About Hanezeki (2009; 2015)
The Problem from XuanXian Qijing
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: follows the book's solution, occupying an internal liberty of White's group in the corner. Black ends in sente, because White must give atari on Black's hane in order to convert the position into a seki. It was Harry again, who made apparent to us that Black's passive move inside the hanezeki might be somewhat sub-optimal. | |
///: : Playing in the corner, at , instead, would be much too indulgent, allowing White to cover the cut on the lower edge with a move at , again reaching the final position shown above. |
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This results in a loss of 20 points for White. |
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///: : Black cuts at , and eventually captures one of White's groups on the outside in a geta. His main group in the corner has three liberties left, so Black will capture first. White's stone on the first line is in atari, so the ladder starting with at , , would not work for White. |
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Black recaptures. |
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White must recapture, too, due to the atari on her single stone on the outside. |
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After Black's atari with , White connects at here; she does not need to play ko on the outside. But now, Black has a smaller eye than White, and will lose the semeai unconditionally. As a matter of course, at does not work, too, White will answer with . | |
///: : Finally, establishes the hanezeki in the corner, in sente. |
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Compared with the result of the book's solution, White has lost ten points of territory on the outside (, ). | |
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After White's oki of , Black cuts on the outside with , and eventually captures one of White's groups. at will not work, too, because is an atari that must be answered. White should have played at , letting Black get two eyes in the corner with . White unasked for Nobi adds two points to Black's gain, which is 22 points then. |
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Black's group has sufficient liberties left to give atari on White's corner group, with . | |
Finally, Black captures White's group in the corner. |
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We have 6 + 2 = 8 points for White, and 11 + 7 = 18 points for Black. This time, Black gained "only" ten points in the exchange, twelve points less than with his correct line of play. | |
///: : However, after White's atari of , playing Nobi with is not correct. Black will be unable to successfully reduce any of White's groups on the outside to less than three liberties. |
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After White's atari of , Black has the option of playing the Counter-atari of . A ko on the outside has developed, but Black has the internal ko-threat of , so the ko is advantageous for him. |
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If White plays oki with , Black re-captures the ko, and White will have difficulties in finding a ko-threat that is large enough to compensate for her forthcoming loss in this semeai. If White connects at , instead, she will again suffer from Black living in the corner, with a move at . |
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///: : , and , turn the position into a seki. | |
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Again, Black has the choice between , and . |
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///: : Black might consider playing at , in order to create further cutting points in White's encirclement, but then he will end in gote in the corner. | |
Possibly (who knows?) the unexpected complications described above served as a kind of "booster detonation" for Inoue Dōsetsu Inseki to develop his masterpiece? Please be assured that there are many more, which we will not discuss in great detail here, just because this is a book about Igo Hatsuyōron, not about Gengen Gokyō. Please investigate this sudden outbreak of a long dormant volcano any further on your own. Several issues do play a role here, even with the "simple" kind of a hanezeki:
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: Jumping to , instead, would give a similar result. Finally, Black gets a seki in the corner with , in sente. |
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White lost four points of territory () on the outside, compared with the "classical" solution to this problem. |
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///: : Black immediately cuts at , and finally gets a geta in the centre. | |