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Subject: Re: not using nullmove?

Author: Christophe Theron

Date: 21:38:58 02/13/04

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On February 13, 2004 at 12:41:41, Tord Romstad wrote:

>On February 13, 2004 at 12:28:26, Mike S. wrote:
>>On February 13, 2004 at 11:07:02, Tord Romstad wrote:
>>>(...) That several of the top commercial
>>>programs do not use null move (at least not in the conventional way) is
>>>further evidence that it is possible to come up with something better.
>>Are you sure that there are top engines which don't use nullmove? Maybe they
>>"just" combine it with some zugzwang detection, or switch it off depending on
>>the amount of material earlier than other engines...
>>(I think the last engine not using nullmove which was among the top was Chess
>>Genius, but that was many years ago.)
>>I'm aware that some engines are not affected by the zugzwang/nullmove problem as
>>much as others are. - I'm only asking from the viewpoint of a user and fan, IOW.
>>no programmer: Is it ok to say, nowadays all top-10 (if not more) engines have
>>to have nullmove implemented in some way, because without they wouldn't be
>>competitive in terms of search speed?
>I guess all strong programs use what Cristophe once called "the null move

Mmh... This post was a long time ago. So you were reading at that time? :)

> which consists of the simple fact that in almost all chess
>positions, there is at least one move which is better than doing nothing.
>Hence, in a wide sense of the term, all programs do indeed use nullmove.

It is a very wide sense. It is possible to take advantage of this observation
without performing the famous "null move". It is also possible to take advantage
of it to do something else than "pruning".

"null move pruning" means something very precise. But it is possible to take
advantage of the "null move observation" in many different ways.


>However, everybody does not use standard recursive null move pruning in
>the form popluarized by Chrilly Donninger in the ICCA Journal a few years
>ago.  Chess Genius and Junior have already been mentioned.  Two other
>examples are Rebel and Chess Tiger.

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