A useful, easy shape: atari on 3rd line

billywoods · Post by **billywoods** » Mon Jan 28, 2013 5:31 am

Aimed at DDKs / weak SDKs / anyone who doesn't know the shape already, because it's really useful.

I post this not because it's profound, but because it's an observation I made when I was 12 kyu or so that has proved surprisingly useful, and I still see some strong SDK players on KGS (mis)read it from scratch each time. It's simple and comes up a lot, at least in my games. I'm surprised it's not taught as standard in the same league as nets and snapbacks, because it's a very useful shape to be able to spot instantly.

Anyway, I hope this post will be useful to someone. It's longish, so I wrote it in dribs and drabs in a rush - sorry! - so corrections and comments appreciated.

Motivated by this diagram:

Click Here To Show Diagram Code: [go]$$c Atari on the second line $$ . . . . . . . . . . . $$ . . . . . . . . . . . $$ . . . . . O . . . . . $$ . . . . O X O . . . . $$ . . . . . . . . . . . $$ --------------------[/go]

in which black is almost always outright dead even with other stones lying around, I asked myself: does the following work for white? In this post I explore this shape and related shapes.

Click Here To Show Diagram Code: [go]$$c Atari on the third line $$ . . . . . . . . . . . $$ . . . . . O . . . . . $$ . . . . O X O . . . . $$ . . . . . . . . . . . $$ . . . . . . . . . . . $$ --------------------[/go]

Of course, as it stands the answer is no:

So what sorts of things might happen? I find the most useful thing is strengthening of the marked white stone:

Click Here To Show Diagram Code: [go]$$c White to play and kill 2 stones $$ . . . . . . . . . . . $$ . . . . . O . . . . . $$ . . . . O X O . . . . $$ . . . . . B O . . . . $$ . . . . . . . . . . . $$ --------------------[/go]

Click Here To Show Diagram Code: [go]$$c White to play and kill 2 stones $$ . . . . . . . . . . . $$ . . . . . O . . . . . $$ . . . . O X O O . . . $$ . . . . . B . . . . . $$ . . . . . . . . . . . $$ --------------------[/go]

Click Here To Show Diagram Code: [go]$$c White to play and kill 2 stones $$ . . . . . . . . . . . $$ . . . . . O . . . . . $$ . . . . O X O . . . . $$ . . . . . B . O . . . $$ . . . . . . . . . . . $$ --------------------[/go]

Click Here To Show Diagram Code: [go]$$c White to play and kill 2 stones $$ . . . . . . . . . . . $$ . . . . . O O . . . . $$ . . . . O X O . . . . $$ . . . . . B . . . . . $$ . . . . . . . . . . . $$ --------------------[/go]

Click Here To Show Diagram Code: [go]$$c White to play and kill 2 stones $$ . . . . . . . . . . . $$ . . . . . O . O . . . $$ . . . . O X O . . . . $$ . . . . . B . . . . . $$ . . . . . . . . . . . $$ --------------------[/go]

Click Here To Show Diagram Code: [go]$$c White to play and kill 2 stones $$ . . . . . . . . . . . $$ . . . . . O . . . . . $$ . . . . O X O . O . . $$ . . . . . B . . . . . $$ . . . . . . . . . . . $$ --------------------[/go]

Click Here To Show Diagram Code: [go]$$c White to play and kill 2 stones $$ . . . . . . . . . . . $$ . . . . . O . . . . . $$ . . . . O X O . . . . $$ . . . . . B . . O . . $$ . . . . . . . . . . . $$ --------------------[/go]

Application:

Click Here To Show Diagram Code: [go]$$ $$ . . . . . . . . . . . $$ . . . T T O T T . . . $$ . . T T O X O T T . . $$ . . T T T B T T T . . $$ . . . . . . . . . . . $$ --------------------[/go]

If black likes his two stones, then any of the marked triangle points is sente for white. If you make it a move that also threatens something else, two free stones. This can be big: here's a problem. Assume no ladders work for black.

