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Subject: Re: Verified Null-Move Pruning, ICGA 25(3)

Author: Frank Phillips

Date: 13:54:10 11/27/02

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On November 27, 2002 at 15:54:26, Omid David Tabibi wrote:

>On November 27, 2002 at 15:36:31, Frank Phillips wrote:
>
>>On November 27, 2002 at 15:15:50, Robert Hyatt wrote:
>>
>>>On November 27, 2002 at 13:48:50, Frank Phillips wrote:
>>>
>>>>On November 26, 2002 at 20:02:06, Robert Hyatt wrote:
>>>>
>>>>>On November 26, 2002 at 16:21:00, Omid David Tabibi wrote:
>>>>>
>>>>>>On November 26, 2002 at 15:58:06, Gian-Carlo Pascutto wrote:
>>>>>>
>>>>>>>On November 26, 2002 at 15:55:56, Omid David Tabibi wrote:
>>>>>>>
>>>>>>>>So it is reasonable that on every program starting from a certain depth >adaptive null-move pruning will always construct a smaller search tree.
>>>>>>>
>>>>>>>Don't you mean the other way around?
>>>>>>>
>>>>>>
>>>>>>Yes :-)
>>>>>>
>>>>>>Starting from a certain depth, verified null-move pruning will always construct
>>>>>>a smaller search tree than the adaptive one.
>>>>>>
>>>>>>
>>>>>>
>>>>>>>--
>>>>>>>GCP
>>>>>
>>>>>
>>>>> I am doing some testing now.  First thing I noticed is that for WAC, the
>>>>>time-squared
>>>>>measurement went down very significantly for your algorithm.  And I have not
>>>>>modified
>>>>>anything such as turning null-move off when low material happens, since your
>>>>>idea will
>>>>>catch the zug problems.
>>>>
>>>>Have you tried Fine70?
>>>>
>>>>Frank
>>>
>>>Yes...  and I told Omid that this is a strange case as if I allow null-move in
>>>pawn-only
>>>endings, which turns it on for fine 70 of course, things get wrecked inside the
>>>search
>>>somehow.  A 45 ply search fails to see that Kb1 wins where normally an 18-19 ply
>>>search is enough...
>>>
>>>
>>>>>
>>>>>
>>
>>
>>Snap... and I have no idea why.  I thought it was my implementation of a similar
>> idea (from Bruce's site) of verification search, but I copied the scheme in
>>Omids paper and it does the same.
>>
>
>What appears at Bruce's site is the original Goetsch and Campbell idea to detect
>zugzwangs. Plenkner (1995) introduced a similar zugzwang detection method.
>
>Verified null-move pruning is different from these methods, for its most
>important application is in middle games, constructing a smaller search tree
>with greater tactical accuracy.
>
>
>>Frank


Got it.  It is not recursive (of course) so the non-verified null moves can fall
prey to zugswang.

Frank



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