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Subject: Re: A Null Move Enhancement?

Author: Peter Fendrich

Date: 05:23:10 02/11/99

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On February 11, 1999 at 02:32:14, Bruce Moreland wrote:

>
>On February 10, 1999 at 21:55:32, Will Singleton wrote:
>
>>On February 10, 1999 at 19:32:18, Bruce Moreland wrote:
>>
>>>
>>>On February 10, 1999 at 19:00:03, Dann Corbit wrote:
>>>
>>>>On February 10, 1999 at 17:20:34, Dan Homan wrote:
>>>>[snip]
>>>>>This is a very interesting observation.  Maybe it would be right to
>>>>>say that null move might be a "waste" of time if the material score
>>>>>is not close to beta?  Taken a step further... some kind of a "windowed"
>>>>>null-move might be a good idea.
>>>>>
>>>>>I tried this in my program.  I changed my null move code so that
>>>>>a null move would only be tried *only* if the material score for the side
>>>>>to move was greater than (beta-1.5*pawn_value).  This reduced my
>>>>>searched nodes from 5-10% in most of the positions I have tried so
>>>>>far.  (I have only tried a handful of WAC positions so far.)
>>>>>
>>>>>If this pans out, It is a perfectly safe enhancement to
>>>>>null-move.  The 1.5 pawn window that I tried was arbitrary;
>>>>>another value might do better.
>>>>What an incredibly creative idea!
>>>
>>>Not a new idea ;-)
>>>
>>>bruce
>>>
>>
>>Implying that you either use something like this or have found it to be not
>>worthwhile.  If you use it, what window value do you use, and does it change
>>depending on the situation?
>
>I think the idea is a good idea.  I couldn't make it work in mine, meaning that
>it didn't make anything go faster.  I know I've tried it.  I don't think I
>invented it.
>
>The idea is obviously that if you are obviously hosed based upon some quick
>eval, that you probably aren't going to come back with a fail high if you give
>the opponent a free move.
>
>Another idea for you guys, which I didn't invent, tried, and don't use, is
>widening the null move window in the downward direction in some circumstances.
>
>You not only check for fail high, and cut off if you get it, you check for fail
>low.  A fail low indicates that the opponent has a massive threat.  In this case
>you can extend.
>
>This idea was mentioned in the original Donninger paper on null-move, ICCAJ,
>don't know what issue, but it was between 1990 and 1995.
>
>bruce

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...

//Peter



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