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The most difficult yose problem

https://lifein19x19.com/viewtopic.php?t=18589

Page 4 of 8

Re: The most difficult yose problem

Posted: Sun Feb 13, 2022 10:02 am
by jmeinh
dany wrote: The current solution has 67 moves. The real solution has over 100 moves
Since Black wins against the strongest white defence we could find so far, that can only mean that W has an even stronger defence somewhere, right? (Unless Black is greedy and wants a better score than B+0,5. But that's hard for me to believe; the result so far and the balance of the furikawaris give a impression of perfection to me...)

Re: The most difficult yose problem

Posted: Sun Feb 13, 2022 10:03 am
by Gérard TAILLE
dany wrote: The current solution has 67 moves. The real solution has over 100 moves
Oops, does that mean it is possible for white to choose a far longer defense? It is more and more unbelivable. Could you give us another hint? Maybe where white can make another choice?

Re: The most difficult yose problem

Posted: Sun Feb 13, 2022 10:17 am
by dany
Gérard TAILLE wrote:
dany wrote: The current solution has 67 moves. The real solution has over 100 moves
Oops, does that mean it is possible for white to choose a far longer defense? It is more and more unbelivable. Could you give us another hint? Maybe where white can make another choice?
The same ko but with more ko threats :)

Hint 3. In the position are more ko threats. But white and also black must prepare them...beforehand

Re: The most difficult yose problem

Posted: Sun Feb 13, 2022 11:03 am
by Gérard TAILLE
dany wrote:
Gérard TAILLE wrote:
dany wrote: The current solution has 67 moves. The real solution has over 100 moves
Oops, does that mean it is possible for white to choose a far longer defense? It is more and more unbelivable. Could you give us another hint? Maybe where white can make another choice?
The same ko but with more ko threats :)

Hint 3. In the position are more ko threats. But white and also black must prepare them...beforehand
Is it a good improvment ? (I still need some more work to continue from this new idea)

Re: The most difficult yose problem

Posted: Sun Feb 13, 2022 11:23 am
by dany
dany wrote: The same ko but with more ko threats :)

Hint 3. In the position are more ko threats. But white and also black must prepare them...beforehand
Gérard TAILLE wrote: Is it a good improvment ? (I still need some more work to continue from this new idea)
Click Here To Show Diagram Code
[go]$$Wm24
$$ +---------------------------+
$$ | . . O X X X X . O . X X . |
$$ | . . O O O O X . O . X . O |
$$ | . . . . O X X X O O O O O |
$$ | . . . O 2 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 |
$$ | X X X . X O X . . X O O O |
$$ | . . X , X O 1 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 |
$$ | . X O X O O . O X X O . X |
$$ +---------------------------+[/go]
Yes, 24 and 25 prepare ko threats

Re: The most difficult yose problem

Posted: Sun Feb 13, 2022 11:34 am
by Gérard TAILLE
dany wrote:
dany wrote: The same ko but with more ko threats :)

Hint 3. In the position are more ko threats. But white and also black must prepare them...beforehand
Gérard TAILLE wrote: Is it a good improvment ? (I still need some more work to continue from this new idea)
Click Here To Show Diagram Code
[go]$$Wm24
$$ +---------------------------+
$$ | . . O X X X X . O . X X . |
$$ | . . O O O O X . O . X . O |
$$ | . . . . O X X X O O O O O |
$$ | . . . O 2 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 |
$$ | X X X . X O X . . X O O O |
$$ | . . X , X O 1 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 |
$$ | . X O X O O . O X X O . X |
$$ +---------------------------+[/go]
Yes, 24 and 25 prepare ko threats
Click Here To Show Diagram Code
[go]$$Wm24
$$ +---------------------------+
$$ | . . O X X X X . O . X X . |
$$ | . . O O O O X . O . X . O |
$$ | . . . . O X X X O O O O O |
$$ | . . . O X X , . B B B B O |
$$ | . . . O O X . B B B . B B |
$$ | . O X . O X . . . . . W . |
$$ | O O O O O X , . O X X X . |
$$ | X O X X O O X . . X O X X |
$$ | X X X . X O X . . X O O O |
$$ | . . X , X O 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 |
$$ | . X O X O O . O X X O . X |
$$ +---------------------------+[/go]
What I have not yet discovered is how to use the white marked stone. I guess I can build a damezumari on the black marked group but it is not clear if I have to search an atari or a seki. I continue to search. In any case it is quite interesting.

