Life In 19x19

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[go]$$Bc White to play
$$ | . . . . . . . .
$$ | . . O . . . . .
$$ | . X O 1 . . . .
$$ | . X X O . . . .
$$ | . O O X X . . .
$$ | . . O . . . . .
$$ | . O X X X O . .
$$ | . . O . . . . .
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ +----------------[/go]

White's best reply to ? (Yes, mistakes have been made by both sides up to this point. And I didn't get the right move in the game: many more mistakes were made by both sides.)

Edited to add: all ladders are in white's favour.

I would call this a "joseki" problem, not a tsumego problem, I suppose it arose like this.

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[go]$$Bc Old joseki
$$ | . . . . . . . .
$$ | . . . , . . . .
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ | . . . 6 . . . .
$$ | . . 2 5 7 . . .
$$ | . . 8 . . . . .
$$ | . . . 1 9 4 . .
$$ | . a 0 . . . . .
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ +----------------[/go]

elsewhere

This is a double approach joseki. is old fashioned. The modern (but pre-AI) play is the keima at a.

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[go]$$Bcm11 Old joseki, continued
$$ | . . . . . . . .
$$ | . . . , . . . .
$$ | . . 8 . . . . .
$$ | . 7 4 9 . . . .
$$ | . 5 3 W . . . .
$$ | . 6 O X X . . .
$$ | . . O . . . . .
$$ | . 2 1 X X O . .
$$ | . . O . . . . .
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ +----------------[/go]

I suppose the ladder works.

But I doubt if White can afford to abandon the stone.

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[go]$$Wcm20 This ladder
$$ | . . . . . . . .
$$ | . . b , . . . .
$$ | . . O 2 . . . .
$$ | . X O X . . . .
$$ | . X X O 1 a . .
$$ | . O O X X . . .
$$ | . . O . . . . .
$$ | . O X X X O . .
$$ | . . O . . . . .
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ +----------------[/go]

is a well known tesuji. Actually, there are two ladders, aren't there?

I suppose the ladder works.

Thanks, Bill.

The local study is interesting; also curious about the whole board evaluations.

xela, I could imagine you made the wrong reply to black 3, but to black 1?!

Uberdude wrote:xela, I could imagine you made the wrong reply to black 3, but to black 1?!

The curse of looking ahead: I could visualise the position after black 3, saw that the ladders were against me, but couldn't see the next move for white. So I didn't go down that path. Instead I went for a trade (there was interesting stuff happening in the top left corner too, but I can't remember enough of the game to be worth posting).

xela wrote:

Uberdude wrote:xela, I could imagine you made the wrong reply to black 3, but to black 1?!

The curse of looking ahead: I could visualise the position after black 3, saw that the ladders were against me, but couldn't see the next move for white. So I didn't go down that path. Instead I went for a trade (there was interesting stuff happening in the top left corner too, but I can't remember enough of the game to be worth posting).

A couple of things. First, just because Black has the option of capturing some White stones is not a reason not to sacrifice them. As you said, you made a trade. If you give up the stones on the left side, the five Black stones to the right are still cut off and attackable. As it happens, the damezumari is very bad for those stones. But if not, White could still attack them. Giving up the single stone, however, unites all the Black stones. That stone is hard to sacrifice.

Second, something that I noted without reading is the vulnerability of the bamboo joint. If it is threatened, the threat and connection take away two dame. So in the position you show, the stones connected by a bamboo joint appear to have 6 liberties. But you have to subtract two for the connection, leaving 4 liberties (or allowing the cut). Wilcox says that stones with five dame are alive in a fight. That's not always so, but stones with only 4 dame are vulnerable. Extending from the stone leaves them with 3 dame (or allows cut). Then the hane leaves them with 2 dame. Bingo!

The shortage of liberties in this bamboo is very similar to this non-joseki variation punishment http://josekipedia.com/#path:pdqfqindpf ... ohphoioepe (though weirdly josekipedia doesn't continue with the ladder at q18 going for an unncessary compromise!), which explains why joseki is q15 pole connection even though it makes an empty triangle, and bamboo at p16 is worse.

