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Silly Reading Mistake From Yesterday's Game
http://www.lifein19x19.com/viewtopic.php?f=10&t=12368		 Page 1 of 1
Author:  Kirby [ Mon Oct 19, 2015 12:23 pm ]
Post subject:  Silly Reading Mistake From Yesterday's Game
I made a silly reading mistake yesterday during one of my games. My opponent didn't catch it, but it's not that hard to see when you look for it (black to play):

Click Here To Show Diagram Code
[go]$$
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X , . . . . . O . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . O . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . X X X . |
$$ | . . . , . . . . . , . . . . . O X O . |
$$ | . . . . . . . . . . . . . . X X O X O |
$$ | . . . . . . . . . . . . . . X O O X . |
$$ | . . . . . . . . . . X . . . X O O . O |
$$ | . . . . . . . . . . . . X . X O . O O |
$$ | . . . . . . . . . . X O O O X O O X O |
$$ | . . . O . . . . . , X X O . O X X X O |
$$ | . . . . . O . . . . X O X O O . X . X |
$$ | . . . . . . . . . . . . X X O O X O X |
$$ | . . . . . . . . . . . . . X . O X O . |
$$ ---------------------------------------[/go]


It's a little embarrassing that I missed this during the game. My hope is that, by showing my mistake publicly, I'll be more careful in the future to avoid this type of reading mistake.

It's also kind of a cool shape, so I thought I'd share it with you L19ers.
Author:  Uberdude [ Mon Oct 19, 2015 12:42 pm ]
Post subject:  Re: Silly Reading MIstake From Yesterday's Game
Are you saying black has a good move now to save the corner, but you made a mistake and didn't play it? Because I can't see one. Or the mistake was earlier to let yourself die* and white made a mistake and didn't capture you?

*But the outside is quite nice so maybe not such a mistake.
Author:  Kirby [ Mon Oct 19, 2015 12:48 pm ]
Post subject:  Re: Silly Reading MIstake From Yesterday's Game
Uberdude wrote:
Are you saying black has a good move now to save the corner, but you made a mistake and didn't play it? Because I can't see one. Or the mistake was earlier to let yourself die* and white made a mistake and didn't capture you?

*But the outside is quite nice so maybe not such a mistake.


Black has a good move now, which can help the corner. I was white, and I tenuki'd to play the marked move:

Click Here To Show Diagram Code
[go]$$
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X , . . . . . O . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . O . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . X X X . |
$$ | . . . , . . . . . , . . . . . O X O . |
$$ | . . . . . . . . . . . . . . X X O X O |
$$ | . . . . . . . . . . . . . . X O O X . |
$$ | . . . . . . . . . . X . . . X O O . O |
$$ | . . . . . . . . . . . . X . X O . O O |
$$ | . . . . . . . . . . X O O O X O O X O |
$$ | . . . O . . . . . , X X O . O X X X O |
$$ | . . . . . W . . . . X O X O O . X . X |
$$ | . . . . . . . . . . . . X X O O X O X |
$$ | . . . . . . . . . . . . . X . O X O . |
$$ ---------------------------------------[/go]


This tenuki was a mistake. My opponent still let me capture the corner in the game.
Author:  Jhyn [ Mon Oct 19, 2015 12:51 pm ]
Post subject:  Re: Silly Reading MIstake From Yesterday's Game
I won't post the move to let the others work, but it is indeed a big blind spot. I wouldn't go so far as to call it a silly reading mistake.
Author:  MMaestro [ Mon Oct 19, 2015 12:52 pm ]
Post subject:  Re: Silly Reading MIstake From Yesterday's Game
Black puts 5 stones into almost atari on the first line from the outside. Then you can either make a shortage of liberties on the outside group or gain a liberty to kill the right side white group?
Author:  Kirby [ Mon Oct 19, 2015 12:59 pm ]
Post subject:  Re: Silly Reading MIstake From Yesterday's Game
MMaestro wrote:
Black puts 5 stones into almost atari on the first line from the outside. Then you can either make a shortage of liberties on the outside group or gain a liberty to kill the right side white group?


Yes, exactly!

Details are hidden:
I tenuki'd, because I read out the right side and the bottom side in isolation. Not together.

