Proofs and refutations

Proofs and Refutations, and Z3

Z3 [3] is a state-of-the-art Satisfiability Modulo Theories (SMT) solver freely available from Microsoft Research. It solves the decision problem for quantifier-free formulas with respect to combinations of theories, such as arithmetic, bit-vectors, arrays, and uninterpreted functions. Z3 is used in various software analysis and test-case generation projects at Microsoft Research and elsewhere....

Scaling Relational Inference Using Proofs and Refutations

Many inference problems are naturally formulated using hard and soft constraints over relational domains: the desired solution must satisfy the hard constraints, while optimizing the objectives expressed by the soft constraints. Existing techniques for solving such constraints rely on efficiently grounding a sufficient subset of constraints that is tractable to solve. We present an eager-lazy g...

An Examination of Counterexamples in Proofs and Refutations

Automatic proofs and refutations for higher-order logic

This thesis describes work on two components of the interactive theorem prover Isabelle/HOL that generate proofs and counterexamples for higher-order conjectures by harnessing external first-order reasoners. Our primary contribution is the development of Nitpick, a counterexample generator that builds on a first-order relational model finder based on a Boolean satisfiability (SAT) solver. Nitpi...

Resolution Refutations and Propositional Proofs with Height-Restrictions

Height restricted resolution (proofs or refutations) is a natural restriction of resolution where the height of the corresponding proof tree is bounded. Height restricted resolution does not distinguish between treeand sequence-like proofs. We show that polylogarithmic-height resolution is strongly connected to the bounded arithmetic theory S 2(α). We separate polylogarithmic-height resolution ...