World Library  
Flag as Inappropriate
Email this Article

Parallel slowdown

Article Id: WHEBN0015167068
Reproduction Date:

Title: Parallel slowdown  
Author: World Heritage Encyclopedia
Language: English
Subject: Parallel computing, Parallel algorithm, Yield method, Cache invalidation, Memory semantics (computing)
Collection: Analysis of Parallel Algorithms, Parallel Computing
Publisher: World Heritage Encyclopedia

Parallel slowdown

A diagram of the program runtime (shown in blue) and program speed-up (shown in red) of a real-world program with sub-optimal parallelization. The dashed lines indicate optimal parallelization–linear increase in speedup and linear decrease in program runtime. Note that eventually the runtime actually increases with more processors (and the speed-up likewise decreases). This is parallel slowdown.

Parallel slowdown is a phenomenon in parallel computing where parallelization of a parallel algorithm beyond a certain point causes the program to run slower (take more time to run to completion).

Parallel slowdown is typically the result of a communications bottleneck. As more processing nodes are added, each processing node spends progressively more time doing communication than useful processing. At some point, the communications overhead created by adding another processing node surpasses the increased processing power that node provides, and parallel slowdown occurs.

Parallel slowdown occurs when the algorithm requires significant communication, particularly of intermediate results. Some problems, known as embarrassingly parallel problems, do not require such communication, and thus are not affected by slowdown.

This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.

Copyright © World Library Foundation. All rights reserved. eBooks from Project Gutenberg are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.