How is your positional judgement? Game 17

Bill Spight · Post by **Bill Spight** » Sun Oct 27, 2019 7:36 am

These topics are based upon Elf's commentaries on GoGoD games. As always, assume area scoring with 7½ pts. komi.

After

Elf estimates one player's winrate as 90½% with 56.6k playouts. Which player is it?

Click Here To Show Diagram Code: [go]$$Bcm37 White to play $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . X . X X . | $$ | . . . O . . . . . , . . . . . O X . X | $$ | . . . . . . . . . . . . . . . O O X . | $$ | . . . . . . . . . . . . . . . . X O . | $$ | . . . . . . . . . . . . . . . . O . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . . , . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . O O . . | $$ | . . . O O O . . . . . . . . . O X . . | $$ | . . X O X O . . . , . . . . . , X . . | $$ | . X O X X X O . . . . . . X . X . . . | $$ | . X O . . . X . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

Enjoy!

bayu · Post by **bayu** » Sun Oct 27, 2019 8:50 am

3 corners, neither of which is sealed in. And black gets a free ladder breaker. I take black anytime. But because Bill posted this as something interesting, I bet that white is ahead. No clue why though.

Click Here To Show Diagram Code: [go]$$Wcm38 White to play $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . 3 . . . . . . . . X . X X . | $$ | . . . O . . . . . , . . . . . O X . X | $$ | . . . . . . . . . . . . . . . O O X . | $$ | . . . . . . . . . . . . . . . . X O . | $$ | . . . . . . . . . . . . . . . . O . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . . , . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . O O . . | $$ | . . 1 O O O . . . . . . . . . O X . . | $$ | . 2 X O X O . . . , . . . . . , X . . | $$ | . X O X X X O . . . . . . X . X . . . | $$ | . X O . . . X . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

My instinct is to continue like this to provoke black to start a weak group. It's probably a sure fire method to lose the 90% advantage:)

TelegraphGo · Post by **TelegraphGo** » Sun Oct 27, 2019 9:05 am

Could this be it? The first one I get right on record? Probably not, since I don't even know the joseki they played

I have a faint recognition of the bottom left and top right results, but not enough to be able to reproduce how they came onto the board. I'll start by looking at the top right.
It's pretty clear that W had one stone captured here - the R17 stone only ever gets played when B is afraid of capturing immediately and allowing W a ko by playing R17 themselves like in the position below:

Click Here To Show Diagram Code: [go]$$Wcm37 B doesn't want to capture $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . X . B X . | $$ | . . . O . . . . . , . . . . . O X O . | $$ | . . . . . . . . . . . . . . . O O X . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . . , . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . O O . . | $$ | . . . O O O . . . . . . . . . O X . . | $$ | . . X O X O . . . , . . . . . , X . . | $$ | . X O X X X O . . . . . . X . X . . . | $$ | . X O . . . X . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

So that means it's a 7 black stones v. 6 white stones commitment. Since B has committed one more stone, we can compare to a similar result where black has committed one more stone than white.

Click Here To Show Diagram Code: [go]$$Bcm37 A simpler result $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . X . . . . . | $$ | . . . O . . . . . , . . . . . X . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . O . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . . , . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . O O . . | $$ | . . . O O O . . . . . . . . . O X . . | $$ | . . X O X O . . . , . . . . . , X . . | $$ | . X O X X X O . . . . . . X . X . . . | $$ | . X O . . . X . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

Compared to this result, in game black has the corner much more solidly, but with a lower position. White in game has a significantly stronger position, but with ladder aji. If the ladder is easy for white to handle, then the game position is much better for white than the simple one above - white is just way harder to attack severely.
So let's look at the bottom left corner to see how the ladder aji is. It's white's turn right now, and W is about to sacrifice the two stone for influence. The first move that comes to my mind is:

