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[Bug-glpk] Bug with LP format
From: |
Enric Rodriguez |
Subject: |
[Bug-glpk] Bug with LP format |
Date: |
Fri, 2 Nov 2007 19:15:33 +0300 |
Hi,
I think I've come across a bug with the function 'lpx_write_cpxlp' for
writing linear programs in CPLEX LP format. The problem is with upper
bounded variables that do not have lower bound. Such a variable say x is
written by GLPK as x <= upper_bound in the Bounds section of the LP
file. But since variables in LP format are understood to be
non-negative, in fact CPLEX understands 0 <= x <= upper_bound, which is
not the intended meaning. Instead, GLPK should write something like -Inf
<= x <= upper_bound. I attach a program that produces an LP file which,
once fed into CPLEX, allows one to see the error if CPLEX is asked to
write the linear program again (or if it is asked for the lower bound of
the variable).
By the way, congratulations on your excellent code. :-)
Best regards,
Enric
--
________________________________________________________________
Enric Rodriguez Carbonell www.lsi.upc.edu/~erodri
Technical University of Catalonia (UPC) address@hidden
Office 114 - Omega Building
Department of Software (LSI) Phone: +34-93-4137792
Jordi Girona 1, 08034 Barcelona, Spain Fax: +34-93-4137833
________________________________________________________________
p.c
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- [Bug-glpk] Bug with LP format,
Enric Rodriguez <=