Author: Tony Werten
Date: 04:30:32 07/02/03
Go up one level in this thread
On July 02, 2003 at 05:47:27, martin fierz wrote: >On July 01, 2003 at 18:24:43, Omid David Tabibi wrote: > >>On July 01, 2003 at 18:19:44, Ralph Stoesser wrote: >> >>>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. >> >>... which is called verified null-mvoe pruning :) > > >to me FHR sounds very similar to ProbCut / MultiProbCut, except that it uses the >static eval at a node instead of a shallow search. Not quite. FHR reduces depth when static eval>>beta and then continues search as normal. Probcut uses a shallow search (several actually ) to generate a cutoff. Tony > > >>> >>>Ralph
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