How did you solve this problem?

dfan · Post by **dfan** » Thu May 10, 2018 7:48 am

I am trying to move more carefully-explore-the-tree reading into instinctive knowledge, and your answers to this question would be helpful in figuring out how to do so. Please keep answers in hide tags (at least for now) so other people aren't spoiled.

This is generally the first problem in any standard easy-life-and-death problem set for which I have to carefully read and explore the tree, as opposed to a few-second "this move must be right; verify; yep" process. Please solve it yourself now before continuing!

Click Here To Show Diagram Code: [go]$$B Black to play and live $$ | . . . . . . . . . . $$ | . . O . . . . . . . $$ | . . . O O . . . O . $$ | . O O X X O O . . , $$ | . O X . X . X O . . $$ | . O X . . . X O . . $$ | . . . . . . . . . . $$ +---------------------[/go]

Solution:

My question for you is: if you solved this problem "on sight", as I do for problems that seem to be considered of similar difficulty, how did you do it? Sample choices:

Bill Spight · Post by **Bill Spight** » Thu May 10, 2018 9:38 am

I did not solve it on sight. The first move that leaped out at me was wrong.

Click Here To Show Diagram Code: [go]$$B What I saw $$ | . . . . . . . . . . $$ | . . O . . . . . . . $$ | . . . O O . . . O . $$ | . O O X X O O . . , $$ | . O X . X . X O . . $$ | . O X . . . X O . . $$ | . . . . 1 . . . . . $$ +---------------------[/go]

BTW, this is the move that would have leaped out at me when I was a raw beginner. It is not actually so bad.

Click Here To Show Diagram Code: [go]$$B First attempt, seki $$ | . . . . . . . . . . $$ | . . O . . . . . . . $$ | . . . O O . . . O . $$ | . O O X X O O . . , $$ | . O X . X 5 X O . . $$ | . O X 2 6 4 X O . . $$ | . . . 3 1 . 7 . . . $$ +---------------------[/go]

is kind of stupid.

at 5 is much more sensible.

Click Here To Show Diagram Code: [go]$$B First attempt, death $$ | . . . . . . . . . . $$ | . . O . . . . . . . $$ | . . . O O . . . O . $$ | . O O X X O O . . , $$ | . O X . X 4 X O . . $$ | . O X 2 . 5 X O . . $$ | . . . 3 1 . 6 . . . $$ +---------------------[/go]

Click Here To Show Diagram Code: [go]$$B Second try $$ | . . . . . . . . . . $$ | . . O . . . . . . . $$ | . . . O O . . . O . $$ | . O O X X O O . . , $$ | . O X . X . X O . . $$ | . O X 1 . 3 X O . . $$ | . . . . 2 . . . . . $$ +---------------------[/go]

Same points, but switching the order of play.

Click Here To Show Diagram Code: [go]$$B Variation $$ | . . . . . . . . . . $$ | . . O . . . . . . . $$ | . . . O O . . . O . $$ | . O O X X O O . . , $$ | . O X . X 3 X O . . $$ | . O X 1 . 2 X O . . $$ | . . 7 . 5 6 4 . . . $$ +---------------------[/go]

Bingo!

Note: Not switching

and

in the previous diagram, but preventing the connection at 3 first. Zwischenzug.

----
Analysis (with thanks to Znosko-Borovsky):

General comment: Life and death problems are mainly about single point eyes and damezumari. Why single point eyes? Because space is constrained.

Click Here To Show Diagram Code: [go]$$B Candidate eyes $$ | . . . . . . . . . . $$ | . . O . . . . . . . $$ | . . . O O . . . O . $$ | . O O X X O O . . , $$ | . O X C X . X O . . $$ | . O X . C . X O . . $$ | . . . C . C . . . . $$ +---------------------[/go]

The first thing to do is to identify the likely one point eyes. This position has four of them.

Click Here To Show Diagram Code: [go]$$B First seen $$ | . . . . . . . . . . $$ | . . O . . . . . . . $$ | . . . O O . . . O . $$ | . O O X X O O . . , $$ | . O X C X . X O . . $$ | . O X . C . X O . . $$ | . . . C 1 C . . . . $$ +---------------------[/go]

The move that leapt out at me is not too bad, because it potentially helps to form three one point eyes.

