A Structure-preserving Clause Form Translation
Journal of Symbolic Computation
Resolution for quantified Boolean formulas
Information and Computation
On a generalization of extended resolution
Discrete Applied Mathematics - Special issue on the satisfiability problem and Boolean functions
Recovering and Exploiting Structural Knowledge from CNF Formulas
CP '02 Proceedings of the 8th International Conference on Principles and Practice of Constraint Programming
Bounded universal expansion for preprocessing QBF
SAT'07 Proceedings of the 10th international conference on Theory and applications of satisfiability testing
Nenofex: expanding NNF for QBF solving
SAT'08 Proceedings of the 11th international conference on Theory and applications of satisfiability testing
An AIG-Based QBF-solver using SAT for preprocessing
Proceedings of the 47th Design Automation Conference
Leveraging dominators for preprocessing QBF
Proceedings of the Conference on Design, Automation and Test in Europe
Clause elimination procedures for CNF formulas
LPAR'10 Proceedings of the 17th international conference on Logic for programming, artificial intelligence, and reasoning
CP'06 Proceedings of the 12th international conference on Principles and Practice of Constraint Programming
SAT'04 Proceedings of the 7th international conference on Theory and Applications of Satisfiability Testing
Effective preprocessing in SAT through variable and clause elimination
SAT'05 Proceedings of the 8th international conference on Theory and Applications of Satisfiability Testing
sQueezeBF: an effective preprocessor for QBFs based on equivalence reasoning
SAT'10 Proceedings of the 13th international conference on Theory and Applications of Satisfiability Testing
TACAS'10 Proceedings of the 16th international conference on Tools and Algorithms for the Construction and Analysis of Systems
Extended failed-literal preprocessing for quantified boolean formulas
SAT'12 Proceedings of the 15th international conference on Theory and Applications of Satisfiability Testing
Solving QBF with counterexample guided refinement
SAT'12 Proceedings of the 15th international conference on Theory and Applications of Satisfiability Testing
Bridging the gap between dual propagation and CNF-based QBF solving
Proceedings of the Conference on Design, Automation and Test in Europe
Recovering and utilizing partial duality in QBF
SAT'13 Proceedings of the 16th international conference on Theory and Applications of Satisfiability Testing
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Quantified Boolean formulas (QBF) provide a powerful framework for encoding problems from various application domains, not least because efficient QBF solvers are available. Despite sophisticated evaluation techniques, the performance of such a solver usually depends on the way a problem is represented. However, the translation to processable QBF encodings is in general not unique and may either introduce variables and clauses not relevant for the solving process or blur information which could be beneficial for the solving process. To deal with both of these issues, preprocessors have been introduced which rewrite a given QBF before it is passed to a solver. In this paper, we present novel preprocessing methods for QBF based on blocked clause elimination (BCE), a technique successfully applied in SAT. Quantified blocked clause elimination (QBCE) allows to simulate various structural preprocessing techniques as BCE in SAT. We have implemented QBCE and extensions of QBCE in the preprocessor bloqqer. In our experiments we show that preprocessing with QBCE reduces formulas substantially and allows us to solve considerable more instances than the previous state-of-the-art.