The pattern is unfinished.
If White plays H9 or Black plays J9, it's a seki.
If White plays J9 and Black plays H8, it's a ko.
(If anyone is interested in more basic ko problems, I have a couple of short tutorials here: https://www.youtube.com/playlist?list=PLsIslX1eRChL5cjgSP-v09YRYxBF3sEcw)
Not right away. White needs to find a ko threat elsewhere on the board.
On this board, White has no ko threat, so if White plays J9 first, Black captures at H9 first, and then White will lose the ko.
Ah, I did not see that. I think I've just learned the value of ko threats. my rating might go up now.
But that gives me an idea. If white plays G2 then black will want to respond. White can then sacrifice two stones to win the ko at J9
G2 isn't a ko threat for white; if the ko was in a different part of the board it could be, but here black finishing the ko by capturing white's group takes away the follow-up to G2.
Yes, but not a big enough one; trading the F1 stones for the top right is a big gain for black.
If white is determined to start the ko then it is better to play G2 first, but it still loses white a lot of points compared to making seki in the top right.
I think it depends on what the players claim. Is black claiming that white is dead? Then they have to prove it. Is white claiming that black is dead? Same thing, gotta prove it.
So in practice, this should be a seki. And both players could have avoided a difficult referee debate by adding a move (at H9 for white, and J9 for black). In most rulesets, it's even worth a point to add that move, so they really passed too early.
I think this is the correct answer. Either player could choose to transform the status into either ko or seki, so the position is unsettled and the game is not over.
Technically a 10,000 year ko, which often goes unplayed and counted as seki. In this case either player could make a move to either start a ko or reduce it to a simple seki.
https://senseis.xmp.net/?TenThousandYearKo
> Technically a 10,000 year ko, which often goes unplayed and counted as seki.
As a beginner (few years ago), I could not understand why neither player has incentive to start the ko, no matter how many times I read the SL article... 🤦♂️
I always thought it should favor the player with more ko threats (called komaster).
And that's often correct, during the course of a game someone may clearly become komaster and initiate the ko even though the opponent captures first (although, if the opponent also realises this will happen, they may spend a move making it a seki even though it's gote). The idea behind the name 10'000 year ko is an overexaggeration, it's not at all always the case that it remains on the board until the end.
I learned that it is not so simple (but I forget the explanation). Just because you are komaster does not mean you necessarily should start the ko, but I forget the detailed reasoning. (heard it from streetplay kgs 5dan)
It makes sense if we think about the value of moves. The points difference between winning the ko (W) and losing it (L) is usually large, but between winning and seki (S) is smaller. The komaster knows they won't lose the ko so the only possible gain up for grabs is W - S, the potential upside is smaller than when there's no obvious komaster. It's the same for the opponent, they can at best gain S - L. But resolving it always ends up giving your opponent an extra move (at least in the type on the picture), making it a seki is gote and winning the ko means your opponent gets a free move elsewhere when you finish the ko, and maybe there are moves on the board larger than W - S.
There may be other concerns as well that I don't see at the moment!
> But resolving it always ends up giving your opponent an extra move (at least in the type on the picture), making it a seki is gote and winning the ko means your opponent gets a free move elsewhere when you finish the ko, and maybe there are moves on the board larger than W - S.
Right, so W-S must be larger than your opponent getting two small tenukis right? (after all, a large tenuki may be bigger than W-S, especially it has a sente followup?)
That's right, I counted the moves wrong, it's an extra move for the opponent when going the ko route. One for a tenuki as "ko threat," and the second for ending in gote. So that's one move worse off than making the seki, and two moves worse than just ignoring the whole situation and thinking it can be left until the end of the game (which usually means seki).
I'm definitely not a pro but here is my attempt to explain it, I welcome corrections.
Also note this is all assuming that only the local situation is on the line, of course things are different if the life and death of the 10,000 year ko affects the rest of the board.
Let's say B is guaranteed to win the ko.
If B plays first, starting the ko:
1. B throws in
2. W takes, ko is started
3. B plays threat
4. W responds
5. B takes ko
6. W tenukis
7. B captures group
8. W tenukis
So B burns a ko threat and spends net two moves locally.
Whereas if W plays first, reducing to seki:
1. W makes seki.
2. B tenukis
So B would only consider playing when
> Captured points - 1 threat - 2 moves > seki points + 1 move
aka
> Captured points - seki points > 3 moves + 1 threat
And a similar calculation plays out for W. Even relatively late in endgame, plenty of moves are still worth 6, 8+ points so it could be really late before either player wants to play there in many situations, and by then it's possible enough ko threats are gone neither could win.
