Spatial: Accurate analysis of hashing function performance

[pachi/nmclean.git] / patternsp.c

#define DEBUG
#include <assert.h>
#include <ctype.h>
#include <inttypes.h>
#include <stdio.h>
#include <stdlib.h>

#include "board.h"
#include "debug.h"
#include "pattern.h"
#include "patternsp.h"

/* Mapping from point sequence to coordinate offsets (to determine
 * coordinates relative to pattern center). The array is ordered
 * in the gridcular metric order so that we can go through it
 * and incrementally match spatial features in nested circles.
 * Within one circle, coordinates are ordered by rows to keep
 * good cache behavior. */
struct ptcoord ptcoords[MAX_PATTERN_AREA];

/* For each radius, starting index in ptcoords[]. */
int ptind[MAX_PATTERN_DIST + 2];

/* ptcoords[], ptind[] setup */
static void
ptcoords_init(void)
{
        int i = 0; /* Indexing ptcoords[] */

        /* First, center point. */
        ptind[0] = ptind[1] = 0;
        ptcoords[i].x = ptcoords[i].y = 0; i++;

        for (int d = 2; d <= MAX_PATTERN_DIST; d++) {
                ptind[d] = i;
                /* For each y, examine all integer solutions
                 * of d = |x| + |y| + max(|x|, |y|). */
                /* TODO: (Stern, 2006) uses a hand-modified
                 * circles that are finer for small d and more
                 * coarse for large d. */
                for (short y = d / 2; y >= 0; y--) {
                        short x;
                        if (y > d / 3) {
                                /* max(|x|, |y|) = |y|, non-zero x */
                                x = d - y * 2;
                                if (x + y * 2 != d) continue;
                        } else {
                                /* max(|x|, |y|) = |x| */
                                /* Or, max(|x|, |y|) = |y| and x is zero */
                                x = (d - y) / 2;
                                if (x * 2 + y != d) continue;
                        }

                        assert((x > y ? x : y) + x + y == d);

                        ptcoords[i].x = x; ptcoords[i].y = y; i++;
                        if (x != 0) { ptcoords[i].x = -x; ptcoords[i].y = y; i++; }
                        if (y != 0) { ptcoords[i].x = x; ptcoords[i].y = -y; i++; }
                        if (x != 0 && y != 0) { ptcoords[i].x = -x; ptcoords[i].y = -y; i++; }
                }
        }
        ptind[MAX_PATTERN_DIST + 1] = i;

#if 0
        for (int d = 0; d <= MAX_PATTERN_DIST; d++) {
                fprintf(stderr, "d=%d (%d) ", d, ptind[d]);
                for (int j = ptind[d]; j < ptind[d + 1]; j++) {
                        fprintf(stderr, "%d,%d ", ptcoords[j].x, ptcoords[j].y);
                }
                fprintf(stderr, "\n");
        }
#endif
}


/* Zobrist hashes used for points in patterns. */
hash_t pthashes[PTH__ROTATIONS][MAX_PATTERN_AREA][S_MAX];

static void
pthashes_init(void)
{
        /* We need fixed hashes for all pattern-relative in
         * all pattern users! This is a simple way to generate
         * hopefully good ones. Park-Miller powa. :) */

        /* We create a virtual board (centered at the sequence start),
         * plant the hashes there, then pick them up into the sequence
         * with correct coordinates. It would be possible to generate
         * the sequence point hashes directly, but the rotations would
         * make for enormous headaches. */
#define PATTERN_BOARD_SIZE ((MAX_PATTERN_DIST + 1) * (MAX_PATTERN_DIST + 1))
        hash_t pthboard[PATTERN_BOARD_SIZE][4];
        int pthbc = PATTERN_BOARD_SIZE / 2; // tengen coord

        /* The magic numbers are tuned for minimal collisions. */
        hash_t h1 = 0xd6d6d6d1;
        hash_t h2 = 0xd6d6d6d2;
        hash_t h3 = 0xd6d6d6d3;
        hash_t h4 = 0xd6d6d6d4;
        for (int i = 0; i < PATTERN_BOARD_SIZE; i++) {
                pthboard[i][S_NONE] = (h1 = h1 * 16787);
                pthboard[i][S_BLACK] = (h2 = h2 * 16823);
                pthboard[i][S_WHITE] = (h3 = h3 * 16811 - 13);
                pthboard[i][S_OFFBOARD] = (h4 = h4 * 16811);
        }

