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We consider the problem of implementing randomized wait-free consensus from max registers under the assumption of an oblivious adversary. We show that max registers solve m-valued consensus for arbitrary m in expected O(log^* n) steps per process, beating the Omega(log m/log log m) lower bound for ordinary registers when m is large and the best previously known O(log log n) upper bound when m is small. A simple max-register implementation based on double-collect snapshots translates this result into an O(n log n) expected step implementation of m-valued consensus from n single-writer registers, improving on the best previously-known bound of O(n log^2 n) for single-writer registers.
@InProceedings{aspnes_et_al:LIPIcs.DISC.2019.1,
author = {Aspnes, James and Er, He Yang},
title = {{Consensus with Max Registers}},
booktitle = {33rd International Symposium on Distributed Computing (DISC 2019)},
pages = {1:1--1:9},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-126-9},
ISSN = {1868-8969},
year = {2019},
volume = {146},
editor = {Suomela, Jukka},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.DISC.2019.1},
URN = {urn:nbn:de:0030-drops-113088},
doi = {10.4230/LIPIcs.DISC.2019.1},
annote = {Keywords: consensus, max register, single-writer register, oblivious adversary, shared memory}
}