Author: José Carlos
Date: 23:36:28 04/25/02
Go up one level in this thread
On April 25, 2002 at 19:50:21, Ricardo Gibert wrote: >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. I didn't mean to offend anyone. Dann said it; I had never though about double null move before; Bob answered; then I called it Dann's idea just to name someway, nothing more. But from now on, I'll call it "every person who considers double null move seriously"'s idea :) José C. >>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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