The paper is aimed at experimental evaluation of the complexity of the p-Median problem instances, defined by m × n costs matrices, from several of the most widely used libraries. The complexity is considered in terms of possible problem size reduction and preprocessing, irrespective of the solution algorithm. We use a pseudo-Boolean representation of PMP instances that allows several reduction...

In this paper we consider the well known p-median problem. We study the behavior of the local improvement algorithm with a new large neighborhood. Computational experiments on the difficult instances show that the algorithm with the neighborhood is fast and finds feasible solutions with small relative error.

We study a well-known linear programming relaxation of the p-median problem. We give a characterization of the directed graphs for which this system of inequalities defines an integral polytope. As a consequence, we obtain that the p-median problem is polynomial in that class of graphs. We also give an algorithm to recognize these graphs. © 2011 Elsevier B.V. All rights reserved.

In combinatorial optimization, and particularly in location problems, the most used robustness criteria rely either on maximal cost or on maximal regret. However, it is well known that these criteria are too conservative. In this paper, we present a new robustness approach, called lexicographic α-robustness, which compensates for the drawbacks of the criteria based on the worst case. We apply t...

We study the p median problem which is one the classical problems in location theory For p and on a two dimensional mesh we give an O mn p time algorithm for solving the problem where assuming that m n m is the number of rows of the mesh containing demand points n the number of columns containing demand points and p the number of demand points

Facility-location problems have several applications in telecommunications, industrial transportation and distribution, etc. One of the most well-known facility-location problems is the p-median problem. This work addresses an application of the capacitated p-median problem to a real-world problem. We propose a genetic algorithm (GA) to solve the capacitated pmedian problem. The proposed GA use...

In the last decade, several robustness approaches have been developed to deal with uncertainty. In decision problems, and particularly in location problems, the most used robustness approach rely either on maximal cost or on maximal regret criteria. However, it is well known that these criteria are too conservative. In this paper, we present a new robustness approach, called lexicographic α-rob...

The Obnoxious p-Median problem consists in selecting a subset of p facilities from a given set of possible locations, in such a way that the sum of the distances between each customer and its nearest facility is maximized. The problem is NP-hard and can be formulated as an integer linear program. It was introduced in the 1990s, and a branch and cut method coupled with a tabu search has been rec...

In the competitive p-median problem, two decision makers, the leader and the follower, compete to attract clients from a given market. The leader opens his facilities, anticipating that the follower will react to the decision by opening his/her own facilities. The leader and the follower try to maximize their own profits. This is the Stackelberg game. We present it as a linear bilevel 0–1 probl...

The "double-cut-and-join" (DCJ) model of genome rearrangement proposed by Yancopoulos et al. uses the single DCJ operation to account for all genome rearrangement events. Given three signed permutations, the DCJ median problem is to find a fourth permutation that minimizes the sum of the pairwise DCJ distances between it and the three others. In this paper, we present a branch-and-bound method ...