tactics/util.h

   1 #ifndef PACHI_TACTICS_UTIL_H
   2 #define PACHI_TACTICS_UTIL_H
   3
   4 /* Advanced tactical checks non-essential to the board implementation. */
   5
   6 #include "board.h"
   7 #include "debug.h"
   8
   9 struct move_queue;
  10
  11 /* Checks if there are any stones in n-vincinity of coord. */
  12 bool board_stone_radar(struct board *b, coord_t coord, int distance);
  13
  14 /* Measure various distances on the board: */
  15 /* Distance from the edge; on edge returns 0. */
  16 static int coord_edge_distance(coord_t c, struct board *b);
  17 /* Distance of two points in gridcular metric - this metric defines
  18  * circle-like structures on the square grid. */
  19 static int coord_gridcular_distance(coord_t c1, coord_t c2, struct board *b);
  20
  21 /* Construct a "common fate graph" from given coordinate; that is, a weighted
  22  * graph of intersections where edges between all neighbors have weight 1,
  23  * but edges between neighbors of same color have weight 0. Thus, this is
  24  * "stone chain" metric in a sense. */
  25 /* The output are distanes from start stored in given [board_size2()] array;
  26  * intersections further away than maxdist have all distance maxdist+1 set. */
  27 void cfg_distances(struct board *b, coord_t start, int *distances, int maxdist);
  28
  29 /* Compute an extra komi describing the "effective handicap" black receives
  30  * (returns 0 for even game with 7.5 komi). @stone_value is value of single
  31  * handicap stone, 7 is a good default. */
  32 /* This is just an approximation since in reality, handicap seems to be usually
  33  * non-linear. */
  34 floating_t board_effective_handicap(struct board *b, int first_move_value);
  35
  36 /* Decide if the given player wins counting on the board, considering
  37  * that given groups are dead. (To get the list of dead groups, use
  38  * e.g. groups_of_status().) */
  39 bool pass_is_safe(struct board *b, enum stone color, struct move_queue *mq);
  40
  41 /* Returns estimated number of remaining moves for one player until end of game. */
  42 int board_estimated_moves_left(struct board *b);
  43
  44 /* To avoid running out of time, assume we always have at least 30 more moves
  45  * to play if we don't have more precise information from gtp time_left: */
  46 #define MIN_MOVES_LEFT 30
  47
  48 /* Tactical evaluation of move @coord by color @color, given
  49  * simulation end position @b. I.e., a move is tactically good
  50  * if the resulting group stays on board until the game end.
  51  * The value is normalized to [0,1]. */
  52 /* We can also take into account surrounding stones, e.g. to
  53  * encourage taking off external liberties during a semeai. */
  54 static double board_local_value(bool scan_neis, struct board *b, coord_t coord, enum stone color);
  55
  56
  57 static inline int
  58 coord_edge_distance(coord_t c, struct board *b)
  59 {
  60         int x = coord_x(c, b), y = coord_y(c, b);
  61         int dx = x > board_size(b) / 2 ? board_size(b) - 1 - x : x;
  62         int dy = y > board_size(b) / 2 ? board_size(b) - 1 - y : y;
  63         return (dx < dy ? dx : dy) - 1 /* S_OFFBOARD */;
  64 }
  65
  66 static inline int
  67 coord_gridcular_distance(coord_t c1, coord_t c2, struct board *b)
  68 {
  69         int dx = abs(coord_dx(c1, c2, b)), dy = abs(coord_dy(c1, c2, b));
  70         return dx + dy + (dx > dy ? dx : dy);
  71 }
  72
  73 static inline double
  74 board_local_value(bool scan_neis, struct board *b, coord_t coord, enum stone color)
  75 {
  76         if (scan_neis) {
  77                 /* Count surrounding friendly stones and our eyes. */
  78                 int friends = 0;
  79                 foreach_neighbor(b, coord, {
  80                         friends += board_at(b, c) == color || board_at(b, c) == S_OFFBOARD || board_is_one_point_eye(b, c, color);
  81                 });
  82                 return (double) (2 * (board_at(b, coord) == color) + friends) / 6.f;
  83         } else {
  84                 return (board_at(b, coord) == color) ? 1.f : 0.f;
  85         }
  86 }
  87
  88 #endif