Verifying Propositional Unsatisfiability: Pitfalls to Avoid

  • Allen Van Gelder
Conference paper
Part of the Lecture Notes in Computer Science book series (LNCS, volume 4501)


The importance of producing a certificate of unsatisfiability is increasingly recognized for high performance propositional satisfiability solvers. The leading solvers develop a conflict graph as the basis for deriving (or “learning”) new clauses. Extracting a resolution derivation from the conflict graph is theoretically straightforward, but it turns out to have some surprising practical pitfalls (as well as the unsurprising problem that resolution proofs can be extremely long). These pitfalls are exposed, solutions are presented, and analyzed for worse cases. Dramatic improvements on industrial benchmarks are demonstrated.


Conflict Graph Unit Clause Resolution Proof Antecedent Clause Clause Learning 
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 Berlin Heidelberg 2007

Authors and Affiliations

  • Allen Van Gelder
    • 1
  1. 1.University of California, Santa Cruz CA 95060USA

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