Click Here To Show Diagram Code: [go]$$B Solution, first move $$ | . . . . . . . . . . $$ | . . O . . . . . . . $$ | . . . O O . . . O . $$ | . O O X X O O . . , $$ | . O X S X . X O . . $$ | . O X 1 C . X O . . $$ | . . . C . C . . . . $$ +---------------------[/go]

But why isn't

obvious? It actually forms a one point eye, and in addition potentially helps to form two more.

Click Here To Show Diagram Code: [go]$$B Solution, var. 1 $$ | . . . . . . . . . . $$ | . . O . . . . . . . $$ | . . . O O . . . O . $$ | . O O X X O O . . , $$ | . O X . X . X O . . $$ | . O X 1 C 3 X O . . $$ | . . . C 2 C . . . . $$ +---------------------[/go]

destroys potential three one point eyes, because if any of them becomes an eye, it will have to include

. Unfortunately for White,

encloses

for the second eye.

Click Here To Show Diagram Code: [go]$$B Solution, var. 2 $$ | . . . . . . . . . . $$ | . . O . . . . . . . $$ | . . . O O . . . O . $$ | . O O X X O O . . , $$ | . O X . X 3 X O . . $$ | . O X 1 a 2 X O . . $$ | . . 7 . 5 6 4 . . . $$ +---------------------[/go]

destroys two potential one point eyes and manages to escape, but

and

form a second one point eye. Because of damezumari White cannot now play at "a".

Again, why isn't

obvious? It forms a one point eye.

Knotwilg · Post by **Knotwilg** » Thu May 10, 2018 9:58 am

I can tell you how my systematic approach works:

1. Increase/decrease the eyespace for living/killing
2. Usually this will reveal the vital point, when one color decisively lives or kills by playing there

In your example:

Click Here To Show Diagram Code: [go]$$B Increasing and decreasing eye space $$ | . . . . . . . . . . $$ | . . O . . . . . . . $$ | . . . O O . . . O . $$ | . O O X X O O . . , $$ | . O X . X 1 X O . . $$ | . O X 4 a . X O . . $$ | . . 2 3 . . . . . . $$ +---------------------[/go]

B1 increases, W2 decreases, B3 increases, W4 cuts (and next A will create a killing shape)
We already see W4 as a likely candidate

Click Here To Show Diagram Code: [go]$$B Vital point at 3? $$ | . . . . . . . . . . $$ | . . O . . . . . . . $$ | . . . O O . . . O . $$ | . O O X X O O . . , $$ | . O X . X 1 X O . . $$ | . O X 3 . . X O . . $$ | . . 2 5 4 a 6 . . . $$ +---------------------[/go]

So What if B3 plays there? Then Bill's point comes to the surface: W4. After W6 Black can not throw in at A because this will create shortage of liberties for himself

Click Here To Show Diagram Code: [go]$$B Different way of increasing $$ | . . . . . . . . . . $$ | . . O . . . . . . . $$ | . . . O O . . . O . $$ | . O O X X O O . . , $$ | . O X . X 2 X O . . $$ | . O X . 4 3 X O . . $$ | . . 1 . . . . . . $$ +---------------------[/go]

In previous diagrams, the hane was lethal, so what if Black increases his eyespace there? White will break through at W2 and next W4 is atari.

Click Here To Show Diagram Code: [go]$$B Increasing and decreasing eye space $$ | . . . . . . . . . . $$ | . . O . . . . . . . $$ | . . . O O . . . O . $$ | . O O X X O O . . , $$ | . O X . X a X O . . $$ | . O X 1 . . X O . . $$ | . . . . . . . . . . $$ +---------------------[/go]

Back to our suspect: B1 as the vital point. As we can see, it also protects against the cut at A. So this is our solution

How I "see" it, which I actually did, I think I instantly see the last diagram in the above hidden box. I do not see the 2nd of those diagrams and I usually don't check, because even if that would work too, the solution leaves less aji.

Edit: continuing with the systematic approach.

Click Here To Show Diagram Code: [go]$$B Increasing and decreasing eye space $$ | . . . . . . . . . . $$ | . . O . . . . . . . $$ | . . . O O . . . O . $$ | . O O X X O O . . , $$ | . O X . X 2 X O . . $$ | . O X 1 . 3 X O . . $$ | . . . . . . . . . . $$ +---------------------[/go]

As said, B3 is the obvious answer, if W2 again decreases the space.