Re: The most difficult yose problem

Posted: Sun Feb 13, 2022 11:41 am
by Cassandra
Click Here To Show Diagram Code
[go]$$Bm59 Komi = 0.5; prisoners :b19: :w5:
$$ +---------------------------+
$$ | . . O X X X X X O . O . O |
$$ | . 1 O O O O X X O . X . O |
$$ | . . X a O X X X O O O O O |
$$ | . . . O X X , . X X X X O |
$$ | . . . O O X . X X X . X X |
$$ | . O Z . O X . . . . . O . |
$$ | O O O O O X O . O X X X . |
$$ | X O X X O O X X . X O X X |
$$ | X X X . X O X O . X O O O |
$$ | . . X , X O O X X X O . X |
$$ | O O O X X O O O X X O X O |
$$ | . X O X O . X O X O O O . |
$$ | O X O X O O . O X X O . O |
$$ +---------------------------+[/go]
I would like to suggest this :b59:.

Black's :bx: does not have any benefit for the ensuing sequence after the used move at A, so it is unlikely that A is the correct choice here.

Re: The most difficult yose problem

Posted: Sun Feb 13, 2022 11:52 am
by Cassandra
Click Here To Show Diagram Code
[go]$$B
$$ +---------------------------+
$$ | . . O X X X X X O X X X . |
$$ | . . O O O O X X O . X X O |
$$ | . . . . O X X X O O O O O |
$$ | . . . O X X B W W 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 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 |
$$ | . X O X O O . O X X O . X |
$$ +---------------------------+[/go]
Just another matter of shape:

Before the ko starts, White would like to have created another formation at the top ( :wc: :bc:), reducing Black's string to the left to only three liberties.

Re: The most difficult yose problem

Posted: Sun Feb 13, 2022 12:00 pm
by Cassandra
Click Here To Show Diagram Code
[go]$$B
$$ +---------------------------+
$$ | . . O X X X X . O . X X . |
$$ | . . O O O O X . O . X . O |
$$ | . . . . O X X X O O O O O |
$$ | . . . O . X , . . 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 |
$$ | . X O X O O . . X X O . M |
$$ +---------------------------+[/go]
Just another deep "feeling":

I can't really believe that the correct solution sequence should contain so many White passes.
Therefore, I do not "feel" that Black will play :b21: at :ex: in the lower right corner.

Additionally, I do not "feel" that White would start the ko-fight, as this measure would cost her some Black stones in her prisoners lid.

Re: The most difficult yose problem

Posted: Sun Feb 13, 2022 3:48 pm
by Gérard TAILLE
Click Here To Show Diagram Code
[go]$$Bm21 Komi = 0.5; prisoners: :b2: :w1:
$$ +---------------------------+
$$ | . . O X X X X . O . X X . |
$$ | . . O O O O X . O . X . O |
$$ | . . . . O X X X O O O O O |
$$ | . . . O . X , . . 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 |
$$ | . X O X O O . 2 X X O . 1 |
$$ +---------------------------+[/go]
After :b21: we saw that this :w22: is losing.
What about the move below:
Click Here To Show Diagram Code
[go]$$Bm21 Komi = 0.5; prisoners: :b2: :w1:
$$ +---------------------------+
$$ | . . O X X X X . O . X X . |
$$ | . . O O O O X . O . X . O |
$$ | . . . . O X X X O O O O O |
$$ | . . . O . X , . 2 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 |
$$ | . X O X O O . . X X O . 1 |
$$ +---------------------------+[/go]
and now if
Click Here To Show Diagram Code
[go]$$Bm21 Komi = 0.5; prisoners: :b2: :w1:
$$ +---------------------------+
$$ | . . O X X X X . O . X X . |
$$ | . . O O O O X . O . X . O |
$$ | . . . . O X X X O O O O O |
$$ | . . . O . X , 3 2 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 |
$$ | . X O X O O . 4 X X O . 1 |
$$ +---------------------------+[/go]
and white has gained one point

