Can a double sente position exist?

[Gérard TAILLE]

I do not see what harm when you keep simple wording as "sente for black" or "double sente"? It is a little mysterious for me.

The harm occurs when people play their "double sente" moves too early.

"Sente for black" is not so harmful. It's one-sided, it's not going to go away (usually!), so you can wait until later.

But "double sente": I need to play that right away, or else the other person will get it! (Not true, but a too-common misunderstanding.)

For example, here's a position from the Lee Sedol-Gu Li jubango, game 5.

$$Wc19 Position after move 37: 'a' is not sente $$ +---------------------------------------+ $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . a b . . . . . . . . . . . | $$ | . . O . . O . X . . . . . X . . . . . | $$ | . X . O . . . . . B . . . . . X X . . | $$ | . . . . . . . . . . . . . . . . . O . | $$ | . . X O O . . . . . . . X . O . O . . | $$ | . . . X . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . X . O . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . X . X . . . . . . . . . X O O O . | $$ | . . . . . . . . . . . . . . . X X O . | $$ | . . O . . . . . . . . . . . . . . X . | $$ | . . . . . . . . . . . . . . . . X . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . X . . . | $$ | . . . O . . . . . O . . O . . . . . . | $$ | . . . . . O . . . . . . . . . X . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ +---------------------------------------+

Click Here To Show Diagram Code

[go]$$Wc19 Position after move 37: 'a' is not sente $$ +---------------------------------------+ $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . a b . . . . . . . . . . . | $$ | . . O . . O . X . . . . . X . . . . . | $$ | . X . O . . . . . B . . . . . X X . . | $$ | . . . . . . . . . . . . . . . . . O . | $$ | . . X O O . . . . . . . X . O . O . . | $$ | . . . X . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . X . O . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . X . X . . . . . . . . . X O O O . | $$ | . . . . . . . . . . . . . . . X X O . | $$ | . . O . . . . . . . . . . . . . . X . | $$ | . . . . . . . . . . . . . . . . X . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . X . . . | $$ | . . . O . . . . . O . . O . . . . . . | $$ | . . . . . O . . . . . . . . . X . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ +---------------------------------------+[/go]

After black plays the marked stone, the top centre is now looking like black's territory, so a is "double sente". Back when I was a 5 kyu, I would have played white a immediately. And a lot of my kyu opponents would have obligingly answered at b. In fact, white ended up playing a much later, on move 112.

$$Wc19 *Now* it's double sente! $$ +---------------------------------------+ $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . a . . . . . . . . . X . . | $$ | . . O . . O . X . . . . . X . . . O . | $$ | . X . O . . . . . X X . . . . X X X O | $$ | . . O . . . . . . . O . . . . . . O . | $$ | . . X O O . . . . . . . X . O . O . . | $$ | . . O X . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . X . O . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . X . X . . . . . . . . . X O O O . | $$ | . . . . . X . . . . . . . . . X X O . | $$ | . X O . . X O . O . O O . . . . . X . | $$ | . . . . . X O . . O X O O . . . X . . | $$ | . X X O O X O . X O X X O X . . . . . | $$ | . O X X O X O X O . X X X X . X . . . | $$ | O . O O X X O X . O X O O X O X . . . | $$ | . O O X O O X X O . O X O . . X . . . | $$ | . . . X . O O O . . O X X . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ +---------------------------------------+

Click Here To Show Diagram Code

[go]$$Wc19 *Now* it's double sente! $$ +---------------------------------------+ $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . a . . . . . . . . . X . . | $$ | . . O . . O . X . . . . . X . . . O . | $$ | . X . O . . . . . X X . . . . X X X O | $$ | . . O . . . . . . . O . . . . . . O . | $$ | . . X O O . . . . . . . X . O . O . . | $$ | . . O X . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . X . O . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . X . X . . . . . . . . . X O O O . | $$ | . . . . . X . . . . . . . . . X X O . | $$ | . X O . . X O . O . O O . . . . . X . | $$ | . . . . . X O . . O X O O . . . X . . | $$ | . X X O O X O . X O X X O X . . . . . | $$ | . O X X O X O X O . X X X X . X . . . | $$ | O . O O X X O X . O X O O X O X . . . | $$ | . O O X O O X X O . O X O . . X . . . | $$ | . . . X . O O O . . O X X . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ +---------------------------------------+[/go]

Oops your example is quite different: in my position it does not matter which player will play her sente move, the result will be the same. In your example I see a huge difference when I compare the result after a white move and the result after a black move. I will never consider such position as double sente.

