board.rules: Some explanations

[pachi.git] / board.h

#ifndef ZZGO_BOARD_H
#define ZZGO_BOARD_H

#include <inttypes.h>
#include <stdbool.h>
#include <stdint.h>

#include "stone.h"
#include "move.h"
#include "probdist.h"
#include "util.h"

struct features_gamma;


/* The board implementation has bunch of optional features.
 * Turn them on below: */

#define WANT_BOARD_C // capturable groups queue

//#define BOARD_SIZE 9 // constant board size, allows better optimization

//#define BOARD_SPATHASH // incremental patternsp.h hashes
#define BOARD_SPATHASH_MAXD 3 // maximal diameter

#define BOARD_PAT3 // incremental 3x3 pattern codes

//#define BOARD_TRAITS 1 // incremental point traits (see struct btraits)
//#define BOARD_GAMMA 1 // incremental probability distribution (requires BOARD_TRAITS, BOARD_PAT3)


/* Allow board_play_random_move() to return pass even when
 * there are other moves available. */
extern bool random_pass;


/* Some engines might normalize their reading and skip symmetrical
 * moves. We will tell them how can they do it. */
struct board_symmetry {
        /* Playground is in this rectangle. */
        int x1, x2, y1, y2;
        /* d ==  0: Full rectangle
         * d ==  1: Top triangle */
        int d;
        /* General symmetry type. */
        /* Note that the above is redundant to this, but just provided
         * for easier usage. */
        enum {
                SYM_FULL,
                SYM_DIAG_UP,
                SYM_DIAG_DOWN,
                SYM_HORIZ,
                SYM_VERT,
                SYM_NONE
        } type;
};


typedef uint64_t hash_t;
#define PRIhash PRIx64


/* Note that "group" is only chain of stones that is solidly
 * connected for us. */
typedef coord_t group_t;

struct group {
        /* We keep track of only up to GROUP_KEEP_LIBS; over that, we
         * don't care. */
        /* _Combination_ of these two values can make some difference
         * in performance - fine-tune. */
#define GROUP_KEEP_LIBS 10
        // refill lib[] only when we hit this; this must be at least 2!
        // Moggy requires at least 3 - see below for semantic impact.
#define GROUP_REFILL_LIBS 5
        coord_t lib[GROUP_KEEP_LIBS];
        /* libs is only LOWER BOUND for the number of real liberties!!!
         * It denotes only number of items in lib[], thus you can rely
         * on it to store real liberties only up to <= GROUP_REFILL_LIBS. */
        int libs;
};

struct neighbor_colors {
        char colors[S_MAX];
};


/* Point traits bitmap; we update this information incrementally,
 * it can be used e.g. for fast pattern.h features matching. */
struct btraits {
        /* Number of neighbors we can capture. 0=this move is
         * not capturing, 1..4=this many neighbors we can capture
         * (can be multiple neighbors of same group). */
        unsigned cap:3;
        /* Whether it is SAFE to play here. This is essentially just
         * cached result of board_safe_to_play(). (Of course the concept
         * of "safety" is not perfect here, but it's the cheapest
         * reasonable thing we can do.) */
        bool safe:1;
        /* Whether we need to re-compute this coordinate; used to
         * weed out duplicates. Maintained only for S_BLACK. */
        bool dirty:1;
};


/* You should treat this struct as read-only. Always call functions below if
 * you want to change it. */

struct board {
        int size; /* Including S_OFFBOARD margin - see below. */
        int size2; /* size^2 */
        int captures[S_MAX];
        float komi;
        int handicap;
        /* The ruleset is currently almost never taken into account;
         * the board implementation is basically Chinese rules (handicap
         * stones compensation) w/ suicide (or you can look at it as
         * New Zealand w/o handi stones compensation), while the engine
         * enforces no-suicide, making for real Chinese rules. */
        enum {
                RULES_CHINESE, /* default value */
                RULES_AGA,
                RULES_NEW_ZEALAND,
                RULES_JAPANESE,
        } rules;

