Re: [gnugo-devel] 3x3 point never played

[Alain Baeckeroot]

Le Jeudi 13 Janvier 2005 03:45, Gunnar Farnebäck a écrit :
> Alain wrote:
> > On a 9x9, gnugo 3.6 against himself
> > The 3x3 point is not played until the end game,
> 
> That is certainly too late. It seems more appropriate to do it at move
> 10, or maybe move 8. Relevant code is around line 355 of fuseki.c:

I tried differents things on that file:
- play the sansan at move 10 and let gnugo 3.6 finish the game....
with various params (size cache, --large-scale, owl depth semeai depth)
Here are my first conclusions (i can give you more details , and sgf files)

- I (6kyu) thinks black make a global mistake by choosing that joseki:
 W can destroy B startegy by playing sans san in 8 or 10, and win the game.
 
- With default params, gnugo 3.6  live in the corner and win, so W should have
  played that for win.
- default + large-scale, gnugo 3.6 is dead in the corner, so W is right not 
having played.
- with compile options: 
 CFLAGS="-march=athlon-xp" 
 ./configure --enable-cache-size=512 
  --enable-experimental-semeai --enable-semeai-node-limit=8000
  --enable-owl-threats --enable-owl-node-limit=16000 
  --enable-large-scale --enable-experimental-reading
 then gnugo W is alive, and win should have win the game.
> 
>   /* On 9x9, only play open corners after the first move if nothing
>    * else useful is found.
>    */
>   if (board_size == 9 && stones_on_board(color) > 0)
>     empty_corner_value = 5;
> 
> I remember that it was necessary to be careful not to just blindly
> occupy corners on 9x9, but this seems way conservative. Maybe an empty
> corner value of say 12 or 15 would be more appropriate.

I like the lot of idea gnugo has, and i m afraid that rising the value
will kill this "imagination".

I thinks if the defensive engine get stronger, gnugo will be able to read
that it can live there, and so will play it for victory :)


> 
> > and then is considered as dead, whereas it can live !!!
> 
> Well, lets say that I have no difficulty seeing how GNU Go might go
> wrong in reading this. With such a strong position black has all sorts
> of nasty moves available which could normally quickly be ruled out.
> Try "gnugo -l SanSan-is-Alive.sgf -L 26 --decide-owl G3 -o vars.sgf"
> to see what moves were actually considered.
;)

Well , humm, sansan might be alive if played early, and is probably dead
in the end game.

There are still hallucination from gnugo in the end game, when white play
negative move (-2 or -3).
This is due to difference of strengh of the attack module and the defense.
The attacker thinks it can do something, but once the move is played
and B has answered, the life of the group is in the hand of the defense module.

As they are not identical, the defense module has to defend a W group and
doens't know how to do it so the group is considered dead, so it dies of
oldness, and will not go to Valhalla ;)

(i have other sgf file to explain that clearly, i prepare an other
mail with all that clearly exposed)

Alain

sansan-retry-3.6.sgf
Description: Text document

sansan-retry-large-scale.sgf
Description: Text document

sansan-retry-large-scale-3.6.sgf
Description: Text document

sansan-retry.sgf
Description: Text document