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Subject: Re: Fail high reductions

Author: Georg v. Zimmermann

Date: 04:22:00 07/02/03

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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?

IMHO Rainer Feldmann uses bad terminology. A fail high node is - at least by my
definition - indeed a node where one subtree returns a value above beta, you
therefor "fail high" and return (value or beta, depending on if you use fail
soft).
What he intends to say is probably : " a fail high REDUCTION node is a node 'v'
with a search window of [alpha,beta] at which
>a static evaluation function 'c' produces a cutoff. "

The technic he describes sounds a lot more error prone than null move to me, at
least in tactical situations.

Georg



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