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Semedori

 

Semedori example
    Keywords: EndGame

[Diagram]
Diag.: Endgame problem

What if anything can White gain by playing here?

Charles Matthews


A difficult position, Charles! :-)
Looks like White can get a seki or ko to me.

Bill


[Diagram]
Diag.: White prepares the cut

Charles From a game of mine last week. I thought the basic idea was the cut at 3 for White, to gain points. Preparation 1 for 2 is obvious enough. White a for Black b would presumably been White's prerogative.

I didn't see a seki, but perhaps the position isn't exactly as in the game: I simplified it somewhat.

So, Black 8 caught me a little by surprise. Now it becomes important how many liberties the lower black group has on the outside.


[Diagram]
Diag.: Variation 1

Bill: White can also start this way, I think. Off to the races. ;-)


[Diagram]
Diag.: Variation 1 (continuation)

Charles So now Black is in a hurry to play 1? Ah, but now I see that White 4 is too naive.


[Diagram]
Diag.: Variation 1 (further continuation)

DaveSigaty: The approach seems right for Black but 3 here would be slightly better at 4 (see below [1]) perhaps.


[Diagram]
Diag.: Variation 1 (even further)

And now? Could become a double ko?


[Diagram]
Diag.: Variation 1b

Bill: B 1 is, I believe, tesuji. Now White has nothing better than W 2, I think, and the end result should be the same as the main line starting with the cut. But it is complicated. :-)


[1]

[Diagram]
Diag.: Variation 1 alternative

DaveSigaty: After 3 if White plays 4, she is simply captured by Black 5, so...


[Diagram]
Diag.: Variation 1 alternative

White has to play 4 and after the sequence to 8, Black can tenuki. White has achieved a double ko that can provide unlimited ko threats but in gote.


[Diagram]
Diag.: Variation 1 alternative

In comparison, this White 8 threatens to capture the outside ko and connect. Black's capture of the inner ko is not atari on the White stones. Black has to play 9 so White has created the double ko in sente.


[Diagram]
Diag.: Variation 1c

Bill: With the potential Black eye gone at a, White's next play is, I believe, to atari with W 1 and then connect at W 3. Through B 8 White loses the semeai, but forces Black to take all the White stones.


[Diagram]
Diag.: Variation 1c (followup)

W 3 - B 4 is almost always sente, since Black can rarely afford to let White make a huge ko.

[Diagram]
Diag.: Variation 1d

Alternatively, Black can connect with B 1. Then W 2 prevents an eye for Black. B 3 wins the semeai.


[Diagram]
Diag.: Variation 1d (continued)

Now W 1 - B 4 is sente.

All roads lead to Rome, more or less.




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