Author: Ernst A. Heinz
Date: 16:31:04 10/04/98
Go up one level in this thread
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 <http://wwwipd.ira.uka.de/Tichy/DarkThought/>.
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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.
[...]
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=Ernst=
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