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
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) {