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

Author: Vincent Diepeveen

Date: 07:33:19 07/13/02

Go up one level in this thread


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



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