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Subject: Re: So how do we tell when to avoid null-move?

Author: José de Jesús García Ruvalcaba

Date: 16:07:35 11/05/99

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On November 05, 1999 at 12:39:20, David Eppstein wrote:

>This and the many other null-move-killer positions regularly posted here seem to
>show that crafty's simplistic check (avoid null move when side to move has only
>one non-queen piece) could stand some improvement.  What better algorithms are
>other programs using to tell when a position might be zugzwang?  I vaguely
>remember a commercial programmer (Christophe or Ed?) making a cryptic comment
>about double-null-move solving this problem, but I didn't understand what that
>might mean.

	It means allowing two consecutive null moves in the search (but no more). This
will mean searching the position with the correct side to move with a depth of
n-2R, where n is the depth of the original search and R is the null reduction.
	It will eventually catch all zugzwangs (unlike traditional null-move search
that does not allow two consecutive null moves).

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