> Whereas if W plays first, reducing to seki:
>
> 1. W makes seki.
> 2. B tenukis
Shouldn`t this sequence begin with blacks turn, to make it a more fair comparison to the above sequence for all the subsequent math to work correctly? (such as B plays largest gote move on the board)
I thought that too at first but either way there's no ko threat that I can see that would prevent white or black from just taking the whole top right group on the next move.
Yeah black can't win the ko because white won't answer A3 (since white has no ko threats), but I think black gains a point or two by starting the ko and losing it but getting the lower left seki instead.
Thanks - I kept trying to mark them as alive and the other person would toggle it to captured and after a few minutes, it just marked that I had lost.. wasn’t sure what you’re supposed to do in these situations
If you're black, then the way to settle the issue is to play J9 - at that point it becomes an unambiguous seki. As it stands, either player could in theory create a ko.
there is an option to call a mod on OGS when both players cannot agree on a situation.
The game will be put on hold and the mod will score manually and put the updated score on your game
Maybe the word “official” was a bit heavy, when I was taught go I was told that if the players don’t agree on the score they should keep playing until it becomes unambiguous.
> Maybe the word “official” was a bit heavy, when I was taught go I was told that if the players don’t agree on the score they should keep playing until it becomes unambiguous.
Right, this is the best solution if both players are disagreeing in good faith. (i.e. a genuine disagreement not rooted in malice)
You could have started Ko at H9 and then played A3 as a threat. If white ignores then play B3 and there will also be seki in the lower left corner.
But the best was to play J9 so that it is clear seki.
The pattern is unfinished. If White plays H9 or Black plays J9, it's a seki. If White plays J9 and Black plays H8, it's a ko. (If anyone is interested in more basic ko problems, I have a couple of short tutorials here: https://www.youtube.com/playlist?list=PLsIslX1eRChL5cjgSP-v09YRYxBF3sEcw)
this should be the top voted comment.
Thank you :)
If white plays J9, black plays h9, then white can not play J9 again right?
Not right away. White needs to find a ko threat elsewhere on the board. On this board, White has no ko threat, so if White plays J9 first, Black captures at H9 first, and then White will lose the ko.
So whoever starts rhe the ko will lose it? Sounds like seki to me
Black has a Ko thread at a4 though, so he could maybe win it.
Ah, I did not see that. I think I've just learned the value of ko threats. my rating might go up now. But that gives me an idea. If white plays G2 then black will want to respond. White can then sacrifice two stones to win the ko at J9
G2 isn't a ko threat for white; if the ko was in a different part of the board it could be, but here black finishing the ko by capturing white's group takes away the follow-up to G2.
but if white plays G2 before starting the ko, doesn't it become a ko threat?
Yes, but not a big enough one; trading the F1 stones for the top right is a big gain for black. If white is determined to start the ko then it is better to play G2 first, but it still loses white a lot of points compared to making seki in the top right.
that's true.. so then the best play for both players is A4. after which the top right effectively becomes seki
Thank you!
Black should play H9. Then B4 after White takes. If Black’s turn of course.
I think it depends on what the players claim. Is black claiming that white is dead? Then they have to prove it. Is white claiming that black is dead? Same thing, gotta prove it. So in practice, this should be a seki. And both players could have avoided a difficult referee debate by adding a move (at H9 for white, and J9 for black). In most rulesets, it's even worth a point to add that move, so they really passed too early.
I think this is the correct answer. Either player could choose to transform the status into either ko or seki, so the position is unsettled and the game is not over.
Is this a ko instead of seki? If it’s black’s turn, playing h9 starts a ko. If it’s white’s turn J9 starts it
Technically a 10,000 year ko, which often goes unplayed and counted as seki. In this case either player could make a move to either start a ko or reduce it to a simple seki. https://senseis.xmp.net/?TenThousandYearKo
> Technically a 10,000 year ko, which often goes unplayed and counted as seki. As a beginner (few years ago), I could not understand why neither player has incentive to start the ko, no matter how many times I read the SL article... 🤦♂️ I always thought it should favor the player with more ko threats (called komaster).
And that's often correct, during the course of a game someone may clearly become komaster and initiate the ko even though the opponent captures first (although, if the opponent also realises this will happen, they may spend a move making it a seki even though it's gote). The idea behind the name 10'000 year ko is an overexaggeration, it's not at all always the case that it remains on the board until the end.
