# AMPL implementation in COIN OR

 4 We are solving a relatively large timetabling problem (15,000 decision variables) and we are trying to switch from IBM's CPLEX to a free solver. I am testing both CBC and Professor Nemhauser's MINTO solvers on NEOS website and I am using AMPL to make the models and the data files. After solving my model I'd like to print out my results but "display x;" brings all zero while I know that there should be some ones in the solution (b/c the objective value is not zero and also I have checked the model on CPLEX and it is not infeasible) Also none of the AMPL post processing commands work; for example the following for-loop command does not work for {i in PAIR, j in ROOM, t in TIME: x[i,j,t]>0} print i," ", j," ", t, " ",x[i,j,t]; My hunch is that the AMPL implementation in COIN is not a standard implementation but I might be wrong. Do you know what I am doing wrong? Thanks asked 14 Mar '10, 22:11 Mark ♦ 3.6k●2●23●50 accept rate: 9%

 2 You might want to try using GLPK which uses an AMPL-like interface known as GMPL. This may prove easier for you. http://www.gnu.org/software/glpk/ If you really want to use COIN than I recommend the MIP solver SYMPHONY. It can read AMPL files. From an FAQ... What modeling languages and file formats does SYMPHONY work with? SYMPHONY will read AMPL/GMPL files using GLPKs parser, or MPS file using COIN-OR's parser. It can also use FlopC++ as a modeling interface.  http://www.coin-or.org/SYMPHONY/index.htm answered 15 Mar '10, 12:58 larrydag 1 ♦ 3.2k●5●13●26 accept rate: 9% Thanks I will give it a try. I was using COIN because I just wanted to quickly test a number of different solvers and that website provided many of them. Thanks again (16 Mar '10, 02:10) Mark ♦
 3 If you haven't done so already, you might want to ask on the Cbc mailing list. answered 17 Mar '10, 21:01 Paul Rubin ♦♦ 14.6k●4●12 accept rate: 19%
 toggle preview community wiki

### Follow this question

By Email:

Once you sign in you will be able to subscribe for any updates here

Markdown Basics

• *italic* or _italic_
• **bold** or __bold__
• image?![alt text](/path/img.jpg "Title")
• numbered list: 1. Foo 2. Bar
• to add a line break simply add two spaces to where you would like the new line to be.
• basic HTML tags are also supported

Tags:

×191
×29
×7

Asked: 14 Mar '10, 22:11

Seen: 6,108 times

Last updated: 17 Mar '10, 21:01

### Related questions

OR-Exchange! Your site for questions, answers, and announcements about operations research.