chapter1-AppendixA-m4-ziavras

Culler d patterson ucb 1 ri s ziavras weighted

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Unformatted text preview: a doesn’t represent actual time represent actual time Some material is adapted from D. Culler & D. Patterson (UCB) S. Ziavras Harmonic Mean Performance Harmonic Mean Performance • Ti=1/Ri: mean execution time per instr. for program i • Arithmetic mean execution time per instr. mean execution time per instr 1 Ta = n n n 1 ∑ Ti = n i =1 ∑ i =1 1 Ri • Harmonic mean execution rate across n programs 1 Rh = = Ta n n ∑ i =1 Some material is adapted from D. Culler & D. Patterson (UCB) 1 Ri S. Ziavras Weighted Harmonic Mean Execution Rate Weighted Harmonic Mean Execution Rate R * h = 1 n ∑ i =1 fi Ri Related correctly to execution times correctly to execution times Some material is adapted from D. Culler & D. Patterson (UCB) S. Ziavras How How Summarize Suite Performance (2/4) • If program SPECRatio on Computer A is 1.25 times bigger than Computer B, then then ExecutionT ime reference SPECRatio 1 . 25 = SPECRatio A B ExecutionT ime A = ExecutionT ime reference ExecutionT ime B ExecutionT ime B Performanc e A = = ExecutionT ime A Performanc e B • Note that when comparing 2 computers as a ratio, execution times on the reference computer drop out, so choice of reference computer is irrelevant Some material is adapted from D. Culler & D. Patterson (UCB) S. Ziavras How Summarize Suite Performance (3/4) • Since ratios, proper mean is geometric mean (SPECRatio unitless, so arithmetic mean meaningless) GeometricM ean = n n ∏ SPECRatio i i =1 1. Geometric mean of the ratios is the same as the th th ratio of the geometric means 2. Ratio of geometric means = Geometric mean of performance ratios ⇒ choice of reference computer is irrelevant! • These two points make geometric mean of ratios attractive to summarize performance Some material is adapted from D. Culler & D. Patterson (UCB) S. Ziavras Some material is adapted from D. Culler & D. Patterson (UCB) S. Ziavras How Summarize Suite Performance (4/4) • Question: Does a single mean well summarize performance of programs in b...
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This document was uploaded on 02/09/2014.

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