Lightweight relevance filtering for machine-generated resolution problems

Irrelevant clauses in resolution problems increase the search space, making proofs hard to find in a reasonable amount of processor time. Simple relevance filtering methods, based on counting symbols in clauses, improve the success rate for a variety of automatic theorem provers and with various initial settings. We have designed these techniques as part of a project to link automatic theorem provers to the interactive theorem prover Isabelle. We have tested them for problems involving thousands of clauses, which yield poor results without filtering. Our methods should be applicable to other tasks where the resolution problems are produced mechanically and where completeness is less important than achieving a high success rate with limited processor time.