Why do you say in the last diagram is double sente position? I guess it is because you think that the ambiant temperature is small comparing to the threats involved by the sente moves. But assume temperature is high so that both players will firstly play several moves in the environment. At the moment temperature drops to a certain temperature t1 one player will decide to play locally. Are you sure it will be a sente move? And are you sure the opponent will be also able to play a sente move at this temperature t1?

Look at this provocative exmple

$$B $$ +---------------------------------------+ $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . X . . O . . . . . . . . . | $$ | . . O O O O O O X X X X X X X . . . . | $$ | . . . . . . . . . . . . . . . . . . . |

Click Here To Show Diagram Code

[go]$$B $$ +---------------------------------------+ $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . X . . O . . . . . . . . . | $$ | . . O O O O O O X X X X X X X . . . . | $$ | . . . . . . . . . . . . . . . . . . . |[/go]

Assume ambiant temperature t < 1.

$$B $$ +---------------------------------------+ $$ | . . . . . 6 4 5 . . . . . . . . . . . | $$ | . . . . . 2 X 1 3 O . . . . . . . . . | $$ | . . O O O O O O X X X X X X X . . . . | $$ | . . . . . . . . . . . . . . . . . . . |

Click Here To Show Diagram Code

[go]$$B $$ +---------------------------------------+ $$ | . . . . . 6 4 5 . . . . . . . . . . . | $$ | . . . . . 2 X 1 3 O . . . . . . . . . | $$ | . . O O O O O O X X X X X X X . . . . | $$ | . . . . . . . . . . . . . . . . . . . |[/go]

The sequence to is sente for black isn't it?
OC this position with ambiant temperature t < 1 is also sente for white?
Do you want really say it is a double sente position? I guess not. You will certainly say it is a "global" double sente position (meaning that take into account the temperature of the environment) but not a local double sente position.

[RobertJasiek]

Do you mean precision for the defintion itself or precision for the various evalutions (counts or move values)?

Conceptual precision. When we have said something for a specific kind of, in this case, double sente, namely for local double sente (its non-existence!), then it is impolite to speak about double sente more generally, showing some example and leaving the reader in doubt whether the example would be a counter-example to our theorem when, in reality, you mean some other concept: global double sente. (At other times, you have been more careful and polite about the matter.)

[Gérard TAILLE]

Do you mean precision for the defintion itself or precision for the various evalutions (counts or move values)?

Conceptual precision. When we have said something for a specific kind of, in this case, double sente, namely for local double sente (its non-existence!), then it is impolite to speak about double sente more generally, showing some example and leaving the reader in doubt whether the example would be a counter-example to our theorem when, in reality, you mean some other concept: global double sente. (At other times, you have been more careful and polite about the matter.)

"Double sente" is a concept which exists in the go language for a very long time. For sure that does not mean that the defintion of this term is very clear OC, but what is impolite is to define this wording in a different context, to decide your defintion is the only acceptable one, and in addition to conclude that this concept simply does not exist!
Those interested by your defintion will buy your book but as far as I am concerned I will continue to use this "double sente" as many other go players do .i.e. in an informal context, trying simply to have a common understanding. OC,I can try to differentiate "global double sente" to "local double sente". For me that's a quite interesting idea but because you claim that "local double sente" does not exist (though I understand it could not exist because the candidate positions for being local double sente are just unnamed!) such discussion cannot take place OC.

[RobertJasiek]

"Double sente" is a concept which exists in the go language for a very long time.

And as such often is a local gote, misleading everybody by the name "double sente" and by pretending bad values to be move values with the fake information on when to play in them. The centuries(?) of wrong teaching must be overcome. You are one of the few doing better by also studying good moments of local play.

to define this wording in a different context,

No. It is not a different context, but is the most frequent traditional context (appearing in old textbooks) with now added clarity. The less frequent traditional context of what later Bill Spight discussed and then I called global double sente (or double sente in the global positional context) was infrequently associated by amateur dans as "try to play there before the opponent but not too early" because of an awareness that the opponent would tenuki rather than accept a double sente fate.

to decide your defintion is the only acceptable one, and in addition to conclude that this concept simply does not exist!

