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Subject: Re: razoring?

Author: David Blackman

Date: 02:32:39 08/17/99

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On August 16, 1999 at 17:47:10, Dave Gomboc wrote:

>On August 16, 1999 at 10:22:14, Bas Hamstra wrote:
>
>>What good is razoring? How safe is it? Pros en cons?
>
>It prunes at depths 1 to n-1 instead of from depths 2 to n, so it speeds things
>up a lot.  It isn't a safe heuristic like alpha-beta.  It will blow up in
>zugzwang positions, just like null-move.
>
>Dave

My impression is it can blow up in all sorts of positions, and usually does it
even worse than null-move. It does prune away a lot of branches, which helps you
get deeper. But too many of the branches it prunes seem to be important ones.
Use with extreme caution, and only near the leaves of the tree.

My program used to do razoring at most depths, but it made too many tactical
errors. Then it only did razoring when a few complicated heuristics said it
would probably be safe. This helped on some tactical test suites but apparently
not in real games. Now it doesn't do razoring at all, and it is stronger, but
still not as strong as i'd like.



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