The most difficult yose problem

dany · #1

Masterpiece created by Cho U 9 dan

Click Here To Show Diagram Code: [go]$$c Black to play, komi 0.5 $$ +---------------------------+ $$ | . . O X X X X . O . X X . | $$ | . . O O O . . . O . . . . | $$ | . . . . O X X X O O O O . | $$ | . . . O . X , . . X X X . | $$ | . . . O O X . X X X . X X | $$ | . O X . O X . . . . . O . | $$ | O O O O O X , . O X X X . | $$ | X O X X O . X . . X O X X | $$ | X X X . X O X . . X O O O | $$ | . . X , . O , X X X O . . | $$ | O . . X X O O O X X O . . | $$ | X . O . O . X O X O O . . | $$ | . X O X . O . . X X O . . | $$ +---------------------------+[/go]

lichigo · #2

Wouah indeed really hard. Where did you find this problem?

dany · #3

Several years ago, in his lecture, Alexander Dinerstein 3p talked about solving this problem.
But imho not all the important moves were explained in his lecture, and some were wrong

Will someone try to find a solution?

kvasir · #4

That is good example of the maxim that yose is also a life and death problem.

Gérard TAILLE · #5

dany wrote:

Several years ago, in his lecture, Alexander Dinerstein 3p talked about solving this problem.
But imho not all the important moves were explained in his lecture, and some were wrong

Will someone try to find a solution?

This problem is quite difficult but I can try to find something.
Just a confirmation : seeing 53 black stones against 45 white stones is it a good understanding that japanese rules are used for this problem?

dany · #6

Gérard TAILLE wrote:

This problem is quite difficult but I can try to find something.
Just a confirmation : seeing 53 black stones against 45 white stones is it a good understanding that japanese rules are used for this problem?

Yes, Japanese rules, komi 0.5

Cassandra · #7

Let's start ...

Click Here To Show Diagram Code: [go]$$ Komi = 0.5; no prisoners $$ +---------------------------+ $$ | . . O X X X X . O . X X . | $$ | . . O O O . . . O . . . . | $$ | . . . . O X X X O O O O . | $$ | . . . O . X , . . X X X . | $$ | . . . O O X . X X X . X X | $$ | . O X . O X . . . . . O . | $$ | O O O O O X , . O X X X . | $$ | X O X X O . X . . X O X X | $$ | X X X . X O X . . X O O O | $$ | . . X , . O , X X X O . . | $$ | O . . X X O O O X X O . . | $$ | X . O 1 O . X O X O O . . | $$ | . X O X . O . . X X O . . | $$ +---------------------------+[/go]

Harleqin · #8

Yes, seems so, and then

Click Here To Show Diagram Code: [go]$$ Komi = 0.5; no prisoners $$ +---------------------------+ $$ | . . O X X X X . O . X X . | $$ | . . O O O . . . O . . . . | $$ | . . . . O X X X O O O O . | $$ | . . . O . X , . . X X X . | $$ | . . . O O X . X X X . X X | $$ | . O X . O X . . . . . O . | $$ | O O O O O X , . O X X X . | $$ | X O X X O . X . . X O X X | $$ | X X X a X O X . . X O O O | $$ | . . X b 2 O , X X X O . . | $$ | O . . X X O O O X X O . . | $$ | X . O 1 O . X O X O O . . | $$ | . X O X . O . . X X O . . | $$ +---------------------------+[/go]

Then 'a' or 'b'? What's that funny shape in the corner?

Cassandra · #9

Harleqin wrote:

What's that funny shape in the corner?

Probably aiming at a fight for creating a seki in the corner???

Click Here To Show Diagram Code: [go]$$ Komi = 0.5; no prisoners $$ +---------------------------+ $$ | . . O X X X X . O . X X . | $$ | . . O O O . . . O . . . . | $$ | . . . . O X X X O O O O . | $$ | . . . O . X , . . X X X . | $$ | . . . O O X . X X X . X X | $$ | . O X . O X . . . . . O . | $$ | O O O O O X , . O X X X . | $$ | X O X X O . X . . X O X X | $$ | X X X . X O X . . X O O O | $$ | . . X . . O , X X X O . . | $$ | O 2 . X X O O O X X O . . | $$ | X . O X O . X O X O O . . | $$ | . X O X . O . . X X O . . | $$ +---------------------------+[/go]

Gérard TAILLE · **#10**

Harleqin wrote:

