Life In 19x19

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[go]$$Wc
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . X . , . X . . |
$$ | . . . . . . . . . |
$$ | . . Y . X . , . . |
$$ | . . 7 O . . O . . |
$$ | . . Y . O . , . . |
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ +-------------------+[/go]

In a recent game I connected the marked black stones by playing at b4. It worked out well enough in the game, but would this have been an effective move against a strong opponent?

Peter,

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[go]$$Wc
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . X . , . X . . |
$$ | . . . . . . . . . |
$$ | . a Y . X . , . . |
$$ | . 2 1 O . . O . . |
$$ | . b Y . O . , . . |
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ +-------------------+[/go]

The answer depends on the two cuts, (a) and (b),
and what happens when your opponent decides to cut at one of them, and the follow-ups
which depend on the whole board (as usual ).

For example, if we remove the limited 9x9 size --
if W cuts at (a) with , B has 2 choices: connect at (b) or atari at (c) --
which leads to two possible ladders -- can you see the ladders?

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[go]$$Wc
$$ | . . . . . . . . .
$$ | . c . . . . . . .
$$ | . 3 Y . . . . . .
$$ | . 2 1 O . . . . .
$$ | . b Y . . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .[/go]

Similarly, if W cuts at (b) instead with , B also has 2 choices
and two ladders (at least) to consider.

Does this make any sense?

Also, locally, blocking was the only move for B.
Otherwise, W pushes through with and the result is a disaster for B (broken shape):

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[go]$$Wc tenuki
$$ | . . . . . . . . .
$$ | . . . . . . . . .
$$ | . . Y . . . . . .
$$ | . 3 1 O . . . . .
$$ | . . Y . . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .[/go]

I see. Black can win the cutting stone, but then White can trap Black in a ladder. Or if Black connects, White can also trap Black in a ladder. But Black has the option (atari or connect), and so the chance to make a good choice based on the rest of the board.

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[go]$$Wc
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . X . , . X . . |
$$ | . . . . . . . . . |
$$ | . a Y . X . , . . |
$$ | . 2 1 O . . O . . |
$$ | . b Y . O . , . . |
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ +-------------------+[/go]

On my 9x9 board, if White cuts at B, Black can atari at B2, and White's ladder fails due to the black stone on e5.

If White cuts at A, Black can connect at B2, and White's ladder fails for the same reason. Or, Black can win the b5 stone, but lose the one on c3 (which is what happened in the game).

Either way, Black seems to have come out better than the split you showed in post 3.

PeterPeter wrote:Black can win the cutting stone...

Yes, W also can choose not to make either cut -- it all depends on the whole board (as usual ).

PeterPeter wrote:Either way, Black seems to have come out better than the split you showed in post 3.

Correct -- usually (but not always) letting W push through with is a disaster for B, but there are exceptions.

PeterPeter wrote:On my 9x9 board, if White cuts at B, Black can atari at B2, and White's ladder fails due to the black stone on e5.

Yes, but there are other considerations here.
If W pushes with , there are complications -- can you see them?

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[go]$$Wc
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . X . , . X . . |
$$ | . . . d . . . . . |
$$ | . . X 5 X . , . . |
$$ | . 2 1 O . . O . . |
$$ | . 3 X . O . , . . |
$$ | . 4 . . . . . . . |
$$ | . . . . . . . . . |
$$ +-------------------+[/go]

Variation 1:Variation 2:

I don't like how either of those turn out for Black.

Would you say was a mistake, as it gave White 2 cutting options?

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

PeterPeter wrote:I don't like how either of those turn out for Black.

Would you say was a mistake, as it gave White 2 cutting options?

$$Wc
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . 2 . , . X . . |
$$ | . . . . . . . . . |
$$ | . . 6 . 4 . , . . |
$$ | . . . 5 . . 1 . . |
$$ | . . X . 3 . , . . |
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ +-------------------+

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

I'd say it is a bit of a mistake, yes. That shape (which is called the tower peep) is good for white when there is nearby support (such as the 1 stone), it's good enough that white would want to play the 5 stone last to get it, I think. So doing a bit of crude tewari... Maybe black 6 wasn't the best option.

On the limited space of a 9x9 board though it's hard to say. My gut tells me to answer at C4 or B5 instead but if I'm honest I haven't read it out that much.

