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Subject: Re: One mate to solve... that now is very easy.

Author: Paul

Date: 15:12:01 05/07/01

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On May 07, 2001 at 18:04:11, Paul Byrne wrote:

>I think the Allis thesis (chapter 2 in particular) is the best introduction
>I have seen to PN search...

I've installed GhostView this afternoon, and am reading the thesis as we speak.
:)

>Yes, PN search keeps the entire search tree in memory.  One way to save memory
>is to delete any solved subtree once you update the parent's values, since it
>will no longer be needed -- that way you can recycle the nodes and get a
>longer search.  This makes extracting a pv afterwards rather difficult though.
>
>Without that, you could get a pv -- although you would have to do some searching
>in the tree to get the shortest line.  However, PN search tends to produce
>some very non-optimal lines since it will search forcing lines quite deeply,
>so the pv and mate-in-n number won't be very reliable.
>
>Classic situation is in an endgame where the opponent's king is forced into a
>corner so the opponent only has one legal move on each turn.  PN search can
>produce lines hundreds of moves long in which the pieces not needed to corner
>the king wander at random around the board, just enough to avoid repetition
>draws.  Adding a small depth factor will limit this.
>
>-paul

Ok ... I understand, thanks for taking the time to explain! Promises to be an
interesting read ...

Paul



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