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Skip offset calculation in slider attacks

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Another small simplification and micro optimization.

No functional change in both 32 and 64 bits.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This commit is contained in:
Marco Costalba
2011-06-05 14:41:59 +01:00
parent 670cee44f0
commit b1b0c64046
2 changed files with 19 additions and 21 deletions
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15
src/bitboard.h
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@@ -69,16 +69,13 @@ extern uint8_t BitCount8Bit[256];
struct Magics {
Bitboard mask;
uint64_t mult;
uint32_t offset;
uint32_t shift;
Bitboard* attacks;
};
extern Magics RMagics[64];
extern Magics BMagics[64];
extern Bitboard RAttacks[0x19000];
extern Bitboard BAttacks[0x1480];
/// Functions for testing whether a given bit is set in a bitboard, and for
/// setting and clearing bits.
@@ -176,12 +173,12 @@ inline Bitboard in_front_bb(Color c, Square s) {
inline Bitboard rook_attacks_bb(Square s, Bitboard occ) {
const Magics& m = RMagics[s];
return RAttacks[m.offset + (((occ & m.mask) * m.mult) >> m.shift)];
return m.attacks[((occ & m.mask) * m.mult) >> m.shift];
}
inline Bitboard bishop_attacks_bb(Square s, Bitboard occ) {
const Magics& m = BMagics[s];
return BAttacks[m.offset + (((occ & m.mask) * m.mult) >> m.shift)];
return m.attacks[((occ & m.mask) * m.mult) >> m.shift];
}
#else // if !defined(IS_64BIT)
@@ -189,15 +186,13 @@ inline Bitboard bishop_attacks_bb(Square s, Bitboard occ) {
inline Bitboard rook_attacks_bb(Square s, Bitboard occ) {
const Magics& m = RMagics[s];
Bitboard b = occ & m.mask;
return RAttacks[m.offset +
((unsigned(b) * unsigned(m.mult) ^ unsigned(b >> 32) * unsigned(m.mult >> 32)) >> m.shift)];
return m.attacks[(unsigned(b) * unsigned(m.mult) ^ unsigned(b >> 32) * unsigned(m.mult >> 32)) >> m.shift];
}
inline Bitboard bishop_attacks_bb(Square s, Bitboard occ) {
const Magics& m = BMagics[s];
Bitboard b = occ & m.mask;
return BAttacks[m.offset +
((unsigned(b) * unsigned(m.mult) ^ unsigned(b >> 32) * unsigned(m.mult >> 32)) >> m.shift)];
return m.attacks[(unsigned(b) * unsigned(m.mult) ^ unsigned(b >> 32) * unsigned(m.mult >> 32)) >> m.shift];
}
#endif