Author: Robert Hyatt
Date: 20:11:18 08/26/05
Go up one level in this thread
On August 26, 2005 at 21:03:07, Uri Blass wrote: >On August 26, 2005 at 17:50:32, Robert Hyatt wrote: > >>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. :) > >Even if you use statistics about all the game and not only about specific search >I do not think that every move has been tried millions of times because white >king from f6 to g7 is not something that you try in the opening when the white >king is at e1 or g1 and stupid lines when the king go forward to the direction >of g7 usually pruned by null move pruning. > >Uri Most don't do history like that. Usually it is just a 12 bit index <from><to>. So it doesn't differentiate between a king move from f6 go g7, and a bishop/queen move from f6 to g7...
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