Life In 19x19

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

Black to play and live.

Normally when I first see a tsumego I can pick out the important features and key points, but this one left me a little lost. Instinctively, A and B looked interesting and good candidates, but I couldn't read either one to a successful conclusion. Even seeing the answer didn't make it much clearer.

If you were able to solve this without reading all the points by trial and error, what were the features in the stones that lead you to the solution?

Solution:

what were the features in the stones that lead you to the solution?

Recognizing this shape:

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[go]$$B
$$ ----------+
$$ . . . . . |
$$ . . O O . |
$$ . . O X . |
$$ . O . X . |
$$ . O X . a |
$$ . O . X . |
$$ . . O X . |
$$ . . O O . |
$$ . . . . . |[/go]

and knowing that since white has to respond at a, this is an eye in sente. To see the second eye in gote is then trivial.


In general, you want to search for forcing moves in tsumegos and reduce the shape to an easier tsumego you already know well.

I suspect I'm coming up with post hoc explanations but here goes
1. Can I make two eyes - no
2. Can I find a move that divides the available space into two parts - yes
3. Is it forcing? Yes white only has 1 move or I will live
4. Do I have a second move that could make two eyes - no
5. Do I have a 2nd move that will divide the space into 2 (or more) parts? Yes
6. Is it forcing? No there are several responses
7. Can I make two eyes with all responses? Yes

Also there was a bit of - "ouch I wouldn't want white to play there" and "gee that looks almost like a couple of living shapes I know". Plus I find it helpful to remember that with tsumego the goal is frequently live! or kill! (Unlike a game where "live - sure but also try to get the most points because you will probably be ok" is more often the goal).

I have talked about the importance of the diagonal relationship before with regard to making eyes. Before, I focused on the diagonal relationship of stones, but now let me talk about the diagonal relationship of potential one point eyes. (Why one point eyes? Because to make two eyes in a small space almost always means that one or both eyes are one point eyes.)

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

Here are two potential one point eyes that are diagonally related. To make them Black has to play at both "a" and "b". Not possible.

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

Here are four potential one point eyes that are diagonally related. "a" and "b" are each adjacent to three potential eyes, and thus are good candidates for . And for as well.

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[go]$$B Attempt #1
$$ --------------+
$$ . . . . . . . |
$$ . . . . . . . |
$$ . . . . O O . |
$$ . . . , O X 3 |
$$ . . . O . X . |
$$ . . . O X . 1 |
$$ . . O 5 4 2 . |
$$ . . O X X X 6 |
$$ . . . O O O . |
$$ . . . , . . . |
$$ . . . . . . . |[/go]

After , makes an eye, but after Black cannot play successfully because of damezumari.

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[go]$$B Attempt #2
$$ --------------+
$$ . . . . . . . |
$$ . . . . . . . |
$$ . . . . O O . |
$$ . . . , O X . |
$$ . . . O . X . |
$$ . . . O X . 2 |
$$ . . O 3 . 1 . |
$$ . . O X X X . |
$$ . . . O O O . |
$$ . . . , . . . |
$$ . . . . . . . |[/go]

Bingo!

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[go]$$B Variation
$$ --------------+
$$ . . . . . . . |
$$ . . . . . . . |
$$ . . . . O O . |
$$ . . . , O X . |
$$ . . . O . X . |
$$ . . . O X . 3 |
$$ . . O 2 . 1 . |
$$ . . O X X X . |
$$ . . . O O O . |
$$ . . . , . . . |
$$ . . . . . . . |[/go]

Done!

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[go]$$B Two eyes
$$ --------------+
$$ . . . . . . . |
$$ . . . . . . . |
$$ . . . . O O . |
$$ . . . , O X . |
$$ . . . O . X b |
$$ . . . O X b b |
$$ . . O . a 1 b |
$$ . . O X X X . |
$$ . . . O O O . |
$$ . . . , . . . |
$$ . . . . . . . |[/go]

BTW, after Black has two eyes, 1/2 eye at "a" and 1 1/2 eyes at "b". If you know that you do not have to read any further than .

Thank you, Bill. I have read about a few different approaches to life and death, but never anything like that.

PeterPeter wrote:Thank you, Bill. I have read about a few different approaches to life and death, but never anything like that.

How soon we forget. viewtopic.php?f=11&t=8029

Quite right. The perils of being a very casual player. Well, I hope the tsumego I am tackling have got a bit more difficult since those days.

The really interesting new bit was the concept of a half-eye, and how you can add them together to get 2 eyes.

PeterPeter wrote:The really interesting new bit was the concept of a half-eye, and how you can add them together to get 2 eyes.

You might be interested in this paper by Howard Landman, "Eyespace values in go". http://library.msri.org/books/Book29/files/landman.pdf

This probably isn't the most helpful, but the correct answer just pops out to me after looking for 15 seconds or so, and then I look at it to read and verify. In this case, seeing what leichtloeslich mentioned with the common unsettled group plus the miai for an eye on the outside is how I confirm it.

To get the answer candidate to pop out, I think the only answer is experience. You have trouble with this one, so you saw the answer. Maybe the next one like it too. But after 5 or 10, you see it in a game and after a few seconds you can't keep from looking at that one intersection that works.

I saw the points a and b as miai for 2 eyes if I played the answer.