GEMPACK manual

Mark Horridge, Michael Jerie, Dean Mustakinov, Florian Schiffmann

17 Dec 2019
ISBN 978-1-921654-90-9

This online version of the GEMPACK documentation is designed for effective searching and navigation within your browser. You can click on on any blue link to jump to the indicated place, and use the Back button to return. Use the middle mouse button to open a link in a new tab. A yellow panel is visible at top right, with links to the Contents page and Index. To find information on a particular topic, go to the Index first. You can also use your browser's Edit..Find command to search through the entire document.

You can use your browser's View menu to adjust the text size. Or, using your keyboard, press CTRL and + or CTRL and - to zoom in or out. If your mouse has a wheel, hold down the CTRL key, and then scroll the wheel to zoom in or out. You may need to wait a second or two to see the effect.

This manual refers to GEMPACK Release 12 and later — but will be useful too for earlier releases.

Each section or subsection has a "topic ID" which appears in green at the end of section headings. GEMPACK programs may emit warning or error messages that refer you to sections of this manual. The references may include section numbers, section titles and topic IDs, but the topic ID is most likely to remain unchanged through successive revisions of the manual.

If you want to print out sections, use the matching PDF file, GPmanual.pdf.

We thank Ken Pearson and Jill Harrison who wrote large parts of previous GEMPACK manuals; much of their work is incorporated here.

A condition of your GEMPACK licence is that acknowledgement of GEMPACK must be made when results that have been obtained with GEMPACK are reported. To cite this manual, use:

Horridge J.M., Jerie M., Mustakinov D. & Schiffmann F. (2018), GEMPACK manual, GEMPACK Software, ISBN 978-1-921654-34-3

Other GEMPACK-related citations are suggested in section 1.7.

1    Introduction [gpd1.1]

Click here for detailed chapter contents

GEMPACK (General Equilibrium Modelling PACKage) is a suite of economic modelling software designed for building and solving applied general equilibrium models. It can handle a wide range of economic behaviour and contains powerful capabilities for solving intertemporal models. GEMPACK calculates accurate solutions of an economic model, starting from an algebraic representation of the model equations. These equations can be written as levels equations, linearized equations or a mixture of these two.

The software includes a range of utility programs for handling the economic data base and the results of simulations, and is fully documented with plenty of examples.

GEMPACK provides

• a simple language in which to describe and document the equations of your economic model;
• a program which converts the equations of your model to a form ready for running simulations;
• options for varying the choice of endogenous, exogenous and shocked variables;
• powerful tools to help you understand or analyze simulation results;
• utility programs to assist in managing model databases. The data can be inspected, modified, or converted to other formats, such as spreadsheets;
• programs to generate reports from simulation results or from inital data.

New features of GEMPACK Release 12 (2018) are listed in section 71.12. New features introduced for versions of GEMPACK Release 11 (2011-16) are listed in sections 71.8 and 71.9.

The remainder of this chapter contains the following sections:

• 1.1 Organization of this manual
• 1.2 Using this manual
• 1.3 Supported Operating Systems
• 1.4 The GEMPACK programs
• 1.5 Models supplied with GEMPACK
• 1.6 Different versions of GEMPACK and associated licences
• 1.7 Citing GEMPACK
• 1.8 Communicating with GEMPACK
• 1.10 Acknowledgments

1.1    Organization of this manual [manualoutline]

Remaining chapters of this manual are organized as follows:

• Chapter 2 is a guide to installing GEMPACK on your Windows PC.
• Chapters 3 to 7 are an Introduction to GEMPACK. New users should first work through these. Chapter 3 tells you how to carry out simulations with models, while chapter 4 tells you how to build or modify models. Chapter 6 describes data files and how to construct them. Chapter 7 describes GEMPACK file types, names and suffixes.
• Chapters 8 to 18 are a comprehensive description of the TABLO language, used to specify GEMPACK models. They also include instructions for running the TABLO program.
• Chapters 19 to 35 tell how to run simulations, using GEMSIM, TABLO-generated programs or SAGEM. They also describe the Command (CMF) Files used to specify details of simulations.
• Chapters 36 to 41 describe other GEMPACK programs. Chapter 36 describes Windows programs such as WinGEM, ViewHAR, Charter, ViewSOL, TABmate, RunGEM, AnalyseGE and RunDynam. Chapters 37 to 41 describe command-line programs, including SLTOHT, ACCUM and DEVIA.
• Chapters 42 to 46 contain a guide to the example models supplied with GEMPACK, and hands-on instructions for using WinGEM, AnalyseGE, RunGEM, and other GEMPACK programs.
• The remaining chapters include more technical material, References, and the Index.

1.2    Using this manual [usingmanual]

This manual is available in two formats which you can view on your PC:

• An HTML document, gpmanual.htm. Each GEMPACK Windows program should provide a link to this file, via the Help menu.
• A PDF document, gpmanual.pdf. You can print out excerpts from this (but not the whole document — it is very long!).

In each case the Contents and Index sections should help you find the information you need.

Each section or subsection has a "topic ID" which appears in green at the end of section headings. GEMPACK programs may emit warning or error messages that refer you to sections of this manual. The references may include section numbers, section titles and topic IDs, but the topic ID is most likely to remain unchanged through successive revisions of the manual.

Previous GEMPACK documentation was contained in a number of separate manuals called GPD-1 to GPD-9. Now most of these documents have been revised¹ and consolidated into this single manual. A list of GEMPACK documents (including the former GPD documents) is given in chapter 80.

1.2.1    For experienced GEMPACK users [gpd1.1.5.2]

If you have worked with an earlier version of GEMPACK, the first thing you will want to see is a list of the new features. The latest new feature list is at the webpage http://www.copsmodels.com/gprelnotes.htm. There is a summary in section 71.12 below. Features introduced for previous GEMPACK Releases are listed in chapter 71.

1.2.2    For new GEMPACK users — getting started [gpd1.1.5.1]

We suggest you read the Introduction to GEMPACK chapters 3 to 7, working through the examples.

We have built these chapters around the sorts of modelling tasks you will want to do. The most important of these tasks are:

• Carrying out simulations with an existing model. Looking at and analysing the results.
• Building a new model or modifying an existing model.
• As part of building a new model or modifying an existing model, you may need to build or modify the data files for the model.

We suggest that you begin with the first of these tasks (simulations). Chapter 3 tells you how to carry out simulations with existing models, and how to look at the results. We suggest that you read this in detail and carry out the simulations described there for yourself. This chapter includes detailed hands-on instructions for using the relevant GEMPACK programs. You will find sufficient detail there to carry out all the steps involved.

The simulations in chapter 3 are based on the Stylized Johansen model, which is a small model. Even if your purpose in using GEMPACK is to work with another model (possibly ORANI-G or GTAP), we strongly recommend that you work through chapter 3 in detail first. After that, you will be in a position to carry out simulations with your chosen model.

At the end of chapter 3 we give suggestions as to what to do next. Roughly speaking, the possibilities are:

• If you mainly want to carry out simulations with another standard model, you will find a list of the models supplied with GEMPACK in section 1.5. You will find detailed hands-on guidance in chapters 42 to 46 about carrying out standard simulations with many of these models.
• When you are ready to build your own model (or modify someone else's), or if you just want to understand how a model is implemented in GEMPACK, you should read chapter 4. Perhaps read it quickly the first time and then go back for a more detailed study.
• If you need to build or modify the data files for a model, you should read chapter 6.
• When you want to know more about the GEMPACK utility programs (say, for report generation or post-simulation processing of results), look at the detailed documentation in Chapters 39 to 41.
• When you want to know more about running the GEMPACK programs, read chapter 48. This chapter gives detailed suggestions for more efficient use of the programs whether you are running them interactively or in batch mode.

We now encourage you to skip the rest of this chapter and to go straight to chapter 3.

1.3    Supported Operating Systems [supportedos]

The complete range of GEMPACK features is available only on PCs running Microsoft Windows. Nevertheless GEMPACK will run (with some limitations) on other operating systems, such as MacOS or Linux (see chapter 69 for more details).

GEMPACK supports both 32-bit and 64-bit versions of Windows 7 to 10. The 64-bit versions are more suitable for large modelling tasks (see section 49.3.1), particularly if you wish to exploit the parallel-processing capability of modern PCs — see chapter 31.

1.4    The GEMPACK programs [gpd9.1.5]

GEMPACK includes a number of separate programs. They fall into two broad groups:

1.4.1    The original command-line programs [gpd9.1.5.1]

The original GEMPACK programs, all written in Fortran, are command-line programs (without a graphical interface). They form the core of GEMPACK and are still directly used by experienced modellers. They are portable between different operating systems. The chief programs are:

1.4.2    The Windows programs [gpd9.1.5.2]

Additional GEMPACK programs only run on Windows PCs. These have a more modern graphical interface, and are written in Pascal [Delphi]. Some of these Windows programs make some use of the core command-line programs listed above: they are really "wrappers" or "shells" which provide a more convenient interface to the original GEMPACK programs. The main Windows programs are:

Another Windows program, RunDynam, is used to organize, perform, and interpret multi-period simulations with recursive-dynamic CGE models. RunDynam is not included in the standard GEMPACK package — it may be purchased separately. See section 36.7 for more about RunDynam.

1.4.3    TABLO-generated programs [gpd1.1.7.1]

There is another class of programs in GEMPACK called TABLO-generated programs. These programs are not supplied as part of the GEMPACK software — you create them yourself.

A TABLO-generated program is a Fortran program, written by the program TABLO, designed to solve a particular model specified in a TABLO input (TAB) file supplied by you. You need a Source-code version of GEMPACK to write TABLO-generated programs — see sections 1.6.1 and 3.5.1 below. These Fortran programs can be compiled and linked to the GEMPACK libraries of subroutines using your Fortran compiler to make an Executable image. The Executable-Image (EXE) can be used to run simulations instead of (and faster than) the program GEMSIM.

1.5    Models supplied with GEMPACK [gpd1.1.8]

A variety of example CGE models are supplied with GEMPACK including:

• small pedagogical models Stylized Johansen and Miniature ORANI
• versions of the ORANI-G model of the Australian economy, including ORANIG-RD, a Recursive Dynamic (forecasting) version.
• TRADMOD, a flexible multi-country trade model documented in Hertel et al. (1992),
• well-known models such as GTAP, the Global Trade Analysis Project's model for analysing trade issues, and DMR, the Dervis, De Melo, Robinson model of Korea,
• TERM, a multi-regional model of a single country
• four intertemporal models TREES, CRTS, 5SECT, and ORANI-INT.
• models using complementarities to simulate quotas, such as MOIQ (based on Miniature ORANI), and several GTAP-based models
• various models illustrating GEMPACK's 'post-simulation' feature

Chapter 60 contains more details. Hands-on examples using some of these models appear in chapters 42 to 46.

1.6    Different versions of GEMPACK and associated licences [gpd1.1.9]

Currently there are four main types of GEMPACK licence:

1. The Source-code version is the most powerful and expensive option. You can produce a model-specific EXE program which solves large models quickly, and can be shared with other people. A Fortran compiler is needed.
2. The Unlimited executable-image version also allows you to create and solve large models, using the general-purpose program GEMSIM. No Fortran compiler is needed — you cannot turn your model into an EXE file.
3. The cheaper Limited executable-image version allows you to create and solve models up to a certain size.
4. The cheapest Introductory licence is needed by persons (with no other GEMPACK licence) who wish to solve a large model using a model-specific EXE program generated by another (source-code) GEMPACK user.

GEMPACK licences are usually site licences, that is, multi-user licences which can be used on any number of computers at the same site within the relevant organisation. However, individual licences are also available for some licence types.

More details about these licence types follow. Alternatively, consult these web-pages:

• Different versions of GEMPACK: http://www.copsmodels.com/gpver.htm
• Feature summary: http://www.copsmodels.com/gemfeat.htm
• Current prices: http://www.copsmodels.com/gpprice.htm
• Licence conditions: http://www.copsmodels.com/gp-lictext.htm

To find out which version of GEMPACK you are running now, see section 2.9.6.

1.6.1    Source-code versions and licences [gpd1.1.9.1]

Source-code licences provide the most flexibility for modellers. The size of the models that can be handled is limited only by the amount of memory on your PC. Large models are usually solved using TABLO-generated programs — which are model specific and can solve large models considerably faster than the general-purpose program GEMSIM. A suitable Fortran compiler is required — see: http://www.copsmodels.com/gpfort.htm which lists both free and commercial compilers.

The Source-code version is the only GEMPACK version that can run "natively" on non-Windows computers: see chapter 69.

1.6.2    Unlimited executable-image version and licence [gpd1.1.9.3]

Like the Source-code version, the Unlimited Executable-image² version allows you to create and solve models of any size — as long as your PC has sufficient memory. No Fortran compiler is needed: all simulations are carried out with the GEMPACK program GEMSIM. With large models (for example, 115 sector ORANI-G or 15-region, 15-commodity GTAP), GEMSIM is noticeably slower than the corresponding TABLO-generated program (which can only be created with a Source-code licence). [Some CPU times are reported in chapter 72.]

If users with an Unlimited Executable-image version find that their simulations are taking an unacceptably long time, they can upgrade to a Source-code version.

1.6.3    Limited executable-image version and licence [gpd1.1.9.2]

With this version, all simulations are carried out with the GEMPACK program GEMSIM. "Limited" means that the size of models that can be solved is limited.

Modellers with the Limited Executable-image version of GEMPACK can carry out the full range of modelling tasks, including building and solving new models, and modifying existing ones. The only restrictions are on the size of the models that can be handled.

The size of models that can be solved is limited to what we call "medium-sized" models. For example, this version is able to solve most single-country models with up to about 40 sectors (for example, it will solve 37-sector ORANI-G), and it will usually solve 12-region, 12-commodity GTAP; but it will not solve 50-sector ORANIG or 15-region, 20-commodity GTAP. The full details of size limits for simulations with the Limited Executable-image version can be seen in chapter 62.

This version of GEMPACK is often supplied at training courses.

If users with a Limited Executable-image version find that their models have become too large, they can upgrade to a Source-code or Unlimited Executable-image version.

1.6.4    Using Exe-image and Source-code GEMPACK together [gpeisc]

A Source-code GEMPACK licence is a site licence covering the whole of some department or section of an organization. The standard installation procedure is not very quick and requires that a suitable Fortran compiler is installed. If there are many GEMPACK users, the cost of multiple Fortran licences could be considerable.

An efficient alternative might be for a small core group of modellers to install the full Source-code GEMPACK (with Fortran compiler) and for an outer group of less frequent (or less advanced) users to use the Unlimited Exe-image version of GEMPACK (without Fortran compiler). No additional licence is needed, because a Source-code licence file will also enable use of the Unlimited Exe-image version.

For example, a university department with a Source-code GEMPACK licence might install full Source-code GEMPACK (with Fortran compiler) on the PCs of several academic staff, while students used the same licence file to run the Unlimited Executable-Image Version. The Executable-Image Version is also well-suited to a Computer Lab environment.

For more details, see http://www.copsmodels.com/gpeisc.htm.

1.6.5    When is a licence needed [gpd1.1.9.7]

A GEMPACK licence is required:

1. to run TABLO or GEMSIM
2. to run a TABLO-generated program using a larger dataset
3. to use some more advanced features of GEMPACK Windows programs

All three tasks above can be accomplished using either an Executable-image or a Source-code licence. But tasks 2 and 3 (but not 1) could also be accomplished using the cheaper Introductory licence described next.

1.6.6    Introductory licence [gpd1.1.9.5]

This type of licence is typically needed by someone who has not installed any full version of GEMPACK, but who has obtained GEMPACK-related material (for example, a TABLO-generated program and/or some data files) from another GEMPACK user.

Some type of GEMPACK licence may be required to run a TABLO-generated program or to use more advanced features of some GEMPACK Windows programs. The Introductory licence is the cheapest way to meet this requirement. It was previously called Large-simulations licence.

TABLO-generated programs distributed to others.

A GEMPACK user with a Source-code licence can create executable images of TABLO-generated programs to solve the models they build or modify. These TABLO-generated programs can be distributed to others (including others who do not have a GEMPACK licence) so that they can carry out simulations with the model. However, if the model is larger than medium sized (as defined in chapter 62), running simulations will require some type of GEMPACK licence. For example, any Source-code or Executable-image licence will do, even older ones. But the Introductory GEMPACK licence, designed for just this purpose, is the cheapest solution.

For example, a modeller who (freely) downloaded the TABLO-generated program GTAP.EXE, would, with no GEMPACK licence be restricted to using data no larger than 12 regions and sectors. If she purchased an Introductory GEMPACK licence, she could solve models of any size (that her PC could manage).

Note also:
(a) An Introductory GEMPACK licence will not allow you to create or modify models.
(b) An Introductory GEMPACK licence will not allow you to run TABLO or GEMSIM.
(c) You do not require a licence file for GEMPACK utility programs such SLTOHT.

Other programs (ViewHAR, AnalyseGE etc).

A trial version of GEMPACK can be freely downloaded from the GEMPACK web site: see http://www.copsmodels.com/gpeidl.htm. After the trial licence expires, you will no longer be able to create or edit new models. However, most Windows programs will continue to work, as they do not require a GEMPACK licence for much of their functionality. However some of the more advanced features of these programs require a moderately recent GEMPACK licence³. For example,

• ViewHAR can be used to modify the data on a Header Array file. However, if the resulting file is large, you will not be able to save it without some kind of GEMPACK licence.
• AnalyseGE normally requires a licence,unless the Solution file being analysed is very small.
• Systematic sensitivity analysis in RunGEM also requires a licence.
• SAGEM also requires some type of GEMPACK licence when used with large models.

The Introductory licence is the least expensive way to satisfy these requirements.

1.7    Citing GEMPACK [citinggempack]

When you report results obtained using GEMPACK, we ask you to acknowledge this by including a reference to GEMPACK in your paper or report. This acknowledgement is a condition of all GEMPACK licences.

For example, please include a sentence or footnote similar to the following:

The results reported here were obtained using the GEMPACK economic modelling software [Horridge et al. (2018)].

and include amongst your references:

Horridge J.M., Jerie M., Mustakinov D. & Schiffmann F. (2018), GEMPACK manual, GEMPACK Software, ISBN 978-1-921654-34-3

An older reference is Harrison and Pearson (1996). For a general account of CGE solution software, focussing on GEMPACK, GAMS and MPSGE, you could cite Horridge et al. (2012). If you use complementarities in your model, consider citing Harrison, Horridge, Pearson and Wittwer (2002). For subtotal results, cite HHP. An extended reference list is here.

1.8    Communicating with GEMPACK [gpd1.1.2]

Latest contact details are at http://www.copsmodels.com/gpcont.htm.

1.8.1    GEMPACK web site [gpd1.1.3]

The GEMPACK Web site is at http://www.copsmodels.com/gempack.htm.

This contains up-to-date information about GEMPACK, including information about different versions, prices, updates, courses and bug fixes. We encourage GEMPACK users to visit this site regularly.

In particular, this site contains a list of Frequently Asked Questions (FAQs) and answers at http://www.copsmodels.com/gp-faq.htm.

This is updated regularly. It is a supplement to the GEMPACK documentation. If you are having problems, you may find the solution there. We welcome suggestions for topics to include there.

There are also alternative GEMPACK web sites at http://www.gempack.com and http://www.gempack.com.au and you can send email to info@gempack.com or support@gempack.com. At present these alternative web sites merely point to the main GEMPACK site. Email to gempack.com is forwarded to the GEMPACK team.

1.8.2    GEMPACK-L mailing list [gpd1.1.4]

GEMPACK-L is a mailing list designed to let GEMPACK users communicate amongst themselves, sharing information, tips, etc. The GEMPACK developers occasionally make announcements on it (new releases, bugs, courses, etc). The list is moderated to prevent spam.

We encourage all GEMPACK users to subscribe to it. Once you have subscribed, you will receive as mail any messages sent to the list. For more details, see http://www.copsmodels.com/gp-l.htm.

1.9    Training Courses [training]

Most GEMPACK users get started by attending a GEMPACK-based training course. A range of courses is offered at different locations around the world by the Centre of Policy Studies — see http://www.copsmodels.com/courses.htm, while others are offered by GTAP (Global Trade Analysis Project) — see http://www.gtap.agecon.purdue.edu/events/.

1.10    Acknowledgments [ackintro]

The improvement of GEMPACK over many years owes a great deal to its users. Some have contributed very useful suggestions, whilst others have patiently supplied us with details needed to reproduce, and ultimately fix, annoying program bugs. We are very grateful to these people, some of whom are listed below.

2    Installing GEMPACK on Windows PCs [gpd6.1]

Click here for detailed chapter contents

This chapter tells you how to install GEMPACK Release 12 on a Windows PC. To install an earlier Release of GEMPACK, please refer to the install documents that accompanied the earlier Release.

Some parts of the install procedure differ between the Executable-Image and the Source-Code versions of GEMPACK — the text below will indicate these differences.

All components of GEMPACK are contained in a single install package, which you might download or receive on a USB drive.

• The install package for Executable-Image GEMPACK might have a name like gpei-12.0-000-install.exe.
• The install package for Source-Code GEMPACK might have a name like gpsc-12.0-000-install.exe.

The package will install

• Windows (GUI) programs such as ViewHAR, ViewSOL, TABmate, AnalyseGE, WinGEM and RunGEM.
• electronic versions of the GEMPACK user documentation (HTM and PDF files).
• many examples of models built using GEMPACK.

The Executable-Image package will also install a number of vital command-line programs such as TABLO.EXE and GEMSIM.EXE. The Source-Code package instead installs Fortran source code files for these programs: during installation these sources are compiled to produce TABLO.EXE and GEMSIM.EXE.

2.1    Preparing to install GEMPACK [gpd6.2]

2.1.1    System requirements [gpd6.2.1]

Requirements for installing GEMPACK are:

• The PC must be running Windows 7 or later.
• The PC must have at least 2GB free hard disk space.
• The PC should have at least 4GB of memory (RAM), and preferably 8GB. Click on Help | About in the main menu of My Computer. This will tell you how much physical memory is available to Windows. The amount of memory you have limits the size of models you can build and run. Small models may use less than 128 MB of RAM, while large models may need 2GB or more. Windows itself uses up much memory. And to do useful things with GEMPACK, you'd very often need to have several GEMPACK Windows programs and perhaps an MSOffice application open at the same time. Each running program uses up RAM.
• If you are installing Source-Code GEMPACK you need first to install and test one of the supported Fortran compilers listed at http://www.copsmodels.com/gpfort.htm. That page links to compiler-specific instructions.
• You will need administrator access to the PC. In a work environment, you may need IT Support to obtain administrator access.
• 64-bit versions of GEMPACK will only work on a 64-bit version of Windows. 32-bit versions of GEMPACK will work on either 32-bit or 64-bit Windows. The install package will detect your Windows version and suggest the right version for you.

2.1.2    Your GEMPACK licence file [gplic]

The installation procedure will ask where to locate your GEMPACK licence file — so you should find it yourself before installing. This small file will have suffix ".GEM" and was probably sent to you as a zipped email attachment, or might be located on the USB drive containing the install package. During installation, a copy of the file, named LICEN.GEM, is placed in the GEMPACK folder (ie, the folder where GEMPACK is installed).

You could also use the LICEN.GEM file in the GEMPACK directory from a previous install of Release 12 GEMPACK (but a Release 11 or earlier licence will not work).

If you cannot find your GEMPACK licence file, you can still install GEMPACK. In this case:

• The Executable-Image installer will create a temporary licence file which last a few months but restricts model size.
• Source-Code GEMPACK cannot be used without a licence.

Then, after installation, you should manually place a copy of your licence file, renamed if necessary to LICEN.GEM, into your GEMPACK folder.

2.1.3    Where to install [instdir]

First decide where to install GEMPACK, bearing the following in mind:

• The ideal plan is to install GEMPACK in a folder C:\GP to which the user has read/write/modify access.
• If you have another or earlier release of GEMPACK already installed in C:\GP, you should probably leave it on your hard disk until you have successfully installed and tested Release 12.0 (in case an unexpected problem occurs). You should rename the directory containing the previous release, so you can install Release 12.0 of GEMPACK in C:\GP. For example, if you currently have Release 11.0 GEMPACK in C:\GP, rename that directory to, say, C:\GP110, and install Release 12.0 into C:\GP. If you use the same GEMPACK directory as before, other GEMPACK-related Windows programs such as RunDynam and RunGTAP will automatically use the latest version of GEMPACK.
• The name of the GEMPACK directory should not contain Chinese or other non-English characters or parentheses ["(",")"]. Also, it's best to avoid extremely long folder names. See section 7.1 for more details.
• It's best if both the GEMPACK programs and the user's model files are stored on a local hard drive (not a network drive).
• You should configure your antivirus program to exclude from real-time scanning both the GEMPACK directory (usually C:\GP) and folders containing the user's model files and simulations. See section 2.1.6 below.

2.1.4    Notes for IT support [itsupport]

You can install GEMPACK as Administrator, and run as Limited or Standard user, as long as permissions are set to allow Limited or Standard users to access needed files. Users of GEMPACK need to be able to read and execute the programs in the GEMPACK directory. In their working directories, Limited Users need full rights to read, write, execute and delete files.

Users of Source-code GEMPACK need to be able to create their own EXE files using their Fortran compiler.

The software requires that users be able to open and use a command prompt (cmd.exe) window, and to run BAT scripts.

Please assist the user by switching off "Hide file extensions of known file types" (From Explorer, Tools...Folder Options...View).

If you are installing GEMPACK on a network please see section 2.9.4.

