Blunder : a bamboo joint is cut and lose the game.

[alain]

gnugo 3.7.8 and 3.7.9 play the same terrible move 26 and let the bamboo joint being cut. This lose the game.

• gnugo 3.7.7 connects.
• Default fourlib-depth is 7. Increasing it to 8 is enough for finding the good move (for 3.7.8 and 3.7.9).

  $ gnugo-3.7.7-ref -l twogtp047.sgf -L 26
  white (O) move E5
  
  $ gnugo-3.7.9-ref -l twogtp047.sgf -L 26
  white (O) move J6
  
  $ gnugo-3.7.9-ref  --fourlib-depth 8 -l twogtp047.sgf -L 26
  white (O) move E5
  
  

[alain]

The twin #104 changes the move and pass the test. This also mean that the connection has no move reason SEMEAI, STRATEGIC_ATTAC or STRATEGIC_DEFEND, as in those case the twin warns and is not used.

[alain]

Some (weird) investigations :

• fourlib depth = 0 or 1 => C8 no.
• fourlib depth = 2, 3, 4, 5, 6 => E5 good
• fourlib depth = 7 => J6 no.
• fourlib depth = 8, 9, 10, 11 => E5 good

[alain]

reverting 2270 and 2254 does fix this, but also lose their benefit, so it is probably not a good idead ;-)

[josephpiche]

I confirm that in current CVS (as of today), this is still an issue. However:

$ interface/gnugo -l twogtp047.sgf -L 26 white (O) move J6

$ interface/gnugo -l twogtp047.sgf -L 26 --fourlib-depth 8 white (O) move E5

$ interface/gnugo -l twogtp047.sgf -L 26 --monte-carlo white (O) move E5

The MC carlo code finds E5. Maybe it should be enabled by default on 9x9 and smaller.