Thank you ez4u.

BTW, do somebody know a (professionnal) game, played under area counting rules, in which the following scheme appears?

Click Here To Show Diagram Code

[go]$$
$$ . . . . . . . . . |
$$ . . . . . . . . . |
$$ . . . X X X X X X |
$$ . . . X O O O O O |
$$ . . . X O O X O . |
$$ . . . X O . X X . |
$$ --------------------[/go]

This configuration seems very interesting, especially for black, and I would be very interested to see how professionnal can use its potential which spreads all over the board till the very very end of the game.

This variant may be too specific, but similar unremovable kos, something like the original sending-3-returning-1 might have occurred somewhere, maybe from an ignored threat. But pattern search for such is hard without an exact pattern of outer stones.

Btw, L/D confirmation was mentioned earlier, but the rules issue here is not confirmation itself - it is the local view in it. The pass-for-ko rule of J89 removes ko considerations from hypothetical play. An imaginary confirmation with normal ko (the obvious first step of any analysis) could find that these stones are not capturable without taking (enabling) a loss elsewhere, so they are alive (like bent4 + unremovable threat, or these). The tricky part is top right W 6 stones in first example, where the "loss elsewhere" is subtle and seems hard to recognise formally with a simple enough rule (enabling de-enabling).

Yes Yann, with the position allowing the sending-3-returning-1 you mentionned you can build the same kind of position:

Area counting. Komi 7.5

Click Here To Show Diagram Code

[go]$$B Black to play and win
$$ --------------------
$$ |. X . O O X X O . |
$$ |O X O . O X X O X |
$$ |O X O O O X X O X |
$$ |. X O . O X X O . |
$$ |X X O O O X X O O |
$$ |O O O X X X X X X |
$$ |X X X X O O O O O |
$$ |X X X X O . X O . |
$$ |. X . X O X . X . |
$$ --------------------[/go]

BTW the black configuration in the bottom right corner seems here better (for black) than the one I proposed in my original problem.

On the same theme I managed to build a very surprising position with an original use of the sending 3 - return 1 configuration (in this position you can count 45 black stones and 45 white stones).

Under japanese rules the game can be stopped there but I assume area counting and komi 5.5

Click Here To Show Diagram Code

[go]$$B
$$ ------------------------
$$ |. X X . O X X X O O . |
$$ |O . X O O O X X O . X |
$$ |. . X O . . O X O . . |
$$ |X X X O . . O X O O O |
$$ |O O O O . . O X X X X |
$$ |. . . . . . O X X X X |
$$ |O O O . . O O X . X . |
$$ |X X O O O X X X X X X |
$$ |O X X X X X O O O O O |
$$ |O O O O O X O . X O . |
$$ |. X X . O X O X . X . |
$$ ------------------------[/go]

Do you see how black can win?
Did you already see such mechanism or is it new for you?
I hope I did not miss something!

Black easy win

Click Here To Show Diagram Code

[go]$$B
$$ ------------------------
$$ |. X X . O X X X O O . |
$$ |O 5 X O O O X X O 3 X |
$$ |. . X O . . O X O . . |
$$ |X X X O . . O X O O O |
$$ |O O O O . . O X X X X |
$$ |. . . . . . O X X X X |
$$ |O O O . . O O X . X . |
$$ |X X O O O X X X X X X |
$$ |O X X X X X O O O O O |
$$ |O O O O O X O . X O 1 |
$$ |. X X . O X O X 4 X 2 |
$$ ------------------------[/go]

Oops you are right Dany. I am stupid, I miss this move. I will try to improve the position in order to apply my idea. Thank you Dany for having take some time on this position.

Area counting. Komi 16.5

Click Here To Show Diagram Code

[go]$$ Black to play and win
$$ +-----------------------+
$$ | . X X . O X X X O O . |
$$ | O O X O O O X X O X X |
$$ | . . X O . , O X O . . |
$$ | X X X O . . O X O O O |
$$ | O O O O . . O X X X X |
$$ | . . , . . , O X X X X |
$$ | O O O . . O O X . X . |
$$ | X X O O O X X X X X X |
$$ | O X X X X X O O O O O |
$$ | O O O O O X O . X O . |
$$ | . X X . O X O X . X . |
$$ +-----------------------+[/go]

Dany, after you found a simple way of winning with my previous position I also considered the position above you suggested.
I have now in mind some other improvements but let's take first this position above.
First of all I do not see how you can win with a komi 16.5. Do you really confirm this result? For me I need a komi 7.5 in order to win. I must have still missed a good black move.

