Aina Niemetz

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A certificate of (un)satisfiability for a quantified Boolean formula (QBF) represents concrete assignments to the variables, which act as witnesses for its truth value. Certificates are highly requested for practical applications of QBF like formal verification and model checking. We present an integrated set of tools realizing resolution-based certificate(More)
Effectively parallelizing SAT solving is an open and important issue. The current state-of-the-art is based on parallel portfolios. This technique relies on running multiple solvers on the same instance in parallel. As soon as one instance finishes, the entire run stops. Several successful systems even use Plain Parallel Portfolio (PPP), where the(More)
—Bit-blasting is the main approach for solving word-level constraints in SAT Modulo Theories (SMT) for bit-vector logics. However, in practice it often reaches its limits, even if combined with sophisticated rewriting and simplification techniques. In this paper, we extended a recently proposed alternative based on stochastic local search (SLS) and improve(More)
Satisfiability Modulo Theories (SMT) is essential for many applications in computer-aided verification. A recent SMT solving approach based on stochastic local search for the theory of quantifier-free fixed-size bit-vectors proved to be quite effective on hard satisfiable instances , particularly in the context of symbolic execution. However, it still(More)
—This paper serves as solver description for our SMT solver Boolector, entering the SMT Competition 2015 in three different configurations. We only list important differences to the earlier version of Boolector that participated in the SMT Competition 2014 [2]. For further information we refer to [3] or source code. OVERVIEW This year's version of Boolector(More)
—This paper serves as solver description for our SMT solver Boolector entering the SMT Competition 2014 in three different configurations. We only list important differences to the earlier version of Boolector that participated in the SMT Competition 2012 [2]. For further information we refer to [2] or source code. OVERVIEW This year's version of Boolector(More)
—Lemmas on demand is an abstraction/refinement technique for procedures deciding Satisfiability Modulo Theories (SMT), which iteratively refines full candidate models of the formula abstraction until convergence. In this paper, we introduce a dual propagation-based technique for optimizing lemmas on demand by extracting partial candidate models via don't(More)