On the dilation spectrum of paths, cycles, and trees

  • Authors:
  • Rolf Klein;Christian Knauer;Giri Narasimhan;Michiel Smid

  • Affiliations:
  • Institute of Computer Science I, Universität Bonn, Bonn, Germany;Institute of Computer Science, Freie Universität Berlin, Berlin, Germany;School of Computing and Information Sciences, Florida International University, Miami, FL, USA;School of Computer Science, Carleton University, Ottawa, Ontario, Canada

  • Venue:
  • Computational Geometry: Theory and Applications
  • Year:
  • 2009

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Abstract

Let G be a graph with n vertices which is embedded in Euclidean space R^d. For any two vertices of G, their dilation is defined to be the ratio of the length of a shortest connecting path in G to the Euclidean distance between them. In this paper, we study the spectrum of the dilation, over all pairs of vertices of G. For paths, cycles, and trees in R^2, we present O(n^3^/^2^+^@e)-time randomized algorithms that compute, for a given value @k1, the exact number of vertex pairs of dilation at most @k. Then we present deterministic algorithms that approximate the number of vertex pairs of dilation at most @k to within a factor of 1+@e. They run in O(nlog^2n) time for paths and cycles, and in O(nlog^3n) time for trees, in any constant dimension d.