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Tsumegos from real games http://lifein19x19.com/viewtopic.php?f=15&t=17076 |
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Author: | Harleqin [ Wed Sep 22, 2021 2:55 am ] |
Post subject: | Re: Tsumegos from real games |
I wanted to play at , and if black draws out the stones, you can build the eye. |
Author: | jlt [ Tue Oct 12, 2021 11:11 pm ] |
Post subject: | Re: Tsumegos from real games |
Problem #26, an endgame problem. I was White in that game. Both players missed a big endgame move, which one? Black to play.
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Author: | Harleqin [ Wed Oct 13, 2021 2:35 am ] |
Post subject: | Re: Tsumegos from real games |
I think this is a problem for White. If S19, then Black throws in and squeezes on the left before S18, which leaves White short of liberties for the squeeze. If Q18 first, then Black just lets himself get squeezed, but then O17 becomes a double atari. On the lower side, I think White could also go in at 'a', so Black should protect at 'b'. |
Author: | jlt [ Wed Oct 13, 2021 4:41 am ] |
Post subject: | Re: Tsumegos from real games |
@Harleqin: you got the correct but I think your doesn't work.
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Author: | Knotwilg [ Wed Oct 13, 2021 7:36 am ] |
Post subject: | Re: Tsumegos from real games |
Initially I saw the above sequence.
Then I realized White could change the order and think about saving everything. I don't think she can.
So it probably boils down to the initial sequence in reverse order anyway.
And I don't think Harleqin's move holds, but for different reasons.
Edit: I'm defeated by my own argument .... So how about:
Seems like seki But is it sente? That makes all the difference |
Author: | jlt [ Wed Oct 13, 2021 8:05 am ] |
Post subject: | Re: Tsumegos from real games |
You got it! The last diagram is best for White since White gets sente, while White takes gote in the first diagram. |
Author: | jlt [ Sun Nov 21, 2021 2:58 pm ] |
Post subject: | Re: Tsumegos from real games |
Problem #27, White to live. This is from a 2-stone handicap game. In the game I managed to live after a 50-move fight but there was a much simpler solution. Edit: after all, it seems that Black can kill, see kvasir's message below. So the problem doesn't work (or should be reformulated as "White to live or to find a good way to sacrifice").
Answer:
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Author: | jlt [ Tue Nov 23, 2021 3:21 pm ] |
Post subject: | Re: Tsumegos from real games |
Problem #28, White to play. Not exactly a life and death problem, but a problem related to the life and death status of a corner group. One of the forum members will recognize this position if he reads this.
In the game I didn't want to connect passively at "a", and I hesitated between "b" and "c". 1) If White plays "b", how does Black protect the corner group? 2) If White plays "b", can Black respond with F19? 3) If White plays "c", is it sente? Suppose that Black plays elsewhere, does White have a followup? |
Author: | kvasir [ Thu Nov 25, 2021 10:54 am ] |
Post subject: | Re: Tsumegos from real games |
jlt wrote: Problem #27, White to live. ... Answer: I was thinking along same lines but I have doubts.
When I put down the diagram it occurred to me that white could play and that looked like a very good move but it is not saving the dead stones.
White is still in the game but if it is about sacrificing then keeping sente is probably better.
I wondered about not playing anything at all but black seems to have a too easy time of that.
I am not sure these are the best variations, but I just don't see how white is escaping. This way also doesn't seem to allow an escape, at least I don't see the tesuji, because black is winning the capturing race even though white could potentially play something like a to e.
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Author: | jlt [ Thu Nov 25, 2021 11:31 am ] |
Post subject: | Re: Tsumegos from real games |
Hmmm... Thanks for your message. So the problem doesn't work, I overlooked in your diagram. |
Author: | kvasir [ Thu Nov 25, 2021 8:24 pm ] |
Post subject: | Re: Tsumegos from real games |
Problem #28 I always think this corner group is confusing. 1) I think lives without giving in sente.
2) Not sure what the question is. Normally it would be this way but it fails because of
But this is a ko. Black would normally not take this risk.
On this board I notice as I make the diagram that there is something afoot because winning the ko is not that much bigger for white than entering the side is for black.
This might be too difficult but it is really white's choice to go after the corner because white can play like this and could then probably win the ko if black doesn't defend.
3) Yep, it is a ko.
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Author: | jlt [ Sat Nov 27, 2021 12:45 am ] |
Post subject: | Re: Tsumegos from real games |
Further comments on problem #28. Question 1: The following move also protects, I don't know if it's better or worse than "a".
Question 3: the following sequence was played in the game.
at which point I wondered: should I throw-in at "a" or play at "b" first? If White plays "a", winning the ko is hard for White since White needs to make an approach at then win the ko B19.
If Black wants to win the ko, then Black doesn't need to answer the throw-in right away, can wait for the approach move before fighting the ko.
In the game, I played A15 which is forcing, and wondered whether I should continue at "a" or "c" (assuming I want to continue locally, which may not be the best choice).
A move at "c" can be ignored, and either player can choose later to convert the position into a seki or to throw-in and fight the ko. In the game I played "a", Black captured a stone:
After this the only way to continue for White would be to play "d" and fight the ko. However I made a mistake and blocked at "e" instead and Black lived by double ko...
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Author: | jlt [ Mon Dec 27, 2021 10:18 am ] |
Post subject: | Re: Tsumegos from real games |
Problem #29, White to play. What is the status of the black group O16?
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Author: | kvasir [ Mon Dec 27, 2021 10:50 am ] |
Post subject: | Re: Tsumegos from real games |
#29 I thought ko.
But this variation was hard to visualize and it looks like it could be seki when played out.
===EDIT This seki is actually just alive. Not sure about this now
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Author: | jlt [ Mon Dec 27, 2021 11:42 am ] |
Post subject: | Re: Tsumegos from real games |
Maybe try another move for ? |
Author: | kvasir [ Tue Dec 28, 2021 6:25 am ] |
Post subject: | Re: Tsumegos from real games |
jlt wrote: Maybe try another move for ? I found another move but the result seems to be the same. First black's bad defense
but it's seki from here
For example
Maybe it's all wrong because my head seems to get stuck when I work out that big eye thing |
Author: | jlt [ Tue Dec 28, 2021 7:02 am ] |
Post subject: | Re: Tsumegos from real games |
I think White can get a ko with the following L16 In more detail:
This variation kills without condition:
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Author: | jlt [ Sat Feb 12, 2022 1:30 am ] |
Post subject: | Re: Tsumegos from real games |
Problem #30, Black to play. What is Black's next move, and what is the status of the upper left corner? Nothing fancy, just something rather elementary that I didn't realize before.
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Author: | kvasir [ Sat Feb 12, 2022 9:40 am ] |
Post subject: | Re: Tsumegos from real games |
It doesn't look elementary to me at all. I thought maybe seki.
There is the annoying hane but it doesn't appear to work.
Then maybe there are many ways to get a seki. I thought the following didn't work...
but it is not clear that white doesn't have a shortage of liberties here.
or
Maybe seki is acceptable? |
Author: | jlt [ Sat Feb 12, 2022 11:16 am ] |
Post subject: | Re: Tsumegos from real games |
Katago sees this:
White can't block at a, otherwise Black b. Black gets a picnic ko: either it's a seki and Black gets a free move elsewhere, or Black kills White's corner. Black has local ko threats (take a white liberty). Hope this is correct. |
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