2.1.5    [Source-code only] Testing the Fortran installation [gpd6.3.3]

Skip this section if you are installing Executable-Image GEMPACK.

Before installing Source-Code GEMPACK you need to test your Fortran installation by compiling and running a small 'Hello World!' program. The webpage http://www.copsmodels.com/gpfort.htm links to compiler-specific instructions for installing and testing your Fortran. It is important that the 'Hello World!' test succeeds before you install GEMPACK.

The test requires that specific Fortran files are present on the PATH. These files are:

• ifortvars.bat for the Intel compiler.
• gfortvars.bat for the GFortran compiler.

The GFortran installer should automatically add the right folders to your PATH. For Intel, you need to edit the PATH variable [the web instructions tell you how].

2.1.6    Configure Anti-virus programs [antivirus]

Some user report that anti-virus programs delete GEMPACK programs or prevent GEMPACK programs from being installed. To avoid such problems you could, before installing GEMPACK:

• Create the GEMPACK folder into which you plan to install (normally C:\GP).
• Configure your anti-virus program to exclude your GEMPACK folder from real-time virus checking. There are some instructions how to do this on the GEMPACK web site at http://www.copsmodels.com/gpconfav.htm.

You may choose also to exclude from virus-checking the folders where GEMPACK-related work will be done — anti-virus programs can slow down simulations (especially RunDynam simulations). See point 3, section 30.

2.2    Installing GEMPACK [gpd6.4]

Exit from all Windows programs before beginning the install procedure.

Use Windows Explorer to locate the GEMPACK install package; double-click to run it.

1. The "User Elevation" dialog will appear; you may need to supply the Administrator password, or simply agree to run the install.
2. Welcome and Copyright warning. To agree to the copyright conditions click Next.
3. Destination Location. Here you choose where GEMPACK will be installed; we refer to this directory as the GEMPACK directory. We recommend that you accept the suggested C:\GP directory. You may choose another existing or new directory by clicking the Browse button. If you do so, when you return to the original screen check carefully that the folder or directory name is what you want. Sometimes the install program adds \GP to the end of the name you have selected. In choosing a folder name, avoid names that contain non-English characters or parentheses. Avoid installing under the Program Files directory: Windows may prevent you changing files there.
4. Changes to your PATH and Environment. The Install program can make changes to your PATH and the Environment variable called GPDIR. We strongly recommend that you agree to these changes. If you do not, you must make these changes yourself later: see section 2.8.
5. Selecting a GEMPACK licence file. If the Installer does not find an existing LICEN.GEM in the GEMPACK directory you may click Browse to select your licence file for installation. If there already is a LICEN.GEM file in your chosen GEMPACK directory, the Installer will not overwrite it, and the Browse button will be disabled. If the existing licence file is an old or wrong licence it is your responsibility to later place the correct Release 12 licence file into your GEMPACK directory, renamed if necessary to LICEN.GEM.
6. [Source-code only] Select Fortran Compiler. Indicate which Fortran compiler you will use. This compiler should be installed and working, as described above.
7. Ready to begin installation. You may review your settings; click Back to make changes or Next to begin the installation. The Install program copies many files to your GEMPACK directory. If installing from a USB drive, leave it inserted until the installation is complete.
8. [Source-code only] Continue with compiling libraries and executable images. After file copying is finished you are prompted to launch BuildGP by clicking Next. When you click on Next, the install program will exit and the BuildGP program will be launched. BuildGP builds the GEMPACK libraries and executable images of the Fortran-based GEMPACK programs. This will take several minutes. If all goes well, you will eventually see a message saying that the libraries and images have been built successfully. In that case, just click OK and go on to section 2.8. If there is a problem, see section 2.2.2.
9. [Source-code only] Continue with compiling libraries and executable images. After file copying is finished you are prompted to launch BuildGP by clicking Next. When you click on Next, the install program will exit and the BuildGP program will be launched. BuildGP builds the GEMPACK libraries and executable images of the Fortran-based GEMPACK programs. This will take several minutes. If all goes well, you will eventually see a message saying that the libraries and images have been built successfully. In that case, just click OK and go on to section 2.8. If there is a problem, see section 2.2.2.
10. For some versions of GEMPACK, you are required to "activate" your licence. A dialog will appear which asks for your name, city and email address. Fill these in; then click the Request Activation Code button. You should soon receive an email containing a 12-letter code, which you enter (or paste) into the activation program. If all is well, your licence will be permanently activated on that PC. For more details see section 2.2.3.

2.2.1    If a warning appears after installing [pcawarning]

Sometimes, just after installing GEMPACK, a warning screen appears, titled "Program Compatibility Assistant" and announcing that "This program might not have installed correctly". You are offered two options (a) "Reinstall using recommended settings", or (b) "This program installed correctly. We believe that the warning is needless and that you should click "This program installed correctly".

2.2.2    [Source-code only] If an error occurs [gpd6.4.1.1]

If an error occurs during the BuildGP process, you will be told the name of the procedure when the error occurred. We suggest that you note this name on paper, then exit from BuildGP. Usually an Error log is shown. This should give you some idea what is happening.

Possible Checks and Actions to try:

• Check that there is plenty of room on your hard disk — if not, you will need to delete some files to create space.
• Check that Fortran is installed and on your path (see section 2.1.5).
• Check that the name of the GEMPACK directory does not contain spaces or Chinese or other non-English characters (See section 7.1).
• Install all over again. Or, you could try re-running just the final, BuildGP, stage. To do this, open a command prompt (DOS box) in your GEMPACK directory and type "BuildGP". Check the GEMPACK directory and compiler choices, then click .Start Build..
• If an error reappears, please notify support@gempack.com. If an Error log has been created, please send it with details of what happened.
• BuildGP checks that there is enough free disk space on the drive you chose for the GEMPACK directory. You can override these checks if you disagree or you can exit from BuildGP, clear some more disk space and then rerun BuildGP. You can read more about BuildGP in section 2.9.1.

2.2.3    Some GEMPACK licences require activation [activation]

Some GEMPACK and RunDynam licences require to be "activated" in order to continue using TABLO or GEMSIM on your PC.

• Limited-size, Introductory and 'Course' licences (handed out at a training course) do not require activation.
• At the final stage of installation, you will be asked if you wish to activate your licence on the PC you are using. This is the best time to do it.
• However, you could choose to run the activation program (GPactivate.exe) later (perhaps after installing the correct licence file). You can go on using a licence which has not been activated for a 'grace period' of 30 days.
• For a given PC and licence, activation is permanent, and does not need to be repeated. But you may need to activate again if you install an upgraded version of GEMPACK, or dramatically change your PC hardware.
• There is a generous limit on the number of times per year each licence can be activated. You can activate an individual licence on several PCs — the limit is greater for site licences. If you exceed the limit you can email GEMPACK sales to ask for the limit to be increased.

More information about licence activation can be found at http://www.copsmodels.com/gpactivation.htm.

2.2.4    GEMPACK licence [gpd6.4.4]

Your GEMPACK licence must be called LICEN.GEM and it must be placed in your GEMPACK directory (that is, the directory in which you installed GEMPACK). The installer may have already done this: if so, skip this section.

If you already have a Release 12 licence on your computer in another directory, please copy the file LICEN.GEM to your current GEMPACK directory.

See section 1.6 for details about GEMPACK licences.

2.2.5    Changes to your PATH and Environment [gpd6.4.4a]

If (against our advice) you did not allow the Install program to make changes to your PATH and the Environment variable called GPDIR, you must now make these changes yourself: see section 2.8.

2.3    Testing the Installation [gpd6.5]

The following test should be performed whether you have the Executable-Image or the Source-Code version of GEMPACK.

The test runs a simulation with the small Stylized Johansen model [SJ].

Create a folder, for example, C:\TEMP, where you can do the test. Copy the following files from the Examples subdirectory of your GEMPACK folder (probably C:\GP\EXAMPLES) to your test folder (eg C:\TEMP):

Open a command prompt (DOS box) by going Start..Run and type in "cmd" and hit OK. This will start a command prompt running. Type in the command

cd /d C:\TEMP

to move to your test folder (assuming that you are testing in C:\TEMP). Then type

dir sj*.*

You should see that the example files listed above are in the test folder.

Step 1: running TABLO

Now type:

tablo -pgs SJ

You should see many messages flash past. If the messages end with

 (Information file is 'C:\temp\SJ.inf'.)
 (The program has completed without error.)
  Total elapsed time is: less than one second.

go straight on to Step 2 below.

If on the other hand you see:

'tablo' is not recognized as an internal or external command,
operable program or batch file.

then the GEMPACK folder is not on your PATH. Please check the steps in section 2.8 and then repeat this part of the testing.

If the messages ended with something like:

  %% Stopping now because of fatal GEMPACK licence problem reported earlier.
  [Search for "%%" in the LOG file to see the earlier message.]
  (ERROR RETURN FROM ROUTINE: TABLO )
  (E-Licence information unavailable.)
  (The program terminated with an error.)

then your GEMPACK folder contains no licence (or the wrong licence). The error message will tell you where TABLO looked for the licence file. Please check that your Release 12 licence file (it must be called LICEN.GEM) is in your GEMPACK directory. If TABLO looks for LICEN.GEM in a directory which is different from the one in which you installed GEMPACK, check the parts of section 2.8 which relate to the Environment variable GPDIR. Repeat this testing once you have remedied any problems.

Step 2: running GEMSIM

Assuming Step 1 (TABLO) worked OK, type

gemsim -cmf sjlb.cmf

You should see many messages flash past, ending with

 (The program has completed without error.)
  Total elapsed time is: less than one second.
 (Output has also been written to log file 'C:\temp\sjlb.log'.)

Congratulations — you have just run a simulation!

If this simulation does not work, start again at section 2.2. If again you have problems, see section 2.5.

If you have the Executable-Image version of GEMPACK, go straight on to section 2.6. If you have the Source-Code version of GEMPACK, you need to do the further tests in the next section.

2.4    [Source-code only] Re-Testing the Installation [gpd6.5s]

This test agains runs a simulation with the small Stylized Johansen model [SJ]. However, while the previous test used GEMSIM (useful whether you have either the Executable-Image or the Source-Code version of GEMPACK), the next test uses a Tablo-generated program (SJ.EXE) to run the simulation. You need the Source-Code version of GEMPACK to create Tablo-generated programs.

Again use the command prompt (DOS box) in your test folder, as described previously.

Step 1: running TABLO

Type in the command

tablo -wfp SJ

You should see messages flash past, ending with

  Successful completion of TABLO.
  The program is
    'sj.for'.
  This program
      o can create the Equations file
      o can carry out multi-step simulations
  ************************************************
 (Information file is 'C:\temp\sj.inf'.)
  (The program has completed without error.)
  Total elapsed time is: less than one second.

Step 2: running LTG

Assuming Step 1 (TABLO) worked OK, type

LTG SJ

You should see your Fortran compiler (Intel or GFortran) at work, ending with the message:

sj.EXE made successfully

If there is a problem, please check that you have installed Fortran correctly as described in section 2.1.5.

Step 3: running a simulation with SJ.EXE

Assuming Step 2 (LTG) worked OK, type

SJ -cmf sjlb.cmf

You should see many messages flash past. If the message ends with:

 (The program has completed without error.)
  Total elapsed time is: less than one second.
 (Output has also been written to log file 'C:\temp\sjlb.log'.)

the test was successful and you should go on to section 2.6.

2.5    If you still have problems [witsend]

If, after re-checking all steps on the install procedure, you still have problems, please run ViewHAR and select

Help | About ViewHAR/Diagnostics | Diagnostics

Save this information in a file, and email it to support@gempack.com. Be sure to describe just when and how the problem appeared.

2.6    More simulations to test GEMPACK and WinGEM [gpd6.5.3]

After you have installed GEMPACK correctly, you will want to start using it! If you are new to GEMPACK, we recommend that you work through the introductory Chapters 3and 4 of the main GEMPACK manual.

To test that GEMPACK and WinGEM are working correctly, we suggest that you carry out the simulations with Stylized Johansen in section 3.4. If you have source-code GEMPACK, run the simulations using a TABLO-generated program as described in section 3.5.2. If you have Executable-Image GEMPACK, use GEMSIM as described in section 3.5.3. In either case, check that the results of the simulation are as expected (see, for example, section 3.7).

If any of these tests does not work, re-check the installation steps described above.

2.7    Working with GEMPACK [gpd6.6]

The following sections contain other information relevant to working with GEMPACK.

2.7.1    New model's directory location [gpd6.6.2]

We suggest that you put each new model you build in a separate directory on the hard disk, outside of the GEMPACK directory (usually C:\GP). Your PATH setting should ensure that the GEMPACK programs are found correctly. Conversely if your PATH and GPDIR are not set correctly, the GEMPACK programs will not run.

When you use WinGEM with any model, make sure that you set WinGEM's working directory to point to the directory containing the files for this model (as spelled out in section 3.4.2).

2.7.2    [Source-code only] GEMSIM or TABLO-generated programs ? [gpd6.6.3]

Both source-code and executable versions of GEMPACK allow you to use the program GEMSIM to run TABLO programs which solve your model or perform other tasks. There are 2 stages:

• TABLO: first converting your TABLO program to GSS/GST files that GEMSIM can use.
• GEMSIM: to run a simulation or perform a calculation.

The source-code version of GEMPACK offers the alternate 3-stage approach of:

• TABLO: first converting your TABLO program to a Fortran program.
• LTG: then converting (compiling) the Fortran program to an EXE file.
• RUN: then running the EXE file to solve your model or perform another task.

Compared to GEMSIM, the TABLO-generated programs [EXE files] run faster with models that have a large database (some CPU times are reported in Chapter 72). However, the additional LTG stage can take some time — this is roughly proportional to the size of the TAB file. If you are going to run the EXE a number of times¹, and if your model has a large database, you will soon recoup the time spent doing LTG. But if you are:

• in the model development stage, where you keep changing the TAB file;
• running a model with a smaller database; or
• running a program that merely manipulates data.

you may well find the simpler GEMSIM approach to be quicker.

2.7.3    Text editor [gpd6.6.4]

When installing and using GEMPACK, you will need to be able to edit text files. This is best done using a text editor (that is, an editor designed especially for handling text files).

We recommend that you use GEMPACK's text editor: TABmate. TABmate has syntax highlighting which is helpful if you are writing or debugging TABLO Input files. TABmate can also be used for other text files, can open several files at the same time and has various Tools which are useful for GEMPACK development.

Other text editors include NotePad (which is supplied with Windows) and VIM and EMACS (which each have their devoted followers). If you use a word processor (such as Microsoft Word) to edit text files, be careful to save the resulting file as a text file.

2.7.4    If you installed in a new directory (not C:\GP) [gpd6.4.3]

If you did NOT install GEMPACK in C:\GP, you may need to help some Windows programs to find and use GEMPACK programs. For example, in RunDynam, click on the Options menu and use menu items such as Which ViewSOL to use to tell the program which versions of ViewSOL, ViewHAR and AnalyseGE to use. In RunGTAP, Click on Tools..Options and then use the various Change buttons to tell RunGTAP where to find Gemsim, ViewHAR, ViewSOL, TABmate, AnalyseGE, Tablo etc.

2.7.5    If a program runs out of memory [gpd6.6.5]

GEMPACK programs may require more memory than is available on your computer. If so you will receive a message saying that the program is stopping because it is unable to allocate sufficient memory. Often this error occurs because you have forgotten to condense your model, or have not condensed it enough (see chapter 14).

Other possible remedies include:

• Free up more memory by closing down any other running applications; then try to rerun the task.
• Buy more memory; however, 32-bit Windows cannot support more than 4 GB, and will only allocate 2 GB to a program.
• If your PC has at least 4GB of memory and you are running 64-bit Windows, check that you are running 64-bit GEMPACK [and for source-code, a 64-bit compiler].

2.7.6    Copying GEMPACK programs to other PCs [gpd6.6.9]

If you have a GEMPACK site licence, you are entitled to install GEMPACK on PCs covered by your site licence, for example, within the same department or institute. An individual GEMPACK licence entitles you to install GEMPACK only on other PCs used by you.

You are allowed to send copies of your TABLO-generated programs to other people. However, such programs may require an Introductory licence if they are used with a larger model. The model size limits are set out in Chapter 62.

Versions of TABLO and GEMSIM programs must match exactly. Hence, do not send GSS/GST files generated by TABLO to others — the GSS/GST files would only work if used with the right GEMSIM version (that matched your TABLO). Rather send only the TAB file — then the recipient can use their matching TABLO and GEMSIM programs.

2.8    Manually setting the PATH and GPDIR [gpd6.4.2]

For GEMPACK to run, you must make sure that the GEMPACK directory (usually C:\GP) is on your PATH, and that the Environment variable GPDIR is set to the GEMPACK directory.

If you did not allow the installer to make changes to your PATH and the Environment variable GPDIR (see section 2.2), you must make the required changes yourself, as described next.

2.8.1    Checking and setting PATH and GPDIR [gpd6.4.2.1]

The usual method to change the PATH and set the Environment variable GPDIR is by editing the System Properties. The important changes are that

• the directory into which you installed GEMPACK (the GEMPACK directory) must be on the system Path.
• the system environment variable GPDIR must be set equal to the GEMPACK directory.

You will need administrator access to make these changes. Follow the steps below to check that the installer made these changes, or to make them yourself:

1. For users of Windows 7 or later, if you are not using an administrator level account you will be prompted for an administrator password during this procedure. Right click on Computer. From the right click menu select Properties then click on the Advanced tab. This brings up the System Properties dialogue window, click on Environment Variables to bring up the Environment Variables dialogue window. Notice that the top half of the window contains user variables, the bottom contains system variables.
2. Edit the system Path variable and add the GEMPACK directory, noting the following. Entries must be separated by a semicolon ";". New entries may be added between any existing entries, however we recommend adding to the beginning of the Path. For example, suppose your GEMPACK directory is C:\GP, then the system path should look like C:\GP;C:\mingw-w64;%SystemRoot%... . If you have a previous GEMPACK directory on the Path delete it and add the new GEMPACK directory to the beginning of the system Path.
3. Add a new (or edit the existing) system environment variable GPDIR to have value set to the GEMPACK directory. This must be the same directory you added to the beginning of the system Path in the previous step.
4. Click on the Ok button to accept these changes to the Environment.

These changes will take effect when you next start a program or open a new command prompt. Test these changes by opening a new command prompt and entering "SET". This should show the altered path and the environment variable GPDIR. If you don't see the changes you expect got to the environment trouble-shooting section and work through the points in the next section 2.8.2.

2.8.2    Trouble-shooting environment variables [envvartrouble]

If you have made changes to the system Path or variable GPDIR which have had the effect you expected, please try the following:

• Reboot your computer and check the values of the system Path and GPDIR again, by opening a new DOS box and entering "SET". Usually this is not necessary, however on rare occasions we have noticed that environment changes are slow to propagate to the rest of the system.
• Check the user Path and GPDIR variables; if a value has been set for both a user and system variable of the same name then, with the exception of the Path variable, the user variable will dominate. This could explain why GPDIR does not have the value you expect. To check the values of user variables for user account Jane for example, you must be logged on as Jane. On Windows 7 and later you can edit the user variables by going to Control Panel, then find User Accounts which depending on the display mode may be in the group User Accounts and Family Safety. From the User Accounts dialogue window click on "Change my environment variables". Check that GPDIR is not set as a user variable, if it is delete it. Bad user enironment variables are more likely to be a problem for upgrade installations rather than new installations.
• Check the values of the system Path and GPDIR variables by working through section 2.8.1.

2.9    Technical Topics [gpd6.7]

In this section we discuss various technical topics. We expect that most GEMPACK users can happily ignore these.

2.9.1    [Source-code only] Running BuildGP [gpd6.7.3]

The program BuildGP is designed to carry out the following tasks:

1. Check your system to see: if Fortran is installed, if there is enough disk space, whether the licence is in the correct place, and if the PATH and GPDIR environment variables are correctly set.
2. Make the GEMPACK libraries by compiling many groups of subroutines.
3. Make the Fortran-based GEMPACK programs (executable images) by compiling the programs and linking to the libraries.

Usually BuildGP does all these automatically when you install GEMPACK. However, there may be situations when you need to run BuildGP yourself. For example, if you discovered a GEMPACK bug, you might be sent a patch file to repair the problem. Detailed instructions would come with the patch file. We provide only brief notes here.

Run the program BUILDGP.EXE in the GEMPACK directory from the command prompt or from My Computer or Windows Explorer.

Check that BuildGP correctly displays your GEMPACK directory and compiler (GFortran or Intel).

Now click on the Start build button.

If you installed GEMPACK successfully with one compiler (say, GFortran), and you later wished to use another compiler (say, Intel), you do not need to install again. It is enough to merely re-run BuildGP. If you want to repeatedly switch between compilers, see the notes at http://www.copsmodels.com/gpmultifort.htm.

2.9.2    File association [gpd6.6.7]

"File association" is the Windows mechanism due to which (for example):

• the ViewHAR icon is displayed beside HAR files in Explorer
• if you double-click a HAR file, it opens in ViewHAR

These happen because files suffixed HAR are "associated" with ViewHAR.exe. Usually the "association" is set up at install time. Only one program can be associated with each file type — so programs might compete to possess more popular suffixes. To stop such contests, Windows may prevent a program from changing an existing association. This may mean, for example, that the GEMPACK installer cannot associate TABmate with TAB files (because Microsoft wants the TAB suffix for Visual Studio). In such cases, you must set up the association manually. You can change the HAR file association as follows:

• in Windows Explorer, right-click on a HAR file and choose Open with....
• check box Always use the selected program should be ticked.
• Use the Browse button to select the latest ViewHAR.exe.

2.9.3    Keep and Temporary directories and GEMPACK Windows programs [gpd6.6.8]

Programs often need to have folders to store user configuration choices, or to write temporary files. Windows provides default folders for these purposes.

GEMPACK Windows programs store user configuration choices in INI files which are (by default) located below a folder chosen by Windows. We call that folder the "Keep" folder. For example, for user "John", the INI file for TABmate might be located at:

C:\Users\John\My Documents\GPKEEP\TABmate\TABmate.ini

Similarly GEMPACK Windows programs by default write temporary files in a subdirectory of the temporary folder provided by Windows².

For very unusual cases, GEMPACK gives a way to avoid problems with the Keep and the default Temporary directories by setting environment variables called GPKEEP and GPTEMP. Set a new environment variable called GPKEEP if you want to change the usual Keep Directory. Set a new environment variable called GPTEMP if you want to change the default temporary directory without changing the environment variable TMP.

In RunGEM, WinGEM, AnalyseGE and RunDynam there are Menu Options within the programs which allow you to set your Temporary directory to a directory of your choosing. The program remembers this Temporary directory setting. When you start the programs for the first time, the default temporary directory is set from the value of the TMP or TEMP environment variable.

If you are having problems with these features of one of the GEMPACK Windows programs, consult the relevant Help file for details and advice.

2.9.4    Installing GEMPACK on a network [gpd6.8]

Some organisations have found it desirable to run the Source-code Version of GEMPACK and the associated Fortran compiler from a network. For example, this can reduce the need for separate copies of the compiler.

Below are some pointers to using GEMPACK and/or Fortran on a network.

• Everyone needs read and execute permissions for the GEMPACK folder but only the administrator may need write access.
• GEMPACK programs do not write to any subdirectories of the Windows directory.
• A range of environment changes, such as to PATH and GPDIR, will need to be made for each user. The Keep and Temporary directories and the TMP or TEMP environment variables need to point to folders that are unique to each user.
• Input, temporary and output files for a simulation should be located on the PC which is running the simulation — the aim is to avoid large amounts of data travelling over the network.

2.9.5    Uninstalling GEMPACK [gpd6.7.6]

To uninstall GEMPACK from your computer, use the standard Add/Remove Programs method. If that fails you could simply:

• Delete the whole GEMPACK directory (and its subdirectories).
• Remove the changes to your PATH and environment (see section 2.8.1).
• Delete any desktop links to GEMPACK programs.

2.9.6    Finding GEMPACK Version and Release Information [identver]

Especially when troubleshooting, it may be useful to check which version of GEMPACK (or of a particular GEMPACK program) you are using. You may wish to know the:

• GEMPACK release no., such as 10.0, 11.2, or 12.0;
• GEMPACK version — either Executable-image or Source-code
• GEMPACK licence type, which should match your GEMPACK version.
• Version no. for an individual program; for example TABmate Version 1.32

Most GEMPACK Windows programs (like ViewHAR and TABmate) give two methods to gather the information above.

First, the GEMPACK Licence command (usually under the Help Menu) shows:

• the name of your licence file, which will be located in your GEMPACK folder.
• the GEMPACK release no. of that licence file. Eg, A GEMPACK 10 licence can be used to run programs from GEMPACK Release 10 or earlier Releases.
• the GEMPACK Version of that licence file — usually Executable-image or Source-code. An Executable-Image licence will not suffice to use Source-Code GEMPACK.
• whether your licence has expired or is size-limited to smaller models.
• your licence details and no. (eg: GFM-0094). The last four digits of this are your customer no.
• if TABLO.EXE is present in your GEMPACK folder, additional lines at the bottom of the Licence Information window show the Version and Release information for that copy of TABLO.EXE — which should match the Version and Release of your licence file.

Figure 2.1 GEMPACK licence command

Second, the About/Diagnostics command (also usually under the Help Menu) shows:

• the name and Version no. of the program; eg, ViewHAR Version 3.13
• the location and filename of the EXE file
• if TABLO.EXE is present in your GEMPACK folder, the GEMPACK Version and Release information for that copy of TABLO.EXE
• a Diagnostics button that displays much more information, which can be saved in a file. If you have a problem, GEMPACK support may ask you to send them this "diagnostics file".

