Chosei: Eternal life in the board game Go

A very rare eternal life (長生) position appeared recently in the 2013 Korean Baduk League.

Choi Cheolhan eternal life chosei 300x400 picture

Choi Cheolhan 9 dan laughing after his game ended in eternal life.

The game was played between Choi Cheolhan 9p (team SK Energy) and Ahn Seongjun 4p (team Jeongganjang) in the 5th round of the league, on June 29, 2013.

When it appeared on the board, Kang Hun 9p, who was the referee for the game, came and judged it to be a draw.

Eternal life

We call this situation eternal life (長生 – chosei in Japanese), because it creates an endless cycle of moves in which neither player can win unless they’re willing to give up on the local situation.

It’s similar to the sort of repeating cycle that can occur when there are several kos on the board, but more complicated because it consists of four moves. This kind of repetition voids the game and leads to a draw under the Japanese rules.

eternal life chosei picture

Eternal life: The moves starting with white A and ending at black D are the only good options locally, after which the situation is back where it started and the pattern repeats itself endlessly.

The diagram above shows the position near the end of Choi and Ahn’s game. Black just played at D and it’s white’s turn to play.

Right now black could live by playing at A, so white plays a throw-in there to prevent it. After white A, if black captures with C, he’ll die after white responds with B. So black’s best option is to play B himself.

After black B, white’s in atari, so he captures two stones with C, then black’s in atari and he captures two stones with D. Now we’re back where we started.

You can have a look at the game record to see the position in more detail, and you can also try a very similar Go problem below.

Ahn Seongjun vs Choi Cheolhan

Download SGF File (Go Game Record)

A first in Korean professional Baduk

Ahn Seongjun eternal life chosei 300x400 picture

Ahn Seongjun 4 dan after the eternal life game.

Eternal life has never been seen before in official games in Korea, so this will be recorded as the first eternal life game in the history of Korean Baduk.

Cho Hunhyun 9p, who’s one of the commentators on Baduk TV, said that in 50 years as a professional Go player he’d never seen this happen before in person.

In an interview after the game, Choi said, “I feel happy and honored to create eternal life in my game but, on the other hand, it’s a pity for my team that I wasn’t able to win the game as captain.”

Choi Cheolhan Yun Jihee eternal life chosei 550x412 picture

Choi Cheolhan and Yun Jihee, partners in Go and life.

Other instances of eternal life

According to Baduk (Dec 1993), a Go magazine in Korea, the first official game in which eternal life appeared was played in Japan. The game was played in the 49th Honinbo league, between Rin Kaiho 9p and Komatsu Hideki 8p, on September 02, 1993.

The game was nearly finished, and it was a very close ‘half point’ game. Neither player could afford give way to avoid the situation, and the game ended as a draw.

However, if this had happened in another tournament, such as the Ing Cup (which uses Ing Rules), it would have been regarded as a special type of ko, so the players would have had to find a ‘ko threat’ before repeating the cycle.

Rin Kaiho vs Komatsu Hideki

Download SGF File (Go Game Record)

Go Seigen once said, “eternal life only happens in one in a million games, so if it ever happens in one of your games, you should cook rice together with red bean and celebrate.” This is a quote from his memoirs.

The second official game in which eternal life appeared was played in a preliminary qualifying match for the 23rd Fujitsu Cup, between O Meien 9p and Uchida Shuhei 2p, on Sep 14, 2009.

Uchida Shuhei vs O Meien

Download SGF File (Go Game Record)

Other than the two games mentioned above, there have never been any other reports of eternal life in official games. So (if that’s true) Choi and Ahn’s game is the third official instance of eternal life in professional Go, and the first in Korean Baduk history.

A Go problem featuring eternal life

Here’s a classic Go problem that involves eternal life, to help you understand this kind of situation better.

ggg eternal life picture

Download the solutions as an SGF or PDF file.

Rarer than a triple ko

Games featuring a triple ko, or the quadruple ko, are extremely rare too. However, they still appear more often than eternal life does.

Last year there was a quadruple ko in a game between Gu Li 9p and Lee Sedol 9p, at the 17th Samsung Cup. I posted a commentary of the quadruple ko game at the time.

Congratulations to Choi and Ahn

As Go Seigen said, this is an event that should be celebrated and congratulated in the Go world.

Congratulations to Choi Cheolhan and Ahn Seongjun, who made this happen in real in life!

Their game will long be remembered as a very special scene in the long history of Go.

Kang Hun referee eternal life chosei 550x412 picture

Choi Cheolhan (left) and Ahn Seongjun create eternal life in the 2013 Korean Baduk League. Referee, Kang Hun (background), ruled the game to be a draw.

About Younggil An

Younggil is an 8 dan professional Go player with the Korean Baduk Association. He won the 'Prize of Victory of the Year' in 1998 for winning 18 consecutive pro games. After completing compulsory military service, Younggil left Korea to teach and promote the game Go overseas. Younggil now runs Younggil's Go School in Sydney, Australia and writes at Go Game Guru. You can find Younggil on Google+ and follow Go Game Guru on Facebook, Google+ or Twitter.

