namespace {
// De Bruijn sequences. See chessprogramming.wikispaces.com/BitScan
- const uint64_t DeBruijn_64 = 0x218A392CD3D5DBFULL;
+ const uint64_t DeBruijn_64 = 0x3F79D71B4CB0A89ULL;
const uint32_t DeBruijn_32 = 0x783A9B23;
CACHE_LINE_ALIGNMENT
Square BSFTable[64];
Bitboard RTable[0x19000]; // Storage space for rook attacks
Bitboard BTable[0x1480]; // Storage space for bishop attacks
- uint8_t BitCount8Bit[256];
typedef unsigned (Fn)(Square, Bitboard);
void init_magics(Bitboard table[], Bitboard* attacks[], Bitboard magics[],
Bitboard masks[], unsigned shifts[], Square deltas[], Fn index);
+
+ FORCE_INLINE unsigned bsf_index(Bitboard b) {
+
+ // Matt Taylor's folding for 32 bit systems, extended to 64 bits by Kim Walisch
+ b ^= (b - 1);
+ return Is64Bit ? (b * DeBruijn_64) >> 58
+ : ((unsigned(b) ^ unsigned(b >> 32)) * DeBruijn_32) >> 26;
+ }
}
/// lsb()/msb() finds the least/most significant bit in a nonzero bitboard.
#if !defined(USE_BSFQ)
-FORCE_INLINE unsigned bsf_index(Bitboard b) {
-
- if (Is64Bit)
- return ((b & -b) * DeBruijn_64) >> 58;
-
- // Use Matt Taylor's folding trick for 32 bit systems
- b ^= (b - 1);
- return ((unsigned(b) ^ unsigned(b >> 32)) * DeBruijn_32) >> 26;
-}
-
Square lsb(Bitboard b) { return BSFTable[bsf_index(b)]; }
Square pop_lsb(Bitboard* b) {
for (int i = 0; i < 64; i++)
BSFTable[bsf_index(1ULL << i)] = Square(i);
- for (Bitboard b = 0; b < 256; b++)
- BitCount8Bit[b] = (uint8_t)popcount<Max15>(b);
-
for (Square s = SQ_A1; s <= SQ_H8; s++)
SquareBB[s] = 1ULL << s;
// until we find the one that passes the verification test.
do {
do magics[s] = pick_random(rk, booster);
- while (BitCount8Bit[(magics[s] * masks[s]) >> 56] < 6);
+ while (popcount<Max15>((magics[s] * masks[s]) >> 56) < 6);
memset(attacks[s], 0, size * sizeof(Bitboard));