Click Here To Show Diagram Code: [go]$$B Increasing and decreasing eye space $$ | . . . . . . . . . . $$ | . . O . . . . . . . $$ | . . . O O . . . O . $$ | . O O X X O O . . , $$ | . O X . X . X O . . $$ | . O X 1 . 3 X O . . $$ | . . . . . . 2 . . . $$ +---------------------[/go]

The same point is the answer if W2 decreases the eyespace from the other side.

Click Here To Show Diagram Code: [go]$$B Increasing and decreasing eye space $$ | . . . . . . . . . . $$ | . . O . . . . . . . $$ | . . . O O . . . O . $$ | . O O X X O O . . , $$ | . O X . X 3 X O . . $$ | . O X 1 . 2 X O . . $$ | . . . . . . 4 . . . $$ +---------------------[/go]

This makes W2 a tempting point for White to try and kill the black group. After connecting with W4, she seems to succeed.

Click Here To Show Diagram Code: [go]$$B Increasing and decreasing eye space $$ | . . . . . . . . . . $$ | . . O . . . . . . . $$ | . . . O O . . . O . $$ | . O O X X O O . . , $$ | . O X . X 3 X O . . $$ | . O X 1 . 2 X O . . $$ | . . b . 5 a 4 C . . $$ +---------------------[/go]

This is where the stylish but not so obvious B5 comes into play: it makes miai of a and b to live, using the shortage of liberties for White due to the circled point being empty and White's stones not being firmly connected.

dfan · Post by **dfan** » Thu May 10, 2018 10:16 am

Many thanks already to Bill and Knotwilg for their generosity of time and diagrams

Bill:

Knotwilg:

Knotwilg · Post by **Knotwilg** » Thu May 10, 2018 10:39 am

BTW, here is the same approach with the first problem in the hitachi series

Click Here To Show Diagram Code: [go]$$B Hitachi number 1 $$---------------------------- $$| . . . . . . . . . . . . . $$| . . O X X . . . . . . . . $$| . . O O O X . . . . . . . $$| O . O . . X . . . . . . . $$| . O X . X . . . . . . . . $$| X O X . . . . . . . . . . $$| . X . . . . . . . . . . . $$| . . X . . . . . . . . . . $$| . . . . . . . . . . . . . $$| . . . . . . . . . . . . . $$| . . . . . . . . . . . . .[/go]

Click Here To Show Diagram Code: [go]$$B Hitachi number 1 $$---------------------------- $$| . 2 1 a . . . . . . . . . $$| C . O X X b . . . . . . . $$| . . O O O X . . . . . . . $$| O . O . . X . . . . . . . $$| . O X . X . . . . . . . . $$| X O X . . . . . . . . . . $$| . X . . . . . . . . . . . $$| . . X . . . . . . . . . . $$| . . . . . . . . . . . . . $$| . . . . . . . . . . . . . $$| . . . . . . . . . . . . .[/go]

The decrease/increase exchange of 1-2 instantly reveals the marked vital point. We also see that White A provokes Black B

Click Here To Show Diagram Code: [go]$$B Hitachi number 1 $$---------------------------- $$| . 2 1 4 . . . . . . . . . $$| 6 3 O X X 5 . . . . . . . $$| . . O O O X . . . . . . . $$| O . O . . X . . . . . . . $$| . O X . X . . . . . . . . $$| X O X . . . . . . . . . . $$| . X . . . . . . . . . . . $$| . . X . . . . . . . . . . $$| . . . . . . . . . . . . . $$| . . . . . . . . . . . . . $$| . . . . . . . . . . . . .[/go]

For example, Black has no time to cut, because of the danger 4 represents. Next White plays the vital point.

Click Here To Show Diagram Code: [go]$$B Hitachi number 1 $$---------------------------- $$| . 2 1 4 . . . . . . . . . $$| 3 a O X X 5 . . . . . . . $$| b c O O O X . . . . . . . $$| O . O . . X . . . . . . . $$| . O X . X . . . . . . . . $$| X O X . . . . . . . . . . $$| C X . . . . . . . . . . . $$| . . X . . . . . . . . . . $$| . . . . . . . . . . . . . $$| . . . . . . . . . . . . . $$| . . . . . . . . . . . . .[/go]

Let's play B3 and remove the complexity of 4-5
This reduces the problem to its canonical form: can White live? Candidates are a/b/c but in all cases, the surprisingly effective move Black has at the marked spot, does the trick.

