Tsumego From Games 46 / Attempts

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yuito6d vs. plaza5d on kgs - 15/12/04 - move 111

[Diagram]
What's the best white shot at $$W?  

Black just played the marked stone... What's whites best attempt at saving his marked group? (Enjoy!;) Reuven


[Diagram]
Possible starting moves:  


Tderz: Possible starting moves which come up to mind are:
White a, b, c, d and e.

[Diagram]
dia. [1]  


Hence, Whites starts: I see that a and b, are miai, the black corner has more fighting liberties than the 5 (now 4) white dame. Continuing with a looks more promising:
(before screaming, look below [7]-[8])

[Diagram]
dia. [2]  


It looks like a miscalculation for Wc, but could be used as large scale attack on the black center group:

[Diagram]
dia. [3]  


yet White can continue with W3 or c and separate black's group.
Not a success for Black, got only some white stones white+circle, but center group is cut-off and weak; the lower edge has a bad endgame.

[Diagram]
dia. [4]  


Another variant seems to be in vain first ...
... black d and e (not f) seem miai ...

[Diagram]
dia. [5]  


W7=white+square, B8=B3

[Diagram]
dia. [6]  


I think ,a is now futile because of b;
and starting with b does not work because of Bc, Wa, Bd and White has damezumari problems.
White e and f are also quite unrelated to the semeai below in this diagram.

[Diagram]
dia. [7]  


at present dia. 1-3 look best, but comprise an error: W1 is answered by B2-B4 and White has liberty problems. Hence, one could try and leave out the liberty losing exchange W1-B4 ind. [1]

[Diagram]
dia. [8]  


[Diagram]
dia. [9]  


Not responding at a gives White tempo (sente) and avoids losing liberties:

[Diagram]
dia. [10]  


Now White considers playing h or b in order to destroy the eye-shape of the black center group, but that makes no sense as Black can connect at a or play i (if White a). Hence , now coming back safely to White g and capturing the black+circle is good enough.

[Diagram]
dia. [11]  

After W3 Black must find the right moment to play a or i or perhaps first in the center around m. Black a is big and honte and allows free play afterwards. (Hope I didn't make stupid mistakes here)

Black ends in sente and could make later a good endgame around x to z for capturing white+square.

It is sente because White a, black r, white i does not attack much Black's center group (having the ko at k, an 1/2 eye at c and space around m).

Is this compromise the most likely outcome?

[Diagram]
dia. [12] another variation  


The shape among those black+circle is also very suited for playing B4 .
(which is better? dia [11] or this [12]?).
Knowing that black+square itself is not important helps in the decision to sacrifice it:

[Diagram]
dia. [13] daydreaming - W's bubble bursts  


If now White is squeezed W1 to W5, then Black is connected on top
but the white+circle are lost after B6 (not a, because Black would lose 2 stones after white b and the ko at c would only help White).

Already seeing this shape W1-W3-W5 tells us that White played inefficiently here.
White should look for better options.

[Diagram]
dia. [14] similar to dias 5-6  


Yet, similar to dias 5-6, White could try again W1 to B8,
but again would fail after white miai of a and b.

[Diagram]
dia. [15] compromise  


White could compromise with black via W1 to W5.
This is a likely outcome. Both White and Black have connected their groups.
(if Wa, then Bb) Black will lose territory in the endgame around the x-points

[Diagram]
dia [16]  


In dia [1] I state something about the corner having more fighting liberties, but after 2nd thought, it does not seem so straightforward: After W1, W3, Black must prohibit all connecting options to the left and takes away a liberty with B4.

[Diagram]
dia [17] common attacking point  


The white+circle have 4 liberties left, technically the corner can be killed easily (made nakade, common shape) by W1 but in exactly how many moves?

[Diagram]
dia [18]  


[Diagram]
dia [19]  


Black has a 4-nakade with (5-3=2) 2 liberties + the ko evolving at a + sente. If we deduct 1 liberty for the sente from White's 4 liberties, we guess it's 3 vs. 3 liberties in ko.

[Diagram]
dia [20]  


[Diagram]
dia [21]  


... B3 and keeping ko a to the last moment

[Diagram]
dia [22]  


... after some ko threat by White

  • - perhaps on the black center group with c,

but beware of the later ko at d, hence perhaps e see dia [24] ...

[Diagram]
dia [23] ko  


... it became real ko against black.

