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Subject: Re: Fail high reductions

Author: Gerd Isenberg

Date: 07:49:41 07/02/03

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On July 02, 2003 at 07:22:00, Georg v. Zimmermann wrote:

>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

Hi George,

If i remember well, Rainer Feldmann's FHR is based on the NullMove observation.
Instead of foreward pruning, FHR reduce depth if a NullMove fail high occurs.

Regards,
Gerd



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