Click Here To Show Diagram Code: [go]$$Bcm37 Double hane when B is liberty short $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . X . X X . | $$ | . . . O . . . . . , . . . . . O X . X | $$ | . . . . . . . . . . . . . . . O O X . | $$ | . . . . . . . . . . . . . . . . X O . | $$ | . . . . . . . . . . . . . . . . O . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . . , . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . O O . . | $$ | . . . O O O . . . . . . . . . O X . . | $$ | . . B O X O . . . , . . . . . , X . . | $$ | . X O X X X O . . . . . . X . X . . . | $$ | . X O . . . X W . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

But to all those who've seen this sort of sequence before it's obvious that W is supposed to take advantage of B's one stone before doing this. The question is whether W should employ a driving tesuji by Atari underneath to prevent the open skirt, or simply Atari from the top to prevent the cutting point. Since W has no help nor development on the left side yet, I would prefer leaving an open skirt to a cutting point, so my suggested variation is:

Click Here To Show Diagram Code: [go]$$Wcm37 White to play $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . X . X X . | $$ | . . . O . . . . . , . . . . . O X . X | $$ | . . . . . . . . . . . . . . . O O X . | $$ | . . . . . . . . . . . . . . . . X O . | $$ | . . . . . . . . . . . . . . . . O . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . . , . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . O O . . | $$ | . . 1 O O O . . . . . . . . . O X . . | $$ | . 2 X O X O . . . , . . . . . , X . . | $$ | . X O X X X O 5 . . . . . X . X . . . | $$ | . X O . . 4 X 3 . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

This bottom left position looks absurdly good for W. B is surrounded with only a handful of points (and bad endgame aji on top of that). On top of that, this is the ideal kind position to have on the opposite side of the board of a ladder. If B tries to play a ladder breaker, it will be inefficient, because it will be too close to thickness. All of W's stones work beautifully together - W's bottom right stones aren't really attackable due to W's big lead in influence, so the game looks hideously difficult for B. I've been confident with all the other ones, but this time really - if AI favors black here then I'm gonna start 2-2 invading san-san openings for territory.

jlt · Post by **jlt** » Sun Oct 27, 2019 9:13 am

White has no territory, and Black has three corners and no weak groups. On the other hand, Black has no influence: no stones on the fourth line or higher, and White can get a wall on the lower left and lock Black in.

Maybe I prefer White because I don't like being excessively territorial, but it's hard to choose.

Click Here To Show Diagram Code: [go]$$Wcm38 (move 48 at :wc:) $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . X . X X . | $$ | . . . O . . . . . , . . . . . O X . X | $$ | . . . . . . . . . . . . . . . O O X . | $$ | . . . . . . . . . . . . . . . . X O . | $$ | . . . . . . . . . . . . . . . . O . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . . , . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . 5 3 . . . . . . . . . . . . O O . . | $$ | . 4 2 O O O . . . . . . . . . O X . . | $$ | 6 1 X O X O 9 . . , . . . . . , X . . | $$ | . X O X X X O 8 W . . . . X . X . . . | $$ | . X O . . 0 X 7 . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

Bill Spight · Post by **Bill Spight** » Sun Oct 27, 2019 10:06 am

Just a note about how I choose the games to show. First, OC, is that I look for games with Elf winrates around 90% or higher around move 30. These may be a bit too easy for those who reply, but they are not always so easy. And that's a good place in the game to evaluate the position. Second, I look for games by Takagawa, Go Seigen, Lee Changho, and Fujisawa Hideyuki because they are human masters of the fuseki. Also, Takemiya, because who understands Cosmic Go? (Nobody, according to Elf.

) Also, Cho Chikun, because if we still had a Meijin, wouldn't he be it?

I have rejected a few games because some of Elf's variations were too far above my head. OC, I do not pretend to understand all of this, but I do want to say something sensible.

Kirby · Post by **Kirby** » Sun Oct 27, 2019 10:37 am

Tryss · Post by **Tryss** » Sun Oct 27, 2019 10:58 am

What was the komi of the original game?

Bill Spight · Post by **Bill Spight** » Sun Oct 27, 2019 11:51 am

Tryss wrote:What was the komi of the original game?

Katago with 0 komi think the game is even (52.5% wr for black with 40k playouts)

5½ komi.

