Re: [gnugo-devel] General impression of 3.3.18

[pogonyshev]

SP LEE wrote: 
> I just played a game with GNUGO 3.3.18 and found it's more aggressive and 
> better in combination attacks. There is only one obvious error on the move

> 62 regarding life and death. Black should obviously play J2 to ensure eye 
> spaces. After white played J2, the black group is dead. I think this is 
> similar to my last game, the cutting point could be vital to the group. 
 
Gunnar and Arend revised the semeai code on the way to 3.3.18 significantly 
and that must be (one of) the reasons why 3.3.18 is stronger. it must be 
especially noticeable in games against strong players (i.e. those who can 
give it nine stones and win ;) since such games typically feature lots of 
semeais. 
 
the life and death problem at J2 is not actually related to eyespaces with 
cutting points. gnugo has two problems reading it: currently, it doesn't 
know that if a dragon is cut in process of defending and both parts have 
one eye each, then the dragon is dead (we can't come up with a way to 
determine if a dragon is still connected without slowing the engine a lot). 
the second problem is about "getting deep, looks lively" life & death 
reading result - it is often fired up in completely inappropriate positions.

 
you can check what gnugo actually thinks of a position using gtp mode. i 
used the following commands here: 
 
    # -l specifies .sgf file to load, -L says till which move to load 
  $ interface/gnugo --mode gtp --quiet -t -l ../12.sgf -L 63 
    # from now the commands go directly to gnugo 
  start_sgftrace 
  owl_does_attack J2 L2 
  finish_sgftrace ../bug.sgf 
  quit 
 
the responses looked like this (`=' means that command succeeded): 
 
  start_sgftrace 
  = 
 
  owl_does_attack J2 L2 
  [ here go tons of debug output, it was turned on with -t option ] 
  = 0 
 
  finish_sgftrace ../bug.sgf 
  = 
 
  quit 
  = 
 
= 0 means that gnugo thinks that J2 is not an effective attack against L2 
dragon. 
 
now you can use your favourite sgf editor (cgoban or jago or whatever else) 
to open bug.sgf and see the actual reading tree of gnugo. 
 
some other often used gtp commands include: 
  life and death reading: 
    owl_attack <vertex> - try to attack the dragon at <vertex> 
    owl_defend <vertex> - try to defend the dragon at <vertex> 
    owl_does_attack <vertex1> <vertex2> - 
        determine if move at <vertex1> attacks the dragon at <vertex2> 
    owl_does_defend <vertex1> <vertex2> - 
        determine if move at <vertex1> defends the dragon at <vertex2> 
    owl_analyze_semeai <vertex1> <vertex2> - 
        analyze semeai between two dragons 
 
  tactical reading: 
    attack <vertex> - try to attack the string at <vertex> 
    defend <vertex> - try to defend the string at <vertex> 
 
  connection reading: 
    connect <vertex1> <vertex2> - try to connect two strings 
    disconnect <vertex1> <vertex2> - try to disconnect two strings 
 
  global position analysis: 
    gg_genmove (white|black) - generate supposedly best move for white or
black 
 
to find the complete list with descriptions look in interface/play_gtp.c
file. 
 
Paul 

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