Cutting point in 3-3 invasion joseki

PeterPeter · #1

A position from the interesting Malkovich game #158:

Click Here To Show Diagram Code: [go]$$Bcm11 W:0 B:0 $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . O . . . . . . . . . . . X . . . . | $$ | . . . , . . . . . , . . . . . , X . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . . , O . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . O O . | $$ | . . X . . . . . . . . . . . . b O X . | $$ | . . . , . . . . . , . . . . . O X . X | $$ | . . . X . . . . . O . . . 0 a O X . . | $$ | . . . . . . . . . . . . . . O X 9 . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

Probably a basic question, but why was :w20:

played here? Couldn't White play elsewhere, then if Black cut at A, trap him in an inescapable ladder by then playing that move? Why is cutting point A more important than cutting point B?

PeterPeter · #2

Don't worry, I have just seen it: Black can escape from the ladder by capturing the 2 Black stones!

EdLee · #3

Peter, first of all, :b15:

(T4) was a mistake, and not joseki.
The result is too good for W -- so don't learn this as a 'joseki'.
Second, could you show your sequence if B cuts at (b)?
This will answer your last question why W fixed (a) but not (b).

PeterPeter · #4

EdLee wrote:

Peter, first of all, :b15:

(T4) was a mistake, and not joseki.

That move looked odd to me, but I was giving the player (who is much stronger than I am) the benefit of the doubt. Thanks for pointing out something that I should NOT try to learn from.

EdLee wrote:

Second, could you show your sequence if B cuts at (b)?
(This will answer your question why W fixed the cut at (a) but not at (b)).

I think I have answered my own question: Black can escape from a ladder at A, but not from one at B?

EdLee · #5

PeterPeter wrote:

Black can escape from a ladder at A, but not from one at B?

It sounds like you figured out what happens if B cuts at (a).
Now please show us (and other beginners) the sequence you figured out if B cuts at (b).

PeterPeter · #6

Click Here To Show Diagram Code: [go]$$Bcm19 W:0 B:0 $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . O . . . . . . . . . . . X . . . . | $$ | . . . , . . . . . , . . . . . , X . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . . , O . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . 0 . . . . | $$ | . . . . . . . . . . . . . . 9 6 . . . | $$ | . . . . . . . . . . . . . 8 7 5 O O . | $$ | . . X . . . . . . . . . . . 4 3 O X . | $$ | . . . , . . . . . , . . . . . O X . X | $$ | . . . X . . . . . O . . . 2 . O X . . | $$ | . . . . . . . . . . . . . . O X 1 . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

Am I missing something? I don't see a good outcome for Black after :b21:

?

EdLee · #7

PeterPeter wrote:

Am I missing something?

Yes.

Your sequence fails for W if there was a B stone at C17. Try again.

In other words, if we change to following board, W would still play :w1:

to fix (a), and not (b) -- why??

Click Here To Show Diagram Code: [go]$$W $$ ----------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . X . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . . , . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . . , . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . O O . | $$ | . . . . . . . . . . . . . . . b O X . | $$ | . . . , . . . . . , . . . . . O X . X | $$ | . . . . . . . . . . . . . 1 a O X . . | $$ | . . . . . . . . . . . . . . O X X . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ -----------------------------------------[/go]

PeterPeter · #8

Oh I see. I don't see an escape for Black from this net:

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

EdLee · #9

Very good! :clap:

Now you understand :w20:

better in that game.
Here is one joseki -- W also plays :w6:

to fix (a), but not (b) -- why?

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

PeterPeter · **#10**

This looks very similar. White could set a net at c.

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

EdLee · **#11**

Good. Follow-up question: what about :w2:

? Can B escape with :b3:

?

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

PeterPeter · **#12**

White would set a net with :w4:

.

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

EdLee · **#13**

Yes -- what if B ataris with :b5:

?

