> When I use primal simplex method to solve an unbounded LP problem. > Checking status gives this: > glp_get_status() returns GLP_UNBND, > glp_get_prim_stat() returns GLP_FEAS, > glp_get_dual_stat() returns GLP_NOFEAS. > Then using dual simplex method to solve the same problem, I got > glp_get_status() returns GLP_INFEAS, > glp_get_prim_stat() returns GLP_INFEAS, > glp_get_dual_stat() returns GLP_NOFEAS. > > Next, I use primal simplex method to solve another LP which is the > dual problem of the previous LP. > Checking status gives this: > glp_get_status() returns GLP_NOFEAS, > glp_get_prim_stat() returns GLP_NOFEAS, > glp_get_dual_stat() returns GLP_INFEAS. > Thent, I use dual simplex method, and I got > glp_get_status() returns GLP_NOFEAS, > glp_get_prim_stat() returns GLP_NOFEAS, > glp_get_dual_stat() returns GLP_FEAS. > I'd like to ask > (a) What is the difference between GLP_NOFEAS and GLP_INFEAS ?
GLP_INFEAS returned by glp_get_prim_stat or glp_get_dual_stat simply means that the current basis is primal (dual) infeasible. GLP_NOFEAS is a stronger status meaning that the problem has no primal (no dual) feasible solution, that is, the minimal sum of primal (dual) infeasibilities is non-zero for such problem. For more details please see the glpk reference manual. > (b) How can I check wheter the primal or dual solution is unbounded ? > Primal (dual) solution is unbounded if the problem has a primal (dual) feasible solution and no dual (primal) feasible solution. _______________________________________________ Help-glpk mailing list [email protected] https://lists.gnu.org/mailman/listinfo/help-glpk
