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 Post subject: Opening problems for AI: Problem 21
Post #1 Posted: Sun Jul 05, 2020 7:14 am 
Honinbo

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Today's problem is fairly far into the opening. White made a textbook play that loses 14½% according to Elf.

Click Here To Show Diagram Code
[go]$$Wcm38 White to play
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . O . . . . |
$$ | . . . O . . X . . X . . . . O X . . . |
$$ | . . . , . . . . . , . . . O X X X . . |
$$ | . . . . . . . . . . . . . . O . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . O . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . X . . . . . . . . . . . . . . . . . |
$$ | . . . X . . . . . , . . . . . , O . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . . . X . O . . . . . . . . . . . . |
$$ | . . O . . X O . . . . . . . . . X . . |
$$ | . . X . X O . . . . . . . . . . . . . |
$$ | . . X , X O . . . , . . . . . , O . . |
$$ | . . X O O . . O . X . . X . . O . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


Enjoy! :)

_________________
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 21
Post #2 Posted: Mon Jul 06, 2020 8:49 am 
Honinbo

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This game is GoGoD 1600-00-00n, between Honinbo Sansa (W) and Rigen. OC, today's pros are stronger, in no small part because we have learned from their mistakes.

Click Here To Show Diagram Code
[go]$$Bcm37 Textbook shape
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . O . . . . |
$$ | . . . W . . 1 . . X . . . . O X . . . |
$$ | . . . , . . . . . , . . . O X X X . . |
$$ | . . a 2 . . . . . . . . . 4 O . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . O . . |
$$ | . 3 W . . . . . . . . . . . . . . . . |
$$ | . X . . . . . . . . . . . . . . . . . |
$$ | . . . X . . . . . , . . . . . , O . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . . . X . O . . . . . . . . . . . . |
$$ | . . O . . X O . . . . . . . . . X . . |
$$ | . . X . X O . . . . . . . . . . . . . |
$$ | . . X , X O . . . , . . . . . , O . . |
$$ | . . X O O . . O . X . . X . . O . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

These were the days before corners, sides, center, which explains why Sansa had not enclosed the top left corner earlier. But :b37: not only made a base, it threatened to invade White's thin corner position at a. So White protected it with :w38: which, with the :wc: stones made what would later be a textbook shape in the corner. ( :w38: might also have been at a.) :b39: intruded into the corner, a mistake that lost 17½% to par by Elf's reckoning. Then White made the solid connection, :w40:.

Click Here To Show Diagram Code
[go]$$Bcm39 Variation for :b39:
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . 6 . . . O . . . . |
$$ | . . . O . . X . . X . . . . O X . . . |
$$ | . . . , . . . . . , . . 2 O X X X . . |
$$ | . . . O . . . . . . . . 4 1 W 5 . . . |
$$ | . . . . . . . . . . . . . . 3 . . . . |
$$ | . . . . . . . . . . . . . . . . O . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . X . . . . . . . . . . . . . . . . . |
$$ | . . . X . . . . . , . . . . . , O . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . . . X . O . . . . . . . . . . . . |
$$ | . . O . . X O . . . . . . . . . X . . |
$$ | . . X . X O . . . . . . . . . . . . . |
$$ | . . X , X O . . . , . . . . . , O . . |
$$ | . . X O O . . O . X . . X . . O . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

:b39: cuts White in two in the top right, then captures the :wc: stone. :w44: supports his group and threatens the Black base. The White stones in the upper right side have been weakened.


Click Here To Show Diagram Code
[go]$$Wcm38 Key point
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . O 2 . . . |
$$ | . . . O . . X . . X . c . . O X . . . |
$$ | . . . , . . . . . , . . . O X X X . . |
$$ | . . a b . . . . . . . . . 1 O . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . O . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . X . . . . . . . . . . . . . . . . . |
$$ | . . . X . . . . . , . . . . . , O . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . . . X 3 O . . . . . . . . . . . . |
$$ | . . O . 4 X O . . . . . . . . . X . . |
$$ | . . X . X O . . . . . . . . . . . . . |
$$ | . . X , X O . . . , . . . . . , O . . |
$$ | . . X O O . . O . X . . X . . O . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

The solid connection, :w38:, is the key point for White. It radiates strength towards the right side, the top side, and the center, and weakens Black's corner. After :b39: White takes sente in the bottom left quadrant, but a, b, or c would also be good.

_________________
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 21
Post #3 Posted: Fri Jun 04, 2021 10:26 am 
Lives in gote

Posts: 310
Liked others: 47
Was liked: 249
Rank: UK 2d Dec15
KGS: mathmo 4d
IGS: mathmo 4d
Speculatively:
Current position:
1. B12 seems natural, even if B responds, W jumps and there is still some aji with F9 eyeing C6 aji.
2. O14 is solid, but B at C15 is too big.

Opp to play
1. C15 to just live in corner is very powerful
2. O15 also very big.

Past:
1. B has large lower left and W doesn't have much to make up for it. Though R8 is fairly weak and so is upper right corner, they seem stable for now as W isn't that thick. W can probably build something in the centre but I don't know how. I like B a little, but there are several tense situations and I don't know how they will resolve.

Check:
1. not quite

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