A thread-safe Term Library

TL;DR

This paper introduces a thread-safe Term Library with a novel busy-forbidden protocol, enabling efficient multi-reader/single-writer access, verified by model checking, and demonstrating significant performance improvements in practical applications.

Contribution

The paper presents a new busy-forbidden protocol for thread-safe term libraries, verified by model checking, and shows its efficiency and practical benefits in state space generation.

Findings

Little overhead compared to sequential versions

Outperforms sequential versions on two processors

Enables substantial speed ups in state space generation

Abstract

Terms are one of the fundamental mathematical concepts in computing. E.g. every expression characterisable by a context free grammar is a term. We developed a thread-safe Term Library. The biggest challenge is to implement hyper-efficient multi-reader/single-writer mutual exclusion for which we designed the new busy-forbidden protocol. Model checking is used to show both the correctness of the protocol and the Term Library. Benchmarks show this Term Library has little overhead compared to sequential versions and outperforms them already on two processors. Using the new library in an existing state space generation tool, very substantial speed ups can be obtained.