So I thinking of only the bottom side, the marked move seems silly:
Click Here To Show Diagram Code
[go]$$
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X , . . . . . O . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . O . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . X X X . |
$$ | . . . , . . . . . , . . . . . O X O . |
$$ | . . . . . . . . . . . . . . X X O X O |
$$ | . . . . . . . . . . . . . . X O O X . |
$$ | . . . . . . . . . . X . . . X O O . O |
$$ | . . . . . . . . . . . . X . X O . O O |
$$ | . . . . . . . . . . X O O O X O O X O |
$$ | . . . O . . . . . , X X O . O X X X O |
$$ | . . . . . O . . . . X O X O O . X . X |
$$ | . . . . . . . . . . . . X X O O X O X |
$$ | . . . . . . . . . . . . . X B O X O . |
$$ ---------------------------------------[/go]



After all, black is just letting himself get captured, right?

Click Here To Show Diagram Code
[go]$$
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X , . . . . . O . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . O . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . X X X . |
$$ | . . . , . . . . . , . . . . . O X O . |
$$ | . . . . . . . . . . . . . . X X O X O |
$$ | . . . . . . . . . . . . . . X O O X . |
$$ | . . . . . . . . . . X . . . X O O . O |
$$ | . . . . . . . . . . . . X . X O . O O |
$$ | . . . . . . . . . . X O O O X O O X O |
$$ | . . . O . . . . . , X X O . O X X X O |
$$ | . . . . . O . . . . X O X O O . X . X |
$$ | . . . . . . . . . . . 2 X X O O X O X |
$$ | . . . . . . . . . . . . . X 1 O X O . |
$$ ---------------------------------------[/go]




But the story doesn't end there - even though my reading did in the game :-) Black can then proceed with the capturing race on the right side.

Click Here To Show Diagram Code
[go]$$
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X , . . . . . O . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . O . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . X X X . |
$$ | . . . , . . . . . , . . . . . O X C 3 |
$$ | . . . . . . . . . . . . . . X X O X O |
$$ | . . . . . . . . . . . . . . X O O X . |
$$ | . . . . . . . . . . X . . . X O O . O |
$$ | . . . . . . . . . . . . X . X O . O O |
$$ | . . . . . . . . . . X O O O X O O X O |
$$ | . . . O . . . . . , X X O . O X X X O |
$$ | . . . . . O . . . . X O X O O a X . X |
$$ | . . . . . . . . . . . 2 X X O O X O X |
$$ | . . . . . . . . . . . . . X 1 O X O . |
$$ ---------------------------------------[/go]



Before the exchange on the bottom, I could play at 'a' to atari white and win the race. Not true, anymore, because black's "silly" exchange causes a shortage of liberties. I can't do anything but capture the stones, but then black wins the race:
Click Here To Show Diagram Code
[go]$$
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X , . . . . . O . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . O . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . X X X . |
$$ | . . . , . . . . . , . . . . . O X . 3 |
$$ | . . . . . . . . . . . . . . X X O X O |
$$ | . . . . . . . . . . . . . . X O O X . |
$$ | . . . . . . . . . . X . . . X O O 5 O |
$$ | . . . . . . . . . . . . X . X O . O O |
$$ | . . . . . . . . . . X O O O X O O X O |
$$ | . . . O . . . . . , X X O . O X X X O |
$$ | . . . . . O . . . . X O X O O a X . X |
$$ | . . . . . . . . . . . 2 X X O O X O X |
$$ | . . . . . . . . . . . . 4 X 1 O X O . |
$$ ---------------------------------------[/go]



Therefore, capturing black when he plays on the first line doesn't work. But if I save the right side, now my other group is dead:

Click Here To Show Diagram Code
[go]$$
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X , . . . . . O . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . O . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . X X X . |
$$ | . . . , . . . . . , . . . . . O X O 2 |
$$ | . . . . . . . . . . . . . . X X O X O |
$$ | . . . . . . . . . . . . . . X O O X . |
$$ | . . . . . . . . . . X . . . X O O . O |
$$ | . . . . . . . . . . . . X . X O . O O |
$$ | . . . . . . . . . . X O O O X O O X O |
$$ | . . . O . . . . . , X X O . O X X X O |
$$ | . . . . . O . . . . X C X O O a X . X |
$$ | . . . . . . . . . . . 3 X X O O X O X |
$$ | . . . . . . . . . . . . . X 1 O X O . |
$$ ---------------------------------------[/go]


I'm again haunted by 'a', and can't kill black anymore.

