As white, I ended up in the position below and chose to play the marked pincer. This strikes me as a reasonable direction to play, but what should I have expected from the move? If played correctly, can I completely deny black a base and kill? Or is the best that I can hope for is building up influence to use to attack the top right? I expected to kill, but I was not able to do so. However, I ended up profiting nicely from the resulting influence.

Click Here To Show Diagram Code

[go]$$c
$$ +---------------------------------------+
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . X . W . . X . . . . . . . . |
$$ | . . . O . . . . . , . . . . X , X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . . . O O O . . . , . . . . . , O . . |
$$ | . . X X X X . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X X . . . . . . . . . . . O O . . |
$$ | . . O . . . . . . . . . . . . O X . . |
$$ | . . . O . . . . . , . . . . . , X . . |
$$ | . . . . . O . . . . . . . X . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ +---------------------------------------+[/go]

Edit: To show coordinates in the diagram.

now where have i heard that one before? ...anyone who puts himself in a pincer expecting to kill deserves to go straight to Hell, without collecting $50. Did you ask Leela her opinion?

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i shrink, therefore i swarm

Hi BG,

I'm wondering which one is bigger: R13 or K3.
Also curious about Leela/AGZ's evaluations here.

To be fair, this is exactly why I asked the question. My experience in the game indicates that you are right, I do not understand what this pincer does in this situation -- hence the question.

Kind of a silly answer, but here is my take:

Locally, the 3-3 is still open, so black could expect to get territory like this:

Click Here To Show Diagram Code

[go]$$c
$$ +---------------------------------------+
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . 5 3 4 . . . . . . . . . . . . . . |
$$ | . . 1 2 6 X . . . . X . . . . . . . . |
$$ | . . . O . . . . . , . . . . X , X . . |
$$ | . 7 9 0 . . . . . . . . . . . . . . . |
$$ | . 8 O . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . . . O O O . . . , . . . . . , O . . |
$$ | . . X X X X . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X X . . . . . . . . . . . O O . . |
$$ | . . O . . . . . . . . . . . . O X . . |
$$ | . . . O . . . . . , . . . . . , X . . |
$$ | . . . . . O . . . . . . . X . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ +---------------------------------------+[/go]

Not sure if it’s the best option, but it’s one local consideration. Hence, white also has the option of defending:

Click Here To Show Diagram Code

[go]$$c
$$ +---------------------------------------+
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . W . . . . . . . . . . . . . . . |
$$ | . . . . . X . . . . X . . . . . . . . |
$$ | . . . O . . . . . , . . . . X , X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . . . O O O . . . , . . . . . , O . . |
$$ | . . X X X X . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X X . . . . . . . . . . . O O . . |
$$ | . . O . . . . . . . . . . . . O X . . |
$$ | . . . O . . . . . , . . . . . , X . . |
$$ | . . . . . O . . . . . . . X . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ +---------------------------------------+[/go]

And it’s worth as much as what black would get with the 3-3.

If white does this, though, maybe black defends the top:

Click Here To Show Diagram Code

[go]$$c
$$ +---------------------------------------+
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O a . . . . . . . . . . . . . . |
$$ | . . . . . X . . . . X . . . . . . . . |
$$ | . . . O . . . B . , . . . . X , X . . |
$$ | . . . . . b . . . . . . . . . . . . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . . . O O O . . . , . . . . . , O . . |
$$ | . . X X X X . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X X . . . . . . . . . . . O O . . |
$$ | . . O . . . . . . . . . . . . O X . . |
$$ | . . . O . . . . . , . . . . . , X . . |
$$ | . . . . . O . . . . . . . X . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ +---------------------------------------+[/go]

Or black might consider ‘a’ or ‘b’.

In a simple sense, your invasion can be expected to prevent black from getting these top points. The 3-3 is still open, so you can’t expect to prevent black from having a presence in the area.

But if you don’t like black getting the top points, your invasion is one option.

Not really a clear answer, I know, but those are my thoughts.

