Re: [gnugo-devel] arend_1_24.5: dfa 1D conversion

[Trevor Morris]

At 12:07 AM 2/3/2002 +0100, Arend Bayer wrote:
>It seems to me that one could save maybe 1 or 2 % by some 50 lines of code
>with a specialized "count_approxlib" function, as approxlib is mainly called
>from order_moves in reading.c, where the location of the liberties is
>not used.

I'd already started on something like this for accurate_approxlib,
and it was easy to generalize it.  Initial testing on it give about
a 6% improvement on reading.tst.

I'll try to get a patch together tomorrow, but here's the main part:

/* Count the liberties a stone of the given color would get if played
 * at (pos).  Captures are ignored based on the ignore_capture flag.
 * (pos) must be empty.  It will fail if there is more than one
 * string neighbor of the same color.  In this case, the return value
 * is -1.  Captures are not handled, so if ignore_capture is 0, and
 * a capture is required, -1 is returned.
 *
 * The intent of this function is to be as fast as possible, not
 * necessarily complete.
 */

intfastlib(int pos, int color, int ignore_capture) {
  int k;
  int ally = 0;
  int fast_liberties = 0;
  int other = OTHER_COLOR(color);
  int neighbor;
  int neighbor_color;

  ASSERT_ON_BOARD1(pos);
  ASSERT1(board[pos] == EMPTY, pos);
  ASSERT1(IS_STONE(color), pos);

  if (!strings_initialized)
    init_board();

  for (k = 0; k < 4; k++) {
    neighbor = pos + delta[k];
    if (board[neighbor] == color) {
      if (ally) {
        if (string_number[ally] != string_number[neighbor]) { 
          return -1; /* More than 1 ally not implemented (yet).*/
        }  /* otherwise, do nothing - keep going */
      } else {
        ally = neighbor;
        fast_liberties += countlib(ally) - 1;
      }
    }
  }
  for (k = 0; k < 4; k++) {
    neighbor = pos + delta[k];
    neighbor_color = board[neighbor];
    if (!ignore_capture
        && neighbor_color == other
        && countlib(neighbor) == 1) {
      return -1;
    }
    if (neighbor_color == EMPTY) {
      if (!ally || !liberty_of_string(neighbor, ally)) {
        fast_liberties++;
      }
    }
  }
  return fast_liberties;
}