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Solving Tasks with Fewer Registers Than Processes

Authors Eli Gafni , Giuliano Losa , Michel Raynal , Gadi Taubenfeld

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Subject Classification

ACM Subject Classification
  • Theory of computation → Distributed algorithms
Keywords
  • Asynchrony
  • Read/write registers
  • Wait-freedom
  • Tasks
  • Covering argument
  • Lower bound
  • Space complexity
  • Anonymous Processes
  • Anonymous Memory

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Abstract

This paper studies distributed-computing tasks through the lens of space complexity in the read/write wait-free model, defined as the number of multi-reader-multi-writer atomic read/write registers needed to solve a task using a wait-free algorithm. Surprisingly, even though the read/write wait-free model is at the foundation of distributed computing, previous work on space complexity has focused on synchronization primitives stronger than read/write registers or on weaker progress conditions.
The paper reveals that the read/write wait-free model offers a rich space-complexity landscape: (1) assuming non-anonymous processes, it shows that there is an infinite hierarchy of tasks of increasing space complexity; (2) it shows that space complexity separates anonymous from non-anonymous memory; (3) regardless of process or register anonymity, it exhibits a task of space complexity two, which is the minimal non-trivial space complexity; (4) finally, it shows that subcases of the adopt-commit task have different space complexity in non-anonymous memory under bounded wait-freedom.

Cite As Get BibTex

Eli Gafni, Giuliano Losa, Michel Raynal, and Gadi Taubenfeld. Solving Tasks with Fewer Registers Than Processes. In 29th International Conference on Principles of Distributed Systems (OPODIS 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 361, pp. 21:1-21:21, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025) https://doi.org/10.4230/LIPIcs.OPODIS.2025.21

Author Details

Eli Gafni
  • UCLA, Los Angeles, CA, USA
Giuliano Losa
  • Stellar Development Foundation, San Francisco, CA, USA
Michel Raynal
  • Univ. Rennes, Inria, CNRS, IRISA, Rennes, France
Gadi Taubenfeld
  • Reichman University, Herzliya, Israel

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