47th Annual IEEE Symposium on Foundations of Computer Science (FOCS'06)
Approximation Algorithms for Non-Uniform Buy-at-Bulk Network Design
Berkeley, California
October 21-October 24
ISBN: 0-7695-2720-5
We consider approximation algorithms for non-uniform buy-at-bulk network design problems. The first nontrivial approximation algorithm for this problem is due to Charikar and Karagiozova (STOC? 05); for an instance on h pairs their algorithm has an approximation guarantee of exp\left( {O\left( {\sqrt {\log h\log \log h} } \right)} \right) for the uniform-demand case, and logD ? exp\left( {O\left( {\sqrt {\log h\log \log h} } \right)} \right) for the general demand case, where D is the total demand. We improve upon this result, by presenting the first poly-logarithmic approximation for this problem. The ratio we obtain is O\left( {\log ^3 h \cdot \min \left\{ {\log D,\gamma \left( {h^2 } \right)} \right\}} \right) where h is the number of pairs and ?(n) is the worst case distortion in embedding the metric induced by a n vertex graph into a distribution over its spanning trees. Using the best known upper bound on \gamma(n) we obtain an O\left( {\min \left\{ {\log ^3 h \cdot \log D,\log ^5 h\log \log h} \right\}} \right) ratio approximation. We also give poly-logarithmic approximations for some variants of the singe-source problem that we need for the multicommodity problem.
Citation:
C. Chekuri, M. T. Hajiaghayi, G. Kortsarz, M. R. Salavatipour, "Approximation Algorithms for Non-Uniform Buy-at-Bulk Network Design," focs, pp.677-686, 47th Annual IEEE Symposium on Foundations of Computer Science (FOCS'06), 2006