Author: Uri Blass
Date: 14:21:57 08/26/05
Go up one level in this thread
On August 26, 2005 at 17:08:52, Robert Hyatt wrote: >On August 26, 2005 at 16:58:21, Uri Blass wrote: > >>On August 26, 2005 at 14:54:32, Robert Hyatt wrote: >> >>>On August 26, 2005 at 14:21:34, Alvaro Jose Povoa Cardoso wrote: >>> >>>>Hi, >>>>some of you compare the number of times a move failed high to the number o times >>>>the same move failed low in order to decide if a move can be reduced one ply. >>>>I've tested this and also tested using the actual values of the history table >>>>(using of course another history table for fail lows). >>>>I couldn't reach a conclusion though. >>>>What is your experience on this? >>>> >>>>best regards, >>>>Alvaro >>> >>> >>>My first thought is that the number of "fail lows" is irrelevant. What you >>>really want to avoid is a reduction on a move that might fail high. Any move >>>will fail low in some situations, but you want to handle the "typical" case >>>correctly and not reduce if there is a reasonable chance the reduction will hide >>>something. >> >>I think that it is relevant. >> >>If a move was never tried and never had an option to fail low then you do not >>want to reduce it. >> > >Chances of that happening is about zero. There are only a finite (and small) >number of different possible moves in the game. "All the right moves" (PhD >thesis by Ebeling) illustrated this. I agree that there is a finite number of moves but I am sure that there are moves that are never tried during the first seconds of a search simply because you need many moves to make them legal. It does not mean that in the first time that they are legal they should be pruned. For example [D]r1b3k1/1pp5/8/8/8/8/6PP/4KB1R w - - 0 1 I doubt if you will find a move like Kf6-g7 at small depths but it does not mean that the move should be pruned and this move can be logical in supporting passed pawns. Uri
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