Re[2]: computer-go: Defeating mirror Go

[Roland <goprog@xxxxxxx>]

Hello Michael,

Thursday, September 28, 2000, 10:47:45 AM, you wrote:


MCac> Don't all of these fall over?
MCac> Doesn't any board position starting with an unconditionally alive group
MCac> defeat mirror go?

No, because it's the player who mirrors that has the alive group,
which should be placed at the mirror point/axis. The purpose of this
group is to prevent the opponent from doing the following you just
mentioned:

MCac> To defeat any type of mirror go ( at least to defeat the mirror part as
MCac> opposed to winning the game ) all you need to do is play on a point of
MCac> reflection/rotation/both.

The living group prevents this, so the opponent can't frustrate the
mirror by this elementary way.


MCac> ( However, if there were an even number of rows/columns... )

you can frustrate the mirror also, look at this example on a 18x18
board. Black(#) starts playing and white only mirrors him; blacks next
move will kill the white center group:

     A B C D E F G H J K L M N O P Q R S
  18 . . . . . . . # O # O . . . . . . . 18
  17 . . . . . . . # O # O . . . . . . . 17
  16 . . . . . . . # O # O . . . . . . . 16
  15 . . . . . . . # O # O . . . . . . . 15
  14 . . . . . . . # O # O . . . . . . . 14
  13 . . . . . . . # O # O . . . . . . . 13
  12 . . . . . . . # O # O . . . . . . . 12
  11 . . . . . . . # O # O . . . . . . . 11
  10 . . . . . . . # O # O . . . . . . . 10
   9 . . . . . . . # O # O . . . . . . .  9
   8 . . . . . . . # O # O . . . . . . .  8
   7 . . . . . . . # O # O . . . . . . .  7
   6 . . . . . . . # O # O . . . . . . .  6
   5 . . . . . . . # O # O . . . . . . .  5
   4 . . . . . . . # O # O . . . . . . .  4
   3 . . . . . . . # O # O . . . . . . .  3
   2 . . . . . . . # O # O . . . . . . .  2
   1 . . . . . . . . O # . . . . . . . .  1
     A B C D E F G H J K L M N O P Q R S

The same idea for mirroring through the center point: The player who
plays first will be the first one to surround and kill the other
group. Black to move:
     

     A B C D E F G H J K L M N O P Q R S
  18 . . . . . . . . . . . . . . . . . . 18
  17 . . . . . . . . . . . . . . . . . . 17
  16 . . . . . . . . . . . . . . . . . . 16
  15 . . . . . . . . . . . . . . . . . . 15
  14 . . . . . . . . . . . . . . . . . . 14
  13 . . . . . . . . . . . . . . . . . . 13
  12 . . . . . . . . . . . . . . . . . . 12
  11 . . . . . . . . # . . . . . . . . . 11
  10 . . . . . . . # O # O . . . . . . . 10
   9 . . . . . . . # O # O . . . . . . .  9
   8 . . . . . . . . . O . . . . . . . .  8
   7 . . . . . . . . . . . . . . . . . .  7
   6 . . . . . . . . . . . . . . . . . .  6
   5 . . . . . . . . . . . . . . . . . .  5
   4 . . . . . . . . . . . . . . . . . .  4
   3 . . . . . . . . . . . . . . . . . .  3
   2 . . . . . . . . . . . . . . . . . .  2
   1 . . . . . . . . . . . . . . . . . .  1
     A B C D E F G H J K L M N O P Q R S



-- 
Best regards,
 Roland