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#include "engine/magic.h"
#include <stdlib.h>
#include <string.h>
#include <assert.h>
static magic_t rook_table[64];
static magic_t bishop_table[64];
static bitboard_t *rook_attacks_flat;
static bitboard_t *bishop_attacks_flat;
static u64 rng_state = 1070399;
static u64 random_u64(void) {
rng_state ^= rng_state << 13;
rng_state ^= rng_state >> 7;
rng_state ^= rng_state << 17;
return rng_state;
}
static u64 random_magic(void) {
return random_u64() & random_u64() & random_u64();
}
static bitboard_t compute_rook_mask(int sq) {
bitboard_t mask = 0;
int rank = sq / 8, file = sq % 8;
for (int r = rank + 1; r < 7; r++) mask |= (bitboard_t)1 << (r * 8 + file);
for (int r = rank - 1; r > 0; r--) mask |= (bitboard_t)1 << (r * 8 + file);
for (int f = file + 1; f < 7; f++) mask |= (bitboard_t)1 << (rank * 8 + f);
for (int f = file - 1; f > 0; f--) mask |= (bitboard_t)1 << (rank * 8 + f);
return mask;
}
static bitboard_t compute_bishop_mask(int sq) {
bitboard_t mask = 0;
int rank = sq / 8, file = sq % 8;
for (int r = rank + 1, f = file + 1; r < 7 && f < 7; r++, f++)
mask |= (bitboard_t)1 << (r * 8 + f);
for (int r = rank - 1, f = file - 1; r > 0 && f > 0; r--, f--)
mask |= (bitboard_t)1 << (r * 8 + f);
for (int r = rank - 1, f = file + 1; r > 0 && f < 7; r--, f++)
mask |= (bitboard_t)1 << (r * 8 + f);
for (int r = rank + 1, f = file - 1; r < 7 && f > 0; r++, f--)
mask |= (bitboard_t)1 << (r * 8 + f);
return mask;
}
static bitboard_t compute_rook_attacks_ref(int sq, bitboard_t occ) {
bitboard_t attacks = 0;
int rank = sq / 8, file = sq % 8;
for (int r = rank + 1; r < 8; r++) {
bitboard_t b = (bitboard_t)1 << (r * 8 + file);
attacks |= b;
if (occ & b) break;
}
for (int r = rank - 1; r >= 0; r--) {
bitboard_t b = (bitboard_t)1 << (r * 8 + file);
attacks |= b;
if (occ & b) break;
}
for (int f = file + 1; f < 8; f++) {
bitboard_t b = (bitboard_t)1 << (rank * 8 + f);
attacks |= b;
if (occ & b) break;
}
for (int f = file - 1; f >= 0; f--) {
bitboard_t b = (bitboard_t)1 << (rank * 8 + f);
attacks |= b;
if (occ & b) break;
}
return attacks;
}
static bitboard_t compute_bishop_attacks_ref(int sq, bitboard_t occ) {
bitboard_t attacks = 0;
int rank = sq / 8, file = sq % 8;
for (int r = rank + 1, f = file + 1; r < 8 && f < 8; r++, f++) {
bitboard_t b = (bitboard_t)1 << (r * 8 + f);
attacks |= b;
if (occ & b) break;
}
for (int r = rank - 1, f = file - 1; r >= 0 && f >= 0; r--, f--) {
bitboard_t b = (bitboard_t)1 << (r * 8 + f);
attacks |= b;
if (occ & b) break;
}
for (int r = rank - 1, f = file + 1; r >= 0 && f < 8; r--, f++) {
bitboard_t b = (bitboard_t)1 << (r * 8 + f);
attacks |= b;
if (occ & b) break;
}
for (int r = rank + 1, f = file - 1; r < 8 && f >= 0; r++, f--) {
bitboard_t b = (bitboard_t)1 << (r * 8 + f);
attacks |= b;
if (occ & b) break;
}
return attacks;
}
static void init_magic_for_square(
int sq, magic_t *entry, bool is_bishop,
