Partimes - Amdahl Parallel Performance Mohamed Iskandarani December 2 2008 Amdahl Outline Amdahl Amdahl Amdahl’s law • Definitions • t s P

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Unformatted text preview: Amdahl Parallel Performance Mohamed Iskandarani December 2, 2008 Amdahl Outline Amdahl Amdahl Amdahl’s law • Definitions: • t s ( P ) execution time of serial portion on P processors • t p ( P ) execution time of parallel portion on P processors • Speedup = time on 1 processors time on P processors = t s ( 1 ) + t p ( 1 ) t s ( P ) + t p ( P ) • Assumptions 1. uniform serial time: t s ( 1 ) = t s ( P ) = t s . 2. parallel overhead is negligeable: t 1 ( P ) = Pt p ( P ) Amdahl Amdahl’s law S = t s + t p ( 1 ) t s + tp ( 1 ) P = 1 ts ts + t 1 ( p ) + tp ( 1 ) P [ ts + tp ( 1 )] (1) = 1 β A + 1- β A P (2) β A = t s t s + t 1 ( P ) = serial fraction (3) Amdahl Amdahl’s law for fixed β A 200 400 600 800 1000 1200 10 20 30 40 50 60 70 80 90 100 β A =0.01 β A =0.10 β A =0.50 S Amdahl Amdahl’s law for fixed P 10-7 10-6 10-5 10-4 10-3 10-2 10-1 10 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 S max /P P=128 P=256 P=512 P=1024 Amdahl Gustafson’s law S = t s + Pt p ( P ) t s + t...
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This note was uploaded on 01/08/2012 for the course MSC 321 taught by Professor Staff during the Fall '08 term at University of Miami.

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Partimes - Amdahl Parallel Performance Mohamed Iskandarani December 2 2008 Amdahl Outline Amdahl Amdahl Amdahl’s law • Definitions • t s P

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