Calculating-Confluence Compositionally

τ -confluence is a reduction technique used in enumerative model-checking of labeled transition systems to avoid the state explosion problem. In this paper, we propose a new on-the-fly algorithm to calculate partial τ -confluence, and propose new techniques to do so on large systems in a compositional manner. Using information inherent in the way a large system is composed of smaller systems, we show how we can deduce partial τ -confluence in a computationally cheap manner. Finally, these techniques are applied to a number of case studies, including the rel/REL atomic multicast protocol.