Shusaku vs Shuwa

For lessons, as well as threads about specific moves, and anything else worth studying.
Post Reply
Akura
Dies with sente
Posts: 87
Joined: Thu Feb 10, 2011 7:37 am
Rank: EGF 5kyu
GD Posts: 0
Location: Munich, Germany
Has thanked: 341 times
Been thanked: 17 times

Shusaku vs Shuwa

Post by Akura »

Still studying "Invincible" I stumbled upon the following position in a two stone game against Shuwa:

Click Here To Show Diagram Code
[go]$$Wcm39
$$ ---------------------------------------
$$ | . . . . . . . . . . . . 3 2 4 . . . . |
$$ | . . . . . . . . . . . 5 . 1 X O O . . |
$$ | . . . . . X . . . . X . . O X X O . . |
$$ | . . O , O . . . . , . . . . . X O . . |
$$ | . . . . . . . . . . . . . O . . X O . |
$$ | . . . . . . . . . . . . . . O X X . . |
$$ | . . . . . . . . . . . . . O O O X . . |
$$ | . . . . . . . . . . . . 6 X O X X . . |
$$ | . . . . . . . . . . . . . . X X O . . |
$$ | . . . , . . . . . , . . . . . , O . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . O . . |
$$ | . . O . . . . . . . . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . O . . |
$$ | . . . X . . . . . , . . . . X , . . . |
$$ | . . . . . . X . . . . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


Now my question is, why does Black not just extend to the edge with :b40: ? If we continue just as in the game we get:

Click Here To Show Diagram Code
[go]$$Bcm40
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . 2 1 . . . . |
$$ | . . . . . . . . . . . . . O X O O . . |
$$ | . . . . . X . . . . X . . O X X O . . |
$$ | . . O , O . . . . , . . . . . X O . . |
$$ | . . . . . . . . . . . . . O . . X O . |
$$ | . . . . . . . . . . . . . . O X X . . |
$$ | . . . . . . . . . . . . . O O O X . . |
$$ | . . . . . . . . . . . . 3 X O X X . . |
$$ | . . . . . . . . . . . . . . X X O . . |
$$ | . . . , . . . . . , . . . . . , O . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . O . . |
$$ | . . O . . . . . . . . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . O . . |
$$ | . . . X . . . . . , . . . . X , . . . |
$$ | . . . . . . X . . . . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


This seems preferable for Black, since White's upper group has less eye shape and the threat for the corner is the same.
Top
amnal
Lives in gote
Posts: 589
Joined: Fri Apr 23, 2010 10:42 am
Rank: 2 dan
GD Posts: 0
Been thanked: 114 times

Re: Shusaku vs Shuwa

Post by amnal »

Black wants to prevent white connecting, and also wants sente.

Your suggested variation doesn't seem to be sente, as black doesn't actually have a followup to connect underneath - white could just answer a with b. Black does get b himself (or similar) to make the same threat whilst aiding his top group, but perhaps this is judged insufficient since white's atari lets him get away too easily and opens invasion points in that same top group.

Click Here To Show Diagram Code
[go]$$Bcm40
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . a 1 . . . . |
$$ | . . . . . . . . . . . b . O X O O . . |
$$ | . . . . . X . . . . X . . O X X O . . |
$$ | . . O , O . . . . , . . . . . X O . . |
$$ | . . . . . . . . . . . . . O . . X O . |
$$ | . . . . . . . . . . . . . . O X X . . |
$$ | . . . . . . . . . . . . . O O O X . . |
$$ | . . . . . . . . . . . . 2 X O X X . . |
$$ | . . . . . . . . . . . . . . X X O . . |
$$ | . . . , . . . . . , . . . . . , O . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . O . . |
$$ | . . O . . . . . . . . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . O . . |
$$ | . . . X . . . . . , . . . . X , . . . |
$$ | . . . . . . X . . . . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


So my guess is that black considers getting the extension in the centre to be worth damaging his group on the top.
Top
skydyr
Oza
Posts: 2495
Joined: Wed Aug 01, 2012 8:06 am
GD Posts: 0
Universal go server handle: skydyr
Online playing schedule: When my wife is out.
Location: DC
Has thanked: 156 times
Been thanked: 436 times

Re: Shusaku vs Shuwa

Post by skydyr »

amnal wrote:Black wants to prevent white connecting, and also wants sente.