Figure 2.2 About/diagnostics

Program Version and GEMPACK Release Information for Command-line or Fortran-based GEMPACK programs is contained in the first 4 or 5 lines of the log file (if there is one) or in the first 4 or 5 lines of screen output when you run that program from the command-line. Usually this information has scrolled off the top of the Command prompt window before you have time to read it. You may need to scroll back to see it. Or, to capture the output to a file, type:

sltoht <nul: >temp.log

and then examine the top of file temp.log. You might see something like:

 <SLTOHT   Version 5.52  January 2011>
   This program accesses some of the routines in the GEMPACK software release
 <GEMPACK Release 11.1.200   May 2012>

In ViewHAR the History command will show you Program Version and GEMPACK Release Information about the program that created a HAR file — see section 49.1. The same information is echoed to the log whenever a Command-line GEMPACK program reads a HAR file.

3    How to carry out simulations with models [gpd1.2]

Click here for detailed chapter contents

This chapter is where we expect new users of GEMPACK to start learning about simulations. We describe how simulations are carried out, and explain some of the terms used in GEMPACK, such as: implementation, simulation, levels and percentage-change variables.

In section 3.1, there is a very brief overview of the Stylized Johansen model and the simulation that you will carry out. The rest of this chapter consists of detailed instructions for carrying out the simulations and interpreting their results.

We encourage you to work through this whole chapter before starting to work with GEMPACK on your own model. At the end of this chapter we suggest different directions you may wish to go in.

Implementation

A model is implemented in GEMPACK when

• the equations describing its economic behaviour are written down in an algebraic form, following a syntax described later in this document, and
• data describing one solution of the model are assembled, to be used as a starting point for simulations.

For most GEMPACK models, the equations are written down in a linearized form, usually expressed in terms of percentage changes in the variables. But you can choose instead to write down the original (or "levels") equations. In either case you need to write them down in a text file which we call a TABLO Input file or TAB file, since TABLO is the name of the GEMPACK program which processes this information.

The procedure for implementing models is described in detail in chapter 4.

Simulation

Once a model is implemented, the model can be used to carry out simulations. Many simulations are the answer to "What if" questions such as "If the government were to increase tariffs by 10 percent, how much different would the economy be in 5 years time from what it would otherwise have been?". From the original solution supplied as the starting point, a simulation calculates a new solution to the equations of the model. GEMPACK usually reports the results of a simulation as percentage changes from the original solution. Levels results may also be available.

Solving models

within GEMPACK is always done in the context of a simulation. You specify the values of certain of the variables (the exogenous ones) and the software calculates the values of the remaining variables (the endogenous ones).

The new values of the exogenous variables are usually given by specifying the percentage changes (increases or decreases) from their values in the original solution.

Levels and Percentage-Change Variables

When the model is implemented, the equations may be linearized (that is, differentiated). The variables in these linearized equations are usually interpreted as percentage changes in the original variables. The original variables (prices, quantities etc) are referred to as the levels variables and the (usually nonlinear) equations relating these levels variables are called the levels equations.

For example, the levels equation

V = P Q

relates the dollar value V of a commodity to its price P ($ per ton) and its quantity Q (tons). The linearized version of this is

p_V = p_P + p_Q

(as explained later in chapter 4 below) which says that, to first order, the percentage change p_V in the dollar value is equal to the sum of the percentage changes p_P in the price and p_Q in the quantity.

Data

The data for a model often consists of input-output data (giving dollar values) and parameters (including elasticities). The data given are usually sufficient to read off an initial solution to the levels equations. (Usually all basic prices are taken as 1 in the initial solution.)

3.1    An example simulation with stylized Johansen [gpd1.2.1]

In this chapter we show you how to carry out simulations with an existing model (that is, one built by someone else). We use as an example the Stylized Johansen model described in Chapter 3 of Dixon et al (1992), hereafter referred to as DPPW. The model equations are listed in table 4.1 in section 4.1.

The Stylized Johansen model is chosen because it is simple. Once you know how to carry out simulations with it in GEMPACK, you will find it easy to carry out simulations with other, more complicated models (including ones you build yourself).

3.1.1    Introduction to the stylized Johansen model [gpd1.2.1.1]

The Stylized Johansen model is a very simple model of a single country. It recognises two sectors "s1" and "s2" each producing a single commodity, one final demander (households) and two primary factors (labor and capital). There are no exports or imports. Output of each sector is a Cobb-Douglas aggregate of labor, capital, and intermediate inputs. Household demands are also Cobb-Douglas.

The initial input-output data base is shown below in Table 3.1. For example, households consume 4 (million) dollars' worth of commodity 2 and industry 2 uses 3 (million) dollars' worth of labor. Note that the first two row totals (value of sales each of good) equal the first two column totals (costs of each sector).

In the GEMPACK implementation, the levels variables are as in Table 3.2 below.

Note that most of the variables have one or more arguments (indicating associated sectors and/or factors). We refer to such variables as vector or matrix variables. For example, PC(i) is a vector variable with 2 components, one for each sector, namely PC("s1") and PC("s2"). XF(f,j) is a matrix variable with the following 4 components:

Variables which have no arguments ('Y' is the only one here) are referred to as scalar or macro variables.

Corresponding to each levels variables, there is an associated percentage change variable. TABLO adds the prefix "p_" to the name of the levels variable to indicate a percentage change. For example, p_XF is the percentage change in the levels variable XF. In DPPW, lower case letters are used to denote percentage-change variables.

More details about the model are given in chapter 4. A full TABLO Input file can be found in section 4.3.3.

3.1.2    The simulation [gpd1.2.1.2]

In the example simulation with the Stylized Johansen model used throughout most of this chapter, we choose a closure in which supplies of the two factors, labor and capital, are the exogenous variables. This means we will specify the percentage changes in the variable XFAC, namely p_XFAC, and solve the model to find the percentage changes in all the other variables. You will also be able to see the levels results (for example, the post-simulation value of household income).

For this simulation, we increase the supply of labor by 10 per cent and hold the supply of capital fixed.

The starting points for any simulation with the Stylized Johansen model are

• the TABLO Input file, SJ.TAB, and
• the data file, SJ.HAR.

3.2    Preparing a directory for model SJ [gpd1.2.4.2]

We assume that you have already installed GEMPACK correctly as described in chapter 2.

To keep all example files for the Stylized Johansen model together in one area, you should first create a separate directory (folder) for these files and copy the relevant files into this directory.

Use Windows Explorer (or My Computer) to create a new folder or subdirectory called \sj and copy all the sj*.* files from the directory containing the GEMPACK model examples (usually C:\GP\EXAMPLES) to this directory \sj.

3.3    Using GEMPACK: WinGEM or command prompt? [gpd1.2.3]

There are two ways of operating GEMPACK:

• through the WinGEM interface. Initially this method is easier, since WinGEM helps you with the names of the programs and files used by GEMPACK.
• at the Command line, ie, working in a DOS box within Windows. We will refer to this method as Command Prompt. Many advanced users find this approach quicker and more flexible. They use DOS commands but also launch Windows programs such as TABmate, ViewHAR and ViewSOL from the command line.

We describe both methods, but suggest that you first work through this chapter using the WinGEM method — then, if you wish, repeat the exercise using the Command prompt instructions which are shown like this:

Command-prompt users should read (but not do) the WinGEM instructions, then should execute the corresponding DOS commands, which will be shown just after the WinGEM instructions.

3.4    Stylized Johansen example simulation [gpd1.2.4]

3.4.1    Starting WinGEM [gpd1.2.4.1]

In Windows, double-click on the WinGEM icon to start GEMPACK for Windows. The main WinGEM menu should appear, as a ribbon menu across the top of the screen:

WinGEM  -  GEMPACK for Windows

File   Simulation   HA Files   Other tasks   Programs   Options   Window   Help

3.4.2    Setting the working directory [gpd1.2.4.3]

WinGEM uses the idea of a working directory to simplify choosing files and running programs. This working directory is where all the files for the model you are using are stored.

For the Stylized Johansen model examples here, the working directory needs to be the directory \SJ you have just created. To set this, first click on File in the main WinGEM menu. This will produce a drop-down menu. In the drop-down menu, click on the menu item Change both default directories.

The notation we use for this sequence of clicks (first File then Change both default directories) is

File | Change both default directories.

In the file selection box that appears, choose drive C: (or the drive containing your directory \SJ if it is on a different drive). Then double-click on C:\ (this will be at the top of the list of directories shown) and then double-click on the subdirectory SJ. [Make sure that the directory name shown in blue above the selection box changes to C:\SJ (or D:\SJ etc if your \SJ directory is on another drive).] Click on the Ok button.

Command-prompt users should open a DOS box in the C:\sj directory.¹

3.4.3    Looking at the data directly using ViewHAR [gpd1.2.4.4]

The input-output data used in the Stylized Johansen model are contained in the data file SJ.HAR. This is a special GEMPACK binary file - called a Header Array file - so you cannot just look at it in a text editor. Instead you will look at SJ.HAR using the ViewHAR program. Select from the main WinGEM menu: HA Files | View VIEWHAR

The ViewHAR window will appear. Click on File | Open and select the file SJ.HAR. This will open the file SJ.HAR and show its contents on the Contents screen.

Command-prompt users can open SJ.HAR by typing "viewhar SJ.HAR" into the DOS box.

Each row of the ViewHAR Contents screen corresponds to a different array of data on the file. Look at the "Name" column to see what data are in these arrays.

The first array is the "Intermediate inputs of commodities to industries - dollar values". The Header CINP is just a label for this array (headers can have up to 4 characters). The array is of Type RE — an array of real numbers with set and element labelling (see chapter 5.0.3).

Double-click on CINP to see the numbers in this array.

Compare these numbers with the input-output data for Stylized Johansen shown in Table 3.1. The actual data in the file at this header is just the 2x2 matrix. ViewHAR calculates and shows the row and column totals.

To return to the Contents Screen, click on Contents in the ViewHAR menu, or click twice on any number.

Look at the other Header Arrays called FINP and HCON to see where their numbers fit in the input-output data base.

Close ViewHAR by selecting File | Exit.

3.5    Implementing and running model SJ [gpd1.impsj]

There are three steps involved in carrying out a simulation using GEMPACK.

Step 1 - Implement the model (using TABLO)

Step 2 - Solve the equations of the model (ie, run a simulation)

Step 3 - View the results

3.5.1    TABLO-generated program or GEMSIM? [gpd1.2.4.5]

The details of steps 1 and 2 vary according to whether you have the Executable-image or the Source-code version of GEMPACK. With either version, you can use GEMSIM to run simulations. The Source-code version also allows you to create a model-specific, TABLO-generated, EXE file, which you can run to solve the model. Especially for larger models, the TABLO-generated program will usually solve quicker.

The Source-code method is described next. If you have the Executable-image version of GEMPACK, you will need to skip onto the GEMSIM instructions in section 3.5.3.

3.5.2    Source-code method: using a TABLO-generated program [gpd1.2.4.6]

In the next examples we are assuming that you have the Source-code version of GEMPACK and have a Fortran compiler on your DOS PATH.

From the WinGEM menu at the top of the screen choose Simulation. In the drop-down menu the choices are

TABLO Implement
Compile & Link
TABmate Implement
-------------------
Run TG Program
GEMSIM Solve
SAGEM Johansen Solve
---------------------
View Solution (ViewSOL)
AnalyseGE

The items from this menu you will be using in this simulation are

TABLO Implement
Compile & Link
Run TG Program
View Solution (ViewSOL).

In the TABLO-generated program method, the GEMPACK program TABLO is used to convert the algebraic equations of the economic model into a Fortran program (.FOR file) specific to your model. This Fortran program (which is referred to as the TABLO-generated program or TG Program in the above menu) is compiled and linked to a library of GEMPACK subroutines. The EXE file of the TABLO-generated program produced by the compiler is used to run simulations (instead of using the program GEMSIM). This method provides faster execution times for large models than the GEMSIM alternative but means you must have an appropriate Fortran compiler.

WinGEM will guide you through the various steps and indicate what to do next.

Step 1 - Implementing the model SJ using TABLO

Step 1(a) - Run TABLO to create the TABLO-generated program

The TABLO Input file is called SJ.TAB. It contains the theory of the Stylized Johansen model. Choose

Simulation | TABLO Implement

A window for TABLO will appear. Click on the Select button to select the name of the TABLO Input file SJ.TAB². This is all TABLO needs to implement this model. ³

At top right of the TABLO window are choice buttons for FORTRAN and GEMSIM.

Check that the first, FORTRAN, option is selected (we want you to create the TABLO-generated Fortran program).

Click on the Run button. The program runs TABLO in a DOS box and when complete, returns you to the TABLO window with the names of files it has created: the Information file SJ.INF and the Log file. Look at both of these files by clicking the View buttons beside them.

The Information file SJ.INF gives information about the TABLO Input file such as whether there are any syntax or semantic errors during checking by TABLO. Search the file for %% to see if there are any errors. Search the file for "syntax error" to see how many syntax errors and semantic problems there are (hopefully none). Go to the end of the file to see what actions can be carried out by the TABLO-generated program produced in this TABLO run.

Command-prompt users can perform Step 1(a) by typing "tablo -wfp sj -log sj.log". To see LOG or INF files, type "tabmate SJ.INF" or "tabmate SJ.LOG".

Step 1(b) - Compile and Link the TABLO-generated Program

When you have looked at these two files, click on the Go to Compile and Link button at the bottom of the TABLO window to run the Fortran compiler. (Alternatively you can start this window by choosing Simulation | Compile and Link... from WinGEM's main menu.)

In the Compile and Link window, the file SJ.FOR is already selected as the TG Program Name. Click on the button Compile and Link and wait a little while the compiler converts the Fortran file SJ.FOR into the SJ.EXE program that you can run.

When finished, click on the button Go to 'Run TG Program' to proceed to the next step in running a simulation.

Command-prompt users can perform Step 1(b) by typing "LTG sj". Type "dir sj.exe" to check that file SJ.EXE has been produced.

Step 2 - Solve the equations of the model using TABLO-generated program

The Go to 'Run TG Program' button takes you to the window for running the TABLO-generated program SJ.EXE. (Alternatively you can start this window by choosing Simulation | Run TG Program... from WinGEM's main menu.)

First Select the Command file called SJLB.CMF. Since Command files are text files, look at this Command file in the text editor by clicking the Edit button.

How is the closure specified? What shock is applied?

What data file is used by this model? How many steps are used in the multi-step solution?

Details about using a GEMPACK Command file to specify a simulation are given in section 3.8 below. For the present, we suggest that you take this on trust and continue with the simulation.

Select File | Exit to close the editor and return to the "Run TG Program" window.

Click on Run to run SJ.EXE with the Command file SJLB.CMF.

When SJ.EXE finishes running, an accuracy summary window will pop up. This gives a graphical view as to how accurately the equations have been solved⁴. You can ignore this for the present (it is discussed in section 3.12.3) so click OK.

If SJ.EXE produces the Solution file, click on Go to ViewSOL⁵.

If there is an error, view the Log file.

Command-prompt users can examine the Command file SJLB.CMF by typing "TABmate SJLB.CMF". Run the simulation by typing "sj -cmf SJLB.CMF". Then, to see the results, type "ViewSOL SJLB.SL4".

Now please skip the next (GEMSIM) section and go on to the ViewSOL instructions in 3.5.4.

3.5.3    Executable-image method: using GEMSIM [gpd1.2.4.7]

In the WinGEM menu at the top of the screen choose Simulation. In the drop-down menu the choices are⁶.

TABLO Implement
Compile & Link
TABmate Implement
-------------------
Run TG Program
GEMSIM Solve
SAGEM Johansen Solve
---------------------
View Solution (ViewSOL)
AnalyseGE

The items from this menu you will be using in this simulation are

TABLO Implement
GEMSIM Solve
View Solution (ViewSOL).

WinGEM will guide you through the various steps and indicate what to do next.

Step 1 - Implementing the model SJ using TABLO (for GEMSIM output)

The TABLO Input file is called SJ.TAB. It contains the theory of the Stylized Johansen model. Choose Simulation | TABLO Implement...

A window for TABLO will appear. Click on the Select button to select the name of the TABLO Input file SJ.TAB⁷. This is all TABLO needs to implement this model ⁸.

At top right of the TABLO window are choice buttons for FORTRAN and GEMSIM.

Check that the second, GEMSIM, option is selected (we want you to create the GEMSIM Auxiliary files).

By "implement" we mean convert the TABLO Input file into binary computer files which are used by the simulation program GEMSIM in the next step. These files are referred to as Auxiliary files (or sometimes as the GEMSIM Statement and Table files) and in this case, are called SJ.GSS and SJ.GST.

Click on the Run button. The program TABLO runs in a DOS box and when complete returns you to the TABLO window with the names of files it has created: the Information file SJ.INF and the Log file. Look at both of these files by clicking the View buttons beside them. To close the file, click on the X in the top right-hand corner of the view, or click File..Exit using the File menu.

The Information file SJ.INF gives information about the TABLO Input file such as whether there are any syntax or semantic errors found during checking by TABLO. Search the file for %% to see if there are any errors. Search the file for "syntax error" to see how many syntax errors and semantic problems there are (hopefully none). Go to the end of the file to see what actions GEMSIM can carry out with the Auxiliary files produced in this TABLO run.

When you have looked at these two files, click on the Go to GEMSIM button at the bottom of the TABLO window to go on to the next step in running a simulation:

Command-prompt users can perform Step 1 by typing "tablo -pgs sj -log sj.log". To see LOG or INF files, type "tabmate SJ.INF" or "tabmate SJ.LOG".

Step 2 - Solve the equations of the model using GEMSIM

The Go To GEMSIM button takes you to the GEMSIM window. (Alternatively you can start this window by choosing Simulation | GEMSIM Solve from WinGEM's main menu.)

First Select the Command file called SJLB.CMF. Since Command files are text files, look at this Command file in the text editor by clicking the Edit button.

How is the closure specified? What shock is applied?

What data file is used by this model? How many steps are used in the multi-step solution?

Details about using a GEMPACK Command file to specify a simulation are given in section 3.8 below. For the present, we suggest that you take this on trust and continue with the simulation.

Select File | Exit to close the editor and return to the GEMSIM window.

Click on Run to run GEMSIM with the Command file SJLB.CMF.

When GEMSIM finishes running, an accuracy summary window will pop up. This gives a graphical view as to how accurately the equations have been solved⁹. You can ignore this for the present (it is discussed in section 3.12.3) so click OK.

If GEMSIM produces the Solution file, click on Go to ViewSOL¹⁰.

If there is an error, view the Log file.

Command-prompt users can examine the Command file SJLB.CMF by typing "TABmate SJLB.CMF". Run the simulation by typing "sj -cmf SJLB.CMF". Then, to see the results, type "ViewSOL SJLB.SL4".

3.5.4    Step 3 - View the Solution using ViewSOL [gpd1.2.viewsol]

You cannot view the Solution file SJLB.SL4 in a text editor because it is a binary file, not a text file. Instead we use ViewSOL to examine the Solution file.

In WinGEM, the Go to ViewSOL button starts the program ViewSOL running and opens the Solution file SJLB.SL4 . [Alternatively you can start this window by choosing Simulation | View Solution (ViewSOL) from WinGEM's main menu.]

Command-prompt users should type "ViewSOL SJLB.SL4".

You will see the Contents page listing many of the variables of the model. ViewSOL has 3 slightly different formats for this Contents list. Select Format... from ViewSOL's main menu and there click on Arrange vectors by name (in the panel headed Vector options); then click Ok which will put you back to the Contents list.

To see the results of one of these variables listed by name, just double-click on the corresponding row in the Contents list. First double-click on the p_XCOM row to see the results for this variable (demand for the two commodities). Select 3 decimal places (see the third drop-down list box along the top row of the current ViewSOL window - the only one with a single figure in it). Then you should see something like the following:

Across the s1 row you see the percentage change result (5.885%), the pre-simulation levels value (8.000), the post-simulation levels value (8.471) and the change (0.471); these are the results for the total supply of commodity s1.

Then click on Contents to return to the Contents list.

To see the p_XFAC results, double-click on this row. You will see

This time all the numbers are in red which is used to remind you that, for this simulation, both components of this variable p_XFAC are exogenous. You should easily be able to understand all of these results.

Then click on Contents to return to the Contents list (or click twice on any number).

To see the p_XC(i,j) results [intermediate inputs of commodity i into industry j], double-click on this row. Now you see

and, in the second drop-down box you should see "1 sjlb". This indicates that you are just seeing the linearized simulation results (the percentage changes in the four components of this variable). You can't see the pre- and post-simulation levels results at the same time since this variable p_XC is a matrix variable. To see the pre-simulation levels results, click on the second drop-down list box (the one showing "1 sjlb") and select the second alternative ("2 Pre sjlb"). Then you will see the pre-simulation levels results. You might also like to look at the post-simulation levels results and the changes.

Then click on Contents to return to the Contents list.

When you have finished looking at the results, exit from ViewSOL.

3.6    The steps in carrying out a simulation [gpd1.2.5]

This section recapitulates the steps (that you just followed) to implement a model and carry out a simulation.

In all cases, after the TABLO Input file for a model has been written, there are 3 steps on the computer to carry out a first simulation with the model. These steps are:

Step 1 - Implement the model

Step 2 - Simulation (Solve the equations of the model)

Step 3 - View the results with ViewSOL or perhaps AnalyseGE.

Step 1 always involves running the program TABLO.

The details of Steps 1 and 2 are a little different depending on whether you have a Source-code or Executable-image version of GEMPACK, as we explain below.

Next we describe the Source-code procedure. The Executable-image version of steps 1 and 2 is described in section 3.6.2.

3.6.1    Steps 1 and 2 using a TABLO-generated program (source-code GEMPACK) [gpd1.2.5.1]

The steps are illustrated in Figure 3.1 below.

Figure 3.1 The steps in carrying out a simulation using a TABLO-generated program

Step 1. Computer Implementation of the Model

Step 1(a) - Run TABLO to create TABLO-generated program

Process the TABLO Input file for the model by running the program TABLO. Select the option WFP which tells TABLO to write a Fortran program (referred to as the TABLO-generated program of the model) which captures the theory of the model.

Step 1(b) - Compile and Link the TABLO-generated program [LTG]

Compile and link the TABLO-generated program of the model, produced in Step 1(a). This will produce an EXE file of the TABLO-generated program¹¹.

Step 2. Simulation (Solve the equations of the model)

Run the EXE file of the TABLO-generated program, as produced in Step 1(b). Take inputs from a Command file which tells the program which base data files are to be read and describes the closure (that is, which variables are exogenous and which are endogenous) and the shocks. This program then computes the solution to your simulation and writes the results to a Solution file

Step 3. Printing or Viewing the Results of the Simulation

The last step is to view simulation results with ViewSOL or AnalyseGE¹². An alternative is to use the program SLTOHT to process results (for example, to produce tables for reports), as introduced in section 3.10 below.

3.6.2    Steps 1 and 2 using GEMSIM [gpd1.2.5.2]

The steps using GEMSIM are illustrated in Figure 3.2.

Figure 3.2 The steps in carrying out a simulation using GEMSIM

Step 1. Computer Implementation of the Model

Process the TABLO Input file for the model by running the GEMPACK program TABLO. Select the option PGS which asks TABLO to produce the GEMSIM Auxiliary files for the GEMPACK program GEMSIM (see Step 2). These files capture the theory of the model, as written in the TABLO Input file.

Selecting option PGS rather than the option WFP as in section 3.6.1 above is what initiates the GEMSIM route rather than the TABLO-generated program route.

Step 2. Simulation (Solve the equations of the model)

Run the GEMPACK program GEMSIM¹³ and tell it to use the GEMSIM Auxiliary (GSS/GST) files produced in Step 1. Take inputs from a Command file which tells the program which base data files are to be read and describes the closure (that is, which variables are exogenous and which are endogenous) and the shocks. GEMSIM then computes the solution to your simulation and writes the results to a Solution file.

Step 3. Printing or Viewing the Results of the Simulation

The last step is to view simulation results with ViewSOL or AnalyseGE¹⁴. An alternative is to use the program SLTOHT to process results (for example, to produce tables for reports), as introduced in section 3.10 below.

Comparing the steps in the two cases

Note that Step 1 above is very similar to Step 1(a) in the TABLO-generated program case (see section 3.6.1 above). The LTG step 1(b) in section 3.6.1 has no analogue in the GEMSIM case since GEMSIM is a general-purpose program which can be used to solve any model. Step 2 is different only in that GEMSIM is run rather than the TABLO-generated program. Step 3 is identical in the two cases.

3.6.3    Other Simulations [gpd1.2.5.othsims]

Once you have carried out one simulation with a model, you will probably want to carry out others, for example, to change the closure and/or shocks, or even to run from different base data. In such cases, you do not have to repeat Steps 1(a) and 1(b). All you have to do is carry out Steps 2 and 3. A hands-on example is given in section 3.11 below. (Of course Step 1 must be repeated if you change the TABLO Input file in any way.)

3.7    Interpreting the results [gpd1.2.7]

You have already looked at the results via ViewSOL (see Step 3 in section 3.5.4). From the ViewSOL Contents page you clicked on and examined variables such as Macros, p_XH, p_PC, p_XF, p_DVHOUS. We have copied some of the results from ViewSOL to a spreadsheet (via the Copy menu item in ViewSOL). These are shown in Table 3.3 below.

We think that you will find the tables fairly easy to interpret.