I am avoiding 0 komi games, and even 4½ komi games, because the question of whether the players have made mistakes or not in a 0 komi game is too difficult. In no komi game Elf usually says that White gives up many percentage points in the opening.

xela · Post by **xela** » Sun Oct 27, 2019 2:16 pm

Echoing bayu (post #2 above):

And that leads us to an interesting question: evaluation assuming both players are strong, versus evaluation assuming both players are amateurs?

jlt · Post by **jlt** » Mon Oct 28, 2019 12:32 am

@xela: I looked at positional judgements by early versions of LeelaZero, and by Leela 0.11.

Knotwilg · Post by **Knotwilg** » Mon Oct 28, 2019 4:14 am

no-LZ analysis

Click Here To Show Diagram Code: [go]$$W $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . X b # X . | $$ | . . . O . . . . . , . . . . . O X . X | $$ | . . . . . . . . . . . . . . . O O X . | $$ | . . . . . . . . . . . . . . . . X O . | $$ | . . . . . . . . . . . . . . . . O . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . . , . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . 5 3 . . . . . . . . . . . . O O . . | $$ | . 4 2 O O O . . . . . . . . . O X . . | $$ | 6 1 X O X O . a . , . . . . . , X . . | $$ | . X O X X X O . . . . . . B . X . . . | $$ | . X O . 8 7 X 9 . . . . . . . . . . . | $$ | . . . . . 0 . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

Although White can enclose Black in the lower left corner like this, it's a 15 point corner and half of her influence (after tiger mouthing at A) is facing a low Black stone. Black doesn't seem to have any inefficiencies, except for being low in the upper right as well. White's ladder represents some aji too.

Overall, this seems to be a case where Black has safe territory in three places, while White's influence is far apart. Black has plenty of room to maneuver in that grand sphere of influence and nearly every group of White can potentially be turned into a liability. So I choose Black.

Edit: dwyrin's heuristic favors White. And there IS an inefficiency in Black's position: the marked stone in the upper right should be at B.
So I'm less confident now of my choice.

LZ

Bill Spight · Post by **Bill Spight** » Sun Nov 10, 2019 8:32 am

My discussion of Elf's commentary.

Honinbo final, game 2, 1995-05-24a. Kato Masao (W) vs. Cho Chikun

After

Elf estimates White's winrate as 90½% with 56.6k playouts.

White won by resignation.

Click Here To Show Diagram Code: [go]$$Bcm37 White is ahead $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . X . X X . | $$ | . . . O . . . . . , . . . . . O X . X | $$ | . . . . . . . . . . . . . . . O O X . | $$ | . . . . . . . . . . . . . . . . X O . | $$ | . . . . . . . . . . . . . . . . O . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . . , . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . O O . . | $$ | . . . O O O . . . . . . . . . O X . . | $$ | . . X O X O . . . , . . . . . , X . . | $$ | . X O X X X O . . . . . . X . X . . . | $$ | . X O . . . X . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

Elf's mainline continuation

Click Here To Show Diagram Code: [go]$$Wcm38 Elf's mainline $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . 8 0 . . . . . . . . . . X . X X . | $$ | . . 9 O . . . . . , . . . . . O X . X | $$ | . . . . . . . . . . . . . . . O O X . | $$ | . . . . . . . . . . . . . . . . X O . | $$ | . . . . . . . . . . . . . . . . O . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . . , . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . O O . . | $$ | . . . O O O . . . . . . . . . O X . . | $$ | . . X O X O . 5 . , . . . . 3 , X . . | $$ | . X O X X X O 7 6 . . . . X 4 X . . . | $$ | . X O . . . X 1 . . . . . . . . . . . | $$ | . . . . . 2 . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

Kato played the two step hane. The rest is Elf's variation.

plays a hanging connection to secure the Black group. Then

takes kikashi against the bottom right corner, then

makes a trumpet connection. Black takes kikashi against that and then invades the top left corner.