For its purpose, my definition is one of four possible equivalent definitions. Therefore, it is not the only possible definition but any of the three alternative definitions would work equally well. This fact of equivalence of four alternatives is a strong indication of how very useful the definition is. The many theorems derived from the definition of other standard types of local endgames are another strong sign of how very useful the definition is.

A global (instead of local) study scope permits another (or other) definition(s) of (then global) double sente. Therefore, the definition of local double sente does not describe concepts of double sente completely. (Besides, there is the related doubly ambiguous type.)

Other local definitions might be suggested but will they have similar success of equivalence and applications in theorems? A global definition might be suggested but which is the best remains to be seen by its scope of application.

Since you question the usefulness of the concept of local double sente due its infamous non-existence, do not forget to notice, as already John pointed out, that O Meien forwent double sente entirely when evaluating local endgames! He must also have been aware that non-existence would be a strong possibility.

I will continue to use this "double sente" as many other go players do .i.e. in an informal context, trying simply to have a common understanding.

There won't be such a common understanding because most go players only familiar with some related informal context do not have a clear understanding. Many of them are kyus still repeating the same mistakes of the past: playing too early because something is called double sente or playing too late because the traditional fake move value suggests such.

because you claim that "local double sente" does not exist [...] such discussion cannot take place OC.

Nonsense. Of course, discussion is possible due to the context of all the other types that do exist and therefore give a good understanding of what a local double sente would be.

[Gérard TAILLE]

"Double sente" is a concept which exists in the go language for a very long time.

And as such often is a local gote, misleading everybody by the name "double sente" and by pretending bad values to be move values with the fake information on when to play in them. The centuries(?) of wrong teaching must be overcome. You are one of the few doing better by also studying good moments of local play.

to define this wording in a different context,

No. It is not a different context, but is the most frequent traditional context (appearing in old textbooks) with now added clarity. The less frequent traditional context of what later Bill Spight discussed and then I called global double sente (or double sente in the global positional context) was infrequently associated by amateur dans as "try to play there before the opponent but not too early" because of an awareness that the opponent would tenuki rather than accept a double sente fate.

to decide your defintion is the only acceptable one, and in addition to conclude that this concept simply does not exist!

For its purpose, my definition is one of four possible equivalent definitions. Therefore, it is not the only possible definition but any of the three alternative definitions would work equally well. This fact of equivalence of four alternatives is a strong indication of how very useful the definition is. The many theorems derived from the definition of other standard types of local endgames are another strong sign of how very useful the definition is.

A global (instead of local) study scope permits another (or other) definition(s) of (then global) double sente. Therefore, the definition of local double sente does not describe concepts of double sente completely. (Besides, there is the related doubly ambiguous type.)

Other local definitions might be suggested but will they have similar success of equivalence and applications in theorems? A global definition might be suggested but which is the best remains to be seen by its scope of application.

Since you question the usefulness of the concept of local double sente due its infamous non-existence, do not forget to notice, as already John pointed out, that O Meien forwent double sente entirely when evaluating local endgames! He must also have been aware that non-existence would be a strong possibility.

I will continue to use this "double sente" as many other go players do .i.e. in an informal context, trying simply to have a common understanding.

There won't be such a common understanding because most go players only familiar with some related informal context do not have a clear understanding. Many of them are kyus still repeating the same mistakes of the past: playing too early because something is called double sente or playing too late because the traditional fake move value suggests such.

because you claim that "local double sente" does not exist [...] such discussion cannot take place OC.

Nonsense. Of course, discussion is possible due to the context of all the other types that do exist and therefore give a good understanding of what a local double sente would be.

OK let's try to continue the discussion.
What about the following definition using thermography: a double sente position is a position for which a part of the mast is purple.
With this definition it does not remain a lot of positions does it?

[Gérard TAILLE]

BTW a sente position can be simply a position for which a part of the mast is colored, without being a double sente position.

