Author: Ed Schröder
Date: 02:06:04 08/27/05
Go up one level in this thread
On August 26, 2005 at 23:11:18, Robert Hyatt wrote: >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... History Reductions is a working idea Bob, you should definitely try it. Ed
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