[Help-glpk] Re: problem loading models

[Andrew Makhorin]

>I'm getting errors reading some models in mps and/or lp format with
>glpk.
>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
>or 
>...
>/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
>chars?

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

Andrew Makhorin