how to calculate the speedup of performance in percentage

[Sara Brown]

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]

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.

[Campbell Ritchie]

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.