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Subject: Re: Branching factor and parallel search efficiency

Author: Anthony Cozzie

Date: 09:46:47 07/16/04

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On July 16, 2004 at 08:59:42, Tord Romstad wrote:

>Which influence does the branching factor of a two-player, zero-sum game have
>on the efficiency of a parallel search?  Is the speedup when using multiple
>processors independent of the branching factor, or does the speedup increase
>(decrease?) when the branching factor increases?  Intuitively I would expect
>the speedup to increase with the branching factor, but I have no experience
>with parallel search.
>
>In case it is not clear, when talking about "branching factor" above, I am not
>talking about what is commonly called the "effective branching factor" (which is
>typically in the range 2-3 for a chess program using recursive null move
>pruning),
>but about the average number of legal moves (around 30-40 in a typical chess
>middle game).
>
>Tord

From what I can tell, the most important thing is being able to split anywhere
in the tree.  This is why Cray Blitz got better speedups than Crafty does now.

I'll be putting this theory to the text pretty soon :)

anthony



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