Author: Uri Blass
Date: 01:32:48 04/07/04
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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 Even if the idea was correct then I think that it is private case of ETC but maybe I do not understand ETC. A possible idea is to detect the pattern from1 to1 from2 to2 to1 from1 in the last 3 moves and to try to2 from2 first in case that it is legal because it gives draw score even without search. it can be also in case of null moves(null move is a1a1) If you detect a1a1 b1c3 a1a1 then the first move to search is c3b1. Note that in that case it is important not to save the move in the hash tables or in the killer moves and I think that even changing the history is bad. I did not try it in movei but I may do it. I remember that Junior used that idea too much and there was a case when it showed a wrong draw score based on 3 moves because it even did not care to check if the 4th move that cause a repetition is legal and it was illegal. Uri
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