Kind of a cool shape, but it was my blindspot during the game :-)
Author:  Uberdude [ Mon Oct 19, 2015 2:17 pm ]
Post subject:  Re: Silly Reading Mistake From Yesterday's Game
Oh right, I didn't see that at first. So white should have extended the single stone first as a probe and if black ataris to keep it dead then white can indeed safely tenuki and the corner stays dead.
Author:  Kirby [ Mon Oct 19, 2015 2:56 pm ]
Post subject:  Re: Silly Reading Mistake From Yesterday's Game
Uberdude wrote:
Oh right, I didn't see that at first. So white should have extended the single stone first as a probe and if black ataris to keep it dead then white can indeed safely tenuki and the corner stays dead.


Yes, I should have done that.
Author:  DrStraw [ Mon Oct 19, 2015 3:53 pm ]
Post subject:  Re: Silly Reading MIstake From Yesterday's Game
Looks like a play at A does it as it stops white from placing black in atari.

Click Here To Show Diagram Code
[go]$$
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X , . . . . . O . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . O . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . X X X . |
$$ | . . . , . . . . . , . . . . . O X O . |
$$ | . . . . . . . . . . . . . . X X O X O |
$$ | . . . . . . . . . . . . . . X O O X . |
$$ | . . . . . . . . . . X . . . X O O . O |
$$ | . . . . . . . . . . . . X . X O . O O |
$$ | . . . . . . . . . . X O O O X O O X O |
$$ | . . . O . . . . . , X X O . O X X X O |
$$ | . . . . . W . . . . X O X O O . X . X |
$$ | . . . . . . . . . . . . X X O O X O X |
$$ | . . . . . . . . . . . . . X a O X O . |
$$ ---------------------------------------[/go]
Author:  Bill Spight [ Mon Oct 19, 2015 7:16 pm ]
Post subject:  Re: Silly Reading Mistake From Yesterday's Game
Kirby wrote:
I made a silly reading mistake yesterday during one of my games.


I say bravo for finding the play in the postmortem. :clap: :)
Author:  Uberdude [ Tue Oct 20, 2015 4:22 am ]
Post subject:  Re: Silly Reading Mistake From Yesterday's Game
Kirby wrote:
Uberdude wrote:
Oh right, I didn't see that at first. So white should have extended the single stone first as a probe and if black ataris to keep it dead then white can indeed safely tenuki and the corner stays dead.


Yes, I should have done that.


Actually, should you? It's a weird situation: it seems black's best answer is to take the single stone on the right which threatens to save the corner and kill white on the right, so white should answer that, but is now short or libs to take approach and capture the 4 stones, so black can tenuki to a big place (incidentally I think the top side is bigger than the lower left, so white's move in the game should have been around there).

Click Here To Show Diagram Code
[go]$$W Dia 1
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . 4 . . . . . |
$$ | . . X , . . . . . O . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . O . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . X X X . |
$$ | . . . , . . . . . , . . . . . O X O 2 |
$$ | . . . . . . . . . . . . . . X X O X O |
$$ | . . . . . . . . . . . . . . X O O X . |
$$ | . . . . . . . . . . X . . . X O O . O |
$$ | . . . . . . . . . . . . X . X O . O O |
$$ | . . . . . . . . . . X O O O X O O X O |
$$ | . . . O . . . . . , X X O . O X X X O |
$$ | . . . . . . . . . . X O X O O 3 X . X |
$$ | . . . . . . . . . . . 1 X X O O X O X |
$$ | . . . . . . . . . . . . . X . O X O . |
$$ ---------------------------------------[/go]


In this line the black corner is dead, black's 4 stones (tetris wiggle shape) are alive, and black gets sente. The alternative of the naive answering as below results in black corner dead, 4 stones alive, and white sente, clearly vastly inferior (a is black's privelege so that's the same). 2 is essentially a pass.

Click Here To Show Diagram Code
[go]$$W Dia 2
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . 3 . . . . . |
$$ | . . X , . . . . . O . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . O . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . X X X . |
$$ | . . . , . . . . . , . . . . . O X O a |
$$ | . . . . . . . . . . . . . . X X O X O |
$$ | . . . . . . . . . . . . . . X O O X . |
$$ | . . . . . . . . . . X . . . X O O . O |
$$ | . . . . . . . . . . . . X . X O . O O |
$$ | . . . . . . . . . . X O O O X O O X O |
$$ | . . . O . . . . . , X X O . O X X X O |
$$ | . . . . . . . . . . X O X O O . X . X |
$$ | . . . . . . . . . . 2 1 X X O O X O X |
$$ | . . . . . . . . . . . . . X . O X O . |
$$ ---------------------------------------[/go]


The alternative for white if black captures on the right rather than atari on the 2 is to carry out the threat to take the 4 stones and get sente as below, but as that loses about 40 points in the corner I don't think it's worth it. If there was some huge life and death problem on the other side of the board then it might be.

