Author: Uri Blass
Date: 11:43:08 04/25/02
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On April 25, 2002 at 14:08:51, Dann Corbit wrote: >On April 25, 2002 at 03:15:14, Uri Blass wrote: > >>On April 25, 2002 at 02:54:03, Andreas Herrmann wrote: >> >>>Hi, >>> >>>I want to implement double nullmove in my chess engine again. Now i'm searching >>>for Zugzwang postions, which should be solved by double nullmove instead of >>>normal nullmove. >>>Another question: How much time costs the double null move in the average. >>>I have tested it in some positions, and my engine needs about 30 to 40 percent >>>more time for the same search depth. Is that normal or is that to much. >>> >>>have a nice day >>>Andreas >>> >>>http://wbholmes.de >> >>I do not know but it is a bad idea to be 30-40% slower only for detecting >>zunzwangs. >> >>I think that there are better ways than double null move to detect zunzwangs. > >However, there isn't a better way for processing them. It still gives a big >speedup for these searches. No I mean to say that there is a simple way to detect zunzwangs without the problem of being 30-40% slower. Note that small zunzwangs of 0.1 pawn are not important and it is important only to care about big zunzwangs. Here is one simple way(I did not try it in my program because I do not think that it is very important for strength): if the remaining depth is smaller than 7 do not detect zunzwangs. In other cases compare the scores with white to move and the score with black to move when you reduce the depth by 7 plies. only if this comparison suggest a zunzwang of at least 1/2 pawn do not use null move pruning. I guess that 7 is too big and you can take even smaller number without the risk of being 30-40% slower. Uri
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