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Re: [Help-glpk] CPLEX vs GMPL: different answers for same problem
From: |
Kevin Hunter |
Subject: |
Re: [Help-glpk] CPLEX vs GMPL: different answers for same problem |
Date: |
Mon, 22 Oct 2012 01:35:00 -0400 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:16.0) Gecko/20121011 Thunderbird/16.0.1 |
At 7:13pm -0400 Sat, 20 Oct 2012, Reginald Beardsley wrote:
I've successfully converted from CPLEX to GMPL but have discovered
that the answers are different. They're both excellent, but they're
not the same.
I *think* I'm solving the same problems, but the input to glpsol is
being created by a program and the files run 50,000+ lines so it's
quite difficult to check.
One method that I have employed in the past to make sure I made no
mistakes when translating models is to have each utility write its
respective understanding of an LP in LP format. i.e.
...
cplex> write cplex_version.lp
...
$ glpsol --math mymodel --wlp glpk_version.lp --check
Then it's a (sometimes painful) exercise in rearranging the respective
files to see the exact differences. Having an editor with regular
expression support comes in rather handy here.
This is nice because the LP file format is a medium all parties
understand, and makes for easy differential finding with utilities like
'diff'.
HTH,
Kevin