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[Help-glpk] Re: problem loading models

From: Andrew Makhorin
Subject: [Help-glpk] Re: problem loading models
Date: Sat, 31 Jan 2004 11:17:51 +0300

>I'm getting errors reading some models in mps and/or lp format with
>The errors I get are like:
>load_mps: reading LP data from `/cygdrive/e/lodi/mpsts/blp-ir98.mps'...
>load_mps: name `UNKNOWN'
>/cygdrive/e/lodi/mpsts/blp-ir98.mps:4: invalid data dsa->card
>Cannot load model
>/cygdrive/e/lodi/blp-ir98.lp:31566: warning: name `oneblpline(Ah.Am...'
>too long; truncated to 16 characters
>/cygdrive/e/lodi/blp-ir98.lp:31566: constraint `oneblpline(Ah.Am'
>multiply defined
>Cannot load model
>Note that cplex can load both the lp and mps files without problems,
>also COIN-OR can read the mps files all-right, and BTW the mps files
>have been generated by cplex.

Many lp/mip solvers allow some deviations from the strict mps format
while glpk does not allow that. Please consult the reference manual.
If you think there is a bug, please send me the mps file which causes
the error.

>So it looks like glpk has some too tight limit on variable/constraint
>name lengths (even if in the mps case, it actually doesn't say what the
>problem is).

In mps all names are limited to 8 chars. The message 'invalid data card'
means that corresponding data card (text line) has wrong formatting.

>Would it be easy to change the glpk code to support names longer than 16

Unfortunately, there is no symbolic constant, so you need to change the
numeric literal '16' everywhere in glplpt.h and glplpt.c.

Andrew Makhorin

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