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Subject: Re: Null Move Heuristic - Comments Please (somewhat long)

Author: James Swafford

Date: 09:23:57 05/15/99

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On May 15, 1999 at 01:03:21, Dave Gomboc wrote:

>On May 15, 1999 at 00:47:12, James Swafford wrote:
>
>>On May 15, 1999 at 00:34:35, Dave Gomboc wrote:
>>
>>>On May 14, 1999 at 20:10:09, William Bryant wrote:
>>>
>>>>I'm ready to ruin a perfectly good search by adding more code. If done right,
>>>>the Null move should make it much stronger.  My copy of C. Donningers paper has
>>>>been ordered by inter library loan so I have not yet read the paper.  Below is a
>>>>summary or digest of information available from this forum over the last year
>>>>concerning null moves.
>>>>
>>>>I think this is a pretty up to date summary of the heuristic, but would
>>>>appreaciate any comments.
>>>>
>>>>Note: I have assembled this from many posts, maybe even yours.  I claim no
>>>>copyright on the material.  For those, like me, ready to expand their programs
>>>>with Null move search, I hope this summary helps.  Please feel free to correct
>>>>any errors I might have made.
>>>>
>>>>William
>>>>wbryant@ix.netcom.com
>>>>
>>>>Null Move Summary
>>>>
>>>>Description
>>>>	Null moves are a forward pruning mechanism to generate a beta cutoff without
>>>>doing a full search
>>>>
>>>>Situations to Avoid Null Moves
>>>>1. When the side on move is in check. Then a null move simply allows the other
>>>>side to capture the King.
>>>>2. Having just done a null move.
>>>
>>>I have heard this restriction before, but I have also heard that it is fine to
>>>do this, because one or the other null-move will fail.  Does this make any
>>>sense?  I have not spent much time thinking about it.
>>>
>>>Dave
>>
>>
>>Suppose you're in Search( ) with depth remaining=7.
>>Now you start a null search w/ a reduction of 2, so
>>you're in search again with depth=5.
>>
>>Now repeat.  Repeat again.
>>Soon enough you're in quiescence, and you might as well
>>have set r to 7.
>>
>>--
>>James
>
>Are recursive null-moves normally done without limit?  I was under the
>impression that a maximum number per continuation were allowed. ?!
>
>Dave

I've never heard of recursive null moves. :-)
Perhaps you could try it and share your results? :-))

--
James



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