[Help-glpk] [Fwd: preprocessing goes into infinite loop]

[Andrew Makhorin]

-------- Forwarded Message --------
From: John Perry <address@hidden>
To: address@hidden <address@hidden>
Subject: preprocessing goes into infinite loop
Date: Fri, 13 Jan 2012 17:28:32 -0600

Hello!

I work with the Sage computer algebra system, which can use GLPK as a backend 
to solve mixed integer linear programs. Unfortunately, Sage sometimes crashes 
when I am trying to solve some linear systems that are machine-generated for a 
problem of interest to me.

I managed to reproduce one of these problems directly in GLPK, linking via C++. 
I have placed a copy of the program at

    www.math.usm.edu/perry/glpk_bug.cpp

The problem creates an LP w/45 rows and 5 columns that apparently sends GLPK's 
preprocessing into an infinite loop. If the 45th row is not added (comment out 
the BOOM macro at the beginning of the file) then the LP finds a solution.

We believe this is a bug in GLPK. If it is a problem with how we are accessing 
GLPK from Sage, please let us know.

Thank you for your attention to this!

regards
john perry