Two Ways to Run GAMS GAMS / 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 optimization Company 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

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

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