Approximating survivable networks with minimum number of Steiner points

  • Authors:
  • Lior Kamma;Zeev Nutov

  • Affiliations:
  • The Open University of Israel;The Open University of Israel

  • Venue:
  • WAOA'10 Proceedings of the 8th international conference on Approximation and online algorithms
  • Year:
  • 2010

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Abstract

Given a graph H = (U,E) and connectivity requirements r = {r(u, v) : u, v ∈ R ⊆ U}, we say that H satisfies r if it contains r(u, v) pairwise internally-disjoint uv-paths for all u, v ∈ R. We consider the Survivable Network with Minimum Number of Steiner Points (SN-MSP) problem: given a finite set V of points in a normed space (M, ∥ċ∥), and connectivity requirements, find a minimum size set S ⊂ M - V of additional points, such that the unit disc graph induced by V ∪ S satisfies the requirements. In the (node-connectivity version of the) Survivable Network Design Problem (SNDP) we are given a graph G = (V, E) with edge costs and connectivity requirements, and seek a min-cost subgraph H of G that satisfies the requirements. Let k = maxu, v ∈ V r(u, v) denote the maximum connectivity requirement. We will show a natural transformation of an SN-MSP instance (V, r) into an SNDP instance (G = (V, E), c, r), such that an α-approximation for the SNDP instance implies an αċO(k2)- approximation algorithm for the SN-MSP instance. In particular, for the most interesting case of uniform requirement r(u, v) = k for all u, v ∈ V, we obtain for SN-MSP the ratio O(k2 ln k), which solves an open problem from [3].