QBF Reasoning on Real-World Instances

During the recent years, the development of tools for deciding Quantified Boolean Formulas (QBFs) has been accompanied by a steady supply of real-world instances, i.e., QBFs originated by translations from application domains. Instances of this kind showed to be challenging for current state-of-the-art QBF solvers, while the ability to deal effectively with them is necessary to foster adoption of QBF-based reasoning in practice. In this paper we describe three reasoning techniques that we implemented in our solver QUBE++ to increase its performances on real-world instances coming from formal verification and planning domains. We present experimental results that witness the contribution of each technique and the better performances of QUBE++ with respect to other state-of-the-art QBF solvers. The effectiveness of QUBE++ is further confirmed by experiments run on challenging real-world SAT instances, where QUBE++ turns out to be competitive with respect to current state-ofthe-art SAT solvers.