Life In 19x19

Posted: **Wed Jul 01, 2020 12:37 pm**

Today's problem comes from GoGoD 2009-06-26c, Game 1 of the 34th Gosei final between Yuki Satoshi (W) and Cho U. An earlier position has recently been discussed by John Fairbairn at https://www.lifein19x19.com/viewtopic.php?f=13&t=17600 .

Click Here To Show Diagram Code: [go]$$Bcm19 White to play $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . 1 . . . . . . X . . . . . . . . . | $$ | . . . O . . . . . , . . . . . X . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . X . . | $$ | . . O . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . . , . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . O . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . O . . | $$ | . . . . . . . . . . . . . . . . X O . | $$ | . . X , . . . . . , . . . . O , X O . | $$ | . . . . X . . . . . X . . . . X O . . | $$ | . . . . . . . . . . . . . . . . O . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

has just invaded the top left corner. Which way does White block? Elf thinks that the difference comes to 21½%.

Posted: **Wed Jul 01, 2020 1:06 pm**

Click Here To Show Diagram Code: [go]$$Wcm20 White takes solid territory, loses percentage points $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . X . . . . . . B . . . . . . . . . | $$ | . . 1 O . . . . . , . . . . . X . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . X . . | $$ | . . O . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . . , . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . O . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . O . . | $$ | . . . . . . . . . . . . . . . . X O . | $$ | . . X , . . . . . , . . . . O , X O . | $$ | . . . . X . . . . . X . . . . X O . . | $$ | . . . . . . . . . . . . . . . . O . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

Black takes the corner in either case, but this way White nails down solid territory instead of building a wall facing the

stone. But this way loses 21½% by comparison with the other way, according to Elf, a huge difference.

Click Here To Show Diagram Code: [go]$$Wcm22 Mainline for :w22: $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . 4 . . . . . . . . . . . . . | $$ | . . X X 2 1 . . . X . . . . . . . . . | $$ | . . O O 3 . . . . , . . . . . X . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . X . . | $$ | . . O . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . . , . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . O . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . O . . | $$ | . . . . . . . . . . . . . . . . X O . | $$ | . . X , . . . . . 5 . . . . O , X O . | $$ | . . . . X . . . . . X . . . . X O . . | $$ | . . . . . . . . . . . . . . . . O . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

takes sente and then reduces the bottom side.

Click Here To Show Diagram Code: [go]$$Wcm20 Mainline variation: White makes outside strength $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . 0 8 9 . . . . . . . . . . . . . . | $$ | . . X 1 . . . . . X . . . . . . . . . | $$ | . . 2 O . . . . . , . . . . . X . . . | $$ | . 4 3 6 . . . . . . . . . . . . . . . | $$ | . 5 7 . . . . . . . . . . . . . X . . | $$ | . . O . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . . , . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . O . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . O . . | $$ | . . . . . . . . . . . . . . . . X O . | $$ | . . X , . . . . . , . . . . O , X O . | $$ | . . . . X . . . . . X . . . . X O . . | $$ | . . . . . . . . . . . . . . . . O . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

Click Here To Show Diagram Code: [go]$$Wcm30 Mainline variation, II $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . X X O . . . . . . . . . . . . . . | $$ | . . X O . 1 . . . X . . 6 . . . . . . | $$ | . 4 X O . 3 . . . , . . . . . X . . . | $$ | . X O X 2 . . . . . . . . . . . . . . | $$ | . O O . . 5 . . . . . . . . . . X . . | $$ | . . O . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . . , . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . O . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . O . . | $$ | . . . . . . . . . . . . . . . . X O . | $$ | . . X , . . . . . , . . . . O , X O . | $$ | . . . . X . . . . . X . . . . X O . . | $$ | . . . . . . . . . . . . . . . . O . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

forces

and creates aji. After

protects the Black framework and makes territory.

Click Here To Show Diagram Code: [go]$$Wcm36 Mainline variation, III $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . X X O . . . . . . . . . . . . . . | $$ | . . X O . O . . . X . . X . . . . . . | $$ | . X X O . O . . . , . . . . . X . . . | $$ | . X O X X . . . . . . . . . . . . . . | $$ | . O O . . O . . . . . . . . . . X . . | $$ | . . O . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . . , . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . O . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . 5 . . . . . . . . . . . . . O . . | $$ | . . 3 4 . . . . . . . . . . . . X O . | $$ | . 6 X , 2 1 . . . , . . . . O , X O . | $$ | . . . . X . . . . . X . . . . X O . . | $$ | . . . . . . . . . . . . . . . . O . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

Then White plays a nice combination against the bottom left corner. This is a kind of joseki.

Posted: **Wed Jul 01, 2020 6:06 pm**

Maybe the principle is that it is almost always right to choose the variation that properly seals off the invading group. White's strength here is not much less than if he blocked in the other direction, but both the black corner and the black top side is much smaller.

Posted: **Wed Jul 01, 2020 7:06 pm**

Harleqin wrote:Maybe the principle is that it is almost always right to choose the variation that properly seals off the invading group. White's strength here is not much less than if he blocked in the other direction, but both the black corner and the black top side is much smaller.

My rule of thumb is to choose the alternative that looks worse for you.

Posted: **Wed Jul 01, 2020 8:53 pm**

Huh, if White blocked on the left I thought he was going to double hane to retake the corner territory. I've seen that idea before when black has the top side stone meaning black can extend the cutting stone in sente if you block the right and follow the usual joseki. It's better if the top side stone is closer though, as then it ends up too close to the ponnuki. Suppose White preferred to get sente here.

Posted: **Wed Jul 01, 2020 11:05 pm**

Uberdude wrote:Huh, if White blocked on the left I thought he was going to double hane to retake the corner territory. I've seen that idea before when black has the top side stone meaning black can extend the cutting stone in sente if you block the right and follow the usual joseki. It's better if the top side stone is closer though, as then it ends up too close to the ponnuki. Suppose White preferred to get sente here.

Yeah, Elf thinks that line loses 4½%.

In the actual game White played the first hane but then extended, losing another 3½%.

Posted: **Fri Jun 04, 2021 10:19 am**

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