I have seen games where programs do not seem to read n-liberty semeais 
properly; 
the opponent or the program may take away liberties until the status flips from 
"alive with proper play" to "dead" -- thereby snatching defeat from the jaws of 
victory.
 Terry McIntyre <[email protected]>


Unix/Linux Systems Administration
Taking time to do it right saves having to do it twice.




________________________________
From: Petr Baudis <[email protected]>
To: Aja <[email protected]>; [email protected]
Sent: Fri, December 3, 2010 7:23:19 AM
Subject: Re: [Computer-go] Tactical misevaluations in Fuego MCTS

On Fri, Dec 03, 2010 at 06:51:55PM +0800, Aja wrote:
> The top right corner can be correctly handled by the 2-point semeai
> feature in the playout, which is described in our simulation
> balancing paper.

Can it? Pachi also has 2-point semeai solver, which can solve the
situation well if the *opponent* reduced the group to two liberties;
it seems your feature has the similar properties.

However, here what happens in high portion of playouts in Pachi is that
white self-reduces the group to 2 liberties:

          A B C D E F G H J K L M N O P Q R S T
        +---------------------------------------+
     19 | O X X X . . O . . . X O O). . X . . O |
     18 | . O O X . O . O X . . X O O O O X O . |
     17 | O . O X . O O X X . X . X X X O X . . |
     16 | O . O X . . . O X . . . . . X X O O . |

Then the 2-point semeai solver happily kicks in for black and the group
is doomed.

I'd be curious how this is prevented in Erica?


There was also another problem with the naive 2-point semeai solver in
Pachi, causing it to take off its liberty more bluntly:

          A B C D E F G H J K L M N O P Q R S T
        +---------------------------------------+
     19 | O X X X . . O . . . . . O). X X . . O |
     18 | . O O X . O . O X . . X O O O O X O . |
     17 | O . O X . O O X X . X . X X X O X . . |
     16 | O . O X . . . O X . . . . . X X O O . |

"Escape" (N19) and counter-capture S17 had equal standing. I'm fixing
that now, thanks. :-)

-- 
                Petr "Pasky" Baudis
The true meaning of life is to plant a tree under whose shade
you will never sit.
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