/*
Stockfish, a UCI chess playing engine derived from Glaurung 2.1
- Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
- Copyright (C) 2008-2014 Marco Costalba, Joona Kiiski, Tord Romstad
+ Copyright (C) 2004-2023 The Stockfish developers (see AUTHORS file)
Stockfish is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
+#include "bitboard.h"
+
#include <algorithm>
-#include <cstring> // For std::memset
+#include <bitset>
+#include <initializer_list>
-#include "bitboard.h"
-#include "bitcount.h"
#include "misc.h"
-int SquareDistance[SQUARE_NB][SQUARE_NB];
+namespace Stockfish {
-Bitboard RookMasks [SQUARE_NB];
-Bitboard RookMagics [SQUARE_NB];
-Bitboard* RookAttacks[SQUARE_NB];
-unsigned RookShifts [SQUARE_NB];
+uint8_t PopCnt16[1 << 16];
+uint8_t SquareDistance[SQUARE_NB][SQUARE_NB];
-Bitboard BishopMasks [SQUARE_NB];
-Bitboard BishopMagics [SQUARE_NB];
-Bitboard* BishopAttacks[SQUARE_NB];
-unsigned BishopShifts [SQUARE_NB];
-
-Bitboard SquareBB[SQUARE_NB];
-Bitboard FileBB[FILE_NB];
-Bitboard RankBB[RANK_NB];
-Bitboard AdjacentFilesBB[FILE_NB];
-Bitboard InFrontBB[COLOR_NB][RANK_NB];
-Bitboard StepAttacksBB[PIECE_NB][SQUARE_NB];
-Bitboard BetweenBB[SQUARE_NB][SQUARE_NB];
Bitboard LineBB[SQUARE_NB][SQUARE_NB];
-Bitboard DistanceRingBB[SQUARE_NB][8];
-Bitboard ForwardBB[COLOR_NB][SQUARE_NB];
-Bitboard PassedPawnMask[COLOR_NB][SQUARE_NB];
-Bitboard PawnAttackSpan[COLOR_NB][SQUARE_NB];
+Bitboard BetweenBB[SQUARE_NB][SQUARE_NB];
Bitboard PseudoAttacks[PIECE_TYPE_NB][SQUARE_NB];
+Bitboard PawnAttacks[COLOR_NB][SQUARE_NB];
-namespace {
-
- // De Bruijn sequences. See chessprogramming.wikispaces.com/BitScan
- const uint64_t DeBruijn64 = 0x3F79D71B4CB0A89ULL;
- const uint32_t DeBruijn32 = 0x783A9B23;
-
- int MS1BTable[256]; // To implement software msb()
- Square BSFTable[SQUARE_NB]; // To implement software bitscan
- Bitboard RookTable[0x19000]; // To store rook attacks
- Bitboard BishopTable[0x1480]; // To store bishop attacks
+Magic RookMagics[SQUARE_NB];
+Magic BishopMagics[SQUARE_NB];
- typedef unsigned (Fn)(Square, Bitboard);
+namespace {
- void init_magics(Bitboard table[], Bitboard* attacks[], Bitboard magics[],
- Bitboard masks[], unsigned shifts[], Square deltas[], Fn index);
+Bitboard RookTable[0x19000]; // To store rook attacks
+Bitboard BishopTable[0x1480]; // To store bishop attacks
- // bsf_index() returns the index into BSFTable[] to look up the bitscan. Uses
- // Matt Taylor's folding for 32 bit case, extended to 64 bit by Kim Walisch.
+void init_magics(PieceType pt, Bitboard table[], Magic magics[]);
- FORCE_INLINE unsigned bsf_index(Bitboard b) {
- b ^= b - 1;
- return Is64Bit ? (b * DeBruijn64) >> 58
- : ((unsigned(b) ^ unsigned(b >> 32)) * DeBruijn32) >> 26;
- }
}
-#ifndef USE_BSFQ
-
-/// Software fall-back of lsb() and msb() for CPU lacking hardware support
-
-Square lsb(Bitboard b) {
- return BSFTable[bsf_index(b)];
+// Returns the bitboard of target square for the given step
+// from the given square. If the step is off the board, returns empty bitboard.
+inline Bitboard safe_destination(Square s, int step) {
+ Square to = Square(s + step);
+ return is_ok(to) && distance(s, to) <= 2 ? square_bb(to) : Bitboard(0);
}
-Square msb(Bitboard b) {
- unsigned b32;
- int result = 0;
+// Returns an ASCII representation of a bitboard suitable
+// to be printed to standard output. Useful for debugging.
