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Subtilities for ko threats handling

https://www.lifein19x19.com/viewtopic.php?t=18572

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Re: Subtilities for ko threats handling

Posted: Wed Jan 19, 2022 7:30 am
by Gérard TAILLE
dany wrote:
Gérard TAILLE wrote:
Click Here To Show Diagram Code
[go]$$B Black to play
$$ -----------------------------
$$ | . . . . . . . . X X X X . |
$$ | X X . . . . X X O O O X X |
$$ | O X X X X X O X O X . O O |
$$ | O O O O O X O X O O . X . |
$$ | . . . O B O O X X O O . . |
$$ | . . . O B O X . . X O O . |
$$ | . . . . B O X X X . X X . |
$$ | . . . . O O . O . X X O X |
$$ | O O O O . . O X X . X O . |
$$ | X X X O . . O O X X X O . |
$$ | . . O X O . . . O X O X X |
$$ | . X X X O . . . O O O O O |
$$ | . . X O O . . . . . . . . |
$$ -----------------------------[/go]
Looking at the link mentionned I found this problem. My question is : what is the purpose of the three marked black stones?
the purpose of these stones is to refute one of White's options

in my position modification this secondary option becomes the solution
Thank you Dany, I understand but I am not able to find this white option showing how black could use her three marked stones to refute this option.
Is it possible for you to show me this option or the corresponding link handling this option?

Re: Subtilities for ko threats handling

Posted: Wed Jan 19, 2022 8:15 am
by dany
Gérard TAILLE wrote: Thank you Dany, I understand but I am not able to find this white option showing how black could use her three marked stones to refute this option.
Is it possible for you to show me this option or the corresponding link handling this option?
Click Here To Show Diagram Code
[go]$$c
$$ +---------------------------+
$$ | . . . . . . . . X X X X . |
$$ | X X . . . . X X O O O X X |
$$ | O X X X X X O X O . . O W |
$$ | O O O O O X O X O O O X X |
$$ | . . . O X O O X X O O X . |
$$ | . . . O X O X . # X O O X |
$$ | . . . , X O X X X , X X O |
$$ | . . . . O O . O . X X O . |
$$ | O O O O . . O X X . X O O |
$$ | X X X O . . O O X X X O . |
$$ | X . . X O . . . O X O X X |
$$ | . X X X O . . . O O O O O |
$$ | . . X O O . . . . . . . . |
$$ +---------------------------+[/go]
White's last move (move 18) from the original problem solution is not the best in the current position
When you find the best white's move you find "how black could use her three marked stones" too

Re: Subtilities for ko threats handling

Posted: Wed Jan 19, 2022 4:10 pm
by Gérard TAILLE
dany wrote:
Gérard TAILLE wrote: Thank you Dany, I understand but I am not able to find this white option showing how black could use her three marked stones to refute this option.
Is it possible for you to show me this option or the corresponding link handling this option?
Click Here To Show Diagram Code
[go]$$c
$$ +---------------------------+
$$ | . . . . . . . . X X X X . |
$$ | X X . . . . X X O O O X X |
$$ | O X X X X X O X O . . O W |
$$ | O O O O O X O X O O O X X |
$$ | . . . O X O O X X O O X . |
$$ | . . . O X O X . # X O O X |
$$ | . . . , X O X X X , X X O |
$$ | . . . . O O . O . X X O . |
$$ | O O O O . . O X X . X O O |
$$ | X X X O . . O O X X X O . |
$$ | X . . X O . . . O X O X X |
$$ | . X X X O . . . O O O O O |
$$ | . . X O O . . . . . . . . |
$$ +---------------------------+[/go]
White's last move (move 18) from the original problem solution is not the best in the current position
When you find the best white's move you find "how black could use her three marked stones" too
With your help I think I have found a good sequence, providing Japonese rules are used (and not Chinese or AGA rules). Is it true?

Re: Subtilities for ko threats handling

Posted: Wed Jan 19, 2022 5:44 pm
by dany
Gérard TAILLE wrote: With your help I think I have found a good sequence, providing Japonese rules are used (and not Chinese or AGA rules). Is it true?
Yes, Japanese rules, 6.5 komi. What's the sequence?

