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Tsumegos from real games
http://www.lifein19x19.com/viewtopic.php?f=15&t=17076		 Page 2 of 6
Author:  xela [ Tue Feb 25, 2020 4:12 am ]
Post subject:  Re: Tsumegos from real games
Tsumego 4, minor detail of move order:
Click Here To Show Diagram Code
[go]$$Bc
$$ ---------------------------------------
$$ | . . . . b 9 . . . . . . . . . . . . . |
$$ | . . W . 5 4 0 8 . . . . . . . . . . . |
$$ | . X W a 3 O 1 X O . . . . O X . . . . |
$$ | . X X O 6 X O O 2 O . . . O X X X . . |
$$ | . X O O . 7 X X O . . . . . . . O . . |
$$ | . . X X O O . . O O . . . . X X O . . |
$$ | . . . . X O X X . X O . . . . O . . . |
$$ | . . . X X X O X . X . . . . . . . . . |
$$ | . . X . . O O . . . . . . . . . . . . |[/go]

:b11: at a. If black omits :b9:, then white can play b and save the :wc: stones.
Author:  jlt [ Tue Feb 25, 2020 6:15 am ]
Post subject:  Re: Tsumegos from real games
Re: tsumego 3. Here is Katago's analysis.


Suppose first that White pushes, Black blocks and White cuts.
Click Here To Show Diagram Code
[go]$$Wc The four black stones are captured
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O O X X . . . . . . . . . . . . . |
$$ | . . O X . O . X . . . . . X . X X . . |
$$ | . . O X . . . . . , . . . . . O . . . |
$$ | . . O X . . 7 5 6 . . . . . . . O . . |
$$ | . . O O X X 2 3 4 . . . . . . O X . . |
$$ | . . . O O X 1 X X O . . . . . . O . . |
$$ | . . . . X W W W W X . . . . . . . . . |
$$ | . . . . X . . . . . . . . . . . . . . |
$$ | . . . , . X . . . , . . . . . , . . . |[/go]


(White shouldn't play :w7: at E15, otherwise Black sacrifices three stones and plays :b8: at :w7:.)

If Black protects the four stones with :b6:, then other stones are caught in a ladder.

Click Here To Show Diagram Code
[go]$$Wc
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O O X X . . . . . . . . . . . . . |
$$ | . . O X . O . X . . . . . X . X X . . |
$$ | . . O X . 6 . . . , . . . . . O . . . |
$$ | . . O X . . . 5 . . . . . . . . O . . |
$$ | . . O O X X 2 3 4 7 . . . . . O X . . |
$$ | . . . O O X 1 X X O . . . . . . O . . |
$$ | . . . . X W W W W X . . . . . . . . . |
$$ | . . . . X . . . . . . . . . . . . . . |
$$ | . . . , . X . . . , . . . . . , . . . |[/go]


However, before blocking, Black may want to make the exchange K14-L13 first, in which case the above variations don't work anymore, so White has to play :w5: differently. Black has to extend at :b6: otherwise the preceding variations work again, and then :w7: captures the cutting stone K12 in a ladder.

Click Here To Show Diagram Code
[go]$$Wc
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O O X X . . . . . . . . . . . . . |
$$ | . . O X . O . X . . . . . X . X X . . |
$$ | . . O X . . . . . , . . . . . O . . . |
$$ | . . O X . . . . . 6 . . . . . . O . . |
$$ | . . O O X X 4 . . 2 5 . . . . O X . . |
$$ | . . . O O X 1 X X O 3 . . . . . O . . |
$$ | . . . . X W W W W X . . . . . . . . . |
$$ | . . . . X . . . . 7 . . . . . . . . . |
$$ | . . . , . X . . . , . . . . . , . . . |[/go]


xela wrote:
But I don't think of this as tesuji, white is playing fairly blunt moves.


