What does this move do?

emeraldemon · Post by **emeraldemon** » Sat Jul 19, 2014 2:29 pm

I was looking at this pro game:

White wins by half a point. The last few moves are as follows:

Click Here To Show Diagram Code: [go]$$Wcm1 Moves 226 to 235 $$ --------------------------------------- $$ | . . . . . . . . . . . . O X X X X X . | $$ | . . . . . . . O O . . O O O O O O X . | $$ | O . O . O O O X O X O O X X O O X X . | $$ | X O . O X X X X X O O X . X O X X . X | $$ | X O O X . 8 7 O X X X X X X X O X X O | $$ | X O X X . . X O O O X O O . X O X X O | $$ | X X X . . . X X O . X O O X X O X O O | $$ | X O O X . . X O O O O 9 . O O O O . O | $$ | O . O X . X X X O O X O . . O O O . O | $$ | . . O X . . X O O X X X O . . , . O . | $$ | . . O X . X X X O 5 6 O 3 O O . . . . | $$ | . . O O X . O O X X X O 2 X O . . O . | $$ | . O X X X X O X . . . X . X O O . . O | $$ | . O X X X O X . X . . . X O X X O O 1 | $$ | . O O X O O X X . . . . . 4 X O X X O | $$ | . . O O O O O X . , . . . . . , X . X | $$ | . . X X O X X . . . . . . X . X . . . | $$ | . . . O . O X X X . . . . . . . . . . | $$ | . . . . O O O O X . . . . . . . . . . | $$ ---------------------------------------[/go]

My question is, why didn't black play

at

? Why does black have to protect?

Click Here To Show Diagram Code: [go]$$Wcm1 Block and win the game? $$ --------------------------------------- $$ | . . . . . . . . . . . . O X X X X X . | $$ | . . . . . . . O O . . O O O O O O X . | $$ | O . O . O O O X O X O O X X O O X X . | $$ | X O . O X X X X X O O X . X O X X . X | $$ | X O O X . . 2 O X X X X X X X O X X O | $$ | X O X X . . X O O O X O O . X O X X O | $$ | X X X . . . X X O . X O O X X O X O O | $$ | X O O X . . X O O O O . . O O O O . O | $$ | O . O X . X X X O O X O . . O O O . O | $$ | . . O X . . X O O X X X O . . , . O . | $$ | . . O X . X X X O . . O . O O . . . . | $$ | . . O O X . O O X X X O . X O . . O . | $$ | . O X X X X O X . . . X . X O O . . O | $$ | . O X X X O X . X . . . X O X X O O 1 | $$ | . O O X O O X X . . . . . . X O X X O | $$ | . . O O O O O X . , . . . . . , X . X | $$ | . . X X O X X . . . . . . X . X . . . | $$ | . . . O . O X X X . . . . . . . . . . | $$ | . . . . O O O O X . . . . . . . . . . | $$ ---------------------------------------[/go]

I can only assume there's some problem around N7 that keeps black from getting the last point and winning the game, but I can't find anything:

Click Here To Show Diagram Code: [go]$$Wcm1 :b8: at :w5: $$ --------------------------------------- $$ | . . . . . . . . . . . . O X X X X X . | $$ | . . . . . . . O O . . O O O O O O X . | $$ | O . O . O O O X O X O O X X O O X X . | $$ | X O . O X X X X X O O X . X O X X . X | $$ | X O O X . . 2 O X X X X X X X O X X O | $$ | X O X X . . X O O O X O O . X O X X O | $$ | X X X . . . X X O . X O O X X O X O O | $$ | X O O X . . X O O O O . . O O O O . O | $$ | O . O X . X X X O O X O . . O O O . O | $$ | . . O X . . X O O X X X O . . , . O . | $$ | . . O X . X X X O . . O 7 O O . . . . | $$ | . . O O X . O O X X X O 6 X O . . O . | $$ | . O X X X X O X . . 9 X 5 X O O . . O | $$ | . O X X X O X . X . 0 . X O X X O O 1 | $$ | . O O X O O X X . . . . . 3 X O X X O | $$ | . . O O O O O X . , . . . . 4 , X . X | $$ | . . X X O X X . . . . . . X . X . . . | $$ | . . . O . O X X X . . . . . . . . . . | $$ | . . . . O O O O X . . . . . . . . . . | $$ ---------------------------------------[/go]

