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Analyzing OpenMP Parallelization Capabilities and Finding Thread Handling Optimums
University West, Department of Engineering Science, Division of Mathematics, Computer and Surveying Engineering.
University West, Department of Engineering Science, Division of Mathematics, Computer and Surveying Engineering.
2018 (English)Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
Abstract [sv]

Utmaningar i modern processortillverkning begränsar klockfrekvensen för enkeltrådiga applikationer, vilket har resulterat i utvecklingen av flerkärniga processorer. Dessa processorer tillåter flertrådig exekvering och ökar därmed prestandan. För att undersöka möjligheterna med parallell exekvering används en Fast Fourier Transform algoritm där trådprestanda mäts för olika skapade tester med varierande problemstorlekar. Dessa tester körs på tre testsystem och använder olika sökalgoritmer för att dynamiskt justera antalet trådar vid exekvering. Denna prestanda jämförs sedan med den högsta möjliga prestanda som kan fås genom Brute-Forcing. Testerna använder OpenMP-instruktioner för att specificera antalet trådar som finns tillgängliga för programexekvering. För mindre problemstorlekar resulterar färre antal trådar i högre prestanda. Motsatsen gäller för större problemstorlekar, där många trådar föredras istället. Denna rapport visar att användning av alla tillgängliga trådar för ett system inte är optimalt i alla lägen då det finns en tydlig koppling mellan problemstorlek och det optimala antalet trådar för maximal prestanda. Detta gäller för alla tre testsystem som omfattas av rapporten. Metodiken som har använts för att skapa testerna har gjort det möjligt att dynamiskt kunna justera antalet trådar vid exekvering. Rapporten visar också att dynamisk justering av antalet trådar inte passar för alla typer av applikationer.

Abstract [en]

As physical limitations limit the clock frequencies available for a single thread, processor vendors increasingly build multi-core systems with support for dividing processes across multiple threads for increased overall processing power. To examine parallelization capabilities, a fast fourier transform algorithm is used to benchmark parallel execution and compare brute-forced optimum with results from various search algorithms and scenarios across three different testbed systems. These algorithms use OpenMP instructions to directly specify number of threads available for program execution. For smaller problem sizes the tests heavily favour fewer threads, whereas the larger problems favour the native 'maximum' thread count. Several algorithms were used to compare ways of searching for the optimum thread values at runtime. We showed that running at maximum threads is not always the most optimum choice as there is a clear relationship between the problem size and the optimal thread-count in the experimental setup across all three machines. The methods used also made it possible to identify a way to dynamically adjust the thread-count during runtime of the benchmark, however it is not certain all applications would be suitable for this type of dynamic thread assignment

Place, publisher, year, edition, pages
2018. , p. 6
Keywords [en]
OpenMP, Parallelization Capabilities, Dynamic, Thread Handling, Performance
Keywords [sv]
OpenMP, Parallell exekvering, Dynamisk trådhantering, Prestanda, Optimum
National Category
Computer Systems
Identifiers
URN: urn:nbn:se:hv:diva-12752Local ID: EXD500OAI: oai:DiVA.org:hv-12752DiVA, id: diva2:1232235
Subject / course
Computer enigeering
Educational program
Course
Supervisors
Examiners
Available from: 2018-07-26 Created: 2018-07-11 Last updated: 2019-06-05Bibliographically approved

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