There was an interesting question of technique in Lee Sedol (white) vs Wang Zejin. First the context: Black had just haned at 1 and instead of defending solidly at 3 (which LZ and other AI preferred by ~1%) Lee played a shoulder hit, Wang got the atari (profit in sente I suppose which is why bots don't like, though telling the difference between a good reverse sente to avoid that and a slow move is hard!) and then answered shoulder, and Lee cut. 8 was the correct shape, 9 a similarly minor (1%) mistake and then black tried to enclose with clamp.
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[go]$$Bc
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$$ | . . X X O O O . . . . . . . . . . . . |
$$ | . . X O . X X O O O O 4 . O . . . . . |
$$ | . . X O . . . X X X X O 3 . . X . . . |
$$ | . . . O . . . . . . . 1 6 0 8 . . . . |
$$ | . . X . . . . . . . . 7 9 . . . X . . |
$$ | . . . . . . . . . . . . . . B 2 5 . . |
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$$ | . . . . . . . . . . . . . . . . X X . |
$$ | . . O . . . . . . . . . . X . O X O . |
$$ | . . . . . . . . . . . . . . . X O X . |
$$ | . . . O . X . . . , . . . . . X O X . |
$$ | . . . . O X . . . . O . . O . X O X . |
$$ | . . . . . . . . . . . . . . . O O O . |
$$ | . . . . . . . . . . . . . . . . O . . |
$$ ---------------------------------------[/go]
LZ's instinct was to break out with this sacrifice, but it soon saw that black can resist with 2 at 3 and although the aji is bad black's ok.
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[go]$$Wc
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$$ | . . X X O O O . . . . . . . . . . . . |
$$ | . . X O . X X O O O O O . O . . . . . |
$$ | . . X O . . . X X X X O X . . X . . . |
$$ | . . . O . . . . . . . X O O O . . . . |
$$ | . . X . . . . . . . . X X 5 . 4 X . . |
$$ | . . . . . . . . . . . . . 3 X O X . . |
$$ | . . . . . . . . . . . . . . 1 2 . . . |
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$$ | . . . . . . . . . . . . . . . . X X . |
$$ | . . O . . . . . . . . . . X . O X O . |
$$ | . . . . . . . . . . . . . . . X O X . |
$$ | . . . O . X . . . , . . . . . X O X . |
$$ | . . . . O X . . . . O . . O . X O X . |
$$ | . . . . . . . . . . . . . . . O O O . |
$$ | . . . . . . . . . . . . . . . . O . . |
$$ ---------------------------------------[/go]
Lee presumably didn't like that either so created some cutting points with a kinda crude push. Rather than blocking black pulled back, -4% says LZ
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[go]$$Wc
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$$ | . . X X O O O . . . . . . . . . . . . |
$$ | . . X O . X X O O O O O . O . . . . . |
$$ | . . X O . . . X X X X O X . . X 2 . . |
$$ | . . . O . . . . . . . X O O O 1 . . . |
$$ | . . X . . . . . . . . X X . . . X . . |
$$ | . . . . . . . . . . . . . . X O X . . |
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$$ | . . . . . . . . . . . . . . . . X X . |
$$ | . . O . . . . . . . . . . X . O X O . |
$$ | . . . . . . . . . . . . . . . X O X . |
$$ | . . . O . X . . . , . . . . . X O X . |
$$ | . . . . O X . . . . O . . O . X O X . |
$$ | . . . . . . . . . . . . . . . O O O . |
$$ | . . . . . . . . . . . . . . . . O . . |
$$ ---------------------------------------[/go]
I guess Wang didn't like giving up the corner profit with the cut, LZ says the below is quite ok for him as he gets strong in the centre. However, white can improve on this sequence by not exchanging 5 for 6 but cutting directly, and then ignoring the s17 push to reduce around n8, having created the option to take the corner profit with a big gote move later and retaining more aji around the q12 cut to make n8 reduction have more oomph. Also LZ then decides black 4 could be at 5 and allow white to link through again and go back to take the corner profit now that white made the bad 1-2 exchange. A delicate dance of turning each others moves into bad exchanges.
