What is a false eye?

Bill Spight · Post by **Bill Spight** » Thu Dec 16, 2010 12:22 pm

What does the term, false eye, mean to you?

Click Here To Show Diagram Code: [go]$$ False eyes? $$ --------------------------------------- $$ | . O a O X X O O O O O X X O X . X O c | $$ | X X O O X O b O X X O O X O X . X . O | $$ | . O a O X O O X X . X O X O O X X X X | $$ | O O O X X X O X . X X O X . O O O O O | $$ | X X X X . X O O X X O O X . . . O . O | $$ | O O O X . . X O O O b O X . . . . O . | $$ | . . O X . . . X X X O O X . . . . O O | $$ | O O X X X X X . . . X X X . . . . . . | $$ | d O X O O O X . . . . . . . . . . . . | $$ | O X X O . O X . . , . . . . . , . . . | $$ | d O O d O O X . . . . . . . . . O O O | $$ | O O X O O X . X . . . . . . . . O X X | $$ | X X X X X X . . . . . . . . O . O X . | $$ | O O O . . . . . . . . . . . . O X X O | $$ | X X O O O O O . . . . . . O O X X O f | $$ | O X X X X O . O . , O O O O X , X O f | $$ | e O X . X O . O . . O X X X X X X X O | $$ | O O O X X O O . O . O X O O O O X O f | $$ | . O X e X O . . O . O X O . O f O f O | $$ ---------------------------------------[/go]

This diagram shows several eyes that are formed by stones that are not all solidly connected, yet all of the stones may remain on the board at the end of the game. Do you consider any of these eyes false?

Thanks.

hyperpape · Post by **hyperpape** » Thu Dec 16, 2010 12:30 pm

I don't know if I need to hide my answers, but I will.

Li Kao · Post by **Li Kao** » Thu Dec 16, 2010 12:30 pm

b and d are true eyes.
Most of the others I regard as undefined.
Luckily false eyes are no fundamental concept in go, but just something to use as a heuristic helping you with reading or determining the status of a group.

But is it intended that in c white is dead if b moves first?
~~And in f black is simply dead? So f has at least one true eye, the f in the bottom row. Because w can just fill the other fs and remove the black stones.~~ OP was modified

edit:
I think in sekis the concept of an eye loses meaning. I rather think about different kinds of liberties there than about eyes. External, shared and several kinds of private liberties.

Magicwand · Post by **Magicwand** » Thu Dec 16, 2010 12:44 pm

Li Kao wrote: But is it intended that in c white is dead if b moves first?

C is alive because if black want to kill white black will lose more points. (edit: not more points but same.)
therefor it is a seki.

in my opinion a,b,e,f are false eyes

a is a seki. two false eye doesnt count as points in japanese rule
b is a life with false eye. rare but happened few times in acutal game.
c is seki so it not counted as point in japanese rule.
d is an eye because it has complete eye on both end.
e is a seki with double ko.
f is a series of false eye that is not counted as points in japanese rule.

Bill Spight · Post by **Bill Spight** » Thu Dec 16, 2010 12:49 pm

Li Kao wrote:b and d are true eyes.
Most of the others I regard as undefined.
Luckily false eyes are no fundamental concept in go, but just something to use as a heuristic helping you with reading or determining the status of a group.

But is it intended that in c white is dead if b moves first?
~~And in f black is simply dead? So f has at least one true eye, the f in the bottom row. Because w can just fill the other fs and remove the black stones.~~ OP was modified

edit:
I think in sekis the concept of an eye loses meaning. I rather think about different kinds of liberties there than about eyes. External, shared and several kinds of private liberties.

Sorry, I made an incorrect diagram for "f". I have corrected it, now.

As for "c":

Click Here To Show Diagram Code: [go]$$B Furikawari $$ --------------------------------------- $$ | . O a O X X O O O O O X X O X 4 X O 3 | $$ | X X O O X O b O X X O O X O X 2 X 1 O | $$ | . O a O X O O X X . X O X O O X X X X | $$ | O O O X X X O X . X X O X . O O O O O |[/go]

Black can capture the two White stones, but then White can capture two Black stones in return.

jts · Post by **jts** » Thu Dec 16, 2010 1:36 pm

I had assumed that the difference between eyes and false eyes is mainly useful for making live groups; it's a false eye if it doesn't prevent the opponent from completely surrounding the stones on one side of the eye, forcing you to connect. Or, put differently, if a given internal liberty could not be one of the group's final two liberties under stone scoring rules, it's a false eye.

So I would only count "b" as an eye. I wouldn't call "d" an eye because it's not contributing to the life of the group. Say there was a ko threat at a13; if white ignored, that entire group is dead. That's why I would think of those eyes as false.

Bill Spight · Post by **Bill Spight** » Thu Dec 16, 2010 2:23 pm

Second round:

In the diagram below I have made changes. Do the changes alter your classification?

