Author: Robert Hyatt
Date: 14:50:32 08/26/05
Go up one level in this thread
On August 26, 2005 at 17:21:57, Uri Blass wrote: >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 by the time I get to _that_ position I could guarantee you every move has been tried millions of times. :)
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