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

Author: Uri Blass

Date: 18:54:49 04/27/04

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On April 27, 2004 at 21:00:22, Vincent Diepeveen wrote:

>On April 27, 2004 at 11:43:36, José 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:
>>  José C.
>Christophe wrote that down just to let you guys believe you should search
>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 :)


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.


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