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Subject: Re: Null-Move: Difference between R = 2 and R = 3 in action

Author: Omid David

Date: 08:09:19 07/13/02

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On July 13, 2002 at 10:33:19, Vincent Diepeveen wrote:

>On July 13, 2002 at 04:47:16, Omid David wrote:
>
>>On July 13, 2002 at 02:39:38, Dann Corbit wrote:
>>
>>>On July 13, 2002 at 02:22:00, Omid David wrote:
>>>
>>>>On July 13, 2002 at 02:07:17, Vincent Diepeveen wrote:
>>>>
>>>>>I still do not understand which positions you talk about which R=2
>>>>>is finding and R=3 isn't.
>>>>
>>>>I read your other post, that's also my point: Although at fixed depth, R=2 is
>>>>much better than R=3 (see also "adaptive null-move pruning" Heinz 1999), in
>>>>practice R=3 performs about the same as R=2 since on many occasions it finds the
>>>>correct move one ply later with lower search cost.
>>>
>>>By the way, if you have not found Vincent's post on double null move you should
>>>look it up.  It is a clear win for sure.
>>
>>Yes it's a nice idea. But the main null-move pruning deficiency is its tactical
>>weakness due to horizon effect. Zugzwangs are not a major problem, and as
>>Vincent points out, he invented the double null-move idea just to show that
>>null-move pruning is OK. Now nobody doubts effectiveness of null-move pruning at
>>all, the only discussion nowadays is the depth reduction value.
>
>I'm missing any position where you have a problem though. Seems to me
>your thing is incredible weak, and or doing other dubious things which
>gets looked up in hashtable, after which it weakens your program.
>
>In DIEP i don't have all these problems.
>  - no dubious forward pruning
>  - no futility
>  - no razoring or any of these techniques.
>  - checks in qsearch
>
>Just PVS with nullmove R=3 and a bunch of extensions. That's it.
>
>Means that after a nullmove i don't get transpositions to positions
>where you have stored a score which is based upon a dubious score.
>
>Best regards,
>Vincent

Why do you think there is a problem?! All the results I got are natural. I'm
sure even in DIEP, R=2 works better under "fixed theoretical" conditions.
However in practice you don't search to fixed depth and thus R=3 might be better
in practice.

My only point is that "R=3 might be better than most people consider it." (Take
DIEP as a successful use of R=3)

P.S.
Have you published anything regarding double null-move?



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