Life In 19x19

There's a position from the train like a pro series, which I'm curious about.

Click Here To Show Diagram Code

[go]$$Bcm1
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O X . . O . . . . . . . X . . . . |
$$ | . . O X . . . . . , . . . . . , X . . |
$$ | . . O X . . . . . . . . . . . . . . . |
$$ | . . . B . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X . . . . . . . . . . . . . . . . |
$$ | . X O O . . . . . . . . . . . . . . . |
$$ | . X X O . . . . . , . . . . . O . . . |
$$ | . X O . . O . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ----------------------------------------[/go]

The question is how to respond as white. In thinking about the problem, I actually did consider the move that was given as the answer: But it was more of selecting the move because it felt right, and not for any other reason. But the problem I had with this move was this sequence: Now white's stones are cut off.

Given this line of reasoning, I selected the simpler move here: I had the suspicion it might be wrong since it was so simple. But it seems to do better with black's cover: Black's shape is destroyed.

So I liked that one better.

Back to the solution shape: I'm trying to think of why this might be better. Some thoughts: Basically, I don't understand why the suggested move is better. And the only reason it came to mind when I was looking at the problem was because I saw pros play something similar in some kind of shape like that. But I don't really get it at a practical level in this position.

Any thoughts?

Kirby wrote: But it was more of selecting the move because it felt right, and not for any other reason. But the problem I had with this move was this sequence:

$$Bcm1
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O X . . O . . . . . . . X . . . . |
$$ | . . O X . . . . . , . . . . . , X . . |
$$ | . . O X . . . . . . . . . . . . . . . |
$$ | . 8 7 X . . . . . . . . . . . . . . . |
$$ | . W 9 4 6 . . . . . . . . . . . . . . |
$$ | . . O 1 5 . . . . . . . . . . . . . . |
$$ | . . 3 2 . . . . . . . . . . . . . . . |
$$ | . . X , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X . . . . . . . . . . . . . . . . |
$$ | . X O O . . . . . . . . . . . . . . . |
$$ | . X X O . . . . . , . . . . . O . . . |
$$ | . X O . . O . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ----------------------------------------

Click Here To Show Diagram Code

[go]$$Bcm1
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O X . . O . . . . . . . X . . . . |
$$ | . . O X . . . . . , . . . . . , X . . |
$$ | . . O X . . . . . . . . . . . . . . . |
$$ | . 8 7 X . . . . . . . . . . . . . . . |
$$ | . W 9 4 6 . . . . . . . . . . . . . . |
$$ | . . O 1 5 . . . . . . . . . . . . . . |
$$ | . . 3 2 . . . . . . . . . . . . . . . |
$$ | . . X , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X . . . . . . . . . . . . . . . . |
$$ | . X O O . . . . . . . . . . . . . . . |
$$ | . X X O . . . . . , . . . . . O . . . |
$$ | . X O . . O . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ----------------------------------------[/go]

Is that the best sequence? What about:

Kirby wrote: Given this line of reasoning, I selected the simpler move here:

$$Bcm1
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O X . . O . . . . . . . X . . . . |
$$ | . . O X . . . . . , . . . . . , X . . |
$$ | . . O X . . . . . . . . . . . . . . . |
$$ | . . W X . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X . . . . . . . . . . . . . . . . |
$$ | . X O O . . . . . . . . . . . . . . . |
$$ | . X X O . . . . . , . . . . . O . . . |
$$ | . X O . . O . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ----------------------------------------

Click Here To Show Diagram Code

[go]$$Bcm1
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O X . . O . . . . . . . X . . . . |
$$ | . . O X . . . . . , . . . . . , X . . |
$$ | . . O X . . . . . . . . . . . . . . . |
$$ | . . W X . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X . . . . . . . . . . . . . . . . |
$$ | . X O O . . . . . . . . . . . . . . . |
$$ | . X X O . . . . . , . . . . . O . . . |
$$ | . X O . . O . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ----------------------------------------[/go]

One problem with that sequence is the issue of A after this exchange (i.e. black doesn't have to play the way you showed).