        /* Virtual board with hashes created, now fill
         * pthashes[] with hashes for points in actual
         * sequences, also considering various rotations. */
#define PTH_VMIRROR     1
#define PTH_HMIRROR     2
#define PTH_90ROT       4
        for (int r = 0; r < PTH__ROTATIONS; r++) {
                for (int i = 0; i < MAX_PATTERN_AREA; i++) {
                        /* Rotate appropriately. */
                        int rx = ptcoords[i].x;
                        int ry = ptcoords[i].y;
                        if (r & PTH_VMIRROR) ry = -ry;
                        if (r & PTH_HMIRROR) rx = -rx;
                        if (r & PTH_90ROT) {
                                int rs = rx; rx = -ry; ry = rs;
                        }
                        int bi = pthbc + ry * (MAX_PATTERN_DIST + 1) + rx;

                        /* Copy info. */
                        pthashes[r][i][S_NONE] = pthboard[bi][S_NONE];
                        pthashes[r][i][S_BLACK] = pthboard[bi][S_BLACK];
                        pthashes[r][i][S_WHITE] = pthboard[bi][S_WHITE];
                        pthashes[r][i][S_OFFBOARD] = pthboard[bi][S_OFFBOARD];
                }
        }
}

static void __attribute__((constructor))
spatial_init(void)
{
        /* Initialization of various static data structures for
         * fast pattern processing. */
        ptcoords_init();
        pthashes_init();
}

inline hash_t
spatial_hash(int rotation, struct spatial *s)
{
        hash_t h = 0;
        for (int i = 0; i < ptind[s->dist + 1]; i++) {
                h ^= pthashes[rotation][i][spatial_point_at(*s, i)];
        }
        return h & spatial_hash_mask;
}

char *
spatial2str(struct spatial *s)
{
        static char buf[1024];
        for (int i = 0; i < ptind[s->dist + 1]; i++) {
                buf[i] = stone2char(spatial_point_at(*s, i));
        }
        buf[ptind[s->dist + 1]] = 0;
        return buf;
}

void
spatial_from_board(struct pattern_config *pc, struct spatial *s,
                   struct board *b, struct move *m)
{
        assert(pc->spat_min > 0);

        /* We record all spatial patterns black-to-play; simply
         * reverse all colors if we are white-to-play. */
        static enum stone bt_black[4] = { S_NONE, S_BLACK, S_WHITE, S_OFFBOARD };
        static enum stone bt_white[4] = { S_NONE, S_WHITE, S_BLACK, S_OFFBOARD };
        enum stone (*bt)[4] = m->color == S_WHITE ? &bt_white : &bt_black;

        memset(s, 0, sizeof(*s));
        for (int j = 0; j < ptind[pc->spat_max + 1]; j++) {
                ptcoords_at(x, y, m->coord, b, j);
                s->points[j / 4] |= (*bt)[board_atxy(b, x, y)] << ((j % 4) * 2);
        }
        s->dist = pc->spat_max;
}

/* Compare two spatials, allowing for differences up to isomorphism.
 * True means the spatials are equivalent. */
static bool
spatial_cmp(struct spatial *s1, struct spatial *s2)
{
        /* Quick preliminary check. */
        if (s1->dist != s2->dist)
                return false;

        /* We could create complex transposition tables, but it seems most
         * foolproof to just check if the sets of rotation hashes are the
         * same for both. */
        hash_t s1r[PTH__ROTATIONS];
        for (int r = 0; r < PTH__ROTATIONS; r++)
                s1r[r] = spatial_hash(r, s1);
        for (int r = 0; r < PTH__ROTATIONS; r++) {
                hash_t s2r = spatial_hash(r, s2);
                for (int p = 0; p < PTH__ROTATIONS; p++)
                        if (s2r == s1r[p])
                                goto found_rot;
                /* Rotation hash s2r does not correspond to s1r. */
                return false;
found_rot:;
        }

        /* All rotation hashes of s2 occur in s1. Hopefully that
         * indicates something. */
        return true;
}


