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Subject: Re: Shredder 8 secret: search depth?

Author: Robert Hyatt

Date: 08:09:41 03/24/04

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On March 23, 2004 at 05:05:56, Vasik Rajlich wrote:


>
>Junior, however, appears to come at the problem of selective search via
>extensions rather than reductions. There are some extremely interesting
>discussions about this in the CCC archives. Amir has claimed that the best way
>to search selectively is via extensions. To complete the reductions vs
>extensions thought from above, an extension strategy will have the profile that
>most moves have the same basic search depth, while certain special moves will
>have a higher search depth. The profile of a search based on reductions compared
>to a search based on extensions will be different.
>


It is easy to prove that last statement wrong.

You write a program that only does search depth reductions.  I write a program
that only does extensions.  I can make mine _identical_ to yours.   Where you
reduce, I do nothing.  Where you don't reduce, I extend.  IE if you don't reduce
a check, I extend the check.  We search _exactly_ the same tree.

reductions are simply the inverse of extensions...  what you can do with one,
you can do with the other.  For example, compare shredder tactically to
ChessMaster.  Then compare the depths.  CM is big on extensions... Shredder is
big on reductions and actually probably uses raw forward-pruning in addition...



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