One play is Elf's top choice, one play is from the game, which loses 16% to the top choice, by Elf's reckoning, and one play is Elf's second choice, which loses 3½%, and so is probably playable.
Enjoy!
_________________ The Adkins Principle: At some point, doesn't thinking have to go on? — Winona Adkins
I'll say 'a'. It makes the stones on top consistent. And it also kind of answers white's approach, which is gospel-esque.
'b' is also nice for attacking, so it's a little bit of a tough call. And approaching at 'c' is always pretty big. Hard problem, because I can see benefits to each move.
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Whatever the correct move is, the follow up sequences are complicated for bot and human alike. Human intuition seems to trump low bot playouts in this position and the bot sequences are volatile. In the end Bill's advice is best for white.
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Going with John's control of the diagonals, 'b' really stands out to my eyes. It even seems that White would have to defend at the top (maybe attach, hane, draw back), so one can then see whether Black needs to defend the top stones afterwards. I don't think that White can press too much around 'a', for example a keima would just be cut and fought.
So, my expectation would maybe be something like this:
Whatever the correct move is, the follow up sequences are complicated for bot and human alike. Human intuition seems to trump low bot playouts in this position and the bot sequences are volatile. In the end Bill's advice is best for white.
What advice is that?
_________________ The Adkins Principle: At some point, doesn't thinking have to go on? — Winona Adkins
'b' highlights the defects in white's shape but just as importantly reinforces black's corner. Black's knight's move is cuttable, as we see in any number of classical games. Usefully, if white chooses to reinforce it's not automatically sente. Black may be well 'c' next.
'c' is a corner approach. Need I say more? Yay corners!
'a' looks wimpy. Black is putting a lot of stones on the top, but it's not sente and there's not much of a follow up. I'd be looking to try and kick at White first to force him to add a stone before playing 'a'. At least we might get a target to aim at.
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Kaya handle: Test
Move 'a' seems too close to black's other stones - a bit over-concentrated when the board is this open. White can call C17 light and tentuki to one of several big points on the lower half of the board.
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Rank: UK 4 dan
KGS: Uberdude 4d
OGS: Uberdude 7d
Black has two obvious shape problems, so first let's look at those.
The press in upper left attempts to split the two marked stones and ruin the big black territory he's trying to build there. If black submits with crawl that's good for white to bulldoze through black's potential.
So how about push and cut? Usually this is a bit of an overplay, but with the nearby support black looks fine: if white settles on the top side white will get in trouble on the left, and the black corner isn't going to die. So it's not urgent for black to fix this problem.
And even if black did play here I prefer to kick first to make White heavier so I have a target to attack if white tenukis to another big place (to avoid black fixing the problem in sente).
Upper right White can slice through the Knight move. Baduk doctor did a nice video on this: https://youtu.be/tnT3_J73JJE. White has the ladder so can interpose the cut of 9 to ensure 11 is sente so black can't play at 12 in sente before 13.
[go]$$Wcm11 $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . X . . . . . . X . . . O X X 4 . | $$ | . . . , . . . . . X . . a . O O X 3 . | $$ | . . O . . . . X . . . O . . . X O 7 . | $$ | . . . . . . . . . O . . . . X X O . . | $$ | . . . . . . . . . . . . . . . W X O . | $$ | . . . . . . . . . . . . . . . . X 1 . | $$ | . . . . . . . . . . . . . . . . 2 5 . | $$ | . . . , . . . . . , . . . . . , 6 . . |[/go]
Black's not collapsing, but this looks better for white. The marked white cutting stone is troublesome.
So jumping at b looks good, as this could change some of the above sequences and allow black to fight more strongly. It's sente to cut at d, so white probably answers like so.
Insetsu played the kosumi at a, which loses 16% to par (assuming komi). I suspect that it is a mistake with no komi, as well. You can see the attraction of forming a nice sized territory with the 5th line keima.
Elf also reckoned that Senkaku's approach, , is a mistake. It invites Black to strengthen himself and play where he wants to play. Elf also thinks that is a mistake by comparison with the jump to a.