Click Here To Show Diagram Code: [go]$$ False eyes? $$ --------------------------------------- $$ | . O a O X X O O O O . X X O X . X O c | $$ | X X O O X O b O X X O O X O X . X . O | $$ | . O a O X O O X X . X O X O O X X X O | $$ | O O O . X X O X . X X O X . O O O X X $$ | X X X X . X O O X X O O X . . . . O O | $$ | O O . X . X X O O O b O X . . O . O . | $$ | . . O X . . . X X X O O X . . . . O O | $$ | O O X X X X X . . . X X X . . . . . . | $$ | d O X O O O X . . . . . . . . . . . . | $$ | O X X O . O X . . , . . . . . , . . . | $$ | d O O d O O X . . . . . . . . . O O O | $$ | O O X O O X . X . . . . . . . . O X X | $$ | X X X X X X . . . . . . . . O . O X . | $$ | O O O . . . . . . . . . . . . O X X O | $$ | X X O O O . O . . . . . . O O X X O f | $$ | O X X X . O . O . , O O O O X , X O f | $$ | e O X . X O . O . . O X X X X X X X O | $$ | O O O X X O O . O . O X O O O O X O f | $$ | . O X e X O . . O . O X . . O f O f O | $$ ---------------------------------------[/go]

Thanks.

palapiku · Post by **palapiku** » Thu Dec 16, 2010 2:33 pm

Isn't a false eye simply any empty point surrounded by stones of the same color (let's say White) such that Black can eventually play there if White keeps passing?
Edit - ignore this post, I like my next one more.

Dusk Eagle · Post by **Dusk Eagle** » Thu Dec 16, 2010 2:56 pm

In the first diagram, I would not call any of the shapes false eyes. Nevertheless, I would not call a, d, e, or f eyes either. I think of eyes as actually having to contribute to the life of the group, whereas I think of false eyes as places that can eventually have the points squeezed out of them. These may not be the best ways to define them, but it's definitely how I think about it. So for all the intersections d, since that shape is already alive, d can be regarded as points, but not eyes. In the second example, this changes: I would definitely say 'd' are false eyes if black kills the shape, and I might refer to d as being false when the shape is still unsettled, but once white lives, I would no longer refer to d as false eyes.

For the first e, I would say that these are simply kos, not eyes, and since neither side can win these kos, these are neither false eyes nor eyes. In the second example, if white kills black, then I guess both e's can be called eyes for white.

The first diagram's f intersections are tricky. To myself, I don't think of those as false eyes, but if a beginner wanted to know why black isn't dead, I might call them false eyes simply for convenience. On the second board, it once again depends on whether white lives or dies. If black kills white, all the f points could be considered real eyes for black.

Just my 2¢.

palapiku · Post by **palapiku** » Thu Dec 16, 2010 3:01 pm

Actually, isn't a false eye any point surrounded by stones of the same color (let's say White), such what if White keeps passing Black will be able to play on that point - while NOT having captured some of the four surronding White stones?

DrStraw · Post by **DrStraw** » Thu Dec 16, 2010 4:28 pm

The false eye concept is useful primarily as a means of determining the viability of a group during the game. At the end of the game the concept is of little value. At that point the only relevant question is whether the points indicated are points. And that depends on the rule set.

Apoah · Post by **Apoah** » Thu Dec 16, 2010 6:59 pm

F is based on sente. If b moves first then w dies and the other way around, yes?

Bill Spight · Post by **Bill Spight** » Thu Dec 16, 2010 10:45 pm

Click Here To Show Diagram Code: [go]$$ False eyes? $$ --------------------------------------- $$ | . O a O X X O O O O 1 X X O X . X O c | $$ | X X O O X O b O X X O O X O X 6 X . O | $$ | . O a O X O O X X . X O X O O X X X O | $$ | O O O 2 X X O X . X X O X . O O O X X $$ | X X X X . X O O X X O O X . . . . O O | $$ | O O . X . X X O O O b O X . . O . O . | $$ | . 3 O X . . . X X X O O X . . . . O O | $$ | O O X X X X X . . . X X X . . . . . . | $$ | d O X O O O X . . . . . . . . . . . . | $$ | O X X O . O X . . , . . . . . , . . . | $$ | d O O d O O X . . . . . . . . . O O O | $$ | O O X O O X . X . . . . . . . . O X X | $$ | X X X X X X . . . . . . . . O . O X . | $$ | O O O . . . . . . . . . . . . O X X O | $$ | X X O O O . O . . . . . . O O X X O f | $$ | O X X X 4 O . O . , O O O O X , X O f | $$ | e O X . X O . O . . O X X X X X X X O | $$ | O O O X X O O . O . O X O O O O X O f | $$ | . O X e X O . . O . O X 5 . O f O f O | $$ ---------------------------------------[/go]

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all kill.

is sente.

Magicwand · Post by **Magicwand** » Fri Dec 17, 2010 3:21 am

Bill Spight wrote: is sente.

reverse sente 1 point?

Bill Spight · Post by **Bill Spight** » Fri Dec 17, 2010 8:12 am

Magicwand wrote:
Bill Spight wrote: is sente.
reverse sente 1 point?

Reverse sente 4 points.

Click Here To Show Diagram Code: [go]$$ Reverse sente $$ --------------------------------------- $$ | . O a O X X O O O O . X X O X . X O 3 | $$ | X X O O X O b O X X O O X O X 2 X 1 O | $$ | . O a O X O O X X . X O X O O X X X O | $$ | O O O . X X O X . X X O X . O O O X X | $$ | X X X X . X O O X X O O X . . . . O O | $$ | O O . X . X X O O O b O X . . O . O . |[/go]

After

Black has 6 points in the corner minus 1 point, on average, in the unsettled region where she can capture 1 stone or White can capture 2 stones, for at total of 5 points. The original position is worth 1 point, so the reverse sente gains 4 points.

Life In 19x19

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