        /* Iterator offsets for foreach_neighbor*() */
        int nei8[8], dnei[4];

        int moves;
        struct move last_move;
        struct move last_move2; /* second-to-last move */
        /* Whether we tried to add a hash twice; board_play*() can
         * set this, but it will still carry out the move as well! */
        bool superko_violation;

        /* The following two structures are goban maps and are indexed by
         * coord.pos. The map is surrounded by a one-point margin from
         * S_OFFBOARD stones in order to speed up some internal loops.
         * Some of the foreach iterators below might include these points;
         * you need to handle them yourselves, if you need to. */

        /* Stones played on the board */
        enum stone *b; /* enum stone */
        /* Group id the stones are part of; 0 == no group */
        group_t *g;
        /* Positions of next stones in the stone group; 0 == last stone */
        coord_t *p;
        /* Neighboring colors; numbers of neighbors of index color */
        struct neighbor_colors *n;
        /* Zobrist hash for each position */
        hash_t *h;
#ifdef BOARD_SPATHASH
        /* For spatial hashes, we use only 24 bits. */
        /* [0] is d==1, we don't keep hash for d==0. */
        /* We keep hashes for black-to-play ([][0]) and white-to-play
         * ([][1], reversed stone colors since we match all patterns as
         * black-to-play). */
        uint32_t (*spathash)[BOARD_SPATHASH_MAXD][2];
#endif
#ifdef BOARD_PAT3
        /* 3x3 pattern code for each position; see pattern3.h for encoding
         * specification. The information is only valid for empty points. */
        uint16_t *pat3;
#endif
#ifdef BOARD_TRAITS
        /* Incrementally matched point traits information, black-to-play
         * ([][0]) and white-to-play ([][1]). */
        /* The information is only valid for empty points. */
        struct btraits (*t)[2];
#endif
#ifdef BOARD_GAMMA
        /* Relative probabilities of moves being played next, computed by
         * multiplying gammas of the appropriate pattern features based on
         * pat3 and traits (see pattern.h). The probability distribution
         * is maintained over the full board grid. */
        /* - Always invalid moves are guaranteed to have zero probability.
         * - Self-eye-filling moves will always have zero probability.
         * - Ko-prohibited moves might have non-zero probability.
         * - FEAT_CONTIGUITY is not accounted for in the probability. */
        struct probdist prob[2];
#endif

        /* Group information - indexed by gid (which is coord of base group stone) */
        struct group *gi;

        /* Positions of free positions - queue (not map) */
        /* Note that free position here is any valid move; including single-point eyes! */
        coord_t *f; int flen;

#ifdef WANT_BOARD_C
        /* Queue of capturable groups */
        group_t *c; int clen;
#endif

#ifdef BOARD_TRAITS
        /* Queue of positions that need their traits updated */
        coord_t *tq; int tqlen;
#endif

        /* Symmetry information */
        struct board_symmetry symmetry;

        /* Last ko played on the board. */
        struct move last_ko;
        int last_ko_age;

        /* Basic ko check */
        struct move ko;

        /* Engine-specific state; persistent through board development,
         * is reset only at clear_board. */
        void *es;

        /* Playout-specific state; persistent through board development,
         * but its lifetime is maintained in play_random_game(); it should
         * not be set outside of it. */
        void *ps;

#ifdef BOARD_GAMMA
        /* Gamma values for probability distribution; user must setup
         * this pointer before any move is played, using board_gamma_set(). */
        struct features_gamma *gamma;
        /* Whether to compute the 'safe' trait using board_safe_to_play()
         * (false) or is_bad_selfatari() (true, much slower). */
        bool precise_selfatari;
#endif