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[go]$$Wc
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$$ | . . X X O O O . . . . . . . . . a . . |
$$ | . . X O . X X O O O O O . O . . 9 0 . |
$$ | . . X O . . . X X X X O X . . X 7 8 . |
$$ | . . . O . . . . . . . X O O O 1 2 . . |
$$ | . . X . . . . . . . . X X . . 5 X . . |
$$ | . . . . . . . . . . . . . 4 X O X . . |
$$ | . . . . . . . . . . . . . . 3 6 . . . |
$$ | . . . . . . . . . . . . . . . b . . . |
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$$ | . . . . . . . . . . . . . . . . X X . |
$$ | . . O . . . . . . . . . . X . O X O . |
$$ | . . . . . . . . . . . . . . . X O X . |
$$ | . . . O . X . . . , . . . . . X O X . |
$$ | . . . . O X . . . . O . . O . X O X . |
$$ | . . . . . . . . . . . . . . . O O O . |
$$ | . . . . . . . . . . . . . . . . O . . |
$$ ---------------------------------------[/go]
Now comes the main point of my post, given black pulled back, how should white exploit all those weaknesses? LZ wants to crudely/bluntly get in all the cuts and forcing moves so that it can capture the cutting stone on the outside nicely with maximum forcing moves:
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[go]$$Wc LZ line
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$$ | . . X X O O O . . . . . . . . . . . . |
$$ | . . X O . X X O O O O O . O . . . . . |
$$ | . . X O . . . X X X X O X . . X X 4 . |
$$ | . . . O . . . . . . . X O O O O 1 2 . |
$$ | . . X . . . . . . . . X X . . 5 X 3 0 |
$$ | . . . . . . . . . . . . . . X O X 8 . |
$$ | . . . . . . . . . . . . . . . 6 7 9 . |
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$$ | . . . . . . . . . . . . . . . . X X . |
$$ | . . O . . . . . . . . . . X . O X O . |
$$ | . . . . . . . . . . . . . . . X O X . |
$$ | . . . O . X . . . , . . . . . X O X . |
$$ | . . . . O X . . . . O . . O . X O X . |
$$ | . . . . . . . . . . . . . . . O O O . |
$$ | . . . . . . . . . . . . . . . . O . . |
$$ ---------------------------------------[/go]
By getting the push at 13 (and then 15) here in sente white avoids black getting the atari there compared to if white just played atari at 17 after 11. The downside is by playing all the forcing moves you lose ko threats and also lost a bit in the corner by giving black a stone at s16 (e.g. no peep at
a for yose benefit).
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[go]$$Wcm11 LZ line contd
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$$ | . . X X O O O . . . . . . . . . . . . |
$$ | . . X O . X X O O O O O . O . . . a . |
$$ | . . X O . . . X X X X O X . . X X X . |
$$ | . . . O . . . . . . . X O O O O O X . |
$$ | . . X . . . . . . . . X X . . O X . X |
$$ | . . . . . . . . . . . . . 7 X O X X . |
$$ | . . . . . . . . . . . . . . 1 X O O . |
$$ | . . . . . . . . . . . . . . 3 2 . . . |
$$ | . . . , . . . . . , . . . . 5 4 . . . |
$$ | . . . . . . . . . . . . . . . 6 . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . X X . |
$$ | . . O . . . . . . . . . . X . O X O . |
$$ | . . . . . . . . . . . . . . . X O X . |
$$ | . . . O . X . . . , . . . . . X O X . |
$$ | . . . . O X . . . . O . . O . X O X . |
$$ | . . . . . . . . . . . . . . . O O O . |
$$ | . . . . . . . . . . . . . . . . O . . |
$$ ---------------------------------------[/go]
Lee chose to keep all those forcing moves in reserve, but that allowed black to connect solidly with 4. He then didn't capture with 5 (I guess not liking to give p11 forcing move) although LZ says that's the best local move (-2%) and better than extend (-6%). Wang astutely saw that the extend was not punished by saving the p13 cutting stone with
a (because then white jumps to m12 which hurts centre group whilst helping white run away), but jumping in the centre to help his group (though LZ says one point left of 6 is best) and encouraging white to spend another dame move to capture p13 (LZ says better than Lee's resistance of 7).
