Wait-free test-and-set

Yehuda Afek, Eli Gafni, John Tromp, Paul M.B. Vitanyi

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review


This paper presents an economical, randomized, wait-free construction of an n-process test-and-set bit from read write registers. The test-and-set shared object has two atomic operations, test&set, which atomically reads the bit and sets its value to 1, and the reset operation that resets the bit to 0. We identify two new complexity measures by which to evaluate waitfree algorithms: (a) The amount of randomness used, and (b) ‘Parallel-Time’—the maximum sequential depth of an execution (i.e. longest chain of operations that must precede each other). The previously best known algorithm for n-process test-and-set [Her91] takes an expected Ω(n2) parallel time, and Ω(n4) sequential time per operation, and Ω(n2log n) space per processor. In contrast, our direct implementation improves this on all counts by using O(log n) coin flips, O(log n) parallel time, O(n) sequential time, per operation, and O(n) space per processor. Thus the question on the difference in the expected complexity of randomized constructions of concurrent objects from read/write registers is raised.

Original languageEnglish
Title of host publicationDistributed Algorithms - 6th International Workshop, WDAG 1992, Proceedings
EditorsAdrian Segall, Shmuel Zaks
PublisherSpringer Verlag
Number of pages10
ISBN (Print)9783540561880
StatePublished - 1992
Event6th International Workshop on Distributed Algorithms, WDAG 1992 - Haifa, Israel
Duration: 2 Nov 19924 Nov 1992

Publication series

NameLecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)
Volume647 LNCS
ISSN (Print)0302-9743
ISSN (Electronic)1611-3349


Conference6th International Workshop on Distributed Algorithms, WDAG 1992


FundersFunder number
National Science FoundationDCR84-51396


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