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Subject: Re: Question about the speed improvement from simple multi programs

Author: Robert Hyatt

Date: 19:05:51 04/21/01

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On April 21, 2001 at 13:55:34, Dan Andersson wrote:

>Using root splitting, a scheme similar to the one you propose one gets about the
>square root of the number of processors.
>
>Regards Dan Andersson


That sounds too high for today's programs. IE the _first_ branch searched
typically takes 50-80% of the total search time.  If you search two moves
at the root at the same time, they will _both_ take about that long.  And
so far you have zero speed-up.  They will then search the remaining 20-50%
of the time in parallel, giving a very minimal speedup. The very first version
of Cray Blitz did this, and with 4 cpus the best we ever got was about 1.5
times faster.  In some positions it would get 2x faster, in some almost no
speedup...



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