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Re: [Help-glpk] inf as RHS of constraint


From: Xypron
Subject: Re: [Help-glpk] inf as RHS of constraint
Date: Tue, 18 Jan 2011 08:08:21 +0100
User-agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.1.16) Gecko/20101123 SeaMonkey/2.0.11

Hello Kevin,

if the right hand side is infinity the constraint is not really needed.

Which version of GLPK have you been using? GLPK 4.45 should support inf and infinity.

Best regards

Xypron


Kevin Hunter wrote:
Hullo List,

I've recently created an LP that file that both CPlex and Gurobi accept and solve, but that GLPK does not (LP file attached). The issue is the use of infinity ('inf') on the right-hand side of a constraint.

Judging from the grammar in the comments above 'parse_constraints' in glpcpx.c, it would appear that GLPK does not support it. Should I consider this a bug? Or is there perhaps a better way I should be writing these constraints?

Thanks,

Kevin

P.S. The ironic thing is that the only place that I can find a thorough grammar for the *CPLEX* LP format is within the GLPK project. Kudos to GLPK for quality code backed by an actual grammar!




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