/* Spatial dict manipulation. */

static unsigned int
spatial_dict_addc(struct spatial_dict *dict, struct spatial *s)
{
        /* Allocate space in 1024 blocks. */
#define SPATIALS_ALLOC 1024
        if (!(dict->nspatials % SPATIALS_ALLOC)) {
                dict->spatials = realloc(dict->spatials,
                                (dict->nspatials + SPATIALS_ALLOC)
                                * sizeof(*dict->spatials));
        }
        dict->spatials[dict->nspatials] = *s;
        return dict->nspatials++;
}

bool
spatial_dict_addh(struct spatial_dict *dict, hash_t hash, unsigned int id)
{
        if (dict->hash[hash]) {
                if (dict->hash[hash] != id)
                        dict->collisions++;
        } else {
                dict->fills++;
        }
        dict->hash[hash] = id;
        return true;
}

/* Spatial dictionary file format:
 * /^#/ - comments
 * INDEX RADIUS STONES HASH...
 * INDEX: index in the spatial table
 * RADIUS: @d of the pattern
 * STONES: string of ".XO#" chars
 * HASH...: space-separated 18bit hash-table indices for the pattern */

static void
spatial_dict_read(struct spatial_dict *dict, char *buf, bool hash)
{
        /* XXX: We trust the data. Bad data will crash us. */
        char *bufp = buf;

        unsigned int index, radius;
        index = strtoul(bufp, &bufp, 10);
        radius = strtoul(bufp, &bufp, 10);
        while (isspace(*bufp)) bufp++;

        /* Load the stone configuration. */
        struct spatial s = { .dist = radius };
        int sl = 0;
        while (!isspace(*bufp)) {
                s.points[sl / 4] |= char2stone(*bufp++) << ((sl % 4)*2);
                sl++;
        }
        while (isspace(*bufp)) bufp++;

        /* Sanity check. */
        if (sl != ptind[s.dist + 1]) {
                fprintf(stderr, "Spatial dictionary: Invalid number of stones (%d != %d) on this line: %s\n",
                        sl, ptind[radius + 1] - 1, buf);
                exit(EXIT_FAILURE);
        }

        /* Add to collection. */
        unsigned int id = spatial_dict_addc(dict, &s);
        assert(id == index);

        /* Add to specified hash places. */
        if (hash)
                for (int r = 0; r < PTH__ROTATIONS; r++)
                        spatial_dict_addh(dict, spatial_hash(r, &s), id);
}

void
spatial_write(struct spatial_dict *dict, struct spatial *s, int id, FILE *f)
{
        fprintf(f, "%d %d ", id, s->dist);
        fputs(spatial2str(s), f);
        for (int r = 0; r < PTH__ROTATIONS; r++) {
                hash_t rhash = spatial_hash(r, s);
                int id2 = dict->hash[rhash];
                if (id2 != id) {
                        /* This hash does not belong to us. Decide whether
                         * we or the current owner is better owner. */
                        /* TODO: Compare also # of patternscan encounters? */
                        struct spatial *s2 = &dict->spatials[id2];
                        if (s2->dist < s->dist)
                                continue;
                        if (s2->dist == s->dist && id2 < id)
                                continue;
                }
                fprintf(f, " %"PRIhash"", spatial_hash(r, s));
        }
        fputc('\n', f);
}

static void
spatial_dict_load(struct spatial_dict *dict, FILE *f, bool hash)
{
        char buf[1024];
        while (fgets(buf, sizeof(buf), f)) {
                if (buf[0] == '#') continue;
                spatial_dict_read(dict, buf, hash);
        }
        if (DEBUGL(1)) {
                fprintf(stderr, "Loaded spatial dictionary of %d patterns.\n", dict->nspatials);
                if (hash)
                        spatial_dict_hashstats(dict);
        }
}

void
spatial_dict_hashstats(struct spatial_dict *dict)
{
        /* m hash size, n number of patterns; is zobrist universal hash?
         *
         * Not so rigorous analysis, but it should give a good approximation:
         * Probability of empty bucket is (1-1/m)^n ~ e^(-n/m)
         * Probability of non-empty bucket is 1-e^(-n/m)
         * Expected number of non-empty buckets is m*(1-e^(-n/m))
         * Number of collisions is n-m*(1-e^(-n/m)). */