+std::string Bitboards::pretty(Bitboard b) {
- if (b > 0xFFFFFFFF)
- {
- b >>= 32;
- result = 32;
- }
+ std::string s = "+---+---+---+---+---+---+---+---+\n";
- b32 = unsigned(b);
-
- if (b32 > 0xFFFF)
- {
- b32 >>= 16;
- result += 16;
- }
+ for (Rank r = RANK_8; r >= RANK_1; --r)
+ {
+ for (File f = FILE_A; f <= FILE_H; ++f)
+ s += b & make_square(f, r) ? "| X " : "| ";
- if (b32 > 0xFF)
- {
- b32 >>= 8;
- result += 8;
- }
+ s += "| " + std::to_string(1 + r) + "\n+---+---+---+---+---+---+---+---+\n";
+ }
+ s += " a b c d e f g h\n";
- return Square(result + MS1BTable[b32]);
+ return s;
}
-#endif // ifndef USE_BSFQ
+// Initializes various bitboard tables. It is called at
+// startup and relies on global objects to be already zero-initialized.
+void Bitboards::init() {
-/// Bitboards::pretty() returns an ASCII representation of a bitboard suitable
-/// to be printed to standard output. Useful for debugging.
-
-const std::string Bitboards::pretty(Bitboard b) {
-
- std::string s = "+---+---+---+---+---+---+---+---+\n";
+ for (unsigned i = 0; i < (1 << 16); ++i)
+ PopCnt16[i] = uint8_t(std::bitset<16>(i).count());
- for (Rank r = RANK_8; r >= RANK_1; --r)
- {
- for (File f = FILE_A; f <= FILE_H; ++f)
- s.append(b & make_square(f, r) ? "| X " : "| ");
+ for (Square s1 = SQ_A1; s1 <= SQ_H8; ++s1)
+ for (Square s2 = SQ_A1; s2 <= SQ_H8; ++s2)
+ SquareDistance[s1][s2] = std::max(distance<File>(s1, s2), distance<Rank>(s1, s2));
- s.append("|\n+---+---+---+---+---+---+---+---+\n");
- }
+ init_magics(ROOK, RookTable, RookMagics);
+ init_magics(BISHOP, BishopTable, BishopMagics);
- return s;
-}
+ for (Square s1 = SQ_A1; s1 <= SQ_H8; ++s1)
+ {
+ PawnAttacks[WHITE][s1] = pawn_attacks_bb<WHITE>(square_bb(s1));
+ PawnAttacks[BLACK][s1] = pawn_attacks_bb<BLACK>(square_bb(s1));
+ for (int step : {-9, -8, -7, -1, 1, 7, 8, 9})
+ PseudoAttacks[KING][s1] |= safe_destination(s1, step);
-/// Bitboards::init() initializes various bitboard tables. It is called at
-/// startup and relies on global objects to be already zero-initialized.
+ for (int step : {-17, -15, -10, -6, 6, 10, 15, 17})
+ PseudoAttacks[KNIGHT][s1] |= safe_destination(s1, step);
-void Bitboards::init() {
+ PseudoAttacks[QUEEN][s1] = PseudoAttacks[BISHOP][s1] = attacks_bb<BISHOP>(s1, 0);
+ PseudoAttacks[QUEEN][s1] |= PseudoAttacks[ROOK][s1] = attacks_bb<ROOK>(s1, 0);
- for (Square s = SQ_A1; s <= SQ_H8; ++s)
- {
- SquareBB[s] = 1ULL << s;
- BSFTable[bsf_index(SquareBB[s])] = s;
- }
-
- for (Bitboard b = 1; b < 256; ++b)
- MS1BTable[b] = more_than_one(b) ? MS1BTable[b - 1] : lsb(b);
-
- for (File f = FILE_A; f <= FILE_H; ++f)
- FileBB[f] = f > FILE_A ? FileBB[f - 1] << 1 : FileABB;
-
- for (Rank r = RANK_1; r <= RANK_8; ++r)
- RankBB[r] = r > RANK_1 ? RankBB[r - 1] << 8 : Rank1BB;
-
- for (File f = FILE_A; f <= FILE_H; ++f)
- AdjacentFilesBB[f] = (f > FILE_A ? FileBB[f - 1] : 0) | (f < FILE_H ? FileBB[f + 1] : 0);
-
- for (Rank r = RANK_1; r < RANK_8; ++r)
- InFrontBB[WHITE][r] = ~(InFrontBB[BLACK][r + 1] = InFrontBB[BLACK][r] | RankBB[r]);
-
- for (Color c = WHITE; c <= BLACK; ++c)
- for (Square s = SQ_A1; s <= SQ_H8; ++s)
- {
- ForwardBB[c][s] = InFrontBB[c][rank_of(s)] & FileBB[file_of(s)];
