Author: Ricardo Gibert
Date: 16:50:21 04/25/02
Go up one level in this thread
On April 25, 2002 at 17:13:41, José Carlos wrote: >On April 25, 2002 at 15:27:26, Robert Hyatt wrote: > >>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. >> >> >>If it was easy to identify positions where a null-move might cause problems, >>the problem would already be solved. >> >>:) > > But I think Dann's idea is very logical, since a lot of us simply disable null When did it become "Dann's idea"? This is an obvious idea that occurs to every person who considers double null move seriously. >move in some positions. Using double null move _only_ there must be better than >disabling it. Of course, that doesn't solve the problem of zugzwang in unepected >situations. > > José C.
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