Re: [gnugo-devel] look at regress file 13x13b:4

[kevin yong]

Hi, Gunnar:

  i did some work on case 13x13b:4, as you suggested,
and found the following:

  1. how/why F11 was choosen:
  at the final report, it says:
    Top moves:
    1. F11 35.01
    2. F10 3.04
    3. K1  2.1
  we can see F11 has a huge points lead over F10.
  Where this big points come from:
    pattern 'ED66'+5 matched at F11
    ...joseki standard move
    ...expands territory
    ...expands moyo
    F11:   35.00 - set_minimum_move_value
  
  and the calling sequence is:
    do_genmove()
      shapes()
        matchpat(shapes_callback, color, &pat_db,
          NULL, NULL); 
          shapes_callback() {
            /* Pattern class J, joseki standard move.
             * Add expand territory and
             * moyo, and require the value at least
             * J_value.
            */
            if (class & CLASS_J) {
              TRACE("...joseki standard move\n");
              add_expand_territory_move(move);
              TRACE("...expands territory\n");
              add_expand_moyo_move(move);
              TRACE("...expands moyo 1\n");
              set_minimum_move_value(move, J_VALUE);
              TRACE("... minimum move value %f\n",
                J_VALUE);
            }

So, problem is: in general, pattern match is
local/small, it is mis-used in a big environment.
Specifically in the case of 13x13b:4, it is currently
at endgame stage now. This Joseki pattern to
expand-territory and moyo should only applicable at
start-middlge stages of a game, provided that there is
enough room to expand. This Joseki pattern match over
looked the later.

Suggested solution: there are several options
available (at least):
1. 
- before shapes() analysis called, insert another
step, let’s temporary named it ‘stage_judgement()’,
which will give a general judgement it’s at
open/middle/end game stage;
- inside shapes(), after a expand territory/moyo
pattern found, should also look at what stage of game
we are, then decide if the pattern is applicable or
not.
2.
- inside shapes(),after a expand territory/moyo
pattern found, add a step to check if there is enough
room to expand before add big points for this pattern.

best regards.
kevin.






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