> I'm trying to solve this simple problem: > \* Problem: Unknown *\
> Maximize > obj: + 0.8 Z.1 + 0.2 Z.2 > Subject To > r.1: - Z.1 + U.1 <= 0.1 > r.2: - Z.1 + U.1 >= -0.1 > r.3: + Z.1 + U.1 <= 1 > r.4: + Z.1 + U.1 >= 0.7 > r.5: - Z.2 + U.1 <= 0.5 > r.6: - Z.2 + U.1 >= 0.125 > r.7: + Z.2 + U.1 <= 0.75 > r.8: + Z.2 + U.1 >= 0.34 > Bounds > 0 <= Z.1 <= 1 > 0 <= Z.2 <= 1 > 0 <= U.1 <= 1 > Generals > Z.1 > Z.2 > U.1 > End > If I try to solve it from a C program using the simplex method it > finds this solution: > Z.1 = 0.55 > Z.2 = 0.3 > U.1 = 0.388977 > But if I try to solve it using the command: > glpsol --simplex --cpxlp program_name.txt > it says: > glp_read_lp: reading problem data from `mip.txt'... > glp_read_lp: 8 rows, 3 columns, 16 non-zeros > glp_read_lp: 3 integer columns, all of which are binary > glp_read_lp: 26 lines were read > ipp_basic_tech: 0 row(s) and 0 column(s) removed > PROBLEM HAS NO PRIMAL FEASIBLE SOLUTION > Time used: 0.0 secs > Memory used: 0.0 Mb (35140 bytes) > It says that the variable are integer but they should not be integer. > Anyone could help me? What's wrong with it? Nothing is wrong. Your instance is mip, because it has integer variables defined in the section 'Generals'. The simplex solver, glp_simplex, ignores integrality conditions and, thus, finds optimal solution to lp relaxation. However, glpsol solves your instance as mip and reports that it has no integer feasible points. _______________________________________________ Help-glpk mailing list Help-glpk@gnu.org http://lists.gnu.org/mailman/listinfo/help-glpk
