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Subject: Re: Mixing alpha-beta with PN search

Author: Klaus Friedel

Date: 03:34:03 01/18/04

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On January 18, 2004 at 06:05:06, Tord Romstad wrote:

>I am considering to implement PN search or one of the many related algorithms in
>my
>engine, in order to use it as a sort of "oracle" for the main search and eval.
>The idea
>is to formulate some sort of goal, and call the PN search to determine whether
>this
>goal could be achieved or not.  For instance, in an endgame position a static
>examination
>of the position could show that white would win if he could manage to bring his
>king to
>g6 without allowing black to sacrifice his knight for white's h pawn, and the
>main search
>could ask the PN search whether this is possible.
>
>My hope is that ideas like this could be used to implement some sort of crude
>long-range
>planning in the endgame.
>
>Has anybody else experimented with similar ideas?  Is it possible to make it
>work?
>
>Tord

I experimented with some combinations of PN and alpha-beta. PN helps finding
forced mates really fast. I tried to switch to PN-search if a forced mate might
be possible. The problem is to detect when to switch to PN.
I also tried to use PN to detect forced draw positions in the endgame.
Another experiment was to use alpha-beta in evaluation function of PN search to
detect possible material gains.

None of the things I tried was really convincing. It works like a charm in some
positions, but simply eats a lot of time and memory in most of the positions.

Nevertheless I think that PN search is a concept with some potential if one
finds a way to reduce its huge memory requirements and find the right goals to
search for.

Bye,
Klaus Friedel



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