Author: Daniel Shawul
Date: 06:25:44 11/17/03
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On November 17, 2003 at 08:25:09, Tord Romstad wrote: >On November 17, 2003 at 07:30:59, Daniel Shawul wrote: > >>you are right,i meant deeper? Do you know any good place sir? >>i have found rebel's programming >>topics(http://members.home.nl/matador/chess840.htm) but you know >>they evaluate each node of the tree,which is quite costy for my program. > >Without evaluating interior nodes, how are you going to do any static >forward pruning or reductions at all? ofcourse I evaluate the nodes I want to razor.But rebel evaluates "all" the nodes to do further reductions.The programmer of rebel suggests drastic changes have to be made to use his reduction methods. > >>Also I tried to reduce the search depth by 1, if score + margin < alpha >>for depths greater than 3. > >Techniques like this seem to be very common (even in strong programs like >Rebel), but I am becoming more and more convinced that they are >fundamentally unsound. The problem is that you may encounter the same >position somewhere else in the search tree where the value of alpha is >different. When you look up the old search results in the hash table, >you get a search inconsistency. > I totally agree with you! >IMHO, it is a sounder idea to base forward pruning, extension and reduction >decisions on how each move affects the different components of the evaluation >function. As an example, you could consider the following idea: > >In a position where one of the pieces for the side to move is hanging, >reduce all moves which satisfies all of the following criterions: > >1. The move is not a capture. >2. The move is not a check. >3. The move does not defend the hanging piece, nor bring the hanging > piece into safety. >4. The move does not threaten any of the enemy pieces. >5. The move does not increase the pressure on the opponent's king. >6. The move does not increase the passed pawn evaluation (for instance > by advancing a passed pawn, or by supporting an unblocked advanced > passed pawn by a rook or a king). > >Tord
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