Re: [Bug-glpk] glpsol cannot solve exported CPLEX file

[Heinrich Schuchardt]

Hello Andrew,

cplex 12.3 accepts a
Subject To
section without constraint.

Why should GLPK require the section to be non-empty?

The cplex online help for the file format does not describe such a requirement.

Best regards

Heinrich Schuchardt

http://www.xypron.de

Am 16.07.14 um 16:36 schrieb Andrew Makhorin

> Hi Heinrich,
> 
> 
> 
> Thank you for your bug report.
> 
> 
> 
> > given the following model:
> 
> > 
> 
> > var x, >=0;
> 
> > minimize obj : x + 5;
> 
> > end;
> 
> > 
> 
> > I export it with
> 
> > 
> 
> > glpsol -m test.mod --wlp test.lp --check
> 
> > 
> 
> > I get
> 
> > 
> 
> > \* Problem: test *\
> 
> > 
> 
> > Minimize
> 
> >   obj: + x
> 
> > \* constant term = 5 *\
> 
> > 
> 
> > Subject To
> 
> > 
> 
> > End
> 
> > 
> 
> > 
> 
> > Then I run
> 
> > 
> 
> > glpsol --lp test.lp
> 
> > 
> 
> > and receive the following output:
> 
> > 
> 
> > Reading problem data from 'test.lp'...
> 
> > test.lp:9: missing variable name
> 
> > CPLEX LP file processing error
> 
> > 
> 
> > 
> 
> > The bug is in glpcpx.c. In parse_constraints() the token check should be 
> 
> > moved from the end of the loop to the start of the loop.
> 
> 
> 
> I don't know how to better fix this bug. The problem is that your lp has
> 
> no constraints, however cplex lp format requires 'Subject To' section to
> 
> be non-empty.