Author: Tord Romstad
Date: 01:22:16 04/07/04
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On April 07, 2004 at 04:15:10, Rémi Coulom wrote: >On April 07, 2004 at 04:06:38, Tord Romstad wrote: > >>The following idea is still untested, but unless I am missing something it >>is guaranteed to reduce the number of nodes without any risk. The idea is >>fairly obvious, and I am sure some of you are already using it, but I still >>don't think it is widely known. >> >>At a node where the remaining depth is sufficiently big that a null move >>would not drop us directly into the qsearch, and beta > DRAW_SCORE, avoid >>doing a null move search if the move leading to the node was a reversible >>move. The point is that we know that the null move search is a waste of >>time in this case. After the null move, the opponent can just reverse >>his move, with a repetition draw score. >> >>Tord > >If the opponent reverses his move, the position will not be a repetition, >because the player to move will not be the same. You're right, of course. It seems clear that I should do some basic tests before I post, or at least refrain from posting so early in the morning. I still think that similar observations can be used to reduce the tree size, though (but not without risk). In some cases, it might make sense to search the reversal of the move to a reduced depth, or to prune it completely. This is just the most trivial special case of a more general idea I am thinking about, but because of the fiasco in my first post this morning it is probably better if I don't try to give a detailed description of the general idea yet. Tord
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