I know these moves are blunt, but because my reading is too shallow, I couldn't see that a succession of 7 blunt moves actually works. That's one of the reasons why I am a kyu player...
Author:  jlt [ Tue Feb 25, 2020 6:30 am ]
Post subject:  Re: Tsumegos from real games
Tsumego 4, analysis by Katago:

Suppose White cuts with :w6: as in Kirby's and xela's posts, then White loses somes stones but ends in sente: after :w10:, Black needs to play "a".
Click Here To Show Diagram Code
[go]$$Bc
$$ ---------------------------------------
$$ | . . . . 9 8 . . . . . . . . . . . . . |
$$ | . . O . 5 4 . 0 . . . . . . . . . . . |
$$ | . X O a 3 O 1 X O . . . . O X . . . . |
$$ | . X X O 6 X O O 2 O . . . O X X X . . |
$$ | . X O O . 7 X X O . . . . . . . O . . |
$$ | . . X X O O . . O O . . . . X X O . . |
$$ | . . . . X O X X . X O . . . . O . . . |
$$ | . . . X X X O X . X . . . . . . . . . |
$$ | . . X . . O O . . . . . . . . . . . . |[/go]


So White won't bother cutting at :w6: and plays as follows:
Click Here To Show Diagram Code
[go]$$Bc
$$ ---------------------------------------
$$ | . . . . 7 6 . . . . . . . . . . . . . |
$$ | . . O . 5 4 . 8 . . . . . . . . . . . |
$$ | . X O . 3 O 1 X O . . . . O X . . . . |
$$ | . X X O . X O O 2 O . . . O X X X . . |
$$ | . X O O 9 . X X O . . . . . . . O . . |
$$ | . . X X O O . . O O . . . . X X O . . |
$$ | . . . . X O X X . X O . . . . O . . . |
$$ | . . . X X X O X . X . . . . . . . . . |
$$ | . . X . . O O . . . . . . . . . . . . |[/go]
Author:  jlt [ Wed Apr 29, 2020 8:48 am ]
Post subject:  Re: Tsumegos from real games
Tsumego #5: An easy one but I didn't take the trouble to read it during the game.

White to play. Assume White is alive. What is the status of the black group?

Click Here To Show Diagram Code
[go]$$Wc
$$ ----------------
$$ O O X . . . . . |
$$ O X X X X . . . |
$$ O O O O O X X X |
$$ . O O . O O O O |[/go]
Author:  EricBackus [ Wed Apr 29, 2020 10:03 am ]
Post subject:  Re: Tsumegos from real games
jlt wrote:
Tsumego #5: An easy one but I didn't take the trouble to read it during the game.

White to play. Assume White is alive. What is the status of the black group?

Click Here To Show Diagram Code
[go]$$Wc
$$ ----------------
$$ O O X . . . . . |
$$ O X X X X . . . |
$$ O O O O O X X X |
$$ . O O . O O O O |[/go]

I think: Black is alive, but white can make a gote seki.

Click Here To Show Diagram Code
[go]$$Wc This attack fails
$$ ----------------
$$ O O X . . 1 2 5 |
$$ O X X X X 4 3 6 |
$$ O O O O O X X X |
$$ . O O . O O O O |[/go]

Click Here To Show Diagram Code
[go]$$Wc Gote seki
$$ ----------------
$$ O O X . 5 2 1 . |
$$ O X X X X 4 . 3 |
$$ O O O O O X X X |
$$ . O O . O O O O |[/go]

Black could alternatively make this a ko, but this is unlikely to be better than seki.
Click Here To Show Diagram Code
[go]$$Wc Ko, white takes first
$$ ----------------
$$ O O X . 3 4 1 . |
$$ O X X X X . 2 . |
$$ O O O O O X X X |
$$ . O O . O O O O |[/go]
Author:  jlt [ Sat May 09, 2020 3:57 am ]
Post subject:  Re: Tsumegos from real games
Tsumego #6: Black to play. Can Black kill a group?

Click Here To Show Diagram Code
[go]$$Bc Black to play
$$ ---------------------------------------
$$ | . . . . . . . O . . . . . . . . . . . |
$$ | . O X . . O O . O X . X X O X O O . . |
$$ | . O X O O O X O O X . . O X . X O . . |
$$ | O X O O X X X X X , . . . X X X . O . |
$$ | . X X X . . . . . . X . O . . . X O O |
$$ | . X . . X . O O O . X O . . . . X O X |
$$ | . . X O . O . X O X O . . O O X . X . |
$$ | . X O . . . O X O X . O O . O O X . X |
$$ | . X O . O . O O X X . X O O X X X X O |
$$ | X O O X O X . . . , . X O X . X . O . |
$$ | . X . O O X . O . . . . X . X X . O . |
$$ | . . . O X X . . . . X X X X O O O . . |
$$ | . X O O . . . X . X X O O O O X . . . |
$$ | . X O X . . . . O X O . . . O X O O . |
$$ | . X O X . X . X X O . . O X . X X X . |
$$ | . X X O . . X . O , O . O X . , . . . |
$$ | . . X O . O X . X O . O X O . X . . . |
$$ | . O O . O . O X X X O O X X . . . . . |
$$ | . . . . . . O . O O . . . . . . . . . |
$$ ---------------------------------------[/go]
Author:  Harleqin [ Sat May 09, 2020 6:04 am ]
Post subject:  Re: Tsumegos from real games
Like this probably:

