https://senseis.xmp.net/?ShikatsuMyokiTsumegoSeries76

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[go]$$W White to play and live
$$ --------------------------
$$ . . . . . . . . . . . . |
$$ . . . . X . X . . . O O |
$$ . . . . . X O O O O X O |
$$ . . . . . . X X X X a X |
$$ . . . . . . . . . . X . |
$$ . . . . . . . . . . . . |
$$ . . . . . . . . . . . . |
$$[/go]

I understand White can live without any condition but I do not find how white can live if Black can avoid losing the ko fight at "a".
Can anybody help me?

After further analysis I think white can save one of her two groups but not both, but OC I am not completly sure.

The solution given on senseis seems fine, does it not?

_________________
be immersed

The problem with the solution is that black has not fighted the ko. Assume used a ko threat, answer the ko threat and retake the ko. That way black has gained locally one move which is quite different.

One major assumption for local tsume-go is that the rest of the board is empty / that there are no worthwile moves outside the local area shown.

_________________
The really most difficult Go problem ever: https://igohatsuyoron120.de/index.htm
Igo Hatsuyōron #120 (really solved by KataGo)

Looking at the first page of Shikatsu Myoki Tsumego Series https://senseis.xmp.net/?ShikatsuMyokiTsumegoSeries I see killing, living and Ko problems.
Here it is a living problem and I underderstood living here means living without conditions but may be I am wrong.

"Double-ko" is considered "unconditionally alive".

If a ko fight were involved, it would have to be a local one.

In the problem in question, White has a local ko threat, but Black does not have any. Therefore, the ko shape will not be still active at the end of the solution sequence.

_________________
The really most difficult Go problem ever: https://igohatsuyoron120.de/index.htm
Igo Hatsuyōron #120 (really solved by KataGo)

You do not get my point Cassandra. With black I only want to fight the ko at "a", not the others:

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[go]$$W White to play and live
$$ --------------------------
$$ . . . . . 4 3 5 2 . . . |
$$ . . . . X . X 1 . 6 O O |
$$ . . . . . X O O O O X O |
$$ . . . . . . X X X X 7 X |
$$ . . . . . . . . . . X . |
$$ . . . . . . . . . . . . |
$$ . . . . . . . . . . . . |
$$[/go]

ko theat
answer to ko threat

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[go]$$Bm10
$$ --------------------------
$$ . . . . . X O O X . . . |
$$ . . . 3 X 2 X O . X O O |
$$ . . . . . X O O O O 1 O |
$$ . . . . . . X X X X O X |
$$ . . . . . . . . . . X . |
$$ . . . . . . . . . . . . |
$$ . . . . . . . . . . . . |
$$[/go]

Dear Gérard,

I am very well aware of what you wanted to do. But if you are talking about Shikatsu Myoki #76, ...

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[go]$$W White to play and live
$$ --------------------------
$$ . . . . . 4 3 5 2 . . . |
$$ . . . . X . X 1 . 6 O O |
$$ . . . . . X O O O O X O |
$$ . . . . . . X X X X 7 X |
$$ . . . . . . . . . . X 9 |
$$ . . . . . . . . . . . . |
$$ . . . . . . . . . . . . |
$$[/go]

pass

... your desire will end locally as in the diagramme above.

However, if you wanted to study an extended VARIATION of that position (NOT the original TSUME-GO), you should add some kind of precondition that creates a firm connection to other positions on the Go board, and also specifies which value potential external ko threats of both sides have.

_________________
The really most difficult Go problem ever: https://igohatsuyoron120.de/index.htm
Igo Hatsuyōron #120 (really solved by KataGo)

Cassandra, I confess I have difficulty to understand what is your view, sorry for that.
Here is the original position

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[go]$$W White to play and live
$$ --------------------------
$$ . . . . . . . . . . . . |
$$ . . . . X . X . . . O O |
$$ . . . . . X O O O O X O |
$$ . . . . . . X X X X a X |
$$ . . . . . . . . . . X . |
$$ . . . . . . . . . . . . |
$$ . . . . . . . . . . . . |
$$[/go]

Here is the beginning of the given solution:

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

After the sequence above, do you claim white can live without conditions?
If not that means that you agree with me because I just do not say something else.

