Miyashita Shuyo, 7 dan played White agains Takagawa Kaku, 7 dan, in a preliminary round of the Honinbo tournament on August 23, 1950 (GoGoD 1950-08-23a). Komi was 4½ pts. After Elf, assuming area scoring and 7½ pt. komi, estimates Black's winrate at 90% (28.4k playouts). Takagawa won by resignation after Black 275.
Takagawa won the Honinbo title in 1952 and held it for nine straight years. He was known for his mastery of the opening and for his positional judgement.
Elf shows this variation with 1% worse winrate estimate than its play, and with fewer playouts (3.1k vs. 14.3k). Elf ends this variation here. OC, the difference could be noise. :)
White pushes into the center, enclosing the stones for a furikawari. After Black's lead looks apparent.
The actual game continuation is of some interest, I believe.
Takagawa did not fancy the sacrifice and played . Elf regards this as losing 2%. Then he cut at 37. Elf regards this as losing 3%. Both plays are within Elf's margin of error, but they do add up. But then Miyashita returns the favor with , losing 5½%.
Elf recommends the atari at , followed by the hanging connection. The result is a furikawari similar to Elf's mainline, but with White 5% better off.
This variation emphasises the flexibility of today's top bots. After , marked, Elf switches gears and, instead of saving the stones, sacrifices them with sente. Then Black invades the top side. (In other variations Elf plays at a.)
is a probe. is the blunder. Black tries to save everything in a complicated fight in which he is outnumbered and has too many weaknesses. Elf says that loses 25%. :shock: Then loses 10% more. Elf thinks it should be at 48, taking away a White dame. A few moves after this diagram Black jumps out at a and then White gets to play the hane at b. Things went from bad to worse for Takagawa, and by it is White who has a winrate estimate of 90%.
Backing up, Takagawa could have avoided the complications.
Elf recommends the underneath hane for instead of the cut. Then Black does not have a second weak group to worry about. In fact, can attack White's weakness. :D
Now a look at the earlier play. :)
The splitting play on the side is one of the hoariest stratagems in go, going back to the earliest extant game records. In this case Miyashita probably played it to avoid sanrensei by Black. Before the AI revolution both the sanrensei and the splittinng play had begun to be questioned. In his 21st century go writings, Go Seigen downplayed the splitting play, but was plainly ambivalent. There is even one position on which he took opposite opinions on it on two different occasions. Nowadays, the bots generally disapprove of the splitting play.
BTW, is on R-09 instead of R-10 to give less space for Black to approach while extending his bottom side moyo,
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OC, at the time this 3-3 invasion was almost anathema. The hane-and-connect on the second line was considered joseki until the AI era. But even now it is hard for me to shake the feeling that Black does not gain by this sequence (taking into account White's extra play, OC). Surely, it seems, Black's fourth line stones in the wall are worth more than 2 pts. of territory each, especially with the Black position on the bottom side.
Elf's second choice is the top left enclosure. Note that Black does not play sanrensei, but makes the "enclosure" of the bottom right corner, extending the Black moyo only a little.
Then White invades the top right corner. Note that Black blocks on the top side. the opposite of what we might expect from human ideas about the direction of play. {shrug}
ELf regards Takagawa's (next diagram) as losing 9%. Instead Black approaches the top left corner. The kick joseki there is a favorite of Elf's. Note that Black approaches from the bottom, anyway. As for it has only 1.5k playouts, but I suspect that it would be Elf's choice in that corner, anyway, because it prevents Black from playing the block there in response to the 3-3 invasion.
You can see how would have been considered ideal at the time. It was a long extension from the top right 4-4 stone and it invited , which Black kicked with , resulting in a position for White was and still is, considered a bit overcentrated. Then is an ideal development of the Black bottom side. Nonetheless, Elf prefers the previous diagram for Black by 10%.
When I was learning go the textbooks decried without an enclosure of the top left corner. Elf does, too. regarding it as losing 11½%. However, it and other such extensiions without an enclosure have a long history in top level play. Perhaps Miyashita wanted to prevent a kind of double wing formation by Black from the top right 4-4 stone if he enclosed the top left.
Elf, of course, would enclose the top left corner. Then Black would not extend far on the top side, but simply enclose the top right corner. Then White would play the shoulder blow to reduce the Black moyo on the bottom side.
Below in progress. :)
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Black takes kikashi against White on the left side and secures his group in the top left with sente. White ignores and invades the right side.
In the actual game, up to White made three sizable errors: the splitting play on the right side, the extension on the top side, and the wrong plan on the left side.