Conclusion, I don't know the answer to this problem?

[Diagram]
dia [24] neglect ko threat on center group  


Black neglects the ko threat on the center group, because cutting is Gote for White and Black can start a new ko with B6. White will have lost two fights and then perhaps the game.

[Diagram]
dia [25] peaceful by black?  


See Dieter's variant below of this no-risk ko (dia. [24]) for black, starting with the descent at W3 (perhaps more stylish) and some moves later, eventually resulting in B10.


[Diagram]
Dieter's dia [26]: White can kill  

Dieter: On the Long L-Group page, it is explained that the descent of W1 can kill Black, if Black prevents the connection. Here, we indeed have to care about White's external liberties.

[Diagram]
Dieter's dia [27]: White can kill ?  
[Diagram]
unkx80's dia [28]: I don't know.  

Although I wrote the relevant section of long L-group, I do not think the liberties allow. --unkx80

That's shocking news unkx80 :-) Tderz I should absorb your columns better.

[Diagram]
Dieter's dia [29]: White can kill ? (W3 @ white+circle, B4 ko))  
[Diagram]
Dieter's dia [30]: White can kill ? (W5 @ white+circle, B6 takes ko)  
[Diagram]
Dieter's dia [31]: Two move approach ko, White to play a threat  

It's a two move approach ko for White. But two questions remain in my mind:

[Diagram]
dia [32]: Dieter's question 1: Black hane  

1) How about Black's aggressive answer at B2?

[Diagram]
dia [33]: Dieter's question 2: ko  

B8 starts a ko on the White group on a large scale. However, White seems to have a lot of internal threats. Still I think that Black may expect more of this than from the two move approach ko mentioned above.


[Diagram]
reply to Dieter's question 2, dia [34]:  


Tderz: reply to Dieter's question 2: ko? First, it seems to me now that Dieter's sagari white+square is better technique (e.g. having a liberty more at a) than hane+connect, but I will check on this.

The ko B1 does not seem so effective, because the black+square have lost liberties and are therefore a source of many ko threats - if not more !:

[Diagram]
reply to Dieter's question 2, dia [35]:  


After W7 Black hardly wants to sacrifice the Black stone below W1.
Besides that any of the previous white moves W1-W7 could/should have been used for ko at black+square, a 2nd ko evolved, hence looking like double-ko.

Black can play c or d, I think it's similar.

[Diagram]
reply to Dieter's question 2, dia [36]:  


... afterwards, astonishingly a and b seem to lead to the same (German "Zugumkehrung" = move inversion?) good result for white - notice that this seems better than just double ko. In first instance, I preferred a.

[Diagram]
reply to Dieter's question 2, dia [37]:  


White is already alive after W7. The miai of m-n gives one eye at either o or p.

[Diagram]
reply to Dieter's question 2, dia [38]:  


White could exchange W1 for B2 for separating (Black replies, after all it's big), then attack at W3. Black would not answer White a at b (the 3 stones are useless now), rather escape making eye-shape around B3=W3 or further.


Are we ready for conclusion? Is unkx's dia [28], the simple sagari-tesuji? making miai of killing the corner or connection the simple & best answer to this problem?
Rich: Ummm... doesn't that diagram show white one liberty short of survival?

Tderz: true, simple sagari [32],[33] or hane [16] are ruled out by unkx's [28],
so it's diagrams [12] leading to compromise [15] ?

unkx80: I still haven't studied this in detail... but I think diagram [17] may be still possible? Diagram [28] did not rule out [17].

Compromise dia [15] leads to a bad endgame on the lower side for black. Knowing that white in all variations seems able to connect somehow - and that also the connection of the black center group is at stake - Black should try to get sente and/or a good endgame on the lower side.

[Diagram]
dia. [39] different compromise  


[Diagram]
dia. [40] Black cuts off marked W  


Black cuts off marked white+circle

[Diagram]
dia. [41]  


White plays W1 here to avoid dia [40]. Black finds this result un-attractive, and might even prefer diagrams [8] to [11], where Black loses 7 black+circle (about 16 points, but white could lose white+square and black keeps the lower edge)), but in sente!

So, is dia [11] best for Black and therefore the fairest, most likely compromise?


Tsumego From Games 46 / Attempts last edited by 50.23.115.116 on January 25, 2015 - 22:49
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