Re: [gnugo-devel] regress gunnar:8

[kevin yong]

Hi, Evan:

  i had a quick look at regress case gunnar:17.

  Problem: T6 wrong, S7 right.

  I went through log file and source code, and found:

It seems that: at ussual analysis (after
exam_positions and move_reasons) process, it dismissed
T6 and choose S8 (better S7? That’s another story). 

  Top moves:
  1. S8  3.91
  .. .. ..
  Checking safety of a white move at S8
  Move generation likes S8 with value 3.91

But gnugo went on and T6 was raised again at  endgame
analysis stage:

Endgame pattern matcher is looking for move reasons
for white!
pattern 'EE302'+3 matched at T6
zzz: add_move_reason, T6 PASS 20 
...expands territory
...(min) territorial value 2.00
...reverse followup value 5.00
  T6: 9.90 - change in territory
  T6:   0.00 - total followup value, added 0.00 as
territorial followup
  T6: 2.50 - added due to followup (0.00) and reverse
followup values (5.00)
  T6:   12.40 0.00 - minimum accepted value
Move generation values T6 to 12.40
.. .. ..

I think there are 2 issues here:
1. endgame pattern match found T6 by pattern EE302, is
it right or wrong? I m not sure;
2. Then it directly go to review_move_reason() process
without a examming/reading process, and got a high
value and been choosen. Should moves found by endgame
pattern match also go through a more detailed
exam/reading process? I m not sure.

>From genmove.c:

  /* If the move value is 6 or lower, we look for
endgame patterns too. */
  if (val <= 6.0 && !disable_endgame_patterns &&
!limit_search) {
    endgame_shapes(color);
    endgame(color);
    gg_assert(stackp == 0);
    if (review_move_reasons(move, &val, color,
pure_threat_value, score,
                            allowed_moves))
      TRACE("Move generation likes %1m with value
%f\n", *move, val);
    gg_assert(stackp == 0);
    time_report(1, "endgame", NO_MOVE, 1.0);
  }

In summary, I found some info about the problem, but I
cant exactly pinpoint the problem and solution. So, I
pass these info for you reference. Like to hear your
comments.

Kevin.





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