Author: Ralph Stoesser
Date: 15:19:44 07/01/03
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On July 01, 2003 at 18:10:04, Uri Blass 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? > >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. > >Uri I think that's right. This is similar to the Nullmove technique, but not that radical, because you only reduce the search depth instead of cutoff the whole subtree. Ralph
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