Two Ways to Run GAMS
GAMS / MPSGE Course: Yerevan, Armenia
May 3 – 7, 2010
GAMS – Generalized Algebraic Modeling
System
 Strength: “Optimization”
 History:

◦ Originated in 1990 at World Bank
◦ Financed later by Oil-refineries
◦ Now used by economists, chemists, and other
scientists who need optimization

Company is small (4-5 people), based in
Georgetown, Washington, DC.
Introduction to GAMS
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GAMS is a “modular” system
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Base GAMS is the general data-management and
data-manipulation part.

GAMS “solvers” are separate plugin style software
developed by outsiders, for example:
◦ MINOS: Non-Linear Program (NLP) solver, by academics at
Stanford U.
◦ CONOPT: NLP developed by professor in Netherlands
◦ PATH: Mixed-Complimentary Solver (MCP) developed at U.
Wisconsin (Madison)
Structure of GAMS

For 20 years, GAMS has been a “command-line” program

In 2005, GAMS developed “GAMS-IDE” – the “Integrated
Development Environment”

IDE is a Graphical Interface for the Command-Line
software
Using GAMS: GUI or Command?
GAMS IDE
You get a “GUI” where you can edit the program
 But files are placed in a strange location:

◦ C:\users\lightm\Documents\gamsdir\projdir\trnsport.gms
GAMS IDE

Input Program (.gms) and outputs (.lst) have tabs
GAMS IDE

Pros:
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Easy to get started
Point and click
Automatically organizes files / folders
Integrated text editor
Cons:
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Hard to understand what happens in “background”
File locations are un-intuitive
Always need a “project dir”
Text-editor is weak
GAMS IDE: PROs and CONs
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Original GAMS uses a “command Line” (MS-DOS)
A separate Text Editor is required
Input and Output files are standard “text files”
No GUI
Must learn commands in MS-DOS
Traditional GAMS
Traditional GAMS
GAMS + Epsilon

Pros:
◦ Easier to see where files are
◦ More powerful text editor
◦ Doesn’t require the mouse

Cons:
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Harder to get Started
Requires learning about your computer
Can’t easily use the mouse
Must learn to use a text editor
Must learn to use MS-Dos commands
GAMS + Epsilon