Click Here To Show Diagram Code
[go]$$W Dia 3 (and a weakness afterwards isn't a big problem but does have some value for white)
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . 5 . . . . . |
$$ | . . X , . . . . . O . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . O . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . X X X . |
$$ | . . . , . . . . . , . . . . . O X O 2 |
$$ | . . . . . . . . . . . . . . X X O X O |
$$ | . . . . . . . . . . . . . . X O O X . |
$$ | . . . . . . . . . . X . . . X O O 4 O |
$$ | . . . . . . . . . . a . X . X O . O O |
$$ | . . . . . . . . . . X O O O X O O X O |
$$ | . . . O . . . . . , X X O . O X X X O |
$$ | . . . . . . . . . . X O X O O . X . X |
$$ | . . . . . . . . . . . 1 X X O O X O X |
$$ | . . . . . . . . . . . . . X 3 O X O . |
$$ ---------------------------------------[/go]


So if white doesn't extend but approaches at the top, and black plays the suicide tesuji to save the corner best play seems to be as below (5 and 6 can be saved for a ko threat, and not sure 7 is best, maybe just a?) in which white gets 2 moves on the outside:

Click Here To Show Diagram Code
[go]$$W Dia 4
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . 1 . . a . . |
$$ | . . X , . . . . . O . . . . . X . . . |
$$ | . . . . . . . . . . . . . . 7 . . . . |
$$ | . . . . . . . . . . . . . . . . O . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . X X X . |
$$ | . . . , . . . . . , . . . . . O X O 4 |
$$ | . . . . . . . . . . . . . . X X O X O |
$$ | . . . . . . . . . . . . . . X O O X . |
$$ | . . . . . . . . . . X . . . X O O 6 O |
$$ | . . . . . . . . . . . . X . X O . O O |
$$ | . . . . . . . . . . X O O O X O O X O |
$$ | . . . O . . . . . , X X O . O X X X O |
$$ | . . . . . . . . . . X O X O O . X . X |
$$ | . . . . . . . . . . . 3 X X O O X O X |
$$ | . . . . . . . . . . . . 5 X 2 O X O . |
$$ ---------------------------------------[/go]


So white has to choose which is best for him: play the extend and then black's best line is to force white to capture black's corner in gote and then tenuki; or white tenuki immediately, black suicides to save the corner and kill the right side white, and white gets another move outside. The corner is so big that I think the former is the best choice for white, but it's not trivial to say that.

So for bonus points the question is, given the chance of white to get 2 moves outside, should white play a more "ko-threaty" move as his tenuki, something which has a more powerful follow-up if ignored? Say an attachment like this?

Click Here To Show Diagram Code
[go]$$W Dia 5
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X , . . . . . O . . . . 1 X . . . |
$$ | . . . . . . . . . . . . . . . 7 . . . |
$$ | . . . . . . . . . . . . . . . . O . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . X X X . |
$$ | . . . , . . . . . , . . . . . O X O 4 |
$$ | . . . . . . . . . . . . . . X X O X O |
$$ | . . . . . . . . . . . . . . X O O X . |
$$ | . . . . . . . . . . X . . . X O O 6 O |
$$ | . . . . . . . . . . . . X . X O . O O |
$$ | . . . . . . . . . . X O O O X O O X O |
$$ | . . . O . . . . . , X X O . O X X X O |
$$ | . . . . . . . . . . X O X O O . X . X |
$$ | . . . . . . . . . . . 3 X X O O X O X |
$$ | . . . . . . . . . . . . 5 X 2 O X O . |
$$ ---------------------------------------[/go]


Then if black takes gote to make the ~40 point gote move in the corner, white's follow-up is better. This is clearly an improvement for white over Dia 4, but is it an improvement over Dia 1, the extension? Probably not, but it's getting closer, and I think it would be plausible to construct another board position where it was. If it is better for white than Dia 1 black could answer the "ko-threat" style move, but if this is a locally slack move then white's best play is to make such threaty attachments and continue so long as black's best answer is to submissively answer, and then after making these beneficial exchanges return to the extension below to complete the gote capture of the black corner. How bizarre!

Edit: having said that, white could have presumably extended the single stone at an earlier point in the fight before the corner had so few liberties and black would have had to answer on the outside.
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