Author: Robert Hyatt
Date: 10:26:43 04/25/02
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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...
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