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Opening problems for AI: Problem 25
http://www.lifein19x19.com/viewtopic.php?f=15&t=17628		 Page 1 of 1
Author:  Bill Spight [ Thu Jul 09, 2020 7:11 am ]
Post subject:  Opening problems for AI: Problem 25
Later in the game, 1620-00-00ap, between Nakamura Doseki (W) and Yasui Santetsu.

White to play.

Click Here To Show Diagram Code
[go]$$Bcm23 White to play. Which way?
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . X . O . . . . . . . X . . . . |
$$ | . . O a . . . . . , . . . . . X X . . |
$$ | . . b 1 . . . . . . . . . . . O O . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . X X X . . . . . . . . . . . . . . . |
$$ | . O X O X X . . . , . . . . O , . . . |
$$ | . . O O O . X . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

How should White reply to the press, :b23:? Should White push through and cut, or should White crawl on the 3d line? Nakamura chose one, but the other was 12% better, according to Elf (assuming komi, which the game did not have, OC).
Author:  lichigo [ Thu Jul 09, 2020 7:51 am ]
Post subject:  Re: Opening problems for AI: Problem 25
I love this series, but I always wonder why not using katago with 0 or 0.5 komi? Why o ly Elfv2?
Author:  pwaldron [ Thu Jul 09, 2020 8:14 am ]
Post subject:  Re: Opening problems for AI: Problem 25
Bill Spight wrote:
Click Here To Show Diagram Code
[go]$$Bcm23 White to play. Which way?
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . X . O . . . . . . . X . . . . |
$$ | . . O a . . . . . , . . . . . X X . . |
$$ | . . b 1 . . . . . . . . . . . O O . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . X X X . . . . . . . . . . . . . . . |
$$ | . O X O X X . . . , . . . . O , . . . |
$$ | . . O O O . X . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]



My first impression was the cut. After thinking a while...I still want to cut. Crawling will leave the white stone on the left overconcentrated and the pincer stone is going to feel pressure, more so with the black hane looming in the top right.

If white cuts then I would expect both sides to settle themselves and white can aim at getting away first to either the top left or bottom right.
Author:  Bill Spight [ Thu Jul 09, 2020 8:49 am ]
Post subject:  Re: Opening problems for AI: Problem 25
lichigo wrote:
I love this series, but I always wonder why not using katago with 0 or 0.5 komi? Why o ly Elfv2?

Because the GoGoD Elf commentaries have already done the heavy lifting, with a large number of rollouts per move. I don't have to spend any time waiting for results.

As for 0 or 0.5 komi, that would be valuable, but I am interested here in how to play under modern conditions. :)

Edit: And why bother with pre-komi games? First, because human opening theory is largely based upon best play in the late 19th century, and a lot of ideas go back even further. And, surprisingly, AI often endorse those plays in those games, komi or no komi. Second, because these games and their mistakes are easier to explain. For me, anyway. But that is because I learned 20th century opening theory, which overestimated side extensions from the 4-4. From AI I have learned that they are mistakes, but I really can't explain why. Now, in the 17th century top players may have made mistakes by playing on the side, but those mistakes I can explain. :)

For example, :b23: in this game may be considered as a refutation of White's extension to C-11. It's not, but it's a good try. If White plays the jump attachment at E-16, C-11 becomes a good play. (Not that Santetsu thought that C-11 was a mistake, but he knew that E-16 would have been a good followup for White.) These are things that I learned at Mother Takagawa's knee. ;)
Author:  Knotwilg [ Thu Jul 09, 2020 12:11 pm ]
Post subject:  Re: Opening problems for AI: Problem 25
With two stones in support no doubt AI will cut
Author:  Shaddy [ Thu Jul 09, 2020 4:37 pm ]
Post subject:  Re: Opening problems for AI: Problem 25
I recall that there's a theme with this side shape that Black can't find a good time to stop pushing White. If he pushes once or twice, hane is severe, three times and the hane is a tiger's mouth, but the fourth push is gote. Also White's push damages the pincer stone, which is unpleasant with the top right shape. I think the computer will crawl.
Author:  Uberdude [ Thu Jul 09, 2020 4:47 pm ]
Post subject:  Re: Opening problems for AI: Problem 25
Knotwilg wrote:
With two stones in support no doubt AI will cut


