Improved Approximation Algorithms for Capacitated Fault-Tolerant k-Center

Cristina G. Fernandes; Samuel P. de Paula; Lehilton L. C. Pedrosa

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arXiv · 1608.01721

Improved Approximation Algorithms for Capacitated Fault-Tolerant k-Center

Cristina G. Fernandes·Samuel P. de Paula·Lehilton L. C. Pedrosa

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Abstract

In the k-center problem, given a metric space V and a positive integer k, one wants to select k elements (centers) of V and an assignment from V to centers, minimizing the maximum distance between an element of V and its assigned center. One of the most general variants is the capacitated {\alpha}-fault-tolerant k-center, where centers have a limit on the number of assigned elements, and, if {\alpha} centers fail, there is a reassignment from V to non-faulty centers. In this paper, we present a new approach to tackle fault tolerance, by selecting and pre-opening a set of backup centers, then solving the obtained residual instance. For the {0,L}-capacitated case, we give approximations with factor 6 for the basic problem, and 7 for the so called conservative variant, when only clients whose centers failed may be reassigned. Our algorithms improve on the previously best known factors of 9 and 17, respectively. Moreover, we consider the case with general capacities. Assuming {\alpha} is constant, our method leads to the first approximations for this case. We also derive approximations for the capacitated fault- tolerant k-supplier problem.

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Cristina G. Fernandes, Samuel P. de Paula, Lehilton L. C. Pedrosa. 2016-08-04. Improved Approximation Algorithms for Capacitated Fault-Tolerant k-Center. https://arxiv.org/abs/1608.01721

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