Hi Woei Ling > Please find attached the > problem data set. Please let me know if you think having another > set of data will help you in diagnosing the problem.
Thank you. Your instances are classic example which beats the glpk simplex at all :+) I solved your small problem without any troubles, however the convergence was extremely slow due to high degeneracy: all constraints are equalities most of which have zero rhs (looking through the constraint matrix I guess it is a pure network problem). lpx_read_mps: reading problem data from `small.mps'... lpx_read_mps: problem network_ lpx_read_mps: 9249 rows, 18084 columns, 206628 non-zeros lpx_read_mps: 128822 cards were read lpx_simplex: original LP has 9249 rows, 18084 columns, 206628 non-zeros lpx_simplex: presolved LP has 9248 rows, 9316 columns, 197312 non-zeros lpx_adv_basis: size of triangular part = 9088 0: objval = 0.000000000e+00 infeas = 1.000000000e+00 (128) 126: objval = 2.088068648e+01 infeas = 4.353815783e-18 (112) * 126: objval = 2.088068648e+01 infeas = 2.220446049e-16 (112) * 200: objval = 1.446037689e+01 infeas = 3.885780586e-16 (99) * 400: objval = 8.348297709e+00 infeas = 0.000000000e+00 (70) * 600: objval = 8.348297709e+00 infeas = 0.000000000e+00 (26) * 800: objval = 8.348297709e+00 infeas = 0.000000000e+00 (22) * 1000: objval = 8.348297709e+00 infeas = 0.000000000e+00 (21) . . . . . . . * 50200: objval = 7.462112984e+00 infeas = 8.411967574e-13 (16) * 50361: objval = 7.462112984e+00 infeas = 0.000000000e+00 (16) OPTIMAL SOLUTION FOUND Time used: 896.0 secs Memory used: 30.1M (31515772 bytes) In principle, glpk simplex is able to solve your problem; however, I would suggest to use more specialized methods like network simplex (it is not implemented in glpk) or a version of out-of-kilter algorithm, because they would obtain the solution much faster. Andrew Makhorin _______________________________________________ Help-glpk mailing list Help-glpk@gnu.org http://lists.gnu.org/mailman/listinfo/help-glpk