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Subject: Re: new thoughts on verified null move

Author: Martin Giepmans

Date: 10:29:38 11/23/02

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On November 23, 2002 at 12:52:21, Omid David Tabibi wrote:

>On November 23, 2002 at 11:37:25, Martin Giepmans wrote:
>
>>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.
>>>
>>>>Uri
>>
>>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.
>
>Of course verified R=3 will *always* construct a larger tree than standard R=3.
>However, starting from a certain depth, it will always construct a smaller tree
>than standard R=2.
>
>Take note, that while verified R=3 constructs a slightly larger tree than
>standard R=3, it has a superior tactical strength to even R=2 !
>
>
>>
>>(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
>>problems.
>>Even if R=3 and vrfd R=3 converge in terms of treesize, the safety (or rather
>>the lack of it) might also converge ...
>>
>
>None will converge.

That is what you hope. And hope is a good thing, for sure :)
But how do you know? In your article there are no results for depths>11.

>However, the deeper you go, the smaller will be the difference in tree size,  and the greater the difference in tactical strength.
>
Again, how do you know?

Martin
>
>>In any case, thanks for sharing.
>>
>>Martin



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