The results show what happens if the supply of labor is increased by 10 per cent and the supply of capital is held fixed. For example,

• Look at the simulation result for 'p_Y', the percentage change in the levels variable 'Y'. The dollar value of total nominal household expenditure will increase by 5.8853 per cent from its pre-simulation value of 6.0000 to its post-simulation value of 6.3531.
• Look at the results for p_XH. The result for commodity 2, p_XH ("s2"), shows that households will consume 6.8993 per cent more of commodity 2 than they did previously.
• Look at the results for p_PC. The price of commodity 2 will fall by 0.9486 per cent.
• The simulation results for p_DVHOUS show that the dollar value of household consumption of commodity 2 will rise by 5.8853 per cent from its pre-simulation value of 4.0000 to its post-simulation value of 4.2354.

Recall that, within GEMPACK, all simulations are set up and solved as perturbations from an initial solution, and results are usually reported as changes or percentage changes from this original solution. In this case the original solution values are as shown in Table 3.2 above, which shows million dollar values of activity. Suitable levels values for quantities can be obtained by assuming that, initially, all prices are 1. (This just sets the units in which quantities are measured.) Then, for example, since households consume 4 million dollars' worth of commodity 2, this means that they consume 4 million units of that commodity.

Hence the three simulation results mentioned above mean that, once labor is increased by 10 per cent and capital is held fixed:

1. Total nominal household expenditure Y has increased to approximately 6.353 million dollars (5.8853 per cent more than the original value of 6 million dollars).

(The other three values given with p_Y in Table 3.3 are

2. Household consumption (XH) of commodity 2 has increased to 4.2760 million units (6.8993 per cent more than the original 4 million units).

3. The commodity price (PC) of commodity 2 has fallen from one dollar per unit to approximately 99.051 cents per unit (a fall of 0.9486 per cent).

4. The dollar value of household consumption (DVHOUS) of the commodity produced by sector "s2" has risen from 4 million dollars to approximately 4.2354 million dollars (an increase of 5.8853 per cent).

The updated values in (2), (3) and (4) above should be related since dollar value should equal price times quantity. The levels equation for commodity 2 ("s2") is

DVHOUS("s2") = PC("s2) x XH("s2")

Note that this equation is true for the post-simulation values, since, from (2) and (3) above, the post-simulation price times the post-simulation quantity is

which is equal to the post-simulation dollar value in (4). This confirms that the solution shown in ViewSOL satisfies the levels equation connecting price, quantity and dollar value of household consumption of this commodity. You might like to check some of the other levels equations in this way.

3.8    Specifying a simulation [gpd1.2.8]

In order to specify the details for carrying out a simulation, you must

• say which model to use,
• say which base data to begin from (that is, the pre-simulation solution),
• say which closure (that is, which variables are endogenous and which are exogenous), and
• say which variables to shock, and by how much, and
• specify the names of the various output files.

Figure 3.3 The information required to specify a simulation

Within GEMPACK, the normal way of specifying this information to the software is via a Command (CMF) file. Indeed, when you carried out the example simulation above, this is exactly what happened in Step 2 above since there you ran either the TABLO-generated program or GEMSIM and took inputs from the Command file SJLB.CMF.

The instructions in this Command file must be prepared in advance in a text editor.

The next section explains the statements in this GEMPACK Command file SJLB.CMF.

3.8.1    Specifying a simulation via a GEMPACK command file [gpd1.2.8.1]

In Step 2 of the example simulation, the program took all the information required to specify the simulation from the GEMPACK Command file SJLB.CMF. The file SJLB.CMF is shown in full in Figure 3.4 below.

Figure 3.4 The GEMPACK command file SJLB.CMF

! The following GEMPACK Command file (usually called SJLB.CMF)  
!  carries out a multi-step simulation 
!  for the Stylized Johansen model.  
!  Auxiliary files (usually tells which TAB file)
auxiliary files = sj ;  
! Data files
file iodata = SJ.HAR ;
updated file iodata = <cmf>.upd ;  
! Closure
exogenous p_xfac ;
rest endogenous ; 
! Solution method information
method = euler ;
steps = 1 2 4 ;
! Simulation part
! Name of Solution file is inferred from name of Command file
! (See section 20.5.)
shock  p_xfac("labor") = 10 ;  
verbal description =
Stylized Johansen model. Standard data and closure.
10 per cent increase in amount of labor. (Capital remains unchanged.) ;
! Options.extrapolation accuracy file = yes ;
log file = yes ;
! End of Command file   

The statements in SJLB.CMF are discussed briefly below.

The statement

auxiliary files = sj ;

tells GEMSIM or the TABLO-generated program to use the Auxiliary files produced in Step 1. (This effectively tells which TABLO Input file (or model) to work with, since these files are just a processed version of the TABLO Input file SJ.TAB for the Stylized Johansen model.) [If you are using the TABLO-generated program SJ.EXE, the Auxiliary files are SJ.AXS and SJ.AXT produced when you ran TABLO in Step 1. If you are using GEMSIM, the Auxiliary files are SJ.GSS and SJ.GST produced when you ran TABLO in Step 1.]. You can find more details about these Auxiliary files in 21.

The statement

file iodata = SJ.HAR ;

tells SJ.EXE or GEMSIM to read base data from the file SJ.HAR (which contains the data in Table 3.1 above).

The line

! Data files

above this line is a comment since it begins with an exclamation mark !. While such comments are ignored by the software, they are very important in organising and documenting the Command file and in making it an intelligible record of the simulation. [You can see several other comment lines in the file.]

The statements:

exogenous p_xfac ;

rest endogenous ;

give the closure (that is, which variables to take as exogenous and which to take as endogenous), while the statement

shock p_xfac("labor") = 10 ;

gives the shock needed to increase the supply of labor by 10 per cent.

When the TABLO-generated program SJ or GEMSIM carries out a simulation, as well as being able to report the changes in the endogenous variables, the program produces an updated version of the original data file(s). The data in these updated data files represent post-simulation values (that is, the ones that would hold after the shocks have worked their way through the economy). For Stylized Johansen, this contains post-simulation dollar values of the entries in Table 3.1 above. The statement

updated file iodata = <cmf>.upd ;

names the file to contain this updated data [examined in section 3.9 below]. The <cmf> in this line indicates that this part of the name comes from the name of the Command file. Since the Command file is usually called SJLB.CMF, the program replaces <cmf> by SJLB (the name of the Command file ignoring its suffix .CMF) so that the updated iodata file will be called SJLB.UPD. The <cmf> syntax is explained further in section 20.5.

The most important output from a simulation is the Solution file which contains the results for the percentage changes in prices and quantities. Here we have omitted the name of the Solution file so the name of this file is taken from the name of the Command file. Because the Command file is called SJLB.CMF, the Solution file will be called SJLB.SL4 (the same basic name SJLB followed by .SL4 which is the standard GEMPACK suffix for Solution files). Another alternative is to add a statement of the form

solution file = ... ;            ! Not included in this SJLB.CMF

in the Command file. Such a statement is allowed, but it is customary to omit it so that the name of the Solution file is inferred from the name of the Command file.

You are required to give a verbal description of the simulation. This description, which can be several lines of text, goes on the Solution file and is visible from ViewSOL and other programs. You can use this to remind yourself (and others) about salient features of the simulation. The statement

verbal description = .Stylized Johansen model. 
 Standard data and closure.
 10 per cent increase in amount of labor (Capital remains unchanged.)
 1,2,4-step solutions plus extrapolation. ;

in SJLB.CMF give 4 lines of text for the verbal description in this case. The semicolon ';' indicates the end of this description — indeed all statements in GEMPACK Command files must end with a semicolon ';'.

With GEMPACK, you can choose one of 4 related solution methods for each simulation. These are introduced in section 3.12.3 below. The statements

method = euler ;

steps = 1 2 4 ;

in the Command file tell the program to use Euler's method based on 3 separate solutions using 1, 2 and 4 steps respectively. (See section 3.12.3 below for an explanation about step numbers.)

The accuracy of the solution depends on the solution method and the numbers of steps. SJ.EXE or GEMSIM can be asked to provide information about the accuracy on an Extrapolation Accuracy file. The statement

extrapolation accuracy file = yes ;

asks the program to produce such a file. The information on this file is described in section 3.12.3 below. (The name of this file is the same as that of the Solution file except that it has a different suffix, namely '.XAC', which makes the full name SJLB.XAC.)

The statement

log file = yes ;

asks the software to produce a LOG file showing all the screen activity as the program runs. This LOG file is called SJLB.LOG - it takes its name from the name SJLB.CMF of the Command file but changes the suffix from .CMF to .LOG. This LOG file is a useful record of the simulation.

Further details of Command files and running simulations are given in chapters 19 and following, which describe running simulations with GEMSIM, TABLO-generated Programs and SAGEM. A summary of the statements that can be used in a GEMPACK Command file for running TABLO-generated programs or GEMSIM is given in chapter 35.

In particular, we know that new users of GEMPACK find the auxiliary files (the statement above is "auxiliary files = sj ;") and the file statements (the statements above are "file iodata = SJ.HAR; " and "updated file iodata = <cmf>.upd ;") confusing initially. More details about these can be found in chapters 21 and 22.

3.9    The updated data - another result of the simulation [gpd1.2.9]

Once the simulation shocks have worked their way through the economy, prices and quantities change (as reported by the simulation results). These price and quantity changes imply changes in the values contained in the original data base for the model. When you carry out a simulation, the GEMPACK programs compute these new values. These new values are written to a file which is referred to as the updated data or post-simulation data.

As you saw in section 3.8 above, the line

updated file iodata = <cmf>.upd ;

in the Command file SJLB.CMF means that, when you ran the simulation, the software produced the updated data file SJLB.UPD. This file contains the data as it would be after the shocks (in this case, the increase in labor supply) have worked their way through the model.

You learned in section 3.4.3 how to use ViewHAR to look at the base (or pre-simulation) data file SJ.HAR. This file is the starting point for the simulation; and, when you look at this file you see the numbers shown in Table 3.1 above.

You can also use ViewHAR to look at the updated data in file SJLB.UPD.

If you are using WinGEM, select from the main WinGEM menu : HA Files | View VIEWHAR. The ViewHAR window will appear. Click on File | Open... and select the file SJLB.UPD.

Command-prompt users can open SJLB.UPD by typing "viewhar SJLB.UPD" into the DOS box.

In ViewHAR's contents screen, each row corresponds to a different array of data on the file. Look at the column under the heading "Name" to see what data are in these arrays. Look at values within the three arrays.

You can check that these post-simulation values are consistent with the results of the simulation as discussed in section 3.7 above. For example, the p_DVHOUS results in Table 3.3 show that the value of household expenditure on commodity s2 increased by 5.8853 percent from its pre-simulation value of 4 to its post-simulation value of 4.2354 (which agrees with the Commodity 2 Households value in the table above).

The most obvious results of a simulation are the percentage changes in the variables. The updated data (which is always obtained when you run a simulation) is another important "result" of the simulation, one which is sometimes overlooked. You can look at this updated data to see how the data base has changed as a result of the simulation.

3.10    Preparing tables and graphs for a report [gpd1.2.10]

When you have run some simulations and analysed the simulation results, the next step is usually to write a report containing a selection of the results in tables or graphs.

This section describes how you can transfer simulation results into a spreadsheet program, such as Microsoft Excel. You can use the spreadsheet program to produce tables and graphs which can be copied and pasted into your report.

All the examples below start with the Solution file for Stylized Johansen SJLB.SL4 created in the example simulation described above.

• Example 1 illustrates how to copy directly from ViewSOL into the spreadsheet program.
• Examples 2 and 3 use the command-line program SLTOHT which is documented in sections 39 and 40.

Once you have suitable tables in your spreadsheet program, you can use it to create graphs of the results.

3.10.1    Example 1: Copying from ViewSOL to Spreadsheet and WordProcessor [gpd1.2.viewsolexport]

Open file SJLB.SL4 in ViewSOL. Select Format and then select Arrange vectors by size and set.

In Contents screen, click on the line Vectors size: 2 SECT 4

The Data Window shows the results for all vector variables which range over the set SECT. Use the Decimal Places list box (in middle of upper toolbar) to display at least 4 decimal places.

In the ViewSOL menu, select Export | Copy. This copies the table of numbers to the clipboard.

Open your spreadsheet program and paste into a new spreadsheet. Use the spreadsheet editing to make the table ready for the report. Copy the table from your spreadsheet and paste it into the report document in your word processor, in the usual Windows way. You should see a table like the following.

ViewSOL has many different Formats that you can use to set up the data to export. Consult the ViewSOL Help for details.

3.10.2    Example 2: Using the GEMPACK Program SLTOHT and Option SSS [gpd1.2.sltoht1]

In the previous example, you interactively pasted from ViewSOL into a spreadsheet the results for one variable.

The SLTOHT method, described here, is more fiddly to set up. However, once you have created a Spreadsheet Mapping file (see below) you can, in one operation, import results for many variables into a spreadsheet. This means that you can automate the production of quite complex reports.

SLTOHT produces a CSV (Comma Separated Value) file. This is a text file which can be opened in your spreadsheet program to import the numbers generated by the simulation. Many arrays, even big arrays with many rows and columns, can be imported, and then (perhaps after some reformatting) moved to your report.

In your text editor, create the file sj1.map which contains just the two lines:

p_xcom
p_xf

This is an example of a Spreadsheet Mapping file (see sections 39.3 and 40.1) used by the program SLTOHT to pick out particular variables on the Solution file.

If you are working in WinGEM, select from the main WinGEM menu

Other tasks... | Solution file to Header/Text (SLTOHT)

Click on the Select button and choose the Solution file SJLB.SL4.

Choose to print Totals solutions. Click the Ok button.

In the SLTOHT window, select from the menu Options | SLTOHT Options. A screen of SLTOHT option choices will appear. Click on SSS Short SpreadSheet output and select a Comma as separator. (A comma is the default choice.)

Click on Ok to accept these options and return to the main SLTOHT screen.

In the SLTOHT window, select from the menu Options | Use mapping file and select the file SJ1.MAP.

Run the program SLTOHT. This will create the CSV text file called SJLB.CSV. When the program has completed, View the text file SJLB.CSV, which is shown below (after the Command prompt case).

Command prompt Users can start SLTOHT running by typing "sltoht" and entering the responses:

SSS      ! Option SSS   
,        ! Data separator is a comma
-SHL     ! Do not include levels results
<carriage-return>    ! Finish option selection
sjlb     ! Name of Solution file
c        ! Cumulative totals
y        ! Yes, use an existing Spreadsheet mapping file
sj1.map  ! Spreadsheet mapping file name
sjlb.csv  ! Name of Output file (CSV)

Look at the file sjlb.csv in your text editor.

The output in file sjlb.csv should look like the box below with the labels and numbers separated by commas. Only the values for variables p_XCOM and p_XF are shown because these were the only two variables in the Spreadsheet Mapping file.

CSV file SJLB.CSV

Solution,sjlb,
 p_XCOM(s1),  5.8852696    ,
 p_XCOM(s2),  6.8992925    ,
 p_XF(labor:s1),  9.9999990    ,
 p_XF(capital:s1),-4.48017488E-07,
 p_XF(labor:s2),  10.000002    ,
 p_XF(capital:s2), 4.48017488E-07,

Start your spreadsheet program (for example Excel) and open the file SJLB.CSV (as a text file with commas for separators). If you format the number cells to show three decimal places, you get a neat spreadsheet table with the labels in one column and the values in the second column. (In a report you would probably want to replace the column of labels with more meaningful labels.)

Document table

3.10.3    Example 3: Using the Program SLTOHT and Option SES [gpd1.2.sltoht2]

There are various different options available in SLTOHT used to produce different kinds of tables as described in chapter 40. Option SES (Spread Sheet with Element labels) produces a table of results using the element names as row and column labels.

In your text editor, create the file sj2.map which contains just the two lines:

p_xcom : p_pc
p_xc

If you are using WinGEM, in the SLTOHT window, select from the WinGEM menu Options | SLTOHT Options. A screen of SLTOHT option choices will appear. Click on SES and select a Comma as separator. (A comma is the default choice.)

Click on Ok to accept these options and return to the main SLTOHT screen.

In the SLTOHT window, select from the menu Options | Use mapping file and select the file SJ2.MAP. Run the program SLTOHT.

SLTOHT will tell you that, by default, this will produce output file SJLB.CSV which already exists. [You created it in Example 2 above.] Click on Yes to say that you wish to change the name of the output file, and choose the name SJLB2.CSV.

When the program has completed, View the text file SJLB2.CSV, which is shown below (after the Command prompt case).

Command prompt Users can start SLTOHT running by typing "sltoht" and entering the responses:

SES      ! Option SES 
,        ! Data separator is a comma
-SHL     ! Do not include levels results
<carriage-return>    ! Finish option selection
sjlb     ! Name of Solution file
c        ! Cumulative totals
y        ! Yes, use an existing Spreadsheet mapping file
sj2.map  ! Spreadsheet mapping filename
sjlb2.csv  ! Name of Output file (CSV)

Open the file sjlb2.csv in your spreadsheet program. The values for variables p_XCOM and p_PC are shown side by side and then the array p_XC is shown below, all with element labels.

! Table of 2 variables.

! Variable p_XC # Intermediate inputs of commodity i to industry j #

! Variable p_XC(SECT:SECT) of size 2x2

You can import either of these tables into your word processor.

3.10.4    Graphs [gpd1.2.10.1]

Once you have suitable tables in your spreadsheet program, you can use it to create graphs of the results. Alternatively the Charter program supplied with GEMPACK (see section 36.2.1) can be used to produce simple graphs directly from ViewHAR or ViewSOL.

3.11    Changing the closure and shocks [gpd1.2.11]

You can carry out several simulations on the same model by changing the closure and/or the shocks in the Command file.

Note that, if you change the closure and/or shocks, but do not change the model (that is, do not change the TABLO Input file), you do not need to repeat Step 1 (running TABLO) in section 3.6. You only need to do Steps 2 and 3 there.

The following example shows you how to make a new Command file in the text editor and then run another simulation using SJ.EXE (or alternatively GEMSIM).

The new simulation is to increase the price of labor by 3 per cent and to increase the supply of capital by 10 per cent. In order to increase the price of labor, the variable p_PF("labor") needs to be exogenous. You need to change the closure and also apply these different shocks.

To change the command file SJLB.CMF, copy it to a new name SJLB2.CMF as follows:

If you are working in WinGEM, in the main WinGEM menu, choose File | Edit file... then open the file SJLB.CMF. Click on File | Save As... and save the file under the new name SJLB2.CMF.

If you are working at the Command prompt, type "copy sjlb.cmf sjlb2.cmf".

Then use the text editor to modify this file, following the steps below.

(1) In the original closure, both components of p_XFAC (supplies of labor and capital) are exogenous. Here you keep the supply of capital exogenous, but set the price (rather than the supply) of labor exogenous. [p_PF is the variable in the model denoting the percentage change in the price of the factors, labor and capital.]

Find the statement

exogenous   p_xfac ;

and change this to

exogenous   p_pf("labor")   p_xfac("capital")   ;

(Be careful not to leave a space between the variable name p_pf and the bracket. However, it does not matter if you use upper or lower case, or a mixture, in Command files.)

(2) Shock p_pf("labor"), the price of labor, by 3 per cent and shock p_xfac("capital"), the supply of capital, by 10 per cent.

You will need two separate shock commands:

 shock   p_pf("labor")   =  3  ;
 shock  p_xfac("capital") = 10 ;

[Remember to put a semicolon ";" after each statement.]

(3) Change the verbal description to describe the new closure and shocks. [This starts after "verbal description =" and ends with a semi-colon ";". There can be several lines of text in it.]

Exit from the editor after saving your changes.

If you are working in WinGEM:

If you have Source Code GEMPACK, click on Simulation | Run TG program... and then Select the TG EXE file to be SJ.EXE.

If you have an Executable-Image version, click on Simulation | GEMSIM Solve... .

Now both cases continue in the same way.

Select the Command file SJLB2.CMF.

Run the program with this Command file SJLB2.CMF. This is Step 2 of the simulation steps listed in section 3.6.

If there are errors when this runs, you will see a window headed "Error during Simulation". To correct the errors in the Command file, click on the button Edit Command file to use split screen editing. The Command file SJLB2.CMF will be shown in the top part of the screen and the LOG file in the bottom part of the screen. The errors will be marked in the LOG file, usually near the end of the file. When you have identified what is causing an error, you must make the appropriate change in the Command file in the top part of the screen (not the LOG file). The Next error button may help you to find errors. [If you have problems identifying or correcting the errors, you can find more assistance in section 4.7.2 below.] When you have corrected all errors, use File | Exit and save the changes you have made to the Command file SJLB2.CMF. Then close the error window by clicking on Close in it. Now click on Run to run the simulation again.

When SJ.EXE (or GEMSIM) has run successfully, click on Go to ViewSOL to look at the results.

If you are working at the Command prompt,

Edit the Command file sjlb2.cmf to make the changes above.

To run the simulation, type in at the Command prompt:

sj  -cmf  sjlb2.cmf

to run sj.exe or, to run GEMSIM:

gemsim -cmf sjlb2.cmf

View the Log file to see if there are any errors.

If there are errors, the errors will be marked in the LOG file (which is probably called sjlb2.log), usually near the end of the file. When you have identified what is causing an error, you must make the appropriate change in the Command file (not the LOG file). After you correct an error, rerun the simulation. [If you have problems identifying or correcting the errors, you can find more assistance in section 4.7.2 below.]

When sj.exe (or GEMSIM) has run successfully, use ViewSOL to examine the Solution file sjlb2.sl4.

3.12    How Johansen and multi-step solutions are calculated [gpd1.2.13]

Johansen solutions are approximate results of a simulation. In contrast, multi-step solutions can be made arbitrarily accurate by taking enough steps. In this section we describe the main ideas involved in calculating these different solutions.

3.12.1    The linearized equations of a model [gpd1.2.13.1]

Johansen solutions are calculated by solving the linearized equations¹⁵ of the model once; multi-step solutions are obtained by solving these equations several times.

The system of linearized equations of any model can be written in the form

C z = 0                                     (1)

where

C is the n x m matrix of coefficients of the equations, known as the Equations .Matrix (which is closely related to the Equations file¹⁶,

z is the m x 1 vector of all the variables (usually in percentage change form) of the model,

n is the total number of equations, and

m is the total number of variables.

We call C the Equations Matrix of the model¹⁷. It is often useful to think of this matrix as a rectangular array or tableau ¹⁸ with the vector variables across the top and the equation blocks along the left-hand side. Each vector variable occupies as many columns as its number of components, and each equation block occupies as many rows as the number of actual equations in it.

To illustrate this, part of the tableau for the 27 x 29 Equations Matrix C for the Stylized Johansen model (from the TABLO Input file SJ.TAB) is shown in Table 3.4.

Notice that we use the words "variable" and "equation" in two different senses. For example, we usually say that Stylized Johansen is a model with 29 variables and 27 equations, where we count as variables all the components of the vector variables and we count as equations all the individual equations in the equation blocks. In this sense, the number of variables is the number of columns in the Equations Matrix while the number of equations is the number of rows. Alternatively we may say that the TABLO Input file for Stylized Johansen has 11 variables (meaning vector variables) and 10 equations (meaning equation blocks). Usually the context will make clear which of these two meanings is intended.

                1     2       2       2            4        2
              p_Y   p_PC   p_PF    p_XCOM....   p_DVFACIN p_DVHOUS  
  cols -->      1   2  3   4  5     6  7          24..27  28  29
        rows  ___________________________________________________
           1 |   |       |       |       |      |        |      | 
 Comin     2 |   |       |       |       |      |        |      |
     4     3 |   |       |       |       |      |        |      |
           4 |___|_______|______ |_______|______|________|______|
           5 |   |       |       |       |      |        |      |
 Facin     6 |   |       |       |       |      |        |      |
     4     7 |   |       |       |       |      |        |      |
           8 |___|_______|______ |_______|______|________|______|
 House     9 |   |       |       |       |      |        |      |
     2    10 |___|_______|_______|_______|______|________|______|
             |   |       |       |       |      |        |      |
     :       |   |       |       |       |      |        |      |
     :       |   |       |       |       |      |        |      |
             |___|_______|_______|_______|______|________|______|
 Numeraire 27|   |       |       |       |      |        |      |
     1       |___|_______|_______|_______|______|________|______|

In general, n is less than m in the system of equations in (1) above, so when you carry out a simulation (Johansen or multi-step) you must specify

• (m-n) of the variables as exogenous and the remaining variables as endogenous, and
• shocks (usually percentage changes) to some of the exogenous variables.

For Stylized Johansen, the total number of variables (m) is 29 and the total number of equations (n) is 27, so we need 2 exogenous variables. We can shock either 1 or 2 of these exogenous variables.

The numerical values of some of the entries in the Equations Matrix can be seen in section 4.4.5 below.

3.12.2    Johansen solutions [gpd1.2.13.2]

Johansen solutions are defined to be solutions obtained by solving the linearized equations of the model just once. Because the levels equations of the model are usually nonlinear, the results of this calculation are only approximations (sometimes good approximations and sometimes not-so-good) to the corresponding solution of the levels equations of the model.

Once the exogenous/endogenous split has been chosen, the system of equations C z = 0 in (1) above, becomes .

A z1 = -D z2                           (2)

where z₁ and z₂ are respectively the (column) vectors of endogenous and exogenous variables,. A is n x n and D is n x (m-n).