        /* --- PRIVATE DATA --- */

        /* For superko check: */

        /* Board "history" - hashes encountered. Size of the hash should be
         * >> board_size^2. */
#define history_hash_bits 12
#define history_hash_mask ((1 << history_hash_bits) - 1)
#define history_hash_prev(i) ((i - 1) & history_hash_mask)
#define history_hash_next(i) ((i + 1) & history_hash_mask)
        hash_t history_hash[1 << history_hash_bits];
        /* Hash of current board position. */
        hash_t hash;
};

#ifdef BOARD_SIZE
/* Avoid unused variable warnings */
#define board_size(b_) (((b_) == (b_)) ? BOARD_SIZE + 2 : 0)
#define board_size2(b_) (board_size(b_) * board_size(b_))
#else
#define board_size(b_) ((b_)->size)
#define board_size2(b_) ((b_)->size2)
#endif

#define board_at(b_, c) ((b_)->b[coord_raw(c)])
#define board_atxy(b_, x, y) ((b_)->b[(x) + board_size(b_) * (y)])

#define group_at(b_, c) ((b_)->g[coord_raw(c)])
#define group_atxy(b_, x, y) ((b_)->g[(x) + board_size(b_) * (y)])

/* Warning! Neighbor count is kept up-to-date for S_NONE! */
#define neighbor_count_at(b_, coord, color) ((b_)->n[coord_raw(coord)].colors[(enum stone) color])
#define set_neighbor_count_at(b_, coord, color, count) (neighbor_count_at(b_, coord, color) = (count))
#define inc_neighbor_count_at(b_, coord, color) (neighbor_count_at(b_, coord, color)++)
#define dec_neighbor_count_at(b_, coord, color) (neighbor_count_at(b_, coord, color)--)
#define immediate_liberty_count(b_, coord) (4 - neighbor_count_at(b_, coord, S_BLACK) - neighbor_count_at(b_, coord, S_WHITE) - neighbor_count_at(b_, coord, S_OFFBOARD))

#define trait_at(b_, coord, color) (b_)->t[coord][(color) - 1]

#define groupnext_at(b_, c) ((b_)->p[coord_raw(c)])
#define groupnext_atxy(b_, x, y) ((b_)->p[(x) + board_size(b_) * (y)])

#define group_base(g_) (g_)
#define board_group_info(b_, g_) ((b_)->gi[(g_)])
#define board_group_captured(b_, g_) (board_group_info(b_, g_).libs == 0)
#define group_is_onestone(b_, g_) (groupnext_at(b_, group_base(g_)) == 0)

#define hash_at(b_, coord, color) ((b_)->h[((color) == S_BLACK ? board_size2(b_) : 0) + coord_raw(coord)])

struct board *board_init(void);
struct board *board_copy(struct board *board2, struct board *board1);
void board_done_noalloc(struct board *board);
void board_done(struct board *board);
/* size here is without the S_OFFBOARD margin. */
void board_resize(struct board *board, int size);
void board_clear(struct board *board);

struct FILE;
typedef char *(*board_cprint)(struct board *b, coord_t c, char *s, char *end);
void board_print(struct board *board, FILE *f);
void board_print_custom(struct board *board, FILE *f, board_cprint cprint);

/* Place given handicap on the board; coordinates are printed to f. */
void board_handicap(struct board *board, int stones, FILE *f);

/* Returns group id, 0 on allowed suicide, pass or resign, -1 on error */
int board_play(struct board *board, struct move *m);
/* Like above, but plays random move; the move coordinate is recorded
 * to *coord. This method will never fill your own eye. pass is played
 * when no move can be played. You can impose extra restrictions if you
 * supply your own permit function. */
typedef bool (*ppr_permit)(void *data, struct board *b, struct move *m);
void board_play_random(struct board *b, enum stone color, coord_t *coord, ppr_permit permit, void *permit_data);

