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Subject: Re: new thoughts on verified null move

Author: Martin Giepmans

Date: 08:37:25 11/23/02

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On November 23, 2002 at 08:48:36, Omid David Tabibi wrote:

>On November 23, 2002 at 08:45:00, Uri Blass wrote:
>>On November 23, 2002 at 08:11:37, scott farrell wrote:
>>>Just after other people's thoughts.
>>>I think Omid's work overlooked the adapative null move searching many of us do,
>>>ie. transitioning from r=3 to r=2.
>>>I think adaptive null move tries to GUESS where to use r=2 to reduce the errors
>>>that R=3 makes. I guess it depends on how often this GUESS is correct, the cost
>>>of the verification search, and how long it takes the adaptive searching to
>>>catch the error at the next ply.
>>>Has anyone looked at setting the verification search to reduced depth of 2
>>>(rather than 1)? obviously to reduce the cost of the verification search.
>>Omid checked it but you also reduce the gain.
>>I think that I will look for good rules when to do the verification search so
>>the cost will be significantly smaller but the gain is going to be the same in
>>at least 99% of the cases.
>I'm currently working on other variations. The initial results are promising.

I have done some tests with your method at greater depths.
At depth 12 vrfd R=3 still had an overhead (in terms of treesize) of about
25% compared to pure R=3.
(my engine uses a simple Q-search that shouldn't give problems here)

So the question is if your expectation that the treesize of R=3 and vrfd R=3
converge at greater depths (> 11) really holds.

Needs more testing, I think.

Another point:
I would expect that vrfd R=3 becomes less safe at greater depths.
The subtrees in which you don't verify nullmove (after the verification) become
deeper and I see no reason - on logical grounds - why this shouldn't give safety
Even if R=3 and vrfd R=3 converge in terms of treesize, the safety (or rather
the lack of it) might also converge ...

In any case, thanks for sharing.


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