Author: Dann Corbit
Date: 10:49:42 04/25/02
Go up one level in this thread
On April 25, 2002 at 13:26:43, Robert Hyatt wrote: >On April 25, 2002 at 12:39:36, J. Wesley Cleveland 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. >> >>That seems like far too much. Are you reducing the search depth again for the >>second nullmove and only doing it when the first nullmove causes a cutoff? You >>might also not want to do it too near the leafs, i.e. if the first nullmove goes >>directly into your quiescence search. > > >One simple test... determine how often, in normal positions, the _second_ null- >move search fails high. Whenever it does, the the first null-move search fails >low and is useless. that is probably where the cost is being exposed... > >In zug positions, the second fail high will cause the first to fail low, which >prevents zug problems. But if it also causes a large number of normal positions >to fail this test as well, then it is losing part of the advantage of null-move >in general... I had a notion about double null move -- Implement double null move in the place where normally you will just turn null move off [except for check]. Use your regular null move algorithm as always, but when conditions indicate null move is not a good idea, switch to double null move.
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