and if
Click Here To Show Diagram Code
[go]$$Bm21 Komi = 0.5; prisoners: :b2: :w1:
$$ +---------------------------+
$$ | . . O X X X X . O . X X . |
$$ | . . O O O O X . O . X . O |
$$ | . . . . O X X X O O O O O |
$$ | . . . O 8 X 5 4 2 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 9 X X X O . X |
$$ | O O O X X O O O X X O X . |
$$ | X X O X O 6 X O X O O O X |
$$ | . X O X O O 7 3 X X O . 1 |
$$ +---------------------------+[/go]
black has lost one ko threat

Re: The most difficult yose problem

Posted: Sun Feb 13, 2022 4:15 pm
by jmeinh
If we want to use the white stone on the right side, how about this?



oops... not quite 100 moves, but pretty close!

Re: The most difficult yose problem

Posted: Sun Feb 13, 2022 4:56 pm
by jmeinh
Gérard TAILLE wrote:
Click Here To Show Diagram Code
[go]$$Bm21 Komi = 0.5; prisoners: :b2: :w1:
$$ +---------------------------+
$$ | . . O X X X X . O . X X . |
$$ | . . O O O O X . O . X . O |
$$ | . . . . O X X X O O O O O |
$$ | . . . O . X , . . 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 |
$$ | . X O X O O . 2 X X O . 1 |
$$ +---------------------------+[/go]
After :b21: we saw that this :w22: is losing.
What about the move below:
Click Here To Show Diagram Code
[go]$$Bm21 Komi = 0.5; prisoners: :b2: :w1:
$$ +---------------------------+
$$ | . . O X X X X . O . X X . |
$$ | . . O O O O X . O . X . O |
$$ | . . . . O X X X O O O O O |
$$ | . . . O . X , . 2 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 |
$$ | . X O X O O . . X X O . 1 |
$$ +---------------------------+[/go]
and now if
Click Here To Show Diagram Code
[go]$$Bm21 Komi = 0.5; prisoners: :b2: :w1:
$$ +---------------------------+
$$ | . . O X X X X . O . X X . |
$$ | . . O O O O X . O . X . O |
$$ | . . . . O X X X O O O O O |
$$ | . . . O . X , 3 2 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 |
$$ | . X O X O O . 4 X X O . 1 |
$$ +---------------------------+[/go]
and white has gained one point

and if
Click Here To Show Diagram Code
[go]$$Bm21 Komi = 0.5; prisoners: :b2: :w1:
$$ +---------------------------+
$$ | . . O X X X X . O . X X . |
$$ | . . O O O O X . O . X . O |
$$ | . . . . O X X X O O O O O |
$$ | . . . O 8 X 5 4 2 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 9 X X X O . X |
$$ | O O O X X O O O X X O X . |
$$ | X X O X O 6 X O X O O O X |
$$ | . X O X O O 7 3 X X O . 1 |
$$ +---------------------------+[/go]
black has lost one ko threat
In the second diagram, Black could remove the D4 ko threat before starting the ko fight, and also the indirect ko threat on G7 (assuming that W has set 28 to 29, which seems more efficient to me). This 2-point loss should be compensated by connecting G2.

