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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.
 Fall '09

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