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Subject: Re: New crap statement ? Perpetuum mobile

Author: Bruce Moreland

Date: 09:28:34 10/05/01

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On October 04, 2001 at 20:14:30, Robert Hyatt wrote:

>On October 04, 2001 at 18:41:14, Bruce Moreland wrote:

>>Two units of work is more than twice as fast as six units, so this particular
>>case is super-linear, barely.  You can make it more so by making the arrays
>>longer.
>
>
>Nope.  I modify my serial algorithm to match your parallel algorithm.  Then it
>is not super-linear at all.  I find it after two compares, one on the first
>element, one on the last.  The parallel algorithm finds it after two compares
>also, but they are done in parallel in one cycle.  Speedup = 2.0...

Bob, I would be an idiot if I said that you couldn't get the same speedup by
modifying the serial algorithm.  I'm not saying that.  I'm saying that you might
be able to see improbable speedups when modifying a serial algorithm by making
it run in parallel.

I'd be a fool to argue that a parallel algorithm will beat a serial algorithm
plus a guy with a compiler and some time to modify code.

If you are now saying that a super-linear speedup could be possible, but that a
guy with a compiler could fix the serial algorithm to make it run better, we
aren't arguing about anything.

bruce




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