Author: Vincent Diepeveen
Date: 04:29:16 11/15/99
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On November 14, 1999 at 22:58:19, James Robertson wrote: >On November 14, 1999 at 22:16:33, Will Singleton wrote: > >>On November 14, 1999 at 21:45:26, William Bryant wrote: >> >>>I recently found that my null threashold is set to low, and I am experimenting >>>with different level. >>> >>>I am curious what other people have found works for them. >>> >>>Do you count pieces or pieces and pawns? >>> >>>How may pieces or pieces and pawns must be present for the side on move >>>to allow a null move? >>> >>>Thanks in advance. >>> >>>William >>>wbryant@ix.netcom.com >> >>I originally had a threshold of around 3 pieces per side, but now I allow >>endgames as long as someone has a piece. This is further modified by a >>blocked-pawn term, which disallows null if most pawns are blocked. I think. >>So, I don't detect zug like some others attempt to do. >> >>I only use R=2, but I know others alternate between 2 and 3 depending on the >>situation. >> >>Will > >What are the advantages/disadvantages of alternating between R=2/3? Does having >some entries with R=3 cause problems with the hash table? The difference between R=2 and R=3 is marginally, however for DIEP R=2 needs a lot more nodes than R=3. Something interesting though is what happens the last few ply. At R=2 you are tempted prune the last 3 ply with quiescencesearch. At R=3 you are doing the last 4 ply, which means that you prune 2 moves of your opponent. For some programs that don't detect much in qsearch this might be a problem. Everyone has to figure out whether R=2 is better for him or whether he can do R=3 too. Some alternatives is using a combination: first nullmove R=3 and all nullmoves after the first one R=2. I am no longer doing that though. I use everywhere R=3 now. Bad luck for a few positions in LCT test and bs2830 testset! Obviously a nullmoving program with R=3 needs 3 ply more than with R=2 to find Kh2-g3!! I guess everyone has to figure out his own reduction based upon node reduction. If R=3 gives you a time reduction of 50%, then i bet it's a good idea to use R=3 instead of R=2 ! >James Vincent
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