"UNconditional" does not imply that there is no ko involved!

+ + + + + + + + + + + + +
+ + + + + + + + + + + + +

Shikatsu Myoki #76:

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[go]$$W
$$ --------------------------
$$ . . . . . 4 3 5 2 . . . |
$$ . . . . X . X 1 . 6 O O |
$$ . . . . . X O O O O X O |
$$ . . . . . . X X X X 7 X |
$$ . . . . . . . . . . X . |
$$ . . . . . . . . . . . . |
$$ . . . . . . . . . . . . |
$$[/go]

creates a SECOND ko shape.
captures the ko at right.

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[go]$$Bm8
$$ --------------------------
$$ . . . . . X O O X . 2 . |
$$ . . . . X 4 X O . X O O |
$$ . . . . . X O O O O 3 O |
$$ . . . . . . X X X X O X |
$$ . . . . . . . . . . X 1 |
$$ . . . . . . . . . . . . |
$$ . . . . . . . . . . . . |
$$[/go]

connects, as he does not have any LOCAL ko threat.
recaptures the ko at right.
captures the ko at left.

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

Double-ko = unconditional life for White.

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[go]$$Bm12
$$ --------------------------
$$ . . . . . X O O X . O . |
$$ . . . 1 X O . O . X O O |
$$ . . . . . X O O O O X O |
$$ . . . . . . X X X X 2 X |
$$ . . . . . . . . . . X X |
$$ . . . . . . . . . . . . |
$$ . . . . . . . . . . . . |
$$[/go]

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[go]$$Bm14
$$ --------------------------
$$ . . . . . X O O X . O . |
$$ . . . X X O 1 O . X O O |
$$ . . . . . X O O O O 2 O |
$$ . . . . . . X X X X O X |
$$ . . . . . . . . . . X X |
$$ . . . . . . . . . . . . |
$$ . . . . . . . . . . . . |
$$[/go]

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

Q.e.d.

+ + + + + + + + + + + + +
+ + + + + + + + + + + + +

Igo Hatsuyoron #80:

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[go]$$B Black to play
$$ -----------------
$$ | . . . . X . .
$$ | . . O O X . .
$$ | . . O X . . .
$$ | . . . X . . .
$$ | . O X . X . .
$$ | . O . . . . .
$$ | . X X X . . .
$$ | . . . . . . .
$$ | . . . . . . .
$$[/go]

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[go]$$B
$$ -----------------
$$ | 9 8 4 1 X . .
$$ | 6 3 O O X . .
$$ | 7 . O X . . .
$$ | . 2 . X . . .
$$ | . O X . X . .
$$ | 5 O . . . . .
$$ | . X X X . . .
$$ | . . . . . . .
$$ | . . . . . . .
$$[/go]

creates a ko shape.
captures the ko.

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[go]$$Wm10
$$ -----------------
$$ | X O O X X . .
$$ | 3 X O O X . .
$$ | X . O X 1 2 .
$$ | . O . X . . .
$$ | . O X . X . .
$$ | X O . . . . .
$$ | . X X X . . .
$$ | . . . . . . .
$$ | . . . . . . .
$$[/go]

plays a LOCAL ko threat.
answers.
recaptures the ko.

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[go]$$W
$$ -----------------
$$ | ? O O X X . .
$$ | O X O O X . .
$$ | X ? O X O X .
$$ | . O . X . . .
$$ | . O X . X . .
$$ | X O . . . . .
$$ | . X X X . . .
$$ | . . . . . . .
$$ | . . . . . . .
$$[/go]

Black does not have any LOCAL ko threat => White dies in ko. => White is NOT unconditionally dead.
(The ko is disadvantageous for Black, as he has to find the first EXTERNAL ko threat, and White has several LOCAL ko threats remaining.)

