Fast pruning of geometric spanners

  • Authors:
  • Joachim Gudmundsson;Giri Narasimhan;Michiel Smid

  • Affiliations:
  • Department of Mathematics and Computing Science, TU Eindhoven, Eindhoven, The Netherlands;School of Computer Science, Florida International University, Miami, FL;School of Computer Science, Carleton University, Ottawa, Canada

  • Venue:
  • STACS'05 Proceedings of the 22nd annual conference on Theoretical Aspects of Computer Science
  • Year:
  • 2005

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Abstract

Let S be a set of points in ℝd. Given a geometric spanner graph, G = (S,E), with constant stretch factor t, and a positive constant ε, we show how to construct a (1+ε)-spanner of G with $\mathcal{O}(|S|)$ edges in time $\mathcal{O}(|E|+|S|{\rm log}|S|)$. Previous algorithms require a preliminary step in which the edges are sorted in non-decreasing order of their lengths and, thus, have running time Ω(|E| log |S|). We obtain our result by designing a new algorithm that finds the pair in a well-separated pair decomposition separating two given query points. Previously, it was known how to answer such a query in $\mathcal{O}({\rm log}|S|)$ time. We show how a sequence of such queries can be answered in $\mathcal{O}(1)$ amortized time per query, provided all query pairs are from a polynomially bounded range.