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

Visualize whirled peas.

Everything with love. Stay safe.

Apologies to all for the claim that Wang and Zen both erred. I miscounted, I am afraid.

Boy! First I don't check whether Black got the last play, just assuming that weiqitv was right, and then I miscount results. Boy is my face red!

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

Visualize whirled peas.

Everything with love. Stay safe.

OK. Well, to redeem myself a bit, here is the answer to the first question. Black to play and get the last play.

Click Here To Show Diagram Code

[go]$$Wc Black to play and get the last play
$$ ---------------------------------------
$$ | . O . . O . X O . . . . . . . X . X . |
$$ | . . O . O X O . O O . X X X X . X O . |
$$ | . X X O . O O O X O O X O O . X O . . |
$$ | . . O O O X X X X X O O O X . X . O . |
$$ | . . X O X X . . . O O . X O . X X X . |
$$ | . X O X O O X . X X O . X O O O O X X |
$$ | O O O . . O X . . . X . X O . O . O O |
$$ | . O O O . O X . . . . . X X O O O X . |
$$ | O O X O O X . . . . . . . O X O O O . |
$$ | X X X O X X . . . , . . . . X X X O . |
$$ | O . O X X . . . . . . . . . . X . X . |
$$ | . O O O X . . . . . . . . . . . X . . |
$$ | O O X X . . . . . X X X X O . . . . . |
$$ | X X . X . . . . X O O O O X X . . . . |
$$ | . O X . X . . X O O . . . O X X . . . |
$$ | O . O X X X X X X O . O O O O X X . . |
$$ | . O O O X O O X O X X O . . . O O X . |
$$ | . . O . O . . O O . O . O . O X O X . |
$$ | . . . O . O O . . . . O . O . X . X . |
$$ ---------------------------------------[/go]

There is more than one answer, but this is the most accurate way.

Click Here To Show Diagram Code

[go]$$Bc Black to play and get the last play
$$ ---------------------------------------
$$ | . O . . O . X O . . 1 . . . . X . X . |
$$ | . . O . O X O . O O . X X X X . X O . |
$$ | . X X O . O O O X O O X O O . X O . . |
$$ | . . O O O X X X X X O O O X . X . O . |
$$ | . . X O X X . 3 2 O O . X O . X X X . |
$$ | . X O X O O X . X X O 4 X O O O O X X |
$$ | O O O . . O X . . . X 5 X O . O . O O |
$$ | . O O O . O X . . . . . X X O O O X . |
$$ | O O X O O X . . . . . . . O X O O O . |
$$ | X X X O X X . . . , . . . . X X X O . |
$$ | O . O X X . . . . . . . . . . X . X . |
$$ | . O O O X . . . . . . . . . . . X . . |
$$ | O O X X . . . . . X X X X O . . . . . |
$$ | X X . X . . . . X O O O O X X . . . . |
$$ | . O X . X . . X O O . . . O X X . . . |
$$ | O . O X X X X X X O . O O O O X X . . |
$$ | . O O O X O O X O X X O . . . O O X . |
$$ | . . O . O . . O O . O . O . O X O X . |
$$ | . . . O . O O . . . . O . O . X . X . |
$$ ---------------------------------------[/go]

After White takes his sente and then there are a few variations for .

Click Here To Show Diagram Code

[go]$$Wcm6 Variation 1
$$ ---------------------------------------
$$ | . O . . O . X O . a X . . . . X . X . |
$$ | . . O . O X O . O O b X X X X . X O . |
$$ | . X X O . O O O X O O X O O . X O . . |
$$ | . . O O O X X X X X O O O X 1 X . O . |
$$ | . . X O X X . X O O O . X O . X X X . |
$$ | . X O X O O X . X X O O X O O O O X X |
$$ | O O O . . O X . . . X X X O . O . O O |
$$ | . O O O . O X . . . . . X X O O O X . |
$$ | O O X O O X . . . . . . . O X O O O 3 |
$$ | X X X O X X . . . , . . . . X X X O 2 |
$$ | O . O X X . . . . . . . . . . X . X 4 |
$$ | . O O O X . . . . . . . . . . . X . . |
$$ | O O X X . . . . . X X X X O . . . . . |
$$ | X X . X . . . . X O O O O X X . . . . |
$$ | . O X . X . . X O O . . . O X X . . . |
$$ | O . O X X X X X X O . O O O O X X . . |
$$ | . O O O X O O X O X X O . . . O O X . |
$$ | . . O . O . . O O . O . O . O X O X . |
$$ | . . . O . O O . . . . O . O . X . X . |
$$ ---------------------------------------[/go]

takes one stone. Then Black simply takes the hane-and-connect, leaving "a" and "b" miai.

Click Here To Show Diagram Code

[go]$$Wcm6 Variation 2
$$ ---------------------------------------
$$ | . O . . O a X O . 5 X . . . . X . X . |
$$ | . . O . O X O . O O 6 X X X X . X O . |
$$ | . X X O . O O O X O O X O O . X O . . |
$$ | . . O O O X X X X X O O O X 4 X . O . |
$$ | . . X O X X . X O O O . X O . X X X . |
$$ | . X O X O O X . X X O O X O O O O X X |
$$ | O O O . . O X . . . X X X O . O . O O |
$$ | . O O O . O X . . . . . X X O O O X . |
$$ | O O X O O X . . . . . . . O X O O O , |
$$ | X X X O X X . . . , . . . . X X X O 3 |
$$ | O . O X X . . . . . . . . . . X . X 1 |
$$ | . O O O X . . . . . . . . . . . X . 2 |
$$ | O O X X . . . . . X X X X O . . . . . |
$$ | X X . X . . . . X O O O O X X . . . . |
$$ | . O X . X . . X O O . . . O X X . . . |
$$ | O . O X X X X X X O . O O O O X X . . |
$$ | . O O O X O O X O X X O . . . O O X . |
$$ | . . O . O . . O O . O . O . O X O X . |
$$ | . . . O . O O . . . . O . O . X . X . |
$$ ---------------------------------------[/go]

If White takes the hane-and-connect, is sente. If Black now gets to play at 10, White will have to make a protective play at "a". is the last play.

Click Here To Show Diagram Code

[go]$$Wcm6 Variation 3
$$ ---------------------------------------
$$ | . O . . O . X O . 1 X . . . . X . X . |
$$ | . . O . O X O . O O 2 X X X X . X O . |
$$ | . X X O . O O O X O O X O O . X O . . |
$$ | . . O O O X X X X X O O O X a X . O . |
$$ | . . X O X X . X O O O . X O . X X X . |
$$ | . X O X O O X . X X O O X O O O O X X |
$$ | O O O . . O X . . . X X X O . O . O O |
$$ | . O O O . O X . . . . . X X O O O X . |
$$ | O O X O O X . . . . . . . O X O O O . |
$$ | X X X O X X . . . , . . . . X X X O . |
$$ | O . O X X . . . . . . . . . . X . X . |
$$ | . O O O X . . . . . . . . . . . X . . |
$$ | O O X X . . . . . X X X X O . . . . . |
$$ | X X . X . . . . X O O O O X X . . . . |
$$ | . O X . X . . X O O . . . O X X . . . |
$$ | O . O X X X X X X O . O O O O X X . . |
$$ | . O O O X O O X O X X O . . . O O X . |
$$ | . . O . O . . O O . O . O . O X O X . |
$$ | . . . O . O O . . . . O . O . X . X . |
$$ ---------------------------------------[/go]

If , gets the last play, leaving "a" and the hane-and-connect as miai.

