GEMPACK provides a simple language to describe and document the equations of an economic model. The equations can be non-linear levels equations, a linearised representation of the model, or a mixture of these two. A preprocessor (the program TABLO) is used to convert the equations to a form ready to run simulations with the model.
The program TABLO includes a condensation facility which makes it possible to solve very large models. Algebraic substitutions can be made symbolically in the system of linearized equations to reduce the system actually solved to a manageable size.
Using simple text files (Command files), it is easy to specify and carry out simulations. For example, there are options for varying the choice of exogenous and endogenous variables, and the variables shocked.
Algorithms in the simulation programs give increased accuracy in solution of the non-linear equations, by using multi-step simulations, extrapolation, subintervals and automatic accuracy techniques.
A generic simulation program, GEMSIM, can be used to solve all economic models. For larger models, compiled model-specific programs can be used to run simulations at increased speed.
GEMPACK contains utility programs to assist in managing the data base on which the model is based. The data can be inspected, modified, converted to spreadsheets or moved to different machines (including those with different operating systems).
On PCs running Windows XP or later, a Windows interface (WinGEM) can be used to run simulations and other programs. There are several other Windows programs to view data (ViewHAR) and simulation solutions (ViewSOL), and a text editor designed specifically for GEMPACK (TABmate).
GEMPACK is fully documented and has detailed examples to help new users.