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Subject: Re: razoring?

Author: Bas Hamstra

Date: 07:22:14 08/16/99

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What good is razoring? How safe is it? Pros en cons?


In August 16, 1999 at 03:44:38, Dave Gomboc wrote
>On August 16, 1999 at 00:17:39, Scott Gasch wrote:
>
>>
>>Would someone please explain the concept of razoring or point me to a reference?
>>
>>Thanks,
>>Scott
>
>You could consult section 4.1 of Computer Chess Compendium, Levy (ed.),
>Springer-Verlag, 1988.  This book has some cool stuff in it, and is IMO well
>worth tracking down at your local university's library.
>
>It is actually a reprint of "Tree-Searching and Tree-Pruning Techniques", John
>Birmingham and Peter Kent, in Advances in Computer Chess 1 (Clarke, ed.),
>Edinburgh University Press, 1977, pp. 89-97.
>
>The quick low-down:
>when max-ing
>  if static_eval(node) < backed_up_eval(some sibling node, depth) prune node
>
>[for min-ing, flip the compare.]
>
>That sounds a little insane.  Probably it has something to do with their example
>being for a 4-ply search. :-)  Maybe give
>
>(when max-ing)
>  if backed_up_eval(node, depth-1) < backed_up_eval(some sibling node, depth)
>   then prune
>
>a look-see.  What ends up happening with the latter translation of their
>description is that branches that look sucky will get searched one ply less
>deeply.  Of course, it would be possible to perform razoring recursively too.
>
>Dave



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