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The years since the 1950s have seen the rapid development of algorithms and computer codes to analyze and solve large mathematical programming problems. One important part of this growth was the development in the early 1980's of modeling systems, one of the earlier of which was the Generalized Algebraic Modeling System or GAMS - the topic of this book. GAMS is designed to
| • | Provide an algebraically based high-level language for the compact representation of large and complex models |
| • | Allow changes to be made in model specifications simply and safely |
| • | Allow unambiguous statements of algebraic relationships |
| • | Provide an environment where model development is facilitated by subscript based expandability allowing the modeler to begin with a small data set, then after verifying correctness expand to a much broader context. |
| • | Be inherently self documenting allowing use of longer variable, equation and index names as well as comments, data definitions etc. GAMS is designed so that model structure, assumptions, and any calculation procedures used in the report writing are documented as a byproduct of the modeling exercise in a self-contained file. |
| • | Be an open system facilitating interface to the newest and best solvers while being solver independent allowing different solvers to be used on any given problem |
| • | Automate the modeling process including |
| — | permitting data calculation; |
| — | verifying the correctness of the algebraic model statements; |
| — | checking the formulation for obvious flaws; |
| — | interfacing with a solver; |
| — | saving and submitting an advanced basis when doing related solutions; |
| — | permitting usage of the solution for report writing. |
| • | Permitting portability of a model formulation between computer systems allowing usage on a variety of computers ranging from PC's to workstations to super computers. |
| • | Switching solvers is also very simple requiring changing a solver option statement or changing from using LP to using NLP. |
| • | Facilitating import and export of data to and from other computer packages |
| • | Allow use by groups of varying expertise |
| • | Provide a example models that may assist modelers through provision of a model library. |
This Users Guide updates and expands upon the original document by Brooke, Kenderick and Meeraus and a revision thereof by Brooke, Kenderick, Meeraus and Raman. This document unifies many system features that have occurred in the continuing system development efforts of the GAMS development Corporation with the capabilities of modern day electronic documents and computer systems.
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