I recently had an opponent play the marked stone as part of the 4-4 attach and extend joseki:

Click Here To Show Diagram Code

[go]$$c
$$ +---------------------------------------+
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . X . . . . . , . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X . . . . . . . . . . . . . b . . |
$$ | . . . . . . . . . . . . . . . X a . . |
$$ | . . . . . . . . . . . . . . O O X . . |
$$ | . . . X . . . . . . . . . . . W X . . |
$$ | . . X , . O . . . O . . . . . O O . . |
$$ | . . X O . . . . . . . . . . . . . . . |
$$ | . . O . O . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ +---------------------------------------+[/go]

What is the best way to respond to this? I decided to tenuki. I reasoned that although white can cut off some of my stones with A, black B would still allow me to create a living group by extending up. White's group on the lower right seems fairly strong to me. So, A does not provide a benefit to white other than a few points, further making it unlikely that white would play A in the near term. I looked this up in my normal joseki references, but it's never mentioned.

Edited: Removed the black stone at O17 to correct the stone imbalance noted by dfan and to add b as noted by Uberdude. Accidentally included the move that I made next.

Are you missing a stone? I count 11 Black stones and 10 White stones so it should be White's turn.

Tenuki is good: white's move is slow. I presume you missed a label 'b' at s7? If white cuts then you can atari and crawl under to connect up to r10 and sacrifice q7 for now (plus still has aji). Locally speaking, if you want to add a move q8 is probably best. If you didn't have r10 then white would be aiming to pincer and attack the group as a whole, rather than just cutting to capture 2 stones in gote (in that case you'd just atari from the outside). The kind of positions white plays that connection as a good move is typically when there is a black double approach stone so there is a severe cut threat, such as this AlphaGo game: http://www.alphago-games.com/view/event ... /9/move/40.

Thank you both! I fixed the erroneously added stone. This is helpful. It's reassuring that my assessment of these positions is now occasionally accurate, rather than consistently wrong.

Click Here To Show Diagram Code

[go]$$Bc
$$ +---------------------------------------+
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . X . . . . . 1 . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X . . . . . . . . . . . . 3 . . . |
$$ | . . . . . . . . . . . . . . . X . . . |
$$ | . . . . . . . . . . . . . . O O X . . |
$$ | . . . X . . . . . . . . . . . W X . . |
$$ | . . X , . O . . . O . . . . . O O . . |
$$ | . . X O . . . . . . . . . . . . . . . |
$$ | . . O . O . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ +---------------------------------------+[/go]

My reply?

First choice:

Local choice: Maybe , depending on the whole board at the time. There are four main types of basic connections against a cut: the solid connection ("a"), the hanging connection ("b" or S-07), the ladder connection, which this is, where the cutting stone can be caught in a ladder, and the net connection, where the cutting stone can be caught in a net.

Edit: Ah! I see that is also Uberdude's local suggestion. Great minds, and all that.

_________________
The Adkins Principle:
At some point, doesn't thinking have to go on?
— Winona Adkins

Visualize whirled peas.

Everything with love. Stay safe.

I ended up playing O17. What makes you prefer 1 to O17? 1 was actually my first thought, but I talked myself out of it. With the stone at R10, I reasoned that O17 would give me both the small knights move with the ideal extension already in place.

My instinct is this, but I’m generally greedy:

Click Here To Show Diagram Code

[go]$$c
$$ +---------------------------------------+
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . X . . . . . , . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X . . . . . . . . . . . . d . . . |
$$ | . . . . . . . . . . . . . . . X . . . |
$$ | . . . . . . . . . . . . . . O O X . . |
$$ | . . . X . . . . . . B . . . . W X . . |
$$ | . . X , . O . . . O . . . . . O O . . |
$$ | . . X O . . . . . . . . . . . . . . . |
$$ | . . O . O . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ +--------------------------------[/go]

That being said, I like ‘d’ now that I see it.

_________________
be immersed

I would also play K16 like Bill Spight did, and my reason for preferring it to O17 is that 1) it is working on a global scale with both D16 and Q16, and 2) making an enclosure starting from a star point is less useful than when you start with a 3-4 point, because there are still good places for White to invade. On the other hand, if the Q16 stone were at R16, then I would play P16 or P17 rather than K16, and if the stone were at Q17 (which is probably more plausible given the position of R10), I'd likely play at Q15.

P.S. I just showed the position to Leela, and it strongly preferred O17 to K16, so go figure!

The K16 move strikes me as an amateurish move - you see it a lot in handicap games. While it can hardly be called a bad move, it's a form of posturing. It doesn't do anything specific.