The matrix A is referred to as the LHS Matrix (Left Hand Side Matrix) of the simulation. The LHS matrix A consists of the columns of the Equations matrix corresponding to the endogenous variables in the given closure. Similarly the columns of the matrix D are just the columns of C corresponding to the exogenous variables in the closure. The shocks are the values to use for z₂. Once these are known, we have a system

A z1 = b                               (3)

to solve (where the RHS vector b is an n x 1 vector equal to -Dz₂). It is the solution z₁ of this matrix equation (3) which is the Johansen solution of the simulation¹⁹.

3.12.3    Multi-step simulations and accurate solutions of nonlinear equations [gpd1.2.13.3]

The idea of a multi-step simulation is to break each of the shocks up into several smaller pieces. In each step, the linearized equations are solved for these smaller shocks. After each step the data, shares and elasticities are recalculated to take into account the changes from the previous step. In general, the more steps the shocks are broken into, the more accurate will be the results.

Figure 3.5 below makes this easy to visualise. In that figure we consider just one exogenous variable X (shown on the horizontal axis) and one endogenous variable Y (vertical axis); these are constrained to stay on the curve g(X,Y) = 0. We suppose that they start from initial values X₀,Y₀ at the point A and that X is shocked from value X₀ to value X₁. Ideally we should follow the curve g(X,Y)=0 in solving this. In a Johansen (that is, a 1-step) solution we follow the straight line which is a tangent to the curve at point A to reach point B_J and so get solution Y_J.

Figure 3.5 Illustration of Euler's method

In Euler's method the direction to move at each step is essentially that of the tangent to the curve at the appropriate point. In a 2-step Euler solution (see Figure above), we first go half way along this tangent to point C₂, then recompute the direction in which to move, and eventually reach point B₂, giving solution Y_E2. The exact solution is at B where Y has value Y₁. In a 4-step Euler simulation we follow a path of 4 straight-line segments, and so on for more steps.

The default method used by GEMPACK is Gragg's method which uses an even more accurate method than Euler's method for calculating the direction in which to move at each step. When the shocks are broken into N parts, Euler's method does N separate calculations while Gragg's method does N+1. Usually the computational cost of this extra calculation is more than repaid by the extra accuracy obtained. More information about Gragg's method (and the similar midpoint method) can be found in section 30.2.

So one way of increasing accuracy is to increase the number of steps. It turns out, however, that the best way to obtain an accurate solution is to carry out 2 or 3 different multi-step calculations with different numbers of steps and to then calculate the solution as an appropriate weighted average of these. This is what is meant by the extrapolated solution.

To illustrate this, we have shown below the different results for the percentage change in household expenditure 'p_Y' in the Stylized Johansen model for the simulation in section 3.1 above, in which labor supply is increased by 10 per cent and capital remains in fixed supply. The table below shows Euler and Gragg results for different step numbers and extrapolations based on them. Note that the exact result is 5.88528.

Multi-step results for different methods and step numbers
   Method     Number of steps
                1         2         4          6        100
    Euler    6.00000   5.94286   5.91412    5.90452    5.88644
    Gragg    5.89091   5.88675   5.88545    5.88529  
Extrapolated results
    From Euler 1,2-step results        5.88571    
    From Euler 1,2,4-step results      5.88527
    From Gragg 2,4,6-step results      5.88529  

Note that, in this case,

• the 4-step Gragg result is more accurate than the 100-step Euler result, and
• the result extrapolated from 1,2,4-step Euler results is much more accurate than the 100-step Euler result (even though the latter takes about 100/7 times as long to compute).

These results are typical of what happens in general.

The general messages are:

• Gragg's method is usually much more accurate than Euler's (for the same number of steps).
• If in doubt, extrapolate.
• Extrapolating from 3 different solutions is better than from 2. For example, extrapolating from Gragg 2,4 and 6-step solutions is usually better than from just 4 and 6-step solutions.

When you extrapolate, if you ask for an Extrapolation Accuracy file (or .XAC file)²⁰, this file shows how accurate the solution is for each endogenous variable. The separate columns show the results for the different multi-step solutions calculated, and the last column of results is the extrapolated result. When you extrapolate from 3 different multi-step results (which is what we recommend), the last two columns give conservative information about the accuracy of each result. (If they show M figures agreement, this means that the 2 different extrapolations based respectively on just the first two and just the first and third agree to this number of figures.)

For example, for the 1,2,4-step Euler results for household expenditure 'p_Y' reported above for the SJLB.CMF simulation (see sections 3.4), the relevant line in the Extrapolation Accuracy file would²¹ be

p_Y     1       6.00000    5.94286   5.91412   5.88527   CX  4  L5

The results are the 1,2,4-step results and the extrapolation based on them. The comment "CX 4" is an abbreviation meaning that you can have confidence in the extrapolated result (this is the 'CX') and that the two extrapolations (the first based just on the 1,2-step results and the second based on the 2,4-step results) agree to 4 figures (or more). Note that the agreements are reported as figures, not decimal places. (For example 123.4567 and 123.4014 agree to 4 figures, but only one decimal place.) The abbreviations (such as 'CX') used on this file are explained at the top of the file. (The first "1" in the line displayed above means that this line refers to the first - in this case, the only - component of variable p_Y.) The "L5" at the end of this line means that you can be confident of 5 figures accuracy in the level of income Y. [See section 26.2.1 for more details.]

At the end of the file is a summary (we refer to it as the Extrapolation Accuracy Summary) which states how many components fall into each category (EMA, CX etc). For a simulation with Stylized Johansen, this may look something like that shown below.

SUMMARY OF CONVERGENCE RESULTS                 Number  Min Figs Agree
      ------------------------------           ------  --------------
 EMA  Last two results equal to machine accuracy  3         6
 FC0  Fair confidence that the result is zero     2
 CX   Confidence in the extrapolated result      22         2  
   2 results are judged accurate to 2 figures.
   4 results are judged accurate to 3 figures.
   16 results are judged accurate to 4 figures.
   3 results are judged accurate to 6 figures.
 
  Above is for linearised variables.
  Below are for levels values of percent-change and change results.

   1 results are judged accurate to 4 figures.
   21 results are judged accurate to 5 figures.
   5 results are judged accurate to 6 figures.
   
    (The summary above covers the XAC-retained variables.)    

The first part is a summary of the number of times different comments (in the example above, "EMA", "FC0" and "CX") have been used for the different results. The second part tells how many results (linearised, then levels) have been judged accurate to different numbers of figures.

More details about Extrapolation Accuracy Summaries and Extrapolation Accuracy files are given in section 26.2.

The only restriction on step numbers is that, for Gragg's method and the midpoint method, the step numbers must either be all odd or all even (for example, 2,4,6 or 3,5,7). Note also that a 1-step Gragg or midpoint is a little unusual and is probably best avoided (since it is more like Euler than Gragg or midpoint).

More details are given in section 30.2 and some of the theory behind multi-step methods can be found in Pearson (1991).

3.12.4    Smiling or frowning face numbers are reported [gpd5.9.2.1]

If you use WinGEM, RunGEM or RunGTAP, you know that after each simulation is completed, you see smiling or frowning faces which indicate how accurately the simulation was solved (provided that you are extrapolating from 3 multi-step calculations). Within ViewSOL, the accuracy summary can be displayed via an icon:

on the upper toolbar.

At the end of the simulation, and at the end of each subinterval if there is more than one, GEMSIM and TABLO-generated programs report (to the terminal and to the LOG file) the face number (between 1 and 10, where 10 is accurate and 1 is very inaccurate). Separate face numbers are shown for the variable and the data accuracy. If there is more than one subinterval, the face number for the overall variable accuracy is shown at the end of the Overall Accuracy Summary (see section 26.3.1).

3.12.5    Fatal error if accuracy too low (GEMSIM and TG-programs) [gpd5.9.2.2]

Suppose that you are extrapolating from 3 multi-step calculations. If the accuracy is extremely low, it is highly unlikely that the simulation results are of any value. Accordingly, the program stops with a fatal error in order to draw your attention to this poor accuracy (but the solution file is still saved).

This can happen at the end of the whole simulation, or it can happen at the end of any subinterval which is solved inaccurately. However it does not happen at the end of a subinterval if you are using automatic accuracy since then you may redo the subinterval in question.

We believe it is your responsibility to decide whether or not a simulation has been solved sufficiently accurately. You should always look at the information provided by the software, especially the Accuracy Summaries (see sections 26.2 and 26.3.1). We are reluctant to intervene and, as when equations are not satisfied very accurately (see section 30.6.1), we end with a fatal error only in what we consider are extreme cases. At present, if any of the face numbers is 3 or less, we stop with a fatal error. Choosing 3 here does not mean that we think face numbers 4,5 and 6 are ok (since often they will not be) - rather we leave the decision to you in such cases.

3.13    GEMPACK programs - an overview [gpd1.2.14]

As you have already seen, GEMPACK is not a single program. There are a number of different programs making up GEMPACK. In this section we give a brief overview of these different programs, grouped by task.

You have not yet used all of the programs below. As you become more experienced with GEMPACK, you may need to come back to this section to check out those programs you have not used.

3.13.1    Working with TABLO input files [gpd1.2.14.1]

TABmate is a special editor for TABLO Input (TAB) files. Use TABmate to create and modify the theory of a model - that is, the TABLO Input file for the model.

TABLO converts the model TAB file into a TABLO-generated program or Auxiliary files for GEMSIM. You must do this before you can carry out a simulation with a model. [See Step 1 in section 3.6.]

In fact TABmate runs the program TABLO in the background. So TABmate and TABLO can perform very similar functions. You can use either TABLO or TABmate to carry out Step 1 for simulations (see section 3.6).

3.13.2    Carrying out simulations [gpd1.2.14.2]

You can use either GEMSIM or the relevant TABLO-generated program to carry out Step 2 for simulations (see section 3.6). Which you use depends on how you ran TABLO in Step 1 (see section 3.6.1 or 3.6.2 above).

GEMSIM. Run GEMSIM to carry out a simulation. Specify the Auxiliary files, starting data files, closure and shocks in a Command file.

TABLO-generated program. Run the EXE file of the TABLO-generated program to carry out a simulation. Specify the starting data files, closure and shocks in a Command file. You can only create TABLO-generated programs if you have a Source-code version of GEMPACK.

3.13.3    Looking at, and processing, simulation results [gpd1.2.14.3]

ViewSOL is for looking at results — see Step 3 in section 3.6.

AnalyseGE is for analysing simulation results. You can view model equations, simulation results and the values of items in the data base. Section 36.6 introduces AnalyseGE. A hands-on introduction to AnalyseGE in the context of a simulation with Stylized Johansen can be found in section 46.1.

SLTOHT is a command-line program that converts simulation results (on a Solution file) either (a) into tables of results which you can import into a spreadsheet, or (b) into a Header Array file. See section 3.10 above and chapters 39 and 40 for information about SLTOHT.

When you report simulation results, you will probably use other standard tools (including spreadsheet programs such as Excel) for making tables and graphs.

3.13.4    Working with data [gpd1.2.14.4]

In GEMPACK data for models are usually held on Header Array files. Because these are binary (ie, non-text) files, you need special programs to work with the data in this form.

ViewHAR is for looking at data on Header Array files. You used ViewHAR to look at original and updated data in the Stylized Johansen example above. ViewHAR can also be used to create a Header Array file and to modify data on a Header Array file (see section 6.1 below and section 6.2).

CMPHAR can be used to compare the data on two Header Array files — see section 37.2.

CMBHAR can be used to combine the data on two or more Header Array files (for example, data representing two or more years). See section 37.3.

Data comes from various sources. You may use other standard tools and programs (including spreadsheet programs such as Excel) when working with data.

3.13.5    Windows modelling environments [gpd1.2.14.5]

WinGEM provides a Windows environment for carrying out modelling and associated tasks.

RunGEM provides a Windows environment for carrying out simulations with a fixed model. Users with little experience of modelling can carry out simulations by choosing just the closure and shocks. See section 36.5 and chapter 45.

RunDynam and variants including RunGDyn are sold as as a separate product. They are Windows interfaces for use with recursive dynamic models such as USAGE and dynamic GTAP. See section 36.7.

3.13.6    Other programs for special tasks [gpd1.2.14.6]

These are programs used for specialised tasks, usually by power users. You will not need to use any of them until you are more experienced with GEMPACK.

ACCUM and DEVIA are used for working with recursive dynamic models such as USAGE which are solved annually over a period of several years. ACCUM and DEVIA collect the results for several years. [See chapter 41.]

SUMEQ is for looking at data on an Equations file. SUMEQ can also be used to diagnose homogeneity problems with a model — see chapter 79.

SEENV is for working with Environment files (which store the set of exogenous and endogenous variables in one closure for a model) — see chapter 56.

3.13.7    Programs for use on non-Windows PCs [gpd1.2.14.7]

Windows programs, such as WinGEM, ViewHAR or ViewSOL, will not run on non-Windows PCs²² -- so other, command-line programs are needed to turn data (HAR) and results (SL4) files into text files that you can view. These are:

SEEHAR turns a Header Array file into a viewable text file — see section 37.1.

3.14    Different GEMPACK files [gpd1.2.15]

As you have seen, GEMPACK programs produce and use several different types of files (for example, Solution files and Header Array files). New users often ask us "Why are there so many different files?".

In this section we give more details about these different files and how they are used.

In our experience, some users are keen to have detailed information about this topic while others are not very interested. Since a detailed knowledge about this topic is not essential for doing effective modelling, you should feel free to skip this section or to skim it very quickly. You can always refer back to it later on, if and when you need to.

A table summarising the different files is given in section 3.14.6 below.

3.14.1    The most important files [gpd1.2.15.1]

We begin with the most important files, namely TABLO Input files, data files, Command files and Solution files, all of which you have met earlier in this chapter.

TABLO Input files. These contain the theory (equations etc) for a model. Alternatively they may be for data manipulation. These files have suffix .TAB. These files are inputs to the program TABLO. The program TABmate (see section 36.4) can be used to create and or modify these files.

Data files. These may be Header Array files or text files. The suffix is not prescribed by the software, though suffix .HAR is recommended (.DAT is sometimes used). Data files can be inputs to a simulation (the original input-output data, the parameters) and updated versions are output from a simulation. Updated data files are usually given the suffix .UPD . Chapter 6 below contains an introduction to the different ways in which you can create data files and modify data on existing data files.

Command files. These contain the details of a simulation, including closure, shocks, starting data and solution method (see section 3.8). The suffix is not prescribed by the software, though .CMF is usual²³. Command files are inputs for GEMSIM and TABLO-generated programs. The statements allowed in Command files are documented in chapter 35.

Solution files. These are the main outputs from a simulation. They contain the change or percentage change results for all the linearized variables. They may also contain levels results. These files have suffix .SL4. They are inputs to various post-simulation programs such as ViewSOL, SLTOHT, and AnalyseGE. Solution files are documented in chapter 27.

Equations files. These contain numerical versions of the linearized equations of a model. They are usually only produced when you wish to use SAGEM to obtain several Johansen (approximate) solutions of a model, as explained in chapter 58. You may also create an Equations file if your model is not homogeneous in prices or quantities (see section 79.1). Equations files have suffix .EQ4. Equations files are documented in chapter 59.

Shock files. Sometimes it is necessary to shock the different components of a variable by different amounts. If the variable has a large number of components, or if the shocks are calculated by a program, it is convenient to put the numerical values of the shocks onto a so-called "shocks file". This file may be a text file or a Header Array file. The suffix for shocks files is not prescribed by the software, though often .SHK is used. The use of shock files is documented in sections 24 to 66.2.

Solution Coefficients (SLC) files. These are output from a simulation. They contain the pre-simulation values of all data and of all Coefficients in the TABLO Input file for the model. These files have suffix .SLC and have the same name (apart from suffix) as the Solution file from the simulation²⁴. The program AnalyseGE reads both the Solution and SLC file when you analyse the results of a simulation²⁵. You can also examine SLC files with ViewHAR. SLC files are documented in section 28.1.

Extrapolation Accuracy files. You can ask²⁶ for an Extrapolation Accuracy file to be produced when you extrapolate from 3 separate multi-step calculations (as you have seen in section 3.12.3 above). These text files show estimates as to how accurate the different simulation results are. They have suffix .XAC and have the same name (apart from suffix) as the Solution file from the simulation. Extrapolation Accuracy files are documented in section 26.2.

3.14.2    Files for communication between programs [gpd1.2.15.2]

There are a number of files which are used for communication between programs. The most important of these are the Auxiliary files which allow communication between TABLO and GEMSIM or the TABLO-generated program.

Auxiliary files. These are either

• Auxiliary files for a TABLO-generated program. These are produced when TABLO writes a TABLO-generated program (see section 3.6.1 above). These files have suffix .AXS (Auxiliary Statement file) and .AXT (Auxiliary Table file).
• GEMSIM Auxiliary files. These are produced when TABLO writes output for GEMSIM (see section 3.6.2 above). These files have suffix .GSS (GEMSIM Statement file) and .GST (GEMSIM Table file).

TABLO-generated program (Fortran file). This is the Fortran (.FOR) file for the TABLO-generated program which is produced by TABLO (see section 3.6.1 above). Auxiliary files (.AXS and .AXT files) are always produced at the same time. In Step 1(b) for simulations (see section 3.6.1), this program is compiled and linked to produce the EXE file of the TABLO-generated program²⁷. It is this EXE file which is run to carry out a simulation.

When the EXE file of a TABLO-generated program is used to carry out a simulation, the Auxiliary files (AXS and AXT files) are required. They communicate vital information from the TABLO Input file to the simulation.

Similarly, if GEMSIM is used to carry out a simulation, the GEMSIM Auxiliary files (GSS and GST files) are required.

3.14.3    LOG files [gpd1.2.15.3]

Often a program runs very quickly and/or puts a lot of information on the screen. If you need to check this output (for example, to see where an error occurs), you can ask for a LOG file to be created²⁸. You can then look at this log file in your favourite text editor. The suffix for LOG files is not prescribed by the software, though suffix .LOG is usual.

3.14.4    Stored-input (STI) files [gpd1.2.15.4]

These days, GEMPACK Windows programs such as TABmate, RunDynam or WinGEM are the main interface seen by most GEMPACK users — but a lot of the work they seem to perform is in fact carried out by command-line programs running in the background.

In previous times, before the GEMPACK Windows programs were available, GEMPACK users usually ran programs like TABLO, GEMSIM and SLTOHT from the command line. The program would ask a sequence of questions — the responses were usually single letters (to indicate options) or filenames (for input and output).

Obviously it could be very tedious to repeatedly run programs in this way. Stored-input files or STI files were a way to reduce the drudgery — they consist of a text file which stores the necessary responses to the questions that the program asked. Then, to repeat an SLTOHT job, one merely typed, say:

sltoht -sti report3.sti

where report3.sti is a text file of the responses needed to generate some report. To produce report3.sti you would, the first time you ran this job, either note responses on a scrap of paper (the old way) or activate the SIF option in SLTOHT which will record your responses in a file.

STI files are rather hard to read and understand — you only see one half of a conversation.

For modern GEMPACK users the most-frequently encountered STI files may be those used for input to TABLO which specify the condensation (section 14.1.2 gives an example). For new models you can and should specify condensation actions — such as Omit, Substitute and BackSolve — within the TAB file, but this option is relatively new, so many older models still use a STI file to store the condensation.

Apart from this, the main remaining uses of STI files are:

• to automate the running of SLTOHT or some other command-line programs which need to be run repeatedly
• to activate some rarely used options in TABLO or other programs. A few options are only accessible via STI files (or by direct responses to program queries).

Stored-input files are further described in section 48.3. They usually have suffix .STI (although other suffixes may be used). You will need to learn about STI files as you become more experienced. You can find introductory examples of creating and working with them in sections 14.1.2, 14.1.4 and 54.11.

3.14.5    Files for power users [gpd1.2.15.5]

A number of files can be created in order to speed up or simplify subsequent tasks. These are typically used mainly by experienced GEMPACK users so you don't need to know any details about them at this stage. Examples are Stored-input files (see section 3.14.4 above), Environment files (see section 23.2) and various Mapping files (see sections 39.3, 39.8 and 40.1).

3.14.6    Summary of files [gpd1.2.15.7]

3.14.7    Work files [gpd1.2.15.6]

Many programs create and use working files while they are running. These work files can be large. Usually these work files are deleted when the program finishes so you do not see them or need to know about them. Occasionally these files are left around on your hard disk if the program finishes with an error. See below or section 30.7 for more details.

3.14.8    Files you can eventually delete [junkfiles]

Especially when running multiperiod simulations, GEMPACK tends to create many output files — most of which will not be needed in a few days time. A list of these 'junk files' appear below. A command-line program, GPDEL, is provided, which will remove many of these files. From a command prompt in your working folder, type:

GPDEL

to see instructions for using it. Alternatively, TABmate's Tools..Delete Junk files menu item offers another way to cull files.

3.15    For new users - what next? [gpd1.2.16]

Congratulations. You have just learnt the most important things about GEMPACK, namely how to set up and carry out simulations, and how to look at the results.

Where you go next in learning about GEMPACK depends on your main purpose in using the software.

• If you mainly want to carry out simulations with another standard model, you will find a list of the models supplied with GEMPACK in section 1.5. If the model you wish to work with is one of these, you will find detailed hands-on guidance in chapter 43 about carrying out standard simulations with many of these models. If you wish to work with another model, the model developers have probably supplied and documented one or more standard simulations. We suggest that you start with those.
• With a well-documented model and good software, it is relatively easy to carry out simulations and produce, and report, a large number of results. It is less easy to really understand these results. The GEMPACK program AnalyseGE (see section 36.6) provides valuable assistance to you in this task. You can find a hands-on introduction to AnalyseGE in the context of a Stylized Johansen simulation in section 46.1. Pearson et al. (2002) provides a hands-on introduction to AnalyseGE in the context of simulations with GTAP. We encourage you to explore the use of AnalyseGE as you analyse the results of simulations you carry out.
• If you want to build your own model (or modify someone else's), or if you just want to understand how a model is implemented in GEMPACK, you should read chapter 4. Perhaps read it quickly the first time and then go back for a more detailed study.
• If you need to build or modify the data files for a model, you should read chapter 6.
• When you want to know more about the GEMPACK utility programs (say, for report generation or post-simulation processing of results), look at the detailed documentation in Chapters 36 to 40.
• When you want to know more about running the GEMPACK programs, read chapter 48. This chapter gives detailed suggestions for more efficient use of the programs whether you are running them interactively or in batch mode.

Whatever your main interest, we strongly encourage you to at least skim chapter 4 first, and then go on to your main interest. You must be familiar with at least the basics of TABLO Input (TAB) files in order to work properly with, and understand, any model implemented via GEMPACK.

4    Building or modifying models [gpd1.3]

Click here for detailed chapter contents

In order to build a model within GEMPACK, it is necessary to prepare a TABLO Input file containing the equations of the model and to construct one or more data files whose purpose is essentially to give one solution of the levels equations of the model.

The preparation of a TABLO Input file involves

• writing down the equations in a suitable form. You can use levels equations, linearized equations or a mixture of these. We discuss this in section 4.1 below.
• working out the data requirements of the model. This is discussed in section 4.2 below.

We describe the preparation of TABLO Input files in section 4.3 and the preparation of the actual data files in chapter 6. We illustrate each step in the process by doing it for the Stylized Johansen model.

Of course, to modify an existing model, you modify the TABLO Input file (to change the theory of the model) and/or the data file(s).

The TABLO Input file given for Stylized Johansen in section 4.3.3 is a mixed one (in the sense that it contains a mixture of linearized and levels equations). In sections 4.4.1 and 4.5.1 we describe alternative TABLO Input files for Stylized Johansen consisting only of linearized or levels equations respectively.

TABLO linearizes all levels equations in TABLO Input files and converts all levels variables to the associated linear ones (change or percentage change in the associated levels variables). This is described in section 4.6.

We conclude this chapter in section 4.7 where we give you advice about building your own model by writing a TABLO Input file from scratch or by modifying an existing one. We include hands-on examples showing how to identify and correct errors in TABLO Input files and Command files.

If you are familiar with using GAMS for general equilibrium modelling, you may prefer to work through the document Kohlhaas and Pearson (2002) instead of, or before, reading this chapter. The many similarities between GEMPACK and GAMS make it relatively easy for a GAMS modeller to begin using GEMPACK productively.

Table 4.1 Levels and linearized equations of the Stylized Johansen model

In Table 4.1, upper-case Roman letters represent the levels of the variables; lower-case Roman letters are the corresponding percentage changes (which are the variables of the linearized version shown in the second column). The letters P, X and D denote prices, quantities and dollar values respectively, while the symbols A and a denote parameters. Subscripts 1 and 2 refer to the (single) commodities produced by industries 1 and 2 (subscript i), or to the industries themselves (subscript j); i = 3 refers to labour while i = 4 refers to the model's one (mobile-between-industries) type of capital; subscript j = 0 identifies consumption. Because the first three equation blocks are identically linear in the logarithms they are natural candidates for presentation and explanation of the model.

4.1    Writing down the equations of a model [gpd1.3.1]

TABLO Input files contain the equations of a model written down in a syntax which is very similar to ordinary algebra. Once you have written down the equations of your model in ordinary algebra, it is a simple matter to put them into a TABLO Input file, as we illustrate in section 3.3 below.

You are free to use levels or linearized versions of the equations or a mixture of these two types. For example, if a certain dollar value D is the product of the price P and quantity Q, the levels equation is

D = P * Q

(where the "*" indicates multiplication), and the associated linearized equation is

p_D = p_P + p_Q

where "p_" denotes "percentage change in". The linearized version says that, to first order of approximation, the percentage-change in the dollar value is the sum of the percentage changes in the price and the quantity. Whichever version of the equation you include, GEMPACK can still produce accurate solutions of the underlying levels equations (which are usually nonlinear).

