Computer Chess Club Archives




Subject: Re: When to do a null move search - an experiment

Author: Sune Fischer

Date: 05:24:54 04/29/04

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On April 29, 2004 at 08:10:03, Vincent Diepeveen wrote:

>On April 28, 2004 at 18:31:48, Sune Fischer wrote:
>>>double nullmove:
>>>allowed: a3 null null d5 ...
>>>allowed: a3 null null d5 null null d4 ....
>>>allowed: a3 null d4 null null d5 ...
>>I gues the last one should have been
>>allowed: a3 null d4 null d5 ...
>That will not find zugzwangs.
>if there is a zugzwang after a3 null d4, then doing a double null after that
>will find it. i am interested in seeing zugzwangs with nullmove. with just 1
>rule into my nullmove i can find them without big problems.

Hmm, I don't see how you will catch zugzwangs after 3 nullmoves.

Each time you nullmove in a zugzwang you change the winning side, doing it 3
times or 5 times is the same as doing it once, AFAICT.

>>I think the rule is there must be an equal number of nullmoves.
>>In special cases the last one might theoreticly fail, ie. if the opponent can't
>>undo the zugzwang.
>>Say he is forced to capture or move a pawn for instance.
>>>That this eats more ply to solve some testset trick like a Bxe4 somewhere, bad
>>>luck there.
>>Why, because nullmoving misses a deep threat?
>Because fullwidth in that Bxe4 position is better because a king must walk from
>one side of the board to f2 or something. So the reduction factor is the problem
>possibly. Nothing to do with zugzwang.

Yeah, that's a typical deep threat.
I think most pruning schemes have problems dealing with that, one might try and
counter balance it by introducing the "right kind" of extensions. :)

>But the majority of nerds kick on solving testset problems, sehe Isenberg.



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