Re: computer-go: Evaluating positions

["Eric Boesch" <ericboesch@xxxxxxxxxxx>]

Heikki Levanto <heikki@xxxxxxxxxxxxxxxxx> wrote:
> On Sun, Jun 17, 2001 at 09:33:49PM +0200, Vlad Dumitrescu wrote:
> > In the end, the list came down to two items, that are independent as far
> > as I can tell (for statical evaluation):
> >     - influence (of a group)
> >     - strength (of a group); this includes life/death
>
> I am not sure I buy this. For the first, I believe those two are related.
> A strong group radiates more influence than a group that have many
> weaknesses, because the opponent can get to threaten those weaknesses, and
> thus play many stones to neutralize the influence, in sente.
>
> When the game is over, it all comes down to a balance of territory. In the
> middle game you could consider actual territory (inside groups), that is
> more or less secure (the group more or less alive), and potential territory
> that is more or less likely to become yours. Influence affects both, in 
> that
> it weakens enemy groups (allows you to attack more fiercely), and lays
> claims to areas that may well end up as your territory.
I agree with Heikki.

Since a percent-alive statistic is in common use, it seems natural to 
multiply this statistic by the group's influence.  Do others do this?  
(Actually, I use two percent-alive statistics, depending on whether the 
group is attacked or defended first.)

Multiplication immediately discourages the undesirable behavior of, "If I 
place a stone here, it will have so much influence, that it more than 
compensates for the fact that it is dead."  (Yes, a dead stone can have 
useful influence, but even so, its usefulness probably will be proportional 
to its percent-alive statistic anyhow.  In a recent rec.games.go example, 
someone advocated placing a dead stone, but it was a move away from 
escaping.)

Incidentally, in the Japanese game, the percent-alive statistic is useful 
for determining when to pass.  A black stone that is 40% alive is worth .6 
points for white.  If the stone's effect on other stones is not worth .6 
points for Black, it should not be placed.

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