Click Here To Show Diagram Code
[go]$$Bc Black to play
$$ ---------------------------------------
$$ | . . . . . . . O . . . . . . . . . . . |
$$ | . O X . . O O . O X . X X O X O O . . |
$$ | . O X O O O X O O X . . O X . X O . . |
$$ | O X O O X X X X X , . . . X X X . O . |
$$ | . X X X . . . . . . X . O . . . X O O |
$$ | . X . . X . O O O . X O 3 a . . X O X |
$$ | . . X O . O . X O X O 1 . O O X . X . |
$$ | . X O . . . O X O X 2 O O . O O X . X |
$$ | . X O . O . O O X X . X O O X X X X O |
$$ | X O O X O X . . . , . X O X . X . O . |
$$ | . X . O O X . O . . . . X . X X . O . |
$$ | . . . O X X . . . . X X X X O O O . . |
$$ | . X O O . . . X . X X O O O O X . . . |
$$ | . X O X . . . . O X O . . . O X O O . |
$$ | . X O X . X . X X O . . O X . X X X . |
$$ | . X X O . . X . O , O . O X . , . . . |
$$ | . . X O . O X . X O . O X O . X . . . |
$$ | . O O . O . O X X X O O X X . . . . . |
$$ | . . . . . . O . O O . . . . . . . . . |
$$ ---------------------------------------[/go]


If 2 captures, 3 at a.
Author:  jlt [ Sat May 09, 2020 8:33 am ]
Post subject:  Re: Tsumegos from real games
It seems that this is the correct :b1:, but White can play :w2: differently and get a ko.
Author:  Harleqin [ Sun May 10, 2020 2:54 pm ]
Post subject:  Re: Tsumegos from real games
Oh.
Click Here To Show Diagram Code
[go]$$Bc Black to play
$$ ---------------------------------------
$$ | . . . . . . . O . . . . . . . . . . . |
$$ | . O X . . O O . O X . X X O X O O . . |
$$ | . O X O O O X O O X . . O X . X O . . |
$$ | O X O O X X X X X , . . . X X X . O . |
$$ | . X X X . . . . . . X 7 O 2 . . X O O |
$$ | . X . . X . O O O . X O . 4 3 . X O X |
$$ | . . X O . O . X O X O 1 6 O O X . X . |
$$ | . X O . . . O X O X 5 O O . O O X . X |
$$ | . X O . O . O O X X . X O O X X X X O |
$$ | X O O X O X . . . , . X O X . X . O . |
$$ | . X . O O X . O . . . . X . X X . O . |
$$ | . . . O X X . . . . X X X X O O O . . |
$$ | . X O O . . . X . X X O O O O X . . . |
$$ | . X O X . . . . O X O . . . O X O O . |
$$ | . X O X . X . X X O . . O X . X X X . |
$$ | . X X O . . X . O , O . O X . , . . . |
$$ | . . X O . O X . X O . O X O . X . . . |
$$ | . O O . O . O X X X O O X X . . . . . |
$$ | . . . . . . O . O O . . . . . . . . . |
$$ ---------------------------------------[/go]
Author:  jlt [ Fri May 22, 2020 8:29 am ]
Post subject:  Re: Tsumegos from real games
This one should be easy.

Problem #7: White to play and win the capturing race.

