Local Search Algorithms for the Red‐Blue Median Problem

Local Search Algorithms for the Red‐Blue Median Problem

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Article ID: iaor20123977
Volume: 63
Issue: 4
Start Page Number: 795
End Page Number: 814
Publication Date: Aug 2012
Journal: Algorithmica
Authors: , ,
Keywords: combinatorial optimization, heuristics: local search
Abstract:

In this paper, we consider the following red‐blue median problem which is a generalization of the well‐studied k‐median problem. The input consists of a set of red facilities, a set of blue facilities, and a set of clients in a metric space and two integers k r ,k b ≥0. The problem is to open at most k r red facilities and at most k b blue facilities and minimize the sum of distances of clients to their respective closest open facilities. We show, somewhat surprisingly, that the following simple local search algorithm yields a constant factor approximation for this problem. Start by opening any k r red and k b blue facilities. While possible, decrease the cost of the solution by closing a pair of red and blue facilities and opening a pair of red and blue facilities. We also improve the approximation factor for the prize‐collecting k‐median problem from 4 (Charikar et al., 2001) to 3+ϵ, which matches the current best approximation factor for the k‐median problem.

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