[RobertJasiek]

What about the following definition using thermography: a double sente position is a position for which a part of the mast is purple.
With this definition it does not remain a lot of positions does it?

This is a good candidate for a definition in thermography. (However, why at all? Why not just call such local endgames "purple"?) I have not studied purple examples carefully yet but recall that they are infrequent or related to rare kos.

Since thermography is pretty well developed, such a definition has a good chance of being useful. I have, however, used thermography so infrequently that I cannot say ad hoc if typical candidate shapes, such as doubly ambiguous, qualify. (In such a theory, there might be no necessity for the extra type doubly ambiguous but it might be put in the double sente category.)

[Gérard TAILLE]

What about the following definition using thermography: a double sente position is a position for which a part of the mast is purple.
With this definition it does not remain a lot of positions does it?

This is a good candidate for a definition in thermography. (However, why at all? Why not just call such local endgames "purple"?) I have not studied purple examples carefully yet but recall that they are infrequent or related to rare kos.

Since thermography is pretty well developed, such a definition has a good chance of being useful. I have, however, used thermography so infrequently that I cannot say ad hoc if typical candidate shapes, such as doubly ambiguous, qualify. (In such a theory, there might be no necessity for the extra type doubly ambiguous but it might be put in the double sente category.)

I studied thermography in the past but I do not either use it. Anyway if it is a good mean to exchange avoiding ambiguity why not.
May be I can see a better wording. Considering purple color is both a blue and a red color:

A position is a black sente position if a part of the mast is blue.
A position is a white sente position if a part of the mast is red.
A position is a gote position if it is neither black sente nor white sente.
A position is double sente if it is both black sente and white sente.

I did not take into account ambiguous position. If it is a real need OC I can try to complete the definitions.

[RobertJasiek]

Thermography, which uses thermographs algebraically or graphically, is powerful and I do not want to discourage you from enhancing it. However, it is inapplicable by players in practice. For application to a typical example, I need hours. General principals for fast application to whole classes of positions are too rough or otherwise missing. This is very different from theory for the temperature and a few move values or counts, for which application time is fast or reasonable.

[Gérard TAILLE]

Thermography, which uses thermographs algebraically or graphically, is powerful and I do not want to discourage you from enhancing it. However, it is inapplicable by players in practice. For application to a typical example, I need hours. General principals for fast application to whole classes of positions are too rough or otherwise missing. This is very different from theory for the temperature and a few move values or counts, for which application time is fast or reasonable.

As I said clearly in my previous post I do not use thermography in practice. I completly agree with you it is inapplicable in practice. I use it here only to show you clearly what means "sente", "gote, or "double sente" for me.
Because the defintion I proposed are simply based on the definition of "sente" the challenge is only to find a simple defintion of "sente" immediatly understandable by any go player not necessarily aware of the huge amount of work made in the theory field.
Do you have yourself such simple defintion of "sente" position (if it is not a secret in your books OC)?

[RobertJasiek]

There has also been my naive definition (uh, even in writing): one player has a sente sequence and the opponent has a gote sequence. Might be good enough for some players but when Bill pointed out its informality, I dug deeper.

[Gérard TAILLE]

There has also been my naive definition (uh, even in writing): one player has a sente sequence and the opponent has a gote sequence. Might be good enough for some players but when Bill pointed out its informality, I dug deeper.

I agree with you Robert this naive defintion is not satisfactory : in this defintion of a "sente position" you use the wording "sente sequence" but what is a "sente sequence"? Do you need an environment to define a "sente sequence"? If yes don't you have in addition to analyse at which temperature of the environment a sequence can be sente?

[RobertJasiek]

It is, however, the most complicated that might be immediately understandable by any go player:)

[Gérard TAILLE]

It is, however, the most complicated that might be immediately understandable by any go player:)

I think if you try to define a "sente position" without taking into account an environment, then this defintion as a good chance to be complicated and more or less unanderstandable for go players. That is a basic reason why I created my approach based on a rich enviroment. With such environment everything becomes far easier indeed.

[RobertJasiek]

everything becomes far easier indeed.

With algebra for every go player?! You need to hide solving systems of equations when selling it as easy for every go player!