Click Here To Show Diagram Code: [go]$$Wcm48 Elf's mainline, continued $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . 4 . . . . . . . . . . . . . | $$ | . 8 X X 2 1 6 . . . . . . . X . X X . | $$ | . . O O 3 7 . . . , . . . . . O X . X | $$ | . . . . . . . . . . . . . . . O O X . | $$ | . . . . . . . . . . . . . . . 5 B O . | $$ | . . . . . . . . . . . . . . . . O . . | $$ | . . . 9 . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . . , . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . O O . . | $$ | . . . O O O . . . . . . . . . O X . . | $$ | . . X O X O . O . , . . . . O , X . . | $$ | . X O X X X O O X . . . . X X X . . . | $$ | . X O . . . X O . . . . . . . . . . . | $$ | . . . . . X . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

eliminates the aji of the

stone.

prevents the extension on the top side with sente, then

secures the corner and creates an open skirt for White.

makes a three space high extension from White's wall. No point in a low extension because of the open skirt.

Black has taken all four corners, but Elf judges White's outside strength to be commanding.

Earlier in the game.

Click Here To Show Diagram Code: [go]$$B Probe $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . 5 . . . . | $$ | . . . 2 . . . . . , . . . . . , 1 0 . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . . c . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . a 8 . . | $$ | . . . . . . . . . . . . . . . 6 7 . . | $$ | . . . 4 . . . . . , . . . . . , 9 . . | $$ | . . . . . . . . . . . . . b . 3 . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

Through

was a popular fuseki, with the probe,

, regarded as an improvement. However, Elf thinks that

is a minor error, losing 7% to par. Elf prefers Wa - Bb, Wc. The bots do like the solid connection at a.

Click Here To Show Diagram Code: [go]$$Bcm11 Three in a row $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . X . 7 5 . | $$ | . . . O . . . . . , . . . . . 6 X O 9 | $$ | . . . . . . . . . . . . . . . 4 2 1 . | $$ | . . . . . . . . . . . . . . . . 3 8 . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . . , . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . O . . | $$ | . . . . . . . . . . . . . . . O X . . | $$ | . . . O . . . . . , . . . . . , X . . | $$ | . . . . . . . . . . . . . . . X . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

Elf thinks Black made three mistakes in a row.

lost 7% to par,

lost 11½%, and

lost 15½%. All that to capture one stone! After

Elf gives Black a 20% chance to win the game (60.1k playouts).

Click Here To Show Diagram Code: [go]$$Bcm13 Elf's variation for :b13: $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . 5 . . | $$ | . . . . . . . . . . . . . . X 4 3 . . | $$ | . . . O . . . . . , . . . . . 2 X O . | $$ | . . . . . . . . . . . . . . . . O X . | $$ | . . . . . . . . . . . . . . . . . 1 . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . . 0 . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . 8 . . . . . . . . . . . . 6 O . . | $$ | . . . . . . . . . . . . . . . O X . . | $$ | . . . O . . . . . , . . . . . , X . . | $$ | . . . . . 7 . . . . . . . 9 . X . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

extends on the second line, avoiding White's kikashi there.

and

play kikashi against the corner, then

returns to the bottom right corner with the solid connection.

Click Here To Show Diagram Code: [go]$$Bcm15 Elf's mainline variation for :b15: $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . 6 5 . . | $$ | . . . . . . . . . . . 7 . . X 4 3 . . | $$ | . . . O . . . . . , . . . . . 2 X O . | $$ | . . . . . . . . . . . . . . . O O X . | $$ | . . . . . . . . . . . . . . . 8 X 1 . | $$ | . . . . . . . . . . . . . . 0 9 . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . . , . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . O . . | $$ | . . . . . . . . . . . . . . . O X . . | $$ | . . . O . . . . . , . . . . . , X . . | $$ | . . . . . . . . . . . . . . . X . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

makes the solid connection, again preventing the White atari there.

-

penetrate the Black corner.

makes a kind of two space extension, and the White wall is still insecure.

pushes along the fourth line,

blocks, and then

hanes.