Click Here To Show Diagram Code

[go]$$Wcm6 Variation 4
$$ ---------------------------------------
$$ | . O . . O a X O . 2 X . . . . X . X . |
$$ | . . O . O X O . O O 1 X X X X . X O . |
$$ | . X X O . O O O X O O X O O . X O . . |
$$ | . . O O O X X X X X O O O X 3 X . O . |
$$ | . . X O X X . X O O O . X O . X X X . |
$$ | . X O X O O X . X X O O X O O O O X X |
$$ | O O O . . O X . . . X X X O . O . O O |
$$ | . O O O . O X . . . . . X X O O O X . |
$$ | O O X O O X . . . . . . . O X O O O 5 |
$$ | X X X O X X . . . , . . . . X X X O 4 |
$$ | O . O X X . . . . . . . . . . X . X 6 |
$$ | . O O O X . . . . . . . . . . . X . . |
$$ | O O X X . . . . . X X X X O . . . . . |
$$ | X X . X . . . . X O O O O X X . . . . |
$$ | . O X . X . . X O O . . . O X X . . . |
$$ | O . O X X X X X X O . O O O O X X . . |
$$ | . O O O X O O X O X X O . . . O O X . |
$$ | . . O . O . . O O . O . O . O X O X . |
$$ | . . . O . O O . . . . O . O . X . X . |
$$ ---------------------------------------[/go]

If , is sente because of the threat to take away the point at "a". After Black takes the hane-and-connect to get the last play.

Failure Diagram

Click Here To Show Diagram Code

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

looks plausible, as it sets up the eventual threat to force a protective play. However, after White takes his sente, he plays , which leaves two hane-and-connects on the board and gets the last play.

Taking the hane-and connect on the right also fails, for the same reason.

Curiously, playing a reverse sente works, because Black can get the last play, even if White plays first. That's the subject of my next note.

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

Visualize whirled peas.

Everything with love. Stay safe.

Back to the actual game. Here is play at temperature 1.

Click Here To Show Diagram Code

[go]$$Wcm34 Black gets the last play
$$ ---------------------------------------
$$ | . O . . O b X O . a 5 8 . . . X . X . |
$$ | . . O . O X O . O O 6 X X X X . X O . |
$$ | . X X O . O O O X O O X O O . X O . . |
$$ | . . O O O X X X X X O O O X 7 X . O . |
$$ | . . X O X X . 2 1 O O . X O . X X X . |
$$ | . X O X O O X . X X O 3 X O O O O X X |
$$ | O O O . . O X . . . X 4 X O . O . O O |
$$ | . O O O . O X . . . . . X X O O O X . |
$$ | O O X O O X . . . . . . . O X O O O . |
$$ | X X X O X X . . . , . . . . X X X O . |
$$ | O . O X X . . . . . . . . . . X . X . |
$$ | . O O O X . . . . . . . . . . . X . . |
$$ | O O X X . . . . . X X X X O . . . . . |
$$ | X X . X . . . . X O O O O X X . . . . |
$$ | . X X . X . . X O O . . . O X X . . . |
$$ | O X O X X X X X X O . O O O O X X . . |
$$ | . O O O X O O X O X X O . . . O O X . |
$$ | . . O . O . . O O . O . O . O . O X . |
$$ | . . . O . O O . . . . O . O . O X X . |
$$ ---------------------------------------[/go]

White starts by taking his sente, and then plays the kosumi, White 238. Black replies with Black 239. For quite a while I thought that both of these moves were mistakes, but that was because of miscounting. White 240 was a good play. If White plays there and at "a", Black will need a protective play at "b". But then Black 241 makes miai of "a" and the hane-and-connect on the right side, and gets the last play.

Even though they were not mistakes, I still think that White 238 and Black 239 were not good technique in a fight for the last play. Why?

Click Here To Show Diagram Code

[go]$$Wc Gives Black extra chances
$$ ---------------------------------------
$$ | . O . . O . X O . . 1 a b c . X . X . |
$$ | . . O . O X O . O O . X X X X . X O . |
$$ | . X X O . O O O X O O X O O . X O . . |
$$ | . . O O O X X X X X O O O X 2 X . O . |
$$ | . . X O X X . X O O O . X O . X X X . |
$$ | . X O X O O X . X X O O X O O O O X X |
$$ | O O O . . O X . . . X X X O . O . O O |
$$ | . O O O . O X . . . . . X X O O O X . |
$$ | O O X O O X . . . . . . . O X O O O . |
$$ | X X X O X X . . . , . . . . X X X O . |
$$ | O . O X X . . . . . . . . . . X . X . |
$$ | . O O O X . . . . . . . . . . . X . . |
$$ | O O X X . . . . . X X X X O . . . . . |
$$ | X X . X . . . . X O O O O X X . . . . |
$$ | . X X . X . . X O O . . . O X X . . . |
$$ | O X O X X X X X X O . O O O O X X . . |
$$ | . O O O X O O X O X X O . . . O O X . |
$$ | . . O . O . . O O . O . O . O . O X . |
$$ | . . . O . O O . . . . O . O . O X X . |
$$ ---------------------------------------[/go]

gives Black extra chances to get the last play after Black plays . Any of "a", "b", or "c" might be the last play of the game, thanks to . See details below.

Click Here To Show Diagram Code

[go]$$Wc Black gives them back, and more
$$ ---------------------------------------
$$ | . O . . O . X O . a 1 . . . . X . X . |
$$ | . . O . O X O . O O 2 X X X X . X O . |
$$ | . X X O . O O O X O O X O O . X O . . |
$$ | . . O O O X X X X X O O O X 3 X . O . |
$$ | . . X O X X . X O O O . X O . X X X . |
$$ | . X O X O O X . X X O O X O O O O X X |
$$ | O O O . . O X . . . X X X O . O . O O |
$$ | . O O O . O X . . . . . X X O O O X . |
$$ | O O X O O X . . . . . . . O X O O O . |
$$ | X X X O X X . . . , . . . . X X X O . |
$$ | O . O X X . . . . . . . . . . X . X . |
$$ | . O O O X . . . . . . . . . . . X . . |
$$ | O O X X . . . . . X X X X O . . . . . |
$$ | X X . X . . . . X O O O O X X . . . . |
$$ | . X X . X . . X O O . . . O X X . . . |
$$ | O X O X X X X X X O . O O O O X X . . |
$$ | . O O O X O O X O X X O . . . O O X . |
$$ | . . O . O . . O O . O . O . O . O X . |
$$ | . . . O . O O . . . . O . O . O X X . |
$$ ---------------------------------------[/go]

But Zen turns right around and gives those extra chances back, with interest. After , White will get the last local play at "a", regardless of who goes first. The next diagram shows technically better play for Black.

