Verifying RUP Proofs of Propositional Unsatisfiability

The importance of producing a certi cate of unsatis ability is increasingly recognized for high performance propositional satis ability solvers. The leading solvers develop a con ict graph as the basis for deriving (or \learning") new clauses. Extracting a resolution derivation from the con ict graph is theoretically straightforward, but resolution proofs can be extremely long. Several other certi cate formats have been proposed and studied, but the veri ers for these formats are beyond any hope of automated veri cation in their own rights. However, they enjoy the advantages of being easy to implement and reasonable in their space requirements. This paper reports progress on developing a practical system for formal veri cation of a more compact certi cate format, and experimental comparisons are presented. A format called RUP (for Reverse Unit Propagation) is introduced and two implementations are evaluated. This method is an extension of con ict clause proofs introduced by Goldberg and Novikov.