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Re: [Bug-glpk] possible bug in 4.52
From: |
Andrew Makhorin |
Subject: |
Re: [Bug-glpk] possible bug in 4.52 |
Date: |
Fri, 26 Jul 2013 13:50:31 +0400 |
Thank you for your bug report.
>
> then the model does not solve. Sometimes, I receive the message
>
> Assertion failed: piv1 != 0.0
>
> Error detected in file ..\src\glpspx02.c at line 3026
>
> >Exit code: 3 Time: 444.488
>
> Since the assertion failed, it may be due to a bug in GLPK.
>
>
>
> More often, for the same problem, I receive
>
> Error: unable to factorize the basis matrix (1)
>
> Sorry, basis recovery procedure not implemented yet
>
> ios_driver: unable to solve current LP relaxation; glp_simplex
> returned 5
>
> +1664019: mip = not found yet >= 2.855670500e+003 (11689;
> 536)
>
> glp_intopt: cannot solve current LP relaxation
>
Most likely this error happens because of Gomory cuts; these tend to be
almost linearly dependent, and the simplex solver sometimes is unable to
detect this. Sorry, glpk is not perfect. Just do not use --gomory.
Please note that your model is hard at least to be solved to optimality.
Though I managed to find a feasible solution close to the optimum (see
below). The proxy heuristic also seems to be efficient. See also the
model output attached.
Andrew Makhorin
GLPSOL: GLPK LP/MIP Solver, v4.52
Parameter(s) specified in the command line:
-m model.mod --mir --pcost --bestp --log model.log
Reading model section from model.mod...
Reading data section from model.mod...
116 lines were read
. . .
Model has been successfully generated
GLPK Integer Optimizer, v4.52
1890 rows, 2988 columns, 15506 non-zeros
2988 integer variables, all of which are binary
Preprocessing...
128 hidden packing inequaliti(es) were detected
8 hidden covering inequaliti(es) were detected
308 constraint coefficient(s) were reduced
746 rows, 2400 columns, 11114 non-zeros
2400 integer variables, all of which are binary
Scaling...
A: min|aij| = 1.000e+00 max|aij| = 7.500e+02 ratio = 7.500e+02
GM: min|aij| = 8.629e-01 max|aij| = 1.159e+00 ratio = 1.343e+00
EQ: min|aij| = 7.580e-01 max|aij| = 1.000e+00 ratio = 1.319e+00
2N: min|aij| = 4.219e-01 max|aij| = 1.500e+00 ratio = 3.556e+00
Constructing initial basis...
Size of triangular part is 746
Solving LP relaxation...
GLPK Simplex Optimizer, v4.52
746 rows, 2400 columns, 11114 non-zeros
0: obj = 2.855630500e+03 infeas = 1.709e-01 (0)
* 112: obj = 2.856081402e+03 infeas = 1.388e-17 (0)
* 128: obj = 2.855636333e+03 infeas = 3.712e-16 (0)
OPTIMAL LP SOLUTION FOUND
Integer optimization begins...
MIR cuts enabled
+ 128: mip = not found yet >= -inf (1; 0)
Cuts on level 0: mir = 1;
+ 821: mip = not found yet >= 2.855637167e+03 (18; 0)
. . .
+ 49803: mip = not found yet >= 2.855637167e+03 (573; 88)
Cuts on level 354: mir = 32;
+ 50900: >>>>> 2.857540500e+03 >= 2.855637167e+03 < 0.1% (592; 112)
+ 55337: mip = 2.857540500e+03 >= 2.855637167e+03 < 0.1% (608; 130)
+ 58553: mip = 2.857540500e+03 >= 2.855637167e+03 < 0.1% (647; 136)
GLPSOL: GLPK LP/MIP Solver, v4.52
Parameter(s) specified in the command line:
-m model.mod --proxy 600 --log model1.log
Reading model section from model.mod...
Reading data section from model.mod...
116 lines were read
. . .
Model has been successfully generated
GLPK Integer Optimizer, v4.52
1890 rows, 2988 columns, 15506 non-zeros
2988 integer variables, all of which are binary
Preprocessing...
128 hidden packing inequaliti(es) were detected
8 hidden covering inequaliti(es) were detected
308 constraint coefficient(s) were reduced
746 rows, 2400 columns, 11114 non-zeros
2400 integer variables, all of which are binary
Scaling...
A: min|aij| = 1.000e+00 max|aij| = 7.500e+02 ratio = 7.500e+02
GM: min|aij| = 8.629e-01 max|aij| = 1.159e+00 ratio = 1.343e+00
EQ: min|aij| = 7.580e-01 max|aij| = 1.000e+00 ratio = 1.319e+00
2N: min|aij| = 4.219e-01 max|aij| = 1.500e+00 ratio = 3.556e+00
Constructing initial basis...
Size of triangular part is 746
Solving LP relaxation...
GLPK Simplex Optimizer, v4.52
746 rows, 2400 columns, 11114 non-zeros
0: obj = 2.855630500e+03 infeas = 1.709e-01 (0)
* 112: obj = 2.856081402e+03 infeas = 1.388e-17 (0)
* 128: obj = 2.855636333e+03 infeas = 3.712e-16 (0)
OPTIMAL LP SOLUTION FOUND
Integer optimization begins...
+ 128: mip = not found yet >= -inf (1; 0)
Applying PROXY heuristic...
Proxy's time limit set to 600 seconds.
Proxy's relative improvement set to 1.00 %.
Searching for a feasbile solution...
>>>>> first solution = 2.862701e+03;
Time used: 418.8 secs. Memory used: 8.1 Mb
Starting proximity search...
>>>>> it: 1: mip = 2.857441e+03; elapsed time 436.0 sec.s
Bound exceeded = 310.810005. Proxy heuristic terminated.
Time used: 436.2. Memory used: 8.1 Mb
Solution found by heuristic: 2857.4405
+ 128: mip = 2.857440500e+03 >= 2.855637167e+03 < 0.1% (2; 0)
Time used: 436.3 secs. Memory used: 4.0 Mb.
+ 924: mip = 2.857440500e+03 >= 2.855640500e+03 < 0.1% (28; 0)
+ 3961: mip = 2.857440500e+03 >= 2.855640500e+03 < 0.1% (37; 0)
+ 8381: mip = 2.857440500e+03 >= 2.855640500e+03 < 0.1% (37; 0)
model2.log.gz
Description: GNU Zip compressed data
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