SMTSampler: Efficient Stimulus Generation from Complex SMT Constraints

Stimulus generation is an essential part of hardware verification, being at the core of widely applied constrained-random verification techniques. However, as verification problems get more and more complex, so do the constraints which must be satisfied. In this context, it is a challenge to efficiently generate random stimuli which can achieve a good coverage of the design space. We developed a new technique SMTSAMPLER which can sample random solutions from Satisfiability Modulo Theories (SMT) formulas with bit-vectors, arrays, and uninterpreted functions. The technique uses a small number of calls to a constraint solver in order to generate up to millions of stimuli. Our evaluation on a large set of complex industrial SMT benchmarks shows that SMTSAMPLER can handle a larger class of SMT problems, outperforming state-of-the-art constraint sampling techniques in the number of samples produced and the coverage of the constraint space.