why do tsumegos have exactly one solution?

[bayu]

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 . All other moves are not only inferior but can be refuted. In contrast to this, there are often various that will do the trick. There are exceptions to the unique , 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?

[EdLee]

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.

[Bill Spight]

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.

[DrStraw]

Sometimes the order of moves can be interchanged but I have only seen few problems where there are two totally different solutions.

[EdLee]

unlike Western chess problems.

Hi Bill,

What's the usual solution etiquette with Western chess problems ?
( Or Shogi, or Xiangqi problems ? )

[dfan]

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.

[Bill Spight]

Sometimes the order of moves can be interchanged but I have only seen few problems where there are two totally different solutions.

Right.

[RobertJasiek]

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.

[bayu]

Tsumego with non-unique (or non-existing) 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.

[asura]

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.

[dfan]

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.

[oren]

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.

[EdLee]

those are more for fun than for improving.

For some people, improving is a (big) part of the fun.

[Charlie]

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?

[Uberdude]

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:

$$B white to play and kill
$$ +---------------------------------------+
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . O X X X X X X X O . O . . . |
$$ | . . . . . O O O O O O O O O . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |

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.