Your suggested variation doesn't seem to be sente, as black doesn't actually have a followup to connect underneath - white could just answer a with b. Black does get b himself (or similar) to make the same threat whilst aiding his top group, but perhaps this is judged insufficient since white's atari lets him get away too easily and opens invasion points in that same top group.

Click Here To Show Diagram Code
[go]$$Bcm40
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . a 1 . . . . |
$$ | . . . . . . . . . . . b . O X O O . . |
$$ | . . . . . X . . . . X . . O X X O . . |
$$ | . . O , O . . . . , . . . . . X O . . |
$$ | . . . . . . . . . . . . . O . . X O . |
$$ | . . . . . . . . . . . . . . O X X . . |
$$ | . . . . . . . . . . . . . O O O X . . |
$$ | . . . . . . . . . . . . 2 X O X X . . |
$$ | . . . . . . . . . . . . . . X X O . . |
$$ | . . . , . . . . . , . . . . . , O . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . O . . |
$$ | . . O . . . . . . . . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . O . . |
$$ | . . . X . . . . . , . . . . X , . . . |
$$ | . . . . . . X . . . . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


So my guess is that black considers getting the extension in the centre to be worth damaging his group on the top.


My thought is that the descent does not threaten to connect to L17 or to wrap around the white group from the bottom. It also seems to increase the aji at O16 by limiting white's liberties more, though black still couldn't exploit it right away.
Top
Uberdude
Judan
Posts: 6727
Joined: Thu Nov 24, 2011 11:35 am
Rank: UK 4 dan
GD Posts: 0
KGS: Uberdude 4d
OGS: Uberdude 7d
Location: Cambridge, UK
Has thanked: 436 times
Been thanked: 3718 times

Re: Shusaku vs Shuwa

Post by Uberdude »

Another important question here is does the descent to p19 alter the status of the white corner group? The answer is no, but if black has p19, how would you answer black s14 to make sure the answer is still 'no'?
Top
keysersoze
Beginner
Posts: 16
Joined: Sun Sep 12, 2010 12:25 pm
GD Posts: 0
Been thanked: 2 times

Re: Shusaku vs Shuwa

Post by keysersoze »

With a hanging connection ;-)
Top
Akura
Dies with sente
Posts: 87
Joined: Thu Feb 10, 2011 7:37 am
Rank: EGF 5kyu
GD Posts: 0
Location: Munich, Germany
Has thanked: 341 times
Been thanked: 17 times

Re: Shusaku vs Shuwa

Post by Akura »

Thank you all - those are very good reasons.

@ Uberdude: I would play 'a'. Shusaku later played 'b':

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


But that doesn't depend on whether :b40: hanes or extends, does it?
Top
User avatar
SoDesuNe
Gosei
Posts: 1810
Joined: Wed Apr 21, 2010 1:57 am
Rank: KGS 1-dan
GD Posts: 0
Has thanked: 490 times
Been thanked: 365 times

Re: Shusaku vs Shuwa

Post by SoDesuNe »

http://senseis.xmp.net/?L2GroupWithDescent explains why the L+2 group is not unconditionally alive with this descent. Now there is the interesting Tsumego to figure out why the J+1 group remains unaffected ; )
Top
Akura
Dies with sente
Posts: 87
Joined: Thu Feb 10, 2011 7:37 am
Rank: EGF 5kyu
GD Posts: 0
Location: Munich, Germany
Has thanked: 341 times
Been thanked: 17 times

Re: Shusaku vs Shuwa

Post by Akura »

Aah, crap! Yet another reason, why I'm not the next Shusaku. Thank you for the link, SoDesuNe.
Top
Post Reply

Return to “Study Group”