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| 9-point corner shape confusion http://www.lifein19x19.com/viewtopic.php?f=11&t=12057 |
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| Author: | jdl [ Fri Jul 17, 2015 10:36 am ] | ||
| Post subject: | 9-point corner shape confusion | ||
This came up in a game I'm playing. I already made my move, so you aren't spoiling anything. As white, I was worried that black could cause trouble (such as a ko) by playing at A. I played S1 just to be extra safe, since I'm ahead by a lot. If it was a close game though, I would hate to give away a free point. Can black do anything interesting here, or am I paranoid?
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| Author: | leichtloeslich [ Fri Jul 17, 2015 10:45 am ] |
| Post subject: | Re: 9-point corner shape confusion |
Quote: Can black do anything interesting here? I dont think so, since white has a guaranteed eye. |
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| Author: | jdl [ Fri Jul 17, 2015 10:52 am ] |
| Post subject: | Re: 9-point corner shape confusion |
White S1 in response to black A? If that's right then I think I see where I was going wrong in my reading. I kept ending up with a black ko in my head, but I don't think it's actually there. |
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| Author: | leichtloeslich [ Fri Jul 17, 2015 11:08 am ] |
| Post subject: | Re: 9-point corner shape confusion |
Quote: White S1 in response to black A? If you do that then I think black s3 can get a ko or seki. I would just simply make an eye, so black A - white s3. After that I dont see anything for black. |
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| Author: | jdl [ Fri Jul 17, 2015 11:16 am ] | ||
| Post subject: | Re: 9-point corner shape confusion | ||
Ok, thanks. This is what I was seeing in my head, thinking it was a ko, but it really isn't because of the double-atari.
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| Author: | Bill Spight [ Fri Jul 17, 2015 12:10 pm ] |
| Post subject: | Re: 9-point corner shape confusion |
Never mind. 
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| Author: | yoyoma [ Fri Jul 17, 2015 12:31 pm ] |
| Post subject: | Re: 9-point corner shape confusion |
jdl wrote: Ok, thanks. This is what I was seeing in my head, thinking it was a ko, but it really isn't because of the double-atari. I think  is a mistake, Black can take the ko, and next extend upwards from  (so a two step ko). Instead white should make an eye on the top side. Now if black starts a ko on the bottom, white is alive in double ko.
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| Author: | jdl [ Fri Jul 17, 2015 12:56 pm ] |
| Post subject: | Re: 9-point corner shape confusion |
yoyoma wrote: I think is a mistake, Black can take the koI'm not seeing the ko that you're referring to. B5 isn't on the board yet. |
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| Author: | yoyoma [ Fri Jul 17, 2015 1:37 pm ] |
| Post subject: | Re: 9-point corner shape confusion |
jdl wrote: yoyoma wrote: I think is a mistake, Black can take the koI'm not seeing the ko that you're referring to. B5 isn't on the board yet. Wow I hallucinated that one! |
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| Author: | Alexfrog [ Fri Jul 17, 2015 4:25 pm ] |
| Post subject: | Re: 9-point corner shape confusion |
yoyoma wrote: jdl wrote: yoyoma wrote: I think is a mistake, Black can take the koI'm not seeing the ko that you're referring to. B5 isn't on the board yet. Wow I hallucinated that one! Hehe, we've all done that sometimes. In this the original 9 point sarea in this thread is safe, but if itwere one smaller, a rectangular eight, without the space at R1, then you would indeed need to play inside. Otherwise your opponent could invade and get either a seki or ko depending on how you responded. |
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| Author: | leichtloeslich [ Thu Jul 23, 2015 1:56 am ] |
| Post subject: | Re: 9-point corner shape confusion |
Quote: I hallucinated that one you're obviously not alone. I often looked at this corner and thought "uhm, doesnt black have to defend?" I guess these are shapes where our seki/ko pattern recogition misfires because there's a forcing move inside and we can make that corner ko shape aroung the 1-1 point, but even with the forcing move the attacker cant get an eye while the defender already has one, therefore no seki or ko anywhere in this thread. |
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