> I have a problem with the new version of GLPK. I tried solving a > LP with > version 4.1 and had no errors with the standalone solver and > --nopresol > setting. Using --std I get an error message numerical > instability primal > simplex phase I, but glpsol produces a result. If I use version > 4.5 and > higher glpsol is not able to produce results. I just get > hundreds of primal > simplex phase II numercal instabilities and the solver is stuck > in a loop. > > I will attach the .mps-file.
Using `--nopresol' option I managed to solve your instance (see the log below). Most probably the instance is not well conditioned due to extra round-off errors introduced by the lp presolver. Andrew Makhorin lpx_read_mps: reading problem data from `UnstableLP.mps'... lpx_read_mps: problem eSimGene lpx_read_mps: 622 rows, 373 columns, 1460 non-zeros lpx_read_mps: 23 integer columns, 22 of which are binary lpx_read_mps: 1933 cards were read lpx_adv_basis: size of triangular part = 598 0: objval = -1.500000000e+000 infeas = 1.000000000e+000 (23) 44: objval = -1.484875533e+000 infeas = 3.391932213e-001 (22) spx_simplex: numerical instability (primal simplex, phase I) 44: objval = -1.484875533e+000 infeas = 1.000000000e+000 (21) 57: objval = -9.999999954e-001 infeas = 8.487112738e-001 (22) spx_simplex: numerical instability (primal simplex, phase I) 57: objval = -9.999999954e-001 infeas = 1.000000000e+000 (21) 111: objval = 1.373978193e+001 infeas = 7.632769432e-015 (21) * 111: objval = 1.373978193e+001 infeas = 1.136868377e-013 (21) * 116: objval = 1.363848093e+001 infeas = 1.136868377e-013 (21) OPTIMAL SOLUTION FOUND Integer optimization begins... + 116: mip = not found yet >= -inf (1; 0) + 136: mip = 1.597152145e+001 >= 1.363848093e+001 14.6% (11; 0) + 178: mip = 1.597152145e+001 >= tree is empty 0.0% (0; 43) INTEGER OPTIMAL SOLUTION FOUND Time used: 3.0 secs Memory used: 0.8M (882064 bytes) _______________________________________________ Help-glpk mailing list Help-glpk@gnu.org http://lists.gnu.org/mailman/listinfo/help-glpk