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Subject: Re: Fail high reductions

Author: Uri Blass

Date: 15:10:04 07/01/03

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On July 01, 2003 at 17:34:47, Russell Reagan wrote:

>From "Fail High Reductions by Rainer Feldmann"
>"...a fail high node is a node 'v' with a search window of [alpha,beta] at which
>a static evaluation function 'c' produces a cutoff. The FHR-algorithm reduces
>the search depths at these fail high nodes thus searching their subtrees with
>less effort."
>Their subtrees? I thought fail high nodes didn't have subtrees, and that you
>return beta at a fail high node. I must be misunderstanding something. Could
>someone give a simple explaination of how fail high reductions work?

If I understand correctly the idea is that you evaluate a position that is not a
leaf and the static evaluation is not in the window of [alpha,beta] so you
reduce the depth.

Example:when you analyze e4 Nf6 Qh5 Nxh5 your evaluation is a queen advantage
for black and you can be almost sure of fail high so instead of searching to
remaining depth of 7 you may decide to search to a smaller depth.


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