UCT Prior: Enable b19, cfgd by default

[pachi.git] / tactics.c

#include <assert.h>
#include <stdio.h>
#include <stdlib.h>

#include "board.h"
#include "debug.h"


bool
is_bad_selfatari_slow(struct board *b, enum stone color, coord_t to)
{
        //fprintf(stderr, "sar check %s %s\n", stone2str(color), coord2sstr(to, b));
        /* Assess if we actually gain any liberties by this escape route.
         * Note that this is not 100% as we cannot check whether we are
         * connecting out or just to ourselves. */
        int groupcts[S_MAX] = {};
        group_t groupids[S_MAX][4] = {};
        foreach_neighbor(b, to, {
                enum stone s = board_at(b, c);
                groupids[s][groupcts[s]++] = group_at(b, c);
        });

        /* We have shortage of liberties; that's the point. */
        assert(groupcts[S_NONE] <= 1);

        /* This is set if this move puts a group out of _all_
         * liberties; we need to watch out for snapback then. */
        bool friend_has_no_libs = false;
        /* We may have one liberty, but be looking for one more.
         * In that case, @needs_more_lib is id of group
         * already providing one, don't consider it again. */
        group_t needs_more_lib = 0;
        /* ID of the first liberty, providing it again is not
         * interesting. */
        coord_t needs_more_lib_except = 0;

        /* Examine friendly groups: */
        for (int i = 0; i < 4; i++) {
                /* We can escape by connecting to this group if it's
                 * not in atari. */
                group_t g = groupids[color][i];
                if (!g) continue;

                if (board_group_info(b, g).libs == 1) {
                        if (!needs_more_lib)
                                friend_has_no_libs = true;
                        // or we already have a friend with 1 lib
                        continue;
                }

                /* Could we self-atari the group here? */
                if (board_group_info(b, g).libs > 2)
                        return false;

                /* We need to have another liberty, and
                 * it must not be the other liberty of
                 * the group. */
                int lib2 = board_group_info(b, g).lib[0];
                if (lib2 == to) lib2 = board_group_info(b, g).lib[1];
                /* Maybe we already looked at another
                 * group providing one liberty? */
                if (needs_more_lib && needs_more_lib != g
                    && needs_more_lib_except != lib2)
                        return false;

                /* Can we get the liberty locally? */
                /* Yes if we are route to more liberties... */
                if (groupcts[S_NONE] > 1)
                        return false;
                /* ...or one liberty, but not lib2. */
                if (groupcts[S_NONE] > 0
                    && !coord_is_adjecent(lib2, to, b))
                        return false;

                /* ...ok, then we can still contribute a liberty
                 * later by capturing something. */
                needs_more_lib = g;
                needs_more_lib_except = lib2;
                friend_has_no_libs = false;
        }

        //fprintf(stderr, "no friendly group\n");

        /* We may be able to gain a liberty by capturing this group. */
        group_t can_capture = 0;

        /* Examine enemy groups: */
        for (int i = 0; i < 4; i++) {
                /* We can escape by capturing this group if it's in atari. */
                group_t g = groupids[stone_other(color)][i];
                if (!g || board_group_info(b, g).libs > 1)
                        continue;

                /* But we need to get to at least two liberties by this;
                 * we already have one outside liberty, or the group is
                 * more than 1 stone (in that case, capturing is always
                 * nice!). */
                if (groupcts[S_NONE] > 0 || !group_is_onestone(b, g))
                        return false;
                /* ...or, it's a ko stone, */
                if (neighbor_count_at(b, g, color) + neighbor_count_at(b, g, S_OFFBOARD) == 3) {
                        /* and we don't have a group to save: then, just taking
                         * single stone means snapback! */
                        if (!friend_has_no_libs)
                                return false;
                }
                /* ...or, we already have one indirect liberty provided
                 * by another group. */
                if (needs_more_lib || (can_capture && can_capture != g))
                        return false;
                can_capture = g;

        }

        //fprintf(stderr, "no cap group\n");

        if (!needs_more_lib && !can_capture && !groupcts[S_NONE]) {
                /* We have no hope for more fancy tactics - this move is simply
                 * a suicide, not even a self-atari. */
                //fprintf(stderr, "suicide\n");
                return true;
        }
        /* XXX: I wonder if it makes sense to continue if we actually
         * just !needs_more_lib. */

