Competitive routing in the half-θ6-graph

  • Authors:
  • Prosenjit Bose;Rolf Fagerberg;André van Renssen;Sander Verdonschot

  • Affiliations:
  • Carleton University;University of Southern Denmark;Carleton University;Carleton University

  • Venue:
  • Proceedings of the twenty-third annual ACM-SIAM symposium on Discrete Algorithms
  • Year:
  • 2012

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Abstract

We present a deterministic local routing scheme that is guaranteed to find a path between any pair of vertices in a half-θ6-graph whose length is at most 5/√3 = 2.886... times the Euclidean distance between the pair of vertices. The half-θ6-graph is identical to the Delaunay triangulation where the empty region is an equilateral triangle. Moreover, we show that no local routing scheme can achieve a better competitive spanning ratio thereby implying that our routing scheme is optimal. This is somewhat surprising because the spanning ratio of the half-θ6-graph is 2. Since every triangulation can be embedded in the plane as a half-θ6-graph using O(log n) bits per vertex coordinate via Schnyder's embedding scheme (SODA 1990), our result provides a competitive local routing scheme for every such embedded triangulation.