METAHEURISTIC APPROACHES FOR THE MULTILEVEL RESOURCE-CONSTRAINED LOT-SIZING PROBLEM WITH SETUP AND LEAD TIMES

We propose the use of metaheuristics for the resource-capacitated multilevel lot-sizing problem with general product structures, setup costs, setup times, and lead times. Initially, we develop a heuristic which moves production in time in order to obtain feasible solutions with good quality. Strategies for the short-term memory and long-term memory of tabu search are then included to guide the search of the subordinate heuristic for new, feasible, and better solutions. Simulated annealing components are embedded into tabu search in order to improve its performance. For small problems, the solutions provided by tabu search and the hybrid metaheuristic are compared to optimal solutions and for larger problems, the quality of the solutions is evaluated against a lower bound generated by Lagrangean relaxation.