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why do tsumegos have exactly one solution?
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Author:  bayu [ Tue Dec 13, 2016 2:28 pm ]
Post subject:  why do tsumegos have exactly one solution?
In a tsumego, does the player/color going first has a name? A tori and uke concept might come in handy when discussing. I call it black in this post.

In most tsumego problems, there is exactly one correct move for :b1:. All other moves are not only inferior but can be refuted. In contrast to this, there are often various :b3: that will do the trick. There are exceptions to the unique :b1: , but in contrast to game positions where there is often more than one way to kill or live (one might be best of course, because of number of points or ko-threats or follow up endgame etc), the exceptions in problem selection are quite rare.

Is there some pedagogic concept or another good reason behind this?
Author:  EdLee [ Tue Dec 13, 2016 3:13 pm ]
Post subject: 
Hi bayu,

One guess: if a shape has more than one correct first move,
it seems it's easier than a similar-level problem -- all else being equal -- that requires a unique first move. :)
Author:  Bill Spight [ Tue Dec 13, 2016 3:41 pm ]
Post subject:  Re: why do tsumegos have exactly one solution?
With tsumego I was not aware of any rule about having a unique first play. OC, there is a certain aesthetic appeal to that, but I do not know of any general sense that a problem with more than one solution is "cooked", unlike Western chess problems.
Author:  DrStraw [ Tue Dec 13, 2016 3:51 pm ]
Post subject:  Re: why do tsumegos have exactly one solution?
Sometimes the order of moves can be interchanged but I have only seen few problems where there are two totally different solutions.
Author:  EdLee [ Tue Dec 13, 2016 4:00 pm ]
Post subject: 
Quote:
unlike Western chess problems.
Hi Bill,

What's the usual solution etiquette with Western chess problems ?
( Or Shogi, or Xiangqi problems ? ) :)
Author:  dfan [ Tue Dec 13, 2016 4:07 pm ]
Post subject:  Re:
EdLee wrote:
What's the usual solution etiquette with Western chess problems?

In general, there is supposed to be a unique winning (or drawing, if that's the goal) move at every step until a obvious winning position is reached. The lack of this property is regarded as a clear flaw, and with certain classes of problems means that the problem is considered qualitatively broken, necessitating a fix restoring the uniqueness property before it can be presented again.
Author:  Bill Spight [ Tue Dec 13, 2016 4:50 pm ]
Post subject:  Re: why do tsumegos have exactly one solution?
DrStraw wrote:
Sometimes the order of moves can be interchanged but I have only seen few problems where there are two totally different solutions.


Right. :)
Author:  RobertJasiek [ Tue Dec 13, 2016 10:25 pm ]
Post subject:  Re: why do tsumegos have exactly one solution?
Some creators of tsumego problems seem to think that each problem must have exactly one correct first move to be called a "problem" in their opinion.

When I create tsumego problems, they can have zero, one, several or (rarely) all correct first moves because this agrees to the reality in our games. The uncertainty about the number of correct first moves increases the difficulty of solving them on average.

If there always is a solution, then the case of zero correct first moves is not trained at all - bad! Even the classics admitted this by providing (only?) one infamous problem with tenuki / pass / ko threat being the only correct first moves.
Author:  bayu [ Wed Dec 14, 2016 3:58 am ]
Post subject:  Re: why do tsumegos have exactly one solution?
Tsumego with non-unique (or non-existing) :b1: exist. I don't think they're taboo, just so rare that I suspect some cultural background might be lurking. But maybe not.

For our chess players: do problems of the form "mate in 3" play a role in learning chess? So far I considered those an artform per se. And people try to solve them because they prefer it to crosswords, not because they want to get better at playing chess.
Author:  asura [ Wed Dec 14, 2016 4:16 am ]
Post subject:  Re: why do tsumegos have exactly one solution?
bayu wrote:
For our chess players: do problems of the form "mate in 3" play a role in learning chess? So far I considered those an artform per se. And people try to solve them because they prefer it to crosswords, not because they want to get better at playing chess.

A chess problem with "mate in 3" might be very easy (too easy) if you would change it to "mate in 4". So it is not an artform but serves the purpose to get better in chess (like tsumego for getting better in go).

There are some artform problems in chess like "how can you reach this position from the intitial position in 7 moves", those are more for fun (imho) than for improving.
Author:  dfan [ Wed Dec 14, 2016 8:29 am ]
Post subject:  Re: why do tsumegos have exactly one solution?
bayu wrote:
For our chess players: do problems of the form "mate in 3" play a role in learning chess? So far I considered those an artform per se. And people try to solve them because they prefer it to crosswords, not because they want to get better at playing chess.

Mate-in-N problems are generally considered more of a separate art than training material (often the positions are very artificial, as you know), but I've seen some teachers suggest them as a way of training calculation (reading). Usually endgame studies are preferred for this, though; their techniques are much more often applicable to actual games.
Author:  oren [ Wed Dec 14, 2016 9:59 am ]
Post subject:  Re: why do tsumegos have exactly one solution?
tsumeshogi are supposed to have just one correct move and also have no extra pieces than needed.

I think tsumego has some similar concepts but doesn't go as far.
Author:  EdLee [ Wed Dec 14, 2016 10:01 am ]
Post subject: 
Quote:
those are more for fun than for improving.
For some people, improving is a (big) part of the fun. :)
Author:  Charlie [ Thu Dec 15, 2016 8:35 am ]
Post subject:  Re: why do tsumegos have exactly one solution?
Is it not the case that tsumego with multiple first moves still always have a best first move, when end-game tesujis and Ko threats are considered? Is this not the source of proverbial wisdom such as the preference for a move on the outside to one on the inside - presumably because a move on the outside reduces the cost of ignoring further moves in the sequence, thus abandoning the tsumego, should they be employed as Ko threats?

