Two Ways to Run GAMSGAMS / MPSGE Course: Yerevan, Armenia

May 3 – 7, 2010

Introduction to GAMS

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 optimizationCompany is small (4-5 people), based in

Georgetown, Washington, DC.

Structure of GAMS

GAMS is a “modular” system

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)

Using GAMS: GUI or Command?

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

GAMS IDE

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 and CONs

Pros:◦ Easy to get started◦ Point and click◦ Automatically organizes files / folders◦ Integrated text editor

Cons:◦ Hard to understand what happens in “background”◦ File locations are un-intuitive◦ Always need a “project dir”◦ Text-editor is weak

Traditional GAMS

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

GAMS + Epsilon

GAMS + Epsilon

Pros:◦ Easier to see where files are◦ More powerful text editor◦ Doesn’t require the mouse

Cons:◦ 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