A General Lock-Free Algorithm for Parallel State Space Construction

Verification via model-checking is a very demanding activity in terms of computational resources. While there are still gains to be expected from algorithmic improvements, it is necessary to take advantage of the advances in computer hardware to tackle bigger models. Recent improvements in his area take the form of multiprocessor and multicore architectures with access to large memory space. We address the problem of generating the state space of finite-state transition systems, often a preliminary step for model-checking. We propose a novel algorithm for enumerative state space construction targeted at shared memory systems. Our approach relies on the use of two data structures: a shared Bloom filter to coordinate the state space exploration distributed among several processors and local dictionaries to store the states. The goal is to limit synchronization overheads and to increase the locality of memory access without having to make constant use of locks to ensure data integrity. Bloom filters have already been applied for the probabilistic verification of systems, they are compact data structures used to encode sets, but in a way that false positives are possible, while false negatives are not. We circumvent this limitation and propose an original multiphase algorithm to perform exhaustive, deterministic, state space generations. We assess the performance of our algorithm on different benchmarks and compare our results with the solution proposed by Inggs and Barringer.