Showing papers by "Zeger Degraeve published in 2013"

Period Decompositions for the Capacity Constrained Lot Size Problem with Setup Times

Abstract: We study the Capacity Constrained Lot Size Problem with Setup Times (CLST). Based on two strong reformulations of the problem, we present a transformed reformulation and valid inequalities that speed up column generation and Lagrange relaxation. We demonstrate computationally how both ideas enhance the performance of our algorithm and show theoretically how they are related to dual space reduction techniques. We compare several solution methods, and propose a new efficient hybrid scheme that combines column generation and Lagrange relaxation in a novel way. Computational experiments show that the proposed solution method for finding lower bounds is competitive with other state-of-the-art approaches found in the literature. Finally, a branch-and-price based heuristic is designed and computational results are reported. The heuristic scheme compares favorably or outperforms similar approaches. Resume : Nous etudions un probleme de planification de production avec des contraintes de capacite et des temps de mise en route. En nous basant sur deux reformulations fortes du probleme, nous presentons une reformulation transformee et des inegalites valides qui accelerent la generation des colonnes et le processus de la relaxation Lagrangienne. Nous presentons des resultats qui indiquent que ces idees ameliorent la performance de nos algorithmes et nous demontrons d’une facon theorique comment ces idees sont liees aux techniques de reduction de l’espace dual. Nous comparons plusieurs methodes de resolution, et proposons une nouvelle approche hybride efficace. Les resultats indiquent que la methode pour trouver des bornes inferieures est competitive avec d’autres approches dans la litterature. Finalement, une nouvelle approche heuristique est proposee et nous rapportons des resultats favorables. Les Cahiers du GERAD G–2013–76 1