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 Post subject: A double ko seki in a game between two professional 9-dans
Post #1 Posted: Thu Sep 03, 2020 7:42 pm 
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From the American Go Journal, vol. 12, nos. 3 & 4, (May/June/July/Aug 1977), p. 28.
Entitled "It Can't Happen"?!, it gives a game between two Japanese 9-dans, that ended in a double ko seki. It might be interesting to see that these odd situations can actually happen in real life games between professionals.

Event: Third Round of the Second Annual Kisei Title
Black: Miyamoto Naoki, 9-dan
White: Yamabe Toshiro, 9-dan
Komi: 5.5
Date: February 3, 1977

(Btw, I have a copy of GoGoD from 2012 (which I should update someday). It has several games from 1977-02-03, but does not appear to have this one. Perhaps it is listed under another date? Anyways, this means I had to input the game myself; let me know if anything does not seem right.)

The article does not say much, but just gives the final conclusion:
"275 moves. Game declared a draw under Nihon Ki-in rules because the 4 ko situation could not be resolved. Black must win both kos to win the game. The double ko seki on the left provides an infinite supply of ko threats and Black refuses to break the repetition of the full board pattern."

(For those as slow as me, the 4 kos seem to be at A8/A9, C8/C9, P3/P4, and S1/T1.)



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 Post subject: Re: A double ko seki in a game between two professional 9-da
Post #2 Posted: Fri Sep 04, 2020 2:33 am 
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Quote:
From the American Go Journal, vol. 12, nos. 3 & 4, (May/June/July/Aug 1977), p. 28.
Entitled "It Can't Happen"?!, it gives a game between two Japanese 9-dans, that ended in a double ko seki. It might be interesting to see that these odd situations can actually happen in real life games between professionals.


Quote:
(Btw, I have a copy of GoGoD from 2012 (which I should update someday). It has several games from 1977-02-03, but does not appear to have this one. Perhaps it is listed under another date? Anyways, this means I had to input the game myself; let me know if anything does not seem right.)


Technically, that's correct, but it's there in a different guise. There is an article in the GoGoD Encyclopaedia which mentions this game. I give below the first part of that article, up to the point where the above game is diagrammed.

Quote:
While obviously much rarer in play - once every 8,000 games according to a Nihon Ki-in estimate - it would be expected that quadruple kos are especially newsworthy. Surprisingly they are hard to pin down. The earliest we have (after the Windlass Ko above) is between Sekiyama Sendayu and Ito Tokujiro in Game 1826-09-15a. This too is a case of two double kos, which at the time is how Sekiyama described it - the phrase quadruple ko was applied much later, probably first by Kubomatsu Katsukiyo who discussed it in a book called it Hyakunin Ikkyoku (A Game apiece by 100 Players) in 1941. Even then, he didn't actually call it a quadruple ko, but simply said there were "four kos in all." Incidentally, Sekiyama sent the game to the Godokoro in Edo for "discussion", but no details of what happened next are extant. There is also a problem sometimes with distinguishing a qud ko from a triple ko. In game 1937-04-18a, one of the players, Kinoshita Keisho, remained convinced it was a quad ko, but others downgraded it to a triple, claiming only three of the kos actually mattered.

Our earliest example in modern play, and the next recorded in Japan after the Sekiyama-Ito example, is 1963-07-04b, Isogawa Masao against Hashimoto Yoshimi in the 1st Pro Best Ten. Though the game was annulled because of the cyclic repetition which neither player could afford to break, a commentary in Go Monthly Review of 1963-10 says White 252 was a mistake, missing a half point win. This was the first in "official" games in Japan, i.e. those domestic events counted for career record purposes. The second is usually quoted as being in the 1st Kisei 9-dan Section in 1977 between Yamabe Toshiro (White) and Miyamoto Naoki. We don't have that full game yet, but the final position was as follows:


and then a small portion of what followed:

Quote:
It is White to play. There is a double ko and two ordinary kos. If White takes at A, then after Black B, White C, Black takes back the ko. Or if White D, then after Black B, White C, Black takes back the ko. Black could not cede either ko in the upper left, otherwise he would have lost by half a point. Incidentally, this was incorrectly reported at the time in Kido as the first quad ko in official games. Not only is that wrong, the "second" quad ko reference was also wrong. There was in fact a quad ko in the Kansai Ki-in Oteai on 1974-10-30 between Hotta Yozo and Kubo Katsuaki. This was a truly remarkable game and it is amazing that it has been overlooked by Nihon Ki-in writers: it starts with tengen and then mirror go follows for 111 moves, and four identical Large Avalanche josekis take place!


However, things have moved on since then. Since 2012 (the date of your GoGoD copy) there have been about 8 or 9 quad kos in pro play, and Chen Zuyuan has published (in Chinese) an important book called Cyclic Kos 循环劫 (Shanghai 2014). He also gives a page to the above game.

