Exact and approximate bandwidth

  • Authors:
  • Marek Cygan;Marcin Pilipczuk

  • Affiliations:
  • -;-

  • Venue:
  • Theoretical Computer Science
  • Year:
  • 2010

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Abstract

In this paper we gather several improvements in the field of exact and approximate exponential time algorithms for the Bandwidth problem. For graphs with treewidth t we present an O(n^O^(^t^)2^n) exact algorithm. Moreover, for any two positive integers k=2,r=1, we present a (2kr-1)-approximation algorithm that solves Bandwidth for an arbitrary input graph in O^*(k^n^(^k^-^1^)^r) time and polynomial space where by O^* we denote the standard big O notation but omitting polynomial factors. Finally, we improve the currently best known exact algorithm for arbitrary graphs with an O(4.383^n) time and space algorithm. In the algorithms for the small treewidth we develop a technique based on the Fast Fourier Transform, parallel to the Fast Subset Convolution techniques introduced by Bjorklund et al. This technique can be also used as a simple method of finding a chromatic number of all subgraphs of a given graph in O^*(2^n) time and space, what matches the best known results.