Click Here To Show Diagram Code
[go]$$Wc White to play
$$ ---------------------------------------
$$ | . . . . . . . . . . . X . X X . X . . |
$$ | . . . X . . . . X O O O X X X X O O . |
$$ | . . O . . X . . X X . O X O O X O . . |
$$ | . . . O . . . . . , X O X O X X O . . |
$$ | . . . . . . . . . . X O O O O X X O . |
$$ | . . O . . . . . . . . O X X . O X O . |
$$ | . . . . . . . . . . X O . O O O X O . |
$$ | . . . . . . . . . . X O O O X X X O . |
$$ | . . . . . . . . . . X O X X X X O O . |
$$ | . . . X . . . . O O X O X O . X O O X |
$$ | . . . X O . . . O X . X O . O X O X . |
$$ | . . X O . O O O X X . . . . . X X X . |
$$ | . . X O . X X O X O . O O O O O O O . |
$$ | . . X O . . . X X O . . X X X X O . . |
$$ | . X O O O X . X . O X . . X . X O . . |
$$ | . X O , O X . . . O . . O X X O . . . |
$$ | . . X O O O X X X O . X O X O O . . . |
$$ | . X . X . O X . X O X . X . X O . . . |
$$ | . . X . . . . . X O . . . X O O . . . |
$$ ---------------------------------------[/go]
Author:  Knotwilg [ Fri May 22, 2020 11:28 am ]
Post subject:  Re: Tsumegos from real games
Click Here To Show Diagram Code
[go]$$W White to play
$$ ---------------------------------------
$$ | . . . . . . . . 4 2 3 X . X X . X . . |
$$ | . . . X . . . . X O O O X X X X O O . |
$$ | . . O . . X . . X X B O X O O X O . . |
$$ | . . . O . . . . . , X O X O X X O . . |
$$ | . . . . . . . . . . X O O O O X X O . |
$$ | . . O . . . . . . . B O X X 6 O X O . |
$$ | . . . . . . . . . . X O 7 O O O X O . |
$$ | . . . . . . . . . . X O O O X X X O . |
$$ | . . . . . . . . . . X O X X X X O O . |
$$ | . . . X . . . . O O X O X O W X O O X |
$$ | . . . X O . . . O X . X O . O X O X . |
$$ | . . X O . O O O X X . . . . W X X X 1 |
$$ | . . X O . X X O X O . O O O O O O O 5 |
$$ | . . X O . . . X X O . . X X X X O . . |
$$ | . X O O O X . X . O X . . X . X O . . |
$$ | . X O , O X . . . O . . O X X O . . . |
$$ | . . X O O O X X X O . X O X O O . . . |
$$ | . X . X . O X . X O X . X . X O . . . |
$$ | . . X . . . . . X O . . . X O O . . . |
$$ ---------------------------------------[/go]


The marked stones are outside liberties, incidental to the problem/

Click Here To Show Diagram Code
[go]$$B continuation
$$ ---------------------------------------
$$ | . . . . . . . . X X O X 4 X X . X . . |
$$ | . . . X . . . . X O O O X X X X O O . |
$$ | . . O . . X . . X X B O X O O X O . . |
$$ | . . . O . . . . . , X O X O X X O . . |
$$ | . . . . . . . . . . X O O O O X X O . |
$$ | . . O . . . . . . . B O . 1 3 O X O . |
$$ | . . . . . . . . . . X O O O O O X O . |
$$ | . . . . . . . . . . X O O O X X X O . |
$$ | . . . . . . . . . . X O X X X X O O . |
$$ | . . . X . . . . O O X O X O W X O O X |
$$ | . . . X O . . . O X . X O . O X O X 2 |
$$ | . . X O . O O O X X . . . . W X X X O |
$$ | . . X O . X X O X O . O O O O O O O O |
$$ | . . X O . . . X X O . . X X X X O . . |
$$ | . X O O O X . X . O X . . X . X O . . |
$$ | . X O , O X . . . O . . O X X O . . . |
$$ | . . X O O O X X X O . X O X O O . . . |
$$ | . X . X . O X . X O X . X . X O . . . |
$$ | . . X . . . . . X O . . . X O O . . . |
$$ ---------------------------------------[/go]


