Differences between revisions 21 and 30 (spanning 9 versions)
Revision 21 as of 2005-06-27 22:27:33
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Revision 30 as of 2008-10-24 02:23:46
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Deletions are marked like this. Additions are marked like this.
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{{{#!latex2
$$Speedup = \frac{Performance~using~enhancement~when~possible}{Performance~without~enhancement}$$
}}}
<<latex($$Speedup = \frac{Performance~using~enhancement~when~possible}{Performance~without~enhancement}$$)>>
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[[latex2($$SpeedupOverall = \frac{Old~Execution~Time}{New~Execution~Time}$$)]] (1) [[latex($$SpeedupOverall = \frac{Old~Execution~Time}{New~Execution~Time}$$)]] (1)
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{{{#!latex2
$$New~Exec~Time = Old~Exec~Time \left( 1 - FractionEnhanced + \frac{FractionEnhanced}{SpeedupEnhanced}\right)$$
}}}
This gives a new Execution time of
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{{{
or

                       Execution Time affected by Improvement
New Execution Time = -------------------------------------- + Execution Time unaffected
                            Amount of Improvement (x times)
[[latex($$New~Exec~Time = Old~Exec~Time \left( 1 - FractionEnhanced + \frac{FractionEnhanced}{SpeedupEnhanced}\right)$$)]]
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                                     1
SpeedupOverall = --------------------------------------------
                                           FractionEnhanced
                 (1 - FractionEnhanced) + ------------------ )
                                           SpeedupEnhanced
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}}} [[latex($$SpeedupOverall=\left(\frac{1}{1-FractionEnhanced + \frac{FractionEnhanced}{SpeedupEnhanced}}\right)$$)]]

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<<latex($$Speedup = \frac{Performance~using~enhancement~when~possible}{Performance~without~enhancement}$$)>>

See SpeedUp

Notice that we are talking about the entire task here and that performance (speedup) is defined in terms of execution time! So we have to define the following:

latex($$SpeedupOverall = \frac{Old~Execution~Time}{New~Execution~Time}$$) (1)

This gives a new Execution time of

latex($$New~Exec~Time = Old~Exec~Time \left( 1 - FractionEnhanced + \frac{FractionEnhanced}{SpeedupEnhanced}\right)$$)

So we have

latex($$SpeedupOverall=\left(\frac{1}{1-FractionEnhanced + \frac{FractionEnhanced}{SpeedupEnhanced}}\right)$$)

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AmdahlsLaw (last edited 2020-01-23 23:15:20 by scot)