Click Here To Show Diagram Code: [go]$$Bcm25 Elf's mainline variation for :b15:, continued $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . O X . . | $$ | . . . . . . . . . . . X . . X O X . . | $$ | . . . O . . . . . , . . . . . O X O . | $$ | . . . . . . . . . . . . . . . O O X . | $$ | . . . . . . . . . . . . . . . O X X . | $$ | . . . . . . . . . . . . 4 . O X . . . | $$ | . . . . . . . . . . . . . . 2 1 . a . | $$ | . . . . . . . . . . . . . 5 3 6 . . . | $$ | . . . , . . . . . , . . . . . 8 . 0 . | $$ | . . . . . . . . . . . . . . 9 7 b . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . O . . | $$ | . . . . . . . . . . . . . . . O X . . | $$ | . . . O . . . . . , . . . . . , X . . | $$ | . . . . . . . . . . . . . . . X . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

at a,

at b

extends on the fourth line,

pushes, and

block again.

protects against the cut, and

stands.

cuts, and the fight is on.

Click Here To Show Diagram Code: [go]$$Bcm17 Elf's mainline variation for :b17: $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . 8 . . . B 2 . X . | $$ | . . . O . . . . . , . . . . . O X W 1 | $$ | . . . . . . . . . . . 0 . . . O O X . | $$ | . . . . . . . . . . . . . . . 4 X a . | $$ | . . . . . . . . . . . . . . . 6 5 . . | $$ | . . . . . . . . . . . . . . . . 7 . . | $$ | . . . . . . . . . . . . . . 9 . . . . | $$ | . . . , . . . . . , . . . . . , . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . 3 O . . | $$ | . . . . . . . . . . . . . . . O X . . | $$ | . . . O . . . . . , . . . . . , X . . | $$ | . . . . . . . . . . . . . . . X . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

captures the

stone, also preventing the atari at a. After the probe and crosscut, preventing the White atari at a becomes a prime objective for Black. The Black shape with five stones surrounding the eye formed by capturing the single White stone appears in textbooks as a good way for White to sacrifice that stone. Elf really doesn't seem to like that shape.

penetrates the corner, cutting off the

stone.

gets the cut in the bottom right. That is a rare treat, as the bots love the solid connection so much.

and

push along the fourth line, building a wall, then

extends on the top side.

takes the double keima, and then

protects White's incipient territorial moyo.

Back to the game.

Click Here To Show Diagram Code: [go]$$Wcm20 Big moves $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . X . X X . | $$ | . . . O . . . . . , . . . . . O X . X | $$ | . . . . . . . . . . . . . . . O O X . | $$ | . . . . . . . . . . . . . . . . B O . | $$ | . . . . . . . . . . . . . . . . 3 . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . . , . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . 1 O . . | $$ | . . . . . . . . . . . . . . . O X . . | $$ | . . . O . . . . . , . . . . . , X . . | $$ | . . . . . . . . . . . . . 2 . X . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

The solid connection,

, is big. So is

capturing the

stone in a ladder.

, although joseki, is a mistake, according to Elf, losing 10% to par. Black should save the

stone.

Click Here To Show Diagram Code: [go]$$Bcm21 Saving Private :bc: $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . X . X X . | $$ | . . . O . . . . . , . . . . . W X . X | $$ | . . . . . . . . . . . . . . . W W X . | $$ | . . . . . . . . . . . . . . . 1 B O . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . . , . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . O O . . | $$ | . . . . . . . . . . . . 8 . . O X . . | $$ | . . . O . . . . . , . . . . 5 7 X . . | $$ | . . . . . . . . . . . . . 6 2 X . . . | $$ | . . . . . . . . . . . . . 4 3 . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

Elf recommends

, not only saving the

stone but threatening the

stones as well.

-

play the tenuki joseki in the bottom right.

Back to the game.

After

Elf gives Black a 10½% chance of winning (24.3k playouts). White makes a few minor errors in the bottom left corner, but maintains the 90% lead after Black blunders.

