Multi-resolution on compressed sets of clauses

The paper presents a system based on new operators for handling sets of propositional clauses represented by means of ZBDDs (zero-suppressed binary decision diagrams). The high compression power of such data structures allows efficient encodings of structured instances. A specialized operator for the distribution of sets of clauses is introduced and used for performing multi-resolution on clause sets. Cut eliminations between sets of clauses of exponential size may then be performed using polynomial size data structures. The ZREs system, a new implementation of the Davis-Putnam procedure (M. Davis and H. Putnam, 1960), solves two hard problems for resolution, that are currently out of the scope of the best SAT provers