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Subject: Re: not using nullmove?

Author: Anthony Cozzie

Date: 11:56:44 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
>observation", 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.
>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.

If I understand Ed's homepage, he uses the standard recursive null move pruning
everyone else does, except that he turns it off a low depths and switches to his
static forward pruning.


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