Trying to insert a little go discussion into the board.

I was following a Shusaku discussion in another thread and got pointed towards an analysis of a game posted at https://senseis.xmp.net/?InvincibleTheGamesOfShusaku%2FGame35AnalyzedWithKataGo.

There was an interesting comment about the diagram below that to me was very non-intuitive. White 20 (top left) is commented as being "on the wrong side of the corner". The commentator, Sanno, recommends a 4-4 or 3-3 instead on the grounds that the top is influenced by Black and so White should emphasize the corner.

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[go]$$B
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . 6 . . . . 4 . |
$$ | . . . . . . . . . . X . . . O O 2 3 . |
$$ | . . . , . . . . . , . 7 . 1 X O X 9 . |
$$ | . . . 0 . . . . . . . . . . O X X . . |
$$ | . . . . . . . . . . . . . . 8 O . . . |
$$ | . . . . . . . . . . . . . . . . 5 . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

This commentary is presumably pre-AI, but it still surprised me. My intuition would be that, with Black stones already on the top side, Black would be in some danger of being overconcentrated if he approached into the corner and gave White a press. Accordingly, if the corner approach isn't interesting then White would do well to emphasize the right side.

Regardless, would anyone suggest what I'm missing?

The move looks reasonable to me and I wouldn't say it is on the "wrong" side of the corner. I would also not say black could be overconcentrated, black is about to attack the three cutting stones and if that happens the game will be more dynamic and efficiency will not be what is most important.

It doesn't look like a critical moment to me and one should, therefore, be able to come up with an Good-Enough_tm move fairly quickly.

Likely moves in the first half of the 19th century could be A or C. If you don't like to be on the inside when black approaches then C, and A if you don't like to be on the outside when black approaches from the inside. B or D have a similar feeling.

Liking the outside makes sense to me, black played many stones on the outside so far. Black could dominate the center if white doesn't counter it with high stones but it doesn't feel like this is critical right now.

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[go]$$B
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . O . . . . O . |
$$ | . . d a . . . . . . X . . . O O O X . |
$$ | . . . b . . . . . , . X . X X O X X . |
$$ | . . . c . . . . . . . . . . O X X . . |
$$ | . . . . . . . . . . . . . . O O . . . |
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
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$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

As the author of the Sensei's page, I must point out that it's written as a synthesis of 1) the game 2) The comments of Sanno 9p 3) As transcribed - faithfully I'm sure - by John Power 3) KataGo's analysis, with a certain number of playouts 4) my interpretation, being a 2d.

So, let me give facts first, my opinion next.

FACTS

Click Here To Show Diagram Code

[go]$$Bm11 Sanno's comment on White 20
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . 6 . . . . 4 . |
$$ | . . . . . . . . . . X . . . O O 2 3 . |
$$ | . . . , . . . . . , . 7 . 1 X O X 9 . |
$$ | . . . 0 . . . . . . . . . . O X X . . |
$$ | . . . . . . . . . . . . . . 8 O . . . |
$$ | . . . . . . . . . . . . . . . . 5 . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |[/go]

is the wrong direction. If White is going to play here at all, the correct move is either the star point or the 3-3 point.

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[go]$$W Sanno's suggestion for White 20
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . O . . . . O . |
$$ | . . 1 . . . . . . . X . . . O O O X . |
$$ | . . . , . 2 . . . , . X . X X O X X . |
$$ | . . 3 . . . . . . . . . . . O X X . . |
$$ | . . . . . . . . . . . . . . O O . . . |
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |[/go]

The modern idea would be to take the 3-3 point. If then . Note that instead of ...

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[go]$$W Sanno's suggestion for White 20
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . 5 . . . . . . . O . . . . O . |
$$ | . . 1 . . . . . . . X . . . O O O X . |
$$ | . . 3 2 . . . . . , . X . X X O X X . |
$$ | . . . 4 . . . . . . . . . . O X X . . |
$$ | . . . . . . . . . . . . . . O O . . . |
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |[/go]

here would be wrong, as would counteract Black's thickness on the right.

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[go]$$W KataGo's evaluation of White 20
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . b . |
$$ | . . . . . . . . . . . . O . . . . O a |
$$ | . . . e . . . . . . X . . . O O O X . |
$$ | . . . . . . . . . , . X . X X O X X . |
$$ | . . . 1 . . . . . . . . . . O X X . . |
$$ | . . . . . . . . . . . . . . O O . . . |
$$ | . . . . . . . . . . . d . . . . X . . |
$$ | . . . . . . . . . . . . . . c . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |[/go]

KataGo's evaluation of is that Black leads the no komi game by 6.5. Its preferred move for Black next is in the diagonally opposite corner. Black can exchange A for B first (and anytime, my words). Other options are taking control of the upper right with C or D or other moves in that area. Or Black can invade the upper left at E, as he did in the game. Or he can occupy the other open corner in the lower left. All of these moves fall within a margin of 1 point of his preferred move. While I'm writing this, the playouts exceed 10k for the better candidates but don't go beyond a few hundreds for the rest.

