OD1P - May 22 Problem / Solution

Sub-page of OD1PMay22Problem

Index of first moves

[Diagram]
Black To Play  

.. a at [1]

...b at [2]

...c at [3]

...d at [4]

...e at [5]

...f at [6] (Correct solution)


[1]

Black Plays at N18


[Diagram]
Black plays at N18  
[Diagram]
Black fails  

White connects, main black group is dead even if the three stones on left might escape.



[2]

Black Plays at P18

[Diagram]
Black plays at P18  

[3]

Black Plays at Q18

[Diagram]
Black plays at Q18  

Q18, Black dies in failure.

[Diagram]
Black Start  

Black lives only if White plays this sequence follishly to W10 allowing Blace to capture at a. White can play b as W4, W6, W8, or even W10 to connect to White's two stones and thus kill the main Black group even if allowing Black's few stones on left to escape if they can. The longer White delays in playing b after B3, the better for Black.

[Diagram]
Black Start  

signal9: I'm not 100% sure, but this looks pretty good to me.

[Diagram]
Black Start  

unkx80: Nah... this is a failure diagram.


[4]

Black Plays at Q19

[Diagram]
Black plays at Q19  
[Diagram]
Order?  

YongCao? I think should play B1 first, then B3.


[Diagram]
Black Dies  

PeiweiCao? Black dies:



[5]

Black Plays at P19

[Diagram]
Black plays at P19  

[6]

Black Plays at O19

[Diagram]
Black plays at O19  

Correct Solution

[Diagram]
Black Start  

PeiweiCao? Now White has two choices:

Gregory W4 at a or b. After either choice White must next choose whether to capture Black's two stones in the corner or four stones on the left leaving the other group to make the second eye for Black. In all scenarios, it seems to me that White will be better off after B1 to capture it and the two supporting stones and to allow Black to live have the second eye in the corner. This makes the White wall on the left solid with no cutting points.

[Diagram]
White Choice 1  

Black lives.

Gregory After B5 White can play either at W6 or B7 (in which case letting Black play at W6).

Or...

[Diagram]
White Choice 2  

PeiweiCao? One of the two blocks of White will be eaten, and Black lives.

[Diagram]
White Choice 2 (Continued)  

Jared: This could be called a "double sacrifice" set-up, with a "double-snapback-threat throw in"

PeiweiCao?: Consider white move 2 at p19 instead of m18, I believe that white p19 assures the death of the black corner.


[Diagram]
Black Start  

unkx80: If W2, then the tesuji of B3 and B5 should ensure life.


[Diagram]
Black Start  

Alexandros? Not a very good player here, but I think PeiweiCao?'s method fails to the following:

[Diagram]
B Black Start  

Then, as I read it, if black picks this path: (with move 3 filling in the liberty)

[Diagram]
Black Start  

unkx80: B5 at W8?

Gregory Yes, If Black plays B5 at W8 (of the previous diagram) then White has to choose between a and b to decide which group to capture and which to let live to make the second eye. The capture at a seems the obvious choice.

[Diagram]
Black Start  

Alexandros?: I'm not sure if it's cheating in a problem, but White could play W4 at B5 in that case, and run into the wall at the other end of the board. Of course, this goes beyond the bounds given for the problem, so it may be wrong...

unkx80: By the usual conventions in life-and-death, we assume that the rest of the board is empty, so feel free to extend the diagram as you wish, so this is not cheating.

For your question of W4 at B5, I leave it as an exercise: What is the gist of this problem? The tesuji has been mentioned on this page at least twice already...

Gregory If White plays W4 at B5 (of previouse diagram) then Black plays B5 at P18 for double atari to capture the two White stones when White saves the three stones in the corner. However since Black is open on the top this is not so good for White.


[Diagram]
Black Death?  

Boardwalk?: Doesn't W8 kill black. Allowing for the run to the other edge of course.

unkx80: B5 is a mistake, should be at W2.


[Diagram]
Correct Solution  

BluPian0: A tricky snapback to find. Thanks goes to Violence for helping me find the solution.

[Diagram]
While closes at top.  

Gregory In this variation on the solution of B1 at O19, after B7, White takes in corner with W8 leaving atari on the four Black stones forcing B9, so White can close the top with W10 if needed.


[Diagram]
Correct Solution?  

AVAVT: Hm... I doubt this is the proper solution. After W3 what would you do?


[Diagram]
Correct Solution?  

AVAVT: Oh Black can still live. I didn't notice B4.



OD1P - May 22 Problem / Solution last edited by Endo on February 18, 2011 - 14:57
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