Click Here To Show Diagram Code

[go]$$Wc
$$ ---------------------------------------
$$ | . O . . O a X O . 5 1 3 9 0 . X . X . |
$$ | . . O . O X O . O O 4 X X X X . X O . |
$$ | . X X O . O O O X O O X O O . X O . . |
$$ | . . O O O X X X X X O O O X 2 X . O . |
$$ | . . X O X X . X O O O . X O . X X X . |
$$ | . X O X O O X . X X O O X O O O O X X |
$$ | O O O . . O X . . . X X X O . O . O O |
$$ | . O O O . O X . . . . . X X O O O X . |
$$ | O O X O O X . . . . . . . O X O O O 7 |
$$ | X X X O X X . . . , . . . . X X X O 6 |
$$ | O . O X X . . . . . . . . . . X . X 8 |
$$ | . O O O X . . . . . . . . . . . X . . |
$$ | O O X X . . . . . X X X X O . . . . . |
$$ | X X . X . . . . X O O O O X X . . . . |
$$ | . X X . X . . X O O . . . O X X . . . |
$$ | O X O X X X X X X O . O O O O X X . . |
$$ | . O O O X O O X O X X O . . . O O X . |
$$ | . . O . O . . O O . O . O . O . O X . |
$$ | . . . O . O O . . . . O . O . O X X . |
$$ ---------------------------------------[/go]

makes sente, because if White then allows Black to play at 5, White must make a protective play at "a". So is not the last play. Next, Black takes the hane-and-connect and then gets the last play with .

So what is technically correct play for White?

Click Here To Show Diagram Code

[go]$$Wc
$$ ---------------------------------------
$$ | . O . . O . X O . . . . . . . X . X . |
$$ | . . O . O X O . O O . X X X X . X O . |
$$ | . X X O . O O O X O O X O O . X O . . |
$$ | . . O O O X X X X X O O O B 1 X . O . |
$$ | . . X O X X . X O O O . X O . X X X . |
$$ | . X O X O O X . X X O O X O O O O X X |
$$ | O O O . . O X . . . X X X O . O . O O |
$$ | . O O O . O X . . . . . X X O O O X . |
$$ | O O X O O X . . . . . . . O X O O O . |
$$ | X X X O X X . . . , . . . . X X X O . |
$$ | O . O X X . . . . . . . . . . X . X . |
$$ | . O O O X . . . . . . . . . . . X . . |
$$ | O O X X . . . . . X X X X O . . . . . |
$$ | X X . X . . . . X O O O O X X . . . . |
$$ | . X X . X . . X O O . . . O X X . . . |
$$ | O X O X X X X X X O . O O O O X X . . |
$$ | . O O O X O O X O X X O . . . O O X . |
$$ | . . O . O . . O O . O . O . O . O X . |
$$ | . . . O . O O . . . . O . O . O X X . |
$$ ---------------------------------------[/go]

I think that there are two candidates. The first one is to take the stone with . That simplifies the play, but Black has to thread the needle.

Click Here To Show Diagram Code

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

The second one is the hane-and-connect. It leaves a more complicated position for Black to solve.

Edit: Actually, the hane-and-connect is not technically correct. The abutment at L-18 is, as well as the capture of the Black stone. But abutment gives Black no chance to go wrong.

You may wish to figure out how Black gets the last play in each of these positions.

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

Visualize whirled peas.

Everything with love. Stay safe.

Actually, the hane-and-connect is not technically correct. We can show that with a difference game.

Click Here To Show Diagram Code

[go]$$W Difference game
$$ ---------------------------------------
$$ | . . . . O . X O . . . . . . . X . X . |
$$ | . . . . O X O . O O . X X X X . X O . |
$$ | . . . O . O O O X O O X O O . X O . . |
$$ | . . . O O X X X X X O O O X . X . O . |
$$ | . . . O X X . X O O O . X O . X X X . |
$$ | . . . . O O X . X X O O X O O O O X X |
$$ | . . . . . O X . . . X X X O . O . O O |
$$ | . . O . . O X . . . . . X X O O O X . |
$$ | . O . O . . . . . . . . . . X O O O . |
$$ | . X O O O . . . . _ . . . . X X X O W |
$$ | . X X X O . . . . . . . . . . X . X W |
$$ | . O X X X O O . . . . . O X . . X . B |
$$ | X X . X . X O O O . . . O X . . . . . |
$$ | O O X X X X O X X O O . O X X . . . . |
$$ | . O O O . X O . X X X O . O O X . . . |
$$ | . X . O B W X X X O O O O O X X . . . |
$$ | . . X O . X X O X X O X X X . X . . . |
$$ | . X O . O O O O . X X . X O X . . . . |
$$ | . O . O . . . . . . . X O . X . . . . |
$$ ---------------------------------------[/go]

We set up the difference game by setting up the mirror position and then giving White one play in one position and Black the other play in the mirror position. (The middle becomes no man's land, OC.) Is either player better off after the exchange?)

First question: Can Black to play win?

Click Here To Show Diagram Code

[go]$$B Black plays first
$$ ---------------------------------------
$$ | . . . . O a X O . 4 5 . . . . X . X . |
$$ | . . . . O X O . O O 1 X X X X . X O . |
$$ | . . . O . O O O X O O X O O . X O . . |
$$ | . . . O O X X X X X O O O X 3 X . O . |
$$ | . . . O X X . X O O O . X O . X X X . |
$$ | . . . . O O X . X X O O X O O O O X X |
$$ | . . . . . O X . . . X X X O . O . O O |
$$ | . . O . . O X . . . . . X X O O O X . |
$$ | . O . O . . . . . . . . . . X O O O . |
$$ | . X O O O . . . . _ . . . . X X X O O |
$$ | . X X X O . . . . . . . . . . X . X O |
$$ | . O X X X O O . . . . . O X . . X . X |
$$ | X X . X . X O O O . . . O X . . . . . |
$$ | O O X X X X O X X O O . O X X . . . . |
$$ | . O O O . X O . X X X O . O O X . . . |
$$ | . X . O X . X X X O O O O O X X . . . |
$$ | . . X O . X X O X X O X X X . X . . . |
$$ | . X O . O O O O 2 X X . X O X . . . . |
$$ | . O . O . . . . . . . X O . X . . . . |
$$ ---------------------------------------[/go]

is an interesting play. If mirrors, the board may look like miai, but is sente. White must play to prevent having to make a protective play at "a", and gets the last play to win by 1 pt.

Click Here To Show Diagram Code

[go]$$B Black plays first
$$ ---------------------------------------
$$ | . . . . O . X O . . . . . . . X . X . |
$$ | . . . . O X O . O O 1 X X X X . X O . |
$$ | . . . O . O O O X O O X O O . X O . . |
$$ | . . . O O X X X X X O O O X 2 X . O . |
$$ | . . . O X X . X O O O . X O . X X X . |
$$ | . . . . O O X . X X O O X O O O O X X |
$$ | . . . . . O X . . . X X X O . O . O O |
$$ | . . O . . O X . . . . . X X O O O X . |
$$ | . O . O . . . . . . . . . . X O O O . |
$$ | . X O O O . . . . _ . . . . X X X O O |
$$ | . X X X O . . . . . . . . . . X . X O |
$$ | . O X X X O O . . . . . O X . . X . X |
$$ | X X . X . X O O O . . . O X . . . . . |
$$ | O O X X X X O X X O O . O X X . . . . |
$$ | . O O O . X O . X X X O . O O X . . . |
$$ | . X . O X . X X X O O O O O X X . . . |
$$ | . . X O . X X O X X O X X X . X . . . |
$$ | . X O . O O O O 4 X X . X O X . . . . |
$$ | . O . O . . 6 5 3 7 . X O . X . . . . |
$$ ---------------------------------------[/go]

If Black gets the sente, he obviously wins, so let prevent it. Now Black leaves the two hane-and-connects as miai and plays on the bottom to get the last play and win.

