Improved on-the-Fly Livelock Detection

Abstract

Until recently, the preferred method of livelock detection was via LTL model checking, which imposes complex constraints on partial order reduction por, limiting its performance and parallelization. The introduction of the $\textsc{dfs}_{\textsc{fifo}}$ algorithm by Faragó et al. showed that livelocks can theoretically be detected faster, simpler, and with stronger por.

For the first time, we implement $\textsc{dfs}_{\textsc{fifo}}$ and compare it to the LTL approach by experiments on four established case studies. They show the improvements over the LTL approach: $\textsc{dfs}_{\textsc{fifo}}$ is up to 3.2 times faster, and it makes por up to 5 times better than with spin’s ndfs.

Additionally, we propose a parallel version of $\textsc{dfs}_{\textsc{fifo}}$, which demonstrates the efficient combination of parallelization and por. We prove parallel $\textsc{dfs}_{\textsc{fifo}}$ correct and show why it provides stronger guarantees on parallel scalability and por compared to LTL-based methods. Experimentally, we establish almost ideal linear parallel scalability and por close to the por for safety checks: easily an order of magnitude better than for LTL.