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

Author: Martin Giepmans

Date: 14:39:26 11/20/02

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On November 20, 2002 at 16:19:29, Omid David Tabibi wrote:

>On November 20, 2002 at 16:04:50, Martin Giepmans 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.
>>>zipped pdf:
>>>gzipped postscript:
>>If I'm not mistaken this is the well known "verification search" with
>>one modification: no verification in the verification search.
>>Am I right?
>The classical verification search as introduced by Plenkner comes to detect
>zugzwangs. Verifeid null-move pruning as presented in the paper, constructs a
>smaller search tree with greater tactical strength in middle games (in addition
>to detecting zugzwangs).
>>Another question:
>>your results in table 5 seem convincing, but what about table 4?
>>Are these results statistically significant? (my guess is no ..)
>For a good estimate of the growth of the search tree as we go deeper, see Table
>3 and Figure 4 (which present ECM test positions searched to a depth of 11
>The WCS test positions were mainly used for testing the tactical strength
>(results in Table 5). Table 4 was provided just for the sake of completeness.

I see that I reduced the numbers of the tables (R=1 ;))
What I wanted to write is that table 6 is convincing while table 5 is IMO not.

Combining table 4 and 5 my impression is that - from a time perspective -
R=3 might be better than verified R=2.
Compared to R=3 verified R=2 solves about 3% more positions but is about 40%


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