Click Here To Show Diagram Code: [go]$$Bcm23 Ladder breaker $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . X . X X . | $$ | . . . O . . . . . , . . . . . O X . X | $$ | . . . . . . . . . . . . . . . O O X . | $$ | . . . . . . . . . . . . . . . . X O . | $$ | . . . . . . . . . . . . . . . . O . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . . , . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . O O . . | $$ | . . . 8 2 6 . . . . . . . . . O X . . | $$ | . . 7 O 1 . . . . , . . . . . , X . . | $$ | . 9 4 3 5 . . . . . . . . X . X . . . | $$ | . . 0 . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

is a ladder breaker.

parries it, but Elf thinks that 27 is 7½% better.

extends on the fifth line, offering the corner for outside strength. Elf regards the solid connection at 29 to be 5% better.

Click Here To Show Diagram Code: [go]$$Bcm33 Blunders $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . X . X X . | $$ | . . . O . . . . . , . . . . . O X . X | $$ | . . . . . . . . . . . . . . . O O X . | $$ | . . . . . . . . . . . . . . . . X O . | $$ | . . . 0 . . . . . . . . . . . . O . . | $$ | . . . . . . . . . . . . . . a . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . . , . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . O O . . | $$ | . . . O O O . . . . . . . . . O X . . | $$ | . . X O X 2 8 . . , . . . . . , X . . | $$ | . X O X X 3 4 7 b . . . . X . X . . . | $$ | . 1 O . . 9 5 6 . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

Elf regards

as a minor error, losing 7% to the a. But

is a blunder, giving up 18% to par. Even though Black can threaten to break out with sente,
what he gains in the corner is not worth the outside strength that White gets in exchange, according to Elf. Elf says that

should take gote and make the ladder with b. The two space extension in the actual game loses 13% to par, a blunder when White's winrate is aroundd 90%.

Elf's judgement of the play in the top right corner is particularly instructive, as White's sacrifice comes right out of the textbooks.

dhu163 · Post by **dhu163** » Mon Dec 26, 2022 10:53 am

seems easy

All is joseki except for upper right and lower left both of which are better for W. Next move is double hane on lower side.

On lower left, W has F5 misplaced and overconcentrated, but can make up for it with the tight local shape of the double hane.

On the right, W's outside is put to good use saving a move not needing to extend with R6 and instead directly developing.

On the lower left, W has several different aji, probably B6 is best if you have to play something, but W can tenuki and also has several ko threats.

Upper right: B has one extra stone. Just around 10 pts with some 3rd line potential that is limited by a cutting point. The shape is way too confined to a small area. W has some points with the ladder as B has no good ladder breaker. Locally perhaps 2pts with 6 or 7 lines of potential with another move. That is simply more than B.

Lower left: This was W's first corner and W needs to add another sente move to continue. B has 13 pts. W has a wall of height 13 if W adds another move, with one weakness on the left. This is normally estimated at around 26 pts, which seems reasonable. But W is also supporting the life of the Q6 stones.

Basically B expects a centre move as in return for a ladder breaker. If we count the right side as cancelling B's lower right, then W at the moment has 13 more in the lower left and the upper left corner which should be counted as 13 normally also. komi should compensate for B's initiative. Upon discounting the ladder breaker, it seems as though W is leading by around 15 pts. I find that a bit hard to believe. Probably I haven't sufficiently counted the W's weaknesses (perhaps there are 1.5 cutting points, subtracting 3pts?) and the fact that all B's groups are alive. Also W probably has less in the lower left than this estimate because B has potential on both sides. This still doesn't seem consistent to me. If the lead really were that much the winrate should be 99%.

Perhaps B hane on the lower side isn't optimal. It is sometimes better to pull back for better aji on the left as the lower side isn't valuable and even after adding a move, problems remain even on the lower side.

Life In 19x19

How is your positional judgement? Game 17

How is your positional judgement? Game 17

Re: How is your positional judgement? Game 17

Re: How is your positional judgement? Game 17

Re: How is your positional judgement? Game 17

Re: How is your positional judgement? Game 17

Re: How is your positional judgement? Game 17

Re: How is your positional judgement? Game 17

Re: How is your positional judgement? Game 17

Re: How is your positional judgement? Game 17

Re: How is your positional judgement? Game 17

Re: How is your positional judgement? Game 17

Re: How is your positional judgement? Game 17

Re: How is your positional judgement? Game 17