Charming ancient problem

Bill Spight · #1

Here is a charming tsumego from the ancient Chinese book, Shiqing Lu.

Click Here To Show Diagram Code: [go]$$W White to play $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . X X X X . . . . . . . . | $$ | . . . . . . X O O O O X . . . . . . . | $$ | . . . , . . X O X , O X . X . , . . . | $$ | . . . . X . X O X X O X . . . X . . . | $$ | . . . X . O X O . . O X O O O X . . . | $$ | . . . . . . O . . X X O . . . . . . . | $$ ---------------------------------------[/go]

Enjoy!

Shaddy · #2

Mnemonic · #3

Horibe · #4

Shaddy wrote:

Horibe · #5

After lengthy staring...a tip of the hat to Shaddy...

tchan001 · #6

haha, shaddy, we studied this shiqinglu problem last august in one of our tsumego sessions in the L19 room.

Shaddy · #7

did we? wow, i had completely forgotten -but it seems i remembered the main idea, hehe

ez4u · #8

Mnemonic wrote:

Bill Spight · #9

Congratulations to the solvers. ez4u's answer is the most detailed and thorough.

I have a perspective that is a bit different, and adds something, I think.

Click Here To Show Diagram Code: [go]$$W White threatens to make an eye and kills two stones $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . X X X X . . . . . . . . | $$ | . . . . . . X O O O O X . . . . . . . | $$ | . . . , . . X O X , O X . X . , . . . | $$ | . . . . X . X O X X O X . . . X . . . | $$ | . . . X . O X O . . O X O O O X . . . | $$ | . . . . . . O . . B B O 1 a 2 . . . . | $$ ---------------------------------------[/go]

I have always thought of plays like :w1:

as threatening to make a eye. But there is another way to look at it, which is helpful here. :w1:

make a half eye at "a". :b2:

takes it away.

:w1:

also makes a potential half eye when the :bc:

stones are captured. But White needs two eyes to live. Where are the other eye and a half coming from?

Obviously, they have to come from capturing or killing the three other stones inside White's eye space. Just killing them is not enough, as that yields only one eye. But capturing three stones yields 1 1/2 eyes.

Click Here To Show Diagram Code: [go]$$W White prevents one eye $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . X X X X . . . . . . . . | $$ | . . . . . . X O O O O X . . . . . . . | $$ | . . . , . . X O X 3 O X . X . , . . . | $$ | . . . . X . X O X X O X . . . X . . . | $$ | . . . X . O X O . . O X O O O X . . . | $$ | . . . . . . O . . X X O 1 . 2 . . . . | $$ ---------------------------------------[/go]

White must be careful. If Black plays at 3, White can capture four stones, but the resulting four point square eye would only be a single eye, not an eye and a half. :w3:

prevents Black from taking away a potential half eye.

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

White must still be careful, as the two eyes are only potential. If White plays :w9:

before

or

, then he will make only 1 1/2 actual eyes when capturing one group of stones or the other. White must capture both at once to make two eyes.

Click Here To Show Diagram Code: [go]$$W Two eyes $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . X X X X . . . . . . . . | $$ | . . . . . . X O O O O X . . . . . . . | $$ | . . . , . . X O . O O X . X . , . . . | $$ | . . . . X . X O . . O X X X X X . . . | $$ | . . . X . O X O O O O X O O O X . . . | $$ | . . . . . . O . O . . O O . X . . . . | $$ ---------------------------------------[/go]

1 1/2 + 1/2 = 2 eyes.

Here is a variation for Black.

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

connects to prevent two separate eye spaces for White.

Click Here To Show Diagram Code: [go]$$B No nakade $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . X X X X . . . . . . . . | $$ | . . . . . . X O O O O X . . . . . . . | $$ | . . . , . . X O . O O X . X . , . . . | $$ | . . . . X . X O . . O X . . X X . . . | $$ | . . . X . O X O O . O X O O O X . . . | $$ | . . . . . . O . O 2 1 O O . X . . . . | $$ ---------------------------------------[/go]

However, the resulting zigzag four eye shape is alive. Black has no nakade to kill.

------

Endgame considerations are not really part of tsumego, but still of some interest, I think.

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

After

White is alive. Now the local temperature has dropped, and both players can play elsewhere.

Click Here To Show Diagram Code: [go]$$B Black plays first $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . X X X X . . . . . . . . | $$ | . . . . . . X O O O O X . . . . . . . | $$ | . . . , . . X O X O O X . X . , . . . | $$ | . . . . X . X O X X O X 3 5 1 X . . . | $$ | . . . X . O X O 2 6 O X O O O X . . . | $$ | . . . . . . O . 4 X X O O . X . . . . | $$ ---------------------------------------[/go]

Click Here To Show Diagram Code: [go]$$B Black captures 5 stones $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . X X X X . . . . . . . . | $$ | . . . . . . X O O O O X . . . . . . . | $$ | . . . , . . X O . O O X . X . , . . . | $$ | . . . . X . X O 8 . O X X X X X . . . | $$ | . . . X . O X O O O O X O O O X . . . | $$ | . . . . . . O . O . 7 O O 9 X . . . . | $$ ---------------------------------------[/go]

forces

, and then :b9:

captures five White stones.

Click Here To Show Diagram Code: [go]$$W White plays first $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . X X X X . . . . . . . . | $$ | . . . . . . X O O O O X . . . . . . . | $$ | . . . , . . X O X O O X . X . , . . . | $$ | . . . . X . X O X X O X . . . X . . . | $$ | . . . X . O X O 1 . O X O O O X . . . | $$ | . . . . . . O . . X X O O . X . . . . | $$ ---------------------------------------[/go]

saves the five stones.

Click Here To Show Diagram Code: [go]$$B One point Black sente $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . X X X X . . . . . . . . | $$ | . . . . . . X O O O O X . . . . . . . | $$ | . . . , . . X O X O O X . X . , . . . | $$ | . . . . X . X O X X O X 3 . 1 X . . . | $$ | . . . X . O X O O 4 O X O O O X . . . | $$ | . . . . . . O . 2 X X O O . X . . . . | $$ ---------------------------------------[/go]

Ignoring the plays on the left for convenience, Black has a one point sente on the right.

Click Here To Show Diagram Code: [go]$$B One point Black sente $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . X X X X . . . . . . . . | $$ | . . . . . . X O O O O X . . . . . . . | $$ | . . . , . . X O . O O X . X . , . . . | $$ | . . . . X . X O 6 . O X X . X X . . . | $$ | . . . X . O X O O O O X O O O X . . . | $$ | . . . . . . O . O . 5 O O . X . . . . | $$ ---------------------------------------[/go]

Charming ancient problem

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