        /* There is another possibility - we can self-atari if it is
         * a nakade: we put an enemy group in atari from the inside. */
        /* This branch also allows eyes falsification:
         * O O O . .  (This is different from throw-in to false eye
         * X X O O .  checked below in that there is no X stone at the
         * X . X O .  right of the star point in this diagram.)
         * X X X O O
         * X O * . . */
        /* TODO: Allow to only nakade if the created shape is dead
         * (http://senseis.xmp.net/?Nakade). */

        /* This branch also covers snapback, which is kind of special
         * nakade case. ;-) */
        for (int i = 0; i < 4; i++) {
                group_t g = groupids[stone_other(color)][i];
                if (!g || board_group_info(b, g).libs != 2)
                        continue;
                /* Simple check not to re-examine the same group. */
                if (i > 0 && groupids[stone_other(color)][i] == groupids[stone_other(color)][i - 1])
                        continue;

                /* We must make sure the other liberty of that group:
                 * (i) is an internal liberty
                 * (ii) filling it to capture our group will not gain
                 * safety */

                /* Let's look at the other liberty neighbors: */
                int lib2 = board_group_info(b, g).lib[0];
                if (lib2 == to) lib2 = board_group_info(b, g).lib[1];
                foreach_neighbor(b, lib2, {
                        /* This neighbor of course does not contribute
                         * anything to the enemy. */
                        if (board_at(b, c) == S_OFFBOARD)
                                continue;

                        /* If the other liberty has empty neighbor,
                         * it must be the original liberty; otherwise,
                         * since the whole group has only 2 liberties,
                         * the other liberty may not be internal and
                         * we are nakade'ing eyeless group from outside,
                         * which is stupid. */
                        if (board_at(b, c) == S_NONE) {
                                if (c == to)
                                        continue;
                                else
                                        goto invalid_nakade;
                        }

                        int g2 = group_at(b, c);
                        /* If the neighbor is of our color, it must
                         * be our group; if it is a different group,
                         * it must not be in atari. */
                        /* X X X X  We will not allow play on 'a',
                         * X X a X  because 'b' would capture two
                         * X O b X  different groups, forming two
                         * X X X X  eyes. */
                        if (board_at(b, c) == color) {
                                if (board_group_info(b, group_at(b, c)).libs > 1)
                                        continue;
                                /* Our group == one of the groups
                                 * we (@to) are connected to. */
                                int j;
                                for (j = 0; j < 4; j++)
                                        if (groupids[color][j] == g2)
                                                break;
                                if (j == 4)
                                        goto invalid_nakade;
                                continue;
                        }

                        /* The neighbor is enemy color. It's ok if
                         * it's still the same group or this is its
                         * only liberty. */
                        if (g == g2 || board_group_info(b, g2).libs == 1)
                                continue;
                        /* Otherwise, it must have the exact same
                         * liberties as the original enemy group. */
                        if (board_group_info(b, g2).libs == 2
                            && (board_group_info(b, g2).lib[0] == to
                                || board_group_info(b, g2).lib[1] == to))
                                continue;

                        goto invalid_nakade;
                });

                /* Now, we must distinguish between nakade and eye
                 * falsification; we must not falsify an eye by more
                 * than two stones. */
                if (groupcts[color] < 1 ||
                    (groupcts[color] == 1 && group_is_onestone(b, groupids[color][0])))
                        return false;

                /* We would create more than 2-stone group; in that
                 * case, the liberty of our result must be lib2,
                 * indicating this really is a nakade. */
                for (int j = 0; j < 4; j++) {
                        group_t g2 = groupids[color][j];
                        if (!g2) continue;
                        assert(board_group_info(b, g2).libs <= 2);
                        if (board_group_info(b, g2).libs == 2) {
                                if (board_group_info(b, g2).lib[0] != lib2
                                    && board_group_info(b, g2).lib[1] != lib2)
                                        goto invalid_nakade;
                        } else {
                                assert(board_group_info(b, g2).lib[0] == to);
                        }
                }

                return false;

invalid_nakade:;
        }

        //fprintf(stderr, "no nakade group\n");

