Improved Approximation Algorithms for the Single-Sink Buy-at-Bulk Network Design Problems

  • Raja Jothi
  • Balaji Raghavachari
Part of the Lecture Notes in Computer Science book series (LNCS, volume 3111)


Consider a given undirected graph G=(V, E) with non-negative edge costs, a root node rV, and a set DV of demands with d v representing the units of flow that demand vD wishes to send to the root. We are also given K types of cables, each with a specified capacity and cost per unit length. The single-sink buy-at-bulk (SSBB) problem asks for a low-cost installation of cables along the edges of G, such that the demands can simultaneously send their flows to sink/root r. The problem is studied with and without the restriction that the flow from a node must follow a single path to the sink (indivisibility constraint). We are allowed to install zero or more copies of a cable type on each edge. The SSBB problem is NP-hard. In this paper, we present a 145.6-approximation for the SSBB problem improving the previous best ratio of 216. For the divisible SSBB (DSSBB) problem, we improve the previous best ratio of 72.8 to α K , where α K is less than 65.49 for all K. In particular, α 2 < 12.7, α 3 < 18.2, α 4 < 23.8, α 5 < 29.3, α 6 < 33.9.


Approximation Ratio Steiner Tree Network Design Problem Single Path Euler Tour 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


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Copyright information

© Springer-Verlag Berlin Heidelberg 2004

Authors and Affiliations

  • Raja Jothi
    • 1
  • Balaji Raghavachari
    • 1
  1. 1.University of Texas at DallasRichardsonUSA

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