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Subject: Re: Trivial alfa-beta question

Author: Robert Hyatt

Date: 14:24:39 02/18/06

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On February 18, 2006 at 13:30:09, Jouni Uski wrote:

>The book "Schach am PC" from 1995 says, that alfa-beta reduces evaluated
>positions with 5 * sqrt (positions). Also some example values are given
>like:
>
>         positions      alfa-beta positions
>8 ply    6.5e12         13e6
>9 ply    2.6e14         80e6
>
>Are these values outdated? Has there been significant improvements later? I
>think today's engines get x plys with much smaller nodes.
>
>Jouni


Pure minimax:

nodes = (branching factor) ^ depth

alpha/beta

nodes = 2 * (branching factor) ^ depth/2

If you add null-move you are no longer purely searching a minimax tree to fixed
depth, so the old formulas do not apply.  If you factor in other forward pruning
ideas, they become even more inaccurate.



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