An Oblivious O(1)-Approximation for Single Source Buy-at-Bulk

Ashish Goel, Ian Post

Research output: Chapter in Book/Report/Conference proceedingConference contribution

6 Scopus citations

Abstract

We consider the single-source (or single-sink) buy-at-bulk problem with an unknown concave cost function. We want to route a set of demands along a graph to or from a designated root node, and the cost of routing x units of flow along an edge is proportional to some concave, non-decreasing function f such that f(0) = 0. We present a polynomial time algorithm that finds a distribution over trees such that the expected cost of a tree for any f is within an O(1)-factor of the optimum cost for that f. The previous best simultaneous approximation for this problem, even ignoring computation time, was O(log |D|), where D is the multi-set of demand nodes. We design a simple algorithmic framework using the ellipsoid method that finds an O(1)-approximation if one exists, and then construct a separation oracle using a novel adaptation of the Guha, Meyerson, and Munagala [10] algorithm for the single-sink buy-at-bulk problem that proves an O(1) approximation is possible for all f. The number of trees in the support of the distribution constructed by our algorithm is at most 1 + log |D|. © 2009 IEEE.
Original languageEnglish (US)
Title of host publication2009 50th Annual IEEE Symposium on Foundations of Computer Science
PublisherInstitute of Electrical and Electronics Engineers (IEEE)
Pages442-450
Number of pages9
ISBN (Print)9781424451166
DOIs
StatePublished - Oct 2009
Externally publishedYes

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