There was an error in my code when relaxing fixed constraints, easily spotted on a small example. Thanks again for the help and suggestions, and sorry for the noise created.
Regards, Rabih Le 24 janv. 2013 à 18:55, Rabih Chaar <[email protected]> a écrit : > I think I am doing something wrong in the application of elasticity variables > on each row. The non zero coefficients of the constraints matrix should > contain exactly elasticity variables additional non-zeros. The logs seems to > violate this > >>>> 450946+220038 !=642201 > > Regards, > > Rabih > > Le 24 janv. 2013 à 18:41, Rabih Chaar <[email protected]> a écrit : > >> Hello, >> Thanks for the quick reply. >> Concerning your recommendation on checking my objective coefficients, I was >> also outputting my relaxed problem in cplex, and everything seems fine. >> >> I am not having this behavior on all instances of the problem. For others I >> am getting the sinf not null. >> >> My goal is to implement an algorithm giving a minimal iis if the problem is >> infeasible, hence the relaxation. This is done programmatically via the glpk >> API, making a copy of the problem, adding the additional elasticity >> variables, setting there objective coefficients to one, setting the >> objective coefficients of initial variables to zero, and adapting row >> constraints with the elasticity variables. I will check my code again. >> >> I wanted to be sure that the primal simplex (on the initial problem) will >> always find a feasible domain if it exists. >> >> Thanks in advance. >> >> Rabih >> >> Le 24 janv. 2013 à 14:40, Andrew Makhorin <[email protected]> a écrit : >> >>> >>>> PS: here is a small log of both problems >>>> >>>> GLPK Simplex Optimizer, v4.47 >>>> 191255 rows, 68860 columns, 450946 non-zeros >>>> 0: obj = 0.000000000e+000 infeas = 5.436e+009 (28783) >>>> ... >>>> 17761: obj = -8.927238865e+008 infeas = 2.030e+007 (14520) >>>> PROBLEM HAS NO FEASIBLE SOLUTION >>>> >>>> Elasticity >>>> Addtional constraints 220038 for 191255 rows >>>> Current column size is 68860 >>>> Additional Constraints 220038 >>>> Current column size after resize is 288898 >>>> GLPK Simplex Optimizer, v4.47 >>>> 191255 rows, 288898 columns, 642201 non-zeros >>>> 0: obj = 0.000000000e+000 infeas = 5.436e+009 (28783) >>>> ... >>>> * 1552: obj = 0.000000000e+000 infeas = 1.490e-008 (28782) >>>> OPTIMAL SOLUTION FOUND >>>> Sinf is 0 >>> >>> BTW, in the second case the objective (Sinf, I guess) is zero on all >>> iterations. Probably you forgot to assign objective coefficients to >>> elastic variables. >> >> _______________________________________________ >> Help-glpk mailing list >> [email protected] >> https://lists.gnu.org/mailman/listinfo/help-glpk > > _______________________________________________ > Help-glpk mailing list > [email protected] > https://lists.gnu.org/mailman/listinfo/help-glpk _______________________________________________ Help-glpk mailing list [email protected] https://lists.gnu.org/mailman/listinfo/help-glpk
