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Subject: Re: NULL move question

Author: Robert Hyatt

Date: 11:22:59 01/18/00

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On January 18, 2000 at 10:08:09, Vincent Diepeveen wrote:

>On January 18, 2000 at 09:15:23, Robert Hyatt wrote:
>
>>On January 18, 2000 at 06:23:34, Vincent Diepeveen wrote:
>>
>>>On January 17, 2000 at 16:47:24, Dann Corbit wrote:
>>>
>>>>I have a theory that NULL move hurts at very, very long calculation times.
>>>>
>>>>The reason I suspect that it is true is that if one position in ten thousand is
>>>>a zugzwang type and you consider a billion positions, a lot of them will be NULL
>>>>moves.  Most of them will be the kind that really should be avoided (maybe 99%
>>>>or even 99.9%) but the 0.1-1% that really should be responded to get ignored.
>>>>When only a few million nodes are searched, I doubt if there is a problem except
>>>>in rare circumstances.
>>>>
>>>>Opinions?  Am I all wet?
>>>
>>>You're not correct. double nullmove detects zugzwang.
>>>In rook endings typical sometimes a single zugzwang is the problem.
>>>Therefore double nullmove is a great invention. Crafty fixes it by
>>>turning nullmove off when there is 1 piece left. That is a hard fix.
>>>double nullmove sees zugzwang also when there are n pieces left.
>>>
>>>Vincent.
>>
>>
>>Not me. I don't turn null move off until there are _no_ pieces left...
>
>Double nullmove nowadays in crafty?
>Or don't you find it useful to detect zugzwang with crafty in all those
>hundreds of thousands of games at the internet?


I just do other tricks.  :)  But no double-null move, and null-move is still
done until the side on move has no pieces at all.



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