Click Here To Show Diagram Code: [go]$$c Black to split white's two groups $$ ---------------------- $$ . . . . . . . . . . . | $$ . . . . . O . . . . . | $$ . . . . X O . . O . . | $$ . . . . X O O . . . . | $$ . . . . X O X . . . . | $$ . . . . X X . . . . . | $$ . . . . . . . O . . . | $$ . . . . O . . . . . . | $$ . . . . . . . O . . . | $$ . . . . . . . . . . . | $$ . . . . . . . . . . . |[/go]

The following two failed variations are pretty clear:

Click Here To Show Diagram Code: [go]$$c Failure 1 $$ ---------------------- $$ . . . . . . . . . . . | $$ . . . . . O . . . . . | $$ . . . . X O . . O . . | $$ . . . . X O O . . . . | $$ . . . . X O X . 2 . . | $$ . . . . X X 1 . . . . | $$ . . . . . . . O . . . | $$ . . . . O . . . . . . | $$ . . . . . . . O . . . | $$ . . . . . . . . . . . | $$ . . . . . . . . . . . |[/go]

Click Here To Show Diagram Code: [go]$$c Failure 2 $$ ---------------------- $$ . . . . . . . . . . . | $$ . . . . . O . . . . . | $$ . . . . X O . . O . . | $$ . . . . X O O . . . . | $$ . . . . X O X 1 . . . | $$ . . . . X X 2 . . . . | $$ . . . . . . . O . . . | $$ . . . . O . . . . . . | $$ . . . . . . . O . . . | $$ . . . . . . . . . . . | $$ . . . . . . . . . . . |[/go]

What about this? (This is just one more variation. Playing around with all the possibilities in this situation could take forever, so I won't. There probably also isn't one unique answer. This is a useful one for this post only.

)

Click Here To Show Diagram Code: [go]$$c White has some cutting points. Let's see what happens. $$ ---------------------- $$ . . . . . . . . . . . | $$ . . . . . O . . . . . | $$ . . . . X O . . O . . | $$ . . . . X O O . . . . | $$ . . . . X O X 2 . . . | $$ . . . . X X 3 1 4 . . | $$ . . . . . . . O . . . | $$ . . . . O . . . . . . | $$ . . . . . . . O . . . | $$ . . . . . . . . . . . | $$ . . . . . . . . . . . |[/go]

Click Here To Show Diagram Code: [go]$$c Oh hey, it's that new shape I mentioned. $$ ---------------------- $$ . . . . . . . . . . . | $$ . . . . . O . . . . . | $$ . . . . X O . . O . . | $$ . . . . X O O 6 . . . | $$ . . . . X O X O 5 . . | $$ . . . . X X X X O 8 . | $$ . . . . . . . O 7 . . | $$ . . . . O . . . . . . | $$ . . . . . . . O . . . | $$ . . . . . . . . . . . | $$ . . . . . . . . . . . |[/go]

Click Here To Show Diagram Code: [go]$$c The tesuji: a and b are miai. $$ ---------------------- $$ . . . . . . . . . . . | $$ . . . . . O . . . . . | $$ . . . . X O . . O . . | $$ . . . . X O O O . . . | $$ . . . . X O X O X b . | $$ . . . . X X X X O O . | $$ . . . . . . . O X . . | $$ . . . . O . . a 9 . . | $$ . . . . . . . O . . . | $$ . . . . . . . . . . . | $$ . . . . . . . . . . . |[/go]

Some silly cases and caveats:

Click Here To Show Diagram Code: [go]$$c White to play and kill 2 stones $$ . . . . . . . . . . . $$ . . . . . O . . . . . $$ . . . . O X O . . . . $$ . . . . . B . . . . . $$ . . . . O . . . . . . $$ --------------------[/go]

[spoiler]

Click Here To Show Diagram Code: [go]$$c White to play and kill 2 stones $$ . . . . . . . . . . . $$ . . . . . O . . . . . $$ . . . . O X O . . . . $$ . . . . . B . . . O . $$ . . . . . . . . . O . $$ --------------------[/go]