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be immersed

You certainly can't reasonably expect to kill black f17 (unless he chooses to let you, which he may well do). Looking at the closest stones it's two black versus one white and black to play so it would be more reasonable (but still not) for black to expect to kill you. Like Kirby said this move means black won't make much territory in the left part of the top side. There are several broad strategic choices for black:
- 1. Save the f17 stone by running to the centre which also attacks white h17. f15 jump most straightforward.
- 2. Save the f17 stone by developing local eyeshape. d18 and then c18 is one way and offers white various choices to give you the corner and separate f17 or keep corner and then you make some shape in side and run out (if white e17 atari and e16 connect this passes the choice of corner or connect to black). d18 and e16 could make a ko.
- 3. Sacrifice f17 by jumping in to 3-3.
- 4. Tenuki. White's followups include a) defend corner (d17/18), b) kick at e17 to defend corner and invite blank to extend and be heavy and attacked or else cover on top next, c) cover and connect at f16 to build wall but black could still likelt live in corner, d) develop h17 e.g. g16 / h15 and then black even more likely to sacrifice with 3-3.

A key issue with 1 is what happens to the top left corner: quite often it will become closer to white territory. The runnning group won't make much territory, so the key counter issue is what happens to h17, can black kill it (rare) or get profit (e.g top right solidifed). On this board white has a supporting wall below so fighting looks unprofitable for black (I'd expect black f17 to escape with a weak group, white top left corner to get more solid, white h17 to escape with weak group). If Black directly plays f15 the e17 kick often is good for white to reduce black eyeshape in sente so the black d18 slide before jumping is a common technique (even though it goes against the simplified idea many learn of don't slide before jump as it removes 3-3 aji).

Given White's thickness option 3 of trading for 3-3 is simple and easy. Option 2 seems plausible but complicated. 4: tenuki is fine too: I wouldn't be sad if I played the extension on right, white played another move top left, I got lower extension. Also g9/10 hane is very big for centre power balance.

Thanks everyone for your answers. This was what I was looking for.

Kirby, your answer was very clear -- the problem was that the question I had a hard time articulating exactly what I needed.



I assume that you are asking from white's perspective as an alternative to H17? I agree that those look like big moves, but I'm not sure which is bigger. My best guess is that R13 is bigger because from black's perspective, I think R12 is bigger than K3. Unfortunately, I haven't had the time to get Leela set up. So, I can't answer that part of your question.

i'd say neither of them! and for the same reason in each case: namely, that whoever plays either of them them is extending towards a live enemy, so neither has much effect - they are both yose moves for both players. As an alternative, white N3 would create aji at Q2, so black can't really pincer it, so i reckon white N3 is bigger than K3.

white has other options... black is so thin at the top and so overconcentrated on the left, maybe white should pass to give black a chance to catch up...

...or, since F17 - L17 is 4 spaces wide, white can secure the corner in sente with E17, and even if black is induced to F16, the gap to L17 still won't be secure, which means a later invasion or probe between L3 and P16 would threaten that gap as well as erase the moyo.

other than that, white's left side position looks bizarre; D10,E10,F10 would be better just about anywhere else.

_________________
i shrink, therefore i swarm

R13 is very large, actually. Black R12 would be sente, threatening Q9.

Q9 would start to make use of black's heavy investment on the left, and Leela agrees that black R12 would be big, but it doesn't think it's sente...

As if that weren't confusing enough, Leela started off liking R13, but ended up agreeing with BlindGroup's H17. So is Leela blind too, or is Blindgroup omniscient?

It's all too difficult for me ...

The key question in this game is: how does White use his influence on the left. Invading the top looks like the obvious answer.
A Black move around H16 would negate all White's influence.

White has no weak groups and black has one, so Swim thinks that separating F17 from its friends by H17 or J17 is the way to go.Swim thinks that black H16 doesn't erase much of white's influence, but it does secure black's top, negating the potential gain of white H17, which i guess is what Knotwig means. I was surprised at how much R12 expands black's shadow, but comparing H17-R12 with R13-H16 suggests the former is superior for white.

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i shrink, therefore i swarm