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Subject: Re: Threat Extension and Tree Explosion

Author: Andrew Williams

Date: 02:13:42 05/23/02

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On May 23, 2002 at 03:40:29, Steve Maughan wrote:

>I have recently been tinkering with threat extensions (TE).  I'd definitely like
>to include some form of TE but I have encountered some problems of tree
>explosion.
>
>What is happening is that the null move routine is detecting a mating threat and
>I'm extending by one ply at ply[x].  I then try a move (at ply[x]) that doesn't
>aviod the threat. In reply the opponent plays a sub-optimal move at ply[x+1]
>that does not lead to mate even though a forced mating move does exist.  At
>plt[x+2] I then detect a threat and extend again...
>
>This sequence leads to a tree explosion.  Is there any common wisdom as to how
>to avoid this?  Some ideas that I've had are:
>
>1) Only extend by a fraction - inelegant solution IMO
>2) Store the rely to the null move that gave the checkmate and make this the
>Killer move for the next ply - didn't seem to work well - still some tree
>explosion.
>
>Has anyone any ideas?
>
>Thanks,
>
>Steve

Why not restrict your search to one threat extension per line? ie Keep track of
whether you've had a TE in the current path, and if so don't check for it again.

Andrew



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