Yes, seems so, and then

Click Here To Show Diagram Code: [go]$$ Komi = 0.5; no prisoners $$ +---------------------------+ $$ | . . O X X X X . O . X X . | $$ | . . O O O . . . O . . . . | $$ | . . . . O X X X O O O O . | $$ | . . . O . X , . . X X X . | $$ | . . . O O X . X X X . X X | $$ | . O X . O X . . . . . O . | $$ | O O O O O X , . O X X X . | $$ | X O X X O . X . . X O X X | $$ | X X X a X O X . . X O O O | $$ | . . X b 2 O , X X X O . . | $$ | O . . X X O O O X X O . . | $$ | X . O 1 O . X O X O O . . | $$ | . X O X . O . . X X O . . | $$ +---------------------------+[/go]

Then 'a' or 'b'? What's that funny shape in the corner?

As far as I am concerned I see a quite simple win for black for this yose. As a consequence I know for sure that I did not fond the good defense for white.
My best sequence begins with your suggestion Harleqin:

Click Here To Show Diagram Code: [go]$$ Komi = 0.5; no prisoners $$ +---------------------------+ $$ | . . O X X X X . O . X X . | $$ | . . O O O . . . O . . . . | $$ | . . . . O X X X O O O O . | $$ | . . . O . X , . . X X X . | $$ | . . . O O X . X X X . X X | $$ | . O X . O X . . . . . O . | $$ | O O O O O X , . O X X X . | $$ | X O X X O 4 X . . X O X X | $$ | X X X 3 X O X . . X O O O | $$ | . . X . 2 O , X X X O . . | $$ | O . . X X O O O X X O . . | $$ | X 5 O 1 O . X O X O O . . | $$ | . X O X . O . . X X O . . | $$ +---------------------------+[/go]

but now I failed to find an interesting move for white.
I tried:

Click Here To Show Diagram Code: [go]$$ $$ +---------------------------+ $$ | . . O X X X X . O . X X . | $$ | . . O O O . . . O . . . . | $$ | . . . . O X X X O O O O 6 | $$ | . . . O . X , . . X X X . | $$ | . . . O O X . X X X . X X | $$ | . O X . O X . . . . . O . | $$ | O O O O O X , . O X X X . | $$ | X O X X O O X . . X O X X | $$ | X X X X X O X . . X O O O | $$ | . . X . O O , X X X O . . | $$ | O . . X X O O O X X O 7 . | $$ | X X O X O . X O X O O 8 9 | $$ | . X O X . O . . X X O . . | $$ +---------------------------+[/go]

but now I do not see how white can cause difficulties for black. Surely I missed a hidden move somewhere.

Cassandra · **#11**

Gérard TAILLE wrote:

... I do not see how white can cause difficulties for black. Surely I missed a hidden move somewhere.

Click Here To Show Diagram Code: [go]$$ Komi = 0.5; no prisoners $$ +---------------------------+ $$ | . . O X X X X . O . X X . | $$ | . . O O O . . . O . . . . | $$ | . . . . O X X X O O O O . | $$ | . . . O . X , . . X X X . | $$ | . . . O O X . X X X . X X | $$ | . O X . O X . . . . . O . | $$ | O O O O O X , . O X X X . | $$ | X O X X O ? X . . X O X X | $$ | X X X X X O X . . X O O O | $$ | . . X . O O , X X X O . . | $$ | O 4 . X X O O O X X O . . | $$ | X . O X O . X O X O O . . | $$ | . X O X . O . . X X O . . | $$ +---------------------------+[/go]

Here you are!

jmeinh · **#12**

Cassandra wrote:

Gérard TAILLE wrote:

... I do not see how white can cause difficulties for black. Surely I missed a hidden move somewhere.

Click Here To Show Diagram Code: [go]$$ Komi = 0.5; no prisoners $$ +---------------------------+ $$ | . . O X X X X . O . X X . | $$ | . . O O O . . . O . . . . | $$ | . . . . O X X X O O O O . | $$ | . . . O . X , . . X X X . | $$ | . . . O O X . X X X . X X | $$ | . O X . O X . . . . . O . | $$ | O O O O O X , . O X X X . | $$ | X O X X O ? X . . X O X X | $$ | X X X X X O X . . X O O O | $$ | . . X . O O , X X X O . . | $$ | O 4 . X X O O O X X O . . | $$ | X . O X O . X O X O O . . | $$ | . X O X . O . . X X O . . | $$ +---------------------------+[/go]

Here you are!