Thanks for the first sequence: Of course, that makes sense. Somehow, I automatically read "breaking through", since I compared it to the variation I had in mind. Regarding your second comment, do you mean white doesn't have to play that way? Still seems OK for white to me.

My question still remains about why the given move is better than the simple one, specifically. Is it because black has the forcing move here? If followed by 'a' or 'b', above, is this that bad for white?

Kirby wrote:

$$Bcm1
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O X . . O . . . . . . . X . . . . |
$$ | . . O X . . . . . , . . . . . , X . . |
$$ | . . O X . . . . . . . . . . . . . . . |
$$ | . . O X . . . . . . . . . . . . . . . |
$$ | . . . B . . . . . . . . . . . . . . . |
$$ | . a O b . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X . . . . . . . . . . . . . . . . |
$$ | . X O O . . . . . . . . . . . . . . . |
$$ | . X X O . . . . . , . . . . . O . . . |
$$ | . X O . . O . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ----------------------------------------

Click Here To Show Diagram Code

[go]$$Bcm1
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O X . . O . . . . . . . X . . . . |
$$ | . . O X . . . . . , . . . . . , X . . |
$$ | . . O X . . . . . . . . . . . . . . . |
$$ | . . O X . . . . . . . . . . . . . . . |
$$ | . . . B . . . . . . . . . . . . . . . |
$$ | . a O b . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X . . . . . . . . . . . . . . . . |
$$ | . X O O . . . . . . . . . . . . . . . |
$$ | . X X O . . . . . , . . . . . O . . . |
$$ | . X O . . O . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ----------------------------------------[/go]

If followed by 'a' or 'b', above, is this that bad for white?

Given this particular board, I think a and b are problematic for white. b seems kind of useless, given how strong black is in lower left, as well as leaving the awful peep aji behind, while a will leave black very strong (assuming black follows with something like E11). I will definitely prefer black in this position. Whether this thinking applies more generally is hard to say.

One possible thing for white to focus on is to keep the four black stones in the upper-left weak and profit from harassing them. From this point of view, I (kind of) can see why the kosumi at A13 may work better, since it doesn't force black to respond. But this is more of an after-thought, if I look at this position as a problem and try to reverse-engineer the reasons for this solution

If I look at this as a game: the board is very open on the right, lower and upper sides, while the left side is pretty boring. So what I would like to do as white is to take sente in the upper-left and play some large point such as K17, or R10.

R10 is just large, while K17 seems "hot" since it involves unsettled groups. For that reason I feel the upper side is more important...

Also - any idea how was this position created? I am trying to figure out the order of moves in the upper-left and I cannot...

alphaville wrote:One possible thing for white to focus on is to keep the four black stones in the upper-left weak and profit from harassing them.

Somehow, this resonates with me a little bit. I guess the solution move keeps black weak, whereas C14 lets black get strong.

alphaville wrote: Also - any idea how was this position created? I am trying to figure out the order of moves in the upper-left and I cannot...

I don't know how the position was created. The book has various problem positions. Maybe it was from somebody's game that the author knew about.

I found the game. The game is from 2003: Lee Changho 9d vs. Luo Xihe 9d.

Here it is:


I guess white's pressure on the black stones does turn out useful.

Oh, cool, it's from a real game - and a very interesting one!

Looking at the game, I can do some more reverse-engineering: B13 seems to be the most resilient move after black plays C18-E18 combination, since if white played instead at C14 (or C13), he would have to worry about black pushing at C14 and cutting.

So white is also clearly looking at the C8 invasion already when he played B13, and trying to help black as little as possible.

All looks good - but I doubt I will find this kind of fancy move in my own games

Click Here To Show Diagram Code

[go]$$Bcm1
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O X . . O . . . . . . . X . . . . |
$$ | . . O X . . . . . , . . . . . , X . . |
$$ | . . O X . . . . . . . . . . . . . . . |
$$ | . . . X . . . . . . . . . . . . . . . |
$$ | . W . . . . . . . . . . . . . . . . . |
$$ | . . O 1 . . . . . . . . . . . . . . . |
$$ | . . 3 2 4 . . . . . . . . . . . . . . |
$$ | . . X , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X . . . . . . . . . . . . . . . . |
$$ | . X O O . . . . . . . . . . . . . . . |
$$ | . X X O . . . . . , . . . . . O . . . |
$$ | . X O . . O . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ----------------------------------------[/go]

Apart from this being a plausible way for White to respond, why have you assumed (a) Black will play 1 - he didn't in the game - and (b) that White will answer it? White can consider playing where Black actually played, i.e. on the upper side.

