A New Partial Order Reduction Algorithm for Concurrent System Verification

Abstract

This paper presents a new partial order reduction algorithm called Two phase that is implemented in a verification tool, PV (Protocol Verifier). Two phase significantly reduces space and time requirements on many practically important protocols on which the partial order reduction algorithms implemented in previous tools (Godefroid 1995, Holzmann et aZ. 1994, Peled 1996 yield very little savings. This is primarily attributable to their use of a run-time proviso deciding which processes to run in a given state. Two phase avoids this proviso and follows a much simpler execution strategy that dramatically reduces the number of executions examined on a significant number of examples. We describe the Two phase algorithm, prove its correctness, and provide evidence of its superior performance on a number of examples including the directory based protocols of a multiprocessor under development.

Partial-order reduction and trail improvement in directed model checking

“…The detection of cycles without search stacks has been addressed. The Two-Phase algorithm [50] has been successfully used in partial-order reduction to reduce state space sizes for some protocol examples. The disadvantage of this algorithm is that it stores much information in a cache, which entails additional complexity.…”

Efficient Symbolic Model Checking for Process Algebras

“…The Two-Phase algorithm (presented in [10]) is a variant of the classical DFS algorithm with POR of [3,8]. It alternates between two distinct phases:…”

“…As shown in [10], the Two-Phase algorithm produces a reduced state space which is stuttering equivalent to the whole one, and therefore preserves CT L X properties [9].…”