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Subject: Re: razoring techniques

Author: Robert Hyatt

Date: 07:24:11 06/14/98

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On June 14, 1998 at 01:27:48, Stuart Cracraft wrote:

>
>On June 13, 1998 at 13:49:42, Peter Kasinski wrote:
>
>>The advantages are obvious.
>>What are the possible negative consequences?
>>What is the right way to implement it?
>>
>>Thank you kindly, as always.
>>
>>PK.
>
>Perhaps we could expand on your post by talking generally
>about "razoring" and what it's all about. Wasn't this coined
>by Beal and is really more an English aphorism? What's
>the rest of the world call it?
>
>--Stuart


I have a vague memory it was coined by Kent/Birmingham years ago.  It
is a mechanism for reducing the depth along branches that are not worth
searching.  When you get to a node within one ply of the quiescience
search (at ply 7 in an 8-ply search, for example), and the current score
is bad enough (below alpha), for each move you can ask "is there any
hope
that this move can recover the lost material?"  If the move is a
non-capture,
non-check, non-tactical-threat, then just drop right into quiesce rather
than another full-width ply before going to the capture search.  The
only
trick is to be *sure* that the move you are reducing the depth on cannot
recover the missing material.

Works well, *if* you control what you razor...



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