Author: Omid David Tabibi
Date: 08:09:21 07/02/03
Go up one level in this thread
On July 02, 2003 at 10:49:41, Gerd Isenberg wrote: >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. FHR reduces the depth if static eval >= beta. I think you are confusing FHR with verified null-move pruning; the latter reduces the depth when null_move_score >= beta (and cuts off immediately if null_move_score >= beta in the subtree of a fail-high reported node). > >Regards, >Gerd
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