Compression of Propositional Resolution Proofs via Partial Regularization

This paper describes two algorithms for the compression of propositional resolution proofs. The first algorithm, RecyclePivotsWithIntersection, performs partial regularization, removing an inference η when it is redundant in the sense that its pivot literal already occurs as the pivot of another inference located below in the path from η to the root of the proof. The second algorithm, LowerUnits, delays the resolution of (both input and derived) unit clauses, thus removing (some) inferences having the same pivot but possibly occurring also in different branches of the proof.