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[go]$$Wc Life and death situation 4
$$ | . . . . . . . . .
$$ | X X X X X X . . .
$$ | . . . a . . X . .
$$ | O O O b O . X . .
$$ | . X 1 . O . X . .
$$ ------------------[/go]

I meant: if White plays at C1, then if Black plays at "a" then White plays at "b" and lives, and if Black plays at "b" then White plays at "a" and lives.

@Bill:



Uhm, not to drive you mad, but why is the word "captured" used here?

So, when they are dead, they all can be captured.
When they are captured, they will be taken off the board.
Nobody plays until then because it is futile.

But - when exactly was it that they were "killed"??
Are they "killed" by putting them in a situation so they are dead?
(Makes sense - kill someone and he's dead.)
But after being dead, they can/could be captured (right?).
Who captures (takes as prisoners) dead soldiers??
(What does "capture" mean, literally and/or in Go, remove them from the board, or have them as prisoners who can't escape??)

Maybe it's an Aspergian language problem or I'm just not into warfare...

@jlt:
Fascinating how after seeing this it seems so obvious...

Captured is one of the basic concepts of go. Dead is not. It is a derived concept.

During play, stones are captured by filling all of their dame. At the end of play, there are stones that may be captured, but do not have to be to remove them from the board. These stone are dead. What makes them dead? The fact that they cannot be defended from capture. (As my post indicated, that is not the only requirement, but it is necessary. )



Dead stones are actually taken off the board with capturing them. But only after play has stopped.



Good question. During the game stones may informally be considered alive or dead. But sometimes that turns out not to be so at the end of the game. So during the game we may "kill" some stones, leaving them on the board with the expectation of taking them off the board without capturing them at the end of play. But that is speaking informally. Strictly speaking, stones are not dead or alive until play has stopped.



Yes. But they may come back to life before play ends.



That is a necessary condition of being dead.



Nobody. They are removed from the board without capturing them.



You capture stones by taking away all of their dame and removing them from the board.



Asparagus is good for you.

_________________
The Adkins Principle:
At some point, doesn't thinking have to go on?
— Winona Adkins

Visualize whirled peas.

Everything with love. Stay safe.

Actually English terms do seem a bit wrong here. Contrary to everyday meaning "captured" or "prisoner" is more dead than "dead" stones that were "killed" (but might still revive later, or need effort to keep them dead).

There is an analogy in which the English terms make sense. You may have to go to some effort to capture living soldiers, but dead soldiers you can just drag off the field of battle without having to capture them.

_________________
The Adkins Principle:
At some point, doesn't thinking have to go on?
— Winona Adkins

Visualize whirled peas.

Everything with love. Stay safe.

Okay, dragging dead soldiers off the battlefield.

My semantic problems revolve around Knotwilg's post,
https://lifein19x19.com/viewtopic.php?p=245208#p245208
(#14, don't know how to use this marker)

The subtle difference between "kill" and "capture".

So moves can be aimed to kill a group (keeping them from making two real eyes) as to capture them later?
And capturing part of a group can help kill the whole group by removing possibilities to form eyes?

Uhm, @Knotwilg, why was it exactly I need to learn this difference?

Here, White is dead but not captured. This means that, even if White plays first, Black can capture White if he wants to.

Click Here To Show Diagram Code

[go]$$Bc White is dead
$$ | . . . . . . . . .
$$ | X X X X X . . . .
$$ | O O O O X . . . .
$$ | . 1 . O X . . . .
$$ ------------------[/go]

However, if Black doesn't pay attention to the surrounding group and lets White play several moves in the area

Click Here To Show Diagram Code

[go]$$Bc Now White is alive and black is dead
$$ | . . . . . . . . .
$$ | O O O O O . . . .
$$ | X X X X X O . . .
$$ | O O O O X O . . .
$$ | . X . O X . . . .
$$ ------------------[/go]

then White becomes alive and Black is dead.

So, the "1" move has "killed" white, but until white has been captured, things might change and white might come back to life?
A bit zombie-ish. Better capture them, killing will not suffice, they might still get a chance to eat your brain!

Speaking of brains... mine feels half-eaten now.
Thank you all!

I think part of the problem with understanding dead vs. captured is that you have not played a game. During the play the only way that stones are removed from the board is by being captured. Capturing stones is part of the play. Dead stones are not captured. Removing dead stones is part of the scoring process. Strictly speaking, it is not necessary to remove dead stones to score the game, but it is the usual way to do it.

Click Here To Show Diagram Code

[go]$$Bc Game over
$$ ----------------
$$ | X X . . . . . |
$$ | O O O O O O O |
$$ | X X X X X X O |
$$ | O O O O X . X |
$$ | . X . O X X . |
$$ ----------------[/go]

For instance, here is the end of a very unlikely 5x7 game. There are no captured stones. Black has killed the White group on the bottom, and there are two dead stones on the top. We could say that White has killed them, but we usually only talk about killing groups. (Go terminology, like most language, is usually informal, not precise. )

We could count the score easily on the small board. Black has 2 pts. for each dead stone in his territory plus 1 pt. for each empty point. That gives him 14 pts. White has 2 pts. for each dead stone plus 1 pt. for each empty point. That gives him 9 pts. Black wins by 5 pts.