Then maybe after...

Click Here To Show Diagram Code: [go]$$ Komi = 0.5; no prisoners $$ +---------------------------+ $$ | . . O X X X X . O . X X . | $$ | . . O O O . . . O . . . . | $$ | . . . . O X X X O O O O . | $$ | . . . O . X , . . X X X . | $$ | . . . O O X . X X X . X X | $$ | . O X . O X . . . . . O . | $$ | O O O O O X , . O X X X . | $$ | X O X X O 5 X . . X O X X | $$ | X X X X X O X . . X O O O | $$ | . . X 7 O O . X X X O . . | $$ | O O 6 X X O O O X X O . . | $$ | X . O X O . X O X O O . . | $$ | . X O X . O 8 . X X O . . | $$ +---------------------------+[/go]

Click Here To Show Diagram Code: [go]$$ Komi = 0.5; no prisoners $$ +---------------------------+ $$ | . . O X X X X . O . X X . | $$ | . . O O O . . . O . . . . | $$ | . . . . O X X X O O O O . | $$ | . . . O . X , . . X X X . | $$ | . . . O O X . X X X . X X | $$ | . O X . O X . . . . . O . | $$ | O O O O O X , . O X X X . | $$ | X O X X O X X . . X O X X | $$ | X X X X X O X . . X O O O | $$ | 2 . X X O O 3 X X X O . . | $$ | O O O X X O O O X X O . . | $$ | X . O X O 4 X O X O O . . | $$ | . X O X . O O 1 X X O . . | $$ +---------------------------+[/go]

... we have a first (temporary?) seki.

Cassandra · **#13**

jmeinh wrote:

... we have a first (temporary?) seki.

Yes, indeed.

But ...

Click Here To Show Diagram Code: [go]$$ Komi = 0.5; no prisoners $$ +---------------------------+ $$ | . . O X X X X . O . X X . | $$ | . . O O O . . . O . . . . | $$ | . . . . O X X X O O O O . | $$ | . . . O . X , . . X X X . | $$ | . . . O O X . X X X . X X | $$ | . O X . O X . . . . . O . | $$ | O O O O O X , . O X X X . | $$ | X O X X O . X . . X O X X | $$ | X X X 3 X O X . . X O O O | $$ | . . X . O O , X X X O . . | $$ | O . . X X O O O X X O . . | $$ | X . O X O . X O X O O . . | $$ | . X O X . O . . X X O . . | $$ +---------------------------+[/go]

...

is a mistake, ...

Click Here To Show Diagram Code: [go]$$ Komi = 0.5; no prisoners $$ +---------------------------+ $$ | . . O X X X X . O . X X . | $$ | . . O O O . . . O . . . . | $$ | . . . . O X X X O O O O . | $$ | . . . O . X , . . X X X . | $$ | . . . O O X . X X X . X X | $$ | . O X . O X . . . . . O . | $$ | O O O O O X , . O X X X . | $$ | X O X X O . X . . X O X X | $$ | X X X . X O X . . X O O O | $$ | . . X . 2 O , X X X O . . | $$ | O . . X X O O O X X O . . | $$ | X . O X O . X O X O O . . | $$ | . X O X . O . . X X O . . | $$ +---------------------------+[/go]

... as well as :w2:

.

Gérard TAILLE · **#14**

Cassandra wrote:

Harleqin wrote:

What's that funny shape in the corner?

Probably aiming at a fight for creating a seki in the corner???

Click Here To Show Diagram Code: [go]$$ Komi = 0.5; no prisoners $$ +---------------------------+ $$ | . . O X X X X . O . X X . | $$ | . . O O O . . . O . . . . | $$ | . . . . O X X X O O O O . | $$ | . . . O . X , . . X X X . | $$ | . . . O O X . X X X . X X | $$ | . O X . O X . . . . . O . | $$ | O O O O O X , . O X X X . | $$ | X O X X O . X . . X O X X | $$ | X X X . X O X . . X O O O | $$ | . . X . . O , X X X O . . | $$ | O 2 . X X O O O X X O . . | $$ | X . O X O . X O X O O . . | $$ | . X O X . O . . X X O . . | $$ +---------------------------+[/go]

Locally this :w2:

white move is good but globally it seems to me quite bad. Here again sure I missed something.

lightvector · **#15**

What if white ignores black move 17 and instead just connects the ko?

