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Do recaptures of non-ko capturing plays occur in practice? http://www.lifein19x19.com/viewtopic.php?f=10&t=15039	Page 1 of 1

Author:	luigi [ Tue Oct 17, 2017 3:53 pm ]
Post subject:	Do recaptures of non-ko capturing plays occur in practice?
I have a very specific question for you seasoned players: is there any position where it's good to make a capture that is not part of a ko or a long cycle and where the stone you place to make said capture can itself be reasonably expected to be captured by the opponent at some later time? Snapback, for instance, is not a valid example because the first capture is made useless by the recapture.

Author: Calvin Clark [ Tue Oct 17, 2017 4:42 pm ]

Post subject: Re: Do recaptures of non-ko capturing plays occur in practic

luigi wrote:

I have a very specific question for you seasoned players: is there any position where it's good to make a capture that is not part of a ko or a long cycle and where the stone you place to make said capture can itself be reasonably expected to be captured by the opponent at some later time?

Snapback, for instance, is not a valid example because the first capture is made useless by the recapture.

If the first capture captures multiple stones it is very common. Consider this example:

Click Here To Show Diagram Code: [go]$$B Capture three stones $$ ------------- $$ . X O O O 1 O . $$ . X X X X O O . $$ . . . . . . . .[/go]

After this capture, the position looks like this. Whether or not white or black gets to play first at 'a' depends on the rest of the board. We cannot say without further information whether or not :b1:

above was good in first place. Sometimes it is, and sometimes it's not.

Click Here To Show Diagram Code: [go]$$B Capture three stones $$ ------------- $$ . X . . a X O . $$ . X X X X O O . $$ . . . . . . . .[/go]

Even if you are talking about the capture of one stone, sometimes the capturing that stone temporarily stabilizes an unstable group. Later on, maybe the stone that makes the capture is put in atari, but it is no longer necessary connect because the group is safe for other reasons (e.g., even if disconnected it still has two eyes, etc.)

So I don't believe a general statement can be made that a capture is not good if the stone that captures could itself be captured later.

Take a look at this AlphaGo self-play game.

Click Here To Show Diagram Code: [go]$$ Position at move 266 - Black to play $$ --------------------------------------- $$ | . . . . . . . X . . . X X O . . . . . | $$ | . . X . . . X O X . . X O . . . O . . | $$ | . . X O . . X O O X X X O O . X O . . | $$ | . X X O . . X O . X X O . . . X O . . | $$ | . O X O . . X O O O X O . . . X O X . | $$ | . B O O . X X X O X X O . . O X X O O | $$ | B B B O X X X O O X . O X X O X X X O | $$ | O B B O X . O O X X X O X O O O X O . | $$ | . O O X O O . X X O O X X O . O O O . | $$ | . O X X X O X X O , . . X O X X X O . | $$ | O O O X O . O O . O O O O O X X O O O | $$ | . O O X O O . O O X X X O . . X O X O | $$ | . O O X X X O . X X O . O O X X X X X | $$ | O . O O X . O X . . . O . . O . X . . | $$ | O O X X X O O O O O X O O O O O X X . | $$ | O X . X O O X X X O O X O X O X O O . | $$ | X X X . X X O O X X X X X X X X . O . | $$ | . . . X . X . . . . O X O X . . X O X | $$ | . . . . . . . . . . . O . . . . . O . | $$ ---------------------------------------][/go]

Click Here To Show Diagram Code: [go]$$B Moves 267 to 272 $$ --------------------------------------- $$ | . . . . . . . X . . . X X O . . . . . | $$ | . . X . . . X O X . . X O . . . O . . | $$ | . . X O . . X O O X X X O O . X O . . | $$ | 3 X X O . . X O . X X O . . . X O . . | $$ | 2 O X O . . X O O O X O . . . X O X . | $$ | 5 X O O . X X X O X X O . . O X X O O | $$ | X X X O X X X O O X . O X X O X X X O | $$ | 6 X X O X . O O X X X O X O O O X O . | $$ | 1 O O X O O . X X O O X X O . O O O . | $$ | 4 O X X X O X X O , . . X O X X X O . | $$ | O O O X O . O O . O O O O O X X O O O | $$ | . O O X O O . O O X X X O . . X O X O | $$ | . O O X X X O . X X O . O O X X X X X | $$ | O . O O X . O X . . . O . . O . X . . | $$ | O O X X X O O O O O X O O O O O X X . | $$ | O X . X O O X X X O O X O X O X O O . | $$ | X X X . X X O O X X X X X X X X . O . | $$ | . . . X . X . . . . O X O X . . X O X | $$ | . . . . . . . . . . . O . . . . . O . | $$ ---------------------------------------[/go]

We can't argue that :b1:

is a bad move because those six stones are in atari before :b1:

and that's kind of big at this stage of the game.

Yet,

is later captured by :w6:

.

Can you explain your question with examples?

Author:	EdLee [ Wed Oct 18, 2017 1:06 am ]
Post subject:
Hi luigi, Re: Calvin's question; yes, what situation prompted your question ?

Author:	luigi [ Wed Oct 18, 2017 2:03 am ]
Post subject:	Re:
Calvin's answer settles it for me. It was an easier one than I thought. I was just wondering how my Kingo variant would change if captures had to be made with kings (while retaining the ko rule, even though it's not strictly needed).

Author:	jeromie [ Wed Oct 18, 2017 5:36 am ]
Post subject:	Re: Do recaptures of non-ko capturing plays occur in practic
Throwing in a stone to destroy a false eye is also very common. There would be many more shapes that are alive if that was not permitted! Edit: Bad example. That’s what I get for posting before coffee.

Author:	luigi [ Wed Oct 18, 2017 5:51 am ]
Post subject:	Re: Do recaptures of non-ko capturing plays occur in practic
jeromie wrote: Throwing in a stone to destroy a false eye is also very common. There would be many more shapes that are alive if that was not permitted! But a throw-in is not a capture, right? EDIT: Okay, I saw your edit.

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