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 Post subject: Shikatsu Myoki Tsumego Series
Post #1 Posted: Mon Jul 19, 2021 8:25 am 
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https://senseis.xmp.net/?ShikatsuMyokiTsumegoSeries76

Click Here To Show Diagram Code
[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?

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 Post subject: Re: Shikatsu Myoki Tsumego Series
Post #2 Posted: Mon Jul 19, 2021 2:23 pm 
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Gérard TAILLE wrote:
https://senseis.xmp.net/?ShikatsuMyokiTsumegoSeries76

Click Here To Show Diagram Code
[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.

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 Post subject: Re: Shikatsu Myoki Tsumego Series
Post #3 Posted: Mon Jul 19, 2021 4:21 pm 
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The solution given on senseis seems fine, does it not?

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 Post subject: Re: Shikatsu Myoki Tsumego Series
Post #4 Posted: Tue Jul 20, 2021 2:49 am 
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Kirby wrote:
The solution given on senseis seems fine, does it not?


The problem with the solution is that black has not fighted the ko. Assume :b8: used a ko threat, :w9: answer the ko threat and :b10: retake the ko. That way black has gained locally one move which is quite different.

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 Post subject: Re: Shikatsu Myoki Tsumego Series
Post #5 Posted: Tue Jul 20, 2021 3:09 am 
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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.

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 Post subject: Re: Shikatsu Myoki Tsumego Series
Post #6 Posted: Tue Jul 20, 2021 3:29 am 
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Cassandra wrote:
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.

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.

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 Post subject: Re: Shikatsu Myoki Tsumego Series
Post #7 Posted: Tue Jul 20, 2021 3:39 am 
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Gérard TAILLE wrote:
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.

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 Post subject: Re: Shikatsu Myoki Tsumego Series
Post #8 Posted: Tue Jul 20, 2021 7:01 am 
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Gérard TAILLE wrote:
https://senseis.xmp.net/?ShikatsuMyokiTsumegoSeries76

Click Here To Show Diagram Code
[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?


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

Click Here To Show Diagram Code
[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]
:b8: ko theat
:w9: answer to ko threat

Click Here To Show Diagram Code
[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]

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 Post subject: Re: Shikatsu Myoki Tsumego Series
Post #9 Posted: Tue Jul 20, 2021 8:30 am 
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Gérard TAILLE wrote:
You do not get my point Cassandra. With black I only want to fight the ko at "a", not the others:

Dear Gérard,

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

Click Here To Show Diagram Code
[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]
:b8: 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.

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 Post subject: Re: Shikatsu Myoki Tsumego Series
Post #10 Posted: Tue Jul 20, 2021 8:54 am 
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Cassandra wrote:
Gérard TAILLE wrote:
You do not get my point Cassandra. With black I only want to fight the ko at "a", not the others:

Dear Gérard,

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

Click Here To Show Diagram Code
[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]
:b8: 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.


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

Click Here To Show Diagram Code
[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:

Click Here To Show Diagram Code
[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.

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 Post subject: Re: Shikatsu Myoki Tsumego Series
Post #11 Posted: Tue Jul 20, 2021 10:10 am 
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"UNconditional" does not imply that there is no ko involved!

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

Shikatsu Myoki #76:

Click Here To Show Diagram Code
[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]

:b4: creates a SECOND ko shape.
:w7: captures the ko at right.

Click Here To Show Diagram Code
[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]

:b8: connects, as he does not have any LOCAL ko threat.
:b10: recaptures the ko at right.
:w11: captures the ko at left.

Click Here To Show Diagram Code
[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.

Click Here To Show Diagram Code
[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]


Click Here To Show Diagram Code
[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]


Click Here To Show Diagram Code
[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:

Click Here To Show Diagram Code
[go]$$B Black to play
$$ -----------------
$$ | . . . . X . .
$$ | . . O O X . .
$$ | . . O X . . .
$$ | . . . X . . .
$$ | . O X . X . .
$$ | . O . . . . .
$$ | . X X X . . .
$$ | . . . . . . .
$$ | . . . . . . .
$$[/go]


Click Here To Show Diagram Code
[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]

:w8: creates a ko shape.
:b9: captures the ko.

Click Here To Show Diagram Code
[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]

:w10: plays a LOCAL ko threat.
:b11: answers.
:w12: recaptures the ko.

Click Here To Show Diagram Code
[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.)

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 Post subject: Re: Shikatsu Myoki Tsumego Series
Post #12 Posted: Tue Jul 20, 2021 10:24 am 
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Cassandra wrote:
"UNconditional" does not imply that there is no ko involved!

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

Shikatsu Myoki #76:

Click Here To Show Diagram Code
[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]

:w3: creates a SECOND ko shape.
:w7: captures the ko at right.


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?

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 Post subject: Re: Shikatsu Myoki Tsumego Series
Post #13 Posted: Tue Jul 20, 2021 11:04 am 
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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"?

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 Post subject: Re: Shikatsu Myoki Tsumego Series
Post #14 Posted: Tue Jul 20, 2021 11:14 am 
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jlt wrote:
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.

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 Post subject: Re: Shikatsu Myoki Tsumego Series
Post #15 Posted: Tue Jul 20, 2021 11:37 am 
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Gérard TAILLE wrote:
Black does not have any LOCAL ko threat => White lives in ko. => White is NOT unconditionally living.
Don't you agree with that?

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.

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 Post subject: Re: Shikatsu Myoki Tsumego Series
Post #16 Posted: Tue Jul 20, 2021 12:23 pm 
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I am as puzzled as Gérard is about all of this.

So Gérard posted this diagram:

Click Here To Show Diagram Code
[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?

Click Here To Show Diagram Code
[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.

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Post #17 Posted: Tue Jul 20, 2021 12:51 pm 
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Farodin wrote:
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?

Click Here To Show Diagram Code
[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]



That position is possible because :b8: played a ko threat elsewhere, and :w9: responded. Whether you accept :b8: - :w9: is a matter of convention.

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Post #18 Posted: Tue Jul 20, 2021 1:47 pm 
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White is alive in double ko. I really don't understand the objection to this.

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Post #19 Posted: Tue Jul 20, 2021 1:55 pm 
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Kirby wrote:
White is alive in double ko. I really don't understand the objection to this.

Click Here To Show Diagram Code
[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.

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Post #20 Posted: Tue Jul 20, 2021 3:48 pm 
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I get your point - black insists on the ko at 'a'.

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

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