Nathan Wetzler

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The DRAT-trim tool is a satisfiability proof checker based on the new DRAT proof format. Unlike its predecessor, DRUP-trim, all presently known SAT solving and preprocessing techniques can be validated using DRAT-trim. Checking time of a proof is comparable to the running time of the proof-producing solver. Memory usage is also similar to solving memory(More)
We present a mechanically-verified proof checker developed with the ACL2 theorem-proving system that is general enough to support the growing variety of increasingly complex satisfiability (SAT) solver techniques, including those based on extended resolution. A common approach to assure the correctness of SAT solvers is to emit a proof of unsatisfiability(More)
An effective SAT preprocessing technique is using symmetrybreaking predicates, i.e., auxiliary clauses that guide a solver away from needless exploration of isomorphic sub-problems. Although symmetrybreaking predicates have been in use for over a decade, it was not known how to express them in proofs of unsatisfiability. Consequently, results obtained by(More)
Several proof formats have been used to verify refutations produced by satisfiability (SAT) solvers. Existing formats are either costly to check or hard to implement. This paper presents a practical approach that facilitates checking of unsatisfiability results in a time similar to proof discovery by embedding clause deletion information into clausal(More)
Satisfiability (SAT) solvers —and software in general— sometimes have serious bugs. We mitigate these effects by validating the results. Today’s SAT solvers emit proofs that can be checked with reasonable efficiency. However, these checkers are not trivial and can have bugs as well. We propose to check proofs using a formally verified program that adds(More)
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