It's interesting that your intuition threw up the right initial defence for White. These low moves generally seem to trouble amateurs. A variant on the theme is when there is a fourth line vs third line series of pushes going along and the third line pro player makes a second-line slide where amateurs typically make a third-line jump, as in Chitoku-Chiteki, 1813:



But having said all that, the upper left position has occurred elsewhere in pro play. Yasui Santetsu played the narabi at C7 in 1620. Iwamoto chose the kosumi as here in 1953 and, just after Yi Chang-ho aboye, Yamada Kimio chose the nobi at C6. So the right move is not cut-and-dried. The overall position is bound to be a factor, but the local choice may also be a matter of style.

This move helps Black the least out of the plausible moves.

Click Here To Show Diagram Code

[go]$$Bcm1
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O X . . O . . . . . . . X . . . . |
$$ | . . O X . . . . . , . . . . . , X . . |
$$ | . . O X . . . . . . . . . . . . . . . |
$$ | . . c B . . . . . . . . . . . . . . . |
$$ | . b a . . . . . . . . . . . . . . . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X . . . . . . . . . . . . . . . . |
$$ | . X O O . . . . . . . . . . . . . . . |
$$ | . X X O . . . . . , . . . . . O . . . |
$$ | . X O . . O . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ----------------------------------------[/go]

My first thought was at 'a', because the kosumi is not really in my "vocabulary". This leaves push and cut at 'b', and Black will not be in real danger after that. I considered 'c', but after Black extends, White doesn't have a good next move locally, and Black can connect to the bottom left. Kosumi at 'b' is nice because now it's Black who doesn't have a good next move locally, and he has to struggle a bit to live.

John Fairbairn wrote:Apart from this being a plausible way for White to respond, why have you assumed (a) Black will play 1 - he didn't in the game - and (b) that White will answer it? White can consider playing where Black actually played, i.e. on the upper side.

I would say that I didn't necessarily think that black would play there. Specifically, I was trying to compare the relative merits of the 3rd line push vs. the 2nd line move. It seemed that the 3rd line push had a benefit: black definitely cannot block white off with 1.

That being said, since black isn't interested in playing there to begin with, maybe that says something about my logic.

alphaville wrote:Oh, cool, it's from a real game - and a very interesting one!

Looking at the game, I can do some more reverse-engineering: B13 seems to be the most resilient move after black plays C18-E18 combination, since if white played instead at C14 (or C13), he would have to worry about black pushing at C14 and cutting.

So white is also clearly looking at the C8 invasion already when he played B13, and trying to help black as little as possible.

All looks good - but I doubt I will find this kind of fancy move in my own games

Seems logical, looking at the way the played.

Maybe my problem is that I'm thinking too locally, trying to find a reason that 2nd line is better than 3rd, or whatever. Maybe it's better to read out the sequence I want to play, and see which local move will serve me best 10 moves down the line.

Shaddy wrote:This move helps Black the least out of the plausible moves.

$$Bcm1
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O X . . O . . . . . . . X . . . . |
$$ | . . O X . . . . . , . . . . . , X . . |
$$ | . . O X . . . . . . . . . . . . . . . |
$$ | . . c B . . . . . . . . . . . . . . . |
$$ | . b a . . . . . . . . . . . . . . . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X . . . . . . . . . . . . . . . . |
$$ | . X O O . . . . . . . . . . . . . . . |
$$ | . X X O . . . . . , . . . . . O . . . |
$$ | . X O . . O . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ----------------------------------------

Click Here To Show Diagram Code

[go]$$Bcm1
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O X . . O . . . . . . . X . . . . |
$$ | . . O X . . . . . , . . . . . , X . . |
$$ | . . O X . . . . . . . . . . . . . . . |
$$ | . . c B . . . . . . . . . . . . . . . |
$$ | . b a . . . . . . . . . . . . . . . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X . . . . . . . . . . . . . . . . |
$$ | . X O O . . . . . . . . . . . . . . . |
$$ | . X X O . . . . . , . . . . . O . . . |
$$ | . X O . . O . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ----------------------------------------[/go]

