Re: computer-go: Computer Go Tournament Program

[Don Dailey <drd@xxxxxxxxxxxxxxxxxxxxx>]

   Date: Mon, 02 Jul 2001 23:00:22 +0200
   From: Gunnar Farnebäck <gunnar@xxxxxxxxxxxxxxxxx>

   Don Dailey wrote:
   > This  sounds great but  how about   adding  a Tromp-Taylor  setting in
   > gnu-go?  I have  considered patching this in myself  but would it  get
   > incorportated into the distribution if I went to the trouble? 

   As it happens this can also be expected in the next version, since I
   already have an implementation ready.

Awesome!  

   But I have no idea why people seem to think that it should be easy to
   generate moves which effectively remove all opponent dead
   stones.  ...

I'm not one of those people.  I know it's not trivial and in fact I don't
think it's currently possible to do it right every time.

   ... Sure, many times it's just to play on their liberties in some
   arbitrary order, but when there are big nakades around quite a bit of
   care is needed. Also, a serious implementation should be able to
   remove bent-four-in-the-corner shapes. These are not too hard to
   statically identify as dead (or more exactly effectively worth one
   eye) by eye shape pattern matching, but in order to actually remove
   them from the board you must first eliminate all ko threats. The only
   way I know of robustly doing this is to first play other moves which
   make all (other) own living stones unconditionally (in the strongest
   sense) alive and all (other) dead opponent stones unconditionally dead.

   So this is what GNU Go does, or at least tries to do. There will be
   two new options, --play_out_aftermath which forces the engine to play
   on until as much as possible is unconditionally settled, and
   --remove_all_dead_stones which plays on until all dead opponent stones
   are gone. For the reasons explained above, the latter option
   effectively includes the former.

   > By  the way,  I do a  lot  of autotesting  between  versions of my own
   > program  using TT  rules and  it's simple   and elegant.   I also have
   > tested against   older versions  of gnugo  (There  is  little point in
   > testing  newer versions since I  only win about 25%  of the games with
   > 2.6 version)  and had to go  to a lot of  trouble  to design a scoring
   > module that works  with gnu-go's habit of  ending the game whenever it
   > feels like it.

   Recent versions of GNU Go are reasonably good at (Japanese style)
   scoring. I have tested the "--score aftermath" option, or more exactly
   the GTP equivalent final_score, on Dave Dyer's test set of 623 scored
   professional games. The latest results are

   66% correct score
   89% off by at most one point
   97% off by at most three points
   99% off by at most ten points

   Most of the misscorings are due to mistakes in the late endgame when
   dame is being filled.

   /Gunnar