BillSpightsElfPositionalJudgmentExercises/Game 9 ELF's Solution

Takagawa (W) - Rin Kaiho, Meijin Final, Game 3, 1969-09-09a. Komi = 5+ pts. (I.e., 5 pts. with White winning jigo.)

After W44 Elf gives Black an estimated winrate of 90½% with 33.8k playouts. However, White, Takagawa, won by 8 pts.

[Diagram]
Black is ahead.  

Elf's recommended continuation of the game.

[Diagram]
Elf's mainline continuation  

B45 leans on the White group on the right side; then B47 tops the tree, capping the White center stones. As White runs out, Black's attack promises to erase White's potential in the left center.

Earlier in the game:

[Diagram]
"Obvious" block loses 10%, says Elf  

Which side to block the 3-3 invasion from is a question I cannot always answer. Usually the difference is small, but in this case it is 10%, and Elf recommends the opposite alternative to the one that appears to be the correct direction of play. (Takagawa would know. ;)) How come?

[Diagram]
Elf's variation for W16  

Here is a clue. Instead of the traditional joseki (now obsolete) taking outside strength, White plays the two step hane and takes the corner.

[Diagram]
Elf's variation for W16 continued  

White does not make outside strength to work with the white+circle stones. Instead, Black has a weakish group in hostile territory. W28 secures territory while attacking the Black group. Black makes elbow room with sente and then turn to his territorial framework in the top right quadrant.

[Diagram]
Elf recommended line after W16  

Takagawa played W20 at 21, but Elf says to play the two step hane here, as well. (The difference only comes to 1%, however.)

[Diagram]
Elf recommended line after W16 continued  

In this variation the white+circle stone is weak. W30 reduces the Black framework in the top right, while Black attacks the white+circle stone. On balance, this is better for Black than when he makes a weak group on the left side.

[Diagram]
White loses more ground  

In the actual game Black played the hane-and-connect in the bottom left corner, which was joseki before the AI era. In this case that is Elf's choice, too, probably because White ends up overconcentrated, given the white+circle stones.

B27 reduces the left side. But W30 loses 16½% and then W34 loses 11%. Each side made smaller errors, but White made three significant mistakes that gave Black a commanding lead.

[Diagram]
Elf mainline for W30  

W30 and W32 make territory with the White wall. Black enlarges the Black moyo and then W34 and W36 reduce it. B37 blocks on the third line with eye shape. Then W38 secures the corner and threatens to connect underneath.

[Diagram]
Elf's mainline for W34  

Takagawa's underneath connection surprised me. It seemed too territorial. I expected something like Elf's W36 in this diagram. B37 is on the frontier of moyos.

[Diagram]
Elf's mainline for W34 continued  

B45 threatens to cut the four White stones off, but White turns and then boldly jumps into Black's moyo. OC, Black still has around an 80% advantage. ;)


BillSpightsElfPositionalJudgmentExercises/Game 9 ELF's Solution last edited by xela on December 7, 2019 - 04:49
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