Byrka, JaroslawSrinivasan, AravindSwamy, Chaitanya2010-02-022010-02-022010-02-02201010.1007/978-3-642-13036-6_19https://infoscience.epfl.ch/handle/20.500.14299/46374WOS:000279619300019We give a new randomized LP-rounding 1.725-approximation algorithm for the metric Fault- Tolerant Uncapacitated Facility Location problem. This improves on the previously best known 2.076-approximation algorithm of Swamy & Shmoys. To the best of our knowledge, our work provides the first application of a dependent-rounding technique in the domain of facility location. The analysis of our algorithm benefits from, and extends, methods developed for Uncapacitated Facility Location; it also helps uncover new properties of the dependent-rounding approach. An important concept that we develop is a novel, hierarchical clustering scheme. Typically, LP-rounding approximation algorithms for facility location problems are based on partitioning facilities into disjoint clusters and opening at least one facility in each cluster. We extend this approach and construct a laminar family of clusters, which then guides the rounding procedure. It allows to exploit properties of dependent rounding, and provides a quite tight analysis resulting in the improved approximation ratio.facility locationfault-tolerantapproximationdependent randomized roundingtext::conference output::conference proceedings::conference paper