Author: Andreas Herrmann
Date: 11:47:24 04/25/02
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On April 25, 2002 at 13:49:42, Dann Corbit wrote: >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. Hi Dann, yes that was also my next idea to implement it. Then it costs nearby nothing on time. Do you know some positions which are very well for testing this. Andreas
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