Black Box Unfolding with Local First Search

McMillan's unfolding approach to the reachability problem in 1-safe Petri nets and its later improvements by Esparza-Romer-Vogler have proven in practice as a very effective method to avoid stateexplosion. This method computes a complete finite prefix of the infinite branching process of a net. On the other hand,the Local First Search approach (LFS) was recently introduced as a new partial order reduction technique which characterizes a restricted subset of configurations that need to be explored to check local properties. In this paper we amalgamate the two approaches: We combine the reduction criterion of LFS with the notions of an adequate order and cutoff events essential to the unfolding approach. As a result,our new LFS method computes a reduced transition system without the problem of state duplication (present in the original LFS). Since it works for any transition system with an independence relation,this black box partial unfolding remains more general than the unfolding of Petri nets. Experiments show that the combination gives improved reductions compared to the original LFS.