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Re: [Bug-glpk] xassert fail in MIR cut back substitution
From: |
Andrew Makhorin |
Subject: |
Re: [Bug-glpk] xassert fail in MIR cut back substitution |
Date: |
Tue, 4 Dec 2007 23:27:07 +0300 |
> I have a MIP where an assertion in the new mir cut generation routines
> in GLPK 4.24 is failing.
> Find attached a cplex-lp file. I was able to produce the problem on a
> linux 64bit machine, and it also appear on some other platforms, but not
> on every, e.g., not on linux 32bit.
> It should pop up with
> ./glpsol --cpxlp --intopt --cuts glpk_mirassertfail.lp
> and the output is
> lpx_read_cpxlp: reading problem data from `glpk_mirassertfail.lp'...
> lpx_read_cpxlp: 50 rows, 43 columns, 169 non-zeros
> lpx_read_cpxlp: 14 integer columns, all of which are binary
> lpx_read_cpxlp: 81 lines were read
> ipp_basic_tech: 6 row(s) and 5 column(s) removed
> ipp_reduce_bnds: 3 pass(es) made, 26 bound(s) reduced
> ipp_basic_tech: 0 row(s) and 0 column(s) removed
> ipp_reduce_coef: 1 pass(es) made, 0 coefficient(s) reduced
> lpx_intopt: presolved MIP has 44 rows, 38 columns, 152 non-zeros
> lpx_intopt: 12 integer columns, all of which are binary
> lpx_adv_basis: size of triangular part = 43
> Solving LP relaxation...
> 0: objval = 2.543860150e+04 infeas = 1.000000000e+00 (0)
> 24: objval = 6.655303517e+04 infeas = 0.000000000e+00 (0)
> * 24: objval = 6.655303517e+04 infeas = 0.000000000e+00 (0)
> * 43: objval = 1.779541789e+01 infeas = 5.079270338e-16 (0)
> OPTIMAL SOLUTION FOUND
> Creating the conflict graph...
> The conflict graph has 2*10 vertices and 15 edges
> Generating cutting planes...
> & 43: obj = 1.779541789e+01 frac = 3 cuts = 0 (0)
> & 95: obj = 1.789692248e+01 frac = 1 cuts = 10 (198)
> 10 Gomory's mixed integer cut(s) added
> Integer optimization begins...
> + 95: mip = not found yet >= -inf (1; 0)
> MIR cuts enabled
> ios_mir_init: warning: debug mode enabled
> GLPK internal error: jj != 0; file glpios05.c, line 1087
> (I had enabled _MIR_DEBUG for testing. The problem comes with or without
> it.)
Thank you for your bug report.
The bug is caused due to a missed fragment in a routine performing
back substitution.
Now the bug has been fixed. Please replace src/glpios05.c by a new
version (see attachment) and then rebuild the package.
glpios05.c.gz
Description: GNU Zip compressed data