Approximating Soft-Capacitated Facility Location Problem With   Uncertainty
  We first show that a better analysis of the algorithm for The Two-Sage Stochastic Facility Location Problem from Srinivasan \cite{sri07} and the algorithm for The Robust Fault Tolerant Facility Location Problem from Byrka et al \cite{bgs10} can render improved approximation factors of 2.206 and \alpha+4 where \alpha is the maximum number an adversary can close, respectively, and which are the best ratios so far.   We then present new models for the soft-capacitated facility location problem with uncertainty and design constant factor approximation algorithms to solve them. We devise the stochastic and robust approaches to handle the uncertainty incorporated into the original model. Explicitly, in this paper we propose two new problem, named The 2-Stage Soft-Capacitated Facility Location Problem and The Robust Soft-Capacitated Facility Location Problem respectively, and present constant factor approximation algorithms for them both. Our method uses reductions between facility location problems and linear-cost models, the randomized thresholding technique of Srinivasan \cite{sri07} and the filtering and clustering technique of Byrka et al \cite{bgs10}. 
Shuxin Cai, Wenguo Yang, Yaohua Tang
cs.DS