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[go]$$Wc Lee's line
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$$ | . . X X O O O . . . . . . . . . . . . |
$$ | . . X O . X X O O O O O . O . . . . . |
$$ | . . X O . . . X X X X O X . . X X . . |
$$ | . . . O . . . . . . . X O O O O . . . |
$$ | . . X . . . . . . . . X X . . 1 X . . |
$$ | . . . . . . . . . . . . . a X O X . . |
$$ | . . . . . . . . . . . . . 5 3 2 4 . . |
$$ | . . . . . . . . . . . 6 . . . . . . . |
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$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . 7 . . . . . |
$$ | . . . . . . . . . . . . . . . . X X . |
$$ | . . O . . . . . . . . . . X . O X O . |
$$ | . . . . . . . . . . . . . . . X O X . |
$$ | . . . O . X . . . , . . . . . X O X . |
$$ | . . . . O X . . . . O . . O . X O X . |
$$ | . . . . . . . . . . . . . . . O O O . |
$$ | . . . . . . . . . . . . . . . . O . . |
$$ ---------------------------------------[/go]
So LZ didn't like Lee's direct cut, preferring all the forcing moves. However, Elfv2 starts off thinking they are about the same value but then prefers his move, but with a key strategic difference: rather than immediately saving the cutting stone treat it as a bad aji creating exchange and then tenuki to lower left, combining attack of black's 2 stones there with growing your moyo and reducing black's centre. If black didn't defend at 4 but plays to help the f4 group (not a bad move, j3 and f6 both less than -2%) the idea seems to be white will naturally get some helping stones towards the l5/j8 area and this will help when pulling out the p12 stone. (Note 5 is not on the dot

). Though with more playouts Elf goes off 4 and thinks black should exchange m4-m3 and then f6.
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[go]$$Wc Elfv2
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$$ | . . X X O O O . . . . . . . . . . . . |
$$ | . . X O . X X O O O O O . O . . . . . |
$$ | . . X O . . . X X X X O X . . X X . . |
$$ | . . . O . . . . . . . X O O O O . . . |
$$ | . . X . . . . . . . . X X . . O X . . |
$$ | . . . . . . . . . . . . . 4 X O X . . |
$$ | . . . . . . . . . . . . . . 1 X 2 . . |
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$$ | . . . . . . . . . 5 . . . . . . . . . |
$$ | . . . . 3 . . . . . . . . . . . X X . |
$$ | . . O . . . . . . . . . . X . O X O . |
$$ | . . . . . . . . . . . . . . . X O X . |
$$ | . . . O . X . . . , . . . . . X O X . |
$$ | . . . . O X . . . . O . . O . X O X . |
$$ | . . . . . . . . . . . . . . . O O O . |
$$ | . . . . . . . . . . . . . . . . O . . |
$$ ---------------------------------------[/go]
MiniGo cormorant has a similar idea to Elf: it starts off liking LZ's inside cut/ataris/pushes, but then prefers Lee/Elf's outside cut and wants to play f6 rather than e7 as the tenuki.
Over on Fox FineArt's commentary included the direct cut and then tenuki to f6 like MiniGo as a good line, though intriguingly it thinks white is only 49.6% whilst LZ and MiniGo and Elf all think white's around 60%. Maybe FineArt can work with 6.5 komi now as the game is actually played with in Korea or it's just different eval?