We say more about the process of linearizing equations in section 3.7 below.

The best way of making the above clear is to take a concrete example, as we do below, using Stylized Johansen as our example model.

4.1.1    Writing down the equations of Stylized Johansen [gpd1.3.1.1]

We start from the equations as written down in Chapter 3 of DPPW (to which we refer readers interested in the derivation of, and motivation behind, these equations). An excerpt from that chapter, SJ.PDF, is included in the "examples" subfolder of your GEMPACK directory.

The equations of the model are shown in Table 4.1. In that table, both the levels and linearized versions of each equation are shown, taken essentially unchanged from DPPW¹. Notice that upper case letters (for example, X) denote levels quantities while lower case letters (for example, x) denote percentage change in the corresponding levels quantity.

For our first implementation of Stylized Johansen (see section 4.3 below), we have chosen a mixed representation, based on the shaded blocks in Table 4.1. That is, we decided to use the levels versions of some of the equations (most are accounting identities and one is the numeraire equation) and the linearized versions of the top three equations (which are behavioural equations). Later, in sections 4.4 and 4.5 respectively, we describe implementations based on exclusively linearized equations (section 4.4) and exclusively levels equations (section 4.5). Of course, each of these 3 implementations is valid and all three produce the same results.

The notation in DPPW involves a liberal use of subscripts which are not suitable for the linear type of input usually required by computers (and required in the TABLO Input file). Hence we use a different notation. The levels variables of the model are as follows. In DPPW subscripts 1 and 2 refer to sectors (commodity or industry), subscripts 3 and 4 refer to factors (3 is labor and 4 is capital) while subscript 0 refers to households.

We introduce sets SECT, the set of two sectors say "s1" and "s2", and FAC, the set of the two factors "labor" and "capital".

Below in Table 4.4, we have rewritten the selected equations from Table 4.1, this time using the GEMPACK variables and notation as in Tables 4.2 and 4.3. Note that below we also use the GEMPACK convention that "p_" indicates percentage change in the relevant levels variable. For example, p_XH(i) denotes the percentage change in XH(i), household consumption of commodity i. In these equations we use "*" to denote multiplication and "/" to denote division. We also use SUM(i,<set>,<expression>) to denote sums (usually expressed via Greek sigma) over all i in the set <set>; here <set> is SECT or FAC.

Note that below we also use the GEMPACK convention that "p_" indicates percentage change in the relevant levels variable. For example, p_XH(i) denotes the percentage change in XH(i), household consumption of commodity i. In these equations we use "*" to denote multiplication and "/" to denote division. We also use SUM(i,<set>,<expression>) to denote sums (usually expressed via Greek sigma) over all i in the set <set>; here <set> is SECT or FAC.

        Equation                                      Subscripts         No. in DPPW
(E1)  p_XH(i)   = p_Y - p_PC(i)                       i in SECT          E3.2.1
(E2)  p_XC(i,j) = p_XCOM(j) - [p_PC(i) - p_PC(j)]     i,j in SECT        E3.2.2, E3.2.3
(E3)  p_XF(f,j) = p_XCOM(j) - [p_PF(f) - p_PC(j)]     f in FAC,j in SECT E3.2.2, E3.2.3
(E4)  p_PC(j)   = SUM(i,SECT, ALPHACOM(i,j)*p_PC(i)) 
                + SUM(f,FAC,  ALPHAFAC(f,j)*p_PF(f))  j in SECT          E3.2.3
(E5)  XCOM(i)   = XH(i) + SUM(j,SECT, XC(i,j))        i in SECT          E3.1.6  
(E6)  XFAC(f)   = SUM(j,SECT, XF(f,j))                f in FAC           E3.1.7  
(E7)  PC("s1")  = 1.                                                     E3.1.23 
(E8)  XC(i,j)   = DVCOMIN(i,j) / PC(i)                i,j in SECT           -
(E9)  XH(i)     = DVHOUS(i) / PC(i)                   i in SECT             -
(E10) XF(f,j)   = DVFACIN(f,j) / PF(f)                f in FAC, j in SECT   -

These equations appear essentially as above in the TABLO Input file (see section 4.3.3 below).

4.2    Data requirements for the linearized equations [gpd1.3.2]

As a general rule, GEMPACK requires an initial levels solution of the model. Thus it is necessary to provide data from which initial (that is, pre-simulation) values of all levels variables and the values of all parameters of the model can be inferred. As we shall see in section 4.2.1 for Stylized Johansen, it is frequently the case that the data required are

• mainly dollar values (rather than separate prices and quantities), and
• certain parameters (such as elasticities).

Once dollar values are known, it is often possible to set basic prices equal to 1 (this amounts to a choice of units for the related quantities), from which the quantities can be derived by dividing the dollar value by the price. [The choice of 1 for the basic price is, of course, arbitrary. Any other fixed value would be as good.]

4.2.1    Data requirements for Stylized Johansen [gpd1.3.2.1]

Suppose that we know the following pre-simulation dollar values.

DVCOMIN(i,j)    Intermediate inputs
DVHOUS(i)       Household consumption
DVFACIN(f,j)    Factor use by industry 

Then, if we set all the prices to one for

PC(i)           Price of commodities
PF(f)           Price of factors  

we can infer all other levels variables in Table 4.2 as follows.

XC(i,j) = DVCOMIN(i,j) / PC(i)      Intermediate inputs     
XH(i)   = DVHOUS(i) / PC(i)         Household use     
XF(f,j) = DVFACIN(i,j) / PF(f)      Factor use     
Y       = SUM(i, SECT, DVHOUS(i))   Household expenditure 

The only other quantities in the equations (E1)-(E10) are the parameters ALPHACOM(i,j) and ALPHAFAC(f,j) in (E4). Because there is a Cobb-Douglas production function involved, it is well-known that these are cost shares, namely

ALPHACOM(i,j) = DVCOMIN(i,j) / DVCOSTS(j),     
ALPHAFAC(f,j) = DVFACIN(f,j) / DVCOSTS(j), 

where DVCOSTS(j) is an abbreviation for

SUM(i, SECT, DVCOMIN(i,j)) + SUM(f, FAC,  DVFACIN(f,j)),

the total costs in industry j. [These results are easily obtained from equations (E3.1.10) and (E3.1.12) in DPPW.]

Thus the only data requirements are the dollar values

DVHOUS(i),  DVCOMIN(i,j)  and  DVFACIN(f,j)

One instance of the data required is as shown in the body of Table 3.1 in section 3.1.1 above.

In the TABLO Input file, the pre-simulation values of these data will be read and the values of all others will be calculated from them.

4.3    Constructing the TABLO input file for a model [gpd1.3.3]

The TABLO Input file of the model is the means of communicating the theory of the model to the computer, in particular to the GEMPACK program TABLO. It consists of the equations written in a syntax which is very similar to ordinary algebra. It also contains a description of the data to be read, where it is to be read from, and how this data is to be used to calculate values of parameters and pre-simulation values of the other levels variables occurring in the equations.

The main part of a TABLO Input file is the equations, which usually come at the end of the file. Before the equations must come

• the VARIABLEs (levels or linearized);
• the SETs used to describe the different arguments of variables;
• the data to be read;
• calculations of the pre-simulation values of any levels variables not read in as data (calculations are done via FORMULAs);
• calculations (via FORMULAs) of any parameters whose values are not read in;
• logical names of the associated data files;
• the headers on the data file(s) where the different pieces of data are to be found (if the data files are GEMPACK Header Array files — see chapter 5).

The order of these in the TABLO Input file is somewhat flexible but follows the general rule that items cannot be used until they have been declared. Thus the SET statements (saying which sets are involved) usually come first. Then the declarations of data files (via FILE statements) often come next, followed by the declarations of the VARIABLEs and parameters.

These ideas are best learnt and understood by example. Hence we launch straight into the preparation of the TABLO Input file for Stylized Johansen.

4.3.1    Viewing the TABLO input file [gpd1.3.3.1]

When working with GEMPACK, many of the input files that you create are text files, so you need a text editor. You can use any text editor you are familiar with.

GEMPACK includes two text editors, TABmate and GemEdit. We suggest you use TABmate since it has coloured highlighting of TABLO syntax, and a powerful Gloss feature which displays all parts of the TABLO code where a chosen variable or coefficient is used. If TABmate is not the default editor in WinGEM, select, in the WinGEM main menu,

Options | Change editor...

then select your editor Use TABmate. You should only have to do this once: WinGEM should remember which editor you chose.

Open the TABLO Input file for Stylized Johansen SJ.TAB in the TABmate editor. In WinGEM, to edit a text file, select in the WinGEM menu,

File | Edit file...

The edit box should show various files in the directory C:\SJ. If the Open box does not start at the correct directory C:\SJ, set the Working directory again as described in section 3.4.2.

Select the file SJ.TAB, the TABLO Input file for the Stylized Johansen model.

Search the TABLO Input file for "EQUATION House" using Search | Find. We will discuss the details of this equation in the next section.

4.3.2    Constructing part of the TABLO input file for Stylized Johansen [gpd1.3.3.2]

In this subsection we consider just two equations of Stylized Johansen, namely (E9) and (E4) in section 4.1.1 above. We show how these are written in the TABLO Input file. (We show the full TABLO Input file in section 4.3.3 and then discuss the rest of this file in section 4.3.4 below.)

Equation (E9)

Consider the very simple equation (E9) relating prices, quantities and dollar values of household consumption.

In the TABLO Input file this equation is written as²

EQUATION House # Household demand for commodity i #
    (all,i,SECT) XH(i) = DVHOUS(i) / PC(i) ;

where

• EQUATION is a keyword indicating that what follows is an equation,
• House is the name by which this equation is known in the model,
• the words between the hashes # form optional additional labelling information which is associated with the equation,
• the quantifier (all,i,SECT) indicates that there are really several equations, one for each sector, and
• the semicolon ; marks the end of this part of the equation statement.

For this equation to be meaningful, we must explain in the TABLO Input file all the names used in the equation.

The levels variables are declared (that is, explained) via the statements

VARIABLE (all,i,SECT) XH(i)  .    # Household demand for commodity i # ; 
VARIABLE (all,i,SECT) DVHOUS(i).  # Dollar value of household use of commodity i # ; 
VARIABLE (all,i,SECT) PC(i)       # Price of commodity i # ;

Notice that, by convention, these declarations also declare associated linear variables p_XH, p_DVHOUS and p_PC which denote the percentage-change in the relevant levels variables. These linear variable names are used in reporting simulation results (see the results in section 3.7 above, for example) and are available for use in linearized equations in the TABLO Input file (see, for example, the EQUATION named "Price_formation" discussed later in this section) without further explicit declaration.

The fact that SECT is a set with two sectors "s1" and "s2" in it is indicated via the SET statement

SET SECT  # Sectors #   (s1-s2) ;

We must also indicate how pre-simulation values of the levels variables can be read or calculated from the data base. We do this via the statements

READ DVHOUS  from FILE iodata HEADER "HCON" ; 
FORMULA (all,i,SECT)   PC(i) = 1 ; 
FORMULA (all,i,SECT)   XH(i) = DVHOUS(i)/PC(i) ;

In the first of the above statements,

• READ is the keyword,
• iodata is the (logical) name by which the particular data file containing this input-output data is known in the TABLO Input file, and
• the Header "HCON" tells where on the file the relevant array of data is to be found.

In the second and third statements, FORMULA is the keyword.

The third of these contains the same expression as the equation we are considering. Indeed, we can combine the EQUATION and FORMULA into a single statement on the TABLO Input file, namely.³

FORMULA & EQUATION House # Household demand for commodity i #
  (all,i,SECT)   XH(i) = DVHOUS(i) / PC(i) ;

The statement

FILE iodata # input-output data for the model # ;

declares "iodata" as the logical name⁴ of the file containing the actual data.

This ends the discussion of the equation (E9) and of all the statements needed for the EQUATION House.

Using the Gloss feature in TABmate

In TABmate, there is a quick way of finding all places where a name such as XH occurs in the TABLO Input file SJ.TAB. In TABmate, click on TABLO Check in the bar near the top of the TABmate screen⁵. Click on the word EQUATION in the "EQUATION House" and then click on Gloss in the bar near the top of the TABmate screen. A box (shown below) appears showing all names used in the EQUATION House in the TABLO Input file.

FORMULA & EQUATION House # Household demand for commodity i # 
   (all,i,SECT) XH(i) = DVHOUS(i) / PC(i) ;
Line
~41: SET SECT # Sectors # (s1-s2) ;
~69: Coefficient Variable (GE 0) (all,i,SECT) XH(i) # Household demand for commodity i # ;
~86: Coefficient Variable (GE 0) (all,i,SECT) DVHOUS(i)
                                        # Dollar value of household use of commodity i # ;
~59: Coefficient Variable (GE 0) (all,i,SECT) PC(i) # Price of commodity i # ;

Click on the X in the top right-hand corner of the Glossary box to exit from the Gloss box.

Click on the word XH in the "EQUATION House" and then click on the Gloss button. The Gloss box (shown below) appears showing all occurrences of the name XH in the TABLO Input file.

Coefficient   XH
Line
~69: Variable (GE 0) (all,i,SECT) XH(i) # Household demand for commodity i # ;
~138: FORMULA & EQUATION House # Household demand for commodity i #
   (all,i,SECT) XH(i) = DVHOUS(i) / PC(i) ;
~142: FORMULA & EQUATION Com_clear # Commodity market clearing #
   (all,i,SECT) XCOM(i) = XH(i)+SUM(j,SECT,XC(i,j));

Try clicking on the word DVHOUS to see where DVHOUS is used in the TABLO Input file SJ.TAB.

Equation (E4)

Now consider the equation (E4) "price formation for commodities". This is written in the TABLO Input file as

EQUATION (LINEAR) Price_formation 
         (all,j,SECT) p_PC(j) = SUM(i,SECT, ALPHACOM(i,j)*p_PC(i)) +
                                SUM(f,FAC,  ALPHAFAC(f,j)*p_PF(f)) ; 

in which

• the qualifier (LINEAR) indicates that this is a linearized equation (not a levels equation),
• the fact that p_PC(i) and p_PF(f) are percentage-changes in the levels variables PC(i) and PF(f) is guaranteed by the convention that, once these levels variables have been declared via

VARIABLE (all,i,SECT) PC(i) # Price of commodity i # ; 
VARIABLE (all,f,FAC)  PF(f) # Price of factor f # ;

the associated linear variables p_PC(i) and p_PF(f) are automatically considered declared. In this equation, ALPHACOM and ALPHAFAC are parameters. To calculate ALPHACOM and ALPHAFAC from the data base, FORMULA statements are used:

FORMULA  .# Share of intermediate commodity i in costs of industry j # 
(all,i,SECT)(all,j,SECT)  ALPHACOM(i,j) = DVCOMIN(i,j) /
    [SUM(ii,SECT,DVCOMIN(ii,j)) + SUM(ff,FAC,DVFACIN(ff,j)) ] ;
FORMULA  .# Share of factor input f in costs of industry j # 
(all,f,FAC)(all,j,SECT)  ALPHAFAC(f,j) = DVFACIN(f,j) /
    [SUM(ii,SECT,DVCOMIN(ii,j)) + SUM(ff,FAC,DVFACIN(ff,j)) ] ;

where FORMULA is the keyword. The fact that ALPHACOM and ALPHAFAC are parameters can be indicated via the statements

COEFFICIENT(PARAMETER) (all,i,SECT)(all,j,SECT) ALPHACOM(i,j) ;
COEFFICIENT(PARAMETER) (all,f,FAC) (all,j,SECT) ALPHAFAC(f,j) ;

in which COEFFICIENT is the keyword and (PARAMETER) is a qualifier.

If you are using the TABmate editor, try using the Gloss button. Click on the word p_PC in the EQUATION Price_formation and click on the Gloss button to see all occurrences of p_PC in the TABLO Input file SJ.TAB. Click on the word "FAC" and Gloss to see all occurrences of the set FAC.

This ends the discussion of the equation (E4) and of all the statements needed for the EQUATION Price_formation.

Statements in a TABLO Input File

The main types of statements in a TABLO Input file, namely EQUATIONs, FORMULAs, READs, VARIABLEs, COEFFICIENTs, SETs and FILEs have been introduced in connection with equations House (E9) and Price_formation (E4) above

Each entity (VARIABLE, COEFFICIENT, etc) must be declared in the TABLO Input file before it is used in EQUATIONs and FORMULAs. This partly determines the order of the statements in the TABLO Input file.

We suggest that you now look at the complete TABLO Input file for this model, as set out in section 4.3.3 below, or using the editor TABmate (or your text editor). This file is usually called SJ.TAB when supplied with the GEMPACK Examples. You will find all the statements shown above in that file.

Since declarations must come before use, you will find the TABLO statements in pretty much the reverse order from that in which we have introduced them above.

We discuss the rest of this TABLO Input file in section 4.3.4.⁶

4.3.3    "Mixed" TABLO input file for the Stylized Johansen model [gpd1.3.3.3]

!-------------------------------------------------------------------! 
!                  Mixed TABLO Input file for the                   ! 
!                    Stylized Johansen model                        !
!                                                                   !
!         following the description in Chapter 3 of the text        ! 
!   "Notes and Problems in Applied General Equilibrium Economics"   ! 
!       by P.Dixon, B.Parmenter, A.Powell and P.Wilcoxen [DPPW]     ! 
!              published by North-Holland 1992.                     ! 
!                                                                   ! 
!-------------------------------------------------------------------!  
! Text between exclamation marks is a comment.                      ! 
! Text between hashes (#) is labelling information.                 !  
!-------------------------------------------------------------------! 
!     Set default values                                            ! 
!-------------------------------------------------------------------! 
VARIABLE (DEFAULT = LEVELS) ; 
EQUATION (DEFAULT = LEVELS) ; 
COEFFICIENT (DEFAULT = PARAMETER) ; 
FORMULA (DEFAULT = INITIAL) ;  

!-------------------------------------------------------------------! 
!      Sets                                                         ! 
!-------------------------------------------------------------------!  
! Index values i=1,2 in DPPW correspond to the sectors called s1,s2. 
  Index values i=3,4 in DPPW correspond to the primary factors, 
  labor and capital.   The set SECT below doubles as the set of  
  commodities  and the set of industries. !  
SET SECT # Sectors # (s1-s2)  ;  
SET FAC # Factors  # (labor, capital) ;  
SET NUM_SECT # Numeraire sector - sector 1 #  (s1) ;  
SUBSET  NUM_SECT is subset of SECT ;  

!-------------------------------------------------------------------! 
!      Levels variables                                             ! 
!-------------------------------------------------------------------!  
! In the DPPW names shown below, : denotes subscript.               ! 
! For example, x:j indicates that j is a subscript.                 ! 
VARIABLE               Y    # Total nominal household expenditure #
                              ! This is also Y in DPPW ! ; 
VARIABLE (all,i,SECT)  PC(i)   # Price of commodity i #
                                ! This is p:i (i=1,2) in DPPW ! ; 
VARIABLE (all,f,FAC)   PF(f)   # Price of factor f #
                                ! This is p:i (i=3,4) in DPPW ! ; 
VARIABLE (all,i,SECT)  XCOM(i)   ! This is x:i (i=1,2) in DPPW !
       # Total demand for (or supply of) commodity i # ;
VARIABLE (all,f,FAC)   XFAC(f)   ! This is x:i (i=3,4) in DPPW !
      # Total demand for (or supply of) factor f    # ; 
VARIABLE (all,i,SECT)  XH(i)   # Household demand for commodity i #
                                ! This is x:i0 (i=1,2) in DPPW ! ; 
VARIABLE (all,i,SECT) (all,j,SECT)     XC(i,j)
      # Intermediate inputs of commodity i to industry j #
     ! This is x:ij (i,j=1,2) in DPPW ! ; 
VARIABLE (all,f,FAC)(all,j,SECT)       XF(f,j)
      # Factor inputs to industry j #
     ! This is x:ij (i=3,4; j=1,2) in DPPW ! ;  

!-------------------------------------------------------------------! 
!     Dollar values read in from database                           ! 
!-------------------------------------------------------------------! 
VARIABLE (all,i,SECT)(all,j,SECT)      DVCOMIN(i,j)
      # Dollar value of inputs of commodity i to industry j # ; 
VARIABLE (all,f,FAC)(all,j,SECT)       DVFACIN(f,j)
     # Dollar value of factor f used in industry j # ; 
VARIABLE (all,i,SECT)                  DVHOUS(i)
      # Dollar value of household use of commodity i # ;  
!-------------------------------------------------------------------!
!     Parameters                                                    ! 
!-------------------------------------------------------------------! 
COEFFICIENT (all,i,SECT)(all,j,SECT)  ALPHACOM(i,j)
   # Share of intermediate use of commodity i in costs of industry j # ;
COEFFICIENT (all,f,FAC)(all,j,SECT)   ALPHAFAC(f,j)
   # Share of factor input f in costs of industry j # ;  
!-------------------------------------------------------------------! 
!      File                                                         ! 
!-------------------------------------------------------------------!  
FILE iodata # input-output data for the model # ;  

!-------------------------------------------------------------------! 
!      Reads from the data base                                     ! 
!-------------------------------------------------------------------!  
READ DVCOMIN from FILE iodata HEADER "CINP" ; 
READ DVFACIN from FILE iodata HEADER "FINP" ; 
READ DVHOUS  from FILE iodata HEADER "HCON" ; 

!-------------------------------------------------------------------!
!      Formulas                                                     ! 
!-------------------------------------------------------------------! 
FORMULA (all,i,SECT) PC(i) = 1.0 ; 
FORMULA (all,i,FAC) PF(i) = 1.0 ; 
FORMULA (all,i,SECT)(all,j,SECT) ALPHACOM(i,j) = DVCOMIN(i,j) /
            [SUM(ii,SECT,DVCOMIN(ii,j)) + SUM (ff,FAC,DVFACIN(ff,j))] ;
FORMULA (all,f,FAC)(all,j,SECT) ALPHAFAC(f,j) = DVFACIN(f,j) /
            [SUM(ii,SECT,DVCOMIN(ii,j)) + SUM (ff,FAC,DVFACIN(ff,j))] ;

! Formula to give initial value of Y !
FORMULA Y = SUM(i,SECT,DVHOUS(i)) ;

!-------------------------------------------------------------------! 
!       Formulas and levels equations                               ! 
!-------------------------------------------------------------------! 
FORMULA & EQUATION Comin
     # Intermediate input of commodity i to industry j #
   (all,i,SECT)(all,j,SECT) XC(i,j) = DVCOMIN(i,j) / PC(i) ;  
FORMULA & EQUATION Facin      # Factor input f to industry j #
 (all,f,FAC)(all,j,SECT) XF(f,j) = DVFACIN(f,j) / PF(f) ;
FORMULA & EQUATION House      # Household demand for commodity i #
 (all,i,SECT) XH(i) = DVHOUS(i) / PC(i) ;         
FORMULA & EQUATION Com_clear ! (E3.1.6) in DPPW !
    # Commodity market clearing #
 (all,i,SECT) XCOM(i) = XH(i) + SUM(j,SECT,XC(i,j)) ;  
FORMULA & EQUATION Factor_use ! (E3.1.7) in DPPW !
     # Aggregate primary factor usage #
 (all,f,FAC) XFAC(f) = SUM(j,SECT,XF(f,j)) ;  

!-------------------------------------------------------------------! 
!      Equations                                                    ! 
!-------------------------------------------------------------------! 
EQUATION(LINEAR)  Consumer_demands ! (E3.2.1) in DPPW !
     # Household expenditure functions #
 (all,i,SECT) p_XH(i) = p_Y - p_PC(i) ;
EQUATION(LINEAR)  Intermediate_com
! From (E3.2.2) with i=1,2 in DPPW. The term p_PC(j) is included
   because of (E3.2.3) in DPPW. !
    # Intermediate demands for commodity i by industry j #
(all,i,SECT)(all,j,SECT) p_XC(i,j) = p_XCOM(j) - (p_PC(i) - p_PC(j)) ;
EQUATION(LINEAR)  Factor_inputs
! From (E3.2.2) with i=3,4 in DPPW. The term p_PC(j) is included
   because of (E3.2.3) in DPPW. !
    # Factor input demand functions #
(all,f,FAC)(all,j,SECT) p_XF(f,j) = p_XCOM(j) - (p_PF(f) - p_PC(j)) ;
EQUATION(LINEAR) Price_formation   ! (E3.2.3) in DPPW !
     # Unit cost index for industry j #
 (all,j,SECT) p_PC(j) = SUM(i,SECT,ALPHACOM(i,j)*p_PC(i)) + 
                               SUM(f,FAC,ALPHAFAC(f,j)*p_PF(f)) ;
EQUATION Numeraire  ! (E3.1.23) in DPPW !
     # Price of commodity 1 is the numeraire #
 (all,i,NUM_SECT)  PC(i) = 1 ;
!--------------end of TABLO Input file------------------------------! 

4.3.4    Completing the TABLO input file for Stylized Johansen [gpd1.3.3.4]

Notice that the TABLO Input file consists of a number of statements, each beginning with its relevant keyword (such as SET or VARIABLE). Some statements include a qualifier such as (LINEAR) in EQUATION(LINEAR). Each statement ends with a semicolon ';'. Text between exclamation marks '!' is treated as a comment; such text can go anywhere in the TABLO Input file. Text between hashes '#' is labelling information; the positioning of this labelling information is restricted (see chapter 10 for full details).

