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Subject: Re: Deep Search Extension

Author: Heiko Mikala

Date: 13:11:06 01/22/98

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Thank you (and Robert) very much for your detailed explanations.

I will try this for sure as soon as I find the time for it.

On January 22, 1998 at 05:03:38, Ernst A. Heinz wrote:

>Donninger's idea is to extend the search one ply if a null move near the
>horizon (e.g. at depths <= 3) does not fail high and the null move score
>plus a constant margin (e.g. minor piece value) is <= alpha while the
>static evaluation at the node is >= beta (i.e. fails high). In order to
>get meaningful results for the null move score, you need to do it with a
>full alpha-beta window instead of a zero window (this is a known error
>in Donninger's original article).

Whoops... so my questions were going into the right direction...
And this sounds reasonable to me. If my position is very good and by
doing nothing it becomes very bad in only a few moves (reduced depth
for null move and depth<=3), than there has to be a threat which could
be overseen by the normal search because it falls behind the horizon,
if i do the "right" delaying move in my last full width ply.
Is this the basic idea behind it?

>Citing from my article about how "DarkThought" plays chess:
>In order to avoid possibly explosive growth of the search tree as caused
>by excessive deep search extensions in the case of repeated mutual
>mating threats, "DarkThought" restricts them to null moves at depth = 2
>in the first "2 * iteration-number" plies on all paths.

Good tip, will try it.



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