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Subject: Re: not using nullmove?

Author: Christophe Theron

Date: 11:24:08 02/15/04

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On February 14, 2004 at 17:52:45, scott farrell wrote:

>On February 14, 2004 at 05:28:04, Uri Blass wrote:
>
>>On February 14, 2004 at 02:09:38, Dann Corbit wrote:
>>
>>>On February 13, 2004 at 12:51:08, Uri Blass wrote:
>>>
>>>>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.
>>>>>
>>>>>Tord
>>>>
>>>>Rebel and chess tiger use null move pruning.
>>>>They use other reductions but the same also for you.
>>>
>>>At one time, Rebel did not use null move pruning (IIRC).
>>
>>At one time when I began with movei movei also did not use null move pruning.
>>The point is that Ed found that adding null move pruning was productive.
>>
>>Uri
>I read a post recently that Ed uses, but not like we do.
>
>He uses it to confirm a reduction or pruning.
>
>He uses it around alpha and not beta, and doesnt use it to cut off.
>
>Scott



What Ed calls alpha is what we beta.



    Christophe



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