GoGoD now has about or over 30 quad kos, and also now has two quintuple kos. Only one of those 5x kos features a pro, in a simultaneous game), and with both quad kos and quint kos there's also debate over whether they should really be called two double-kos or a double-ko and a triple ko. A debate which doesn't interest me.

What does interest me is why the game result was noted as being under "Nihon Ki-in rules" when Miyamoto was in fact not bound by those, as he was a Kansai Ki-in player. Also, the earlier Kansai Ki-in game from 1974 was never published until 1989. I'm not a conspiracy theorist, but I do wonder whether the KK played a part in suppressing the games. It was a time of intense and sometimes very bitchy KK-NK rivalry.

As to how to handle cyclic kos, usually a replay is called for. In 2004 there was an example of a pro making an illegal ko capture in a quad ko (and so losing, of course). I suspect that at least in part is behind pro dislike of a play-out superko rule.


This post by John Fairbairn was liked by 3 people: gowan, jaeup, tundra
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 Post subject: Re: A double ko seki in a game between two professional 9-da
Post #3 Posted: Fri Sep 04, 2020 10:07 am 
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tundra wrote:
(Btw, I have a copy of GoGoD from 2012 (which I should update someday). It has several games from 1977-02-03, but does not appear to have this one. Perhaps it is listed under another date? Anyways, this means I had to input the game myself; let me know if anything does not seem right.)

You could have found the game in the aeb collection (or in https://homepages.cwi.nl/~aeb/go/games/games/Kisei/Kis02/a.sgf)
but I did not have the date. Thanks, added.

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 Post subject: Re: A double ko seki in a game between two professional 9-da
Post #4 Posted: Wed Sep 09, 2020 12:01 pm 
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in that game position, i disagree with the bottom right 2 kos.
neither is really a ko fight, white can ignore both, and black can ignore both.
but yeah the two left kos are clearly a problem.

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 Post subject: Re: A double ko seki in a game between two professional 9-da
Post #5 Posted: Thu Sep 17, 2020 7:44 pm 
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I am also unsure of what, exactly, is going on in this position. But I think it may be something like this:

Ignoring the various kos, Black's current score, accounting for black stones that have been captured or are apparently dead on the board, is approximately 35 points. White's current score, including komi, is approximately 30.5 points. So Black seems to have a comfortable lead. (If White can win the two kos on the lower right, capturing another two Black stones, he could reduce Black's score by two points. Also, Q5 could become an eye, giving White another point. And this would eventually force Black to fill in at T6, reducing his score by yet another point. But it looks like Black would still be in the lead by 0.5 points, I believe.)

But in order to translate this lead into a win for Black, the game needs to terminate. Black can do this, if he can win both kos in the lower right, and fill both of them in. Then the only kos left on the board will be the two in the double ko seki. Apparently (I think), Japanese rules will then regard these stones as simply being in a seki. So the game will end and can be scored accordingly, with Black winning.

But of course, White will not be so cooperative. He will try to prevent Black from filling both kos, so that the game becomes either a quadruple or triple ko, leading to a draw.

So the two kos on the lower right actually are important, even if they do not affect the life and death status of any group. Black would like to end the ko fights in order to end the game, while White wants to maintain them indefinitely. And it turns out that White will get his way here.

Anyways, those are my thoughts. But I admit that Japanese rules in particular are difficult for me to understand. (Not to mention, I may have miscounted the scores above.) I'd be happy to hear other opinions, including any corrections.


Last edited by tundra on Sun Sep 20, 2020 11:12 am, edited 1 time in total.
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 Post subject: Re: A double ko seki in a game between two professional 9-da
Post #6 Posted: Sun Sep 20, 2020 2:14 am 
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tundra wrote:
Anyways, those are my thoughts. But I admit that Japanese rules in particular are difficult for me to understand. (Not to mention, I may have miscounted the scores above.) I'd be happy to hear other opinions, including any corrections.
Actually, the sgf file includes the exact comment explaining the situation. If two players split the two kos at the corner, White wins by 0.5 points. It means that, whenever White captures one ko, Black will defend it using the double ko as a ko threat. White cannot afford to yield both kos, so a quadruple ko draw occurs.

It is not such a difficult shape, and pros who are accustomed to play a close game often makes this type of draw (or no result). I remember Sedol Lee once was in a similar situation. Even though the game was played under the Chinese rule, it was essentially identical in that both players cannot yield small kos just because the game was so close, and they decided to use double ko as ko threats.

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 Post subject: Re: A double ko seki in a game between two professional 9-da
Post #7 Posted: Sun Sep 20, 2020 11:21 am 
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Well, my counting must be off somewhere. I still find Black in the lead by 0.5 points, even if he loses both kos on the right. Presumably I am missing a point somewhere on the board, either for White or against Black.

But I see that John Fairbairn has said above, that "Black could not cede either ko in the upper left, otherwise he would have lost by half a point." [Btw, should that read "lower right", rather than "upper left"?] So I will accept his official commentary.

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