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5k vs 5k and three question review
http://www.lifein19x19.com/viewtopic.php?f=4&t=17207
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Author:  Fllecha [ Thu Jan 16, 2020 4:15 am ]
Post subject:  5k vs 5k and three question review

Hi all,

I played with white and I probably performed at least 4 stone below my usual level, cannot say why. I ask for a review basically on

1) General direction of play
2) The strange outcome on the lower left corner. In the counting phase we cannot say for sure if it was seki or dead and there is some (apparentely) infinte ko if you try to reduce the shape to a well known dead 4-bent in the corner.
3) How to handle the upper right corner against that reduction.

Thanks as usual.


Author:  Bill Spight [ Thu Jan 16, 2020 4:28 am ]
Post subject:  Re: 5k vs 5k and three question review

Hi, Fllecha,

Happy New Year! :D

Fllecha wrote:
2) The strange outcome on the lower left corner. In the counting phase we cannot say for sure if it was seki or dead and there is some (apparentely) infinte ko if you try to reduce the shape to a well known dead 4-bent in the corner.


The bottom left is a standard Bent Four. White is dead by Korean and Japanese rules, and probably by area rules, I did not check. The ko is characteristic of Bent Four. :) Black takes first, and is presumed to be able to win it under Japanese and Korean rules. By area rules (Chinese and others) before making the ko Black eliminates all of White's ko threats for free. On rare occasions Black cannot do so, and then may leave the Bent Four as seki.

Author:  EdLee [ Thu Jan 16, 2020 11:00 am ]
Post subject: 

Hi Fellecha,

For (2), BentFourInTheCornerIsDead.

Author:  Mike Novack [ Wed Mar 11, 2020 3:22 pm ]
Post subject:  Re: 5k vs 5k and three question review

Sorry I did not see this earlier. I think Fllecha and opponent aren't seeing HOW this becomes "bent four"

"2) The strange outcome on the lower left corner. In the counting phase we cannot say for sure if it was seki or dead and there is some (apparentely) infinte ko if you try to reduce the shape to a well known dead 4-bent in the corner. "

No Fllecha, there is no ko involved. You are imagining black has to play C1 or A3 to get to bent four? No, black would play A1 first and THEN C1 or A3.

Author:  ez4u [ Wed Mar 11, 2020 4:12 pm ]
Post subject:  Re: 5k vs 5k and three question review

Do you understand that you killed your own stones when you played C2 in the game? At that point White is alive in seki. C2 fills an important internal liberty and creates a dead shape.

Author:  mhlepore [ Wed Mar 11, 2020 4:46 pm ]
Post subject:  Re: 5k vs 5k and three question review

I've added a few comments to the sgf file. Basically, I think your direction of play is pretty good. Try not to leave unfinished shapes. Try to make yourself safe first. Tactically, you can sharpen your play up a bit.

edit: I just saw ez4u's comment on the lower left and he's correct. you can have seki as he describes with no risk, or you can go for ko, but seki probably safer.



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