This paper introduces a novel, fast atomic-snapshot protocol for asynchronous message-passing systems. In the process of defining what ``fast'' means exactly, we spot a few interesting issues that arise when conventional time metrics are applied to long-lived asynchronous algorithms. We reveal some gaps in latency claims made in earlier work on snapshot algorithms, which hamper their comparative time-complexity analysis. We then come up with a new unifying time-complexity metric that captures the latency of an operation in an asynchronous, long-lived implementation. This allows us to formally grasp latency improvements of our atomic-snapshot algorithm with respect to the state-of-the-art protocols: optimal latency in fault-free runs without contention, short constant latency in fault-free runs with contention, the worst-case latency proportional to the number of active concurrent failures, and constant, amortized latency.
@article{arxiv.2408.02562,
title = {Asynchronous Latency and Fast Atomic Snapshot},
author = {João Paulo Bezerra and Luciano Freitas and Petr Kuznetsov and Matthieu Rambaud},
journal= {arXiv preprint arXiv:2408.02562},
year = {2025}
}