Click Here To Show Diagram Code: [go]$$c White to play and kill 2 stones $$ . . . . . . . . . . . $$ . . . . . . O O . . . $$ . . . . . O . . . . . $$ . . . . O X O . . . . $$ . . . . . B . . . . . $$ . . . . . . . . . . . $$ --------------------[/go]

Click Here To Show Diagram Code: [go]$$c Black to play and escape $$ . . . . . . . . . . . $$ . . . . O . . . . . . $$ . . . . . O X X . . . $$ . . . O O X O O X . . $$ . . . . . . . . . . . $$ . . . . . . . . . . . $$ --------------------[/go]

Click Here To Show Diagram Code: [go]$$c Black to play and escape $$ . . . . . . . . . . . $$ . . . O . . . . . . . $$ . . . . O X X X . . . $$ . . . O X O O O X . . $$ . . . . . . . . . . . $$ . . . . . . . . . . . $$ --------------------[/go]

Click Here To Show Diagram Code: [go]$$c Black to play and escape $$ . . . . . . . . . . . $$ X X . O O . . . . . . $$ . . . . O X X X . . . $$ . . . O X O O O X . . $$ . . . . . . . . . . . $$ . . . . . . . . . . . $$ --------------------[/go]

Also worth a read: add a second stone and sacrifice both.

Phelan · Post by **Phelan** » Mon Jan 28, 2013 5:43 am

Additional material at [sl=ThirdLineCapture]Sensei's[/sl].

Uberdude · Post by **Uberdude** » Mon Jan 28, 2013 5:50 am

billywoods wrote:I'm surprised it's not taught as standard in the same league as nets and snapbacks, because it's a very useful shape to be able to spot instantly.

I teach it as standard to beginners, though later than nets and snapbacks. It's good as a tactical example to explain the strategy of why it's good to start in the corners and sides rather than the centre.

billywoods · Post by **billywoods** » Mon Jan 28, 2013 5:52 am

Phelan wrote:Additional material at [sl=ThirdLineCapture]Sensei's[/sl].

Aha! I looked for it but couldn't find it.

Thanks. Hopefully the discussion is useful anyway!

(Though, if I may say so, like most SL pages I find it mostly very badly written. :-?

)

shapenaji · Post by **shapenaji** » Mon Jan 28, 2013 6:13 am

a problem that emerges:

Click Here To Show Diagram Code: [go]$$c $$ ---------------------- $$ . . . . . . . . . . . | $$ . . . . . O . . . . . | $$ . . . . X O . . O . . | $$ . . . . X O O . . . . | $$ . . . . X O X . . . . | $$ . . . . X X . 1 . 2 . | $$ . . . . . . . O . . . | $$ . . . . O . . . . . . | $$ . . . . . . . O . . . | $$ . . . . . . . . . . . | $$ . . . . . . . . . . . |[/go]

how does black separate?

Charlie · Post by **Charlie** » Mon Jan 28, 2013 7:19 am

Click Here To Show Diagram Code: [go]$$c $$ ---------------------- $$ . . . . . . . . . . . | $$ . . . . . O . . . . . | $$ . . . . X O . . O . . | $$ . . . . X O O . 5 . . | $$ . . . . X O X . 2 1 . | $$ . . . . X X . X 3 O . | $$ . . . . . . . O . 4 . | $$ . . . . O . . . . . . | $$ . . . . . . . O . . . | $$ . . . . . . . . . . . | $$ . . . . . . . . . . . |[/go]

Like this?

shapenaji · Post by **shapenaji** » Mon Jan 28, 2013 7:44 am

ah but then there's this:

Click Here To Show Diagram Code: [go]$$c $$ ---------------------- $$ . . . . . . . . . . . | $$ . . . . . O . . . . . | $$ . . . . X O . . O . . | $$ . . . . X O O . . . . | $$ . . . . X O X 4 2 1 . | $$ . . . . X X . X 3 O . | $$ . . . . . . . O . . . | $$ . . . . O . . . . . . | $$ . . . . . . . O . . . | $$ . . . . . . . . . . . | $$ . . . . . . . . . . . |[/go]

Uberdude · Post by **Uberdude** » Mon Jan 28, 2013 8:13 am

Creating good problems is not easy

. This one has too many possible variations.

billywoods · Post by **billywoods** » Mon Jan 28, 2013 9:12 am

I never promised this was a good problem!