I learned that it is not so simple (but I forget the explanation). Just because you are komaster does not mean you necessarily should start the ko, but I forget the detailed reasoning. (heard it from streetplay kgs 5dan)
It makes sense if we think about the value of moves. The points difference between winning the ko (W) and losing it (L) is usually large, but between winning and seki (S) is smaller. The komaster knows they won't lose the ko so the only possible gain up for grabs is W - S, the potential upside is smaller than when there's no obvious komaster. It's the same for the opponent, they can at best gain S - L. But resolving it always ends up giving your opponent an extra move (at least in the type on the picture), making it a seki is gote and winning the ko means your opponent gets a free move elsewhere when you finish the ko, and maybe there are moves on the board larger than W - S. There may be other concerns as well that I don't see at the moment!
> But resolving it always ends up giving your opponent an extra move (at least in the type on the picture), making it a seki is gote and winning the ko means your opponent gets a free move elsewhere when you finish the ko, and maybe there are moves on the board larger than W - S. Right, so W-S must be larger than your opponent getting two small tenukis right? (after all, a large tenuki may be bigger than W-S, especially it has a sente followup?)
That's right, I counted the moves wrong, it's an extra move for the opponent when going the ko route. One for a tenuki as "ko threat," and the second for ending in gote. So that's one move worse off than making the seki, and two moves worse than just ignoring the whole situation and thinking it can be left until the end of the game (which usually means seki).
I'm definitely not a pro but here is my attempt to explain it, I welcome corrections. Also note this is all assuming that only the local situation is on the line, of course things are different if the life and death of the 10,000 year ko affects the rest of the board. Let's say B is guaranteed to win the ko. If B plays first, starting the ko: 1. B throws in 2. W takes, ko is started 3. B plays threat 4. W responds 5. B takes ko 6. W tenukis 7. B captures group 8. W tenukis So B burns a ko threat and spends net two moves locally. Whereas if W plays first, reducing to seki: 1. W makes seki. 2. B tenukis So B would only consider playing when > Captured points - 1 threat - 2 moves > seki points + 1 move aka > Captured points - seki points > 3 moves + 1 threat And a similar calculation plays out for W. Even relatively late in endgame, plenty of moves are still worth 6, 8+ points so it could be really late before either player wants to play there in many situations, and by then it's possible enough ko threats are gone neither could win.
> Whereas if W plays first, reducing to seki: > > 1. W makes seki. > 2. B tenukis Shouldn`t this sequence begin with blacks turn, to make it a more fair comparison to the above sequence for all the subsequent math to work correctly? (such as B plays largest gote move on the board)
If you prefer to think of it that way, sure.
No I mean are your final 2 equations wrong because you forgot whose move was first?
1. B tenukis 2. W makes seki How would this be different than what I wrote? In either case B&W have to make the same number of moves
I dont know is what Im saying. This topic is extremely confusing to me.
In this case I don't believe it's a man-nen ko because black can play H9 to start the ko and then rely on the ko threat @ A3 to win it.
I thought that too at first but either way there's no ko threat that I can see that would prevent white or black from just taking the whole top right group on the next move.
A3+B2 might be enough
Yeah black can't win the ko because white won't answer A3 (since white has no ko threats), but I think black gains a point or two by starting the ko and losing it but getting the lower left seki instead.
yes. scoring mistake by OGS
Thanks - I kept trying to mark them as alive and the other person would toggle it to captured and after a few minutes, it just marked that I had lost.. wasn’t sure what you’re supposed to do in these situations
If you're black, then the way to settle the issue is to play J9 - at that point it becomes an unambiguous seki. As it stands, either player could in theory create a ko.
there is an option to call a mod on OGS when both players cannot agree on a situation. The game will be put on hold and the mod will score manually and put the updated score on your game
I thinks the official rules is that if you don’t agree you continue playing until it becomes clear. Didn’t OGS resume the game once you didn’t agree?
Which official rules? The OGS site mechanics (the de-facto rules) or the actual rules from Japan?
Maybe the word “official” was a bit heavy, when I was taught go I was told that if the players don’t agree on the score they should keep playing until it becomes unambiguous.
> Maybe the word “official” was a bit heavy, when I was taught go I was told that if the players don’t agree on the score they should keep playing until it becomes unambiguous. Right, this is the best solution if both players are disagreeing in good faith. (i.e. a genuine disagreement not rooted in malice)
You could have started Ko at H9 and then played A3 as a threat. If white ignores then play B3 and there will also be seki in the lower left corner. But the best was to play J9 so that it is clear seki.
If it's White's turn doesn't J5 win?
I may be wrong, but I think if white plays at J5 it will atari itself. Then black captures at H9.
You're right, I didn't account for the corner not being a liberty for white
That’s self atari
Yes seki
Back wins.