White will 100% start the ko. Black's life is threatened as well, and there is no ko threat big enough.

Click Here To Show Diagram Code

[go]$$Wcm134 Move 1 W65 B60
$$ ---------------------------------------
$$ | . . . . . . . O . . . . . . . . . . . |
$$ | . X X O O . O X . . . O . O X . . . . |
$$ | . X O O . O X X . . . X O . O X X . . |
$$ | . X X O O X O X . X X 3 X 1 O O X X . |
$$ | X X O X . X O O X O X B O O 2 X O O O |
$$ | . O O X . . . O . O X O O X X X X X X |
$$ | . . O X . . X . O . X O X . . . . . X |
$$ | . . O X . . . . O X X O X X X X . X X |
$$ | . . O X . . . . O . X X O O X X . . . |
$$ | . X X O X . X . . O O O O X O X X . X |
$$ | . O O O . . . . . . . . . . O O X X . |
$$ | . . . . . X . . . X . . . . . . O X X |
$$ | . . . O . . . . . . . . . . . . O O . |
$$ | . . . . . X . . . . . . . . . . . . . |
$$ | . . X . X . . . . . . . . . . . . . . |
$$ | . . . , . O . . . , . . . . . O . . . |
$$ | . . . O . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

So black will connect, and White will live in sente:
Edit: Just realized I didn't know how Black can live... need to do more reading.

We have to play either here or one above. This has a chance of giving an extra bit of eyespace, so I'll take it.

No choice. Otherwise black plays there and we die.

I'm having trouble seeing a way for this to go better for us than ko. I'm playing this as a sort of a probe. If W plays elsewhere, the ko starts here. If he connects, we get two ko threats against the group when the ko starts next turn. If he doesn't, the ko starts here and we have threats against his top-right group.

Actually, second thought: if W doesn't connect it's not ko, we just kill him with F19. So, two ko threats. And I think W is going to take first, and then gets one internal threat...

Click Here To Show Diagram Code

[go]$$Bcm137
$$ ---------------------------------------
$$ | . . . . . 6 2 O 1 . . . . . . . . . . |
$$ | . X X O O 5 O X . . . O . O X 9 . . . |
$$ | . X O O . O X X . . . X O 8 O X X . . |
$$ | . X X O O X O X . X X 4 X O O O X X . |
$$ | X X O X . X O O X O X X O O 3 X O O O |
$$ | . O O X . . . O . O X O O X X X X X X |
$$ | . . O X . . X . O . X O X . . . . . X |
$$ | . . O X . . . . O X X O X X X X . X X |
$$ | . . O X . . . . O . X X O O X X . . . |
$$ | . X X O X . X . . O O O O X O X X . X |
$$ | . O O O . . . . . . . . . . O O X X . |
$$ | . . . . . X . . . X . . . . . . O X X |
$$ | . . . O . . . . . . . . . . . . O O . |
$$ | . . . . . X . . . . . . . . . . . . . |
$$ | . . X . X . . . . . . . . . . . . . . |
$$ | . . . , . O . . . , . . . . . O . . . |
$$ | . . . O . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

Actually, I'm not sure this ko is winnable for us, either. At least as I've read it out. But if there's any way for us to live here, I think it has a ko component, so having these ko threats will be necessary. And if not, my big brothers will have to save me.

I was going to play this:

Click Here To Show Diagram Code

[go]$$Wc Move 139 W65 B60
$$ ---------------------------------------
$$ | . . . . . . 7 O 6 . . . . . 5 . . . . |
$$ | . X X O O . O X . 8 B O . O X 3 4 . . |
$$ | . X O O . O X X . . 2 X O . O X X . . |
$$ | . X X O O X O X . X X 1 X O O O X X . |
$$ | X X O X . X O O X O X X O O . X O O O |
$$ | . O O X . . . O . O X O O X X X X X X |
$$ | . . O X . . X . O . X O X . . . . . X |
$$ | . . O X . . . . O X X O X X X X . X X |
$$ | . . O X . . . . O . X X O O X X . . . |
$$ | . X X O X . X . . O O O O X O X X . X |
$$ | . O O O . . . . . . . . . . O O X X . |
$$ | . . . . . X . . . X . . . . . . O X X |
$$ | . . . O . . . . . . . . . . . . O O . |
$$ | . . . . . X . . . . . . . . . . . . . |
$$ | . . X . X . . . . . . . . . . . . . . |
$$ | . . . , . O . . . , . . . . . O . . . |
$$ | . . . O . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

No reason for us to fight the ko, we need both and at to kill, right?