Re: Subtilities for ko threats handling

Posted: Thu Jan 20, 2022 2:04 pm
by Gérard TAILLE
dany wrote:
Gérard TAILLE wrote: Thank you Dany, I understand but I am not able to find this white option showing how black could use her three marked stones to refute this option.
Is it possible for you to show me this option or the corresponding link handling this option?
Click Here To Show Diagram Code
[go]$$c
$$ +---------------------------+
$$ | . . . . . . . . X X X X . |
$$ | X X . . . . X X O O O X X |
$$ | O X X X X X O X O . . O W |
$$ | O O O O O X O X O O O X X |
$$ | . . . O X O O X X O O X . |
$$ | . . . O X O X . # X O O X |
$$ | . . . , X O X X X , X X O |
$$ | . . . . O O . O . X X O . |
$$ | O O O O . . O X X . X O O |
$$ | X X X O . . O O X X X O . |
$$ | X . . X O . . . O X O X X |
$$ | . X X X O . . . O O O O O |
$$ | . . X O O . . . . . . . . |
$$ +---------------------------+[/go]
White's last move (move 18) from the original problem solution is not the best in the current position
When you find the best white's move you find "how black could use her three marked stones" too
Though I now understand the meaning of the three marked stones I did not manage to find a white move better than the marked white stone in the diagram above. Does such white move really exist?

Re: Subtilities for ko threats handling

Posted: Thu Jan 20, 2022 6:06 pm
by dany
Gérard TAILLE wrote: Though I now understand the meaning of the three marked stones I did not manage to find a white move better than the marked white stone in the diagram above. Does such white move really exist?
There are 6 such moves ;-)

Re: Subtilities for ko threats handling

Posted: Fri Jan 21, 2022 4:24 am
by Gérard TAILLE
dany wrote:
Gérard TAILLE wrote: Though I now understand the meaning of the three marked stones I did not manage to find a white move better than the marked white stone in the diagram above. Does such white move really exist?
There are 6 such moves ;-)
Maybe we are in line but it seems we discuss on two different positions.
I considered only the following position resulting from Ichiriki problem, I mean with no black stone on J8.
Click Here To Show Diagram Code
[go]$$c
$$ +---------------------------+
$$ | . . . . . . . . X X X X . |
$$ | X X . . . . X X O O O X X |
$$ | O X X X X X O X O . . O W |
$$ | O O O O O X O X O O O X X |
$$ | . . . O B O O X X O O X . |
$$ | . . . O B O X . . X O O X |
$$ | . . . , B O X X X , X X O |
$$ | . . . . O O . O . X X O . |
$$ | O O O O . . O X X . X O O |
$$ | X X X O . . O O X X X O . |
$$ | X . . X O . . . O X O X X |
$$ | . X X X O . . . O O O O O |
$$ | . . X O O . . . . . . . . |
$$ +---------------------------+[/go]
In this position do you agree that the white marked is the only best move?
Do you agree also that the presence of the three marked stones is essential in order to say that the white marked stone is really the only best move?

Re: Subtilities for ko threats handling

Posted: Fri Jan 21, 2022 4:46 am
by dany
Gérard TAILLE wrote:
dany wrote:
Gérard TAILLE wrote: Though I now understand the meaning of the three marked stones I did not manage to find a white move better than the marked white stone in the diagram above. Does such white move really exist?
There are 6 such moves ;-)
Maybe we are in line but it seems we discuss on two different positions.
I considered only the following position resulting from Ichiriki problem, I mean with no black stone on J8.
Click Here To Show Diagram Code
[go]$$c
$$ +---------------------------+
$$ | . . . . . . . . X X X X . |
$$ | X X . . . . X X O O O X X |
$$ | O X X X X X O X O . . O W |
$$ | O O O O O X O X O O O X X |
$$ | . . . O B O O X X O O X . |
$$ | . . . O B O X . . X O O X |
$$ | . . . , B O X X X , X X O |
$$ | . . . . O O . O . X X O . |
$$ | O O O O . . O X X . X O O |
$$ | X X X O . . O O X X X O . |
$$ | X . . X O . . . O X O X X |
$$ | . X X X O . . . O O O O O |
$$ | . . X O O . . . . . . . . |
$$ +---------------------------+[/go]
In this position do you agree that the white marked is the only best move?
Do you agree also that the presence of the three marked stones is essential in order to say that the white marked stone is really the only best move?
Yes.Yes

