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Re: [Bug-glpk] glpsol: Assertion failed: x >= lb; file glpmip2.c; line 2
From: |
Andrew Makhorin |
Subject: |
Re: [Bug-glpk] glpsol: Assertion failed: x >= lb; file glpmip2.c; line 230 |
Date: |
Wed, 12 Apr 2006 18:38:14 +0400 |
> Attached find a MPS file that produces the following output when
> I try to
> solve it by invoking glpsol 4.9. as follows: glpsol --mps
> model.mps
>
> lpx_read_mps: reading problem data from `model.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+003 infeas =
> 1.000000000e+000 (0)
> 29: objval = 8.409999943e+002 infeas =
> 0.000000000e+000 (0)
> * 29: objval = 8.409999943e+002 infeas =
> 0.000000000e+000 (0)
> * 30: objval = 7.689999812e+002 infeas =
> 6.821210263e-013 (0)
> OPTIMAL SOLUTION FOUND
> Integer optimization begins...
> Objective function is integral
> + 30: mip = not found yet >= -inf (1;
> 0)
> Assertion failed: x >= lb; file glpmip2.c; line 230
>
> The model works for many different input parameters.
> Thanks in advance. Best regards,
This occurs due to excessive floating-point errors. Using the option
--intopt (which enables the mip presolver) resolves the problem:
lpx_read_mps: reading problem data from `model.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: 6 row(s) and 0 column(s) removed
ipp_reduce_coef: 1 pass(es) made, 0 coefficient(s) reduced
lpx_intopt: presolved MIP has 57 rows, 54 columns, 201 non-zeros
lpx_intopt: 54 integer columns, none of which are binary
lpx_adv_basis: size of triangular part = 57
Solving LP relaxation...
0: objval = -2.520000000e+03 infeas = 1.000000000e+00 (0)
29: objval = 8.409999943e+02 infeas = 0.000000000e+00 (0)
* 29: objval = 8.409999943e+02 infeas = 0.000000000e+00 (0)
* 30: objval = 7.689999812e+02 infeas = 0.000000000e+00 (0)
OPTIMAL SOLUTION FOUND
Integer optimization begins...
Objective function is integral
+ 30: mip = not found yet >= -inf (1; 0)
+ 32: mip = 7.689999943e+02 >= 7.690000000e+02 < 0.1% (3; 0)
+ 32: mip = 7.689999943e+02 >= tree is empty 0.0% (0; 5)
INTEGER OPTIMAL SOLUTION FOUND
Time used: 1.0 secs
Memory used: 0.2M (211932 bytes)