Cassandra · **#16**

Lightvector was faster with his posting, as his name already suggests :-)

Click Here To Show Diagram Code: [go]$$Bm17 Komi = 0.5; prisoners: $$ +---------------------------+ $$ | . . O X X X X . O . X X . | $$ | . . O O O O X . O . X . O | $$ | . . . . O X X X O O O O 2 | $$ | . . . O . X , . . X X X O | $$ | . . . O O X . X X X . X X | $$ | . O X . O X . . . . . O . | $$ | O O O O O X , . O X X X . | $$ | X O X X O O X . . X O X X | $$ | X X X . X O X . . X O O O | $$ | . . X , X O , X X X O . 3 | $$ | O O O X X O O O X X O X . | $$ | X X O X O . X O X O O O X | $$ | . X O X 4 O . . X X O . . | $$ +---------------------------+[/go]

Now, White has a wild bunch of ko-threats in the lower left corner.

dany · **#17**

Cassandra wrote:

Lightvector was faster with his posting, as his name already suggests :-)

Click Here To Show Diagram Code: [go]$$Bm17 Komi = 0.5; prisoners: $$ +---------------------------+ $$ | . . O X X X X . O . X X . | $$ | . . O O O O X . O . X . O | $$ | . . . . O X X X O O O O 2 | $$ | . . . O . X , . . X X X O | $$ | . . . O O X . X X X . X X | $$ | . O X . O X . . . . . O . | $$ | O O O O O X , . O X X X . | $$ | X O X X O O X . . X O X X | $$ | X X X . X O X . . X O O O | $$ | . . X , X O , X X X O . 3 | $$ | O O O X X O O O X X O X . | $$ | X X O X O . X O X O O O X | $$ | . X O X 4 O . . X X O . . | $$ +---------------------------+[/go]

Now, White has a wild bunch of ko-threats in the lower left corner.

up to 20 move everything is correct. subsequent moves will be more difficult

Cassandra · **#18**

Click Here To Show Diagram Code: [go]$$Bm21 Komi = 0.5; prisoners: $$ +---------------------------+ $$ | . . O X X X X . O . X X . | $$ | . . O O O O X . O . X . O | $$ | . . . . O X X X O O O O O | $$ | . . . O . X , . 3 X X X O | $$ | . . . O O X . X X X . X X | $$ | . O X . O X . . . . . O . | $$ | O O O O O X , . O X X X . | $$ | X O X X O O X . . X O X X | $$ | X X X . X O X . . X O O O | $$ | . . X , X O , X X X O . X | $$ | O O O X X O O O X X O X . | $$ | X X O X O . X O X O O O X | $$ | a X O X O O . 2 X X O . 1 | $$ +---------------------------+[/go]

Black is unable to turn the lower right corner into a seki.

After :b23:

White has 22 points of territory on the board, while Black has only 21.
White will gain an additional five prisoners in the seki in the lower left corner, starting with capturing at A.

Gérard TAILLE · **#19**

dany wrote:

Cassandra wrote:

Lightvector was faster with his posting, as his name already suggests :-)

Click Here To Show Diagram Code: [go]$$Bm17 Komi = 0.5; prisoners: $$ +---------------------------+ $$ | . . O X X X X . O . X X . | $$ | . . O O O O X . O . X . O | $$ | . . . . O X X X O O O O 2 | $$ | . . . O . X , . . X X X O | $$ | . . . O O X . X X X . X X | $$ | . O X . O X . . . . . O . | $$ | O O O O O X , . O X X X . | $$ | X O X X O O X . . X O X X | $$ | X X X . X O X . . X O O O | $$ | . . X , X O , X X X O . 3 | $$ | O O O X X O O O X X O X . | $$ | X X O X O . X O X O O O X | $$ | . X O X 4 O . . X X O . . | $$ +---------------------------+[/go]

Now, White has a wild bunch of ko-threats in the lower left corner.

up to 20 move everything is correct. subsequent moves will be more difficult

Yes Dany, for the time being I did not find the good sequence for black.
In the sequence here under white wins by 0.5 points => I need to gain still one point for black. Very hard indeed.

dany · **#20**

Gérard TAILLE wrote:

Very hard indeed.

Not yet

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

White win ko and game.

H12 unnecessary move

The most difficult yose problem

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