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

PeterPeter · **#14**

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

White will connect with :w6:

, then Black can escape at :b7:

(escaping at A fails after White B). White will capture with :w8:

, and I slightly prefer White's position.

I had to consider a lot of variations to decide on this main line - how did I do?

EdLee · **#15**

was bad -- try again.

PeterPeter wrote:

White will capture with :w8:

, and I slightly prefer White's position.

Click Here To Show Diagram Code: [go]$$B $$ | . . . , . . . . . , . . . . . , . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . 4 . O . . | $$ | . . . . . . . . . . . . . 9 7 3 O X . | $$ | . . . . . . . . . . . . . . 2 1 O X . | $$ | . . . , . . . . . , . . . 8 C O X . . | $$ | . . . . . . . . . . . . . O 6 O X . . | $$ | . . . . . . . . . . . . . . O X X . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ -----------------------------------------[/go]

This shape is a disaster for W.

EdLee · **#16**

While you work on :w8:

, here's one follow-up question about the original :w20:

in the Malkovich game.
W has two ways to fix that cut: tiger's mouth (right) or solid connect (left).
The tiger's mouth is better. Why? Try to name as many reasons as you can. (I have to crash now!

)

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

PeterPeter · **#17**

I see it now, White forces a bigger capture after :w8:

.

Click Here To Show Diagram Code: [go]$$B $$ | . . . , . . . . . , . . . . . , . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . 4 0 O . . | $$ | . . . . . . . . . . . . . 8 7 3 O X . | $$ | . . . . . . . . . . . . . 9 2 1 O X . | $$ | . . . , . . . . . , . . . . 5 O X . . | $$ | . . . . . . . . . . . . . O 6 O X . . | $$ | . . . . . . . . . . . . . . O X X . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ -----------------------------------------[/go]

If Black captures with :b9:

, White still gains after :w10:

.

PeterPeter · **#18**

EdLee wrote:

:w8: was bad -- try again.

PeterPeter wrote:

White will capture with :w8:

, and I slightly prefer White's position.

Click Here To Show Diagram Code: [go]$$B $$ | . . . , . . . . . , . . . . . , . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . 4 . O . . | $$ | . . . . . . . . . . . . . 9 7 3 O X . | $$ | . . . . . . . . . . . . . a 2 1 O X . | $$ | . . . , . . . . . , . . . 8 C O X . . | $$ | . . . . . . . . . . . . . O 6 O X . . | $$ | . . . . . . . . . . . . . . O X X . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ -----------------------------------------[/go]

This shape is a disaster for W.

Because Black can play at A?

EdLee · **#19**

PeterPeter wrote:

I see it now, White forces a bigger capture after :w8:

.

Good! That's called a squeeze.

EdLee · **#20**

Click Here To Show Diagram Code: [go]$$B Shape disaster for W $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . Q . Q . . | $$ | . . . . . . . . . . . . . # # # Q X . | $$ | . . . . . . . . . . . . . . Q # Q X . | $$ | . . . , . . . . . , . . . Q . Q X . . | $$ | . . . . . . . . . . . . . O O O X . . | $$ | . . . . . . . . . . . . . . O X X . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ -----------------------------------------[/go]

PeterPeter wrote:

Because Black can play at A?

(*) Because W's shape is crushed. See:
http://senseis.xmp.net/?SqueezingOutTheToothpaste
and
http://senseis.xmp.net/?SmallGaps
(*) Also, because W should've gotten the following result -- compare the two!

Click Here To Show Diagram Code: [go]$$Wm12 $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . O O O . . | $$ | . . . . . . . . . . . . . O Y Y O X . | $$ | . . . . . . . . . . . . 1 Y Y Y O X . | $$ | . . . , . . . . . , . . . . Y O X . . | $$ | . . . . . . . . . . . . . O O O X . . | $$ | . . . . . . . . . . . . . . O X X . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ -----------------------------------------[/go]

Cutting point in 3-3 invasion joseki

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