Author: Bruce Moreland
Date: 09:46:36 08/09/01
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On August 09, 2001 at 10:33:51, Dieter Buerssner wrote: >On August 07, 2001 at 16:03:34, Bruce Moreland wrote: > >>I've often heard people state that null move with R=3 is better than with R=2, >>but I have never ever ever gotten a test result that indicates this. > >I also did quite some experiments here. Many similar to the ones you described. >Like R=3 at the tips and at the root. Changing between R=2 and 3 by remaining >search depth, and also dependent on the relative depth (say depth 10 wanted, and >change between the R at 5). The later yields in yet another inconsistency with >the hash tables... > >At test positions, I found no convincing difference between them all. There is >one exception. I think in rook endgames mostly the higer R was better. > >I did test games (I think mostly 5min+3sec) vs. Crafty. And when I tried this >first, almost anything, that had some sort of dynamical null move performed >better. Later, when I tried to reproduce, I could not see this anymore. Now, it >seems that R=2 allways is better. > >I think, the higer R hurts especially in positions, that look rather unforced to >the engine. Say White has a pawn at f6. Black castled K-side. Now perhaps white >can make 3 moves with the Q, until it reaches h6 for the mate threat. Say white >sacs some material while doing this. So lines with the Q-move null will fail >high for black. To a human, this can look rather simple. With high R, this can >need a lot of depth. One one such oversight may of course outweigh all advantage >gained by the general higher search depth. > >BTW. You mentioned, that Yace is using dynamical null move. It actually doesn't >by default. It has the framework, and it can be changed by the user, to swithc >to dynamical null move. But with the default setup, it will use R=2, and R=1 in >positions with only one minor piece per side. > >I am using a null move algorithim, that is functionally similar to the "double >null move" Vincent has explained here some times. I don't recall what that was, and I am interested enough that I'm embarass myself by asking: What was that? bruce > >Regards, >Dieter
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