Second question: Can White to play win? If not, Black's play, capturing the single stone, is technically superior to the hane-and-connect.

Click Here To Show Diagram Code

[go]$$W White plays first
$$ ---------------------------------------
$$ | . . . . O . X O . . . . . . . X . X . |
$$ | . . . . O X O . O O 1 X X X X . X O . |
$$ | . . . O . O O O X O O X O O . X O . . |
$$ | . . . O O X X X X X O O O X . X . O . |
$$ | . . . O X X . X O O O . X O . X X X . |
$$ | . . . . O O X . X X O O X O O O O X X |
$$ | . . . . . O X . . . X X X O . O . O O |
$$ | . . O . . O X . . . . . X X O O O X . |
$$ | . O . O . . . . . . . . . . X O O O . |
$$ | . X O O O . . . . _ . . . . X X X O O |
$$ | . X X X O . . . . . . . . . . X . X O |
$$ | . O X X X O O . . . . . O X . . X . X |
$$ | X X . X . X O O O . . . O X . . . . . |
$$ | O O X X X X O X X O O . O X X . . . . |
$$ | . O O O . X O . X X X O . O O X . . . |
$$ | . X . O X . X X X O O O O O X X . . . |
$$ | . . X O . X X O X X O X X X . X . . . |
$$ | . X O . O O O O 2 X X . X O X . . . . |
$$ | . O . O . . . . . . . X O . X . . . . |
$$ ---------------------------------------[/go]

OC, one way to prevent is to play . But then makes both the top and bottom miai and gets jigo.

Click Here To Show Diagram Code

[go]$$W White plays first
$$ ---------------------------------------
$$ | . . . . O . X O . . . . . . . X . X . |
$$ | . . . . O X O . O O 2 X X X X . X O . |
$$ | . . . O . O O O X O O X O O . X O . . |
$$ | . . . O O X X X X X O O O X 3 X . O . |
$$ | . . . O X X . X O O O . X O . X X X . |
$$ | . . . . O O X . X X O O X O O O O X X |
$$ | . . . . . O X . . . X X X O . O . O O |
$$ | . . O . . O X . . . . . X X O O O X . |
$$ | . O . O . . . . . . . . . . X O O O . |
$$ | . X O O O . . . . _ . . . . X X X O O |
$$ | . X X X O . . . . . . . . . . X . X O |
$$ | . O X X X O O . . . . . O X . . X . X |
$$ | X X . X . X O O O . . . O X . . . . . |
$$ | O O X X X X O X X O O . O X X . . . . |
$$ | . O O O . X O . X X X O . O O X . . . |
$$ | . X . O X . X X X O O O O O X X . . . |
$$ | . . X O . X X O X X O X X X . X . . . |
$$ | . X O . O O O O a X X . X O X . . . . |
$$ | . O . O . . . . 1 b . X O . X . . . . |
$$ ---------------------------------------[/go]

is a clever play. Now if , White can play , which leaves the two hane-and-connects miai, as well as "a" and "b". White wins. Similarly, if Black plays at 3, White replies at 2, and wins.

Click Here To Show Diagram Code

[go]$$W White plays first
$$ ---------------------------------------
$$ | . . . . O c X O . 3 2 . . . . X . X . |
$$ | . . . . O X O . O O 4 X X X X . X O . |
$$ | . . . O . O O O X O O X O O . X O . . |
$$ | . . . O O X X X X X O O O X a X . O . |
$$ | . . . O X X . X O O O . X O . X X X . |
$$ | . . . . O O X . X X O O X O O O O X X |
$$ | . . . . . O X . . . X X X O . O . O O |
$$ | . . O . . O X . . . . . X X O O O X . |
$$ | b O . O . . . . . . . . . . X O O O . |
$$ | . X O O O . . . . _ . . . . X X X O O |
$$ | . X X X O . . . . . . . . . . X . X O |
$$ | . O X X X O O . . . . . O X . . X . X |
$$ | X X . X . X O O O . . . O X . . . . . |
$$ | O O X X X X O X X O O . O X X . . . . |
$$ | . O O O . X O . X X X O . O O X . . . |
$$ | . X . O X . X X X O O O O O X X . . . |
$$ | . . X O . X X O X X O X X X . X . . . |
$$ | . X O . O O O O . X X . X O X . . . . |
$$ | . O . O . . . . 1 . . X O . X . . . . |
$$ ---------------------------------------[/go]

So Black responds with . Now if White plays at "a" to make 3 and 4 miai, Black plays the hane-and-connect at "b" to get a mirror position and jigo. So to protect the point at "a" White blocks with , but then leaves "a" and "b" miai and gets jigo.

Click Here To Show Diagram Code

[go]$$W White plays first
$$ ---------------------------------------
$$ | . . . . O a X O . 5 1 3 7 8 . X . X . |
$$ | . . . . O X O . O O 4 X X X X . X O . |
$$ | . . . O . O O O X O O X O O . X O . . |
$$ | . . . O O X X X X X O O O X 2 X . O . |
$$ | . . . O X X . X O O O . X O . X X X . |
$$ | . . . . O O X . X X O O X O O O O X X |
$$ | . . . . . O X . . . X X X O . O . O O |
$$ | . . O . . O X . . . . . X X O O O X . |
$$ | . O . O . . . . . . . . . . X O O O . |
$$ | . X O O O . . . . _ . . . . X X X O O |
$$ | . X X X O . . . . . . . . . . X . X O |
$$ | . O X X X O O . . . . . O X . . X . X |
$$ | X X . X . X O O O . . . O X . . . . . |
$$ | O O X X X X O X X O O . O X X . . . . |
$$ | . O O O . X O . X X X O . O O X . . . |
$$ | . X . O X . X X X O O O O O X X . . . |
$$ | . . X O . X X O X X O X X X . X . . . |
$$ | . X O . O O O O 6 X X . X O X . . . . |
$$ | . O . O . . . . . . . X O . X . . . . |
$$ ---------------------------------------[/go]

is another potential answer to Black's threat on the top. But then gives Black the last play in the top corridor. After , forces to protect "a". Then Black gets for jigo.

Capturing the single stone is technically superior to the hane-and-connect.

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

Visualize whirled peas.

Everything with love. Stay safe.

Earlier I said that the kosumi in the actual game was not technically correct. We can show that with a difference game, too.