        /* We can be throwing-in to false eye:
         * X X X O X X X O X X X X X
         * X . * X * O . X * O O . X
         * # # # # # # # # # # # # # */
        /* We cannot sensibly throw-in into a corner. */
        if (neighbor_count_at(b, to, S_OFFBOARD) < 2
            && neighbor_count_at(b, to, stone_other(color))
               + neighbor_count_at(b, to, S_OFFBOARD) == 3
            && board_is_false_eyelike(b, &to, stone_other(color))) {
                assert(groupcts[color] <= 1);
                /* Single-stone throw-in may be ok... */
                if (groupcts[color] == 0) {
                        /* O X .  There is one problem - when it's
                         * . * X  actually not a throw-in!
                         * # # #  */
                        foreach_neighbor(b, to, {
                                if (board_at(b, c) == S_NONE) {
                                        /* Is the empty neighbor an escape path? */
                                        /* (Note that one S_NONE neighbor is already @to.) */
                                        if (neighbor_count_at(b, c, stone_other(color))
                                            + neighbor_count_at(b, c, S_OFFBOARD) < 2)
                                                goto invalid_throwin;
                                }
                        });
                        return false;
                }

                /* Multi-stone throwin...? */
                assert(groupcts[color] == 1);
                group_t g = groupids[color][0];

                assert(board_group_info(b, g).libs <= 2);
                /* Suicide is definitely NOT ok, no matter what else
                 * we could test. */
                if (board_group_info(b, g).libs == 1)
                        return true;

                /* In that case, we must be connected to at most one stone,
                 * or throwin will not destroy any eyes. */
                if (group_is_onestone(b, g))
                        return false;
invalid_throwin:;
        }

        //fprintf(stderr, "no throw-in group\n");

        /* No way to pull out, no way to connect out. This really
         * is a bad self-atari! */
        return true;
}


bool
board_stone_radar(struct board *b, coord_t coord, int distance)
{
        int bounds[4] = {
                coord_x(coord, b) - distance,
                coord_y(coord, b) - distance,
                coord_x(coord, b) + distance,
                coord_y(coord, b) + distance
        };
        for (int i = 0; i < 4; i++)
                if (bounds[i] < 1)
                        bounds[i] = 1;
                else if (bounds[i] > board_size(b) - 2)
                        bounds[i] = board_size(b) - 2;
        for (int x = bounds[0]; x <= bounds[2]; x++)
                for (int y = bounds[1]; y <= bounds[3]; y++)
                        if (board_atxy(b, x, y) != S_NONE) {
                                /* fprintf(stderr, "radar %d,%d,%d: %d,%d (%d)\n",
                                        coord_x(coord, b), coord_y(coord, b),
                                        distance, x, y, board_atxy(b, x, y)); */
                                return true;
                        }
        return false;
}

void
cfg_distances(struct board *b, coord_t start, int *distances, int maxdist)
{
        /* Queue for d+1 spots; no two spots of the same group
         * should appear in the queue. */
#define qinc(x) (x = ((x + 1) >= board_size2(b) ? ((x) + 1 - board_size2(b)) : (x) + 1))
        coord_t queue[board_size2(b)]; int qstart = 0, qstop = 0;

        foreach_point(b) {
                distances[c] = board_at(b, c) == S_OFFBOARD ? maxdist + 1 : -1;
        } foreach_point_end;

        queue[qstop++] = start;
        for (int d = 0; d <= maxdist; d++) {
                /* Process queued moves, while setting the queue
                 * for new wave. */
                int qa = qstart, qb = qstop;
                qstart = qstop;
                for (int q = qa; q < qb; qinc(q)) {
#define cfg_one(coord, grp) do {\
        distances[coord] = d; \
        foreach_neighbor (b, coord, { \
                if (distances[c] < 0 && (!grp || group_at(b, coord) != grp)) { \
                        queue[qstop] = c; \
                        qinc(qstop); \
                } \
        }); \
} while (0)
                        coord_t cq = queue[q];
                        if (distances[cq] >= 0)
                                continue; /* We already looked here. */
                        if (board_at(b, cq) == S_NONE) {
                                cfg_one(cq, 0);
                        } else {
                                group_t g = group_at(b, cq);
                                foreach_in_group(b, g) {
                                        cfg_one(c, g);
                                } foreach_in_group_end;
                        }
#undef cfg_one
                }
        }

        foreach_point(b) {
                if (distances[c] < 0)
                        distances[c] = maxdist + 1;
        } foreach_point_end;
}