Author: Roberto Waldteufel
Date: 18:26:36 10/04/98
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On October 04, 1998 at 19:31:04, Ernst A. Heinz wrote: >On October 04, 1998 at 19:06:15, Roberto Waldteufel wrote: >> >>Hi all, >> >>I wonder what reductions various programs use for the null move. I reduce by 2 >>plies, but I believe a one-ply reduction may be more usual. However, I have >>found R=2 produces quite good results in my program. I would like to hear of >>others' experiences. > >Below I quote again from my article about "How DarkThought Plays Chess" as >published in the ICCA Journal 20(3) and electronically available from the WWW >page of "DarkThought" at URL . > >******************************************************************************* > >Search Parameterization > >[...] > >Null-Move Search. > Generally regarded as both a curse and a blessing of > microcomputer-based chess programs, the realm of null-move > pruning provides ample opportunities for many improvements (e.g. by > parameter fine-tuning). In DARKTHOUGHT, null moves may be > layered (i.e. disabled in either the upper or lower parts of the search > tree up to a predefined depth threshold), made non-recursive or even > switched off completely. The first DARKTHOUGHT delayed null moves > until depths <= 5 after Don Dailey (of SOCRATES and STARSOCRATES > fame) enthused about this scheme during the 8th WCCC in Hong > Kong, 1995. > > Like many other chess programs, DARKTHOUGHT currently uses a > depth-reduction factor of 2 for null-move searches. But other values, > especially depth-adaptive ones in combination with various material > thresholds for disabling the null move in endgames, are constantly > experimented with. The same holds for depth and score margin of the > deep-search extension which default to 2 and the value of 3 Pawns > respectively. > >[...] > >******************************************************************************* > >=Ernst= Thanks for the reply and the extract from your paper. I have read your paper on extended futility pruning and limited razoring at your web sit today - very interesting stuff. I currantly do normal futility pruning, but I have not tried any sort of pruning at depths of 2 or 3. You have given me some good ideas to try out :-) Best wishes, Roberto
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