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Subject: Re: When to do a null move search - an experiment

Author: Ed Schröder

Date: 23:00:57 04/29/04

Go up one level in this thread

On April 29, 2004 at 23:25:59, Robert Hyatt wrote:

>On April 29, 2004 at 16:17:34, Ed Schröder wrote:
>>On April 29, 2004 at 14:44:47, Robert Hyatt wrote:
>>>On April 29, 2004 at 09:28:53, Ed Schröder wrote:
>>>>On April 29, 2004 at 07:37:23, Vincent Diepeveen wrote:
>>>>[ snips ]
>>>>>>This is all very poor Vince, I assume you don't play much with nowadays top
>>>>>>programs. From 1982 to 2001 Rebel won its games by positional understanding and
>>>>>>not by search and Rebel lost its games because it was outsearched. Today Rebel
>>>>>>isn't outsearched at all, it now loses its games because the current top
>>>>>>programs have a better positional understanding than Rebel.
>>>>>>You should have a good look at the current tops, the positional progress has
>>>>>>been great the last years. To me it all seems to indicate (provided your search
>>>>>>is okay) the only way to make progress is to improve on chess knowledge. But
>>>>>>what's new, I already came to that conclusion in 1986 after some intensive talks
>>>>>>with Hans Berliner.
>>>>>What i mean is Ed, is that you would not have accomplished the great results
>>>>>with Rebel which you managed, had you just searched with a fullwidth search +
>>>>>bunch of checks in qsearch.
>>>>No of course not, brute force is silly, Rebel since day 1 has been a selective
>>>>program. But I am getting your point, in the days before the nullmove was
>>>>discovered Genius and Rebel had the best (static) selective search, a dominant
>>>>factor in their successes, is that what you meant to say? If so, it is true.
>>>>If only Frans had kept his mouth shut to Chrilly (Chrilly leaking nullmove in
>>>>the ICCA journal) it is very likely Fritz would been the next Richard Lang still
>>>>dominating all the rating lists and WCC's for the last decade. But Frans didn't
>>>>and then all bets were off.
>>>Chrilly wasn't the one that started the null-move search stuff.  Don Beal was
>>>the first I recall reading although Murray Campbell also wrote a paper on the
>>>idea.  I will try to flip through the surviving Cray Blitz source listing to see
>>>exactly when null-move was added to it.  All I remember is Burton Wendroff
>>>(Lachex) sending me a copy of Murray's paper and saying "try this". (this
>>>happened while I was preparing for an ACM or WCCC event).  Of course I am
>>>talking about R=1, non-recursive, as it was defined "in the good old days".. :)
>>Actually Don Beal told Frans about nullmove in Cologne 1986, Don at that time
>>only used nullmove in QS. Don did not use nullmove as we know it today, that
>>came after Chrilly's article.

>Yes, but Campbell defined "the null-move observation" exactly as it is used
>today (no move played, reduce depth, if it fails high, then let the search fail
>high with no more searching.)  He even suggested that R=2 needs serious testing.

Did Campbell mention recursive nullmove too? Because that's where the real
strength of the algorithm comes from.

>Chrilly's main advancement was using the null-move observation to detect threats
>and extend the search when the condition was met.  I don't know of anyone that
>really does this today.  I did it back around version 9, but stopped due to the
>high cost and low return...

As far as I can remember the article was about detecting mate-threats only, I
could be wrong. I use it, when the first nullmove returns a mate-value I extend
one ply.

My best,


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