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Re: [Help-glpk] Help regarding MILP problem
From: |
Andrew Makhorin |
Subject: |
Re: [Help-glpk] Help regarding MILP problem |
Date: |
Thu, 30 Nov 2006 08:07:58 +0300 |
> I have a 0-1 MIP formulation of a file scheduling problem. The variables
> are all 0-1. When I run it using standard approach (as a MIP problem)
> using glpsol on the command line, it runs for a long time.
Try specifying the option --intopt that enables the mip presolver.
This signficantly reduces the running time for your instance:
lpx_read_cpxlp: reading problem data from `problem_data.lpt'...
lpx_read_cpxlp: 1132 rows, 496 columns, 3432 non-zeros
lpx_read_cpxlp: 496 integer columns, 495 of which are binary
lpx_read_cpxlp: 2196 lines were read
ipp_basic_tech: 451 row(s) and 180 column(s) removed
ipp_reduce_bnds: 2 pass(es) made, 4 bound(s) reduced
ipp_basic_tech: 12 row(s) and 4 column(s) removed
ipp_reduce_coef: 2 pass(es) made, 28 coefficient(s) reduced
lpx_intopt: presolved MIP has 669 rows, 312 columns, 2099 non-zeros
lpx_intopt: 312 integer columns, 311 of which are binary
lpx_adv_basis: size of triangular part = 669
Solving LP relaxation...
0: objval = 3.000000000e+00 infeas = 1.000000000e+00 (0)
168: objval = 9.000000000e+00 infeas = 3.589083054e-19 (0)
* 168: objval = 9.000000000e+00 infeas = 4.163336342e-17 (0)
* 200: objval = 6.333333333e+00 infeas = 2.704506029e-15 (0)
* 320: objval = 3.014284257e+00 infeas = 1.110223025e-15 (0)
OPTIMAL SOLUTION FOUND
Integer optimization begins...
Objective function is integral
+ 320: mip = not found yet >= -inf (1; 0)
. . . . .
+ 34137: mip = 5.000000000e+00 >= 4.000000000e+00 20.0% (10; 5223)
+ 34627: mip = 5.000000000e+00 >= tree is empty 0.0% (0; 5361)
INTEGER OPTIMAL SOLUTION FOUND
Time used: 46.0 secs
Memory used: 1.7M (1807748 bytes)