/* Returns true if given move can be played. */
static bool board_is_valid_play(struct board *b, enum stone color, coord_t coord);
static bool board_is_valid_move(struct board *b, struct move *m);
/* Returns true if ko was just taken. */
static bool board_playing_ko_threat(struct board *b);
/* Returns 0 or ID of neighboring group in atari. */
static group_t board_get_atari_neighbor(struct board *b, coord_t coord, enum stone group_color);
/* Returns true if the move is not obvious self-atari. */
static bool board_safe_to_play(struct board *b, coord_t coord, enum stone color);

/* Adjust symmetry information as if given coordinate has been played. */
void board_symmetry_update(struct board *b, struct board_symmetry *symmetry, coord_t c);
/* Associate a set of feature gamma values (for pd building) with the board. */
void board_gamma_set(struct board *b, struct features_gamma *gamma, bool precise_selfatari);
/* Force re-compute of a probability distribution item. */
void board_gamma_update(struct board *b, coord_t coord, enum stone color);

/* Returns true if given coordinate has all neighbors of given color or the edge. */
static bool board_is_eyelike(struct board *board, coord_t coord, enum stone eye_color);
/* Returns true if given coordinate could be a false eye; this check makes
 * sense only if you already know the coordinate is_eyelike(). */
bool board_is_false_eyelike(struct board *board, coord_t coord, enum stone eye_color);
/* Returns true if given coordinate is a 1-pt eye (checks against false eyes, or
 * at least tries to). */
bool board_is_one_point_eye(struct board *board, coord_t c, enum stone eye_color);
/* Returns color of a 1pt eye owner, S_NONE if not an eye. */
enum stone board_get_one_point_eye(struct board *board, coord_t c);

/* board_official_score() is the scoring method for yielding score suitable
 * for external presentation. For fast scoring of entirely filled boards
 * (e.g. playouts), use board_fast_score(). */
/* Positive: W wins */
/* Compare number of stones + 1pt eyes. */
float board_fast_score(struct board *board);
/* Tromp-Taylor scoring, assuming given groups are actually dead. */
struct move_queue;
float board_official_score(struct board *board, struct move_queue *mq);

/** Iterators */

#define foreach_point(board_) \
        do { \
                coord_t c; coord_pos(c, 0, (board_)); \
                for (; coord_raw(c) < board_size(board_) * board_size(board_); coord_raw(c)++)
#define foreach_point_and_pass(board_) \
        do { \
                coord_t c; coord_pos(c, -1, (board_)); \
                for (; coord_raw(c) < board_size(board_) * board_size(board_); coord_raw(c)++)
#define foreach_point_end \
        } while (0)

#define foreach_in_group(board_, group_) \
        do { \
                struct board *board__ = board_; \
                coord_t c = group_base(group_); \
                coord_t c2 = c; coord_raw(c2) = groupnext_at(board__, c2); \
                do {
#define foreach_in_group_end \
                        c = c2; coord_raw(c2) = groupnext_at(board__, c2); \
                } while (coord_raw(c) != 0); \
        } while (0)

/* NOT VALID inside of foreach_point() or another foreach_neighbor(), or rather
 * on S_OFFBOARD coordinates. */
#define foreach_neighbor(board_, coord_, loop_body) \
        do { \
                struct board *board__ = board_; \
                coord_t coord__ = coord_; \
                coord_t c; \
                coord_pos(c, coord_raw(coord__) - 1, (board__)); do { loop_body } while (0); \
                coord_pos(c, coord_raw(coord__) - board_size(board__), (board__)); do { loop_body } while (0); \
                coord_pos(c, coord_raw(coord__) + 1, (board__)); do { loop_body } while (0); \
                coord_pos(c, coord_raw(coord__) + board_size(board__), (board__)); do { loop_body } while (0); \
        } while (0)

#define foreach_8neighbor(board_, coord_) \
        do { \
                int fn__i; \
                coord_t c = (coord_); \
                for (fn__i = 0; fn__i < 8; fn__i++) { \
                        c += (board_)->nei8[fn__i];
#define foreach_8neighbor_end \
                } \
        } while (0)

