[Bug-glpk] Another Bug in mip presolver?

[Ingo Thomas]

Hi,

Some time ago I posted a bug report regarding a bug in the presolver. Somehow 
the attached model file vanished, so I assume it has been rejected due to its 
size. I tried to reproduce the error with a reduced model, but I didnt succeed 
on that, so I try again to send the original model file, this time gzipped.

I encountered an error solving a medium-sized MIP (see attached file
x3.mod). Using the standard options, glpk reports the attached problem
to have no feasible solution, though it has by construction as well as
according to a number of other LP solvers, namely lpsolve, CPLEX 10,
COIN clp. Using either the interior point option or the --nopresol
option, glpk finds the correct solution.

The error does not seem to be related to the integer part, as it
occurs in the relaxed problem (option --nomip) as well.

Cheers, Ingo

x3.mod.gz
Description: GNU Zip compressed data