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Document magics bitboards code

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Add comments and rename stuff to better clarify what the
magic bitboard initialization code does.

No functional change.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This commit is contained in:
Marco Costalba
2011-10-31 15:37:46 +01:00
parent 8a89b12641
commit 90890844ad
2 changed files with 73 additions and 49 deletions
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src/bitboard.h
+12 -12
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@@ -60,14 +60,14 @@ extern Bitboard SquaresInFrontMask[2][64];
extern Bitboard PassedPawnMask[2][64];
extern Bitboard AttackSpanMask[2][64];
extern uint64_t RMult[64];
extern int RShift[64];
extern Bitboard RMask[64];
extern uint64_t RMagics[64];
extern int RShifts[64];
extern Bitboard RMasks[64];
extern Bitboard* RAttacks[64];
extern uint64_t BMult[64];
extern int BShift[64];
extern Bitboard BMask[64];
extern uint64_t BMagics[64];
extern int BShifts[64];
extern Bitboard BMasks[64];
extern Bitboard* BAttacks[64];
extern Bitboard BishopPseudoAttacks[64];
@@ -172,25 +172,25 @@ inline Bitboard in_front_bb(Color c, Square s) {
#if defined(IS_64BIT)
inline Bitboard rook_attacks_bb(Square s, Bitboard occ) {
return RAttacks[s][((occ & RMask[s]) * RMult[s]) >> RShift[s]];
return RAttacks[s][((occ & RMasks[s]) * RMagics[s]) >> RShifts[s]];
}
inline Bitboard bishop_attacks_bb(Square s, Bitboard occ) {
return BAttacks[s][((occ & BMask[s]) * BMult[s]) >> BShift[s]];
return BAttacks[s][((occ & BMasks[s]) * BMagics[s]) >> BShifts[s]];
}
#else // if !defined(IS_64BIT)
inline Bitboard rook_attacks_bb(Square s, Bitboard occ) {
Bitboard b = occ & RMask[s];
Bitboard b = occ & RMasks[s];
return RAttacks[s]
[unsigned(int(b) * int(RMult[s]) ^ int(b >> 32) * int(RMult[s] >> 32)) >> RShift[s]];
[unsigned(int(b) * int(RMagics[s]) ^ int(b >> 32) * int(RMagics[s] >> 32)) >> RShifts[s]];
}
inline Bitboard bishop_attacks_bb(Square s, Bitboard occ) {
Bitboard b = occ & BMask[s];
Bitboard b = occ & BMasks[s];
return BAttacks[s]
[unsigned(int(b) * int(BMult[s]) ^ int(b >> 32) * int(BMult[s] >> 32)) >> BShift[s]];
[unsigned(int(b) * int(BMagics[s]) ^ int(b >> 32) * int(BMagics[s] >> 32)) >> BShifts[s]];
}
#endif