[Computer-go] Definition of single-point eye

Peter Drake drake at lclark.edu
Thu Oct 23 16:19:02 PDT 2014

On Thu, Oct 23, 2014 at 3:38 PM, Robert Jasiek <jasiek at snafu.de> wrote:

> On 24.10.2014 00:17, Peter Drake wrote:
>> An eye is a vacant point, surrounded [orthogonally] by stones of the same
>> color, that can only be filled by simultaneously capturing all of the
>> surrounding stones.
> If it can be filled by the opponent, then it is not an eye.

Isn't A an eye here?


o can play there, but only after filling all of the external liberties.

(Remember, I'm trying to define "eye", not "life").

If it can be filled by the player, then maybe because suicide is allowed.

x could play at A here without suicide. You're right that I should clarify
that the *opponent* can only play there by simultaneously capturing all of
the surrounding stones.

> "capture" is less suitable than "removal".

Capture seems to be the more common term.  One could argue that capturing
consists of playing a stone and then removing some enemy stones, e.g.,
"removal" is the process of taking those stones off the board.

"surrounded" is less exact than "adjacent and only adjacent to".

I'm not sure I understand your wording.

> "empty" is more common than "vacant".

Yes. This is probably leaking in from my coding on my computer Go, where I
want to be sure not to confuse the empty set with the set containing one
vacant point.

> > I'm writing up some "how to play Go" flyers
> Japanese rules? You might use the Simplified Japanese Rules.

AGA rules.

> > Under AGA (and, I think, Chinese) rules, confused players
> > can always keep going until all eyes are one-point eyes.
> So they can do under Japanese rules. So this is of course no reason not to
> use area scoring rules.
> http://home.snafu.de/jasiek/simple.html

AGA rules, of course, allow either area or territory scoring.

One of my issues with Japanese rules (and perhaps the main reason that we
don't use them in Monte Carlo playouts) is that one has to understand life
and death in order to know when to stop playing. This means more rules
explanation for humans and a nasty coding task for computers. Also, what
does Japanese rules do if there is a dispute about what's alive? Even
dan-level players scratch their heads at this, but the best answer I've
found is that Japanese rules require you to play out the situation and then
"unwind" the game so that it doesn't affect the score. Under AGA rules,
continuing to play does not affect the score.

Your rules appear to be largely equivalent to AGA, but with legal suicide
and positional rather than situational superko.

Thanks for the comments,

Peter Drake
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