The most difficult yose problem

dany · Post by **dany** » Sun Jan 30, 2022 1:05 pm

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 · Post by **lichigo** » Sun Jan 30, 2022 1:14 pm

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

dany · Post by **dany** » Tue Feb 08, 2022 7:53 am

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 · Post by **kvasir** » Tue Feb 08, 2022 10:01 am

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

Gérard TAILLE · Post by **Gérard TAILLE** » Wed Feb 09, 2022 4:05 am

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 · Post by **dany** » Wed Feb 09, 2022 5:56 am

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 · Post by **Cassandra** » Thu Feb 10, 2022 3:17 am

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 · Post by **Harleqin** » Thu Feb 10, 2022 7:21 am

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 · Post by **Cassandra** » Thu Feb 10, 2022 8:05 am

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 · Post by **Gérard TAILLE** » Thu Feb 10, 2022 11:31 am

Harleqin wrote:Yes, seems so, and then

$$ Komi = 0.5; no prisoners
$$ +---------------------------+
$$ | . . O X X X X . O . X X . |
$$ | . . 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 . . |
$$ | . X O X . O . . X X O . . |
$$ +---------------------------+
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 · Post by **Cassandra** » Thu Feb 10, 2022 11:43 am

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 · Post by **jmeinh** » Thu Feb 10, 2022 12:31 pm

Cassandra wrote:
Gérard TAILLE wrote:... I do not see how white can cause difficulties for black. Surely I missed a hidden move somewhere.

$$ Komi = 0.5; no prisoners
$$ +---------------------------+
$$ | . . O X X X X . O . X X . |
$$ | . . 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 . . |
$$ | . X O X . O . . X X O . . |
$$ +---------------------------+
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 · Post by **Cassandra** » Thu Feb 10, 2022 2:11 pm

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

.

Gérard TAILLE · Post by **Gérard TAILLE** » Fri Feb 11, 2022 10:40 am

Cassandra wrote:
Harleqin wrote:What's that funny shape in the corner?
Probably aiming at a fight for creating a seki in the corner???

$$ Komi = 0.5; no prisoners
$$ +---------------------------+
$$ | . . O X X X X . O . X X . |
$$ | . . 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 . . |
$$ | . X O X . O . . X X O . . |
$$ +---------------------------+
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

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

lightvector · Post by **lightvector** » Fri Feb 11, 2022 11:47 am

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

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