Click Here To Show Diagram Code: [go]$$B Hitachi number 1 $$---------------------------- $$| 8 . a 2 . . . . . . . . . $$| 1 4 O X X 3 . . . . . . . $$| 6 . O O O X . . . . . . . $$| O 7 O . . X . . . . . . . $$| b O X . X . . . . . . . . $$| X O X . . . . . . . . . . $$| 5 X . . . . . . . . . . . $$| . . X . . . . . . . . . . $$| . . . . . . . . . . . . . $$| . . . . . . . . . . . . . $$| . . . . . . . . . . . . .[/go]

If Black goes after the vital point immediately, we get this. Black should start with the hane, reducing the eyespace first, before moving into the vital point.

As the proverb says: "there is death in the hane".

Bill Spight · Post by **Bill Spight** » Thu May 10, 2018 11:03 am

dfan wrote:Many thanks already to Bill and Knotwilg for their generosity of time and diagrams

Bill:
my instinct is that White will clamp in response, and there goes my second eye. One reason I am asking people here is that I'm curious how clear it is to people right away that White's clamp won't work after .

Knotwilg:
Your systematic approach is very much like what In-Seong Hwang recommends (unsurprisingly); instead of being tricky right away, try the simplest move first, and if it doesn't work, refute your opponent's refutation (often by playing in the same spot).

dfan · Post by **dfan** » Thu May 10, 2018 11:21 am

Bill:

Ian Butler · Post by **Ian Butler** » Thu May 10, 2018 11:47 am

dfan wrote:Bill:
$$B dfan's solution
$$ | . . . . . . . . . .
$$ | . . O . . . . . . .
$$ | . . . O O . . . O .
$$ | . O O X X O O . . ,
$$ | . O X . X 3 X O . .
$$ | . O X 1 5 2 X O . .
$$ | . . 9 . 7 6 4 8 . .
$$ +---------------------
Click Here To Show Diagram Code
[go]$$B dfan's solution $$ | . . . . . . . . . . $$ | . . O . . . . . . . $$ | . . . O O . . . O . $$ | . O O X X O O . . , $$ | . O X . X 3 X O . . $$ | . O X 1 5 2 X O . . $$ | . . 9 . 7 6 4 8 . . $$ +---------------------[/go]

$$B Bill's solution
$$ | . . . . . . . . . .
$$ | . . O . . . . . . .
$$ | . . . O O . . . O .
$$ | . O O X X O O . . ,
$$ | . O X . X 3 X O . .
$$ | . O X 1 . 2 X O . .
$$ | . . 7 . 5 6 4 . . .
$$ +---------------------
Click Here To Show Diagram Code
[go]$$B Bill's solution $$ | . . . . . . . . . . $$ | . . O . . . . . . . $$ | . . . O O . . . O . $$ | . O O X X O O . . , $$ | . O X . X 3 X O . . $$ | . O X 1 . 2 X O . . $$ | . . 7 . 5 6 4 . . . $$ +---------------------[/go]
Speaking of that kosumi, why did you choose it over the atari? Compared to my line, Black now does have a small ko threat, but White has a big ko threat. I'm trying to figure out what Black gains from holding the last exchange in reserve. Do you want to keep the possibility of the throw-in (where my is)? I could have thrown in there first with my , but maybe we don't know yet whether it's a good idea. Or do you just not want to play forcing moves that you don't have to?

dfan · Post by **dfan** » Thu May 10, 2018 12:28 pm

Ian Butler wrote:
dfan wrote:Bill:
$$B dfan's solution
$$ | . . . . . . . . . .
$$ | . . O . . . . . . .
$$ | . . . O O . . . O .
$$ | . O O X X O O . . ,
$$ | . O X . X 3 X O . .
$$ | . O X 1 5 2 X O . .
$$ | . . 9 . 7 6 4 8 . .
$$ +---------------------
Click Here To Show Diagram Code
[go]$$B dfan's solution $$ | . . . . . . . . . . $$ | . . O . . . . . . . $$ | . . . O O . . . O . $$ | . O O X X O O . . , $$ | . O X . X 3 X O . . $$ | . O X 1 5 2 X O . . $$ | . . 9 . 7 6 4 8 . . $$ +---------------------[/go]
Can't white make a ko with the atari instead of the cosumi by playing your variation's 7?

