Diversification and determinism in local search for satisfiability

  • Authors:
  • Chu Min Li;Wen Qi Huang

  • Affiliations:
  • LaRIA, Université de Picardie Jules Verne, Amiens Cedex 1, France;Huazhong university of science and technology, Wuhan, China

  • Venue:
  • SAT'05 Proceedings of the 8th international conference on Theory and Applications of Satisfiability Testing
  • Year:
  • 2005

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Abstract

The choice of the variable to flip in the Walksat family procedures is always random in that it is selected from a randomly chosen unsatisfied clause c. This choice in Novelty or R-Novelty heuristics also contains some determinism in that the variable to flip is always limited to the two best variables in c. In this paper, we first propose a diversification parameter for Novelty (or R-Novelty) heuristic to break the determinism in Novelty and show its performance compared with the random walk parameter in Novelty+. Then we exploit promising decreasing paths in a deterministic fashion in local search using a gradient-based approach. In other words, when promising decreasing paths exist, the variable to flip is no longer selected from a randomly chosen unsatisfied clause but in a deterministic fashion to surely decrease the number of unsatisfied clauses. Experimental results show that the proposed diversification and the determinism allow to significantly improve Novelty (and Walksat).