/*
Stockfish, a UCI chess playing engine derived from Glaurung 2.1
Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
- Copyright (C) 2008-2010 Marco Costalba, Joona Kiiski, Tord Romstad
+ Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad
+ Copyright (C) 2015-2020 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
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 <cstring>
-#include <iostream>
#include <algorithm>
+#include <bitset>
#include "bitboard.h"
-#include "bitcount.h"
-#include "rkiss.h"
-
-// Global bitboards definitions with static storage duration are
-// automatically set to zero before enter main().
-Bitboard RMask[64];
-Bitboard RMult[64];
-Bitboard* RAttacks[64];
-int RShift[64];
-
-Bitboard BMask[64];
-Bitboard BMult[64];
-Bitboard* BAttacks[64];
-int BShift[64];
-
-Bitboard SetMaskBB[65];
-Bitboard ClearMaskBB[65];
-
-Bitboard SquaresByColorBB[2];
-Bitboard FileBB[8];
-Bitboard RankBB[8];
-Bitboard NeighboringFilesBB[8];
-Bitboard ThisAndNeighboringFilesBB[8];
-Bitboard InFrontBB[2][8];
-Bitboard StepAttacksBB[16][64];
-Bitboard BetweenBB[64][64];
-Bitboard SquaresInFrontMask[2][64];
-Bitboard PassedPawnMask[2][64];
-Bitboard AttackSpanMask[2][64];
-
-Bitboard BishopPseudoAttacks[64];
-Bitboard RookPseudoAttacks[64];
-Bitboard QueenPseudoAttacks[64];
-
-uint8_t BitCount8Bit[256];
-int SquareDistance[64][64];
+#include "misc.h"
-namespace {
-
- CACHE_LINE_ALIGNMENT
-
- int BSFTable[64];
- Bitboard RAttacksTable[0x19000];
- Bitboard BAttacksTable[0x1480];
+uint8_t PopCnt16[1 << 16];
+uint8_t SquareDistance[SQUARE_NB][SQUARE_NB];
- void init_sliding_attacks(Bitboard magic[], Bitboard* attack[], Bitboard attTable[],
- Bitboard mask[], int shift[], Square delta[]);
-}
+Bitboard SquareBB[SQUARE_NB];
+Bitboard LineBB[SQUARE_NB][SQUARE_NB];
+Bitboard PseudoAttacks[PIECE_TYPE_NB][SQUARE_NB];
+Bitboard PawnAttacks[COLOR_NB][SQUARE_NB];
+Magic RookMagics[SQUARE_NB];
+Magic BishopMagics[SQUARE_NB];
-/// print_bitboard() prints a bitboard in an easily readable format to the
-/// standard output. This is sometimes useful for debugging.
+namespace {
-void print_bitboard(Bitboard b) {
+ Bitboard RookTable[0x19000]; // To store rook attacks
+ Bitboard BishopTable[0x1480]; // To store bishop attacks
- for (Rank r = RANK_8; r >= RANK_1; r--)
- {
- std::cout << "+---+---+---+---+---+---+---+---+" << '\n';
- for (File f = FILE_A; f <= FILE_H; f++)
- std::cout << "| " << (bit_is_set(b, make_square(f, r)) ? "X " : " ");
-
- std::cout << "|\n";
- }
- std::cout << "+---+---+---+---+---+---+---+---+" << std::endl;
+ void init_magics(Bitboard table[], Magic magics[], Direction directions[]);
}
-/// first_1() finds the least significant nonzero bit in a nonzero bitboard.
-/// pop_1st_bit() finds and clears the least significant nonzero bit in a
-/// nonzero bitboard.
+/// Bitboards::pretty() returns an ASCII representation of a bitboard suitable
+/// to be printed to standard output. Useful for debugging.