Click Here To Show Diagram Code

[go]$$W Difference game, kosumi vs. capture
$$ ---------------------------------------
$$ | . . . . O . X O . . W . . . . X . X . |
$$ | . . . . O X O . O O . X X X X . X O . |
$$ | . . . O . O O O X O O X O O . X O . . |
$$ | . . . O O X X X X X O O O X . X . O . |
$$ | . . . O X X . X O O O . X O . X X X . |
$$ | . . . . O O X . X X O O X O O O O X X |
$$ | . . . . . O X . . . X X X O . O . O O |
$$ | . . O . . O X . . . . . X X O O O X . |
$$ | . O . O . . . . . . . . . . X O O O . |
$$ | . X O O O . . . . _ . . . . X X X O . |
$$ | . X X X O . . . . . . . . . . X . X . |
$$ | . O X X X O O . . . . . O X . . X . . |
$$ | X X . X . X O O O . . . O X . . . . . |
$$ | O O X X X X O X X O O . O X X . . . . |
$$ | . O O O . X O . X X X O . O O X . . . |
$$ | . X . O B W X X X O O O O O X X . . . |
$$ | . . X O . X X O X X O X X X . X . . . |
$$ | . X O . O O O O . X X . X O X . . . . |
$$ | . O . O . . . . . . . X O . X . . . . |
$$ ---------------------------------------[/go]

Note that the two hane-and-connects are miai, so we can ignore them in the play.

First question: Can Black to play win?

Click Here To Show Diagram Code

[go]$$B Black first
$$ ---------------------------------------
$$ | . . . . O . X O . 4 O 2 6 7 . X . X . |
$$ | . . . . O X O . O O 3 X X X X . X O . |
$$ | . . . O . O O O X O O X O O . X O . . |
$$ | . . . O O X X X X X O O O X 1 X . O . |
$$ | . . . O X X . X O O O . X O . X X X . |
$$ | . . . . O O X . X X O O X O O O O X X |
$$ | . . . . . O X . . . X X X O . O . O O |
$$ | . . O . . O X . . . . . X X O O O X . |
$$ | . O . O . . . . . . . . . . X O O O . |
$$ | . X O O O . . . . _ . . . . X X X O . |
$$ | . X X X O . . . . . . . . . . X . X . |
$$ | . O X X X O O . . . . . O X . . X . . |
$$ | X X . X . X O O O . . . O X . . . . . |
$$ | O O X X X X O X X O O . O X X . . . . |
$$ | . O O O . X O . X X X O . O O X . . . |
$$ | . X . O X . X X X O O O O O X X . . . |
$$ | . . X O . X X O X X O X X X . X . . . |
$$ | . X O . O O O O 8 X X . X O X . . . . |
$$ | . O . O . . 0 9 5 a . X O . X . . . . |
$$ ---------------------------------------[/go]

@ "a"

Yes, Black to play wins. is, as we know, the key play to separate the White groups and make sente. White offers the most stubborn resistance. After Black has only one play to win. is sente, but Black gets the last play on the bottom side. Note that is good after Black has united his groups.

Click Here To Show Diagram Code

[go]$$B Black first, variation 1
$$ ---------------------------------------
$$ | . . . . O . X O . 4 O 5 . . . X . X . |
$$ | . . . . O X O . O O 3 X X X X . X O . |
$$ | . . . O . O O O X O O X O O . X O . . |
$$ | . . . O O X X X X X O O O X 1 X . O . |
$$ | . . . O X X . X O O O . X O . X X X . |
$$ | . . . . O O X . X X O O X O O O O X X |
$$ | . . . . . O X . . . X X X O . O . O O |
$$ | . . O . . O X . . . . . X X O O O X . |
$$ | . O . O . . . . . . . . . . X O O O . |
$$ | . X O O O . . . . _ . . . . X X X O . |
$$ | . X X X O . . . . . . . . . . X . X . |
$$ | . O X X X O O . . . . . O X . . X . . |
$$ | X X . X . X O O O . . . O X . . . . . |
$$ | O O X X X X O X X O O . O X X . . . . |
$$ | . O O O . X O . X X X O . O O X . . . |
$$ | . X . O X . X X X O O O O O X X . . . |
$$ | . . X O . X X O X X O X X X . X . . . |
$$ | . X O . O O O O . X X . X O X . . . . |
$$ | . O . O . . . . 2 . . X O . X . . . . |
$$ ---------------------------------------[/go]

prevents Black from playing there later, but Black wins easily.

Click Here To Show Diagram Code

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

After Black takes her sente with and then switches to the hane-and-connect on the bottom side. Finally, gets the last play.

Question 2: Can White to play win?

Click Here To Show Diagram Code

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

sets a trap. If is sente, because of a possible ko in the corner. Then settles the bottom side, and gets the last play. If each player wins the difference game by playing first, we cannot say that either play is technically superior to the other.

Click Here To Show Diagram Code

[go]$$W White first, Black defense.
$$ ---------------------------------------
$$ | . . . . O . X O . 3 O 1 5 6 . X . X . |
$$ | . . . . O X O . O O 2 X X X X . X O . |
$$ | . . . O . O O O X O O X O O . X O . . |
$$ | . . . O O X X X X X O O O X . X . O . |
$$ | . . . O X X . X O O O . X O . X X X . |
$$ | . . . . O O X . X X O O X O O O O X X |
$$ | . . . . . O X . . . X X X O . O . O O |
$$ | . . O . . O X . . . . . X X O O O X . |
$$ | . O . O . . . . . . . . . . X O O O . |
$$ | . X O O O . . . . _ . . . . X X X O . |
$$ | . X X X O . . . . . . . . . . X . X . |
$$ | . O X X X O O . . . . . O X . . X . . |
$$ | X X . X . X O O O . . . O X . . . . . |
$$ | O O X X X X O X X O O . O X X . . . . |
$$ | . O O O . X O . X X X O . O O X . . . |
$$ | . X . O X . X X X O O O O O X X . . . |
$$ | . . X O . X X O X X O X X X . X . . . |
$$ | . X O . O O O O 4 X X . X O X . . . . |
$$ | . O . O . . . . . . . X O . X . . . . |
$$ ---------------------------------------[/go]

is the defense to get jigo. If , makes miai of the capture of the stone on the top side and the hane-and-connect on the bottom side. gets the last play and jigo.

Click Here To Show Diagram Code

[go]$$W Black defense, variation
$$ ---------------------------------------
$$ | . . . . O . X O . 5 O 1 4 . . X . X . |
$$ | . . . . O X O . O O 2 X X X X . X O . |
$$ | . . . O . O O O X O O X O O . X O . . |
$$ | . . . O O X X X X X O O O X 3 X . O . |
$$ | . . . O X X . X O O O . X O . X X X . |
$$ | . . . . O O X . X X O O X O O O O X X |
$$ | . . . . . O X . . . X X X O . O . O O |
$$ | . . O . . O X . . . . . X X O O O X . |
$$ | . O . O . . . . . . . . . . X O O O . |
$$ | . X O O O . . . . _ . . . . X X X O . |
$$ | . X X X O . . . . . . . . . . X . X . |
$$ | . O X X X O O . . . . . O X . . X . . |
$$ | X X . X . X O O O . . . O X . . . . . |
$$ | O O X X X X O X X O O . O X X . . . . |
$$ | . O O O . X O . X X X O . O O X . . . |
$$ | . X . O X . X X X O O O O O X X . . . |
$$ | . . X O . X X O X X O X X X . X . . . |
$$ | . X O . O O O O 7 X X . X O X . . . . |
$$ | . O . O . . 9 8 6 0 . X O . X . . . . |
$$ ---------------------------------------[/go]

If takes the Black stone, is sente. Then gets the last play on the bottom side, for jigo.

