Re: Inconsistent timing results of multithreaded program on an SMP machine.
From: Con Kolivas
Date: Sun Nov 20 2005 - 05:39:49 EST
On Sun, 20 Nov 2005 21:35, Muli Ben-Yehuda wrote:
> On Sun, Nov 20, 2005 at 09:28:13PM +1100, Con Kolivas wrote:
> > Ok I've had a look at the actual program now ;) Are you timing the time
> > it takes to completion of everything?
> > This part of your program:
> > for (i= 0; i<8; i++)
> > pthread_join(tid[i], NULL);
> > Cares about the order the threads finish. Do you think this might be
> > affecting your results?
> I don't see why it should matter. Depending on the order the threads
> finish, we will always wait in pthread_join until the last one
> finishes, and then do between 0 and 7 more pthread_joins that should
> return immediately (since the last one has already finished).
If it was instant it shouldn't matter. I'm aware of that in theory, but there
have certainly been reports of pthread_join taking quite a while happening in
a sort of lazy/sloppy way. I don't know why this is the case but I wondered
if it was showing up here.
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