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Re: [Bug-glpk] LP reader cannot read empty constraints


From: Andrew Makhorin
Subject: Re: [Bug-glpk] LP reader cannot read empty constraints
Date: Wed, 04 Dec 2013 13:14:48 +0400

> I just found another problem about GLPK lp reader (version 4.52.1).
> 
> I use CPLEX converted the '25FV47' problem in netlip from mps to lp
> and there are empty constraints. But I cannot read the lp file using
> GLPK lp reader as it complains 'missing variable name' (as you know an
> empty constraint does not have any variables).
> 
> Could this be changed in the future? Thanks.
> 

Disagree. The cplex lp format routine works correctly:

GLPSOL: GLPK LP/MIP Solver, v4.53
Parameter(s) specified in the command line:
 25fv47.mps --wlp 25fv47.lp --check
Reading problem data from `25fv47.mps'...
Problem: 25FV47
Objective: R0000
One free row was removed
821 rows, 1571 columns, 10400 non-zeros
6919 records were read
Writing problem data to '25fv47.lp'...
2504 lines were written

GLPSOL: GLPK LP/MIP Solver, v4.53
Parameter(s) specified in the command line:
 --lp 25fv47.lp --check
Reading problem data from '25fv47.lp'...
821 rows, 1571 columns, 10400 non-zeros
2504 lines were read

In particular, an empty row named 'F1X.0' appears in the lp file as
follows:

Subject To
 F1X.0: 0 MSEXP = 0

so glp_read_lp is able to correctly read back the lp file.





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