The TABLO Input file is not case-sensitive so for example, XH and Xh would be identical so far as TABLO is concerned.

First come the DEFAULT statements. In TABLO Input files, EQUATIONs and VARIABLEs can be linear or levels. It is possible to distinguish each type by using the appropriate qualifier (LEVELS) or (LINEAR) after the keyword each time, as in, for example,

VARIABLE (LEVELS) Y # Nominal household expenditure # ; 
VARIABLE (LINEAR) (all,f,FAC) p_PF(f) # Price of factors # ; 

When most variables being declared are levels variables, it seems wasteful to have to keep repeating the qualifier (LEVELS). There are DEFAULT statements which allow you to reduce the number of qualifiers required in your TABLO Input files. If you put the statement

VARIABLE (DEFAULT = LEVELS) ;

early in a TABLO Input file, then, after it, any VARIABLE declaration is taken as the declaration of a levels variable unless a different qualifier (LINEAR) is present. Similarly for EQUATIONs coming after the statement

EQUATION (DEFAULT = LEVELS) ;

Of course, if most equations in your TABLO Input file are linearized ones, you could put the opposite default statement

EQUATION (DEFAULT = LINEAR) ;

near the start of your file, and then you would only have to flag, using the qualifier (LEVELS), the levels equations.

Similarly, the statements

COEFFICIENT (DEFAULT = PARAMETER) ; 
FORMULA (DEFAULT = INITIAL) ;

set the default types for COEFFICIENTs declared and FORMULAs. The only COEFFICIENTs in the TABLO Input file in section 4.3.3 above are parameters, while the only FORMULAs are used to set initial values (that is, pre-simulation values) of levels variables, or to set the values of the parameters. You will see non-parameter COEFFICIENTs and non-initial FORMULAs in section 4.4.1 below, when you look at linearized TABLO Input files.

Next come the declarations of the SETs, namely SECT (sectors) and FAC (primary factors). A further set NUM_SECT to stand for the single numeraire sector (sector s1) is also defined; this is only used for the last of the equations, the numeraire equation. The reason for the SUBSET statement will be explained when we discuss that equation below.

Then come the declarations of the VARIABLEs. Note that the arguments (if any) of each are clearly described, using the "(all,<index>,<set-name>)" quantifier(s) at the start of the declarations.

These quantifiers refer to the SETs, which is why the SET declarations must precede the VARIABLE declarations. The variables declared are all levels variables (because of the DEFAULT statement earlier). Although not explicitly mentioned here, the associated linear variables p_Y, p_XH etc are taken as automatically declared by convention, and can be used in subsequent EQUATIONs without further explicit declaration.

Then comes the declaration of the parameters - which must always be declared as COEFFICIENTs. The qualifier (PARAMETER) is not needed here because of the earlier DEFAULT(COEFFICIENT=PARAMETER) statement.

Next comes the declaration of the single data FILE required. This file is given the logical name 'iodata'. The actual name of the file on your computer containing this data is not limited by this logical name. You can give the actual file any convenient name. GEMSIM or the TABLO-generated program will prompt you for this actual name when you run it; the prompt will use the logical name 'iodata' from the TABLO Input file. Or, if you use a GEMPACK Command file (as we recommend), you will need to use the logical name as well as the actual name in the relevant statement (for example, "file iodata = SJ.HAR ;"). See section 22.1 for more details.

Then come READ statements telling the program to read in initial (that is, pre-simulation) values of certain levels variables. Each READ statement says from where the data is to be read (that is, which file and which header on the file).

Next come some FORMULAs assigning initial values to other levels variables. The left-hand side of a FORMULA (that is, the part before the '=' sign) must be a simple VARIABLE or COEFFICIENT, but the right-hand side can be a complicated expression. In such an expression, the symbols for the arithmetic operations are '+' and '-' for addition and subtraction, '*' and '/' for multiplication and division, and '^' for exponentiation. Note that '*' must be shown explicitly wherever multiplication is required. Notice also the use of the syntax

SUM(<index>,<set-name>, <expression to be summed> )

to express sums over sets.

Finally come the EQUATIONs (see (E1) to (E10) in section 4.1.1 above). As explained in section 4.3.2, some of these double as FORMULAs, in which case the statement must begin with FORMULA & EQUATION to indicate that there are really two statements here.

The syntax of the last equation (the numeraire equation) may surprise you. We could have expressed this as

PC("s1") = 1 ;

using the sector element name "s1" to indicate which price is fixed at one. Instead we have introduced the new set NUM_SECT consisting of just this sector "s1" and written the equation as

(all,i,NUM_SECT)  PC(i) = 1 ;

This illustrates the point of SUBSET declarations. The VARIABLE PC has been declared to have one argument ranging over the set SECT, but here we need to give it an argument ranging over the smaller set NUM_SECT. The earlier SUBSET statement

SUBSET  NUM_SECT  is subset of  SECT ;

alerts TABLO to the fact that an argument ranging over NUM_SECT is always in the set SECT. Without this, the use of PC(i) with i ranging over NUM_SECT would trigger a semantic error since TABLO checks that all arguments range over appropriate sets.

As stated earlier, the order of the statements in the TABLO Input file can be varied. For example, especially with larger models, some COEFFICIENTs may only be relevant to a small number of the EQUATIONs and it may be better to declare these and assign values to them just before the relevant EQUATION or group of EQUATIONs.

WRITE statements send the values of COEFFICIENTs (or levels VARIABLEs) to a file so you can examine them (or use them as a input to another program). Try this out by adding the following statements at the end of the TABLO Input file for Stylized Johansen and then re-running Steps 1, 2 and 3 in chapter 3.

File (new) Output;
Write ALPHACOM to file Output header "ACOM";
Write ALPHAFAC to file Output header "AFAC";

You'll also need to add into the CMF the line:

file Output = <cmf>out.har;

Complete documentation of TABLO Input files is given in chapters 8 to 18, which you will need to consult when you start to build a new model.

4.3.5    Change or percentage-change variables [gpd1.3.3.5]

Many levels variables (for example, prices, quantities, dollar values) are always positive and so it is natural for the associated linear VARIABLE to be a percentage change.

However, when the relevant levels variable can be positive or zero or negative (examples are the Balance of Trade and an ad valorem tax rate), it is wiser to specify that the associated linear VARIABLE is an ordinary change. This is because, in such a case, if the levels value happens to be zero at the start of any step of a multi-step simulation, the associated percentage change could not be calculated (since it would require division by zero). Also, there are often numerical problems (which slow or hinder convergence of the solutions) when a percentage-change variable changes sign in the levels; these problems may be overcome if an ordinary change variable is used because then TABLO works with a slightly different linearization of the EQUATIONs involving this VARIABLE.⁷ In summary, we suggest the following guidelines.

• For levels variables which are always positive (or always negative), work with the associated percentage change as a linear VARIABLE.
• For levels variables which may change sign, declare the associated linear VARIABLE to be an ordinary change. In this case, when declaring the levels variable, insert the qualifier (CHANGE) after the keyword VARIABLE.

The (CHANGE) qualifier tells TABLO to automatically declare the associated linear variable as an ordinary change (the prefix "c_" is usually added to the levels name).⁸ For example, if you have a declaration

VARIABLE (CHANGE) BT  # Balance of trade # ;

in your TABLO Input file, the associated change linear variable c_BT is automatically available for use in linearized equations and will be used in reporting simulation results. Alternatively a linear change variable can be declared directly, using the two qualifiers LINEAR and CHANGE as in.

VARIABLE (LINEAR,CHANGE) delB  # Change in trade balance # ;

(When you declare a linear change variable explicitly, you are not required to begin the name with "c_".)

4.3.6    Variable or parameter ? [gpd1.3.3.6]

When you build a model, you have in mind the sorts of questions you will be using the model to answer. You may be thinking of holding some quantities constant and varying others.

Within GEMPACK, the quantities you may wish to vary will be declared as VARIABLEs while those which cannot vary can be declared as COEFFICIENT(PARAMETER)s.

Traditionally GEMPACK users declare as VARIABLEs (rather than as parameters) any quantity which might conceivably vary.⁹ For example, you may have a model which includes tax rates which you do not (at present) intend to vary. You could declare them as COEFFICIENT(PARAMETER)s but it may be more useful to declare them as VARIABLEs. In the latter case, you can convey the fact that they do not vary by indicating that the VARIABLEs are exogenous and not shocked.¹⁰ Later, if you wish to model the consequences of these tax rates changing, you do not have to change the model.

In Stylized Johansen, there are only two exogenous variables, the supplies of the primary factors labor and capital, so this issue does not arise. However, it does arise in most of the more serious models implemented via GEMPACK. For example, in ORANI-G (see section 60.5), many quantities which do not change in most simulations (for example, household subsistence demands, various technology terms and various shifters) are declared as Variables rather than as Parameters.

4.3.7    TABLO language - syntax and semantics [gpd1.3.3.7]

Full details of the syntax and semantics used in TABLO Input files are given in chapters 10 to 11. The description there applies to all TABLO Input files - that is, to those containing just levels equations, just linearized ones and to those (such as the one in section 4.3.3 above) containing a mixture of levels and linearized equations. We will introduce more information about the syntax and semantics in sections 4.4 and 4.5 below (where we describe alternative TABLO Input files for Stylized Johansen, firstly one containing just linearized equations and secondly one containing just levels equations).

4.4    Linearized TABLO input files [gpd1.3.4]

The majority of the more well-known models implemented in GEMPACK use a TABLO Input file containing only linearized equations; we refer to such TABLO Input files as linearized TABLO Input files.

We illustrate this by giving in full in section 4.4.1 below such a TABLO Input file for Stylized Johansen. This file is usually called SJLN.TAB when supplied with the GEMPACK Example files.

In comparison with the mixed TABLO Input file for Stylized Johansen in section 4.3.3 above, the main differences to note are as follows.

• The linear VARIABLEs are declared explicitly.
• The levels variables do not seem to be present. But in fact, in a linearized TABLO Input file, many of these are declared as COEFFICIENTs. Thus, in TABLO Input files, COEFFICIENTs have two functions:
  1. They can denote the (pre-simulation) values of a levels variable.
  2. They can denote parameters.
• In a linearized TABLO Input file, the requirement that an initial solution be obtainable from the data base means that the values of all COEFFICIENTs occurring in the linearized EQUATIONs must have their values defined (via READs or FORMULAs).
• It is necessary to provide UPDATE statements to tell how the data read from the data base changes in response to small changes in the relevant linear VARIABLEs. (It helps to think in terms of a multi-step simulation as described in section 3.12.3 above. After each step, the data base has to be updated to take into account changes in all the linear VARIABLEs over the step.) We give a more detailed discussion of UPDATE statements in section 4.4.4 below. One role of UPDATE statements is to provide the link between the linear VARIABLEs and the COEFFICIENTs (that is, levels variables).

We give the full TABLO Input file in section 4.4.1 and then discuss noteworthy features of it in section 4.4.2 below.

Advice about linearizing equations by hand can be found in section 18.2.

4.4.1    A linearized TABLO input file for Stylized Johansen [gpd1.3.4.1]

!-------------------------------------------------------------------!
!               Linearized TABLO Input file for the                 !
!                       Stylized Johansen model                     !
!           following the description in Chapter 3 of the text      !
!    "Notes and Problems in Applied General Equilibrium Economics"  !
!       by P.Dixon, B.Parmenter, A.Powell and P.Wilcoxen [DPPW]     !
!                published by North-Holland 1992.                   !
!-------------------------------------------------------------------!
! Text between exclamation marks is a comment.                      !                        
! Text between hashes (#) is labelling information.                 !
!-------------------------------------------------------------------!
!      Sets                                                         !
!-------------------------------------------------------------------!
! Index values i=1,2 in DPPW correspond to the sectors called s1,s2.
  Index values i=3,4 in DPPW correspond to the primary factors, labor 
  and capital.   The set SECT below doubles as the set of 
  commodities  and the set of industries. !
SET
 SECT # Sectors # (s1-s2)  ;
 FAC # Factors  # (labor, capital) ;
 NUM_SECT # Numeraire sector - sector 1 #  (s1) ;
SUBSET  NUM_SECT is subset of SECT ;
!-------------------------------------------------------------------!
!  File                                                             !
!-------------------------------------------------------------------!
 FILE iodata # the input-output data for the model # ;
!-------------------------------------------------------------------!
VARIABLE ! All variables are percent changes in relevant levels quantities !
!  In the DPPW names shown below,  : denotes subscript.             !
!  Thus, for example,   x:j indicates that j is a subscript.        !
 (ORIG_LEVEL=Y) p_Y  # Total household expenditure [DPPW y]#; 
 (ORIG_LEVEL=1) (all,i,SECT) p_PC(i) 
     # Price of commodities [DPPW p:i (i=1,2)]#;
 (ORIG_LEVEL=1) (all,f,FAC) p_PF(f)  
     # Price of factors [DPPW p:i  (i=3,4)]#;
 (ORIG_LEVEL=DVCOM) (all,i,SECT) p_XCOM(i)  
     # Total demand for (or supply of) commodities [DPPW x:i (i=1,2)]#;
 (ORIG_LEVEL=DVFAC) (all,f,FAC) p_XFAC(f)  
     # Total demand for (or supply of) factors [DPPW x:i  (i=3,4)]#;
 (ORIG_LEVEL=DVHOUS) (all,i,SECT) p_XH(i)  
     # Household consumption of commodities [DPPW x:i0  (i=1,2)]#;
 (ORIG_LEVEL=DVCOMIN) (all,i,SECT)(all,j,SECT) p_XC(i,j)  
     # Intermediate commodity inputs [DPPW x:ij  (i,j=1,2)]#;
 (ORIG_LEVEL=DVFACIN) (all,f,FAC)(all,j,SECT) p_XF(f,j)  
     # Intermediate factor inputs [DPPW x:ij  (i=3,4; j=1,2)]#;

!-------------------------------------------------------------------!
!  Base data, updates and reads                                     !
!   (Base data is as in Table E3.3.1 of DPPW)                       !
!-------------------------------------------------------------------!
 COEFFICIENT (GE 0)  (all,i,SECT)(all,j,SECT) DVCOMIN(i,j)  
   # Dollar value of inputs of commodity i to industry j # ;
 UPDATE (all,i,SECT)(all,j,SECT) DVCOMIN(i,j) = p_PC(i)*p_XC(i,j) ;

 COEFFICIENT (GE 0)  (all,f,FAC)(all,j,SECT)  DVFACIN(f,j)  
   # Dollar value of inputs of factor f to industry j # ;
 UPDATE (all,f,FAC)(all,j,SECT)  DVFACIN(f,j) = p_PF(f)*p_XF(f,j) ;

 COEFFICIENT (GE 0)  (all,i,SECT) DVHOUS(i)  
   # Dollar value of household use of commodity i # ;
 UPDATE (all,i,SECT)             DVHOUS(i) = p_PC(i)*p_XH(i) ;

!-------------------------------------------------------------------!
!  Reads from the data base                                         !
!-------------------------------------------------------------------!
 READ DVCOMIN FROM FILE iodata HEADER "CINP" ;
 READ DVFACIN FROM FILE iodata HEADER "FINP" ;
 READ DVHOUS  FROM FILE iodata HEADER "HCON" ;

!-------------------------------------------------------------------!
!  Other coefficients and formulas for them                         !
!-------------------------------------------------------------------!
 COEFFICIENT  Y    # Total nominal household expenditure # ;
 FORMULA Y = SUM(i,SECT,DVHOUS(i)) ;

 COEFFICIENT (all,i,SECT) DVCOM(i) # Value of total demand for commodity i # ;
 FORMULA     (all,i,SECT) DVCOM(i) = SUM(j,SECT, DVCOMIN(i,j)) + DVHOUS(i) ;
 
 COEFFICIENT (all,f,FAC) DVFAC(f) # Value of total demand for factor f # ;
 FORMULA     (all,f,FAC) DVFAC(f) =  SUM(j,SECT,DVFACIN(f,j)) ;

 COEFFICIENT(PARAMETER)   (all,i,SECT)(all,j,SECT) ALPHACOM(i,j)  
   # alpha(i,j) - commodity parameter in Cobb-Douglas production function # ;
   ! = initial share of commodity i in total inputs to industry j  
     This is  alpha:ij  (i=1,2; j=1,2) in (E3.1.4) of DPPW ! 
 FORMULA(INITIAL)(all,i,SECT)(all,j,SECT) ALPHACOM(i,j) = DVCOMIN(i,j)/DVCOM(j);
 
COEFFICIENT(PARAMETER)   (all,f,FAC)(all,j,SECT) ALPHAFAC(f,j)  
   # alpha(f,j) - factor parameter in Cobb-Douglas production function. #;
   ! = initial share of factor f in total inputs to industry j  
     This is  alpha:ij  (i=3,4; j=1,2) in (E3.1.4) of DPPW !  
 FORMULA(INITIAL)(all,f,FAC)(all,j,SECT) ALPHAFAC(f,j) = DVFACIN(f,j)/DVCOM(j);

 COEFFICIENT   (all,i,SECT)(all,j,SECT) BCOM(i,j)  
   # beta(i,j) - share of industry j in total demand for commodity i # ; 
   ! This is  beta:ij  (i=1,2; j=1,2) in (E3.2.4) of DPPW !  
 FORMULA   (all,i,SECT)(all,j,SECT) BCOM(i,j) = DVCOMIN(i,j)/DVCOM(i) ;

 COEFFICIENT   (all,i,SECT)  BHOUS(i)  
   # beta(i,0) - share of households in total demand for commodity i # ; 
   ! This is  beta:i0  (i=1,2) in (E3.2.4) of DPPW !  
 FORMULA   (all,i,SECT) BHOUS(i) = DVHOUS(i)/DVCOM(i) ;

 COEFFICIENT   (all,f,FAC)(all,j,SECT) BFAC(f,j)  
   # beta(f,j) - share of industry j in total demand for factor f #; 
   ! This is  beta:ij  (i=3,4; j=1,2) in (E3.2.5) of DPPW !  
 FORMULA   (all,f,FAC)(all,j,SECT) BFAC(f,j) = DVFACIN(f,j)/DVFAC(f) ;

!-------------------------------------------------------------------!
!  Equations (Linearized)                                           !
!-------------------------------------------------------------------!
EQUATION  Consumer_demands # Household expenditure functions [DPPW E3.2.1]# 
(all,i,SECT) p_XH(i) = p_Y - p_PC(i) ;

EQUATION  Intermediate_com # Intermediate demands [DPPW E3.2.2 i=1,2]#
! The term p_PC(j) is included because of (E3.2.3) in DPPW. !
(all,i,SECT)(all,j,SECT) p_XC(i,j) = p_XCOM(j) - (p_PC(i) - p_PC(j)) ;

EQUATION  Factor_inputs # Factor input demand functions [DPPW E3.2.2 i=3,4]#
! The term p_PC(j) is included because of (E3.2.3) in DPPW. !
(all,f,FAC)(all,j,SECT) p_XF(f,j) = p_XCOM(j) - (p_PF(f) - p_PC(j)) ;

EQUATION  Price_formation  # Unit cost index for industry j [DPPW E3.2.3]#
    (all,j,SECT) p_PC(j) = SUM(i,SECT,ALPHACOM(i,j)*p_PC(i)) +
                           SUM(f,FAC,ALPHAFAC(f,j)*p_PF(f)) ;

EQUATION Com_clear # Commodity market clearing [DPPW E3.2.4]#
   (all,i,SECT) p_XCOM(i) = BHOUS(i)*p_XH(i) + SUM(j,SECT,BCOM(i,j)*p_XC(i,j)); 
 
EQUATION Factor_use # Aggregate primary factor usage [E3.2.5 in DPPW]#
   (all,f,FAC) p_XFAC(f) = SUM(j,SECT,BFAC(f,j)*p_XF(f,j)) ; 
 
EQUATION NUMERAIRE # Numeraire is price of commodity 1 [DPPW E3.2.6]#
   (all,i,NUM_SECT)  p_PC(i) = 0; 
   ! Alternatively, this could be written as   p_PC( "s1" ) = 0 !

!-------------------------------------------------------------------!
!      Balance check for data base                                  !
!-------------------------------------------------------------------!
! In a balanced data base, total demand for commodity i, DVCOM(i) 
   should equal DVCOST(i), the total cost of inputs to industry i !
![[!
! To check that total demand = total costs to industry i
   remove the strong comment markers ![[! ... !]]! around  this section   !
COEFFICIENT (all,i,SECT) DVCOST(i) # Total cost of inputs to industry i# ;
 FORMULA   (all,i,SECT)
     DVCOST(i) = SUM(u,SECT,DVCOMIN(u,i)) + SUM(f,FAC,DVFACIN(f,i)) ;
  ! Check that the values  of DVCOM and DVCOST are equal !
  DISPLAY DVCOM ;
  DISPLAY DVCOST ; !]]! 
!---------end of TABLO Input file--------------------------------------!

4.4.2    Noteworthy features in the linearized TABLO input file [gpd1.3.4.2]

1. DEFAULT statements

Notice that there are no DEFAULT statements at the start of the linearized file in section 4.4.1. This is because of the convention that all TABLO Input files are assumed to begin with defaults appropriate for linearized TABLO Input files¹¹, namely as if there were the following statements at the start.

VARIABLE (DEFAULT = LINEAR) ; 
EQUATION (DEFAULT = LINEAR) ; 
VARIABLE (DEFAULT = PERCENT_CHANGE) ; 
COEFFICIENT (DEFAULT = NON_PARAMETER) ; 
FORMULA (DEFAULT = ALWAYS) ;  

The purpose of the last of these is discussed under the heading "FORMULAs" below.

2. VARIABLEs

The linear variables are declared explicitly. We have chosen to use the same names as are declared implicitly in the mixed TABLO Input file in section 4.3.3 above. (This makes results from the 2 files easier to compare.) But we could have chosen different names.

The (ORIG_LEVEL=...) qualifiers tell the software what to take as the pre-simulation values for the various levels variables. For example,

VARIABLE  (ORIG_LEVEL=Y)  p_Y  # Total nominal household expenditure # ;

indicates that the pre-simulation levels value of the variable p_Y is Y. Without this ORIG_LEVEL qualifier, you would not see the pre-simulation, post-simulation and changes results in Table 3.3 above when you run a simulation. Similarly

VARIABLE  (ORIG_LEVEL=1)  (all,i,SECT)  p_PC(i) # Price of commodities # ;

tells the software that it can take 1 as the pre-simulation levels values of the PC(i) for each commodity i. Starting with these prices equal to one explains why it is sensible to take the pre-simulation values of the supplies XCOM(i) to be equal to the pre-simulation dollar values DVCOM(i), as indicated in

VARIABLE  (ORIG_LEVEL=DVCOM)  (all,i,SECT)  p_XCOM(i) #...# ;

These ORIG_LEVEL qualifiers are not necessary in the mixed TABLO Input file SJ.TAB shown in section 4.3.3 above since there the linear variable p_Y is derived automatically from Y via the declaration of the levels variable Y, so the software knows the connection between Y and p_Y. [See section 10.4 for documentation about the ORIG_LEVEL qualifier.]

3. COEFFICIENTs

Many of the levels quantities which were declared as levels variables in the mixed TABLO Input file in section 4.3.3 are declared here as COEFFICIENTs. (For example, the dollar values DVHOUS and DVCOM. The first is READ from the data base and the second has its values assigned via a FORMULA.)

It may help to think of these COEFFICIENTs as holding pre-simulation values of the levels variables. However this is not entirely accurate in a multi-step simulation as we see below in the discussion of FORMULAs and UPDATEs.

4. FORMULAs

Most of the FORMULAs in the linearized file are re-evaluated at each step of a multi-step simulation. This is what the qualifier (ALWAYS) denotes in the DEFAULT statement shown in (1.) above. After each step of a multi-step simulation, the data base is updated and all FORMULA(ALWAYS)s are re-evaluated. For example, this ensures that DVCOM is always an accurate reflection of the DVCOMIN and DVHOUS values on the currently updated data base. [A numerical example is in section 4.4.7.]

However some FORMULAs, those with qualifier (INITIAL), are only evaluated on the first step of a multi-step simulation. FORMULAs giving the value of parameters (such as those for ALPHACOM and ALPHAFAC) should only be applied initially (that is, at the first step) since the value of a parameter should not be changed.

5. UPDATEs

The purpose of an UPDATE statement is to tell the software how a COEFFICIENT (that is, a levels variable) changes in response to the small changes in the linear VARIABLEs at each step of a multi-step simulation.

For example, consider DVHOUS(i), the dollar value of household consumption of commodity i.

(a) Suppose there were an explicit linear VARIABLE, say p_DVHOUS(i), declared giving the percentage change in DVHOUS(i). (In fact there is no such VARIABLE in the linearized TABLO Input file.) Then, in response to a change in this, the new value of DVHOUS(i) should be given by

new_DVHOUS(i) = old_DVHOUS(i)*[1 + p_DVHOUS(i)/100]

(On any step, the old value is the value before the step and the new value is the one put on the data base updated after the step.) We would need an UPDATE statement to indicate this. The statement could be

UPDATE (all,i,SECT) DVHOUS(i) = p_DVHOUS(i) ; .

