Block Me If You Can!

We present a method for automatic verification of systems with a parameterized number of communicating processes, such as mutual exclusion protocols or agreement protocols. To that end, we present a powerful abstraction framework that uses an efficient and precise symbolic encoding of (infinite) sets of configurations. In particular, it generalizes downward-closed sets that have successfully been used in earlier approaches to parameterized verification. We show experimentally the efficiency of the method, on various examples, including a fine-grained model of Szymanski’s mutual exclusion protocol, whose correctness, to the best of our knowledge, has not been proven automatically by any other existing methods.