But then I thought a bit more... if we start the ko, we need to be sure to win it, otherwise we should play as above. But it would be nice to get something, I don't think we're ahead-- white has so much potential on the bottom.

I'm not sure why jts wants to play where he did... above is itself a ko threat, so we have 3 there if we don't start off by playing the first one.

So we have three threats on top. White has maybe one around the lower left area. So I'm pretty sure we can win the ko. I expect white will let us just eat the top left.

I'm so stupid. If J19 threatens to kill, it's a ko threat.

If W connects every time B plays atari on the large group, and if W answers B ko threats on the left by living, then B has enough ko threats to squeeze W into a dead shape. At that point, capturing the ko no longer helps (B can simply connect), and the 1-2-3 exchange only makes one eye.

But suppose W answers the B ko threat on the left with another ko? That does not live outright, but on the other hand, further B ko threats no longer threaten to kill outright. Then W can ignore a B ko threat to save the large group before it is squeezed to death. This might let W resist a little longer

Edit: On second thought, I guess that just means the first B ko threat should be played inside, at the marked W stone, rather than atari from the outside.

Click Here To Show Diagram Code

[go]$$W
$$ ---------------------------------------
$$ | . . . . . W . O X . . . . X 2 3 . . . |
$$ | . X X O O . O X . . X O O O X 1 . . . |
$$ | . X O O . O X X . . . X O O O X X . . |
$$ | . X X O O X O X . X X . X O O O X X . |
$$ | X X O X . X O O X O X X O O X X O O O |
$$ | . O O X . . . O . O X O O X X X X X X |
$$ | . . O X . . X . O . X O X . . . . . X |
$$ | . . O X . . . . O X X O X X X X . X X |
$$ | . . O X . . . . O . X X O O X X . . . |
$$ | . X X O X . X . . O O O O X O X X . X |
$$ | . O O O . . . . . . . . . . O O X X . |
$$ | . . . . . X . . . X . . . . . . O X X |
$$ | . . . O . . . . . . . . . . . . O O . |
$$ | . . . . . X . . . . . . . . . . . . . |
$$ | . . X . X . . . . . . . . . . . . . . |
$$ | . . . , . O . . . , . . . . . O . . . |
$$ | . . . O . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

Let's capture the ko for our liberty. If black captures the ko back, we can always connect, later.

Would someone please post in hide-comments (or unhidden, if it's certain to not affect the game) whether my last move was slightly better or slightly worse than the connection directly? I know in some similar situations, it's worth capturing, just so your opponent has to blow a ko threat, but wasn't sure if this was the same. For example, is there some downside to forcing our opponents to connect at L17? I'm trying to remove smaller inefficiencies from my game, so I should check my judgement with that of others, occasionally. I don't expect much on this move, just a few words is fine.

Once more into the breach, dear friends...

These have to be our biggest ko threats. I'm pretty confident that the only reason Daniel smacked me down before was that I was wasting it.

Looking ahead... they're going to have to use their O17 ko threat soon. We can respond with O19, they retake, we make another threat against the left top group, he connects at N18, and then we have to choose between L18 and Q18. I'm pretty sure that if we let W take L18, W has miai of connecting to the left top group and living locally. (It will be hard to get seki, even, given that W can make an eye more easily than we can.) If we let W get q18, we have a choice between a new ko and trying to kill W with a big eye. I'm pretty sure that we can prevent W from getting an eye in the corner, though. I'll need to read this more carefully when we have to make these choices, but I'm getting confident that mechanically, the conclusion of the ko works in our favor.

This leaves the question of whether W has any big non-local ko threats. Threats against our top left are ok compensation for W, but considering that our capture is bigger and we get sente to move to the bottom, W probably won't even make any threats here. What about threats to cut at F7 and D5? Or H8? I'm going to say that D5 is small. I'm counting 24 pts in the corner, which is what we get from capturing O16 alone. F7 and H8 are harder to say... they're big, but the ko is worth at least 54 points (our stones plus O16), and possibly as much as 75 (the full value of losing the entire top minus getting the entire top).

Do we have big non-local ko threats? B11 is worth about 30 points. That's not horribly big. I don't think that any plays on the open bottom are urgent enough to be ko threats for either side. I think we need to ignore all of their outside threats.

Response to jts' hidden comments: O17 is not a ko threat for white, we would just connect at Q18 and white would die.

I think white will L17 next, giving us the little group. I still don't think white has the threats to win the ko. Violence agrees, it seems, or he would have stopped us.