Is there some shortage of liberties or something that I'm not seeing?

leichtloeslich · Post by **leichtloeslich** » Sat Jul 19, 2014 3:23 pm

If this was played under Japanese rules I'd assume it's simply an error in (moveorder) transcription, since under territory scoring it makes very little sense for white to fill at t6 before pushing at g15.

Under area scoring it may make no difference because filling in a liberty by pushing could mean white gets one less dame to fill.

Mikebass14 · Post by **Mikebass14** » Sat Jul 19, 2014 4:26 pm

If white plays 3 at 5 in your last diagram, isn't that also a 1 point sente move, worth the same as 7 in the game?

emeraldemon · Post by **emeraldemon** » Sun Jul 20, 2014 9:44 am

No, I don't think so. If white ataris black can just connect:

Click Here To Show Diagram Code: [go]$$Wcm1 Block and win the game? $$ --------------------------------------- $$ | . . . . . . . . . . . . O X X X X X . | $$ | . . . . . . . O O . . O O O O O O X . | $$ | O . O . O O O X O X O O X X O O X X . | $$ | X O . O X X X X X O O X . X O X X . X | $$ | X O O X . . 2 O X X X X X X X O X X O | $$ | X O X X . . X O O O X O O . X O X X O | $$ | X X X . . . X X O . X O O X X O X O O | $$ | X O O X . . X O O O O . . O O O O . O | $$ | O . O X . X X X O O X O . . O O O . O | $$ | . . O X . . X O O X X X O . . , . O . | $$ | . . O X . X X X O . . O . O O . . . . | $$ | . . O O X . O O X X X O 3 X O . . O . | $$ | . O X X X X O X . . . X 4 X O O . . O | $$ | . O X X X O X . X . . . X O X X O O 1 | $$ | . O O X O O X X . . . . . . X O X X O | $$ | . . O O O O O X . , . . . . . , X . X | $$ | . . X X O X X . . . . . . X . X . . . | $$ | . . . O . O X X X . . . . . . . . . . | $$ | . . . . O O O O X . . . . . . . . . . | $$ ---------------------------------------[/go]

black gets one point from not having to capture. In the game black gets an extra point, but loses a point having to capture the white stone.

emeraldemon · Post by **emeraldemon** » Sun Jul 20, 2014 4:33 pm

leichtloeslich wrote:If this was played under Japanese rules I'd assume it's simply an error in (moveorder) transcription, since under territory scoring it makes very little sense for white to fill at t6 before pushing at g15.

Under area scoring it may make no difference because filling in a liberty by pushing could mean white gets one less dame to fill.

I think this must be it, an error in move order. White could presumably have made that push at any time, maybe the person recording just didn't notice when it happened and put it at the very end. It's annoying though, because I was specifically interested in finding a game with a close endgame to study...

ez4u · Post by **ez4u** » Mon Jul 21, 2014 1:23 am

emeraldemon wrote:
leichtloeslich wrote:If this was played under Japanese rules I'd assume it's simply an error in (moveorder) transcription, since under territory scoring it makes very little sense for white to fill at t6 before pushing at g15.

Under area scoring it may make no difference because filling in a liberty by pushing could mean white gets one less dame to fill.
I think this must be it, an error in move order. White could presumably have made that push at any time, maybe the person recording just didn't notice when it happened and put it at the very end. It's annoying though, because I was specifically interested in finding a game with a close endgame to study...

Well, you've just studied it quite thoroughly. Be happy!

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