Life In 19x19
http://www.lifein19x19.com/

Opening problems for AI: Problem 12
http://www.lifein19x19.com/viewtopic.php?f=15&t=17589		 Page 2 of 2
Author:  Bill Spight [ Sun Jun 28, 2020 2:40 pm ]
Post subject:  Re: Opening problems for AI: Problem 12
A bit more about the three stones

Click Here To Show Diagram Code
[go]$$Bcm9 Moves 9 to 12
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . . . . . . X . . . . |
$$ | . . . , . . . . . , . . . O 1 , X . . |
$$ | . . . . . . . . . . . . . 2 3 . . . . |
$$ | . . . . . . . . . . . . . 4 . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . X . . . , . . . . . O . . . |
$$ | . . . X . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

After :w12: the three stones are too strong for a continued close assault. The exchanges so far have strengthened them. Elf still likes approaching the top left corner for :b13:.

Click Here To Show Diagram Code
[go]$$Bcm13 Variation: White sphere of influence
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . . . . . 4 X . . . . |
$$ | . . . , . 2 . . . , . . . O X , X . . |
$$ | . . 1 . . . . . . . . . . O X . . . . |
$$ | . . . . . . . . . . . . . O . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . 3 . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . X . . . , . . . . . O . . . |
$$ | . . . X . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

In this case :w14: replies to :b13: with the keima extension, which allows Black to pincer with :b15:. Then :w16: makes a nice wall which, with :w14: and the D-17 stone, form a White sphere of influence on the top side. OC, with a 7 point gap it is rather thin.

The odds of winning or losing may not have changed much, but :w14: appears to refute Black's play in the top right. In the game :b13: prevents that development with the turn at 16.

Click Here To Show Diagram Code
[go]$$Bcm13 Moves 13 to 17
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . 4 . 3 . 5 . . 1 X . . . . |
$$ | . . . , . . . . . , . . . O X , X . . |
$$ | . . . . . . . . . . . . . O X . . . . |
$$ | . . 2 . . . . . . . . . . O . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . X . . . , . . . . . O . . . |
$$ | . . . X . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

In fact, with :b13: - :b17: Black makes territory on the top side, countering White's influence there.

Now we come to the Black blunder, :b21:.

Click Here To Show Diagram Code
[go]$$Bcm21 Moves 21 to 28
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . O . X . X . . X X . . . . |
$$ | . . . , . . . . . , . . . O X , X . . |
$$ | . . . . . . . b . . . . . O X . . . . |
$$ | . . O . . . . . . . . . . O 1 . . . . |
$$ | . . . . . . . . . . . . a 3 . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , 2 . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . 4 . . |
$$ | . . . O . . e . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O , . X . . c , . . . . . O . . . |
$$ | . d X X . . . . . 5 . . 7 . 6 . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

:b21: takes away a liberty from the three stones and reduces their influence on the right side. But it does not itself exert much influence on the right side. :w22: freely extends to R-10. :b23:, which appears to be a minor error, does exert more influence there, but :w24: pretty well nullifies it. The game develops normally through :b27:.

At this point Elf gives Black only a 4½% chance of winning with 7½ komi. A tewari in the top right makes Black look overconcentrated there to me. Isn't it easy now to give up those three stones?

:w28: was a counter-hane at a, and Go Seigen actually ended up saving the three stones. Elf prefers b, c, d, or e instead, by about 5% each.
Author:  dhu163 [ Fri Jun 04, 2021 10:06 am ]
Post subject:  Re: Opening problems for AI: Problem 12
Speculatively:
Current position:
1. S15 is very obvious and how could it be bad? W will be harassed more if B gets S15 in sente? R15 seems bad as W is too low on libs.
2. M15 comes to mind but after S15 S17 K17, I don't see what W is doing. M14 K17 N12 seems more appropriate locally.

Opp to play
1. S15 obviously

Past:
1. I much prefer W. B seems to have nothing with bad shape, needing to capture the cutting stones but can't and isn't even much territory if captured.

Check:
1. close enough
Page 2 of 2 All times are UTC - 8 hours [ DST ]
Powered by phpBB © 2000, 2002, 2005, 2007 phpBB Group
http://www.phpbb.com/