Re: The most difficult yose problem

Posted: Sun Feb 13, 2022 5:30 pm
by dany
jmeinh wrote:
Gérard TAILLE wrote:
Click Here To Show Diagram Code
[go]$$Bm21 Komi = 0.5; prisoners: :b2: :w1:
$$ +---------------------------+
$$ | . . O X X X X . O . X X . |
$$ | . . O O O O X . O . X . O |
$$ | . . . . O X X X O O O O O |
$$ | . . . O . X , . . 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 |
$$ | . X O X O O . 2 X X O . 1 |
$$ +---------------------------+[/go]
After :b21: we saw that this :w22: is losing.
What about the move below:
Click Here To Show Diagram Code
[go]$$Bm21 Komi = 0.5; prisoners: :b2: :w1:
$$ +---------------------------+
$$ | . . O X X X X . O . X X . |
$$ | . . O O O O X . O . X . O |
$$ | . . . . O X X X O O O O O |
$$ | . . . O . X , . 2 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 |
$$ | . X O X O O . . X X O . 1 |
$$ +---------------------------+[/go]
and now if
Click Here To Show Diagram Code
[go]$$Bm21 Komi = 0.5; prisoners: :b2: :w1:
$$ +---------------------------+
$$ | . . O X X X X . O . X X . |
$$ | . . O O O O X . O . X . O |
$$ | . . . . O X X X O O O O O |
$$ | . . . O . X , 3 2 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 |
$$ | . X O X O O . 4 X X O . 1 |
$$ +---------------------------+[/go]
and white has gained one point

and if
Click Here To Show Diagram Code
[go]$$Bm21 Komi = 0.5; prisoners: :b2: :w1:
$$ +---------------------------+
$$ | . . O X X X X . O . X X . |
$$ | . . O O O O X . O . X . O |
$$ | . . . . O X X X O O O O O |
$$ | . . . O 8 X 5 4 2 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 9 X X X O . X |
$$ | O O O X X O O O X X O X . |
$$ | X X O X O 6 X O X O O O X |
$$ | . X O X O O 7 3 X X O . 1 |
$$ +---------------------------+[/go]
black has lost one ko threat
In the second diagram, Black could remove the D4 ko threat before starting the ko fight, and also the indirect ko threat on G7 (assuming that W has set 28 to 29, which seems more efficient to me). This 2-point loss should be compensated by connecting G2.
:w22: interesting move
Click Here To Show Diagram Code
[go]$$Bm21 Komi = 0.5; prisoners: :b2: :w1:
$$ +---------------------------+
$$ | . . O X X X X . O . X X . |
$$ | . . O O O O X . O . X . O |
$$ | . . . . O X X X O O O O O |
$$ | . . . O 8 X 6 4 2 X X X O |
$$ | . . . O O X 7 X X X . X X |
$$ | . 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 9 X O 5 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 |
$$ | . X O X O O . 3 X X O . 1 |
$$ +---------------------------+[/go]
both black and white lost 4 points and 1 ko threat. so black still win

or
Click Here To Show Diagram Code
[go]$$Bm21 Komi = 0.5; prisoners: :b2: :w1:
$$ +---------------------------+
$$ | . . O X X X X . O . X X . |
$$ | . . O O O O X . O . X . O |
$$ | . . . . O X X X O O O O O |
$$ | . . . O 6 X . 5 2 X X X O |
$$ | . . . O O X . X X X . X X |
$$ | . O X . O X . . . . . O . |
$$ | O O O O O X 9 . O X X X . |
$$ | X O X X O O X . . X O X X |
$$ | X X X . X O X . . X O O O |
$$ | . . X 7 X O 4 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 |
$$ | . X O X O O . 3 X X O . 1 |
$$ +---------------------------+[/go]
black lost 3 points and white lost 4 points. both lost 1 ko threat. so black still win

