chapter1-AppendixA-m4-ziavras

# Culler d patterson ucb s ziavras how summarize suite

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Unformatted text preview: han Bandwidth • • • Secure transfers require involvement of the O/S in the form of software interrupts/exceptions/traps overhead per transfer Long messages amortize overhead; overhead bigger part of short messages DMA-like transfers: same overhead shared by many individual data items Transfers may be delayed until enough data has been accumulated for a bulk transfer Some material is adapted from D. Culler & D. Patterson (UCB) S. Ziavras How Summarize Suite Performance (1/4) • Arithmetic average of execution time of all pgms1 – But they vary by 4X in speed, so some would be more important than others in arithmetic average • Could add a weight per program, but how pick weight? 2 – Different companies want different weights for their products • Using the arithmetic mean of performances: WRONG • SPECRatio: Normalize execution times to reference computer, yielding a ratio proportional to performance: time on reference computer SPECRatio = time on computer being rated Some material is adapted from D. Culler & D. Patterson (UCB) S. Ziavras Mean Computer Performance • Similar problems with n computers and 1 program, or 1 computer and n exclusive execution modes (such as vector, sequential, parallel), or 1 computer and a suite of n programs • Assume n programs & 1 computer programs computer • 1 Arithmetic mean time of a given computer for a given set of n programs (ti for program i) T= 1/n Σi=1n ti • 2 Weighted arithm. mean time (fi: weight of program i) T*= Σi=1n fi*ti Some material is adapted from D. Culler & D. Patterson (UCB) S. Ziavras Arithmetic Mean Performance Arithmetic Mean Performance • Ri: execution rate for program i, for 1 ≤ i ≤ n Ri ~ 1/Ti = a R 1 n i • If π ={f i, for i=1,2,...,n} are the program weights for i=1 are the program weights – Weighted arithmetic mean execution rate n R a = ∑ (f i • R i ) * W WRONG N R n ∑ i= i =1 It’s proportional to the sum of the inverses of execution times times 1/R*...
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