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 Post subject: Opening problems for AI: Problem 16
Post #1 Posted: Wed Jul 01, 2020 12:37 pm 
Honinbo

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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]

:b19: has just invaded the top left corner. Which way does White block? Elf thinks that the difference comes to 21½%.

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— Winona Adkins

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 Post subject: Re: Opening problems for AI: Problem 16
Post #2 Posted: Wed Jul 01, 2020 1:06 pm 
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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 :bc: 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]

:w22: 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]

:b31: forces :w32: and creates aji. After :w34: :b35: 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.

_________________
The Adkins Principle:
At some point, doesn't thinking have to go on?
— Winona Adkins

Visualize whirled peas.

Everything with love. Stay safe.

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 Post subject: Re: Opening problems for AI: Problem 16
Post #3 Posted: Wed Jul 01, 2020 6:06 pm 
Lives in sente
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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.

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 Post subject: Re: Opening problems for AI: Problem 16
Post #4 Posted: Wed Jul 01, 2020 7:06 pm 
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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. :lol:

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The Adkins Principle:
At some point, doesn't thinking have to go on?
— Winona Adkins

Visualize whirled peas.

Everything with love. Stay safe.

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 Post subject: Re: Opening problems for AI: Problem 16
Post #5 Posted: Wed Jul 01, 2020 8:53 pm 
Judan

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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.


This post by Uberdude was liked by 2 people: Bill Spight, zermelo
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 Post subject: Re: Opening problems for AI: Problem 16
Post #6 Posted: Wed Jul 01, 2020 11:05 pm 
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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%.

_________________
The Adkins Principle:
At some point, doesn't thinking have to go on?
— Winona Adkins

Visualize whirled peas.

Everything with love. Stay safe.

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 Post subject: Re: Opening problems for AI: Problem 16
Post #7 Posted: Fri Jun 04, 2021 10:19 am 
Lives in gote

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Speculatively:
Current position:
1. Normally D17 is more efficient locally unless you really need to make life and territory. It seems particularly appropriate here when W has some moyo support for the wall at D8 (quite far away) and B's stone at K17 is weak.

Opp to play
1. My instinct is B should play D17, but reading suggests C16 is better.

Past:
1. Lower left means B probably slightly ahead

Check:
1. as expected

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