A MIP-based framework and its application on a lot sizing problem with setup carryover

In this paper we present a framework to tackle mixed integer programming problems based upon a “constrained” black box approach. Given a MIP formulation, a black-box solver, and a set of incumbent solutions, we iteratively build corridors around such solutions by adding exogenous constraints to the original MIP formulation. Such corridors, or neighborhoods, are then explored, possibly to optimality, with a standard MIP solver. An iterative approach in the spirit of a hill climbing scheme is thus used to explore subportions of the solution space. While the exploration of the corridor relies on a standard MIP solver, the way in which such corridors are built around the incumbent solutions is influenced by a set of factors, such as the distance metric adopted, or the type of method used to explore the neighborhood. The proposed framework has been tested on a challenging variation of the lot sizing problem, the multi-level lot sizing problem with setups and carryovers. When tested on 1920 benchmark instances of such problem, the algorithm was able to solve to near optimality every instance of the benchmark library and, on the most challenging instances, was able to find high quality solutions very early in the search process. The algorithm was effective, in terms of solution quality as well as computational time, when compared with a commercial MIP solver and the best algorithm from the literature.