My first thought was at 'a', because the kosumi is not really in my "vocabulary". This leaves push and cut at 'b', and Black will not be in real danger after that. I considered 'c', but after Black extends, White doesn't have a good next move locally, and Black can connect to the bottom left. Kosumi at 'b' is nice because now it's Black who doesn't have a good next move locally, and he has to struggle a bit to live.

Yeah, 'a' was something that came to mind, too. It feels like something someone around my level would play :-p

I think they key point here is you need to consider the pros and cons in the local continuations if black and white play first, and then look at the global position to see, given the expected flow of the game, who is likely to play first locally and who that's good for.

So my first thought is I don't want to keep on pushing from behind as that increases the strength of the black wall (which looking globally is not strong, white has a pincer stone so likely wants to attack it), but jump ahead. So there's the 3rd line move which has this obvious weakness (maybe don't need to play 3-4, but if you don't maybe white would capture on other side and let you into corner which is a big loss, but I did it to make threat on 3 stones obvious):

Click Here To Show Diagram Code

[go]$$Bcm1
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . 4 3 . . . . . . . . . . . . . . . . |
$$ | . . O X . . O . . . . . . . X . . . . |
$$ | . . O X . . . . . , . . . . . , X . . |
$$ | . 8 O X . . . . . . . . . . . . . . . |
$$ | . 6 5 1 . . . . . . . . . . . . . . . |
$$ | . 7 2 . . . . . . . . . . . . . . . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . a . . . . . . . . . . . . . . . . . |
$$ | . . X , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X . . . . . . . . . . . . . . . . |
$$ | . X O O . . . . . . . . . . . . . . . |
$$ | . X X O . . . . . , . . . . . O . . . |
$$ | . X O . . O . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ----------------------------------------[/go]

So this means white's one point jump out to the centre (if white is next to play in the area) has a classic cutting tesuji weakness (maybe 2 at 6 directly more stylish, but W might resist). Also a above is sente, but you don't want to play it too early as it fixes the jump weakness, but might be relevant for c8 gap:

Click Here To Show Diagram Code

[go]$$Wcm1
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . O X . . . . . . . . . . . . . . . . |
$$ | . . O X . . O . . . . . . . X . . . . |
$$ | . . O X . . . . . , . . . . . , X . . |
$$ | . O O X . . . . . . . . . . . . . . . |
$$ | . O X X . . . . . . . . . . . . . . . |
$$ | 7 X O 8 . . . . . . . . . . . . . . . |
$$ | 5 2 O 6 1 . . . . . . . . . . . . . . |
$$ | . 3 4 . . . . . . . . . . . . . . . . |
$$ | . . X , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X . . . . . . . . . . . . . . . . |
$$ | . X O O . . . . . . . . . . . . . . . |
$$ | . X X O . . . . . , . . . . . O . . . |
$$ | . X O . . O . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ----------------------------------------[/go]

Compare this to jumping following the kosumi, black's typical attempt to cut the shape is peep and cut at waist, but it doesn't work as white's corner stick is now 4 not 3 stones long (and white is safe even if black 2 is connected):

Click Here To Show Diagram Code

[go]$$Wcm1
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . 3 2 . . . . . . . . . . . . . . . . |
$$ | . . O X . . O . . . . . . . X . . . . |
$$ | . . O X . . . . . , . . . . . , X . . |
$$ | . . O X . . . . . . . . . . . . . . . |
$$ | . 6 7 X . . . . . . . . . . . . . . . |
$$ | . O 8 4 . . . . . . . . . . . . . . . |
$$ | . 9 O 5 1 . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X . . . . . . . . . . . . . . . . |
$$ | . X O O . . . . . . . . . . . . . . . |
$$ | . X X O . . . . . , . . . . . O . . . |
$$ | . X O . . O . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ----------------------------------------[/go]

So if white wants to play next in the area to jump out, the kosumi is better (though there's also e13 knight jump to consider which stops the tesuji of diagram 2, but leaves another cut).

