Computer Chess Club Archives




Subject: Re: Deep Search Extension

Author: Ernst A. Heinz

Date: 01:21:26 01/19/98

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On January 18, 1998 at 18:53:15, Bruce Moreland wrote:

>On January 18, 1998 at 10:37:59, Robert Hyatt wrote:
>>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...
>No, my idea is a form of Donninger's thing rather than the other way

If you want to take this "who discovered what" game a step further, we
should attribute all these special cases to Anantharam's more general
"threat extension" as described in his Ph.D. thesis. The "Deep Thought"
team used fail-low null move scores to detect threats before 1990 ...

>The only place I've read about this recently is on the Dark Thought
>page.  Are you guys still doing this, or am I confused?

Yes, I have modified and fine-tuned the original deep-search rules quite
a bit in order to make the extension usable. I still like it together
with aggressive null move pruning, especially in the endgame.


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