-#if defined(IS_64BIT) && !defined(USE_BSFQ)
+const std::string Bitboards::pretty(Bitboard b) {
-Square first_1(Bitboard b) {
- return Square(BSFTable[((b & -b) * 0x218A392CD3D5DBFULL) >> 58]);
-}
-
-Square pop_1st_bit(Bitboard* b) {
- Bitboard bb = *b;
- *b &= (*b - 1);
- return Square(BSFTable[((bb & -bb) * 0x218A392CD3D5DBFULL) >> 58]);
-}
+ std::string s = "+---+---+---+---+---+---+---+---+\n";
-#elif !defined(USE_BSFQ)
+ 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 " : "| ";
-Square first_1(Bitboard b) {
- b ^= (b - 1);
- uint32_t fold = unsigned(b) ^ unsigned(b >> 32);
- return Square(BSFTable[(fold * 0x783A9B23) >> 26]);
-}
+ s += "|\n+---+---+---+---+---+---+---+---+\n";
+ }
-// Use type-punning
-union b_union {
-
- Bitboard b;
- struct {
-#if defined (BIGENDIAN)
- uint32_t h;
- uint32_t l;
-#else
- uint32_t l;
- uint32_t h;
-#endif
- } dw;
-};
-
-Square pop_1st_bit(Bitboard* bb) {
-
- b_union u;
- Square ret;
-
- u.b = *bb;
-
- if (u.dw.l)
- {
- ret = Square(BSFTable[((u.dw.l ^ (u.dw.l - 1)) * 0x783A9B23) >> 26]);
- u.dw.l &= (u.dw.l - 1);
- *bb = u.b;
- return ret;
- }
- ret = Square(BSFTable[((~(u.dw.h ^ (u.dw.h - 1))) * 0x783A9B23) >> 26]);
- u.dw.h &= (u.dw.h - 1);
- *bb = u.b;
- return ret;
+ return s;
}
-#endif // !defined(USE_BSFQ)
+/// Bitboards::init() initializes various bitboard tables. It is called at
+/// startup and relies on global objects to be already zero-initialized.
-/// init_bitboards() initializes various bitboard arrays. It is called during
-/// program initialization.
+void Bitboards::init() {
-void init_bitboards() {
+ for (unsigned i = 0; i < (1 << 16); ++i)
+ PopCnt16[i] = std::bitset<16>(i).count();
- for (Bitboard b = 0; b < 256; b++)
- BitCount8Bit[b] = (uint8_t)count_1s<CNT32_MAX15>(b);
+ for (Square s = SQ_A1; s <= SQ_H8; ++s)
+ SquareBB[s] = (1ULL << s);
- for (Square s1 = SQ_A1; s1 <= SQ_H8; s1++)
- for (Square s2 = SQ_A1; s2 <= SQ_H8; s2++)
- SquareDistance[s1][s2] = std::max(file_distance(s1, s2), rank_distance(s1, s2));
+ 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));
- SquaresByColorBB[DARK] = 0xAA55AA55AA55AA55ULL;
- SquaresByColorBB[LIGHT] = ~SquaresByColorBB[DARK];
-
- for (Square s = SQ_A1; s <= SQ_H8; s++)
+ for (Square s = SQ_A1; s <= SQ_H8; ++s)
{
- SetMaskBB[s] = 1ULL << s;
- ClearMaskBB[s] = ~SetMaskBB[s];
+ PawnAttacks[WHITE][s] = pawn_attacks_bb<WHITE>(square_bb(s));
+ PawnAttacks[BLACK][s] = pawn_attacks_bb<BLACK>(square_bb(s));
}
- ClearMaskBB[SQ_NONE] = ~EmptyBoardBB;
-
- FileBB[FILE_A] = FileABB;
- RankBB[RANK_1] = Rank1BB;
-
- for (int f = FILE_B; f <= FILE_H; f++)
+ // Helper returning the target bitboard of a step from a square