How about if black first? If black tries to cover the 3rd line move on 4th line (5th at a is flimsy shape with an obvious gap) white can maybe push out though black has that cutting tesuji on 2nd line to make liberty troubles (maybe corner hane first) but white might allow the cut and develop the outside group:

Click Here To Show Diagram Code

[go]$$Bcm1
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O X . . O . . . . . . . X . . . . |
$$ | . . O X . . . . . , . . . . . , X . . |
$$ | . . O X . . . . . . . . . . . . . . . |
$$ | . 4 3 X . . . . . . . . . . . . . . . |
$$ | . 5 O 2 . . . . . . . . . . . . . . . |
$$ | . . O 1 a . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X . . . . . . . . . . . . . . . . |
$$ | . X O O . . . . . . . . . . . . . . . |
$$ | . X X O . . . . . , . . . . . O . . . |
$$ | . X O . . O . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ----------------------------------------[/go]

Or maybe white would look at the whole board and tenuki, extending that lone stone on the top is clearly an important place. Maybe black spends another move to connect, and white extends again? Or 4 somewhere else like lower left or right side?

Click Here To Show Diagram Code

[go]$$Bcm1
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O X . . O . . 2 . . 4 . X . . . . |
$$ | . . O X . . . . . , . . . . . , X . . |
$$ | . . O X . . . . . . . . . . . . . . . |
$$ | . . . X . . . . . . . . . . . . . . . |
$$ | . . O 3 . . . . . . . . . . . . . . . |
$$ | . . O 1 . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X . . . . . . . . . . . . . . . . |
$$ | . X O O . . . . . . . . . . . . . . . |
$$ | . X X O . . . . . , . . . . . O . . . |
$$ | . X O . . O . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ----------------------------------------[/go]

Compare if the same idea happens with kosumi (black's reinforcement with 3 is a bit different):

Click Here To Show Diagram Code

[go]$$Bcm1
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O X . . O . . 2 . . 4 . X . . . . |
$$ | . . O X . . . . . , . . . . . , X . . |
$$ | . . O X . . . . . . . . . . . . . . . |
$$ | . . . X . . . . . . . . . . . . . . . |
$$ | . O . . . . . . . . . . . . . . . . . |
$$ | . . O 1 . . . . . . . . . . . . . . . |
$$ | . . 3 . . . . . . . . . . . . . . . . |
$$ | . . X , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X . . . . . . . . . . . . . . . . |
$$ | . X O O . . . . . . . . . . . . . . . |
$$ | . X X O . . . . . , . . . . . O . . . |
$$ | . X O . . O . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ----------------------------------------[/go]

How to judge these 2 results? I think they are both globally good for white who got to settle nicely on the top side. How about the left side shape? c10 got an extra stone in the 2nd, so maybe c8 area stronger, but also the wall is not so thick and has a cut/peep. Top one the black wall is thicker and has double hane if white tries to crawl along left side, so is probably a bit worse for territory but better thickness to top side but not left side.

So I think the key point is white is happy with either of these results (though perhaps one subtly better), so black won't allow that and will pincer on the top side, which means the fact kosumi has better shape for white to come out later is most important. Also from an efficiency standpoint c13 makes c12 look a bit odd.

Uberdude wrote:I think they key point here is you need to consider the pros and cons in the local continuations if black and white play first, and then look at the global position to see, given the expected flow of the game, who is likely to play first locally and who that's good for.

That's a pretty tall order I appreciate your analysis. I might go as far as to evaluate some pros and cons of a local continuation with me playing first, but I rarely think of all combinations of who is playing first locally vs. the global position, the flow of the game, and who is likely to play first.

I guess I must be too lazy.

Uberdude wrote: So I think the key point is white is happy with either of these results (though perhaps one subtly better), so black won't allow that and will pincer on the top side, which means the fact kosumi has better shape for white to come out later is most important. Also from an efficiency standpoint c13 makes c12 look a bit odd.

Nice thought process to get to that conclusion. Seems a bit daunting to me. Maybe this problem is just a bit too difficult for me to assess properly.