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[go]$$Wc
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . 2 . , . X . . |
$$ | . . . 8 . . . . . |
$$ | . . . 7 4 . , . . |
$$ | . . 6 5 . . 1 . . |
$$ | . . X . 3 . , . . |
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ +-------------------+[/go]

I'd perhaps go for something like this. You're cut but you're still alive and the corner is quite big

PeterPeter wrote:I don't like how either of those turn out for Black.

Would you say was a mistake, as it gave White 2 cutting options?

$$Wc
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . 2 . , . X . . |
$$ | . . . . . . . . . |
$$ | . . 6 . 4 . , . . |
$$ | . . . 5 . . 1 . . |
$$ | . . X . 3 . , . . |
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ +-------------------+

Click Here To Show Diagram Code

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

Another possible idea for six with fewing cuts is as below:

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

I would say is the mistake, unless you were actively planning to sacrifice it after .

The main idea here is that Black succumbs to a peep from White.

In such a shape, it's not uncommon for Black to peep:

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[go]$$Bc
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . , . , . , . . |
$$ | . . . W . . . . . |
$$ | . . , a 1 . , . . |
$$ | . . . W . . . . . |
$$ | . . , . , . , . . |
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ +-------------------+[/go]

White typically connects solidly at a, and is strengthened. Peeps are usually a tactical move used to get an outcome that outweighs the strengthening of White. As EdLee pointed out, Black's next move if White ignores the peep will be to push through at a himself (following up on the original threat). This leads to a poor shape for White, with cutting points.

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[go]$$Wc
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . , . , . , . . |
$$ | . . . 1 . . . . . |
$$ | . . , a B . , . . |
$$ | . . . W . . . . . |
$$ | . . , . , . , . . |
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ +-------------------+[/go]

Now what's bad about the diagram above is that where the Black stone is simply there to start with, White has turned it into a peep against his shape on his own turn. Now he does not have time to avoid Black cutting at a. The fact that White has given Black this opportunity by making Black's stone into a peep without making black expend a turn is a big difference from the first diagram.

Now Black can push through and cut at any time, and White still has to spend a turn to defend at a. If doesn't achieve something big, it might have been better at a to begin with.

Falcord wrote:I'd perhaps go for something like this.

$$Wc
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . 2 . , . X . . |
$$ | . . . 8 . . . . . |
$$ | . . . 7 4 . , . . |
$$ | . . 6 5 . . 1 . . |
$$ | . . X . 3 . , . . |
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ +-------------------+

Click Here To Show Diagram Code

[go]$$Wc
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . 2 . , . X . . |
$$ | . . . 8 . . . . . |
$$ | . . . 7 4 . , . . |
$$ | . . 6 5 . . 1 . . |
$$ | . . X . 3 . , . . |
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ +-------------------+[/go]

Falcord, that's very bad for Black.

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[go]$$Wcm9
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . X . , . X . . |
$$ | . 3 5 X . . . . . |
$$ | . 2 1 O X . , . . |
$$ | . 4 X O . . O . . |
$$ | . . X . O . , . . |
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ +-------------------+[/go]

Black's shape is very bad (broken):

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[go]$$Wcm9
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . B . , . X . . |
$$ | . @ @ B . . . . . |
$$ | . B @ @ B . , . . |
$$ | . X B @ . . O . . |
$$ | . . X . O . , . . |
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ +-------------------+[/go]

The original at C4 was bad. The Keima at B5 is better:

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

Greetings,
I don`t know to what extent the rule of thumb applies on a 9x9 but what Ed has just shown is that first, don`t play two stones diagonally with a space in between. That`s bad shape. But, if you do and your opponent cuts, then the correct response is often a keima, as in the diagram above.
Best wishes,
Buri

Hi Buri,

Buri wrote:...first, don`t play two stones diagonally with a space in between. That`s bad shape.

Unfortunately, it's not so simple.
Sometimes, it is good shape; sometimes, it is not.
It depends on the exact board position.

Greetings,
Ed, thanks for the clarification. You are right of course. The shape does crop up and is of no significance in a lot of games. However, without any intention to be disrespectful I would like to reclarify what you say.
As a beginner, I(we) are taught this is -basically- a bad shape. (I am citing here Jennie Shen and Guo Juan). Therefore I respectfully feel that the weighting is a great deal more towards treating it as a bad shape, rather than the sense that it is `sometimes good, sometimes bad` which might suggests to a beginner such as myself that this is a more balanced issue. In Jennie Shen`s lectures on the topic (Guo Juan Internet school) it is treated as essentially bad and that the correct response is almost always a keima. However, the direction of the keima must be selected in relation to the whole board situation.
best wishes,
Buri