Black just played the marked stone... What's whites best attempt at saving his marked group? (Enjoy!;) Reuven
Tderz: Possible starting moves which come up to mind are:
White a, b, c, d and e.
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])
dia. [2]
It looks like a miscalculation for Wc, but could be used as
large scale attack on the black center group:
dia. [3]
yet White can continue with or c and separate black's group.
Not a success for Black, got only some white stones , but center group is cut-off and weak; the lower edge has a bad endgame.
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.
dia. [7]
at present dia. 1-3 look best, but comprise an error:
is answered by
-
and White has liberty problems.
Hence, one could try and leave out the liberty losing exchange
-
ind. [1]
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 is good enough.
dia. [11]
After 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 stuid mistakes here)
Black ends in sente and could make later a good endgame around x to z for capturing .
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?
dia. [12] another variation
The shape among those is alsi very suited for playing
.
(which is better? dia [11] or this [12]?).
Knowing that itself is not important helps in the decision to sacrifice it:
dia. [13] daydreaming - W's bubble bursts
If now White is squeezed to
, then Black is connected on top
but the are lost after
(not a, because Black would lose 2 stones after white b and the ko at c would only help White).
Already seeing this shape -
-
tells us that White played inefficiently here.
White should look for better options.
dia. [14] similar to dias 5-6
Yet, similar to dias 5-6, White could try again to
,
but again would fail after white miai of a and b.
dia. [15] compromise
White could compromise with black via to
.
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
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 ,
, Black must prohibit all connecting options to the left and takes away a liberty with
.
dia [17] common attacking point
The have 4 liberties left, technically the corner can be killed easily (made nakade, common shape) by
but in exactly how many moves?
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.
dia [22]
... after some ko threat by White
but beware of the later ko at d, hence perhaps e see dia [24] ...
dia [23] ko
... it became real ko against black.
=> Conclusion, I don't know the answer to this problem?
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 . White will have lost two fights and then perhaps the game.
dia [25] peaceful by black?
See Dieter's variant below of this no-risc ko (dia. [24]) for black, starting with the descent at (perhaps more stylish) and some moves later, eventually resulting in
.
Dieter's dia [26]: White can kill
Dieter: On the Long L-Group page, it is explained that the descent of can kill Black, if Black prevents the connection. Here, we indeed have to care about White's external liberties.
Dieter's dia [27]: White can kill ?
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.
Dieter's dia [29]: White can kill ? ( @
,
ko))
Dieter's dia [30]: White can kill ? ( @
,
takes ko)
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:
dia [33]: Dieter's question 2: ko
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.
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 is better technique (e.g. having a liberty more at a) than hane+connect, but I will check on this.
The ko does not seem so effective, because the
have lost liberties and are therefore a source of many ko threats - if not
more !:
reply to Dieter's question 2, dia [35]:
After Black hardly wants to sacrifice the Black stone below
.
Besides that any of the previous white moves -
could/should have been used for ko at
, a 2nd ko evolved, hence looking like double-ko.
Black can play c or d, I think it's similar.
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 preferrred a.
reply to Dieter's question 2, dia [37]:
White is already alive after . The miai of m-n gives one eye at either o or p.
reply to Dieter's question 2, dia [38]:
White could exchange for
for separating (Black replies, after all it's big), then attack at
. Black would not answer White a at b (the 3 stones are useless now), rather escape making eye-shape around
=
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.
dia. [41]
White plays here to avoid dia [40].
Black finds this result un-attractive, and might even prefer diagrams [8] to [11], where Black loses 7
(about 16 points, but white could lose
and black keeps the lower edge)), but in sente!
So, is dia [11] best for Black and therefore the fairest, most likely compromise?