#define foreach_diag_neighbor(board_, coord_) \
        do { \
                int fn__i; \
                coord_t c = (coord_); \
                for (fn__i = 0; fn__i < 4; fn__i++) { \
                        c += (board_)->dnei[fn__i];
#define foreach_diag_neighbor_end \
                } \
        } while (0)


static inline bool
board_is_eyelike(struct board *board, coord_t coord, enum stone eye_color)
{
        return (neighbor_count_at(board, coord, eye_color)
                + neighbor_count_at(board, coord, S_OFFBOARD)) == 4;
}

static inline bool
board_is_valid_play(struct board *board, enum stone color, coord_t coord)
{
        if (board_at(board, coord) != S_NONE)
                return false;
        if (!board_is_eyelike(board, coord, stone_other(color)))
                return true;
        /* Play within {true,false} eye-ish formation */
        if (board->ko.coord == coord && board->ko.color == color)
                return false;
#ifdef BOARD_TRAITS
        /* XXX: Disallows suicide. */
        return trait_at(board, coord, color).cap > 0;
#else
        int groups_in_atari = 0;
        foreach_neighbor(board, coord, {
                group_t g = group_at(board, c);
                groups_in_atari += (board_group_info(board, g).libs == 1);
        });
        return !!groups_in_atari;
#endif
}

static inline bool
board_is_valid_move(struct board *board, struct move *m)
{
        return board_is_valid_play(board, m->color, m->coord);
}

static inline bool
board_playing_ko_threat(struct board *b)
{
        return !is_pass(b->ko.coord);
}

static inline group_t
board_get_atari_neighbor(struct board *b, coord_t coord, enum stone group_color)
{
#ifdef BOARD_TRAITS
        if (!trait_at(b, coord, stone_other(group_color)).cap) return 0;
#endif
        foreach_neighbor(b, coord, {
                group_t g = group_at(b, c);
                if (g && board_at(b, c) == group_color && board_group_info(b, g).libs == 1)
                        return g;
                /* We return first match. */
        });
        return 0;
}

static inline bool
board_safe_to_play(struct board *b, coord_t coord, enum stone color)
{
        /* number of free neighbors */
        int libs = immediate_liberty_count(b, coord);
        if (libs > 1)
                return true;

#ifdef BOARD_TRAITS
        /* number of capturable enemy groups */
        if (trait_at(b, coord, color).cap > 0)
                return true; // XXX: We don't account for snapback.
        /* number of non-capturable friendly groups */
        int noncap_ours = neighbor_count_at(b, coord, color) - trait_at(b, coord, stone_other(color)).cap;
        if (noncap_ours < 1)
                return false;
/*#else see below */
#endif

        /* ok, but we need to check if they don't have just two libs. */
        coord_t onelib = -1;
        foreach_neighbor(b, coord, {
#ifndef BOARD_TRAITS
                if (board_at(b, c) == stone_other(color) && board_group_info(b, group_at(b, c)).libs == 1)
                        return true; // can capture; no snapback check
#endif
                if (board_at(b, c) != color) continue;
                group_t g = group_at(b, c);
                if (board_group_info(b, g).libs == 1) continue; // in atari
                if (board_group_info(b, g).libs == 2) { // two liberties
                        if (libs > 0) return true; // we already have one real liberty
                        // get the other liberty
                        coord_t lib = board_group_info(b, g).lib[0];
                        if (lib == coord) lib = board_group_info(b, g).lib[0];
                        /* we might be connecting two 2-lib groups, which is ok;
                         * so remember the other liberty and just make sure it's
                         * not the same one */
                        if (onelib >= 0 && lib != onelib) return true;
                        onelib = lib;
                        continue;
                }
                // many liberties
                return true;
        });
        // no good support group
        return false;
}

#endif