You mean with that extra stone that will become overconcentrated after pushing and cutting gives black momentum to damage the other one? ;-)
Author:  Bill Spight [ Fri Jul 10, 2020 9:09 am ]
Post subject:  Re: Opening problems for AI: Problem 25
I see that there is great interest in a no komi analysis of these ancient games. :) I think that's wonderful, but I think that assuming komi has relevance for our modern understanding of opening moves, even given positions from games of yore.

Click Here To Show Diagram Code
[go]$$Wcm24 Actual game
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . X . O . . . . . . . X . . . . |
$$ | . . O . . . . . . , . . . . . X X . . |
$$ | . . 1 X . . . . . . . . . . . O O . . |
$$ | . . 3 2 . . . . . . . . . . . . . . . |
$$ | . a 5 4 . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . X X X . . . . . . . . . . . . . . . |
$$ | . O X O X X . . . , . . . . O , . . . |
$$ | . . O O O . X . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

The crawl, :w24:, loses 12% to the push and cut. Elf has a very slight preference for the keima at a instead of :w26:, but White takes gote either way.

Click Here To Show Diagram Code
[go]$$Wcm24 Push and cut
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . X . O . . . . . . . X . . . . |
$$ | . . O 1 2 . 6 7 . , . . . . . X X . . |
$$ | . . . X 3 4 . . . . . . . . . O O . . |
$$ | . . . a 5 . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . W . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . X X X . . . . . . . . . . . . . . . |
$$ | . O X O X X . . . , . . . . O , . . . |
$$ | . . O O O . X . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

Of course White chooses the hane for :w30: instead of a play on the left such as a, which would make the :wc: stone too close. Besides, ceding the top side to Black is unappetizing. ;) The :wc: stone will be helpful if Black plays first in that area.

Click Here To Show Diagram Code
[go]$$Wcm30 Two step hane
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . X . O . . . . . . . X . . . . |
$$ | . . O O X . X 1 5 , . . . . . X X . . |
$$ | . . . X O X . 2 3 . . . . . . O O . . |
$$ | . . 7 . O . . 4 . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . 6 . . . . . . . . . . . . . . . |
$$ | . . W . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . X X X . . . . . . . . . . . . . . . |
$$ | . O X O X X . . . , . . . . O , . . . |
$$ | . . O O O . X . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

Joseki for :w32: is to extend with :w34:, but White continues lightly with a two step hane rather than being pushed towards Black's strength in the top right. After :b33:, :w34: makes a strong, solid connection.

At this point Black has a number of playable moves. If he continues with :b35: in the top left, White secures his group with :w36:.

I think that pwaldron puts it well. The crawl makes the :wc: stone overconcentrated and Black's resultant wall weakens the pincer stone. OTOH, the push and cut works with the :wc: stone, and the contact fight on the top side strengthens the pincer stone. Elf's two step hane is a good tesuji here. :)
Author:  dhu163 [ Fri Jun 04, 2021 10:29 am ]
Post subject:  Re: Opening problems for AI: Problem 25
Speculatively:
Current position:
1. Neither seems that nice. It seems worrying to try to fight when B has such a solid shape in the lower left and fairly solid in the upper right. Hence, I prefer b=C15 instinctively.
2. However, is C11 close enough to support the fight. D16 E16 E15 F15 E14 G16 H16?

Opp to play
1. C15=b of course, trying to kill corner.

Past:
1. B ahead as from discussion in problem 24, B is very solid in lower left and W has nothing much yet.

Check:
1. I keep forgetting lower right but it turns out not to matter this time. The idea seems to be that W is alive and B is not.
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