Oh-RAM! one and a half round atomic memory

Theophanis Hadjistasi, Nicolas Nicolaou, Alexander A. Schwarzmann

Research output: Chapter in Book/Report/Conference proceedingConference contribution

11 Scopus citations


Implementing atomic read/write shared objects in a message-passing system is an important problem in distributed computing. Considering that communication is the most expensive resource, efficiency of read and write operations is assessed primarily in terms of the needed communication and the associated latency. Attiya, Bar-Noy, and Dolev established that two communication round-trip phases involving in total four message exchanges are sufficient to implement atomic operations when a majority of processors are correct. Subsequently Dutta et al. showed that one round involving two communication exchanges is sufficient as long as the system adheres to certain constraints with respect to crashes on the number of readers and writers in the system. It was also observed that three exchanges are sufficient in some settings. This extended abstract presents work that explores algorithms where operations are able to complete in three message exchanges without imposing constraints on the number of participants, i.e., the aim is One and half Round Atomic Memory, hencethenameOh-RAM!Recently Hadjistasi et al. showed that three-exchange implementations are impossible in the MWMR (multi-writer/multi-reader) setting. This paper shows that this is achievable in the SWMR (single-writer/multi-reader) setting, and also achievable for read operations in the MWMR setting by “sacrificing” the performance of write operations. In particular, a SWMR implementation is presented, where reads complete in three and writes complete in two exchanges. Next, a MWMR implementation is given, where reads involve three and writes involve four exchanges. In light of the impossibility result these algorithms are optimal in terms of the number of communication exchanges. Both algorithms are then refined to allow some reads to complete in just two exchanges. These algorithms are evaluated and compared using the NS3 simulator with different topologies and operation loads.

Original languageEnglish (US)
Title of host publicationNetworked Systems - 5th International Conference, NETYS 2017, Proceedings
EditorsAmr El Abbadi, Benoit Garbinato
PublisherSpringer Verlag
Number of pages16
ISBN (Print)9783319596464
StatePublished - Jan 1 2017
Externally publishedYes
Event5th International Conference on Networked Systems, NETYS 2017 - Marrakech, Morocco
Duration: May 17 2017May 19 2017

Publication series

NameLecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)
Volume10299 LNCS
ISSN (Print)0302-9743
ISSN (Electronic)1611-3349


Other5th International Conference on Networked Systems, NETYS 2017

ASJC Scopus subject areas

  • Theoretical Computer Science
  • Computer Science(all)


Dive into the research topics of 'Oh-RAM! one and a half round atomic memory'. Together they form a unique fingerprint.

Cite this