From a real game of mine, I had a group in the corner from a 3-3 invasion. My opponent killed it.

Is this group definitely dead? I can't find a way for it to live. Was 2 my mistake? I played it assuming that White needed to reinforce first, after which I could make two eyes.

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[go]$$W Can Black live?
$$ ----------------------
$$ . . . . O O X . 3 . . |
$$ . . . . O X X X . . . |
$$ . . . O . O O X X X 2 |
$$ . . . . . . . O O X 1 |
$$ . . . . . . . . . O . |
$$ . . . . . . . . . . O |
$$ . . . . . . . . . . . |
$$ . . . . . . . . . . . |
$$ ----------------------[/go]

It's not dead, it's at least ko or seki.

It just so happens that Sensei's Library's current article of the week is about exactly this shape: Walkie Talkie Seven

Excellent and extensive analysis there, to which I can add little, other than to say that was indeed a mistake, and should be the 2-1 point

Like this, it's easy life for Black:

Click Here To Show Diagram Code

[go]$$Wc Life
$$ ----------------------
$$ . . . . O O X . . 2 . |
$$ . . . . O X X X . . . |
$$ . . . O . O O X X X . |
$$ . . . . . . . O O X 1 |
$$ . . . . . . . . . O . |
$$ . . . . . . . . . . O |
$$ . . . . . . . . . . . |
$$ . . . . . . . . . . . |[/go]

But with your , it appears ko is best you've got:

Click Here To Show Diagram Code

[go]$$Wc Ko.
$$ ----------------------
$$ . . . . O O X . 3 4 . |
$$ . . . . O X X X . 5 6 |
$$ . . . O . O O X X X 2 |
$$ . . . . . . . O O X 1 |
$$ . . . . . . . . . O . |
$$ . . . . . . . . . . O |
$$ . . . . . . . . . . . |
$$ . . . . . . . . . . . |[/go]

But this ko is better for you, because it's multiple steps for White:

Click Here To Show Diagram Code

[go]$$Wc Better ko.
$$ ----------------------
$$ . . . . O O X . 3 5 6 |
$$ . . . . O X X X . 4 . |
$$ . . . O . O O X X X 2 |
$$ . . . . . . . O O X 1 |
$$ . . . . . . . . . O . |
$$ . . . . . . . . . . O |
$$ . . . . . . . . . . . |
$$ . . . . . . . . . . . |[/go]

After White takes with 7, he can't fill at the 1-1 if he wishes to kill (it's a seki if White gets to fill T15). At the same time, he needs to take care of T15.

@araban: There's no need to play in your second diagram, you can let white start the ko (or make seki)

Ah, indeed. I'm assuming you mean third diagram.

Oh, yeah, third diagram

Click Here To Show Diagram Code

[go]$$W Can Black live?
$$ ----------------------
$$ . . . . O O X . . . . |
$$ . . . . O X X X . . 2 |
$$ . . . O . O O X X X . |
$$ . . . . . . . O O X 1 |
$$ . . . . . . . . . O . |
$$ . . . . . . . . . . O |
$$ . . . . . . . . . . . |
$$ . . . . . . . . . . . |
$$ ----------------------[/go]

Just considering the internal shape, is this way better endgame? Black gets 6 points.

Click Here To Show Diagram Code

[go]$$W Can Black live?
$$ ----------------------
$$ . . . . O O X . . 2 . |
$$ . . . . O X X X . . . |
$$ . . . O . O O X X X a |
$$ . . . . . . . O O X 1 |
$$ . . . . . . . . . O . |
$$ . . . . . . . . . . O |
$$ . . . . . . . . . . . |
$$ . . . . . . . . . . . |
$$ ----------------------[/go]

This way, black can also get 6 points if he gets ''a''. But if white gets ''a'' first, black only has 5.

I don't think it's 'way better', but perhaps it is better. It seems to me that it depends on the value of sente, but I'm terrible when it comes to endgame calculations like this so I'll just hope that Bill Spight crosses by and provides some analysis.

Thanks all! I think I was blasé about defending this because the group was the result of a 3-3 invasion - and a 3-3 invasion can't die, right?

On a related note, it's one of go's fascinations that positions from beginner games still provoke discussion amongst stronger players.



I think he meant 'is it better endgame this way' rather than 'way better.'

Click Here To Show Diagram Code

[go]$$W Can Black live?
$$ ----------------------
$$ . . . . O O X . a b . |
$$ . . . . O X X X . . 2 |
$$ . . . O . O O X X X . |
$$ . . . . . . . O O X 1 |
$$ . . . . . . . . . O . |
$$ . . . . . . . . W . O |
$$ . . . . . . . . . . . |
$$ . . . . . . . . . . . |
$$ ----------------------[/go]

Yes, is optimal in the corner. If White plays at a, Black plays at b, and vice versa. (I have added to tighten up the outside. )

_________________
The Adkins Principle:
At some point, doesn't thinking have to go on?
— Winona Adkins

Visualize whirled peas.

Everything with love. Stay safe.

Click Here To Show Diagram Code

[go]$$W Can Black live?
$$ ----------------------
$$ . . . . O O X . 1 3 . |
$$ . . . . O X X X . 2 5 |
$$ . . . O . O O X X X . |
$$ . . . . . . . O O X 4 |
$$ . . . . . . . . . O . |
$$ . . . . . . . . W . O |
$$ . . . . . . . . . . . |
$$ . . . . . . . . . . . |[/go]

Best play depends upon the ko threat situation. Kos generally favor the invader, because he has fewer stones at stake.

I think that this sequence is normally optimal under Japanese/Korean scoring, as the corner point cannot be a White point.

Click Here To Show Diagram Code

[go]$$W Can Black live?
$$ ----------------------
$$ . . . . O O X . 1 . . |
$$ . . . . O X X X . . 2 |
$$ . . . O . O O X X X . |
$$ . . . . . . . O O X . |
$$ . . . . . . . . . O . |
$$ . . . . . . . . W . O |
$$ . . . . . . . . . . . |
$$ . . . . . . . . . . . |
$$ ----------------------[/go]

Under area scoring, I think that is normally optimal. It is a White sente.

Click Here To Show Diagram Code

[go]$$W Can Black live?
$$ ----------------------
$$ . . . . O O X . O 3 . |
$$ . . . . O X X X 2 1 X |
$$ . . . O . O O X X X . |
$$ . . . . . . . O O X 4 |
$$ . . . . . . . . . O 5 |
$$ . . . . . . . . W . O |
$$ . . . . . . . . . . . |
$$ . . . . . . . . . . . |
$$ ----------------------[/go]

White has a follow-up for seki. Under area scoring Black has 1 point of territory.

(Edited for area scoring.)

_________________
The Adkins Principle:
At some point, doesn't thinking have to go on?
— Winona Adkins

Visualize whirled peas.

Everything with love. Stay safe.