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Subject: Re: how to back up the PV with minimal work.

Author: Tord Romstad

Date: 03:54:49 01/21/04

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On January 20, 2004 at 19:48:45, Sune Fischer wrote:

>I'm surprised if a few PV moves can cut down the tree my any significant amount,
>but then again I never understood why IID works.. :)

IID is one of the few concepts even I, who doesn't even adhere to the
"fundamental principle of chess programming" mentioned elsewhere in the
thread, think I am capable of understanding.   :-)

When the remaining depth is big, there is no best move in the hash table,
and it is likely that the search will fail high (typically because the
static eval is above or at least not too far below beta), it makes sense
to make some extra effort to obtain good move ordering for this node,
because it will probably cut down the size of the big subtree considerably.
A good way to do this is to first do a search with reduced depth.  Most
people seem to reduce the depth by 2, but I always had better results with
a reduction of only 1 ply.

Tord



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