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how to calculate the speedup of performance in percentage

Sara Brown
Ranch Hand

Joined: Feb 22, 2012
Posts: 55
assume performance with multithread


core 1
thread 1 = 5 sec

core 2
thread 1 = 3 sec
thread 2 = 2 sec


how to calculate the speedup of performance in percent?


i am really confused. what to take to calculate and how? please, thank you.

fred rosenberger
lowercase baba
Bartender

Joined: Oct 02, 2003
Posts: 11168
    
  16

We don't have enough information. It would depend on how you define "speedup". It would also depend on whether in the "core 2" example, did they run sequentially? Did they run interleaved and the time listed is how long each thread took by itself?

Personally, I don't see what difference it makes how long each thread took - what matters is how long the total job took. If thread 1 starts and runs to completion before thread 2 can start, then you really haven't saved anything.

Multi-threading isn't a panacea. It won't always save you time. Think about the old saying that "Nine women can't have a baby in one month". Some tasks can't be split up, so no matter how many threads you have, you won't save any time.


There are only two hard things in computer science: cache invalidation, naming things, and off-by-one errors
Campbell Ritchie
Sheriff

Joined: Oct 13, 2005
Posts: 38045
    
  22
fred rosenberger wrote: . . . "Nine women can't have a baby in one month". . . .
Isaac Asimov, in one of his “Robot” stories, wrote:If one and a half chickens lay one and a half eggs in one and a half days, how many eggs will nine chickens lay in nine days?
Look for Amdahl's_law.
 
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