Learning back-clauses in SAT

  • Authors:
  • Ashish Sabharwal;Horst Samulowitz;Meinolf Sellmann

  • Affiliations:
  • IBM Watson Research Center, Yorktown Heights, NY;IBM Watson Research Center, Yorktown Heights, NY;IBM Watson Research Center, Yorktown Heights, NY

  • Venue:
  • SAT'12 Proceedings of the 15th international conference on Theory and Applications of Satisfiability Testing
  • Year:
  • 2012

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Abstract

In [3], SAT conflict analysis graphs were used to learn additional clauses, which we refer to as back-clauses. These clauses may be viewed as enabling the powerful notion of "probing": Back-clauses make inferences that would normally have to be deduced by setting a variable deliberately the other way and observing that unit propagation leads to a conflict. We show that short-cutting this process can in fact improve the performance of modern SAT solvers in theory and in practice. Based on out numerical results, it is suprising that back-clauses, proposed over a decade ago, are not yet part of standard clause-learning SAT solvers.