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[go]$$W KataGo's suggestion for White 20
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . O . . . . O . |
$$ | . . . . . . . . . . X . . . O O O X . |
$$ | . . . 3 . . . . . , . X . X X O X X . |
$$ | . . . . . . . . . . . . . . O X X . . |
$$ | . . . . . . . . . . . . 1 . O O . . . |
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . 2 . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |[/go]

KataGo suggests to play first, upon which he has Black reinforce at (my term) and then occupy the open corner at
Another option is to play at which leads to a sacrifice, or playing immediately. These 3 options fall within 0.1 or 0.2 points of each other. While writing this, the sacrifice variation is taking the lead, with 17k playouts.

Click Here To Show Diagram Code

[go]$$W KataGo's evaluation of Sanno's suggested "best for both"
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . O . . . . O . |
$$ | . . 1 . . . . . . . X . . . O O O X . |
$$ | . . . , . 2 . . . , . X . X X O X X . |
$$ | . . 3 . . . . . . . . . . . O X X . . |
$$ | . . . . . . . . . . . . . . O O . . . |
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |[/go]

KataGo evaluates this result as B+7.3 and next has Black go to the open corner in the lower right. It would ignore to go there already and would ignore for the same reason.

MY INTERPRETATION

From my analyses with KataGo of 6 castle games, my impression is that the professional commentators often make comments about direction of play which I can't confirm with KataGo. Of course opening theory has evolved a lot since Shusaku, first by Go Seigen and Kitani Minoru, bringing the 4-4 and espececially 3-3 into fashion, later by the Korean and Chinese developments, moving the 3-3 out of fashion and recently with KataGo, confirming 3-3 as slightly inferior in general but bringing 3-4 back into fashion, plus all sorts of novelties.

KataGo clearly thinks of the cut up groups in the upper right as urgent, given its evaluating moves in that area on par with playing in the open corners.

Sanno calls Black stones "on the right" in relationship to the upper left corner as "thickness". I'm not sure if he means that Black is thick in the whole upper right area, given White's 3 floating stones, or specifically the black stones at the top. Since any white move in that area elicits a black response on both sides, I wouldn't call those stones thick. Surely they exert influence. Influence usually needs to be backed up in order to become thick or efficient. If not, stones merely exerting influence can become a target.

As expected, KataGo thinks of the 3-3 point as a move to ignore. It occupies the corner and turns the area into one that is not urgent.
So what's the difference then with 4-4? Black can ignore that too, "says KataGo", but next White's pressure on the top increases.
The same is true for the 3-5 move but again Black can ignore and later invade the corner.

All in all, I would dare saying that Sanno's comments here are very much the line of thought of those days but not necessarily true, and not confirmed by KataGo. It's not that these comments should be completely disregarded for that reason. I just find it hard to learn from pro comments without backup from AI, so I tend to treat them as incidental.

I'm not sure this needs to be about katago evaluations and variations.

I learned long time ago that this 3-4 is often the best move in the corner when there are strong stones around the marked point. I learned it by seeing others play this way and at some point I did some pattern searches in professional games and very often they played this 3-4 in similar situations.

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[go]$$W
$$ +--------------------------------------+
$$ | . . . . . . . . . . . . . . . . . . .|
$$ | . . . . . . . . . . . . O . . . . O .|
$$ | . . . 1 . . . . . . # . . . O O O X .|
$$ | . . . , . . . . . , . X . X X O X X .|
$$ | . . . . . . . . . . . . . . O X X . .|
$$ | . . . . . . . . . . . . . . O O . . .|
$$ | . . . . . . . . . . . . . . . . X . .|
$$ | . . . . . . . . . . . . . . . . . . .|
$$ | . . . . . . . . . . . . . . . . . . .|
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$$ | . . . , . . . . . , . . . . . , . . .|
$$ | . . . . . . . . . . . . . . . . . . .|
$$ | . . . . . . . . . . . . . . . . . . .|
$$ | . . . . . . . . . . . . . . . . . . .|
$$ +--------------------------------------+[/go]

If you tried some variations that feel like they could happen, then it really always turns out just fine. Indeed, when I checked with the computer the 3-4 move is tighter on territory than katago's preferred move.

Examples of some (subjectively) likely variations:


The 4-5 point is a lot less tight on territory and it is almost obvious that it wouldn't be favored by katago. I think it was about -1.4 compared to the 3-4 point and bit closer to the katago move. That is when running a lot of playouts, it starts out as being much closer. However, I wouldn't say I was as confident coming up with variations in this case. Maybe it is harder in general or it is something only myself finds more difficult.

The reason why the move is in the corner is like that human players often hedge their bets when they choose their move. The computer appears to want to start any semi-forced sequence if it evaluates better than the alternatives. This should be perceived as a risky strategy by someone that recognizes that they could inadvertently start something that then ends up being unfavorable. Therefore, I'd venture to guess that white is hedging his bets by playing in the corner and expects black will have a similar approach and either play into the corner or play in another corner.

If white plays in the corner, then it sure would be a move that the player fancies and that doesn't have to be anyone else's move. I wouldn't really expect the comment by Sanno to be as informative as the fact that Yasui Sanchi played this move in an important game. Sanno could come later to say something that was entertaining or sounded smart, which is likely what any audience wants to hear, but Yasui Sanchi was the one playing the game