bitboard_t *occs, bitboard_t *atts, bitboard_t *used
) {
int bits = 64 - entry->shift;
int count = 1 << bits;
bitboard_t mask = entry->mask;
for (int i = 0; i < count; i++) {
occs[i] = 0;
bitboard_t m = mask;
for (int j = 0; m; j++) {
if (i & (1 << j)) {
occs[i] |= (bitboard_t)1 << __builtin_ctzll(m);
}
m &= m - 1;
}
atts[i] = is_bishop
? compute_bishop_attacks_ref(sq, occs[i])
: compute_rook_attacks_ref(sq, occs[i]);
}
for (int tries = 0; tries < 100000000; tries++) {
bitboard_t magic = random_magic();
if (__builtin_popcountll((magic * mask) & 0xFF00000000000000ULL) < 6)
continue;
memset(used, 0, count * sizeof(bitboard_t));
bool fail = false;
for (int i = 0; i < count && !fail; i++) {
int idx = (int)(((occs[i] * magic) >> (64 - bits)) & (count - 1));
if (used[idx] == 0) {
used[idx] = atts[i];
} else if (used[idx] != atts[i]) {
fail = true;
}
}
if (!fail) {
entry->magic = magic;
for (int i = 0; i < count; i++) {
int idx = (int)(((occs[i] * magic) >> (64 - bits)) & (count - 1));
entry->attacks[idx] = atts[i];
}
return;
}
}
assert(0 && "Failed to find magic number");
}
void magic_init(void) {
for (int sq = 0; sq < 64; sq++) {
rook_table[sq].mask = compute_rook_mask(sq);
rook_table[sq].shift = 64 - __builtin_popcountll(rook_table[sq].mask);
bishop_table[sq].mask = compute_bishop_mask(sq);
bishop_table[sq].shift = 64 - __builtin_popcountll(bishop_table[sq].mask);
}
int rook_total = 0, bishop_total = 0;
for (int sq = 0; sq < 64; sq++) {
rook_total += 1 << (64 - rook_table[sq].shift);
bishop_total += 1 << (64 - bishop_table[sq].shift);
}
rook_attacks_flat = (bitboard_t*)malloc(rook_total * sizeof(bitboard_t));
bishop_attacks_flat = (bitboard_t*)malloc(bishop_total * sizeof(bitboard_t));
assert(rook_attacks_flat && bishop_attacks_flat);
int rook_off = 0, bishop_off = 0;
for (int sq = 0; sq < 64; sq++) {
rook_table[sq].attacks = rook_attacks_flat + rook_off;
rook_off += 1 << (64 - rook_table[sq].shift);
bishop_table[sq].attacks = bishop_attacks_flat + bishop_off;
bishop_off += 1 << (64 - bishop_table[sq].shift);
}
int max_count = 1 << 12;
bitboard_t *occs = (bitboard_t*)malloc(max_count * sizeof(bitboard_t));
bitboard_t *atts = (bitboard_t*)malloc(max_count * sizeof(bitboard_t));
bitboard_t *used = (bitboard_t*)malloc(max_count * sizeof(bitboard_t));
assert(occs && atts && used);
for (int sq = 0; sq < 64; sq++) {
init_magic_for_square(sq, &rook_table[sq], false, occs, atts, used);
}
for (int sq = 0; sq < 64; sq++) {
init_magic_for_square(sq, &bishop_table[sq], true, occs, atts, used);
}
free(occs);
free(atts);
free(used);
}
bitboard_t get_rook_attacks(int sq, bitboard_t occ) {
magic_t *m = &rook_table[sq];
return m->attacks[((occ & m->mask) * m->magic) >> m->shift];
}
bitboard_t get_bishop_attacks(int sq, bitboard_t occ) {
magic_t *m = &bishop_table[sq];
return m->attacks[((occ & m->mask) * m->magic) >> m->shift];
}
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