The capture is technically superior to the kosumi, as well.

----

BTW, there is another White play that is not technically inferior to the capture, and that is the play on the second line. As we can see with the following difference game.

Click Here To Show Diagram Code

[go]$$W Difference game, capture vs. abutment
$$ ---------------------------------------
$$ | . . . . O . X O . . . . . . . X . X . |
$$ | . . . . O X O . O O W X X X X . X O . |
$$ | . . . O . O O O X O O X O O . X O . . |
$$ | . . . O O X X X X X O O O X . X . O . |
$$ | . . . O X X . X O O O . X O . X X X . |
$$ | . . . . O O X . X X O O X O O O O X X |
$$ | . . . . . O X . . . X X X O . O . O O |
$$ | . . O . . O X . . . . . X X O O O X . |
$$ | . O . O . . . . . . . . . . X O O O . |
$$ | . X O O O . . . . _ . . . . X X X O . |
$$ | . X X X O . . . . . . . . . . X . X . |
$$ | . O X X X O O . . . . . O X . . X . . |
$$ | X X . X . X O O O . . . O X . . . . . |
$$ | O O X X X X O X X O O . O X X . . . . |
$$ | . O O O . X O . X X X O . O O X . . . |
$$ | . X . O B W X X X O O O O O X X . . . |
$$ | . . X O . X X O X X O X X X . X . . . |
$$ | . X O . O O O O . X X . X O X . . . . |
$$ | . O . O . . . . a . . X O . X . . . . |
$$ ---------------------------------------[/go]

The top side is miai, so whoever plays first can win with the kosumi at "a".

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

Visualize whirled peas.

Everything with love. Stay safe.

Good morning, Bill.
Off-topic: since post 385, the tengen went from a comma (,) to an underscore (_).

( Nice convention. )

I'm guessing Bill did. that on purpose, to make it clear that this is not one board with a center but two seperate positions.

Right. At least, nobody can say, What about a play on tengen?

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

Visualize whirled peas.

Everything with love. Stay safe.

The Four Immortals game: A corrupted game record

A relay game by four immortals (Taoist immortals, I suppose) is game number 5 in the Carefree and Innocent Pastime Collection(C&IP), played in 1094. The game record is available in the GOGOD database. There are problems with the game record in the C&IP. In "The history of go rules" (2011) Chen Zuyuan notes that the statement that the game was 242 moves long was written in with a brush later. (The book was printed.) It would have been usual to say that each side made 121 moves, and elsewhere it is stated that in this game each side made 125 moves. Chen speculates about all this. But there is another problem with the game record, as the final diagram shows.

Click Here To Show Diagram Code

[go]$$Wcm42 Final diagram
$$ ---------------------------------------
$$ | . O . . . . . . O O . X X . X X X O . |
$$ | X O 1 . X O O O X X X . . X X O O O . |
$$ | X X O O O O X O O O O X X X X X X O . |
$$ | . X X X O . X X O , O O O X X O O . . |
$$ | . . . . X X . X O O . X X X O O . O . |
$$ | . . . . X O O X O X X . X O O X O . . |
$$ | . . X . . X O X X X O X X X X X O O . |
$$ | . . . . . X O O . X O O O O X . X O O |
$$ | . . . . . X O O . O O X . O X . X X O |
$$ | X X . , . X O X O C O X X X . , . . X |
$$ | O X X X . . X X a O X X O O X X O X . |
$$ | O O X O X X O X . O O O X O O O X X X |
$$ | . O O O O X O X O O X X X X O . O O O |
$$ | . . O X O O O X X O X X O O O O O . O |
$$ | . . O X . X . O X O O X X . . X X O O |
$$ | . . . O X X O . O , X . . O O X O X X |
$$ | . . O . O X . O . O O X X X X X O X . |
$$ | . . . . O X . . O X X X . . . . O X . |
$$ | . . . . . . . . O O X . . . . . . . . |
$$ ---------------------------------------[/go]

White 242 was a protective play. Now the book states that White has 9 Black prisoners and has 43 points, and that Black has 7 White prisoners and has 42 points. To get those scores you first make all the protective plays and then fill in the territories with the prisoners, and then subtract the group tax. White has four groups and Black has two, so White's group tax is 8 pts. and Black's group tax is 4 pts. Without the group tax White would win by 5 pts.

So far, so good, except that to get a score of 43 pts. White has to count the tengen point (marked), and White cannot do that without having a White stone at "a". The game is not really over, and, unless the four immortals were very bad players, the game record is corrupted.

Gotta run now, but I will speculate on what went wrong, later.

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

Visualize whirled peas.

Everything with love. Stay safe.

Apparently some people have altered the game record to make it come out in accordance with the score. So maybe I'm re-treading well trodden ground, but I thought that I would give it a try, too.

Click Here To Show Diagram Code

[go]$$Wcm36 Mistakes
$$ ---------------------------------------
$$ | . O . . . . . . O O . X X . X X X O . |
$$ | X O 7 . X O O O X X X . . X X O O O . |
$$ | 6 X O O O O X O O O O X X X X X X O . |
$$ | . X X X O . X X 1 , O O O X X O O . . |
$$ | . . . . X X . X O O . X X X O O . O . |
$$ | . . . . X O O X O X X . X O O X O . . |
$$ | . . X . . X O X X X O X X X X X O O . |
$$ | . . . . . X O O . X O O O O X . X O O |
$$ | . . . . . X O O . O O X . 5 X . X X O |
$$ | X X . , . X O X O , O X X X . , . . X |
$$ | O X X X . . X X a O X X O O X X O X . |
$$ | O O X O X X O X . O O O X O O O X X X |
$$ | . O O O O X O X O O X X X X O . O O O |
$$ | . . O X O O O X X O X X O O O O O . O |
$$ | . . O X . X . O X O O X X . . X X O O |
$$ | . . . O X X O . O , 4 . . O O X O X X |
$$ | . . O . O X . O . O O X X X X X O X . |
$$ | . . . . O X . . O X X X . . . . O X . |
$$ | . . . . . . . . 3 O 2 . . . . . . . . |
$$ ---------------------------------------[/go]

Backing the game up to move 236, we can see that Black 241 and White 242 should be at "a". But they look like a neutral point and a protective play, simple formalities that could easily have ended play. It is certainly plausible that someone had already played at "a" before they were played. But White 236 is an error. It gains only ½ pt., while there is a reverse sente that gains 1 pt., at 237.