But most boards are not so easy to count. In that case we remove the dead stones from Black's territory and put them inside White's territory, and vice versa. We also put the Black stones that White has captured inside Black's territory, and vice versa. Doing so with this board, we have:

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[go]$$Bc Game scored
$$ ----------------
$$ | O O O O O . . |
$$ | O O O O O O O |
$$ | X X X X X X O |
$$ | . . . X X X X |
$$ | . . . . X X X |
$$ ----------------[/go]

Now we simply count the empty points. Black has 7, White has 2, so Black wins by 5, as advertised.

Here is the end of a professional game.

Click Here To Show Diagram Code

[go]$$B
$$ ---------------------------------------
$$ | . . . O O X . . . . . X X O . . . . . |
$$ | . . O O X X . . . . X X O O O O . . . |
$$ | . . O X X O X . . X X O O O X O X . . |
$$ | . . O X . . . . X , X X X X X O . . . |
$$ | . O X X X X X O . O O . X O O . . . . |
$$ | . . O X O O X O . . . . X X O O O . . |
$$ | . . O O . O O X X . O . X O O X O O . |
$$ | . . . O . O O O X X O X O O X X X O O |
$$ | . . . . O O O O X O X . X X O . X X O |
$$ | . . . X X X O X X O X . . . . , X . X |
$$ | . X . X O X O X O O O X . . . X X X . |
$$ | . . O O O O X X a O X X X X X O X . . |
$$ | . O . . O X X X O O O O X O O O X . . |
$$ | . . O O O X . . X X O . O O . O X . . |
$$ | O O X X X X . . X O d . . O O X X X b |
$$ | O X . X O X . . X O X . . . . O X O X |
$$ | O X X O . . O . X O O . O . . O X O c |
$$ | X X O . O . . . X X O O X O O . O . O |
$$ | . . . . . . . . X X X X X O . . . O . |
$$ ---------------------------------------[/go]

Only the points, a, b, c, and d, remain to be filled before scoring. (Edit: This game was played in 1950. Today pros normally fill such points during play. Edit2: Oops! White needs to protect at d, doesn't he? That's one reason to fill all those points. ) White has captured 7 Black stones, Black has captured 3 White stones. There are several dead stones on the board, which you should be able to identify. Black killed a White group in the bottom left.

_________________
The Adkins Principle:
At some point, doesn't thinking have to go on?
— Winona Adkins

Visualize whirled peas.

Everything with love. Stay safe.

Click Here To Show Diagram Code

[go]$$B Black captures the white stones
$$ | . . . . . . .
$$ | X X X X X . .
$$ | O O O O X . .
$$ | O 1 O O X . .
$$ ---------------[/go]

In this diagram, removes the last liberty of these 7 white stones. By the rule of capture, the white stones are removed from the board.
This is what we mean by Black captures the white stones.

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[go]$$B Black kills White
$$ | . . . . . . .
$$ | X X X X X . .
$$ | O O O O X . .
$$ | . 1 . O X . .
$$ ---------------[/go]

Black kills the white stones, because their eyespace is reduced to 1 eye.
Black does not capture the white stones, because they still have two liberties. In fact ...

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[go]$$B From kill to capture - 1
$$ | . . . . . . .
$$ | X X X X X . .
$$ | O O O O X . .
$$ | 2 X 1 O X . .
$$ ---------------[/go]

If next Black decides to capture the white stones, reducing their liberties to 1, the maneuver needs to go in 3 steps.
After White can capture the two stones at .

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[go]$$B From kill to capture - 2
$$ | . . . . . . .
$$ | X X X X X . .
$$ | O O O O X . .
$$ | O 3 4 O X . .
$$ ---------------[/go]

In the resulting position, again goes for capture, but again White can postpone being captured, by capturing herself at

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[go]$$B From kill to capture - 3
$$ | . . . . . . .
$$ | X X X X X . .
$$ | O O O O X . .
$$ | O 5 O O X . .
$$ ---------------[/go]

Finally White has only one liberty left and Black captures all 7 stones, as in the very first diagram.

The whole sequence of mutual captures goes to show that Black has originally killed White, in the second diagram.

Now what did I mean with worry free?

Click Here To Show Diagram Code

[go]$$B Black kills White
$$ | . . . . . . .
$$ | . O O O O O .
$$ | X X X X X O .
$$ | O O O O X . .
$$ | . 1 . O X . .
$$ ---------------[/go]

Just like in diagram 2, Black killes White by reducing the eyespace to 1 eye. However, Black is not worry free: the black chain has 3 liberties, against White's 2 inside. Black is ahead in the capturing race but needs to be mindful of his small advantage.

Click Here To Show Diagram Code

[go]$$B Counting liberties
$$ | . . . . . . .
$$ | . O O O O O .
$$ | X X X X X O .
$$ | O O O O X 2 .
$$ | . 1 3 O X . .
$$ ---------------[/go]

When White reduces Black to 2 liberties, it's not sufficient for Black to have killed the white stones in the corner. He must set out to effectively capture them, starting with as in the above sequence of captures.

If there's anything unclear about the above, ask freely.

The Go terminology is a bit counter-intuitive: I would naturally think killed/dead is a more fatal/worse outcome than captured, but in go killed stones are still on the board and not captured yet (so can still have aji). But captured stones are totally gone.

I guess that, for go players, capture is worse than death ! never surrender !