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Subject: Re: Iterative deepening -- Why add exactly one ply?

Author: Robert Hyatt

Date: 06:29:37 05/25/04

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On May 25, 2004 at 07:59:33, Tord Romstad wrote:

>In all implementations of iterative deepening I have seen, the search depth
>is always incremented by exactly one ply between each iteration.  Is there any
>reason to believe that this is optimal?  Has anybody tried other increments?
>
>I am now running some tests with an increment of 3/4 of a ply.  So far, the
>results don't seem very different from the usual 1 ply increment.  If it turns
>out that increments different from 1 ply are no worse, this could perhaps be
>useful in time management.  The engine could use 1 ply increments most of the
>time, but occasionally add only half a ply if just a small amount of the
>allocated thinking time is left.
>
>Any thoughts about this?
>
>Tord


There's no reason, really, except that "in the good old days" (when this was
first discovered), nobody had thought about fractional plies.

I ran a series of tests several years ago, trying everything from .5 to 1.5, and
nothing particularly stood out.  Sometimes .5 to .75 works better sometimes it
was worse...

Varying the inc is a reasonable idea that should be examined....



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