Local consistency and SAT-solvers

  • Authors:
  • Justyna Petke;Peter Jeavons

  • Affiliations:
  • Oxford University Computing Laboratory, Oxford, UK;Oxford University Computing Laboratory, Oxford, UK

  • Venue:
  • CP'10 Proceedings of the 16th international conference on Principles and practice of constraint programming
  • Year:
  • 2010

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Abstract

In this paper we show that the power of using k-consistency techniques in a constraint problem is precisely captured by using a particular inference rule, which we call positive-hyper-resolution, on the direct Boolean encoding of the CSP instance. We also show that current clause-learning SAT-solvers will deduce any positive-hyper-resolvent of a fixed size from a given set of clauses in polynomial expected time. We combine these two results to show that, without being explicitly designed to do so, current clause-learning SAT-solvers efficiently simulate k-consistency techniques, for all values of k. We then give some experimental results to show that this feature allows clause-learning SAT-solvers to efficiently solve certain families of CSP instances which are challenging for conventional CP solvers.