A cut-off approach for bounded verification of parameterized systems.

The features in multi-threaded programs, such as recursion, dynamic creation and communication, pose a great challenge to formal verification. A widely adopted strategy is to verify tentatively a system with a smaller size, by limiting the depth of recursion or the number of replicated processes, to find errors without ensuring the full correctness. The model checking of parameterized systems, a parametric infinite family of systems, is to decide if a property holds in every size instance. There has been a quest for finding cut-offs for the verification of parameterized systems. The basic idea is to find a cut-off on the number of replicated processes or on the maximum length of paths needed to prove a property, standing a chance of improving verification efficiency substantially if one can come up with small or modest cut-offs. In this paper, a novel approach, called Forward Bounded Reachability Analysis (FBRA), based upon the cut-off on the maximum lengths of paths is proposed for the verification of parameterized systems. Experimental results show that verification efficiency has been significantly improved as a result of the introduction of our new cut-offs.