GLPK/glpsol gives different objective values for mip/nomip
Domingo Alvarez Duarte <[email protected]> Tue, 6 Oct 2020 15:09:25 +0200
| Newsgroups | gmane.comp.gnu.glpk |
|---|---|
| Message-ID | <[email protected]> |
Hello ! Testing GLPK with miplib2017 I noticed that GLPK/glpsol gives different values for LP objective funcion value when a MIP problem is given with the option --nomip , is this the expected behavior ? Solving MIP -> * 6593: obj = 4.383346402e+07 inf = 1.946e-09 (0) 29 Soling "--nomip" -> * 6743: obj = 4.233035973e+07 inf = 6.147e-12 (0) 29 ==== glpsol --freemps mps/lrn.mps.gz GLPSOL: GLPK LP/MIP Solver, v4.65 Parameter(s) specified in the command line: --freemps mps/lrn.mps.gz Reading problem data from 'mps/lrn.mps.gz'... Problem: lrn Objective: func 8702 rows, 7253 columns, 52643 non-zeros 2455 integer variables, all of which are binary 67330 records were read 211 free rows were removed GLPK Integer Optimizer, v4.65 8491 rows, 7253 columns, 46123 non-zeros 2455 integer variables, all of which are binary Preprocessing... 112 hidden packing inequaliti(es) were detected 209 hidden covering inequaliti(es) were detected 1975 constraint coefficient(s) were reduced 5850 rows, 5299 columns, 31271 non-zeros 1654 integer variables, all of which are binary Scaling... A: min|aij| = 9.766e-04 max|aij| = 6.215e+07 ratio = 6.365e+10 GM: min|aij| = 5.419e-02 max|aij| = 1.845e+01 ratio = 3.405e+02 EQ: min|aij| = 2.937e-03 max|aij| = 1.000e+00 ratio = 3.405e+02 2N: min|aij| = 2.441e-03 max|aij| = 1.760e+00 ratio = 7.209e+02 Constructing initial basis... Size of triangular part is 5722 Solving LP relaxation... GLPK Simplex Optimizer, v4.65 5850 rows, 5299 columns, 31271 non-zeros 0: obj = 2.498157926e+07 inf = 1.866e+05 (334) 2731: obj = 5.436550173e+12 inf = 1.848e-11 (0) 20 * 6593: obj = 4.383346402e+07 inf = 1.946e-09 (0) 29 OPTIMAL LP SOLUTION FOUND Integer optimization begins... Long-step dual simplex will be used + 6593: mip = not found yet >= -inf (1; 0) ==== glpsol3 --nomip --freemps mps/lrn.mps.gz GLPSOL: GLPK LP/MIP Solver, v4.65 Parameter(s) specified in the command line: --nomip --freemps mps/lrn.mps.gz Reading problem data from 'mps/lrn.mps.gz'... Problem: lrn Objective: func 8702 rows, 7253 columns, 52643 non-zeros 2455 integer variables, all of which are binary 67330 records were read 211 free rows were removed GLPK Simplex Optimizer, v4.65 8491 rows, 7253 columns, 46123 non-zeros Preprocessing... 6994 rows, 6390 columns, 39179 non-zeros Scaling... A: min|aij| = 9.766e-04 max|aij| = 6.215e+07 ratio = 6.365e+10 GM: min|aij| = 5.419e-02 max|aij| = 1.845e+01 ratio = 3.405e+02 EQ: min|aij| = 2.937e-03 max|aij| = 1.000e+00 ratio = 3.405e+02 Constructing initial basis... Size of triangular part is 6859 0: obj = 1.806438124e+07 inf = 1.926e+05 (365) 2652: obj = 6.010935271e+12 inf = 7.411e-14 (0) 19 * 6743: obj = 4.233035973e+07 inf = 6.147e-12 (0) 29 OPTIMAL LP SOLUTION FOUND Time used: 2.3 secs Memory used: 13.2 Mb (13847675 bytes) ==== Cheers !