Boolean satisfiability (SAT) has played a key role in diverse areas spanning testing, formal verification, planning, optimization, inferencing and the like. Apart from the classical problem of checking boolean satisfiability, the problems of generating satisfying uniformly at random, and of counting the total number of satisfying assignments have also attracted significant theoretical and practical interest over the years. Prior work offered heuristic approaches with very weak or no guarantee of performance, and theoretical approaches with proven guarantees, but poor performance in practice.

We propose a novel approach based on limited-independence hashing that allows us to design algorithms for both problems, with strong theoretical guarantees and scalability extending to thousands of variables. Based on this approach, we present two practical algorithms, UniWit: a near uniform generator and ApproxMC: the first scalable approximate model counter, along with reference implementations. Our algorithms work by issuing polynomial calls to SAT solver. We demonstrate scalability of our algorithms over a large set of benchmarks arising from different application domains.