Opening problems for AI: Problem 25

Bill Spight · Post by **Bill Spight** » Thu Jul 09, 2020 7:11 am

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,

? 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).

lichigo · Post by **lichigo** » Thu Jul 09, 2020 7:51 am

I love this series, but I always wonder why not using katago with 0 or 0.5 komi? Why o ly Elfv2?

pwaldron · Post by **pwaldron** » Thu Jul 09, 2020 8:14 am

Bill Spight wrote:
$$Bcm23 White to play. Which way?
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Click Here To Show Diagram Code
[go]$$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.

Bill Spight · Post by **Bill Spight** » Thu Jul 09, 2020 8:49 am

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,

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.

Knotwilg · Post by **Knotwilg** » Thu Jul 09, 2020 12:11 pm

With two stones in support no doubt AI will cut

Shaddy · Post by **Shaddy** » Thu Jul 09, 2020 4:37 pm

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.

Uberdude · Post by **Uberdude** » Thu Jul 09, 2020 4:47 pm

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?

Bill Spight · Post by **Bill Spight** » Fri Jul 10, 2020 9:09 am

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,

, loses 12% to the push and cut. Elf has a very slight preference for the keima at a instead of

, 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

instead of a play on the left such as a, which would make the

stone too close. Besides, ceding the top side to Black is unappetizing.

The

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

is to extend with

, but White continues lightly with a two step hane rather than being pushed towards Black's strength in the top right. After

,

makes a strong, solid connection.

At this point Black has a number of playable moves. If he continues with

in the top left, White secures his group with

.

I think that pwaldron puts it well. The crawl makes the

stone overconcentrated and Black's resultant wall weakens the pincer stone. OTOH, the push and cut works with the

stone, and the contact fight on the top side strengthens the pincer stone. Elf's two step hane is a good tesuji here.

dhu163 · Post by **dhu163** » Fri Jun 04, 2021 10:29 am

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