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

Author: Vincent Diepeveen

Date: 19:19:26 11/21/02

Go up one level in this thread


On November 21, 2002 at 22:05:15, Vincent Diepeveen wrote:

Small addition: when the parameter 'allowingnull' is true
you must not allow transposition in hashtable either of course.

>On November 21, 2002 at 11:14:24, Robert Hyatt wrote:
>
>Just go for a 2 minute single cpu implementation.
>
>But of course you will find that R=2 always will outperform
>already his verification search with 1 ply reduction.
>
>You can implement it quicker his algorithm by doing next
>after nullmove:
>
>int Search(alfa,beta,depthleft,allowingnull) {
>  ..
>
>  if( !allowingnull && nullmoveok ) {
>    .. try nullmove
>    if( score >= beta ) { // score returned by nullmove
>      score = Search(alfa,beta,depthleft-1,true);
>       // last parameter to prevent another reduction next position
>      if( score >= beta ) {
>        StoreInHashtableAndKillerTable(..);
>        return score;
>      }
>    }
>  }
>  ..
>
>This is a more elegant way to implement it, and it was already done
>years ago and published in ICCA journal.
>
>That's pretty quickly done in crafty Bob :)
>
>>On November 21, 2002 at 10:15:47, Bernhard Bauer wrote:
>>
>>>Hi Omid,
>>>
>>>would you implement your pruning technique in crafty so the benefits could be
>>>tested by everybody?
>>>That way we would have the best comparison.
>>>regards
>>>Bernhard
>>
>>I am working on this.  I'll certainly post the results when I get it to work
>>right.
>>It is a bit tricky if you try to do it cleanly...
>>
>>
>>>
>>>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



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