        /* The result: Reality matches these expectations pretty well!
         *
         * Actual:
         *      Loaded spatial dictionary of 1064482 patterns.
         *      (Spatial dictionary hash: 513997 collisions (incl. repetitions), 11.88% (7970033/67108864) fill rate).
         *
         * Theoretical:
         *      m = 2^26
         *      n <= 8*1064482 (some patterns may have some identical rotations)
         *      n = 513997+7970033 = 8484030 should be the correct number
         *      n-m*(1-e^(-n/m)) = 514381
         *
         * To verify, make sure to turn patternprob off (e.g. use
         * -e patternscan), since it will insert a pattern multiple times,
         * multiplying the reported number of collisions. */

        unsigned long buckets = (sizeof(dict->hash) / sizeof(dict->hash[0]));
        fprintf(stderr, "\t(Spatial dictionary hash: %d collisions (incl. repetitions), %.2f%% (%d/%lu) fill rate).\n",
                        dict->collisions,
                        (double) dict->fills * 100 / buckets,
                        dict->fills, buckets);
}

void
spatial_dict_writeinfo(struct spatial_dict *dict, FILE *f)
{
        /* New file. First, create a comment describing order
         * of points in the array. This is just for purposes
         * of external tools, Pachi never interprets it itself. */
        fprintf(f, "# Pachi spatial patterns dictionary v1.0 maxdist %d\n",
                MAX_PATTERN_DIST);
        for (int d = 0; d <= MAX_PATTERN_DIST; d++) {
                fprintf(f, "# Point order: d=%d ", d);
                for (int j = ptind[d]; j < ptind[d + 1]; j++) {
                        fprintf(f, "%d,%d ", ptcoords[j].x, ptcoords[j].y);
                }
                fprintf(f, "\n");
        }
}

/* We try to avoid needlessly reloading spatial dictionary
 * since it may take rather long time. */
static struct spatial_dict *cached_dict;

const char *spatial_dict_filename = "patterns.spat";
struct spatial_dict *
spatial_dict_init(bool will_append, bool hash)
{
        if (cached_dict && !will_append)
                return cached_dict;

        FILE *f = fopen(spatial_dict_filename, "r");
        if (!f && !will_append) {
                if (DEBUGL(1))
                        fprintf(stderr, "No spatial dictionary, will not match spatial pattern features.\n");
                return NULL;
        }

        struct spatial_dict *dict = calloc2(1, sizeof(*dict));
        /* We create a dummy record for index 0 that we will
         * never reference. This is so that hash value 0 can
         * represent "no value". */
        struct spatial dummy = { .dist = 0 };
        spatial_dict_addc(dict, &dummy);

        if (f) {
                spatial_dict_load(dict, f, hash);
                fclose(f); f = NULL;
        } else {
                assert(will_append);
        }

        cached_dict = dict;
        return dict;
}

int
spatial_dict_put(struct spatial_dict *dict, struct spatial *s, hash_t h)
{
        /* We avoid spatial_dict_get() here, since we want to ignore radius
         * differences - we have custom collision detection. */
        int id = dict->hash[h];
        if (id > 0) {
                /* Is this the same or isomorphous spatial? */
                if (spatial_cmp(s, &dict->spatials[id]))
                        return id;

                /* Look a bit harder - perhaps one of our rotations still
                 * points at the correct spatial. */
                for (int r = 0; r < PTH__ROTATIONS; r++) {
                        hash_t rhash = spatial_hash(r, s);
                        int rid = dict->hash[rhash];
                        /* No match means we definitely aren't stored yet. */
                        if (!rid)
                                break;
                        if (id != rid && spatial_cmp(s, &dict->spatials[rid])) {
                                /* Yay, this is us! */
                                if (DEBUGL(3))
                                        fprintf(stderr, "Repeated collision %d vs %d\n", id, rid);
                                id = rid;
                                /* Point the hashes back to us. */
                                goto hash_store;
                        }
                }

                if (DEBUGL(1))
                        fprintf(stderr, "Collision %d vs %d\n", id, dict->nspatials);
                id = 0;
                /* dict->collisions++; gets done by addh */
        }

        /* Add new pattern! */
        id = spatial_dict_addc(dict, s);
        if (DEBUGL(4)) {
                fprintf(stderr, "new spat %d(%d) %s <%"PRIhash"> ", id, s->dist, spatial2str(s), h);
                for (int r = 0; r < 8; r++)
                        fprintf(stderr,"[%"PRIhash"] ", spatial_hash(r, s));
                fprintf(stderr, "\n");
        }

        /* Store new pattern in the hash. */
hash_store:
        for (int r = 0; r < PTH__ROTATIONS; r++)
                spatial_dict_addh(dict, spatial_hash(r, s), id);

        return id;
}