- PawnAttackSpan[c][s] = InFrontBB[c][rank_of(s)] & AdjacentFilesBB[file_of(s)];
- PassedPawnMask[c][s] = ForwardBB[c][s] | PawnAttackSpan[c][s];
- }
-
- for (Square s1 = SQ_A1; s1 <= SQ_H8; ++s1)
- for (Square s2 = SQ_A1; s2 <= SQ_H8; ++s2)
- if (s1 != s2)
- {
- SquareDistance[s1][s2] = std::max(distance<File>(s1, s2), distance<Rank>(s1, s2));
- DistanceRingBB[s1][SquareDistance[s1][s2] - 1] |= s2;
- }
-
- int steps[][9] = { {}, { 7, 9 }, { 17, 15, 10, 6, -6, -10, -15, -17 },
- {}, {}, {}, { 9, 7, -7, -9, 8, 1, -1, -8 } };
-
- for (Color c = WHITE; c <= BLACK; ++c)
- for (PieceType pt = PAWN; pt <= KING; ++pt)
- for (Square s = SQ_A1; s <= SQ_H8; ++s)
- for (int i = 0; steps[pt][i]; ++i)
- {
- Square to = s + Square(c == WHITE ? steps[pt][i] : -steps[pt][i]);
-
- if (is_ok(to) && distance(s, to) < 3)
- StepAttacksBB[make_piece(c, pt)][s] |= to;
- }
-
- Square RookDeltas[] = { DELTA_N, DELTA_E, DELTA_S, DELTA_W };
- Square BishopDeltas[] = { DELTA_NE, DELTA_SE, DELTA_SW, DELTA_NW };
-
- init_magics(RookTable, RookAttacks, RookMagics, RookMasks, RookShifts, RookDeltas, magic_index<ROOK>);
- init_magics(BishopTable, BishopAttacks, BishopMagics, BishopMasks, BishopShifts, BishopDeltas, magic_index<BISHOP>);
-
- for (Square s1 = SQ_A1; s1 <= SQ_H8; ++s1)
- {
- PseudoAttacks[QUEEN][s1] = PseudoAttacks[BISHOP][s1] = attacks_bb<BISHOP>(s1, 0);
- PseudoAttacks[QUEEN][s1] |= PseudoAttacks[ ROOK][s1] = attacks_bb< ROOK>(s1, 0);
-
- for (Square s2 = SQ_A1; s2 <= SQ_H8; ++s2)
- {
- Piece pc = (PseudoAttacks[BISHOP][s1] & s2) ? W_BISHOP :
- (PseudoAttacks[ROOK][s1] & s2) ? W_ROOK : NO_PIECE;
-
- if (pc == NO_PIECE)
- continue;
-
- LineBB[s1][s2] = (attacks_bb(pc, s1, 0) & attacks_bb(pc, s2, 0)) | s1 | s2;
- BetweenBB[s1][s2] = attacks_bb(pc, s1, SquareBB[s2]) & attacks_bb(pc, s2, SquareBB[s1]);
- }
- }
+ for (PieceType pt : {BISHOP, ROOK})
+ for (Square s2 = SQ_A1; s2 <= SQ_H8; ++s2)
+ {
+ if (PseudoAttacks[pt][s1] & s2)
+ {
+ LineBB[s1][s2] = (attacks_bb(pt, s1, 0) & attacks_bb(pt, s2, 0)) | s1 | s2;
+ BetweenBB[s1][s2] =
+ (attacks_bb(pt, s1, square_bb(s2)) & attacks_bb(pt, s2, square_bb(s1)));
+ }
+ BetweenBB[s1][s2] |= s2;
+ }
+ }
}
-
namespace {
- Bitboard sliding_attack(Square deltas[], Square sq, Bitboard occupied) {
-
- Bitboard attack = 0;
+Bitboard sliding_attack(PieceType pt, Square sq, Bitboard occupied) {
- for (int i = 0; i < 4; ++i)
- for (Square s = sq + deltas[i];
- is_ok(s) && distance(s, s - deltas[i]) == 1;
- s += deltas[i])
- {
- attack |= s;
-
- if (occupied & s)
- break;
- }
+ Bitboard attacks = 0;
+ Direction RookDirections[4] = {NORTH, SOUTH, EAST, WEST};
+ Direction BishopDirections[4] = {NORTH_EAST, SOUTH_EAST, SOUTH_WEST, NORTH_WEST};
- return attack;
- }
+ for (Direction d : (pt == ROOK ? RookDirections : BishopDirections))
+ {
+ Square s = sq;
+ while (safe_destination(s, d) && !(occupied & s))
+ attacks |= (s += d);
+ }
+ return attacks;
+}
- // init_magics() computes all rook and bishop attacks at startup. Magic
- // bitboards are used to look up attacks of sliding pieces. As a reference see
- // chessprogramming.wikispaces.com/Magic+Bitboards. In particular, here we
- // use the so called "fancy" approach.