White takes first

Click Here To Show Diagram Code
[go]$$W White to play
$$ ---------------------------------------
$$ | . . . . . . . . 4 1 8 X 6 X X 9 X 7 . |
$$ | . . . X . . . . X O O O X X X X O O . |
$$ | . . O . . X . . X X B O X O O X O . . |
$$ | . . . O . . . . . , X O X O X X O . . |
$$ | . . . . . . . . . . X O O O O X X O . |
$$ | . . O . . . . . . . B O X X . O X O . |
$$ | . . . . . . . . . . X O . O O O X O . |
$$ | . . . . . . . . . . X O O O X X X O . |
$$ | . . . . . . . . . . X O X X X X O O 5 |
$$ | . . . X . . . . O O X O X O W X O O X |
$$ | . . . X O . . . O X . X O . O X O X . |
$$ | . . X O . O O O X X . . . . W X X X 2 |
$$ | . . X O . X X O X O . O O O O O O O 3 |
$$ | . . X O . . . X X O . . X X X X O . . |
$$ | . X O O O X . X . O X . . X . X O . . |
$$ | . X O , O X . . . O . . O X X O . . . |
$$ | . . X O O O X X X O . X O X O O . . . |
$$ | . X . X . O X . X O X . X . X O . . . |
$$ | . . X . . . . . X O . . . X O O . . . |
$$ ---------------------------------------[/go]


White will always take a ko to prevent Black from connecting.


Edited diagram 2, voiding jlt's next comment
Author:  jlt [ Fri May 22, 2020 1:26 pm ]
Post subject:  Re: Tsumegos from real games
Knotwilg, you mistyped what you had in mind in diagram 2 since there are two :w2: on the board and :b7: on an intersection that is already occupied by a white stone.

Anyway I think that :w1: starting from your diagram 1 leads to a ko (this is what happened in my game), while :w1: in your diagram 3 is the correct move, White wins the semeai without needing to fight a ko.
Author:  jlt [ Tue May 26, 2020 11:42 am ]
Post subject:  Re: Tsumegos from real games
Problem #8: Black to play. Can Black save the marked stone?

Click Here To Show Diagram Code
[go]$$Bc Black to play
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . O . . . . . . . O O X . . . |
$$ | . O . B O . . . . , . . O X O X . . . |
$$ | O . O O X O . . . . . O . X O X . . . |
$$ | . O X X X . . . . . . . X . X X O . . |
$$ | . X X . X . . . . . . . . . . . . . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , O . . . . , . . . . . , . . . |
$$ | . . O O X . . . . . . . . . . . . . . |
$$ | . . X X . . . . . . . . . . . . O . . |
$$ | . . . . . . . . . . . . . . . . O X . |
$$ | . . . . . . . . . . . . . . . . O X . |
$$ | . . X . . . . . . . . . . . . . O X . |
$$ | . . . , O . . . . X . . X . . O X . . |
$$ | . . . O . . . O . . . . . . . O X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]
Author:  jlt [ Wed Jun 17, 2020 12:38 am ]
Post subject:  Re: Tsumegos from real games
Possible variation:

Click Here To Show Diagram Code
[go]$$Bc Black to play
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . 7 3 . . . . . . . . . . . . . . . . |
$$ | . 4 . . 5 O . . . . . . . O O X . . . |
$$ | . O 1 B O 6 . . . , . . O X O X . . . |
$$ | O 2 O O X O . . . . . O . X O X . . . |
$$ | . O X X X . . . . . . . X . X X O . . |
$$ | . X X . X . . . . . . . . . . . . . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |[/go]
Author:  jlt [ Wed Jun 17, 2020 12:48 am ]
Post subject:  Re: Tsumegos from real games
Problem #9. I was Black in this game. Between moves 50 and 130 I thought that I had killed the upper left corner. Probably White thought the same as well, as he didn't try to live. When he finally made an attempt at move 130, he didn't make the correct choice.

White to play and save the marked stones.

