[Bug-glpk] xassert fail in MIR cut back substitution

[Stefan Vigerske]

Hi,

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.)

Best,
Stefan

glpk_mirassertfail.lp
Description: Text document