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Subject: Re: A Null Move Enhancement?

Author: Bruce Moreland

Date: 20:36:09 02/11/99

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On February 11, 1999 at 16:21:06, Will Singleton wrote:

>
>On February 11, 1999 at 12:52:27, Bruce Moreland wrote:
>
>>
>>On February 11, 1999 at 08:23:10, Peter Fendrich wrote:
>>
>>>Can't check that from here, but it "must be":
>>>"Null Move and Deep Search: Selective-Search Heuristics for Obtuse Chess
>>>Programs." Donninger, C. (1993).
>>>ICCA Journal, Vol. 16, No. 3, pp. 137-143. (A)
>>>
>>>I tried it but it was no hit.
>>>That doesn't mean that it couldn't work for other programmers in other
>>>programs...
>>
>>I expect that Ernst will respond, because he refined it and I think still uses
>>it.
>>
>>bruce
>
>
>I tried it (only allowing null-move when material imbalance exists) and found
>very little change.
>
>Regarding your thought about threat-detection and null-move, a reading of
>Anantharaman's article (ICCAJ 1991) indicates that he found little or no benefit
>to this.  But I remember something about you detecting mate threats with null
>move.  Is that right?

That seems to help on some tactical tests.  Sometimes I return mate scores that
are outside the window, and when I find one of these I extend all of the
candidates.

So, in this case, if you let your opponent move when it is your move, and as a
result you are instantly mated, extend everything a little, since you might end
up pushing the mate over the threshold.

The null-move killer position is WAC 141.  It's an obvious mate that humans can
see easily, and some programs can see really quickly, but a generic null-move
program can't see it very well.

4r1k1/p1qr1p2/2pb1Bp1/1p5p/3P1n1R/1B3P2/PP3PK1/2Q4R w - - 0 1

The key is Qxf4, and it's a forced mate.

bruce



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