Click Here To Show Diagram Code
[go]$$Wc White to play and save the marked stones
$$ ---------------------------------------
$$ | . . . . . . . . X . . . . . . . X O . |
$$ | . . . . . . X X . X O . . . O X . O . |
$$ | . . . . X . O X X O O . O O O X X X . |
$$ | . . W W X . . O O , . . . X X X O X . |
$$ | . . . . . . O . X O . . X . X O O O . |
$$ | . . X X . X X O . . . . X X X X O . . |
$$ | . . . . . . . O . . . . X O O O . . . |
$$ | . . . . . . . . . . . . . . . . O . . |
$$ | . . . . . . X X O . . . X . O O X . . |
$$ | . . X X X . . O . , . O . X O X X . . |
$$ | . . X O . O . . . . . . O O X O . . . |
$$ | . . X O . O . . . . . . . O X O O X . |
$$ | . . O X . . . . . . . . X O X . X . . |
$$ | . . O . . . . . . . . O O X . X . . . |
$$ | . . . . . . . O X . O O X . . . . . . |
$$ | . . . O . . . . O O . X . X . O X . . |
$$ | . . . . O . O O X X O O X . . X . . . |
$$ | . . . O X X X X O X X . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]
Author:  Knotwilg [ Wed Jun 17, 2020 2:38 am ]
Post subject:  Re: Tsumegos from real games
Click Here To Show Diagram Code
[go]$$Wc White to play and save the marked stones
$$ ---------------------------------------
$$ | . . . . . . . . X . . . . . . . X O . |
$$ | . 1 . a . . X X . X O . . . O X . O . |
$$ | . . . . X . O X X O O . O O O X X X . |
$$ | . . W W X . . O O , . . . X X X O X . |
$$ | . b . . . . O . X O . . X . X O O O . |
$$ | . . X X . X X O . . . . X X X X O . . |
$$ | . . . . . . . O . . . . X O O O . . . |
$$ | . . . . . . . . . . . . . . . . O . . |
$$ | . . . . . . X X O . . . X . O O X . . |
$$ | . . X X X . . O . , . O . X O X X . . |
$$ | . . X O . O . . . . . . O O X O . . . |
$$ | . . X O . O . . . . . . . O X O O X . |
$$ | . . O X . . . . . . . . X O X . X . . |
$$ | . . O . . . . . . . . O O X . X . . . |
$$ | . . . . . . . O X . O O X . . . . . . |
$$ | . . . O . . . . O O . X . X . O X . . |
$$ | . . . . O . O O X X O O X . . X . . . |
$$ | . . . O X X X X O X X . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


Does :w1: make miai of A and B?
Author:  jlt [ Wed Jun 17, 2020 2:58 am ]
Post subject:  Re: Tsumegos from real games
Not sure.

Click Here To Show Diagram Code
[go]$$Wc
$$ ---------------------------------------
$$ | . . . . . . . . X . . . . . . . X O . |
$$ | . 1 . 3 4 . X X . X O . . . O X . O . |
$$ | . . . . X . O X X O O . O O O X X X . |
$$ | . . W W X . . O O , . . . X X X O X . |
$$ | . 2 . . . . O . X O . . X . X O O O . |
$$ | . . X X . X X O . . . . X X X X O . . |
$$ | . . . . . . . O . . . . X O O O . . . |
$$ | . . . . . . . . . . . . . . . . O . . |[/go]


and then?


This seems to lead to a ko
Click Here To Show Diagram Code
[go]$$Wc
$$ ---------------------------------------
$$ | . 8 9 . . . . . X . . . . . . . X O . |
$$ | 0 1 . 3 4 . X X . X O . . . O X . O . |
$$ | . 6 . 5 X . O X X O O . O O O X X X . |
$$ | . 7 W W X . . O O , . . . X X X O X . |
$$ | . 2 . . . . O . X O . . X . X O O O . |
$$ | . . X X . X X O . . . . X X X X O . . |
$$ | . . . . . . . O . . . . X O O O . . . |
$$ | . . . . . . . . . . . . . . . . O . . |[/go]


Katago suggests another move

Click Here To Show Diagram Code
[go]$$Wc
$$ ---------------------------------------
$$ | 9 . . . . . . . X . . . . . . . X O . |
$$ | 6 5 . 1 3 4 X X . X O . . . O X . O . |
$$ | . 7 . 8 X . O X X O O . O O O X X X . |
$$ | . . W W X . . O O , . . . X X X O X . |
$$ | . 2 . . . . O . X O . . X . X O O O . |
$$ | . . X X . X X O . . . . X X X X O . . |
$$ | . . . . . . . O . . . . X O O O . . . |
$$ | . . . . . . . . . . . . . . . . O . . |[/go]


It is really necessary for Black to block at :4:, otherwise a variation like this can happen:

Click Here To Show Diagram Code
[go]$$Wc
$$ ---------------------------------------
$$ | . . . . . . 8 . X . . . . . . . X O . |
$$ | . . . 1 3 5 X X . X O . . . O X . O . |
$$ | . 4 . . X 6 O X X O O . O O O X X X . |
$$ | . . W W X . 7 O O , . . . X X X O X . |
$$ | . 2 . . 9 . O . X O . . X . X O O O . |
$$ | . . X X . X X O . . . . X X X X O . . |
$$ | . . . . . . . O . . . . X O O O . . . |
$$ | . . . . . . . . . . . . . . . . O . . |[/go]
Author:  jlt [ Tue Nov 10, 2020 12:02 pm ]
Post subject:  Re: Tsumegos from real games
Problem #10, White to play. What is the status of the C10 group?

