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Subject: Re: Null move generalization

Author: Ricardo Gibert

Date: 20:59:39 04/17/02

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On April 17, 2002 at 15:43:23, Jesus de la Villa wrote:

>
>Have someone defined the general rule(s) where null move
>is unable to find simple combinations?, and if so, which
>are those rules ?
>
>"Obviusly" is more expensive to check it than to not
>use Null Move.
>
>Thanks for asking
>
>
>
>PS. I hope you undertand my poor English :)

Nullmove assumes that having the move is better than not. This assumption is not
correct for zugzwangs, so nullmove will have a problem with those positions
where zugzwang is relavant. It fails quite badly, so some care is needed in
avoiding this. Not using it in the endgame where zugzwang occurs with
significant frequency is one way. Another idea is "double nullmove".

Pseudo-zugzwang, where having the move results in a delay in attaining a
favorable result, is fine for nullmove. In fact, it makes out like a bandit by
allowing a program to find a favorable result more easily than it would
otherwise. Unfortunately, these also only occur with significant frequency in
the ending where nullmove is typically turned off :-(



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