_________________
The really most difficult Go problem ever: https://igohatsuyoron120.de/index.htm
Igo Hatsuyōron #120 (really solved by KataGo)

I agree till that point. But here, with black to play, I stop playing locally and say:
Black does not have any LOCAL ko threat => White lives in ko. => White is NOT unconditionally living.
Don't you agree with that?

To summarize, if I followed correctly your conversation,

1) If there are no ko threats elsewhere, White lives by double ko.
2) If Black has enough ko threats elsewhere, then Black can kill White.

Cassandra calls the conjunction of 1) and 2) "living without condition", while Gérard calls that "living by ko"?

Yes jlt but, in addition, if Black has enough ko threats elsewhere then the sequence given is not the best one for white. By choosing other moves I think white can save one of her groups.

NO. Not if we talk about TSUME-GO.

Your misunderstanding here is similar to the following:
The correct solution of a tsume-go is assumed to contain the strongest attempt of the attacker / the strongest defense of the defender.
For many of these positions -- if encountered in a real game -- you would stop the tsume-go solution sequence in between, in order to play moves in the surrounding that will benefit you in the endgame (e.g. instead of trying the strongest attempt to kill from the inside but fail, and / or to sacrifice stones unnecessarily).

Even with Shikatsu Myoki #76, you might want to play Black 2 at 5, in order to reduce White's corner territory decisively in sente, and be happy with it.

Life-and-death tsume-go are designed for training your attacking and defending techniques in close combat. They are not intended to simulate the decision criteria of a "real" game. With regard to "real" games, many tsume-go solutions must be considered wrong.

_________________
The really most difficult Go problem ever: https://igohatsuyoron120.de/index.htm
Igo Hatsuyōron #120 (really solved by KataGo)

I am as puzzled as Gérard is about all of this.

So Gérard posted this diagram:

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[go]$$Bm10
$$ --------------------------
$$ . . . . . X O O X . . . |
$$ . . . 3 X 2 X O . X O O |
$$ . . . . . X O O O O 1 O |
$$ . . . . . . X X X X O X |
$$ . . . . . . . . . . X . |
$$ . . . . . . . . . . . . |
$$ . . . . . . . . . . . . |
$$[/go]

I've copied the resulting shape below. It is clear to me that white needs to win the ko at 'a' in order to live. There is no double ko here. Whether black has local threats or not shouldn't matter, should it?

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[go]$$ White to move
$$ --------------------------
$$ . . . . . X O O X . . . |
$$ . . . X X O . O . X O O |
$$ . . . . . X O O O O X O |
$$ . . . . . . X X X X a X |
$$ . . . . . . . . . . X . |
$$ . . . . . . . . . . . . |
$$ . . . . . . . . . . . . |
$$[/go]

The only difference I see between this tsumego and other tsumego that are commonly accepted to end in "life / death by ko" is that the ko at 'a' is already present at the beginning of the tsumego.

That position is possible because played a ko threat elsewhere, and responded. Whether you accept - is a matter of convention.

White is alive in double ko. I really don't understand the objection to this.

_________________
be immersed

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[go]$$ White to move
$$ --------------------------
$$ . . . . c X O O X . b . |
$$ . . . X X O . O . X O O |
$$ . . . . . X O O O O X O |
$$ . . . . . . X X X X a X |
$$ . . . . . . . . . . X . |
$$ . . . . . . . . . . . . |
$$ . . . . . . . . . . . . |
$$[/go]

Consider at the beginning that black is only interested by winning the ko at "a". It is white to play but for black b and c are miai, that is the point.

I get your point - black insists on the ko at 'a'.

Then, I agree with you. I think it's ko.

_________________
be immersed