Bill Spight wrote:...something that I noted without reading is the vulnerability of the bamboo joint. If it is threatened, the threat and connection take away two dame. So in the position you show, the stones connected by a bamboo joint appear to have 6 liberties. But you have to subtract two for the connection, leaving 4 liberties...

This has been a blind spot for me (using the past tense because, now we've had this conversation, I'll never get it wrong again). I simply didn't see the black stones as attackable. I saw them as having plenty of liberties, with white F4 being blighted.

And here we have a nice case study: the AI told me I'd missed something interesting in the position, but the conversation with humans showed up the underlying gap in my thought process :-)

Even if black didn't push to reduce his liberties and missed the hane for white 4, I'd still imagine trades like this:

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

Here's another one. Again I didn't find the move in the game, but KataGo showed me an interesting way to connect.

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[go]$$Bc
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . . O O O . . . . . . . . . . . . . |
$$ | . . . O X . X . . . . X . . . X . . . |
$$ | . O . . X . X . . X . . . . . . . . . |
$$ | . X O O X . . . . . . O . . . . . . . |
$$ | . X X X O O O . . O . . . 2 . X . . . |
$$ | . . . . X X O . . . . 1 a . . . . . . |
$$ | . . . X . O . . . . . . . . . . . . . |
$$ +---------------------------------------+[/go]

I wimped out and played at a not realising I could jump a bit further. After , how does black connect to safety?

My first thought:

Yes, that seems to work too, but KataGo showed me something much more stylish!

It's easy to connect with the standard shape of kosumi or attach against the White knight move, though there may be better moves given White's thinness and Black's support above. But I would be more concerned with reading counters (or evaluating the natural trade) to this White resistance.

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[go]$$Bc
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . . O O O . . . . . . . . . . . . . |
$$ | . . . O X . X . . . . X . . . X . . . |
$$ | . O . . X . X . . X . . . . . . . . . |
$$ | . X O O X . . . . . . O . . . . . . . |
$$ | . X X X O O O . . O . . . . 2 X . . . |
$$ | . . . . X X O . . . . 1 . . . . . . . |
$$ | . . . X . O . . . . . . . . . . . . . |
$$ +---------------------------------------+[/go]

xela wrote:Here's another one. Again I didn't find the move in the game, but KataGo showed me an interesting way to connect.

$$Bc
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . . O O O . . . . . . . . . . . . . |
$$ | . . . O X . X . . . . X . . . X . . . |
$$ | . O . . X . X . . X . . . . . . . . . |
$$ | . X O O X . . . . . . O . . . . . . . |
$$ | . X X X O O O . . O . . . 2 . X . . . |
$$ | . . . . X X O . . . . 1 a . . . . . . |
$$ | . . . X . O . . . . . . . . . . . . . |
$$ +---------------------------------------+

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[go]$$Bc
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . . O O O . . . . . . . . . . . . . |
$$ | . . . O X . X . . . . X . . . X . . . |
$$ | . O . . X . X . . X . . . . . . . . . |
$$ | . X O O X . . . . . . O . . . . . . . |
$$ | . X X X O O O . . O . . . 2 . X . . . |
$$ | . . . . X X O . . . . 1 a . . . . . . |
$$ | . . . X . O . . . . . . . . . . . . . |
$$ +---------------------------------------+[/go]

I wimped out and played at a not realising I could jump a bit further.

Here is where Sonoda's theory of diagonal lines might have helped.

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[go]$$Bc
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . . O O O . . . . . . . . . . . . . |
$$ | . . . O X . X . . . . X . . . X . . . |
$$ | . O . . X . X . . X . . . . . . . . . |
$$ | . X O O X . . . . . . O . . . . . . . |
$$ | . X X X O O O . . O . . 1 . . X . . . |
$$ | . . . . X X O . . . . a . . . . . . . |
$$ | . . . X . O . . . . . . . . . . . . . |
$$ +---------------------------------------+[/go]

It is obvious that is OK, so why not a? Worth checking out.

After , how does black connect to safety?