Click Here To Show Diagram Code
[go]$$Wc White to play
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . O . . O O . . . . . . . . O O O . . |
$$ | . . . . O X . X . . . O O O X O X . . |
$$ | X O O O X X . . . , . O X X X X . X . |
$$ | . X X . . . . . . . X O . . . X . . . |
$$ | . . X . X . . . . . . O O . X O O . . |
$$ | . O . . O X . X . X . O X X . O X . . |
$$ | . . O O O X . . . . X . . . O O . . . |
$$ | X . O X O O . O X X . . X X X O O . . |
$$ | . . O X O . O X X O . . . . . O X . . |
$$ | O O X X X . X O O O . . O O O O . X . |
$$ | . X X . . X . . X O O O X X X . . . . |
$$ | . . . X . X . X . O X X . . . . X . . |
$$ | . . X O O O O . O . . . . . X . . X . |
$$ | . . X O . . O . O . O O . . . . X . O |
$$ | . . X O X O X X . , X O . X O O X O . |
$$ | . . O O X X . . X . X O . X X O O . O |
$$ | . . . . X . . . . . . X X O X . . O . |
$$ | . . . . . . . . . . . . . . . . X O . |
$$ ---------------------------------------[/go]
Author:  jlt [ Thu Nov 12, 2020 1:37 pm ]
Post subject:  Re: Tsumegos from real games
Answer:

It's a ko.

Click Here To Show Diagram Code
[go]$$Wc
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . O . . O O . . . . . . . . O O O . . |
$$ | . . . . O X . X . . . O O O X O X . . |
$$ | X O O O X X . . . , . O X X X X . X . |
$$ | 2 X X . . . . . . . X O . . . X . . . |
$$ | 1 5 X . X . . . . . . O O . X O O . . |
$$ | 8 O 7 . O X . X . X . O X X . O X . . |
$$ | 3 6 O O O X . . . . X . . . O O . . . |
$$ | X 4 O X O O . O X X . . X X X O O . . |
$$ | . . O X O . O X X O . . . . . O X . . |
$$ | O O X X X . X O O O . . O O O O . X . |
$$ | . X X . . X . . X O O O X X X . . . . |
$$ | . . . X . X . X . O X X . . . . X . . |
$$ | . . X O O O O . O . . . . . X . . X . |
$$ | . . X O . . O . O . O O . . . . X . O |
$$ | . . X O X O X X . , X O . X O O X O . |
$$ | . . O O X X . . X . X O . X X O O . O |
$$ | . . . . X . . . . . . X X O X . . O . |
$$ | . . . . . . . . . . . . . . . . X O . |
$$ ---------------------------------------[/go]


White has local ko threats: capture A16 or capture F13.

In order to live, White just needs to ignore one ko threat and then can live with B10: after :w9: ko threat, :b10: responds, :w11: takes ko, :b12: ko threat, then White is alive (if Black a then White b).

Click Here To Show Diagram Code
[go]$$Wm11
$$ | X X X . . . . . . . X O . . . X . . . |
$$ | O O X . X . . . . . . O O . X O O . . |
$$ | a O O . O X . X . X . O X X . O X . . |
$$ | 1 X O O O X . . . . X . . . O O . . . |
$$ | X X O X O O . O X X . . X X X O O . . |
$$ | b 3 O X O . O X X O . . . . . O X . . |
$$ | O O X X X . X O O O . . O O O O . X . |
$$ | . X X . . X . . X O O O X X X . . . . |
$$ | . . . X . X . X . O X X . . . . X . . |[/go]


Move :w1: is interesting because go problems rarely teach us these kinds of moves. In most go problems, only one group is involved and we don't threaten to connect to another group before living locally.
Author:  jlt [ Thu Nov 12, 2020 2:20 pm ]
Post subject:  Re: Tsumegos from real games
Problem #11, White to play.

Click Here To Show Diagram Code
[go]$$Wc
$$ ------------
$$ . X . X . . |
$$ . X . . O . |
$$ X . . O . . |
$$ X . , X O . |
$$ X . . X O . |
$$ . . . O X . |
$$ . X . . X . |
$$ . . . . . . |[/go]
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