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From: Frank Mori Hess (frank.hess_at_[hidden])
Date: 2008-05-14 17:07:46

Hash: SHA1

On Wednesday 14 May 2008 16:47 pm, James Sutherland wrote:
> Any thoughts on what is chewing up the extra time then? Isn't the
> total time the correct measure here? Is the difference between the
> "real" time and the "system" time due to the join_all?

There is no extra time, or not much. You seem to be misinterpreting the
output of the "time" command. The real time is the elapsed time in the real
world. The sys plus user time is the time the all cpus spent executing the
program in total, which you would expect to remain roughly constant.

If 2 cpus each spent 1 second running the program in parallel, the real time
would be 1 second and the system plus user time would be 2 seconds.

If one cpu each spent 2 seconds running the program, the real time would be 2
seconds and the system plus user time would still be 2 seconds.

Oh, I also made my version loop 10 times as long, which is why it takes almost
10 seconds.

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