Bisimulator 2.0: An On-the-Fly Equivalence Checker based on Boolean Equation Systems

Equivalence checking is a classical verification method determining if a finite-state concurrent system (protocol) satisfies its desired external behaviour (service) by comparing their underlying labeled transition systems (LTSs) modulo an appropriate equivalence relation. Local (or on-the- fly) equivalence checking explores the synchronous product of the LTSs incrementally, allowing an efficient detection of errors in complex systems. In this paper, we consider the technique based on translating the equivalence checking problem in terms of the local resolution of a Boolean equation system (BES). We propose two enhancements of this technique in the case of equivalent LTSs: a new, faster BES encoding of weak equivalence relations, and a new local BES resolution algorithm with a good average complexity. These enhancements were incorporated into the BISIMULATOR 2.0 equivalence checker of the CADP toolbox, and led to significant performance improvements.