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Subtilities for ko threats handling http://www.lifein19x19.com/viewtopic.php?f=12&t=18572 |
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Author: | Gérard TAILLE [ Sat Jan 15, 2022 11:28 am ] |
Post subject: | Subtilities for ko threats handling |
I have very rarely seen problems dealing with the handling of ko threats. Here is one I built myself: Can you manage to read this endgame? What is the best sequence? Who will win the game ? BTW, from your experience, what is for you the level required to solve this problem by pure reading? |
Author: | kvasir [ Sun Jan 16, 2022 8:02 pm ] |
Post subject: | Re: Subtilities for ko threats handling |
Gérard TAILLE wrote: Can you manage to read this endgame? What is the best sequence? Who will win the game ? BTW, from your experience, what is for you the level required to solve this problem by pure reading? Not really. At least not in the right state of mind but probably could during a game. It is actually the wrong question to ask about "pure reading" because you mostly need to decide how to play it correctly and then you can figure that way out; I don't think it helps to start from the premise that it must be read out rather than deducted or just seen. If you decide black can fight to win the ko then it is not so hard to read that out but if this is inadequate you can consider alternatives. Conversely you could decide black can't or doesn't need to fight the ko and if that is inadequate try something else. Trying to brute force this without trusting your instincts is just too difficult to be practical. I think this is the solution but too long to not put in a hide block and maybe others like to think about it before reading replies. |
Author: | ez4u [ Mon Jan 17, 2022 1:54 am ] |
Post subject: | Re: Subtilities for ko threats handling |
Author: | John Fairbairn [ Mon Jan 17, 2022 1:55 am ] |
Post subject: | Re: Subtilities for ko threats handling |
Quote: I have very rarely seen problems dealing with the handling of ko threats. Rara avis, true, but there is one in captivity here, by Ichiriki Ryo. I don't know how you refer to other threads on L19, but you can find it by searching on "superhard" then choosing the thread "Japanese Title and League Scene." This reference today (2022-01-17) to Ichiriki happily coincides with him winning Game 1 of the Kisei against Iyama. |
Author: | ez4u [ Mon Jan 17, 2022 2:12 am ] |
Post subject: | Re: Subtilities for ko threats handling |
Author: | ez4u [ Mon Jan 17, 2022 2:25 am ] |
Post subject: | Re: Subtilities for ko threats handling |
Author: | kvasir [ Mon Jan 17, 2022 2:57 am ] |
Post subject: | Re: Subtilities for ko threats handling |
Author: | Gérard TAILLE [ Mon Jan 17, 2022 10:41 am ] |
Post subject: | Re: Subtilities for ko threats handling |
ez4u wrote: However(!), that means that Black cannot answer the ko capture in the upper left and must connect in the upper right. Luckily, Black 13 below is big enough to win. If White answers it, she has no ko threats left. If both sides capture on the left side, Black wins. Therefore the original "subtlety" in the thread name seems to be using the second largest ko threat first and keeping the largest in reserve. If Black starts with B5 instead of E7, he will lose the game. The various answers to this thread show me that such problem is really quite difficult. This is a very good point ez4u, but I still do not think the sequence above is the correct one because the threat b13 seems to big. Are you sure that white cannot improve this sequence? Anyway this sequence is a key point to understand the subtility I mentionned in the title. |
Author: | ez4u [ Mon Jan 17, 2022 3:57 pm ] |
Post subject: | Re: Subtilities for ko threats handling |
That's it for me. I will leave any further improvements to others. |
Author: | dany [ Tue Jan 18, 2022 4:27 am ] |
Post subject: | Re: Subtilities for ko threats handling |
Marcel Grünauer wrote: John Fairbairn wrote: Rara avis, true, but there is one in captivity here, by Ichiriki Ryo. I don't know how you refer to other threads on L19, but you can find it by searching on "superhard" then choosing the thread "Japanese Title and League Scene." That would be https://lifein19x19.com/viewtopic.php?p=259055#p259055. (You can find the link to the post on the post's top right, where it says "#3".) "The solution to the Ichiriki Problem A is apparently as follows - a void game." I think white can play better and win by half a point |
Author: | Gérard TAILLE [ Tue Jan 18, 2022 8:00 am ] |
Post subject: | Re: Subtilities for ko threats handling |
dany wrote: Marcel Grünauer wrote: John Fairbairn wrote: Rara avis, true, but there is one in captivity here, by Ichiriki Ryo. I don't know how you refer to other threads on L19, but you can find it by searching on "superhard" then choosing the thread "Japanese Title and League Scene." That would be https://lifein19x19.com/viewtopic.php?p=259055#p259055. (You can find the link to the post on the post's top right, where it says "#3".) "The solution to the Ichiriki Problem A is apparently as follows - a void game." I think white can play better and win by half a point Dany, could you give your best sequence for both ? |
Author: | Gérard TAILLE [ Tue Jan 18, 2022 8:31 am ] |
