Complexity analysis of heuristic CSP search algorithms

  • Authors:
  • Igor Razgon

  • Affiliations:
  • Computer Science Department, University College Cork, Ireland

  • Venue:
  • CSCLP'05 Proceedings of the 2005 Joint ERCIM/CoLogNET international conference on Constraint Solving and Constraint Logic Programming
  • Year:
  • 2005

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Abstract

CSP search algorithms are exponential in the worst-case. A trivial upper bound on the time complexity of CSP search algorithms is O*(dn), where n and d are the number of variables and the maximal domain size of the underlying CSP, respectively. In this paper we show that a combination of heuristic methods of constraint solving can reduce the time complexity. In particular, we prove that the FC-CBJ algorithm combined with the fail-first variable ordering heuristic (FF) achieves time complexity of O*((d – 1)n), where n and d are the number of variables and the maximal domain size of the given CSP, respectively. Furthermore, we show that the combination is essential because neither FC-CBJ alone nor FC with FF achieve the above complexity. The proposed results are interesting because they establish connection between theoretical and practical approaches to CSP research.