Hi guys,

In this problem it is black to play in order to connect his group up.



The solution by the book (lee chang ho tesuji vol 3)
is :



Howhever... someone from our go club sugested to start with D3.
This way black does not need to sacrifice two stones and is also connected.
I tried to refute this with F3 but then there is E5.

Is there a refutation for D3 or is the answer in the book wrong ?

Thanks!
Otenki

Looks to me like this works as a refutation for that

How about if the reply is e2 ? (note that 6 cannot be played at f1)
eg:

Click Here To Show Diagram Code

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

That's true. Brain decided to not work for a moment while I read that sequence it seems. Back to thinking about other options then.

Click Here To Show Diagram Code

[go]$$Bc
$$ - . . . . . . .
$$ - . . X . . . .
$$ - . . . . . . .
$$ - . . X . . O .
$$ - . . X O . O .
$$ - . . . . O . X
$$ - . . X 4 3 . X
$$ - . . X O . 2 X
$$ - . . X 1 O 5 X
$$ - . . . . 6 O X
$$ - . . . . . . X
$$ ----------------[/go]

Click Here To Show Diagram Code

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

Click Here To Show Diagram Code

[go]$$Bc
$$ - . . . . . . .
$$ - . . X . . . .
$$ - . . . . . . .
$$ - . . X . . O .
$$ - . . X O . O .
$$ - . . . . O . X
$$ - . . X 5 6 . X
$$ - . . X O . 2 X
$$ - . . X 1 O 3 X
$$ - . . . . 4 O X
$$ - . . . . . . X
$$ ----------------[/go]

So, the result seems like ko. Did I miss anything?

_________________
Still officially AGA 5d but I play so irregularly these days that I am probably only 3d or 4d over the board (but hopefully still 5d in terms of knowledge, theory and the ability to contribute).

How about:

Click Here To Show Diagram Code

[go]$$Bc
$$ - . . . . . . .
$$ - . . X . . . .
$$ - . . . . . . .
$$ - . . X . . O .
$$ - . . X O . O .
$$ - . . . . O . X
$$ - . . X . . . X
$$ - . . X O . 2 X
$$ - . . X 1 O . X
$$ - . . . . 3 O X
$$ - . . . . . . X
$$ ----------------[/go]

Ha! I forgot the obvious! I was just looking at the comment "what about E5?"

_________________
Still officially AGA 5d but I play so irregularly these days that I am probably only 3d or 4d over the board (but hopefully still 5d in terms of knowledge, theory and the ability to contribute).

In your last variation, I would play one point below:

Click Here To Show Diagram Code

[go]$$Bc
$$ - . . . . . . .
$$ - . . X . . . .
$$ - . . . . . . .
$$ - . . X . . O .
$$ - . . X O . O .
$$ - . . . . O . X
$$ - . . X . . . X
$$ - . . X Q 5 6 X
$$ - . . X 1 O 2 X
$$ - . . . . 3 O X
$$ - . . . . . 4 X
$$ ----------------[/go]

IMHO black can capture the marked stone but not connect.

EDIT: Does not work because of on E5

D3 is my first instinct, and I can find no refutation. Either E2 or E5 will work, depending on how white plays.

The book solution also solves the problem in that it connects, but otherwise seems inferior.

I feel that D3 is probably better, for the obvious reason that it doesn't give two stones. However, there are more complicated considerations than just connecting.

I still suspect D3 was better, but here were my initial thoughts...


If black plays D3, white can play like this:

Click Here To Show Diagram Code

[go]$$Bc
$$ - . . . . . . .
$$ - . . X . . . .
$$ - . . . . . . .
$$ - . . X . . O .
$$ - . . X O . O .
$$ - . . . . O . X
$$ - C C X . . . X
$$ - C C X O 2 . X
$$ - C C X 1 O 4 X
$$ - C C C . 3 O X
$$ - C C C C . 5 X
$$ ----------------[/go]

Now white can tenuki - black got some points, but there aren't a ton of points. If you count the marked intersections, that's 13 points. Now, white has sente.

If black plays as in the book and white does tenuki, then black can play here, and get many more points:

Click Here To Show Diagram Code

[go]$$Bc
$$ - . . . . . . .
$$ - . . X . . . .
$$ - . . . . . . .
$$ - . . X . . O .
$$ - . . X O . O .
$$ - . . . . O . X
$$ - . . X . 3 . X
$$ - . . X O 1 . X
$$ - . . X . O . X
$$ - . . . . . O X
$$ - . . . . . . X
$$ ----------------[/go]

So I figured, the book solution was more sente than D3. But this logic doesn't hold, because as shown in the book variation, white can keep playing forcing moves to force black to connect:

Click Here To Show Diagram Code

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

After this, white still gets sente, and has more points.

So if we consider just the single move, D3 or E5, I feel that E5 is more of a sente move - white would be more inclined to answer it immediately if it's played. But if black really wants to connect these stones, the end position sequence in the book is worse for black than the end position I gave above where white gets sente.

So... I think D3 is better.

_________________
be immersed

To me this sounds funny. If B can afford to tenuki after starting the sequence he shouldn't have started it. I guess.

_________________
I think I am so I think I am.

Totally nonsense or essentially correct?

_________________
I think I am so I think I am.