A fast and simple algorithm for bounds consistency of the all different constraint

  • Authors:
  • Alejandro Lopez-Ortiz;Claude-Guy Quimper;John Tromp;Peter Van Beek

  • Affiliations:
  • School of Computer Science, University of Waterloo, Waterloo, Canada;School of Computer Science, University of Waterloo, Waterloo, Canada;CWI, Amsterdam, Netherlands;School of Computer Science, University of Waterloo, Waterloo, Canada

  • Venue:
  • IJCAI'03 Proceedings of the 18th international joint conference on Artificial intelligence
  • Year:
  • 2003

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Abstract

In constraint programming one models a problem by stating constraints on acceptable solutions. The constraint model is then usually solved by interleaving backtracking search and constraint propagation. Previous studies have demonstrated that designing special purpose constraint propagators for commonly occurring constraints can significantly improve the efficiency of a constraint programming approach. In this paper we present a fast, simple algorithm for bounds consistency propagation of the alldifferent constraint. The algorithm has the same worst case behavior as the previous best algorithm but is much faster in practice. Using a variety of benchmark and random problems, we show that our algorithm outperforms existing bounds consistency algorithms and also outperforms--on problems with an easily identifiable property-state-ofthe-art commercial implementations of propagators for stronger forms of local consistency.