A Clause-Based Heuristic for SAT Solvers

  • Nachum Dershowitz
  • Ziyad Hanna
  • Alexander Nadel
Part of the Lecture Notes in Computer Science book series (LNCS, volume 3569)


We propose a new decision heuristic for DPLL-based propositional SAT solvers. Its essence is that both the initial and the conflict clauses are arranged in a list and the next decision variable is chosen from the top-most unsatisfied clause. Various methods of initially organizing the list and moving the clauses within it are studied. Our approach is an extension of one used in Berkmin, and adopted by other modern solvers, according to which only conflict clauses are organized in a list, and a literal-scoring-based secondary heuristic is used when there are no more unsatisfied conflict clauses. Our approach, implemented in the 2004 version of zChaff solver and in a generic Chaff-based SAT solver, results in a significant performance boost on hard industrial benchmarks.


Satisfying Assignment Partial Assignment Conjunctive Normal Form Formula Decision Heuristic Empty Clause 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


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Copyright information

© Springer-Verlag Berlin Heidelberg 2005

Authors and Affiliations

  • Nachum Dershowitz
    • 1
  • Ziyad Hanna
    • 2
  • Alexander Nadel
    • 1
    • 2
  1. 1.School of Computer ScienceTel Aviv UniversityRamat AvivIsrael
  2. 2.Design Technology GroupIntel CorporationHaifaIsrael

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