Industrial Strength Distributed Explicit State Model Checking

We present Preach, an industrial strength distributed explicit state model checker based on Murphi. The goal of this project was to develop a reliable, easy to maintain, scalable model checker that was compatible with the Murphi specification language. Preach is implemented in the concurrent functional language Erlang, chosen for its parallel programming elegance. We use the original Murphifront-end to parse the model description, a layer written in Erlang to handle the communication aspects of the algorithm, and also use Murphias a back-end for state expansion and to store the hash table. This allowed a clean and simple implementation, with the core parallel algorithms written in under 1000 lines of code. This paper describes the Preach implementation including the various features that are necessary for the large models we target. We have used Preach to model check an industrial cache coherence protocol with approximately 30 billion states. To our knowledge, this is the largest number published for a distributed explicit state model checker. Preach has been released to the public under an open source BSD license.