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Subject: Re: To skin a cat (was Re: NULL MOVE)

Author: Thorsten Greiner

Date: 07:57:08 02/26/99

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On February 25, 1999 at 00:12:53, Don Dailey wrote:

>On February 24, 1999 at 19:16:27, Bruce Moreland wrote:
>>On February 24, 1999 at 15:37:58, Don Dailey wrote:
>>>My program is a mixture of static rules and null move.  I do null
>>>move when I have significant depth remaining, but when I am near
>>>end nodes I do a simple static attack analysis.  This has proven
>>>to be a significant improvement to my chess program.  It is faster
>>>than null move and slightly riskier, but the net affect is
>>>a stronger chess program (for me.)   Even though it's probably
>>>riskier, it does pick up things null move will miss although the
>>>converse is also true.
>>Can you describe this or give examples please?  I know that some people do this
>>but I haven't the vaguest idea how it works.
> [Nice story of Don Dailey deleted]
>I  think there are  probably  several  modern programs  that use  some
>version of this  static based selectivity,  and Rebel is  one of them.
>Rebel may not do it  anything like we did, but  it shows that there is
>more than one way to skin a cat!
>- Don

It seems some other chess programmers also discovered the ideas you described.
For example, Ernst Heinz of the german Dark Thought team describes a similar
idea in his paper on extended futility pruning, where they apply static
selectivity in the last three plies before the search horizon (see for this and other papers).

Also Rainer Feldmanns (from Zugzwang) idea of FH-reductions aims at a similar
direction: At each node in the tree, they reduce the depth of the subtree by
one, if the static evaluation (backep up by some threat recognition) if >= beta.
A link to the online version of his paper is found at


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