Thanks for the variation, though, shapenaji - but I suspect it'd take me a week to read this problem out fully...

Phelan · Post by **Phelan** » Mon Jan 28, 2013 10:45 am

billywoods wrote:
Phelan wrote:Additional material at [sl=ThirdLineCapture]Sensei's[/sl].

Aha! I looked for it but couldn't find it. Thanks. Hopefully the discussion is useful anyway!

(Though, if I may say so, like most SL pages I find it mostly very badly written. )

You can always improve the page.

Go ahead, it's pretty easy!

Edit: Oh, and I think discussion on these topics is always useful, especially when it's a personalized look at something.

Unusedname · Post by **Unusedname** » Mon Jan 28, 2013 11:58 am

I never knew this...

do you have any other of these things i should know? haha

billywoods · Post by **billywoods** » Mon Jan 28, 2013 12:28 pm

Phelan wrote:You can always improve the page.

Well, while I think the page is badly written, I think it's far from a problem unique to that one page. I find SL really poorly organised, to the extent where one person alone (even one person with a lot of free time and spare motivation on their hands - which I'm not!) couldn't fix it. but that's a discussion for another thread, perhaps.

jts · Post by **jts** » Mon Jan 28, 2013 2:44 pm

billywoods wrote:
Phelan wrote:You can always improve the page.

Well, while I think the page is badly written, I think it's far from a problem unique to that one page. I find SL really poorly organised, to the extent where one person alone (even one person with a lot of free time and spare motivation on their hands - which I'm not!) couldn't fix it. but that's a discussion for another thread, perhaps.

Can you share what you take to be the problem with that page - or with SL pages in general? I've always found SL to be ultra-useful and, for a wiki with so much raw information, very well organized. I read the page on the cathedral when I was 14k or so, and found it very useful at the time.

(I agree that the way the main article blends into the commentary on the article can be a difficult style, especially if you don't know who the main "deshi" are. But it's very honest to the wiki form. On a wikipedia article, the editors are encouraged to write in the Ten Commandments style of an academic reference article, but then when you lift up the stone you see a menagerie of worms and beetles scuttling about in the moist soil of the discussion page. A SL page lays out the obvious first, and then contains a mini-seminar on the more confusing aspects of the topic.)

billywoods · Post by **billywoods** » Mon Jan 28, 2013 9:20 pm

jts wrote:Can you share what you take to be the problem with that page - or with SL pages in general?

Sure:

I couldn't even find the shape that this thread is about. The search function does its best, but if I don't know the name of the shape, and it doesn't happen to be indexed on a page I can find easily (both of which are common), the information is lost in the void.
Here is an example game linked to early on the beginners' study page. It uses language incorrectly ("captures" to mean "puts into a situation where capture is unavoidable"), has confusing grammar (white changes from male to female even within the same sentence - "if he plays in her own area"), and rambles on about two scoring systems (when the main point to a beginner should be "pick one, it doesn't matter"). I think this page is great, by the way.
Here is the link that Phelan gave me. At the start of the page, it notes that the shape made is sometimes called a "cathedral", and posts three diagrams of some stones getting squashed against the edge in the sort of detail that a 25k would appreciate. Then the dan players charge in and start a high-level discussion immediately after, which no 25k will be able to follow and no 25k will necessarily realise is not intended for them. A telling quote, 80% of the way down the page: "Both before and after reading this page, I confess I have no idea what cathedral is."
Here is the page of beginner exercises. I might try them myself later. They're too hard.
Here is the page on vital points, linked to from the beginners' page. I don't think this page explains anything very well: it doesn't explain how to find vital points, or list common ones, it just jumps straight into some pro games. Anyway, enough beginners' pages, because I could list those forever...
Here is a bad page about honte. It gives a washy definition, a single example, and then a whole stream of discussion - in this case mostly about translation from Japanese, not about go. It's interesting, but completely unsuitable for someone learning for the first time what honte is. Here is a page about a common shape which was marked as "urgently" needing "wiki master editing" in June 2009.
Here is an unnecessary and badly laid out page; here is a similarly badly laid out page but which could potentially be useful; here, more of the same; this one is okay; this is far better. They're all saying the same thing.
For comparison, and to show it's not all doom and gloom, here is a (fantastic) page on common corner shapes, and all of the pages linked to from there that I checked seem good too.

