Author: Robert Hyatt
Date: 07:27:04 08/27/05
Go up one level in this thread
On August 27, 2005 at 05:06:04, Ed Schröder wrote: >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 It's definitely on my list of things to try... When Bruce and I were playing with the "reduction" idea several years ago, the one thing that was missing was a "semi-intelligent" way of excluding certain moves from the reduction process...
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