[Help-glpk] Re: [Bug-glpk] glpsol: Assertion failed: x >= lb; file glpmip2.c; line 230

[Andrew Makhorin]

> Thanks a lot. But now I tried a different parameter combination
> (please
> find them attached in the model_2.mps file). The sentence:
> 
> glpsol --mps --intopt model_2.mps
> 
> 
> produces the following:
> 
> 
> lpx_read_mps: reading problem data from `model_2.mps'...
> lpx_read_mps: problem name not specified
> lpx_read_mps: 65 rows, 54 columns, 240 non-zeros
> lpx_read_mps: 54 integer columns, none of which are binary
> lpx_read_mps: 239 cards were read
> ipp_basic_tech:  2 row(s) and 0 column(s) removed
> ipp_reduce_bnds: 2 pass(es) made, 18 bound(s) reduced
> ipp_basic_tech:  7 row(s) and 0 column(s) removed
> ipp_reduce_coef: 1 pass(es) made, 0 coefficient(s) reduced
> lpx_intopt: presolved MIP has 56 rows, 54 columns, 198 non-zeros
> lpx_intopt: 54 integer columns, none of which are binary
> lpx_adv_basis: size of triangular part = 56
> Solving LP relaxation...
>       0:   objval = -2.520000000e+003   infeas = 
> 1.000000000e+000 (0)
>      29:   objval =  2.017999987e+003   infeas = 
> 0.000000000e+000 (0)
> *    29:   objval =  2.017999987e+003   infeas = 
> 0.000000000e+000 (0)
> *    35:   objval =  6.229999868e+002   infeas = 
> 4.547473509e-013 (0)
> OPTIMAL SOLUTION FOUND
> Integer optimization begins...
> Objective function is integral
> +    35: mip =     not found yet >=              -inf        (1;
> 0)
> Assertion failed: x >= lb; glpmip2.c; line 230
> 
> 
> 
> which seems to be a similar mistake. Although I don't think it is
> an
> unfeasible problem instance, may this be connected to
> unfeasibility
> issues? Thanks,
> 

Now to solve your instance the mip pesolver should be disabled due
to the same reason:

lpx_read_mps: reading problem data from `model_2.mps'...
lpx_read_mps: problem name not specified
lpx_read_mps: 65 rows, 54 columns, 240 non-zeros
lpx_read_mps: 54 integer columns, none of which are binary
lpx_read_mps: 239 cards were read
lpx_simplex: original LP has 65 rows, 54 columns, 240 non-zeros
lpx_simplex: presolved LP has 63 rows, 51 columns, 216 non-zeros
lpx_adv_basis: size of triangular part = 63
      0:   objval =  -2.520000000e+03   infeas =   1.000000000e+00 (0)
     27:   objval =   6.229999868e+02   infeas =   0.000000000e+00 (0)
OPTIMAL SOLUTION FOUND
Integer optimization begins...
Objective function is integral
+    27: mip =     not found yet >=              -inf        (1; 0)
+    27: mip =   6.229999868e+02 >=   6.230000000e+02 < 0.1% (1; 0)
+    27: mip =   6.229999868e+02 >=     tree is empty   0.0% (0; 1)
INTEGER OPTIMAL SOLUTION FOUND
Time used:   0.0 secs
Memory used: 0.1M (134576 bytes)


Probably the troubles occur because some integer variables take
on relatively large values. I think reformulating the problem could
avoid this error. However, it is a lack of the implementation.

Andrew Makhorin