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KarlKnechtel

 

BQM42
    Keywords: Life & Death

KarlKnechtel: Haha, I grabbed #42 ;)

In a game I just played on NNGS, the following situation came up in the corner, with me playing white. (I had a few extra stones attached, but the point is that all the external liberties were filled. It was a very strange game - my opponent opened on the 6-5 point!)

[Diagram]
Diag.: What should happen now?

As I understand the Japanese scoring, making seki is worth 8 points for Black here and killing the white group is worth 30 (plus two for each attached stone - so 38 in my case, I think).


[Diagram]
Diag.: What actually happened

After a lot of thought on my part, I played the indicated moves. (Black 3 came almost instantly). After even more thought I decided that I had died in gote. (I still won the game by around 60 points. Like I said, very strange game.)


The question(s): Is this sequence correct? Is the white group indeed dead here? If so, could I have saved it after Black 1? (I'm pretty confident that if White plays first at 1 the group is unconditionally alive.)


I think you can get seki or ko.

--BlueWyvern

[Diagram]
Diag.: Annoying situation

If Black plays at a, White plays b and White has an ugly ko on her hands. If Black plays elsewhere, White plays b and you have seki.

HolIgor: And if White does not play b? Black will have to play b anyway to kill; which brings about more favourable ko.

unkx80: If Black plays at a, White should not play b and leave it as a ten thousand year ko, I think.

OK... but Black 1 was an endgame play. What happens when the game is already "over ten thousand years old", so to speak?


[Diagram]
Diag.: Annoying situation


Suppose there are no other meaningful plays on the board. If Black plays as shown, White must pass (or throw away a stone), fill at a, or take away a shared liberty at b or c. Filling results in death; Black can make a dead farmer's hat shape at b. Taking away a liberty also is deadly; Black takes the ko, White cannot retake (no meaningful ko threats) or fill the other shared liberty (damezumari); and Black captures.

So White passes. If Black passes, the game is over and I think the players must agree it's seki, since obviously neither wants to touch the situation. If Black fills b or c, White captures and is alive.

So Black takes the ko. If White takes a shared liberty, Black connects the ko and White is almost filled with a bulky five and dies.

Therefore White passes again:

[Diagram]
Diag.: Annoying situation

Here White passes at 6 and 8. White 2 at the circled point was captured.


If Black now connects, it's seki - either six-stone shape he can make is living for White:

[Diagram]
Diag.: Annoying situation

After capturing, the circled points are miai for White to divide the space, and Black won't be able to capture inside because of damezumari.


[Diagram]
Diag.: Annoying situation

Similarly here.


If Black passes here (after he takes the ko and White passes) they again have to agree it's seki. If Black tries filling a shared liberty, White can take back the ko and Black eventually dies.

Overall conclusion: With no ko threats elsewhere on the board, the whole thing is definitely seki after best play by both players. I got one out of two moves right, and my mistake only cost 30 points instead of 38. ;)



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