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Get rid of Shift[] tables

Browse source 
We can calculate them counting the masks bits.

Also small tweak to sliding_attacks()

No functional change.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This commit is contained in:
Marco Costalba 2011-06-05 12:09:55 +01:00
parent 3092f0c646
commit 670cee44f0
2 changed files with 18 additions and 46 deletions
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60
src/bitboard.cpp
View file

@ -107,20 +107,6 @@ const uint64_t RMult[64] = {
0x410201CE5C030092ULL 0x410201CE5C030092ULL
}; };
const int BShift[64] = {
58, 59, 59, 59, 59, 59, 59, 58, 59, 59, 59, 59, 59, 59, 59, 59,
59, 59, 57, 57, 57, 57, 59, 59, 59, 59, 57, 55, 55, 57, 59, 59,
59, 59, 57, 55, 55, 57, 59, 59, 59, 59, 57, 57, 57, 57, 59, 59,
59, 59, 59, 59, 59, 59, 59, 59, 58, 59, 59, 59, 59, 59, 59, 58
};
const int RShift[64] = {
52, 53, 53, 53, 53, 53, 53, 52, 53, 54, 54, 54, 54, 54, 54, 53,
53, 54, 54, 54, 54, 54, 54, 53, 53, 54, 54, 54, 54, 54, 54, 53,
53, 54, 54, 54, 54, 54, 54, 53, 53, 54, 54, 54, 54, 54, 54, 53,
53, 54, 54, 54, 54, 54, 54, 53, 52, 53, 53, 53, 53, 53, 53, 52
};
#else // if !defined(IS_64BIT) #else // if !defined(IS_64BIT)
const uint32_t DeBruijnMagic = 0x783A9B23; const uint32_t DeBruijnMagic = 0x783A9B23;
@ -175,26 +161,11 @@ const uint64_t RMult[64] = {
0x5AC08A4735370479ULL, 0x5AC08A4735370479ULL,
}; };
const int BShift[64] = {
26, 27, 27, 27, 27, 27, 27, 26, 27, 27, 27, 27, 27, 27, 27, 27,
27, 27, 25, 25, 25, 25, 27, 27, 27, 27, 25, 23, 23, 25, 27, 27,
27, 27, 25, 23, 23, 25, 27, 27, 27, 27, 25, 25, 25, 25, 27, 27,
27, 27, 27, 27, 27, 27, 27, 27, 26, 27, 27, 27, 27, 27, 27, 26
};
const int RShift[64] = {
20, 21, 21, 21, 21, 21, 21, 20, 21, 22, 22, 22, 22, 22, 22, 21,
21, 22, 22, 22, 22, 22, 22, 21, 21, 22, 22, 22, 22, 22, 22, 21,
21, 22, 22, 22, 22, 22, 22, 21, 21, 22, 22, 22, 22, 22, 22, 21,
21, 22, 22, 22, 22, 22, 22, 21, 20, 21, 21, 21, 21, 21, 21, 20
};
#endif // defined(IS_64BIT) #endif // defined(IS_64BIT)
CACHE_LINE_ALIGNMENT int BSFTable[64]; CACHE_LINE_ALIGNMENT int BSFTable[64];
void init_sliding_attacks(Bitboard attacks[], Magics m[], const int shift[], void init_sliding_attacks(Bitboard attacks[], Magics m[], const Bitboard mult[], Square deltas[]);
const Bitboard mult[], Square deltas[]);
} }
@ -354,8 +325,8 @@ void init_bitboards() {
Square RDeltas[] = { DELTA_N, DELTA_E, DELTA_S, DELTA_W }; Square RDeltas[] = { DELTA_N, DELTA_E, DELTA_S, DELTA_W };
Square BDeltas[] = { DELTA_NE, DELTA_SE, DELTA_SW, DELTA_NW }; Square BDeltas[] = { DELTA_NE, DELTA_SE, DELTA_SW, DELTA_NW };
init_sliding_attacks(RAttacks, RMagics, RShift, RMult, RDeltas); init_sliding_attacks(RAttacks, RMagics, RMult, RDeltas);
init_sliding_attacks(BAttacks, BMagics, BShift, BMult, BDeltas); init_sliding_attacks(BAttacks, BMagics, BMult, BDeltas);
for (Square s = SQ_A1; s <= SQ_H8; s++) for (Square s = SQ_A1; s <= SQ_H8; s++)
{ {
@ -394,7 +365,7 @@ namespace {
return subMask; return subMask;
} }
