This paper presents a formal verification algorithm for finding errors in models of complex concurrent systems. The algorithm improves explicit guided model checking by applying the Empirical Bayes method to revise heuristic estimates of the distance from a given state to an error state. Guided search using the revised estimates finds errors with less search effort than the original estimates.

Abstract. This paper presents a disk-based explicit state model checking algorithm that uses an approach called layered duplicate detection. In this approach, states encountered during a breadth-first traversal of the graph of the transition system are stored in memory according to the layer of the graph in which they are first encountered. With this layered organization of memory, transition locality is exploited by checking only the most recent layers for duplicates. In RAM, exploiting transition locality in this way saves time. In external memory, it saves space. In addition, a layered structure allows an easy method of counterexample reconstruction in disk-based model checking. We prove a worst-case linear bound on the redundant work performed by our approach. Experimental results indicate that average case redundant work is much better than the worst-case. The implemented model checker has been used to verify a transition system that required more than 275 GBs of disk storage.

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