Author: Robert Hyatt
Date: 14:08:52 08/26/05
Go up one level in this thread
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. One way to see this is to set all history values to -1, then increment them normally when they result in a fail high, and if they are -1, set them to 0 if they don't. I'd bet almost 100% of moves will have a value >= 0, meaning they were tried in the search. When we started searching millions of moves per second, untried moves became very rare... >If you know that a move failed low many times but did not fail high then it >seems more safe to reduce it. > >Uri
This page took 0 seconds to execute
Last modified: Thu, 15 Apr 21 08:11:13 -0700
Current Computer Chess Club Forums at Talkchess. This site by Sean Mintz.