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Between SAT and UNSAT: The Fundamental Difference in CDCL SAT

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Book cover Theory and Applications of Satisfiability Testing -- SAT 2015 (SAT 2015)

Part of the book series: Lecture Notes in Computer Science ((LNTCS,volume 9340))

Abstract

The way CDCL SAT solvers find a satisfying assignment is very different from the way they prove unsatisfiability. We propose an explanation to the difference by identifying direct connections to the workings of some of the most important elements in CDCL solvers: the effects of restarts and VSIDS, and the roles of learned clauses. We give a wide range of concrete evidence that highlights the varying effects and roles of these elements. As a result, this paper also sheds a new light on the internal workings of CDCL. Based on our reasoning on the difference in solver behaviors, we present several ideas for optimizing SAT solvers for either SAT or UNSAT instances. We then show that we can achieve improvements on both SAT and UNSAT at the same time by judiciously exploiting the difference. We have implemented a hybrid idea mixing two different restart strategies on top of our new solver COMiniSatPS and observed substantial performance improvement.

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Authors and Affiliations

  1. New York University, New York, NY, 10012, USA

    Chanseok Oh

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  1. Chanseok Oh
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Correspondence to Chanseok Oh .

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Editors and Affiliations

  1. Algorithms, University of Texas, Austin, Texas, USA

    Marijn Heule

  2. Trusted Systems Research Group, Fort Meade, Texas, USA

    Sean Weaver

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Oh, C. (2015). Between SAT and UNSAT: The Fundamental Difference in CDCL SAT. In: Heule, M., Weaver, S. (eds) Theory and Applications of Satisfiability Testing -- SAT 2015. SAT 2015. Lecture Notes in Computer Science(), vol 9340. Springer, Cham. https://doi.org/10.1007/978-3-319-24318-4_23

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  • DOI: https://doi.org/10.1007/978-3-319-24318-4_23

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  • Publisher Name: Springer, Cham

  • Print ISBN: 978-3-319-24317-7

  • Online ISBN: 978-3-319-24318-4

  • eBook Packages: Computer ScienceComputer Science (R0)

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