Bitboard sliding_attacks(Square sq, Bitboard occupied, Square deltas[], bool skipLast) { Bitboard sliding_attacks(Square sq, Bitboard occupied, Square deltas[], Bitboard excluded) {
Bitboard attacks = 0; Bitboard attacks = 0;
@ -404,12 +375,11 @@ namespace {
while ( square_is_ok(s) while ( square_is_ok(s)
&& square_distance(s, s - deltas[i]) == 1 && square_distance(s, s - deltas[i]) == 1
&& (!skipLast || !file_distance(s, sq) || (square_file(s) != FILE_A && square_file(s) != FILE_H)) && !bit_is_set(excluded, s))
&& (!skipLast || !rank_distance(s, sq) || (square_rank(s) != RANK_1 && square_rank(s) != RANK_8)))
{ {
attacks |= 1ULL << s; set_bit(&attacks, s);
if (occupied & (1ULL << s)) if (bit_is_set(occupied, s))
break; break;
s += deltas[i]; s += deltas[i];
@ -418,19 +388,21 @@ namespace {
return attacks; return attacks;
} }
void init_sliding_attacks(Bitboard attacks[], Magics m[], const int shift[], void init_sliding_attacks(Bitboard attacks[], Magics m[], const Bitboard mult[], Square deltas[]) {
const Bitboard mult[], Square deltas[]) {
Bitboard occupancy, index; Bitboard occupancy, index, excluded;
int maxKey, offset = 0; int maxKey, offset = 0;
for (Square s = SQ_A1; s <= SQ_H8; s++) for (Square s = SQ_A1; s <= SQ_H8; s++)
{ {
excluded = ((Rank1BB | Rank8BB) & ~rank_bb(s)) | ((FileABB | FileHBB) & ~file_bb(s));
m[s].offset = offset; m[s].offset = offset;
m[s].mult = mult[s]; m[s].mult = mult[s];
m[s].shift = shift[s]; m[s].mask = sliding_attacks(s, EmptyBoardBB, deltas, excluded);
m[s].mask = sliding_attacks(s, EmptyBoardBB, deltas, true); m[s].shift = (CpuIs64Bit ? 64 : 32) - count_1s<CNT64>(m[s].mask);
maxKey = 1 << (CpuIs64Bit ? 64 - shift[s] : 32 - shift[s]); maxKey = 1 << count_1s<CNT64>(m[s].mask);
for (int key = 0; key < maxKey; key++) for (int key = 0; key < maxKey; key++)
{ {
@ -439,7 +411,7 @@ namespace {
index = CpuIs64Bit ? occupancy * mult[s] index = CpuIs64Bit ? occupancy * mult[s]
: unsigned(occupancy * mult[s] ^ (occupancy >> 32) * (mult[s] >> 32)); : unsigned(occupancy * mult[s] ^ (occupancy >> 32) * (mult[s] >> 32));
attacks[offset + (index >> shift[s])] = sliding_attacks(s, occupancy, deltas, false); attacks[offset + (index >> m[s].shift)] = sliding_attacks(s, occupancy, deltas, EmptyBoardBB);
} }
offset += maxKey; offset += maxKey;
} }

4
src/bitboard.h
View file

@ -176,12 +176,12 @@ inline Bitboard in_front_bb(Color c, Square s) {
inline Bitboard rook_attacks_bb(Square s, Bitboard occ) { inline Bitboard rook_attacks_bb(Square s, Bitboard occ) {
const Magics& m = RMagics[s]; const Magics& m = RMagics[s];
return RAttacks[m.index + (((occ & m.mask) * m.mult) >> m.shift)]; return RAttacks[m.offset + (((occ & m.mask) * m.mult) >> m.shift)];
} }
inline Bitboard bishop_attacks_bb(Square s, Bitboard occ) { inline Bitboard bishop_attacks_bb(Square s, Bitboard occ) {
const Magics& m = BMagics[s]; const Magics& m = BMagics[s];
return BAttacks[m.index + (((occ & m.mask) * m.mult) >> m.shift)]; return BAttacks[m.offset + (((occ & m.mask) * m.mult) >> m.shift)];
} }
#else // if !defined(IS_64BIT) #else // if !defined(IS_64BIT)