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Re: maximum theoretical speedup with dual quad processors
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Re: maximum theoretical speedup with dual quad processors


  • Subject: Re: maximum theoretical speedup with dual quad processors
  • From: Michael Ash <email@hidden>
  • Date: Tue, 3 Feb 2009 00:29:13 -0500

On Mon, Feb 2, 2009 at 11:30 PM, Peter Duniho <email@hidden> wrote:
> On Feb 1, 2009, at 8:37 PM, Michael Ash wrote:
>
>> Thanks to both you and Rob for repeating the experiment. Interesting
>> that it's so variable. On my computer it would occasionally require
>> several million to crash, but most of the time it explodes within the
>> first few hundred thousand.
>
> I've been testing your code too.  The first time I ran it, it crashed after
> 1,150,000 operations had been added.  But the second time, more than two
> hours and 40 million operations later, it was still running fine.  I've had
> a couple more attempts where it went well over 1 million without problem.
>
> I'm going to keep trying, but it looks very hard to reproduce on my system
> (MacBook Pro Core 2 Duo 2.33Ghz, Leopard 10.5.6).

I have a theory that more cores results in more danger, which would
fit this particular data point.

> Just for clarification, what kind of "explode" happens on your computer (and
> the other respondents, if they have that information)?
>
> On my computer, the one time I saw it crash, it was an
> NSInvalidArgumentException, complaining that in "-[MyOperation start]" the
> "receiver has already started or finished".  I'm wondering if this is the
> exception everyone sees, or if the actual exception varies from one
> execution of the program to the next.

That exception is what I get as well. While I was building the test
case I also saw some cases of double-frees (the objc runtime message
saying that you're freeing an object already destroyed, I forget the
exact wording and i don't have it handy here), but I think that was
only if I stuck a periodic waitUntilAllOperationsAreFinished in the
loop.

Mike
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References: 
 >Re: maximum theoretical speedup with dual quad processors (From: Michael Ash <email@hidden>)
 >Re: maximum theoretical speedup with dual quad processors (From: Michael Ash <email@hidden>)
 >Re: maximum theoretical speedup with dual quad processors (From: Peter Duniho <email@hidden>)

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