> For the attached testcase, we obtain that > $ glpsol p0033.mps --max -o output.gomory --gomory
> gives an optimum of 5201, while > $ glpsol p0033.mps --max -o output.intopt --intopt > gives an optimum of 5131. The optimum 5201 is confirmed > by a completely different MIP solver. > Does this behavior indicate there is a bug somewhere? The bug appears if the constant term of the objective is non-zero either originally or due to fixing some columns at non-zero value by the mip preprocessor. In my previous post I just commented out the corresponding fragment leading to wrong results. To fix the bug in a correct way please replace lines 748 and 751 (the routine ios_preprocess_node, file src/glpios02.c): 748: L[0] = -DBL_MAX, U[0] = mip->mip_obj; 751: L[0] = mip->mip_obj, U[0] = +DBL_MAX; by the following ones: 748: L[0] = -DBL_MAX, U[0] = mip->mip_obj - mip->c0; 751: L[0] = mip->mip_obj - mip->c0, U[0] = +DBL_MAX; Please note that these changes will appear in the next version of the package. Andrew Makhorin _______________________________________________ Bug-glpk mailing list [email protected] http://lists.gnu.org/mailman/listinfo/bug-glpk