- void init_magics(Bitboard table[], Bitboard* attacks[], Bitboard magics[],
- Bitboard masks[], unsigned shifts[], Square deltas[], Fn index) {
+// Computes all rook and bishop attacks at startup. Magic
+// bitboards are used to look up attacks of sliding pieces. As a reference see
+// www.chessprogramming.org/Magic_Bitboards. In particular, here we use the so
+// called "fancy" approach.
+void init_magics(PieceType pt, Bitboard table[], Magic magics[]) {
- int seeds[][RANK_NB] = { { 8977, 44560, 54343, 38998, 5731, 95205, 104912, 17020 },
- { 728, 10316, 55013, 32803, 12281, 15100, 16645, 255 } };
+ // Optimal PRNG seeds to pick the correct magics in the shortest time
+ int seeds[][RANK_NB] = {{8977, 44560, 54343, 38998, 5731, 95205, 104912, 17020},
+ {728, 10316, 55013, 32803, 12281, 15100, 16645, 255}};
Bitboard occupancy[4096], reference[4096], edges, b;
- int i, size;
-
- // attacks[s] is a pointer to the beginning of the attacks table for square 's'
- attacks[SQ_A1] = table;
+ int epoch[4096] = {}, cnt = 0, size = 0;
for (Square s = SQ_A1; s <= SQ_H8; ++s)
{
// all the attacks for each possible subset of the mask and so is 2 power
// the number of 1s of the mask. Hence we deduce the size of the shift to
// apply to the 64 or 32 bits word to get the index.
- masks[s] = sliding_attack(deltas, s, 0) & ~edges;
- shifts[s] = (Is64Bit ? 64 : 32) - popcount<Max15>(masks[s]);
+ Magic& m = magics[s];
+ m.mask = sliding_attack(pt, s, 0) & ~edges;
+ m.shift = (Is64Bit ? 64 : 32) - popcount(m.mask);
+
+ // Set the offset for the attacks table of the square. We have individual
+ // table sizes for each square with "Fancy Magic Bitboards".
+ m.attacks = s == SQ_A1 ? table : magics[s - 1].attacks + size;
// Use Carry-Rippler trick to enumerate all subsets of masks[s] and
// store the corresponding sliding attack bitboard in reference[].
b = size = 0;
- do {
+ do
+ {
occupancy[size] = b;
- reference[size] = sliding_attack(deltas, s, b);
+ reference[size] = sliding_attack(pt, s, b);
if (HasPext)
- attacks[s][_pext_u64(b, masks[s])] = reference[size];
+ m.attacks[pext(b, m.mask)] = reference[size];
size++;
- b = (b - masks[s]) & masks[s];
+ b = (b - m.mask) & m.mask;
} while (b);
- // Set the offset for the table of the next square. We have individual
- // table sizes for each square with "Fancy Magic Bitboards".
- if (s < SQ_H8)
- attacks[s + 1] = attacks[s] + size;
-
if (HasPext)
continue;
// Find a magic for square 's' picking up an (almost) random number
// until we find the one that passes the verification test.
- do {
- do
- magics[s] = rng.sparse_rand<Bitboard>();
- while (popcount<Max15>((magics[s] * masks[s]) >> 56) < 6);
-
- std::memset(attacks[s], 0, size * sizeof(Bitboard));
+ for (int i = 0; i < size;)
+ {
+ for (m.magic = 0; popcount((m.magic * m.mask) >> 56) < 6;)
+ m.magic = rng.sparse_rand<Bitboard>();
// A good magic must map every possible occupancy to an index that
// looks up the correct sliding attack in the attacks[s] database.
// Note that we build up the database for square 's' as a side
- // effect of verifying the magic.
- for (i = 0; i < size; ++i)
+ // effect of verifying the magic. Keep track of the attempt count
+ // and save it in epoch[], little speed-up trick to avoid resetting
+ // m.attacks[] after every failed attempt.
+ for (++cnt, i = 0; i < size; ++i)
{
- Bitboard& attack = attacks[s][index(s, occupancy[i])];
-
- if (attack && attack != reference[i])
+ unsigned idx = m.index(occupancy[i]);
+
+ if (epoch[idx] < cnt)
+ {
+ epoch[idx] = cnt;
+ m.attacks[idx] = reference[i];
+ }
+ else if (m.attacks[idx] != reference[i])
break;
-
- assert(reference[i]);
-
- attack = reference[i];
}
- } while (i < size);
+ }
}
- }
}
+}
+
+} // namespace Stockfish
projects / stockfish / blobdiff