We address a multi-item capacitated lot-sizing problem with setup times, stock and demand shortages. Demand cannot be backlogged, but can be totally or partially lost. Safety stock is an objective to reach rather than an industrial constraint to respect. In this paper we consider an approach based on a lagrangean relaxation of the capacity constraints to generate a lower bound of the optimal va...

Multi-item capacitated lot-sizing problems are reformulated using a class of valid inequalities, which are facets for the single-item uncapacitated problem. Computational results using this reformulation are reported, and problems vnth up to 20 items and 13 periods have been solved to optimality using a commercial mixed integer code. We also show how the valid inequalities can easily be generat...