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Subject: Re: Deep Search Extension

Author: Robert Hyatt

Date: 07:37:59 01/18/98

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On January 18, 1998 at 01:33:02, Stuart Cracraft wrote:

>What is Deep Search Extension (with null move)?
>I'm referring to this paper which I hope to buy some back
>issues to have in my collection. But until then, if you know
>about this extension, if that is indeed what it is, please
>jot a reply.
>The article is:
>Donninger, C. (1993). Null move and deep search: Selective search
> heuristics for obtuse chess programs. ICCA Journal, Vol. 16, No. 3,
> pp. 137-143.

It is a form of the extension Bruce described for null-move mate threat
extension.  The idea was to shift the null-move window downward, and
notice whether the null-move search fails high or low.  If it fails low,
there is some sort of threat in the current position.  If it fails high,
there is no threat.  If there is a threat, you extend by 1 ply.

I tried it and found it was not effective at all.  It would solve some
problem positions faster, to be sure, but it did not perform as well in
regular games.  I discarded it two years ago.  I believe Bruce Moreland
also tried it and chucked it...

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