Re: The most difficult yose problem

Posted: Mon Feb 14, 2022 4:46 am
by Gérard TAILLE
dany wrote:
jmeinh wrote:
Gérard TAILLE wrote:
Click Here To Show Diagram Code
[go]$$Bm21 Komi = 0.5; prisoners: :b2: :w1:
$$ +---------------------------+
$$ | . . O X X X X . O . X X . |
$$ | . . O O O O X . O . X . O |
$$ | . . . . O X X X O O O O O |
$$ | . . . O . X , . . 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 |
$$ | . X O X O O . 2 X X O . 1 |
$$ +---------------------------+[/go]
After :b21: we saw that this :w22: is losing.
What about the move below:
Click Here To Show Diagram Code
[go]$$Bm21 Komi = 0.5; prisoners: :b2: :w1:
$$ +---------------------------+
$$ | . . O X X X X . O . X X . |
$$ | . . O O O O X . O . X . O |
$$ | . . . . O X X X O O O O O |
$$ | . . . O . X , . 2 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 |
$$ | . X O X O O . . X X O . 1 |
$$ +---------------------------+[/go]
and now if
Click Here To Show Diagram Code
[go]$$Bm21 Komi = 0.5; prisoners: :b2: :w1:
$$ +---------------------------+
$$ | . . O X X X X . O . X X . |
$$ | . . O O O O X . O . X . O |
$$ | . . . . O X X X O O O O O |
$$ | . . . O . X , 3 2 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 |
$$ | . X O X O O . 4 X X O . 1 |
$$ +---------------------------+[/go]
and white has gained one point

and if
Click Here To Show Diagram Code
[go]$$Bm21 Komi = 0.5; prisoners: :b2: :w1:
$$ +---------------------------+
$$ | . . O X X X X . O . X X . |
$$ | . . O O O O X . O . X . O |
$$ | . . . . O X X X O O O O O |
$$ | . . . O 8 X 5 4 2 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 9 X X X O . X |
$$ | O O O X X O O O X X O X . |
$$ | X X O X O 6 X O X O O O X |
$$ | . X O X O O 7 3 X X O . 1 |
$$ +---------------------------+[/go]
black has lost one ko threat
In the second diagram, Black could remove the D4 ko threat before starting the ko fight, and also the indirect ko threat on G7 (assuming that W has set 28 to 29, which seems more efficient to me). This 2-point loss should be compensated by connecting G2.
:w22: interesting move
Click Here To Show Diagram Code
[go]$$Bm21 Komi = 0.5; prisoners: :b2: :w1:
$$ +---------------------------+
$$ | . . O X X X X . O . X X . |
$$ | . . O O O O X . O . X . O |
$$ | . . . . O X X X O O O O O |
$$ | . . . O 8 X 6 4 2 X X X O |
$$ | . . . O O X 7 X X X . X X |
$$ | . 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 9 X O 5 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 |
$$ | . X O X O O . 3 X X O . 1 |
$$ +---------------------------+[/go]
both black and white lost 4 points and 1 ko threat. so black still win

or
Click Here To Show Diagram Code
[go]$$Bm21 Komi = 0.5; prisoners: :b2: :w1:
$$ +---------------------------+
$$ | . . O X X X X . O . X X . |
$$ | . . O O O O X . O . X . O |
$$ | . . . . O X X X O O O O O |
$$ | . . . O 6 X . 5 2 X X X O |
$$ | . . . O O X . X X X . X X |
$$ | . O X . O X . . . . . O . |
$$ | O O O O O X 9 . O X X X . |
$$ | X O X X O O X . . X O X X |
$$ | X X X . X O X . . X O O O |
$$ | . . X 7 X O 4 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 |
$$ | . X O X O O . 3 X X O . 1 |
$$ +---------------------------+[/go]
black lost 3 points and white lost 4 points. both lost 1 ko threat. so black still win
Very convincing explanation. Thank you Dany and Jmeinh

Re: The most difficult yose problem

Posted: Mon Feb 14, 2022 5:25 am
by Gérard TAILLE
jmeinh wrote:If we want to use the white stone on the right side, how about this?



oops... not quite 100 moves, but pretty close!
White can reach 102 moves but by losing one point => black wins by 1.5 points in this variation:

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