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

Author: Omid David Tabibi

Date: 12:04:13 11/20/02

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On November 20, 2002 at 14:59:10, Andreas Herrmann wrote:

>On November 20, 2002 at 11:43:10, Omid David Tabibi wrote:
>
>>
>>            ICGA Journal, Vol. 25, No. 3, pp. 153-161, September 2003
>>
>>
>>                          Verified Null-Move Pruning
>>
>>                    Omid David Tabibi and Nathan S. Netanyahu
>>
>>
>>                                   Abstract
>>
>>In this article we review standard null-move pruning and introduce our extended
>>version of it, which we call verified null-move pruning. In verified null-move
>>pruning, whenever the shallow null-move search indicates a fail-high, instead of
>>cutting off the search from the current node, the search is continued with
>>reduced depth.
>>
>>Our experiments with verified null-move pruning show that on average, it
>>constructs a smaller search tree with greater tactical strength in comparison to
>>standard null-move pruning. Moreover, unlike standard null-move pruning, which
>>fails badly in zugzwang positions, verified null-move pruning manages to detect
>>most zugzwangs and in such cases conducts a re-search to obtain the correct
>>result. In addition, verified null-move pruning is very easy to implement, and
>>any standard null-move pruning program can use verified null-move pruning by
>>modifying only a few lines of code.
>>
>>
>>pdf:  http://www.cs.biu.ac.il/~davoudo/pubs/vrfd_null.pdf
>>zipped pdf:  http://www.cs.biu.ac.il/~davoudo/pubs/vrfd_null.pdf.zip
>>gzipped postscript:  http://www.cs.biu.ac.il/~davoudo/pubs/vrfd_null.ps.gz
>
>Hi Omid,
>
>hmm seems interresting. Thanks for the paper. I will try it out in the next
>days. Did you tryd your null move extension also in pawn endgame positions where
>the most moves in the search tree are zugzwang?
>

No I didn't conduct much experiments on various zugzwang positions. The main
benefit of verified null-move pruning is in the middle game, since it will
construct a smaller search tree with more accurate results.

I believe that in endgames with extreme cases of zugzwang, it might be better to
turn off null-move altogether; since while verified null-move will guarantee an
accurate result, the cost of the re-searches might be too much.

Omid.

>Andreas



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