Reducing Symmetries to Generate Easier SAT Instances

  • Authors:
  • Jian Zhang;Zhuo Huang

  • Affiliations:
  • Laboratory of Computer Science, Institute of Software, Chinese Academy of Sciences, Beijing 100080, China;Laboratory of Computer Science, Institute of Software, Chinese Academy of Sciences, Beijing 100080, China

  • Venue:
  • Electronic Notes in Theoretical Computer Science (ENTCS)
  • Year:
  • 2005

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Abstract

Finding countermodels is an effective way of disproving false conjectures. In first-order predicate logic, model finding is an undecidable problem. But if a finite model exists, it can be found by exhaustive search. The finite model generation problem in the first-order logic can also be translated to the satisfiability problem in the propositional logic. But a direct translation may not be very efficient. This paper discusses how to take the symmetries into account so as to make the resulting problem easier. A static method for adding constraints is presented, which can be thought of as an approximation of the least number heuristic (LNH). Also described is a dynamic method, which asks a model searcher like SEM to generate a set of partial models, and then gives each partial model to a propositional prover. The two methods are analyzed, and compared with each other.