I am trying to solve a fairly common MIP. Here are the problem characteristics. - Multi product , Multi site (sites simultaneously serve as production, demand & inventory storage locations). weekly time buckets
- products (unit: cases) can be made only in discrete batch sizes using limited number of shifts/batches at each site during each week.
- Transportation is allowed across sites to meet demand at any site
- Additionally minimum end of week inventory levels must be met at each location.
The current solution from a solver(gurobi) never reaches an MIP gap of better than 15 % from the best bound. If this problem does not have fixed batch sizes( can produce any quantity during a shift), it is straightforward. But if not, can someone suggest simple heuristic techniques to solve this kind of MIP?
asked
VM1 |

It would be of advantage to state the MIP, or at least the objective function and the most important constraints.

Gurobi has already applied some not-so-simple heuristic techniques to your problem. The 15% gap might indicate that Gurobi's solution has an objective value 15% above optimum; but more often Gurobi's solution is optimal or quite close to optimal, and it's only the bound that is 15% off because (informally speaking) the constraints don't give a tight enough continuous relaxation. A heuristic tailored to your problem might or might not give you a better solution than Gurobi's heuristics, and might not give any bound at all.