Re: Subtilities for ko threats handling

Posted: Fri Jan 21, 2022 4:58 am
by dany
The original position and my modification are the same story, the same variations. The only difference is which variation you prefer as a solution. Ichiriki prefers the eternal life variation. I prefers another variation.

original position:
Ichiriki variation - the best
another variation

modified position:
Ichiriki variation
another variation - the best

Re: Subtilities for ko threats handling

Posted: Fri Jan 21, 2022 6:28 am
by Cassandra
dany wrote:The original position and my modification are the same story, the same variations.
Did you adjust the komi while adding a Black stone to the board?

Or did you suppose that the added Black stone has captured a White one?

Re: Subtilities for ko threats handling

Posted: Fri Jan 21, 2022 6:35 am
by Gérard TAILLE
dany wrote:The original position and my modification are the same story, the same variations. The only difference is which variation you prefer as a solution. Ichiriki prefers the eternal life variation. I prefers another variation.

original position:
Ichiriki variation - the best
another variation

modified position:
Ichiriki variation
another variation - the best
I understand Dany and I agree with your results.
As far as I am concerned I do not like very much Eternal Life and I prefer using area scoring and superko.
Here I have to recognize that in the context of japanese rules the original position is very well built. Beside the threat handling difficulty the result is quite interesting : as soon as a player try to avoid the eternal life then this player will lose by half a point.

Ther modified position avoid the Eternal life but then the result is far less interesting because white can win in several variations.

Re: Subtilities for ko threats handling

Posted: Fri Jan 21, 2022 7:45 am
by dany
Gérard TAILLE wrote: Ther modified position avoid the Eternal life but then the result is far less interesting because white can win in several variations.
No. White can win in the only variation

Re: Subtilities for ko threats handling

Posted: Fri Jan 21, 2022 8:13 am
by dany
In the original position, the interesting variation remains hidden behind Ichiriki solution. I do not like it. In the modified position the interesting variation becomes a solution and Ichiriki solution becomes a strong false idea))

Re: Subtilities for ko threats handling

Posted: Fri Jan 21, 2022 8:41 am
by dany
Cassandra wrote:
dany wrote:The original position and my modification are the same story, the same variations.
Did you adjust the komi while adding a Black stone to the board?

Or did you suppose that the added Black stone has captured a White one?
I reduced black's score by 1 point

Re: Subtilities for ko threats handling

Posted: Fri Jan 21, 2022 9:15 am
by Gérard TAILLE
dany wrote:In the original position, the interesting variation remains hidden behind Ichiriki solution. I do not like it. In the modified position the interesting variation becomes a solution and Ichiriki solution becomes a strong false idea))
Yes Dany I agree with you but I still do not see how black has to play in order that all white moves are forced (no variation).
As an example in the following position:
Click Here To Show Diagram Code
[go]$$c
$$ +---------------------------+
$$ | . . . . . . . . X X X X . |
$$ | X X . . . . X X O O O X X |
$$ | O X X X X X O X O . . O O |
$$ | O O O O O X O X O O O . . |
$$ | . . . O X O O X X O O . O |
$$ | B . . O X O X . # X O O . |
$$ | O X X X X O X X X , X X O |
$$ | . . . . O O . O . X X O . |
$$ | O O O O . . O X X . X O O |
$$ | X X X O . . O O X X X O . |
$$ | X O . X O . . . O X O X X |
$$ | . X X X O . . . O O O O O |
$$ | X . X O O . . . . . . . . |
$$ +---------------------------+[/go]
white can choose between several moves can't she?
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