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Subject: Re: Null Moves at the Root?

Author: Robert Hyatt

Date: 14:59:38 12/23/00

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On December 23, 2000 at 14:31:57, Gian-Carlo Pascutto wrote:

>On December 23, 2000 at 12:53:03, Robert Hyatt wrote:
>
>>
>>I don't know if that would work.  Such a null-move search _must_ fail high,
>>or else you are winning.  Because you just let the opponent play two moves in
>>a row, and if he can't win with that advantage, something is up.  I don't think
>>you can use the score returned by null-move to set the initial aspiration
>>window for that reason.
>
>I wasn't thinking of that, but of the case where two moves for the
>opponent would not allow him to get his score high enough to stay
>inside the window you originally set. In that case your window must
>be way too high/low (depening on who's side you look at ;) or you
>have a zugzwang situtation.
>
>But now that you mention it, why not use the nullmove score as a lower
>bound (alpha) for the search? The idea being that we must be able to
>improve upon what would happen if we would pass. This might come in
>handy in cases where you fail low, and instead of going to -INF, just
>set alpha to the nullmove score.
>
>--
>GCP


You could do this, but I think the normal "previous value - .5" (or whatever
a programmer chooses to use) would be _far_ more accurate.  The null-move score
would probably lose material big time...  ie you play QxQ and if I play a null
move, you move the queen and I am a queen down...



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