Click Here To Show Diagram Code

[go]$$Wcm36 Correct play, but . . . .
$$ ---------------------------------------
$$ | . O . . . . . . O O . X X . X X X O . |
$$ | X O 9 . X O O O X X X . . X X O O O . |
$$ | 8 X O O O O X O O O O X X X X X X O . |
$$ | . X X X O . X X 5 , O O O X X O O . . |
$$ | . . . . X X . X O O . X X X O O . O . |
$$ | . . . . X O O X O X X . X O O X O . . |
$$ | . . X . . X O X X X O X X X X X O O . |
$$ | . . . . . X O O . X O O O O X . X O O |
$$ | . . . . . X O O . O O X . 7 X . X X O |
$$ | X X . , . X O X O , O X X X . , . . X |
$$ | O X X X . . X X 6 O X X O O X X O X . |
$$ | O O X O X X O X . O O O X O O O X X X |
$$ | . O O O O X O X O O X X X X O . O O O |
$$ | . . O X O O O X X O X X O O O O O . O |
$$ | . . O X . X . O X O O X X . . X X O O |
$$ | . . . O X X O . O , 4 . . O O X O X X |
$$ | . . O . O X . O . O O X X X X X O X . |
$$ | . . . . O X . . O X X X . . . . O X . |
$$ | . . . . . . . . 3 O 1 2 . . . . . . . |
$$ ---------------------------------------[/go]

If White plays correctly, then White 238 is the last effective play, since the plays that gain ½ pt. are miai. White and Black each get the same moves as in the game record, but Black also gets Black 241. White wins by 1 pt., but by 42 to 41 instead of 43 to 42. This is a possible reconstruction, but not one that makes a minimal change to the game record.

Click Here To Show Diagram Code

[go]$$Bcm29 Blunder
$$ ---------------------------------------
$$ | . O . . . . . . O O . X X . . 1 . a . |
$$ | X O . . X O O O X X X . . X X O O 2 . |
$$ | . X O O O O X O O O O X X X X X X O . |
$$ | . X X X O . X X . , O O O X X O O . . |
$$ | . . . . X X . X O O . X X X O O . O . |
$$ | . . . . X O O X O X X . X O O X O . . |
$$ | . . X . . X O X X X O X X X X X O O . |
$$ | . . . . . X O O . X O O O O X . X O O |
$$ | . . . . . X O O . O O X . . X . X X O |
$$ | X X . , . X O X O , . . X X . , . . X |
$$ | O X X X . . X X . O X X O O X X O X . |
$$ | O O X O X X O X . O O O X O O O X X X |
$$ | . O O O O X O X O O X X X X O . O O O |
$$ | . . O X O O O X X O X X O O O O O . O |
$$ | . . O X . X . O X O O X X . . X X O O |
$$ | . . . O X X O . O , . . . O O X O X X |
$$ | . . O . O X . O . O O X X X X X O X . |
$$ | . . . . O X . . O X X X . . . . O X . |
$$ | . . . . . . . . . O . . . . . . . . . |
$$ ---------------------------------------[/go]

White 230 is a blunder. Would a Taoist immortal make that mistake? "a" is the obvious move. If we let White make the obvious move, everything falls into place.

Click Here To Show Diagram Code

[go]$$Bcm29 Possible game
$$ ---------------------------------------
$$ | . O . . . . . . O O . X X . . 1 . 2 . |
$$ | X O . . X O O O X X X . . X X O O . . |
$$ | . X O O O O X O O O O X X X X X X O . |
$$ | . X X X O . X X 8 , O O O X X O O . . |
$$ | . . . . X X . X O O . X X X O O . O . |
$$ | . . . . X O O X O X X . X O O X O . . |
$$ | . . X . . X O X X X O X X X X X O O . |
$$ | . . . . . X O O . X O O O O X . X O O |
$$ | . . . . . X O O . O O X . 0 X . X X O |
$$ | X X . , . X O X O , 6 7 X X . , . . X |
$$ | O X X X . . X X 9 O X X O O X X O X . |
$$ | O O X O X X O X . O O O X O O O X X X |
$$ | . O O O O X O X O O X X X X O . O O O |
$$ | . . O X O O O X X O X X O O O O O . O |
$$ | . . O X . X . O X O O X X . . X X O O |
$$ | . . . O X X O . O , 5 . . O O X O X X |
$$ | . . O . O X . O . O O X X X X X O X . |
$$ | . . . . O X . . O X X X . . . . O X . |
$$ | . . . . . . . . 4 O 3 . . . . . . . . |
$$ ---------------------------------------[/go]

After White makes the correct play in the top right corner, , Black 231 is sente. White 232 is the last effective play. The ½ pt. plays are miai, with each player getting the one in the published game record, and Black getting Black 237. After White 238 the rest are dame and protective plays. And this way the scores come out as in the published record.

OC, this is speculative, but it is also parsimonious, making minimal changes to the published record.

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

Visualize whirled peas.

Everything with love. Stay safe.

Bill, I cannot find quickly any positions of yours with the following aspects. Do you recall them or where to find them?

1) A basic endgame ko, some local non-ko not-only-dame endgames, possibly a few dames. There is no first move that is correct under area and territory scoring. I am not sure whether you found such positions. If not, maybe you can construct some?

2) Ca. 15 or 20 years ago, you found a position with different behaviour under area and territory scoring having only innocently looking shapes without any of the well-known exceptions related to sekis, kos or dames.

That may be something I posted on rec.games.go but found a flaw in a couple of years later. But it led to finding the button position, which has an average value of 1/2 by area scoring, and ought to have a score of 1/2 by territory scoring, but territory scores are integers. I believe that the button is on SL.



That sounds like something that I found in discussion with Bernd Gramlich, again on rec.games.go.

So far, I have not identified anything in my records. I'll keep looking.

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

Visualize whirled peas.

Everything with love. Stay safe.

Cher Robert,

OC, there is the first problem in this thread.

See https://lifein19x19.com/forum/viewtopic ... 89#p194089

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

Visualize whirled peas.

Everything with love. Stay safe.

I did not mention it because territory scoring also allows the move that is correct under area scoring.

***

Let's hope Bernd Gramlich used lesfables then and not " " or "-" as his account name...

Oh, I missed that. 0.75 - 0.5 = 0.5 - 0.75 + 0.5.

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

Visualize whirled peas.

Everything with love. Stay safe.

How not to teach the last play

Volume 5 in Sakata's classic Killer of Go series is The Tsume and Yose of Go. It combines tsumego with yose, a traditional practice of which I approve. The book devotes one page (three diagrams) to the question of the last play. Here is the basic diagram.

Click Here To Show Diagram Code

[go]$$Bc Black to play, the rest of the board is jigo
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . X O . . . . . . . O O |
$$ | . X . . . . X . X O O O O X . . . O X |
$$ | X X X X X X O X O X O X O O O O O X X |
$$ | O X O O O X O X . X O X X . X O . . X |
$$ | O X O X X X O X X X O O O O X O O O X |
$$ | O O O O O O O O O O X X X X X X X X X |
$$ | . . . . . . . . . . . . . . . . . . . |[/go]

Here, in brief, is what the book says. (The book was very probably ghost written, but Sakata signed off on it.)

Click Here To Show Diagram Code

[go]$$Bc Diagram 1 Black gets the last play
$$ ---------------------------------------
$$ | . . . . . . . . 3 1 2 . . . . . . . . |
$$ | . . . . . . . . X O . . . . . . . O O |
$$ | . X . . . . X . X O O O O X . . . O X |
$$ | X X X X X X O X O X O X O O O O O X X |
$$ | O X O O O X O X . X O X X 4 X O . 5 X |
$$ | O X O X X X O X X X O O O O X O O O X |
$$ | O O O O O O O O O O X X X X X X X X X |
$$ | . . . . . . . . . . . . . . . . . . . |[/go]

is the last play. White wins by 1 pt.