Comments

  1. Very interesting and spectacular. Thank you for showing the games and the problem, making this quite clear to us.

    The fact that such a position is rare makes it more or less acceptable that such a game is voided, but as a matter of principle I would prefer the rule that a board position may not be repeated. That applies to the normal ko, the triple and quadruple ko, and thus also to this eternal life. In fact, if such a ko rule would apply, then there is no eternal life at all: as in a ko position, the one who wins the “ko fight” wins this local position. If this procedure is what the Ing rules stipulate, I sympathise with them.

    Kind regards,
    Paul

  2. Anonymous says:

    It’s a superko : http://senseis.xmp.net/?Superko . What do you think about this rules ?

  3. Yes, superko simply and satisfyingly always resolves such rare situations in favor of one of the players. The game cannot end in a “no result”.

    For example, in the tsumego problem, under superko, White dies.

    And under superko, in the 3 “Eternal Life” games above, Ahn Seongjun, O Meien, and Rin Kaiho all can easily be seen to force their opponent to abandon the ko. Moreover, only in the O Meien game might a strong kyu player have trouble working out the win after O Meien’s opponent is forced (by superko) to abandon the ko.

  4. Augustin says:

    Hi,

    If the game was under Ing rules, who will win the ko?

  5. Luis Bolaños says:

    Hi,

    I have designed Stoical Go, a Go variant where all known forced Go cycles are impossible. It’s like Go, with the difference that, instead of normal ko rules, it’s illegal to make a capture immediately after an enemy capture. What do you think of this idea?

    http://senseis.xmp.net/?StoicalGo

    • “all known forced Go cycles are impossible [in Stoïcal Go]”
      DEAD WRONG.

      It is even stated that this eternal life situation can happen with these rules on your link !?!

      • Luis Bolaños says:

        Hikaru, I’ve checked all the forced Go cycles mentioned in Sensei’s Library and none of them is possible in Stoical Go.

        However, if you can find or construct a forced cycle in it, I’d really like to know about it.

        Also, it’s not stated anywhere on my link that this eternal life is possible. What is said is that it’s possible under a DIFFERENT rule suggested by another user.

  6. I’m glad there is no superko rule. Very cool game. Thanks for the writeup!

  7. Interestingly, Cho Hunhyun showed after the game that b could have gotten a seki instead with 77 at d18. He has to make a sacrifice at k18 after that though to make it work. What I didn’t get was if b missed that variation or prefered the draw. It seems to me that a seki would give b the better position, but I could be wrong on that, and maybe b was happy with a draw in any case, his opponent beeing Choi Cheolhan.

    • KiattiyosL says:

      If I were Black, I would choose the draw the moment I saw it. I would be able to boast of not losing to Choi Cheolhan all my life!

      …And that’s exactly why I’m not strong yet.

  8. Very cool :) Thanks for sharing!

  9. Malcolm says:

    Some questions for strong players:
    1) If Black opts for the seki spotted by Cho Hunhyun, would the game be favorable for White?
    2) I believe that with a superko rule the game is favorable for White. Without superko, was there a way earlier on in the game (say around move 39) for White to get a playable position and avoid the drawn game by chosei?

    @Myron: I don’t understand your comment. You seem to say the game would be good for Ahn Seonjun if there were a superko rule. However, move 87 is illegal with superko so Black has to make a move elsewhere, like a ko threat. Choi Cheolhan with white would ignore any ko threat and capture the whole corner, obtaining a superior position IMO.

    • Malcolm, I mistakenly thought Ahn was White. Sorry about that. So yes, with superko, Choi (White) forces Ahn (Black) to abandon the ko to capture the roughly 50(?) point corner for, as you say, “a superior position”.

    • An Younggil 8p says:

      Answers to Malcolm’s questions.
      1) If Black opts for the seki spotted by Cho Hunhyun, would the game be favorable for White?
      A: The game should be even. In that case, black needs to cut at K18, and it would help white a lot.

      2) I believe that with a superko rule the game is favorable for White. Without superko, was there a way earlier on in the game (say around move 39) for White to get a playable position and avoid the drawn game by chosei?
      A: There must have been so many possible options for both sides. It’s a lightning game, so they wouldn’t be able to consider many moves under the time pressure.

  10. happysocks says:

    Very interesting, thanks!

    Only bummer was seeing Go Seigen’s memoir is (apparently) not available in english. :(

  11. Eternal life has been known about since antiquity and appears in classic go texts like Gokyo Shumyo and Xuanxuan Qijing. We also have thousands of historical game records of go masters dating back centuries. How is it possible that it hadn’t occurred in a professional game prior to 1993? Or does that refer to first occurrences under modern rules?

    • An Younggil 8p says:

      There could be some unrecorded games, but we can’t see now if it’s happened long time ago or not. Therefore, we can say it’s third time in official games which we can see the game records.

  12. I hate the idea of the super ko the ruling of a game being a tie does not bother me as much as the super ko rule which limits play ability.

  13. But if both of the groups are alive, why not treat it as a seki and agree to not repeat that cycle of moves infinitely?

    • Younggil An says:

      That’s a good question. That could be possible, but it’s really rare to see, so they probably don’t think they need to change the rules.
      You can celebrate instead under the current rules. :)

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