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| One space corner extension invasion question http://www.lifein19x19.com/viewtopic.php?f=15&t=10472 |
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| Author: | oca [ Fri Jun 20, 2014 7:02 am ] |
| Post subject: | One space corner extension invasion question |
Hi, I saw in book an invasion that went like that : Then they talk about continuation for  at "a" and "b", but nothing is said about at "c"Trying for my self I went to this where white lives... Is my sequence correct ? Is there anything better for black (or for white) ? Any thought is welcome... |
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| Author: | DrStraw [ Fri Jun 20, 2014 7:06 am ] |
| Post subject: | Re: One space corner extension invasion question |
You have found the sequence which invalidates a black move at c |
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| Author: | Joaz Banbeck [ Fri Jun 20, 2014 7:08 am ] |
| Post subject: | Re: One space corner extension invasion question |
oca wrote: Black can start a ko like this. It is not easy for black to win because of his cutting points, but white has to win to live. |
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| Author: | DrStraw [ Fri Jun 20, 2014 7:12 am ] |
| Post subject: | Re: One space corner extension invasion question |
I don't think that this ko is even worth considering this early in the game as there is almost certain no threat big enough. Later in the game it may be a possibility. |
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| Author: | Joaz Banbeck [ Fri Jun 20, 2014 7:15 am ] |
| Post subject: | Re: One space corner extension invasion question |
DrStraw wrote: I don't think that this ko is even worth considering this early in the game as there is almost certain no threat big enough. Later in the game it may be a possibility. Agreed. So black probably tenukis at 3, and gets sente. Later, if white wants to repair it, he loses sente again: So black can leave it until he has good ko theats, and until he does, it is always going to be a pile of bad aji for white. |
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| Author: | oca [ Fri Jun 20, 2014 7:34 am ] |
| Post subject: | Re: One space corner extension invasion question |
Thanks, that's very interesting, variants with ko never comes into my mind... |
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| Author: | Uberdude [ Fri Jun 20, 2014 7:47 am ] |
| Post subject: | Re: One space corner extension invasion question |
oca, as you showed with your sequence connecting with 3 doesn't kill the corner. But even if it did (locally) you need to realize there is a big weakness in black's surrounding position with this cut of 4. If white captures part of black's wall he lives easily and escapes and destroys black's outside influence. Now it may be that black just about manages to keep everything together but at a minimum it means the ko Joaz showed is utterly unplayable for black as white has loads of local threats. That's why the book recommended connecting at a (now the cut of 4 above can be captured in a ladder, or if no ladder the fight is now much easier for black). It's a very common beginner (and not beginner!) mistake to only look at the opponent's problems and try to kill something, only for them to counterattack and exploit your weaknesses you overlooked and kill some of you instead. |
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| Author: | Uberdude [ Fri Jun 20, 2014 7:54 am ] |
| Post subject: | Re: One space corner extension invasion question |
Joaz Banbeck wrote: Actually white can tennuki after black 97 and he has elimnated in the ko in sente already (though at the cost of making a bad exchange as if black then captures the stone and white answers that capture made him stronger). If black doesn't want white to fix in sente he has to tenuki 96 but then if white crawls at 97 it takes a liberty and the cut at a becomes very serious. |
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| Author: | oca [ Fri Jun 20, 2014 8:00 am ] |
| Post subject: | Re: One space corner extension invasion question |
Uberdude wrote: oca, as you showed with your sequence connecting with 3 doesn't kill the corner. But even if it did (locally) you need to realize there is a big weakness in black's surrounding position with this cut of 4. If white captures part of black's wall he lives easily and escapes and destroys black's outside influence. Now it may be that black just about manages to keep everything together but at a minimum it means the ko Joaz showed is utterly unplayable for black as white has loads of local threats. That's why the book recommended connecting at a (now the cut of 4 above can be captured in a ladder, or if no ladder the fight is now much easier for black). It's a very common beginner (and not beginner!) mistake to only look at the opponent's problems and try to kill something, only for them to counterattack and exploit your weaknesses you overlooked and kill some of you instead.  Wow ... the ladder doesn't work... back to "Lessons In The Fundamentals Of Go" Chapter 1  ...
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| Author: | mitsun [ Fri Jun 20, 2014 1:12 pm ] |
| Post subject: | Re: One space corner extension invasion question |
Suppose B manages to eliminate all outside weaknesses. Playing "a" would still be the wrong -- B has a better attack. |
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| Author: | oca [ Fri Jun 20, 2014 2:54 pm ] |
| Post subject: | Re: One space corner extension invasion question |
Something like that ? seki I think... |
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| Author: | DrStraw [ Fri Jun 20, 2014 3:45 pm ] |
| Post subject: | Re: One space corner extension invasion question |
oca wrote: 9 at 10 creates a bulky 5, which is dead. |
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| Author: | cyclops [ Fri Jun 20, 2014 3:54 pm ] |
| Post subject: | Re: One space corner extension invasion question |
oca wrote:  is fine. It is not seki but w is dead.  is worse than a pass! It looses sente, it costs 1 pt and you destroy about 4 liberties of your dead group. Making it much deader, so to speak.edit: Ofcourse Joaz is right. is unnecessary most of the times.
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| Author: | Joaz Banbeck [ Fri Jun 20, 2014 3:59 pm ] |
| Post subject: | Re: One space corner extension invasion question |
cyclops wrote: ... is fine. It is not seki but w is dead. is useful only if white has stones around M18 or M19 and is threatening to connect out, or if there is a liberties race - in which case T16 must be played, followed by T19, and the throwin at S19. |
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| Author: | cyclops [ Fri Jun 20, 2014 4:16 pm ] |
| Post subject: | Re: One space corner extension invasion question |
edit: off topic, deleted |
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| Author: | ez4u [ Fri Jun 20, 2014 6:01 pm ] |
| Post subject: | Re: One space corner extension invasion question |
Joaz Banbeck wrote: ... is useful only if white has stones around M18 or M19 and is threatening to connect out, ...[snip]Surely in that case  will be played at 9, no? |
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| Author: | Bill Spight [ Fri Jun 20, 2014 6:04 pm ] |
| Post subject: | Re: One space corner extension invasion question |
Dies in gote.
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