Click Here To Show Diagram Code

[go]$$Bc Diagram 2 White gets the last play
$$ ---------------------------------------
$$ | . . . . . . . 3 2 4 . . . . . . . . . |
$$ | . . . . . . . 5 X O . . . . . . . O O |
$$ | . X . . . . X . X O O O O X . . . O X |
$$ | X X X X X X O X O X O X O O O O O X X |
$$ | O X O O O X O X . X O X X 1 X O . 6 X |
$$ | O X O X X X O X X X O O O O X O O O X |
$$ | O O O O O O O O O O X X X X X X X X X |
$$ | . . . . . . . . . . . . . . . . . . . |[/go]

is the last play. Black wins by 1 pt.

Conclusion: Trying too hard to get the last play can be dangerous.

That's it! Nothing about the value of getting the last play, nothing about how to get it. Just a note of caution.

----

Well, today we know a good bit more about getting the last play. Berlekamp and Wolfe's Mathematical Go teaches us that, unless ko is a consideration, we can ignore plays that gain less than 1 pt. in considering the last play. That eliminates in Diagram 1 and in Diagram 2, each of which gains only ½ pt. The question of getting the last play, if it arises at all, is concerned with getting the last play at temperature 1 or higher. In this case it is White who gets the last play at temperature 3 in diagram 1 and Black who gets the last play at temperature 3 in diagram 2. So getting the last play matters in this case. You just have to understand the concept properly.

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

Visualize whirled peas.

Everything with love. Stay safe.

Kano teaches about getting the last play

Kano does much better than Sakata. But Kano's Yose Dictionary is over 40 years old. The modern knowledge about getting the last play was yet to come. Kano discusses two positions, not just one. (Three examples if you count the miai example. ) Also, the positions have temperature 1, which is the place to start the study of getting the last play.

Click Here To Show Diagram Code

[go]$$Bc Black to play and get the last play
$$ --------------------
$$ | . . . . . . . . . .
$$ | . X . . . X X O . .
$$ | . X . X . X O . O .
$$ | . O X , X X O . . ,
$$ | . O . O O O O . . .
$$ | . O . . . . . . . .
$$ | . . . . . . . . . .[/go]

By the standard assumption, the surrounding territory belongs to White. There are three places to play, two hane-and-connects and the place around D-16. The hane-and-connects are miai, so this should be easy.

Click Here To Show Diagram Code

[go]$$Bc Black gets the last play
$$ --------------------
$$ | . . . . . 5 4 6 . .
$$ | . X . . . X X O . .
$$ | 9 X . X . X O . O .
$$ | 7 O X 3 X X O . . ,
$$ | 8 O 1 O O O O . . .
$$ | . O 2 . . . . . . .
$$ | . . . . . . . . . .[/go]

is sente, and then takes the reverse sente. After that, the rest is miai, as advertised.

But here is Kano's first play diagram.

Click Here To Show Diagram Code

[go]$$Bc Failure
$$ --------------------
$$ | . . . . . 9 8 0 . .
$$ | . X . . . X X O . .
$$ | 5 X 7 X . X O . O .
$$ | 3 O X 6 X X O . . ,
$$ | 4 O 1 O O O O . . .
$$ | . O 2 . . . . . . .
$$ | . . . . . . . . . .[/go]

Good. White punishes Black's failure to play the reverse sente at 6. However, Kano does not blame .

Click Here To Show Diagram Code

[go]$$Bc Black gets the last play (Kano)
$$ --------------------
$$ | . . . . . . 3 1 2 .
$$ | 5 X . . . X X O . .
$$ | 4 X . X . X O . O .
$$ | 6 O X 9 X X O . . ,
$$ | . O 7 O O O O . . .
$$ | . O 8 . . . . . . .
$$ | . . . . . . . . . .[/go]

is not a mistake, but what about ? It does not provide the stoutest resistance.

Click Here To Show Diagram Code

[go]$$Bc Stiffer resistance
$$ --------------------
$$ | . . . . . . 3 1 2 .
$$ | . X . . . X X O . .
$$ | 7 X 9 X . X O . O .
$$ | 5 O X 8 X X O . . ,
$$ | 6 O 4 O O O O . . .
$$ | . O . . . . . . . .
$$ | . . . . . . . . . .[/go]

It makes no difference in this case, but is technically correct, as a play at 8 would be. gives Black the chance to err by playing at 8.

It is hard to fault Kano, given the state of knowledge in the early 1970s, but we know more now about getting the last play.

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

Visualize whirled peas.

Everything with love. Stay safe.

Kano's beauty

Kano's final position for getting the last play is a thing of beauty.

Click Here To Show Diagram Code

[go]$$Wc Kano's beauty
$$ ----------------------
$$ | . . . . . . . . . . .
$$ | . . . . . . X X O . .
$$ | . X . X . . X O . O .
$$ | O X O X . X X O . , .
$$ | X X X X . O X O . . .
$$ | O X O . X O X O . . .
$$ | O X . . X O X O . . .
$$ | O O O O O . O . . . .
$$ | . . . . . . . . . . .
$$ | . . . , . . . . . , .[/go]

Kano's book may have been ghost written, but I believe that this position is Kano's invention. It combines a bread and butter hane-and-connect on the top side with a somewhat complicated position around E-15. As usual, we assume that the surrounding territory belongs to White. Kano has White to play.

Click Here To Show Diagram Code

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

, saving the stone, is a mistake. Black plays the sente, , and then takes the hane-and-connect on the top side to get the last play.

Click Here To Show Diagram Code

[go]$$Wc White gets the last play
$$ ----------------------
$$ | . . . . . . 8 7 9 . .
$$ | . . . . . . X X O . .
$$ | . X . X . . X O . O .
$$ | O X O X 2 X X O . , .
$$ | X X X X 1 O X O . . .
$$ | O X W 6 B O X O . . .
$$ | O X 4 5 B O X O . . .
$$ | O O O O O 3 O . . . .
$$ | . . . . . . . . . . .
$$ | . . . , . . . . . , .[/go]

- is correct, threatening the stones, Black saves them and captures the stone with reverse sente. Then White takes the hane-and-connect and gets the last play.

In this combination White can get the last play, regardless of who plays first.

Click Here To Show Diagram Code

[go]$$Bc Black sente
$$ ----------------------
$$ | . . . . . . . . . . .
$$ | . . . . . . X X O . .
$$ | . X . X . . X O . O .
$$ | O X O X . X X O . , .
$$ | X X X X 1 O X O . . .
$$ | O X W . X O X O . . .
$$ | O X . . X O X O . . .
$$ | O O O O O 2 O . . . .
$$ | . . . . . . . . . . .
$$ | . . . , . . . . . , .[/go]

Black has the obvious sente, leaving the hane-and-connect and the region around miai. At first blush, then, this position is a Black sente. However, . . .

Click Here To Show Diagram Code

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

After - White can simply leave the hane-and-connect unplayed. (Not when there is nothing else left on the board, OC. ) White's play is ambiguous between sente and reverse sente. This is a kind of ambiguity of which I was unaware.

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

Visualize whirled peas.

Everything with love. Stay safe.

Isn't the E15 area simply a double sente here? (with the complete sequences)