(b) In fact there is no linear VARIABLE declared in the linearized TABLO Input file giving the percentage change in DVHOUS(i). However there are explicit linear VARIABLEs p_PC(i) and p_XH(i) showing the percentage changes in the relevant price and quantity. If p_DVHOUS(i) were declared, there would be a linear EQUATION connecting it to p_PC(i) and p_XH(i). This EQUATION would say that

p_DVHOUS(i) = p_PC(i) + p_XH(i)

Thus, the procedure for updating DVHOUS(i) is

new_DVHOUS(i) = old_DVHOUS(i)*[1 + {p_PC(i)+p_XH(i)}/100]

In fact the UPDATE statement is

UPDATE (all,i,SECT) DVHOUS(i) = p_PC(i) * p_XH(i) ;

This is interpreted by TABLO as having the correct effect (see section 4.4.6 for a numerical example). At first you may be puzzled by the multiplication sign "*" here since the percentage change in DVHOUS(i) is the SUM of p_PC(i) and p_XH(i). However, this form of UPDATE is called a PRODUCT UPDATE because it is used to update a COEFFICIENT (that is, a levels variable) which is the product of 2 or more levels variables whose percentage changes are explicit linear VARIABLEs. Here, in the levels,

DVHOUS(i) = PC(i) * XH(i)

and the "*" used in a PRODUCT UPDATE is to remind you of this levels¹² formula.

6. Levels Prices and Quantities not Needed

Notice that no COEFFICIENTs have been declared to hold the levels values of prices or quantities. [For example, there is no COEFFICIENT XH(i) even though there is a VARIABLE p_XH(i).] This is a fairly common feature of linearized TABLO Input files. In such files,

• normally linear VARIABLEs are declared to show percentage changes (or changes) in prices and quantities, but no explicit linear VARIABLEs are declared to show percentage changes in dollar values.
• COEFFICIENTs holding levels dollar values are declared but there are not normally COEFFICIENTs holding levels prices or quantities.

7. Names for Levels and Linearized VARIABLEs

As you have seen above, the levels variables required in a linearized TABLO Input file appear as COEFFICIENTs while the percentage-change (or change) variables required appear as linear VARIABLEs.

It may happen that you need on the TABLO Input file a levels variable as a COEFFICIENT and its percentage change (or change) as a VARIABLE. In this case, since TABLO Input files are not case-sensitive, you cannot follow the convention of using upper case for the levels variables or COEFFICIENTs (for example, XHOUS) and the same name partly or wholly in lower case for the associated linear VARIABLEs (for example, xhous). The problem is most likely to occur for values, which often occur both as COEFFICIENTs and VARIABLEs.

We suggest 3 alternative ways around this problem.

1: Follow a convention that value coefficients start with "V", while the associated percentage change variable begins with "w".For example,

COEFFICIENT  VHOUTOT       VARIABLE  whoutot

2: Use the natural name for the COEFFICIENT version and attach 'p_' (for percentage change) or 'c_' (for change) at the start for the VARIABLE. For example,

COEFFICIENT  XHOUS(i)      VARIABLE  p_XHOUS(i)

3: Use the natural name for the VARIABLE version and attach '_L' (for levels) to the end for the COEFFICIENT. For example,

VARIABLE  xhous(i)         COEFFICIENT  XHOUS_L(i).

Although TABLO Input files are not case-sensitive (meaning that xhous and XHOUS are treated as being the same), we find it makes linearized TABLO Input files more readable if we consistently put linear VARIABLE names in lower case, or consistently put the first letter of all linear VARIABLE names in lower case and the rest in upper case.

4.4.3    Analysing simulation results [gpd1.3.4.3]

Now that you understand about TABLO Input files, you will want to begin learning how to analyse simulation results, ie, to explain them using the equations of the model (as in the TABLO Input file), and the base data.

In section 46.1 you can find a detailed hands-on analysis, using the AnalyseGE program, of the 10 percent labor increase simulation with Stylized Johansen (based on the linear TABLO Input file SJLN.TAB in section 4.4.1 above).

4.4.4    Writing UPDATE statements [gpd1.3.4.4]

The purpose of an UPDATE statement is to tell how much some part of data read changes in response to changes in the model's variables in the current step of a multi-step simulation. An introductory example was given in section 4.4.2 above.

Consider a COEFFICIENT V whose value(s) are read. There are three possibilities for the UPDATE statement for V.

1. If there is a linear VARIABLE, say w, in the TABLO Input file which represents the percentage change in V, then use an UPDATE statement of the form

UPDATE V = w ;

2. If, in the levels, V is equal to the product of two or more percentage-change variables, say p and q, use an UPDATE statement of the form

UPDATE V = p*q ;

This type of UPDATE statement is referred to as a PRODUCT UPDATE since it involves updating a Levels variable which is a product of other Levels quantities (often a value V is, in levels, the product of price P and quantity Q).

3. Otherwise work out an expression for the change in V in terms of linear VARIABLEs in the TABLO Input file and use a CHANGE UPDATE statement of the form

UPDATE (CHANGE)  V = <expression for change in V> ;

Of these, the second case is by far the most common and probably will cover over 90% of your UPDATE statements.¹³ All three UPDATE statements in the linearized TABLO Input file for Stylized Johansen are of this form (see section 4.4.1 above). Of course if COEFFICIENT V has one or more arguments, the UPDATE statements also contain the appropriate quantifiers, for example (all,i,SECT). Note also that only COEFFICIENTs whose values are READ or assigned via a FORMULA(INITIAL) in the TABLO Input file should be UPDATEd.

In case 3 above, the expression for the change in V is obtained by linearizing the levels equation connecting V to other levels variables whose associated linear variables have been declared in the TABLO Input file. See section 11.12.7 for a worked example.

More details about Updates, including examples, can be found in section 11.12.

4.4.5    Numerical versions of linearized equations [gpd1.3.4.5]

In this section we look at numerical versions of the linearized equations in SJLN.TAB. In two subsections below, we look at the numerical consequences of Update statements in SJLB.TAB (section 4.4.6) and at how the values of the Coefficients and the numerical equations are recalculated during each step of a multi-step calculation (section 4.4.7).

Some users are keen to have detailed information about these topics; others are not. Since a detailed knowledge about these topics is not essential for doing effective modelling, you should feel free to skip these sections. You can always refer back to them later on, if necessary.

Here we look at the numerical version of the linearized equation for market clearing of commodities Com_clear. The equation is

Equation Com_clear   (all,i,SECT) 
   p_XCOM(i) = BHOUS(i)*p_XH(i) + SUM(j,SECT,BCOM(i,j)*p_XC(i,j)) ;

There are really 2 equations here, one for each sector ("s1", "s2"). The BHOUS and BCOM Coefficients are shares. When evaluated at the base data values (see Table 3.1 above), they have the values

At the start of the simulation (ie, on the first Euler step — see section 3.12.3 above), the two equations are

This is why we call BHOUS and BCOM coefficients since their values are what are usually called the coefficients in the above equations¹⁴. The unknowns p_XCOM("s1"), p_XH("s1"), p_XC("s1","s1") and p_XC("s1","s2") are the Variables in the first of these equations.

When GEMPACK solves the equations above, all the variables are put onto one side so that the equation says that some expression is equal to zero. The equations above are rewritten as

If you look at Table 3.4 above which represents the Equations Matrix for the linearized system, the equation Com_clear("s1") is one row of the Equations matrix. The coefficients of variable p_XH("s1") give the column for p_XH("s1") in the Equations matrix so that

• you can see that the number -0.25 goes in the Com_clear("s1") row and the p_XH("s1") column [from the second term in the first equation].
• The number 1.0 goes in the Com_clear("s2") row and the p_XCOM("s2") column [the first term in the second equation].
• and similarly for the other terms in the equations.

4.4.6    Numerical examples of update statements [gpd1.3.4.6]

Here we consider the 4-step Euler calculation with Stylized Johansen in which the supply of labor is increased by 10 percent (and the supply of capital is fixed).

We look at the effect of the Update statements after the first step of this 4-step calculation.

During the first step, the supply of labor is only increased by 2.5 percent (one quarter of the total shock). The software solves the linear equations (those in section 4.4.5 above) to work out the consequential changes in the other quantities and prices. Some results from solving these equations are as follows:

The Update statement for DVHOUS(i) is

UPDATE  (all,i,SECT)  DVHOUS(i) = p_PC(i) * p_XH(i) ;

which means (see point 5. in section 4.4.2 above) that

new_DVHOUS(i) = old_DVHOUS(i)*[1 + {p_PC(i)+p_XH(i)}/100] .

Hence the updated values for DVHOUS after the first step are

DVHOUS("s1") = 2*[1+{0+1.5}/100] = 2*1.015 = 2.03

DVHOUS("s2") = 4*[1+{-0.25+1.75}/100] = 4*1.015 = 4.06

Similarly the other percentage changes in prices and quantities during this first step are used to update the values of the other Coefficients DVCOMIN(i,j) and DVFACIN(f,j) which are read from the data base.¹⁵

4.4.7    How equations are recalculated in a multi-step calculation [gpd1.3.4.7]

As we indicated in section 3.12.1 above, the values of the Coefficients may change from step to step of a multi-step calculation.

Here we look at this for the second step of the 4-step Euler calculation discussed in section 4.4.6 above.

The values of all Coefficients read from the data base are updated at the end of the first step of this calculation. During the second step, these Coefficients take these updated values.

The values taken during step 2 of all other Coefficients which are not Coefficient(Parameter)s are inferred from the relevant Formulas.¹⁶ For example, the DVCOM(i) values during step 2 are calculated by applying the TABLO Input file

FORMULA (all,i,SECT) DVCOM(i) = SUM(j,SECT, DVCOMIN(i,j)) + DVHOUS(i);

The updated values for DVHOUS (see section 4.4.6 above) and DVCOMIN are put into the right-hand side of this Formula to give the values for DVHOUS(i) used during the second step. Similarly for all other Coefficients.

Thus, for example, the values of the BHOUS(i) are recalculated during this second step. These recalculated values are put into the relevant equations (namely the Com_clear equations).

Hence the numerical linear equations solved during step 2 may be different from those solved during step 1.

In fact, for the Stylized Johansen model, the Coefficients BHOUS, BCOM and BFAC, which look as if they may change from step to step, do not change.¹⁷ This behaviour (which is not typical of GE models) is a consequence of the fact that all behaviour in Stylized Johansen is Cobb-Douglas.

More details about the values used and calculated during the different steps of this 4-step calculation can be found in section 25.2.2.

4.5    Levels TABLO input files [gpd1.3.5]

We illustrate the construction of TABLO Input files containing only levels equations by looking at such a file for Stylized Johansen in section 4.5.1. The main difference in general from mixed TABLO Input files is in connection with behavioural equations (such as CES specifications). You should expect the levels files to contain explicit calibration FORMULAs of the kind familiar to levels modellers for calculating the values of the parameters of these functions.

A surprise with the Cobb-Douglas specification in Stylized Johansen is that, although such parameters appear in the levels equations, we do not need to calculate their values since these parameters do not appear in the linearized equations produced by TABLO. But this would not be the case if Cobb-Douglas were replaced by CES.

4.5.1    Levels TABLO input file for Stylized Johansen [gpd1.3.5.1]

The main difference from the mixed TABLO Input file shown in section 4.3.3 comes from using the levels version of the behavioural equations (the first three blocks in Table 4.1. These involve two parameters not present in the linearized versions of these equations, namely

These are called ALPHAH(i) and Q(j) respectively in the levels TABLO Input file given later in this section. As part of the calibration phase, you would expect to have to give FORMULAs for calculating the values of these. For example, using the TABLO Input file notation,

ALPHAH(i) = PC(i)*XH(i)/Y = DVHOUS(i)/SUM(ii,SECT,DVHOUS(ii))

and it would also be possible to write down a formula for the Q(j). However, in GEMPACK, the levels equations are only used as a means of writing down the linearized equations (TABLO does this by symbolically differentiating the levels equations — see section 4.6 below). Once this has been done, the levels equations are ignored. Thus, since the linearized versions of these equations no longer involve these ALPHAH and Q parameters, it is not necessary to give FORMULAs for them.¹⁸ Of course, in a more complicated model, you may not be sure if similar parameters are going to appear in the linearized system. When in doubt, you can write down the TABLO Input file leaving out calibration FORMULAs for such parameters and process the file by running TABLO. If the values are needed in the linearized system, TABLO will tell you and not allow you to proceed until you have supplied calibration FORMULAs.

Another noteworthy feature of the levels TABLO file shown below is in the EQUATION E_W for the quantity called W(j) there. Variable W(j) has been introduced to simplify the "intermediate demands" and "price formation" equations. The equation E_W uses the PROD operator to express W(j) as the product of the relevant quantities.¹⁹ The full levels TABLO Input file is shown below.

.!-------------------------------------------------------------------!
!                   Levels TABLO Input File for the                 !
!                      Stylized Johansen Model                      !
!                                                                   !
!      following the description in Chapter 3 of the text           !
!   "Notes and Problems in Applied General Equilibrium Economics"   !
!     by P.Dixon, B.Parmenter, A.Powell and P.Wilcoxen [DPPW]       !
!             published by North-Holland 1992                       !
!-------------------------------------------------------------------!

!   Text between exclamation marks is a comment                     !
!   Text between hashes (#) is labelling information                !

!-------------------------------------------------------------------!
!    Set defaults for Levels model                                  !
!-------------------------------------------------------------------!
EQUATION(DEFAULT=LEVELS) ;
VARIABLE(DEFAULT=LEVELS) ;
FORMULA(DEFAULT=INITIAL) ;
COEFFICIENT(DEFAULT=PARAMETER) ;

!-------------------------------------------------------------------!
!      Sets                                                         !
!-------------------------------------------------------------------!
! Index values i=1,2 in DPPW correspond to the sectors called s1,s2.
  Index values i=3,4 in DPPW correspond to the primary factors,
  labor and capital.   The set SECT below doubles as the set of 
  commodities  and the set of industries. !

SET SECT # Sectors # (s1-s2)  ;
SET FAC # Factors  # (labor, capital) ;

!-------------------------------------------------------------------!
!      Levels variables                                             !
!-------------------------------------------------------------------!
! In the DPPW names shown below, : denotes subscript.               !
! For example, x:j indicates that j is a subscript.                 !

Variable (GE 0)        Y    # Total nominal household expenditure # 
                            ! This is also Y in DPPW ! ;

Variable (GE 0) (all,i,SECT)  PC(i)   # Price of commodity i #
                               ! This is p:i (i=1,2) in DPPW ! ;
Variable (GE 0) (all,f,FAC)   PF(f)   # Price of factor f #
                               ! This is p:i (i=3,4) in DPPW ! ;
Variable (GE 0) (all,i,SECT)  XCOM(i) 
    # Total demand for (or supply of) commodity i #
                               ! This is x:i (i=1,2) in DPPW ! ;
Variable (GE 0) (all,f,FAC)   XFAC(f) 
    # Total demand for (or supply of) factor f    #
                               ! This is x:i (i=3,4) in DPPW ! ;

Variable (GE 0) (all,i,SECT)  XH(i)   # Household demand for commodity i #
                               ! This is x:i0 (i=1,2) in DPPW ! ;
Variable (GE 0) (all,i,SECT) (all,j,SECT)     XC(i,j) 
    # Intermediate inputs of commodity i to industry j #
    ! This is x:ij (i,j=1,2) in DPPW ! ;
Variable (GE 0) (all,f,FAC)(all,j,SECT)       XF(f,j) 
    # Factor inputs to industry j #
    ! This is x:ij (i=3,4; j=1,2) in DPPW ! ;
Variable (all,j,SECT)  W(j)    #Price expression#;

!-------------------------------------------------------------------!
!     Dollar values read in from database                           !
!-------------------------------------------------------------------!
Variable (GE 0) (all,i,SECT)(all,j,SECT)      DVCOMIN(i,j) 
    # Dollar value of inputs of commodity i to industry j # ;
Variable (GE 0) (all,f,FAC)(all,j,SECT)       DVFACIN(f,j)
    # Dollar value of factor f used in industry j # ;
Variable (GE 0) (all,i,SECT)                  DVHOUS(i) 
    # Dollar value of household use of commodity i # ;

!-------------------------------------------------------------------!
!     Parameters                                                    !
!-------------------------------------------------------------------!
COEFFICIENT (all,i,SECT)   ALPHAH(i)     #Household parameter#;
COEFFICIENT
 (all,i,SECT) (all,j,SECT) ALPHACOM(i,j) #Commodity parameter#;
COEFFICIENT
 (all,f,FAC) (all,j,SECT)  ALPHAFAC(f,j) #Factor parameter#;
COEFFICIENT (all,j,SECT)   Q(j)          #Scale parameter#;

!-------------------------------------------------------------------!
!      File                                                         !
!-------------------------------------------------------------------!
FILE iodata # input-output data for the model # ;

!-------------------------------------------------------------------!
!      Reads from the data base                                     !
!-------------------------------------------------------------------!
READ DVCOMIN from FILE iodata HEADER "CINP" ;
READ DVFACIN from FILE iodata HEADER "FINP" ;
READ DVHOUS  from FILE iodata HEADER "HCON" ;

!-------------------------------------------------------------------!
!     Formulas to calculate the Initial solution                    !
!-------------------------------------------------------------------!
! FORMULAs for Y, ALPHAH(i) and Q(j) are only needed if require
   change differentiation or add the Newton correction terms. !

!   1. Formulas for initial prices   !
!....................................!

FORMULA (all,i,SECT) PC(i) = 1 ;
FORMULA (all,f,FAC)  PF(f) = 1 ;
FORMULA (all,j,SECT) W(j) = 1 ;
FORMULA (all,j,SECT) Q(j) = 1 ;

.!   2. Formulas which are also equations   !
!..........................................!

FORMULA & EQUATION Comin 
# Intermediate input of commodity i in industry j #
 (all,i,SECT)(all,j,SECT)
 XC(i,j) = DVCOMIN(i,j) / PC(i) ;
! Quantity   = Dollar value / price !

FORMULA & EQUATION Facin # Factor input f in industry j #
 (all,f,FAC)(all,j,SECT)
 XF(f,j) = DVFACIN(f,j)/PF(f) ;

FORMULA & EQUATION House # Household demand for Commodity i #
 (all,i,SECT)
 XH(i) = DVHOUS(i)/PC(i) ;

FORMULA & EQUATION Com_clear #Commodity market clearing #
! (E3.1.6) in DPPW !
(all,i,SECT)   XCOM(i) = XH(i) + SUM(j,SECT, XC(i,j)) ;

FORMULA & EQUATION Factor_use # Aggregate primary factor usage #
! (E3.1.7) in DPPW ! 
(all,f,FAC)   XFAC(f) = SUM(j,SECT, XF(f,j)) ;

!  3. Formula for initial value of Y !
!....................................!
FORMULA Y = SUM(i,SECT,PC(i)*XH(i)) ;

!  4. Formulas for the parameters   !
!...................................!

FORMULA (all,i,SECT)(all,j,SECT)
 ALPHACOM(i,j) = XC(i,j)/XCOM(j) ;

FORMULA (all,f,FAC)(all,j,SECT)
 ALPHAFAC(f,j) = XF(f,j)/XCOM(j) ;

FORMULA (all,i,SECT)
 ALPHAH(i) = PC(i)*XH(i)/Y ;

!-------------------------------------------------------------!
!  Levels Equations    (Numbers refer to DPPW)                !
!-------------------------------------------------------------!
EQUATION Consumer_demands #Household expenditure functions #
! (E3.1.9) in DPPW ! 
 (all,i,SECT)  XH(i) = ALPHAH(i)*Y/PC(i)  ;

EQUATION Intermediate_com
 # Intermediate demand for commodity i by industry j # 
! (E3.1.10) in DPPW !
 (all,i,SECT) (all,j,SECT)
 XC(i,j) = ALPHACOM(i,j)*Q(j)*XCOM(j)*W(j)/PC(i) ;

EQUATION E_W # Define W(j) to simplify other equations #
 (all,j,SECT)
 W(j) = PROD(t,SECT,PC(t)^ALPHACOM(t,j)) *
                      PROD(u,FAC,PF(u)^ALPHAFAC(u,j)) ;

EQUATION Factor_inputs  # Factor input demand functions #
                                      !(E3.1.10) in DPPW ! 
 (all,f,FAC) (all,j,SECT)
 XF(f,j) = ALPHAFAC(f,j)*Q(j)*XCOM(j)*W(j)/PF(f) ;

EQUATION Price_formation # Unit cost index for industry j #
 (all,j,SECT)   PC(j) = Q(j)*W(j) ; ! (E3.1.12) in DPPW !

EQUATION Numeraire
 # Numeraire for the model is price of commodity 1 (E3.1.23)#
 PC("s1") = 1 ;              
!-------------end of TABLO Input file-------------------------!

4.6    TABLO linearizes levels equations automatically [gpd1.3.7]

When TABLO processes a TAB file containing levels EQUATIONs and VARIABLEs, it converts the file to a linearized file (we call it the associated linearized TABLO Input file). You can see the linearized equations on the INF file and evaluate them in AnalyseGE (see section 18.3).

The most important feature of this conversion is that, for each levels VARIABLE, say X, in your original TABLO Input file, there is an associated linear VARIABLE whose name is that of the original levels variable with "p_" added at the start.²⁰ Also, for each levels VARIABLE in the original TABLO Input file, a COEFFICIENT with the same name as the levels VARIABLE is declared in the associated linearized TABLO Input file.

It is important to realise that the rest of TABLO (the last part of the CHECK and all of the CONDENSE and CODE stages) proceeds

as if the associated linearized TABLO Input file were the actual TABLO Input file.

This means that warnings and error messages given by TABLO may refer to statements in this associated linearized file rather than in your original TABLO Input file.²¹ Other features of this conversion are explained in section 9.2.

4.7    Creating the TABLO input file and command files for your own model [gpd1.3.9]

When you want to build your own model, you will usually construct the TABLO Input file by modifying one from an existing model. For example, you may wish to add some equations to an existing model.

Alternatively, you can create a TABLO Input file for your model from scratch. Suggestions about this can be found in section 8.3.

Whenever you are building or modifying a TABLO Input file, you will probably want to use the TABmate editor (see section 36.4) if you are working on a PC. TABmate assists you to identify and remove syntax or semantic errors from your TABLO Input file, as the examples in section 4.7.1 below show.

You will also need to write Command files for simulations. In section 4.7.2 below, we show you how you can identify and correct errors in Command files.

4.7.1    Correcting errors in TABLO input files [gpd1.3.9.1]

In the example below, we show you how to fix all errors in the TABLO Input file sjerror.tab which is supplied with the GEMPACK Examples.

TABmate can be a great help in finding errors. The example below shows you how to use TABmate to correct a TABLO Input file SJERROR.TAB which contains some typical errors.

Check how your WinGEM is configured by selecting

Options | Editor for TABLO Check Errors

and then slide your mouse across to click on Use TABmate.

Set your working directory to the subdirectory \SJ as described in section 3.4.2.

Now open a TABLO window via Simulation | TABLO Implement... and then, in this window, Select the TABLO Input file SJERROR.TAB. Click on Run to run TABLO. This run will find errors and so you should see a new window titled Error running TABLO In this window, click on Edit TABLO file.

This will cause TABmate display SJERROR.TAB. Indeed, TABmate will show you the first error, which occurs at the beginning of the declaration of variable XCOM. You should see a wriggly red line under the word VARIABLE at the start of this line (line number 55 of the file). To see the reason for this error, click on the word VARIABLE which is underlined in red. You will see the reason

Expected ;

shown (also in red) in the Error status panel in the bottom right-hand half of the TABmate's bottom panel. [After a few seconds the reason will go away, but you can get it back by clicking on the bottom panel or on the red-underlined word.]

You can see that a semi-colon is missing from the end of the previous line (the end of the declaration of variable PF). To remedy this error, insert a semi-colon at the end of that line. TABmate does not immediately realise that you have fixed this error. However you can ask TABmate to check the file by clicking on the TABLO Check button near the middle of the top part of TABmate. When you click on this Check button, TABmate first saves the TAB file and then runs TABLO to check the file.

This time it gets past the previous error but finds another error, underlining the word FACT in red and giving Unknown set as the reason for this error. A moment's reflection will tell you that the name of this set is just FAC (not FACT), so correct this error by removing the final "T". Then click on TABLO Check button again. This time TABmate tells you No error found (in "go-ahead" green rather than "stop" red).

Now that you have removed all errors, you can return to WinGEM to continue. To do this, close TABmate (for example, by selecting File | Exit from the main TABmate menu). You will see WinGEM's Error running TABLO window. In this window, click on Rerun. Then WinGEM will rerun TABLO. This time there should be no errors and TABLO will produce either a TABLO-generated program or else output for GEMSIM as usual.

This illustrates the procedure for removing errors from TABLO Input files.

• Run TABLO
• Use TABmate (and its TABLO Check button) to remove all errors, then close TABmate.
• Click on the Rerun button to rerun TABLO under WinGEM to produce a TABLO-generated program or output for GEMSIM.

tablo -pgs sjerror

tabmate sjerror.inf

     51   VARIABLE (all,i,SECT)  PC(i)   # Price of commodity i #
     52                                  ! This is p:i (i=1,2) in DPPW ! ;
     53   VARIABLE (all,f,FAC)   PF(f)   # Price of factor f #
     54                                  ! This is p:i (i=3,4) in DPPW !
     55   VARIABLE (all,i,SECT)  XCOM(i)
          ?
 %% Syntax error.
 Expected ;.
     56       # Total demand for (or supply of) commodity i #
     57                                  ! This is x:i (i=1,2) in DPPW ! ;

     87   COEFFICIENT (all,f,FACT)(all,j,SECT)   ALPHAFAC(f,j)
                             ?
 %% Semantic problem.
 Unknown set.
     88    # Share of factor input f in costs of industry j # ;

    109   FORMULA (all,i,FAC) PF(i) = 1.0 ;
                              ?
 %% Semantic problem.
 Unknown coefficient or variable.