I have deliberately avoided very short pages, pages about books (which are sometimes even reviewed by their own authors), pages about users, deliberate discussion pages and non-serious pages. There are lots of these - probably more of these than about go itself - and while I don't object to their existence, they're almost all useless, and are not where effort should be spent. I've also avoided pages about very uncommon shapes or plays because they are bound to be short and badly written.

Here is an old L19 thread about it. Here is an unreadable SL discussion page about it.

jts · Post by **jts** » Mon Jan 28, 2013 10:13 pm

Okay, thanks for the examples. Some of those pages you linked to seem perfectly good. The pages on honte and vital point give a definition, rather than a study plan, because these are not concepts beginners will understand after 15 minutes on Sensei's Library (as opposed to eyeshape and nakade, which a sharp beginner might well master from a single page). "4463 enclosure with 34 contact move" shows a number of variations with a few comments - what more do you want? I don't want to delete half of the branches, do you? Other pages aren't very good examples of problems with SL - if Robert Jasiek goes around assimilating various pages to the borg, well, RJ is a problem for the go community as a whole, not Sensei's Library specifically. But let's try to improve the others.

I think it's kind of awe-inspiring that you can find a heavily-commented, 9x9 beginner game on sensei's library. Everyone whom I've ever met in the Go world uses "captured" to mean "put in a situation where capture is unavoidable." I'm not sure why you're so down on such a helpful page. Have you ever read a commentary on a professional game? Inevitably when, during the end game, one player "puts stones in a situation where capture is unavoidable", the commentary will talk about capturing stones. But the beautiful thing about a wiki is that you can change problems you observe. I have removed the one use of "her" on the page.

I simply don't believe that beginner exercise 1 is too hard for you. (Although perhaps this is why you find the eyeshape pages confusing?

) There are at least two hundred excellent problems there. When I was a beginner I think I tried all three hundred. It's very obvious that the problems are getting harder and murkier as you go through them, and beginners can take that in stride. I agree that the SL editors went a little wild adding in-game problems from amateur dan games - the page would be more elegant if it were restricted to the thematic unity of the first 250 problems. On the other hand, having an opportunity to try my hand at some challenging, creative problems after doing the didactic ones didn't hurt me - on the contrary, I think it help show me how tactically fascinating Go is. Anyway. Options: (i) Leave "Beginner Exercises" as is. (ii) Delete the last 50-100 problems. (iii) Move the last 50-100 problems to a separate section on the same page, to make sure there is no confusion. -- Does anyone have strong objections to any of those three changes?

Life In 19x19

A useful, easy shape: atari on 3rd line

A useful, easy shape: atari on 3rd line

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Re: A useful, easy shape: atari on 3rd line

Re: A useful, easy shape: atari on 3rd line

Re: A useful, easy shape: atari on 3rd line

Re: A useful, easy shape: atari on 3rd line

Re: A useful, easy shape: atari on 3rd line

Re: A useful, easy shape: atari on 3rd line

Re: A useful, easy shape: atari on 3rd line

Re: A useful, easy shape: atari on 3rd line

Re: A useful, easy shape: atari on 3rd line

Re: A useful, easy shape: atari on 3rd line

Re: A useful, easy shape: atari on 3rd line

Re: A useful, easy shape: atari on 3rd line

Re: A useful, easy shape: atari on 3rd line