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Re: [gnugo-devel] move valuation

From: Daniel Bump
Subject: Re: [gnugo-devel] move valuation
Date: Mon, 12 Nov 2001 13:12:33 -0800

Arend wrote:

> There are basically two ways two asign a value to a move, I think the
> technical terms are miai counting and deiri counting. The first compares
> the value of the position before the move was made with the value
> of the position after the move was made; the other is to compare the value
> of the position after a black move with the value of the position 
> after a white move played in the same area.
> If everything is gote, the second way produces values that are twice
> as high.
> If I do not misunderstand the code, GnuGo is inconsistent here. 
> Moves that (OWL-)attack or defend a dragon XYZ produce a value of
> 2 * dragon[XYZ].effective_size. Unless the opponent can save/kill the
> respective dragon in sente, this is deiri counting.
> OTOH, influence_delta_territory clearly uses miai counting.

Strictly speaking you might be correct.

What is the value of the position when there is a critical
dragon on the board? I suppose it is the average of the
two values depending on who gets to move first. Of course
that's double the effective size of the dragon---divided
by two. So using 2*dragon.effective_size seems to imply
that we are using deiri counting from your definition.

BUT I think it's clear that doubling the influence values
to resolve this apparent inconsistency would be a very bad
thing to do. GNU Go already has a tendency to give up
groups it knows it can save because it thinks something
else is bigger. Often it's wrong.


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