Trading-Off SAT Search and Variable Quantifications for Effective Unbounded Model Checking

Interpolant-based model checking has been shown effective on large verification instances, as it efficiently combines automated abstraction and fixed-point checks. On the other hand, methods based on variable quantification have proved their ability to remove free inputs, thus projecting the search space over state variables. In this paper we propose an integrated approach combining the abstraction power of interpolation with techniques relying on AIG and/or BDD representations of states, supporting variable quantification and fixed-point checks. The underlying idea of this combination is to adopt AIG- or BDD-based quantifications to limit and restrict the search space (and the complexity) of the interpolant-based approach. The exploited strategies, individually well-known, are integrated with a new flavor, specifically designed to improve their effectiveness on large verification instances. Experimental results, oriented to hard-to-solve verification problems, show the robustness of our approach.