As pwaldron points out, White likes cutting across the keima. Elf has a slight preference for , but 18 is also good. We'll come back to that variation. OC, Black does not capture the cutting stone in this situation.
approaches the bottom left corner, and White plays a one space pincer. Then Black approaches the bottom right corner and White plays kosumi against . Next, and bolster Black's position in the top right.
White strengthens his stones on the right, which in turn puts pressure on the Black corner. Black bolsters the corner with a hane-and-connect. OC, Black cannot afford to connect to the atari with , and captures the stone.
goes after the four White stones on the top side. plays kikashi, and then lays claim to the right side. IMO, is nicely placed. Now approaches the bottom left corner.
This approach is probably playable. It got so few rollouts, however, that Elf does not even show White's response. With so few rollouts we cannot be sure of its winrate estimate.
Elf prefers the jump to , which strengthens Black in the top right and threatens to cut White in two. connects the White stones. Elf thinks that the jump attachment at a is also good. FatKata prefers to enclose the bottom left corner at b. After , Black approaches the bottom left corner. White now makes a base in the top left with , then plays the kick and lays claim to the top side, as pwaldron and Uberdude suggest. Then encloses the bottom right corner.
now initiates a driving tesuji which pushes out into the center. Black is strengthened in the center, but is a severe cut across the Black keima in the top right.
The one space jump jumped out at me. And the kosumi in the top left just seemed passive and pedestrian. If it realistically threatened the White approach stone, that would be a different matter.
BTW, after the one space jump I like the jump attachment to induce the 2d line hane with sente, and then enclosing the bottom left corner.
_________________ The Adkins Principle: At some point, doesn't thinking have to go on? — Winona Adkins
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Rank: UK 2d Dec15
KGS: mathmo 4d
IGS: mathmo 4d
Speculatively: Current position: 1. Its a scary position when B has no territory yet compared to W. Defending a seems too slack making H15 bad. Hence, keeping the tight pressure before defending seems important. So b looks attractive when it is locally big anyway for the upper right. With W's shape quite bad overall with lots of different aji that B doesn't want to commit to without a follow up because W defending is also valuable when B is split too. 2. c is interesting for sure, hoping to pincer the upper left but not daring to yet because it may owe another move when B can't get that efficiency yet from the attack, at least not from the J13 direction. 3. I'll guess that c is the game play because it looks like leaving too much aji of a and allowing W to settle the left by counterattack. And because players before loved to play it too much. And that b is best then a. B risks losing the ladder which affects R15. 4. Even with the ladder, W has enough stones to make shape with R15 and get some shape or sacrifice.
Opp to play 1. a is very tempting to try but it doesn't seem realistic. Without support it will induce the push and cut. Otherwise C12 seems tempting in response to H12 to prepare a. However, B may still tenuki. Or the left C6 seems big as W is weak in the upper left and B is potentially 8th line with H15.
Past: 1. What a strange position to see centre flying. H15 doesn't seem right.
Check: 1. Partially correct. I should simply not have worried about the upper left yet. Neither side can do much yet.
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, is a mistake. It invites Black to strengthen himself and play where he wants to play. Elf also thinks that 
is a mistake by comparison with the jump to a.
, but 18 is also good. We'll come back to that variation. OC, Black does not capture the cutting stone in this situation. 
approaches the bottom left corner, and White plays a one space pincer. Then Black approaches the bottom right corner and White plays kosumi against 
and 
bolster Black's position in the top right.
, and 
captures the 
stone.
goes after the four White stones on the top side. 
plays kikashi, and then 
lays claim to the right side. IMO, 
approaches the bottom left corner.
, which strengthens Black in the top right and threatens to cut White in two. 
, then 
lays claim to the top side, as pwaldron and Uberdude suggest. 
encloses the bottom right corner. 
extends, but enclosing the bottom left corner at a is also good. 
is a severe cut across the Black keima in the top right.