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Subject: Re: Multi-ProbCut and Crafty : does it work ?

Author: Will Singleton

Date: 09:03:01 06/28/03

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On June 28, 2003 at 11:20:21, Frederic Louguet wrote:

>I read an interesting paper from Albert Xin Jiang and Michael Buro about
>Multi-ProbCut and its implementation in Crafty. I have always been very
>skeptical about this pruning technique (for chess) but the paper is rather
>optimistic. However, the data presented does not seem very convincing from a
>statistical point of view (too few games, not enough opponents). So could Robert
>Hyatt tell us a little more about the effectiveness of this technique ? Does it
>_really_ work ?

I don't know about crafty, but I can tell you my experience.  After messing with
the values of cutoffs(c), moves(m) and reduction(r), I use c=2, m=8, and r=3/4,
depending on depth.  Increasing m (number of moves to probe to try to get
cutoffs) slows you down and doesn't help accuracy very much, and any value
greater than 2 for c caused all kinds of unnecessary searching.

I found it helps slightly in many cases, and has no effect or is slightly worse
in others.  I didn't quantify it, but I didn't get quite the results the authors
did.  But since it didn't seem to hurt, I left it in.

Will



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