Can anyone post a tsumego were all the "solutions" (i.e. the sequences leading to life/death/seki) are truly 100% equivalent?
Author:  Uberdude [ Thu Dec 15, 2016 8:45 am ]
Post subject:  Re: why do tsumegos have exactly one solution?
Charlie, yes often when multiple moves work one is better. However sometimes it is not clear which pros and cons are better: for example is gaining 1 point better if the cost is leaving 3 more ko threats, or some bad aji for later? There's no such thing as a universal point to ko threat to aji exchange rate, though I dare say Robert Jasiek might try to find one ;-) As for tsumego with two truly equivalent solutions (and some clearly inferior ones), here's an easy one:

Click Here To Show Diagram Code
[go]$$B white to play and kill
$$ +---------------------------------------+
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . O X X X X X X X O . O . . . |
$$ | . . . . . O O O O O O O O O . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |[/go]

If you want a less trivial one I need to think a bit more.
Author:  Bill Spight [ Thu Dec 15, 2016 12:13 pm ]
Post subject:  Re: why do tsumegos have exactly one solution?
Click Here To Show Diagram Code
[go]$$B white to play and kill
$$ +---------------------------------------+
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . O X X X X X X X O . O . . . |
$$ | . . . . . O O O O O O O O O . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |[/go]


The only unique attack is on the point of symmetry.

Click Here To Show Diagram Code
[go]$$W Only one eye
$$ +---------------------------------------+
$$ | . . . . . . 2 . 3 1 5 . 4 . . . . . . |
$$ | . . . O . O X X X X X X X O . O . . . |
$$ | . . . . . O O O O O O O O O . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |[/go]


:w1: keeps Black from making two eyes. But Black can guarantee seki. :cool:
Author:  Go_Japan [ Thu Dec 15, 2016 2:59 pm ]
Post subject:  Re: why do tsumegos have exactly one solution?
RobertJasiek wrote:
Some creators of tsumego problems seem to think that each problem must have exactly one correct first move to be called a "problem" in their opinion.

When I create tsumego problems, they can have zero, one, several or (rarely) all correct first moves because this agrees to the reality in our games. The uncertainty about the number of correct first moves increases the difficulty of solving them on average.

If there always is a solution, then the case of zero correct first moves is not trained at all - bad! Even the classics admitted this by providing (only?) one infamous problem with tenuki / pass / ko threat being the only correct first moves.


Internetgoschool.com run by Guo Juan also does this. Basically, she presents real games for problems, so there are in her view "best" moves, but also cases where several moves work the same or where there is no local play and the correct play is to tenuki. I think that is much better way to study than always playing where there is one solution. As RobertJasiek said, in games, there are many times with multiple plays and sometimes with no solution to a local position and tenuki is best. This is especially important not to remove any potential aji for later in the game.
Author:  Calvin Clark [ Thu Dec 15, 2016 11:21 pm ]
Post subject:  Re: why do tsumegos have exactly one solution?
I think it depends on the author, the purpose of the problem and the context. Having only one correct solution helps a lot with self-study, whether or not you look at answers. The answer book can be shorter, too, so it's a convenience to authors. :)

But there are other ways. Mingjiu Jiang 7p presents his students with problems on the board and asks them: "first tell me the result." They are not supposed to just start putting down stones to see what happens. So the exchange frequently goes like this:

Mingjiu: First, tell Ame the result.
Student: I think black can kill.
Mingjiu: Okay, how many ways can black kill?
Student: Uh....

Then at some point if you do put down stones and you're not sure, you have to deal with the man himself. :oops: This is interactive teaching. He sometimes encouraged students to work together when studying problems, so they see more counters and refutations. He has a point. If you study alone, it's easy to get into the habit of optimistic reading.

In that style, often there was more than one solution and maybe one was really best all the time or maybe which one is is best would depend on the whole board position, just like in real games. I think it is good way, in the same way that fine wine is good. But few can live off of wine, so the water of conveniently contrived closed positions will have sustain us most of the time. :)
Author:  goPlayerJuggler [ Thu Jul 04, 2024 3:19 am ]
Post subject:  Re: why do tsumegos have exactly one solution?
Yesterday I started a discussion related to this on SL, because most of the tsumego there with multiple solutions have been marked as "unsound", which I don't really like.
https://senseis.xmp.net/?topic=15325

There's a reply from Unkx80 which I'd like to share here:
Quote:
in both Chinese and Japanese, there is a specific term for failed life-and-death problem constructions: 失题 (Simplified Chinese) / 失題 (Traditional Chinese/Japanese), literally "missed problem". This term is used when a problem has either (i) no solutions, or (ii) more than one solution.

In printed Chinese problem books, it is common to see a statement on the problem itself stating that "this is a "missed problem" with two solutions". I suppose this is the same for Japanese - I don't know the history, but I have a feeling that the Chinese Go community had imported the "missed problem" concept from the Japanese.

So my issue on SL seems to be, at least partly, an issue with terminology/translation from Chinese & Japanese; or a difference in Go culture between "Asia" and "non-Asia".
Author:  kvasir [ Thu Jul 04, 2024 4:18 am ]
Post subject:  Re: why do tsumegos have exactly one solution?
Tsumego doesn't have to have exactly one solution. There are many examples of problem collections that don't follow this pattern. That there are books, as was suggested, that will label such problems is evidence.

It is a matter of perspective if you wish to call problems that don't have any or have many good solutions "inconsistent", "abnormal", "unsound", "different", "missed" or something else. Though it does seem a bit pedantic to myself if the problem isn't otherwise unclear. Unclear tsumego can be infuriating though.
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