Post subject: | Re: Subtilities for ko threats handling |
John Fairbairn wrote: Quote: I have very rarely seen problems dealing with the handling of ko threats. Rara avis, true, but there is one in captivity here, by Ichiriki Ryo. I don't know how you refer to other threads on L19, but you can find it by searching on "superhard" then choosing the thread "Japanese Title and League Scene." This reference today (2022-01-17) to Ichiriki happily coincides with him winning Game 1 of the Kisei against Iyama. Thank you for the information John and thank you for the link Marcel. It is quite interesting but adressed to professionnal. I do not expect my problem being of professionnal interest ![]() |
Author: | Gérard TAILLE [ Tue Jan 18, 2022 3:30 pm ] |
Post subject: | Re: Subtilities for ko threats handling |
Marcel Grünauer wrote: John Fairbairn wrote: Rara avis, true, but there is one in captivity here, by Ichiriki Ryo. I don't know how you refer to other threads on L19, but you can find it by searching on "superhard" then choosing the thread "Japanese Title and League Scene." That would be https://lifein19x19.com/viewtopic.php?p=259055#p259055. (You can find the link to the post on the post's top right, where it says "#3".) Looking at the link mentionned I found this problem. My question is : what is the purpose of the three marked black stones? IOW, is the best sequence different with just the following position in which I deleted three black stones and three white stones: |
Author: | dany [ Tue Jan 18, 2022 4:42 pm ] |
Post subject: | Re: Subtilities for ko threats handling |
dany wrote: "The solution to the Ichiriki Problem A is apparently as follows - a void game." I think white can play better and win by half a point uh... I was slightly wrong white can play better and win by half a point...in another position |
Author: | dany [ Wed Jan 19, 2022 2:51 am ] |
Post subject: | Re: Subtilities for ko threats handling |
Gérard TAILLE wrote: Looking at the link mentionned I found this problem. My question is : what is the purpose of the three marked black stones? the purpose of these stones is to refute one of White's options in my position modification this secondary option becomes the solution |
Author: | Gérard TAILLE [ Wed Jan 19, 2022 7:30 am ] |
Post subject: | Re: Subtilities for ko threats handling |
dany wrote: Gérard TAILLE wrote: Looking at the link mentionned I found this problem. My question is : what is the purpose of the three marked black stones? the purpose of these stones is to refute one of White's options in my position modification this secondary option becomes the solution Thank you Dany, I understand but I am not able to find this white option showing how black could use her three marked stones to refute this option. Is it possible for you to show me this option or the corresponding link handling this option? |
Author: | dany [ Wed Jan 19, 2022 8:15 am ] |
Post subject: | Re: Subtilities for ko threats handling |
Gérard TAILLE wrote: Thank you Dany, I understand but I am not able to find this white option showing how black could use her three marked stones to refute this option. Is it possible for you to show me this option or the corresponding link handling this option? White's last move (move 18) from the original problem solution is not the best in the current position When you find the best white's move you find "how black could use her three marked stones" too |
Author: | Gérard TAILLE [ Wed Jan 19, 2022 4:10 pm ] |
Post subject: | Re: Subtilities for ko threats handling |
dany wrote: Gérard TAILLE wrote: Thank you Dany, I understand but I am not able to find this white option showing how black could use her three marked stones to refute this option. Is it possible for you to show me this option or the corresponding link handling this option? White's last move (move 18) from the original problem solution is not the best in the current position When you find the best white's move you find "how black could use her three marked stones" too With your help I think I have found a good sequence, providing Japonese rules are used (and not Chinese or AGA rules). Is it true? |
Author: | dany [ Wed Jan 19, 2022 5:44 pm ] |
Post subject: | Re: Subtilities for ko threats handling |
Gérard TAILLE wrote: With your help I think I have found a good sequence, providing Japonese rules are used (and not Chinese or AGA rules). Is it true? Yes, Japanese rules, 6.5 komi. What's the sequence? |
Author: | Gérard TAILLE [ Thu Jan 20, 2022 2:04 pm ] |
Post subject: | Re: Subtilities for ko threats handling |
dany wrote: Gérard TAILLE wrote: Thank you Dany, I understand but I am not able to find this white option showing how black could use her three marked stones to refute this option. Is it possible for you to show me this option or the corresponding link handling this option? White's last move (move 18) from the original problem solution is not the best in the current position When you find the best white's move you find "how black could use her three marked stones" too Though I now understand the meaning of the three marked stones I did not manage to find a white move better than the marked white stone in the diagram above. Does such white move really exist? |
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