Think of it like this. You've decided to paint the house. A bit of preparation's no bad thing, so you some paint and brushes, and a few other odds and ends.

But then, instead of getting on with the work, the K16 kind of painter decides to go back to the hardware shop and buy some more brushes, maybe some new overalls, and maybe also the latest gizmo. All these things might come in useful some day, so they are not necessarily wasted purchases, but they do waste time and you might end up getting distracted, and the house never gets painted...

The O17 painter gets on with the work, and if he finds out later he needs a special brush to get behind the radiators, he'll go and buy just that. He's efficient, he doesn't get distracted, and he's in control.

On the go board, the K16 player risks handing the initiative to White. The O17 player keeps the initiative.

There are other heuristic ways to justify O17. For example, you are supposed to play in areas with the most development opportunities. K16 is developmental but ignores opportunities. Or the Mizokami counting method: both Black and White have 5 stones on the right side so Black should be prudent. That would fit either the narabi defence or O17, but K16 would be seen as too grandiose to be prudent. Or there's the domino/Newton's balls theory: the lower right Black group has been affected, so Black must respond by defending that. Narabi would do that, and O17 could claim to do that indirectly, but K16 could not. There is also fuseki theory: if it's now the middle game (discuss!), a fuseki move like K16 is anachronistic. Narabi is a middle game move. O17 is too, in that it is trying to confirm the initiative.

Another relevant heuristic here, especially with Halloween still in the air, is "Beware of ippo-ji."

(The narabi is a standard play here, as is a White play there, and is often shown as an example of "my best point is the enemy's best point.")

Some day we may have a similar AG-zero class evaluation tool;
it'll be interesting to see its preference here
( and on any Chinese variants, versus a corner approach ).

Click Here To Show Diagram Code

[go]$$Bc
$$ +---------------------------------------+
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . X . . . . . 1 . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . X . . . |
$$ | . . . . . . . . . . . . . . O O X . . |
$$ | . . . X . . . . . . . . . . . W X . . |
$$ | . . X , . O . . . O . . . . . O O . . |
$$ | . . X O . . . . . . . . . . . . . . . |
$$ | . . O . O . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ +---------------------------------------+[/go]

I know that O-17 is the modern style. I guess Leela likes it, too, eh?

However, I do not think that there is anything wrong with sanrensei, and in addition K-16 looks to develop on both the right and left sides; it will work with either one. O-17 develops the right side.

Either way, after I think that Black is ahead.

_________________
The Adkins Principle:
At some point, doesn't thinking have to go on?
— Winona Adkins

Visualize whirled peas.

Everything with love. Stay safe.

This evaluation could be entirely true, as far as top humans go.
Suppose AGZ's win rate (for ) drops significantly with sanrensei ( here, or ) versus a corner move ( like o17 ).
It's entirely possible even the top human brains (as ) cannot take advantage of this 'slack' sanrensei. In this sense, "there's nothing wrong with it" is true, because it makes little difference to humans.
But against an AGZ class engine, it could be a game-losing move.

For what it's worth, Leela still thinks Black is well ahead after K16, it just likes O17 even more (I think the win rates for Black of the two moves were something like 64% and 60%).

It would be interesting to see what the actual win rates, not just estimated win rates, are for Leela vs. Leela games, starting from these two positions. (Unfortunately AlphaGo vs. AlphagGo games for these two positions is not going to happen. )

_________________
The Adkins Principle:
At some point, doesn't thinking have to go on?
— Winona Adkins

Visualize whirled peas.

Everything with love. Stay safe.

Both K16 and O17 (and many other normal moves in large open areas) are excellent choices, there is nothing wrong with any of them, it is just a matter of style.

Just chose a move you feel good about, and don't be afraid to experiment with different such moves, see what works for you.

_________________
Sorin - 361points.com

While I thoroughly agree with the advice to enjoy experimenting, I'm unsure it's just a matter of style.

In the following position, in a 3-stone game, Black played sanrensei as shown. But Kitani commented that sanrensei at A was better because of the position of the White stone. He said it made it easier to play Black B.

Surely if there's one thing that AlphaGo has shown it is that the whole board does matter.




Later in the same game, Black did play the other sanrensei but again Kitani criticised this, not as a bad move but because he thought there was a better one available. He recommended the irregular approach of Black A, with White B, Black C to follow. This gives Black the initiative with more opportunities to control the game.

In the first diagram the lower side san ren sei is clearly inferior to that on the right side because the mokuhazushi white stone in the upper left is in a position that restricts (reduces) the influence of the san ren sei on the bottom.