Bill Spight · Post by **Bill Spight** » Thu May 10, 2018 12:52 pm

dfan wrote:Bill:
$$B dfan's solution
$$ | . . . . . . . . . .
$$ | . . O . . . . . . .
$$ | . . . O O . . . O .
$$ | . O O X X O O . . ,
$$ | . O X . X 3 X O . .
$$ | . O X 1 5 2 X O . .
$$ | . . 9 . 7 6 4 8 . .
$$ +---------------------
Click Here To Show Diagram Code
[go]$$B dfan's solution $$ | . . . . . . . . . . $$ | . . O . . . . . . . $$ | . . . O O . . . O . $$ | . O O X X O O . . , $$ | . O X . X 3 X O . . $$ | . O X 1 5 2 X O . . $$ | . . 9 . 7 6 4 8 . . $$ +---------------------[/go]

$$B Bill's solution
$$ | . . . . . . . . . .
$$ | . . O . . . . . . .
$$ | . . . O O . . . O .
$$ | . O O X X O O . . ,
$$ | . O X . X 3 X O . .
$$ | . O X 1 . 2 X O . .
$$ | . . 7 . 5 6 4 . . .
$$ +---------------------
Click Here To Show Diagram Code
[go]$$B Bill's solution $$ | . . . . . . . . . . $$ | . . O . . . . . . . $$ | . . . O O . . . O . $$ | . O O X X O O . . , $$ | . O X . X 3 X O . . $$ | . O X 1 . 2 X O . . $$ | . . 7 . 5 6 4 . . . $$ +---------------------[/go]
Speaking of that kosumi, why did you choose it over the atari?
It is the vital point. In your line Black has enough liberties to avoid ko; in my line the question does not arise.

Compared to my line, Black now does have a small ko threat, but White has a big ko threat. I'm trying to figure out what Black gains from holding the last exchange in reserve.
Sans ko, the two results are equivalent. In a real game Black should almost certainly transpose from my line to yours with .

My reply is embedded.

swannod · Post by **swannod** » Thu May 10, 2018 12:58 pm

dfan wrote:I am trying to move more carefully-explore-the-tree reading into instinctive knowledge, and your answers to this question would be helpful in figuring out how to do so. Please keep answers in hide tags (at least for now) so other people aren't spoiled.

At least in my own practice I've decided being able to read quickly and accurately is more useful. Even if you believe you've found the only move, being able to quickly verify seems essential to me as these kinds of situations can make or break a game.

Pio2001 · Post by **Pio2001** » Thu May 10, 2018 2:21 pm

Hi Dfan,

EdLee · Post by **EdLee** » Thu May 10, 2018 3:25 pm

Hi Dan,

Gomoto · Post by **Gomoto** » Thu May 10, 2018 4:41 pm

Intuitivly I checked the correct move in the first the place, but I dismissed it immediatly, while still in the intuitive phase.

I returned to the correct move during reading (Which I always do after selecting candidate moves intuitivly)
and realized it is indeed the solution.

I recommend playing lots of games and review them carefully. Much more fun than doing problems for me. (Although I do problems regulary on my phone when I have some time at my hand during the day.)

I improved my intuition for shortage of liberties and squeezing situations (among other tactical aspects) a lot after I encountered them again and again as missed opportunities during my self reviews.

Intuition is important, but dont pray and play. Intuition has always be to backed up by reading! It is a trap to play strictly intuitive that will hold you back.

(The key to better play is not to substitute careful reading with intuition. The key is the combination of better and faster reading with better and faster intuition. Stick to haengma and never play creative(=bare intuitive) moves by the way

)

(When I play weaker opponents they frequently make moves I whould shrug off at first sight (wrong place or wrong timing), this is the place for intuition, to sort out the clear mistakes)

Kirby · Post by **Kirby** » Thu May 10, 2018 6:02 pm

Choice #3.

Since I knew it was a problem, I knew that getting an eye would be one way to live. I recognize the shape to see that your white 2 doesn't work.

What wasn't immediate was whether that way was the ONLY way to live. There are two other first moves that looked to have a chance of working, but it wasn't clear since they didn't produce a "clean" eye.

In a real game, I don't know it's a problem so it's slightly harder.

Life In 19x19

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