A simple and linear time randomized algorithm for computing sparse spanners in weighted graphs†

  1. Surender Baswana1,*,
  2. Sandeep Sen2

Article first published online: 4 OCT 2006

DOI: 10.1002/rsa.20130

Issue

Random Structures & Algorithms

Random Structures & Algorithms

Volume 30, Issue 4, pages 532–563, July 2007

Additional Information

How to Cite

Baswana, S. and Sen, S. (2007), A simple and linear time randomized algorithm for computing sparse spanners in weighted graphs. Random Structures & Algorithms, 30: 532–563. doi: 10.1002/rsa.20130

Author Information

  1. 1

    Max-Planck-Institut für Informatik, Stuhlsatzenhausweg 85, 66123 Saarbrücken, Germany

  2. 2

    Department of Computer Science and Engineering, Indian Institute of Technology Delhi, Hauz Khas, New Delhi-110016, India

*Computer Science and Engineering, I.I.T. Kanpur, Kanpur 208016, India

  1. †

    Preliminary version of this work appeared in the 30th International Colloquium on Automata, Languages and Programming, pages 384–396, 2003.

Publication History

  1. Issue published online: 29 MAY 2007
  2. Article first published online: 4 OCT 2006
  3. Manuscript Accepted: 22 DEC 2005
  4. Manuscript Received: 26 OCT 2004

Funded by

  • IBM UPP award
  • Infosys Technologies Ltd., Bangalore

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Keywords:

  • graph algorithms;
  • randomized algorithms;
  • shortest path;
  • spanner

Abstract

Let G = (V,E) be an undirected weighted graph on |V | = n vertices and |E| = m edges. A t-spanner of the graph G, for any t ≥ 1, is a subgraph (V,ES), ES ⊆ E, such that the distance between any pair of vertices in the subgraph is at most t times the distance between them in the graph G. Computing a t-spanner of minimum size (number of edges) has been a widely studied and well-motivated problem in computer science. In this paper we present the first linear time randomized algorithm that computes a t-spanner of a given weighted graph. Moreover, the size of the t-spanner computed essentially matches the worst case lower bound implied by a 43-year old girth lower bound conjecture made independently by Erdős, Bollobás, and Bondy & Simonovits.

Our algorithm uses a novel clustering approach that avoids any distance computation altogether. This feature is somewhat surprising since all the previously existing algorithms employ computation of some sort of local or global distance information, which involves growing either breadth first search trees up to θ(t)-levels or full shortest path trees on a large fraction of vertices. The truly local approach of our algorithm also leads to equally simple and efficient algorithms for computing spanners in other important computational environments like distributed, parallel, and external memory. © 2006 Wiley Periodicals, Inc. Random Struct. Alg., 2007

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