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

Author: Gerd Isenberg

Date: 22:11:23 04/27/04

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On April 27, 2004 at 21:54:49, Uri Blass wrote:

>On April 27, 2004 at 21:00:22, Vincent Diepeveen wrote:
>
>>On April 27, 2004 at 11:43:36, JosÚ Carlos wrote:
>>
>>>On April 27, 2004 at 08:37:34, Tony Werten wrote:
>>>
>>>>On April 27, 2004 at 03:33:26, Bas Hamstra wrote:
>>>>
>>>>>About double nullmove: I tested this in some pawnendgames to see if it could
>>>>>handle zuzwang problems, but I don't see it perform any better than normal
>>>>>nullmove. Can Vincent or you post a position where double null outperforms
>>>>>normal null? I agree the idea is elegant, but I just don't see it work.
>>>>
>>>>I switch it off in pawns only endgames. Couldn't figure out why it wasn't doing
>>>>as well as it sounded.
>>>
>>>  I can't think about it now, but I recall this thread where an interesting
>>>discussion about double null move came up:
>>>
>>>http://chessprogramming.org/cccsearch/ccc.php?art_id=241476
>>>
>>>  JosÚ C.
>>
>>Christophe wrote that down just to let you guys believe you should search
>>fullwidth.
>>
>>Practical chances of it happening is small, not zero but very close to it.
>>Additionally you can add a single 'if then else' condition in transposition
>>table cutoff to avoid the theoretical scenario that christophe describes.
>>
>>Look the alternative to double nullmove is doing something dead slow like what
>>Gerd is doing, or what i used to do in my draughtsprogram; a verification
>>search, which is just a fullwidth search of n-R ply. So not the later posted in
>>ICGA verification search. Verification search already was excisting in other
>>publications than in the ICGA. So Omid just stole the name kind of for something
>>working crappy :)
>
>No
>
>Omid did not steal the idea.
>
>You simply did not understand Omid's ideas.
>Omid's idea is not mainly to detect zugzwangs but to detect tactics earlier.
>
>Null move pruning means that there are tactics that you need more plies to see
>because of the horizon effect when you cannot detect the threat.
>
>With verified null move pruning you can see it 1 or 2 plies earlier.
>
>Doing checks in the qsearch cannot solve the problem because there is tactics
>that is not based on checks.
>
>>
>>Basically all those approaches eat shitload of nodes to say it *very* polite.
>
>Basically I see no reason that verification search to detect zugzwangs needs to
>eat many nodes(Omid's idea is not verification search) and common sense tells me
>that if the depth is reduced enough it does not eat many nodes.
>
>Uri



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