No dia dia 16 de Julho, pelas 11H00, na sala 6.4.30, realizar-se-á um Seminário organizado pelo Centro de Investigação Operacional com o título 'Lagrangian-Based Branch-and-Bound for Two-Echelon Uncapacitated Facility Location with Single Assignment Constraints', cujo orador é o Professor Bernard Gendron (CIRRELT and DIRO, Université de Montréal).

Abstract:

We present an exact method for the Two-Echelon Uncapacitated Facility Location with Single Assignment Constraints (TUFLPS), which arises in many applications in transportation, logistics and telecommunications.

In such applications, facilities in the first echelon, called depots, supply facilities in the second echelon, called satellites, to ultimately satisfy customer demands. The single assignment constraints ensure that each satellite is supplied from a single depot. These constraints either constitute a requirement of the problem, or they are implicitly satisfied, given that the costs decompose by arc. The algorithm we propose is based on the combination of a Lagrangian relaxation method and an IP-based large neighborhood search heuristic. The two approaches are complemented with variable fixing procedures and embedded within a branch-and-bound algorithm. The resulting algorithm is able to solve large-scale instances derived from a real application more efficiently than the state-of-the-art MIP software CPLEX.

*Joint work with: Paul-Virak Khuong (CIRRELT and DIRO, Université de Montréal), Frédéric Semet (École Centrale de Lille).