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

Author: Omid David

Date: 01:47:16 07/13/02

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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.



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