A Decomposition Technique for Max-CSP

  • Authors:
  • Hachémi Bennaceur;Christophe Lecoutre;Olivier Roussel

  • Affiliations:
  • Université Lille-Nord de France, Artois, F-62307 Lens-CRIL, F-62307 Lens-CNRS UMR 8188, F-62307 Lens-IUT de Lens-bennaceur@cril.univ-artois.fr;Université Lille-Nord de France, Artois, F-62307 Lens-CRIL, F-62307 Lens-CNRS UMR 8188, F-62307 Lens-IUT de Lens-lecoutre@cril.univ-artois.fr;Université Lille-Nord de France, Artois, F-62307 Lens-CRIL, F-62307 Lens-CNRS UMR 8188, F-62307 Lens-IUT de Lens-roussel@cril.univ-artois.fr

  • Venue:
  • Proceedings of the 2008 conference on ECAI 2008: 18th European Conference on Artificial Intelligence
  • Year:
  • 2008

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Abstract

The objective of the Maximal Constraint Satisfaction Problem (Max-CSP) is to find an instantiation which minimizes the number of constraint violations in a constraint network. In this paper, inspired from the concept of inferred disjunctive constraints introduced by Freuder and Hubbe, we show that it is possible to exploit the arc-inconsistency counts, associated with each value of a network, in order to avoid exploring useless portions of the search space. The principle is to reason from the distance between the two best values in the domain of a variable, according to such counts. From this reasoning, we can build a decomposition technique which can be used throughout search in order to decompose the current problem into easier sub-problems. Interestingly, this approach does not depend on the structure of the constraint graph, as it is usually proposed. Alternatively, we can dynamically post hard constraints that can be used locally to prune the search space. The practical interest of our approach is illustrated, using this alternative, with an experimentation based on a classical branch and bound algorithm, namely PFC-MRDAC.