That's a good observation! :) I am actually maximizing an integer non-concave nonlinear program :S. I am using branch and bound to solve the problem, i.e.:
1. I make some decision on the integer variables.
2. For each decision variable, I try to get an upper and lower bound of the problem.
3. I compare the bounds of different branches (integer variables) and remove the worse ones.
4. After some iterations, I will stop, pick the best branch (integer variable) and hopefully know how far I am from the optimum (using the best upper bound).
Any feasible solution of a non-concave program can be treated as its lower bound. But, I need some ways to calculate a good upper bound (not +Inf :) ). I am looking for some software that can help me.
"Bruno Luong" <email@example.com> wrote in message <firstname.lastname@example.org>... > "Nazmul Islam" wrote in message <email@example.com>... > > > > > Unfortunately, my solution is getting stuck at a local minimum. Please let me know if I can get the lower bounds of this problem through the interior point method. > > -Inf is lower-bound. Of course it is useless answer, nevertheless it is a correct answer (You never explain why you need a lower-bound for). > > Bruno