I checked the result with Katago and I still think that Black will win with Komi 16.5.

Can you please show me Dany in order for me to know where I am wrong? If you agree you take black stones and I try to defend with white. It's your turn.

Click Here To Show Diagram Code

[go]$$
$$ +-----------------------+
$$ | . X X 2 O X X X O O . |
$$ | O O X O O O X X O X X |
$$ | . . X O . , O X O . . |
$$ | X X X O . . O X O O O |
$$ | O O O O . . O X X X X |
$$ | . . , . . , O X X X X |
$$ | O O O . . O O X . X . |
$$ | X X O O O X X X X X X |
$$ | O X X X X X O O O O O |
$$ | O O O O O X O . X O . |
$$ | . X X 3 O X O X . X 1 |
$$ +-----------------------+[/go]

Click Here To Show Diagram Code

[go]$$
$$ +-----------------------+
$$ | . X X 2 O X X X O O . |
$$ | O O X O O O X X O X X |
$$ | 4 . X O . , O X O . . |
$$ | X X X O . . O X O O O |
$$ | O O O O . . O X X X X |
$$ | . . , . . , O X X X X |
$$ | O O O . . O O X . X . |
$$ | X X O O O X X X X X X |
$$ | O X X X X X O O O O O |
$$ | O O O O O X O . X O 5 |
$$ | . X X 3 O X O X . X 1 |
$$ +-----------------------+[/go]

Eureka! That's the move I missed! Very good timing indeed, thank you very much for your help Dany. I will continue to look for a better position but I do not know if I will find the success.

First of all, thank you again Dany for having help me to understand the subtilities of the sending 3 - return 1 scheme.
Hoping I have understood here is a new attempt to reach the theme I proposed in this topic (I am still optimistic because I knew Go is a very surprising game)

Area counting, komi 5.5

Click Here To Show Diagram Code

[go]$$ Black to play and win
$$ +-----------------------+
$$ | . X X . O O O X O O X |
$$ | O O X O . . O X O X X |
$$ | . . X O . , O X O . X |
$$ | X X X O . . O X O O . |
$$ | O O O O . . O X X O O |
$$ | . . , . . , O X X X X |
$$ | O O O O O O O X . X . |
$$ | X X X X X X X X X X X |
$$ | O O O O O X O O O O O |
$$ | O X . O O X O . X O . |
$$ | X X X . O X O X . X . |
$$ +-----------------------+[/go]

I do not see how Black can win

OK Dany, this time I take black stones and you the white ones:

Click Here To Show Diagram Code

[go]$$B
$$ +-----------------------+
$$ | . X X 1 O O O X O O X |
$$ | O O X O . . O X O X X |
$$ | . . X O . , O X O . X |
$$ | X X X O . . O X O O . |
$$ | O O O O . . O X X O O |
$$ | . . , . . , O X X X X |
$$ | O O O O O O O X . X . |
$$ | X X X X X X X X X X X |
$$ | O O O O O X O O O O O |
$$ | O X . O O X O . X O . |
$$ | X X X . O X O X . X . |
$$ +-----------------------+[/go]

Oops you are again and again right Dany, I modified my position at the last moment (in order to try and avoid dual solution) but it was not a good idea.
Here is my previous version.

Area counting, komi 5.5

Click Here To Show Diagram Code

[go]$$B Black to play and win
$$ +-----------------------+
$$ | . X X . O O O X O O . |
$$ | O O X O . . O X O X X |
$$ | . . X O . , O X O X X |
$$ | X X X O . . O X O O . |
$$ | O O O O . . O X X O O |
$$ | . . , . . , O X X X X |
$$ | O O O O O O O X . X . |
$$ | X X X X X X X X X X X |
$$ | O O O O O X O O O O O |
$$ | O X X O O X O . X O . |
$$ | . X X . O X O X . X . |
$$ +-----------------------+[/go]

Does this position work Dany? I continue to be optimistic but I am not as strong as you

I'm not sure, but it doesn't seem to work