+ auto landing_square_bb = [&](Square s, int step)
{
- FileBB[f] = FileBB[f - 1] << 1;
- RankBB[f] = RankBB[f - 1] << 8;
- }
+ Square to = Square(s + step);
+ return is_ok(to) && distance(s, to) <= 2 ? square_bb(to) : Bitboard(0);
+ };
- for (int f = FILE_A; f <= FILE_H; f++)
+ for (Square s = SQ_A1; s <= SQ_H8; ++s)
{
- NeighboringFilesBB[f] = (f > FILE_A ? FileBB[f - 1] : 0) | (f < FILE_H ? FileBB[f + 1] : 0);
- ThisAndNeighboringFilesBB[f] = FileBB[f] | NeighboringFilesBB[f];
- }
+ for (int step : {-9, -8, -7, -1, 1, 7, 8, 9} )
+ PseudoAttacks[KING][s] |= landing_square_bb(s, step);
- for (int rw = RANK_7, rb = RANK_2; rw >= RANK_1; rw--, rb++)
- {
- InFrontBB[WHITE][rw] = InFrontBB[WHITE][rw + 1] | RankBB[rw + 1];
- InFrontBB[BLACK][rb] = InFrontBB[BLACK][rb - 1] | RankBB[rb - 1];
+ for (int step : {-17, -15, -10, -6, 6, 10, 15, 17} )
+ PseudoAttacks[KNIGHT][s] |= landing_square_bb(s, step);
}
- for (Color c = WHITE; c <= BLACK; c++)
- for (Square s = SQ_A1; s <= SQ_H8; s++)
- {
- SquaresInFrontMask[c][s] = in_front_bb(c, s) & file_bb(s);
- PassedPawnMask[c][s] = in_front_bb(c, s) & this_and_neighboring_files_bb(s);
- AttackSpanMask[c][s] = in_front_bb(c, s) & neighboring_files_bb(s);
- }
-
- for (int i = 0; i < 64; i++)
- if (!CpuIs64Bit) // Matt Taylor's folding trick for 32 bit systems
- {
- Bitboard b = 1ULL << i;
- b ^= b - 1;
- b ^= b >> 32;
- BSFTable[uint32_t(b * 0x783A9B23) >> 26] = i;
- }
- else
- BSFTable[((1ULL << i) * 0x218A392CD3D5DBFULL) >> 58] = i;
-
- 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 k = 0; steps[pt][k]; k++)
- {
- Square to = s + Square(c == WHITE ? steps[pt][k] : -steps[pt][k]);
-
- if (square_is_ok(to) && square_distance(s, to) < 3)
- set_bit(&StepAttacksBB[make_piece(c, pt)][s], to);
- }
-
- Square RDelta[] = { DELTA_N, DELTA_E, DELTA_S, DELTA_W };
- Square BDelta[] = { DELTA_NE, DELTA_SE, DELTA_SW, DELTA_NW };
-
- init_sliding_attacks(BMult, BAttacks, BAttacksTable, BMask, BShift, BDelta);
- init_sliding_attacks(RMult, RAttacks, RAttacksTable, RMask, RShift, RDelta);
-
- for (Square s = SQ_A1; s <= SQ_H8; s++)
- {
- BishopPseudoAttacks[s] = bishop_attacks_bb(s, EmptyBoardBB);
- RookPseudoAttacks[s] = rook_attacks_bb(s, EmptyBoardBB);
- QueenPseudoAttacks[s] = queen_attacks_bb(s, EmptyBoardBB);
- }
+ Direction RookDirections[] = { NORTH, EAST, SOUTH, WEST };
+ Direction BishopDirections[] = { NORTH_EAST, SOUTH_EAST, SOUTH_WEST, NORTH_WEST };
- for (Square s1 = SQ_A1; s1 <= SQ_H8; s1++)
- for (Square s2 = SQ_A1; s2 <= SQ_H8; s2++)
- if (bit_is_set(QueenPseudoAttacks[s1], s2))
- {
- int f = file_distance(s1, s2);
- int r = rank_distance(s1, s2);
+ init_magics(RookTable, RookMagics, RookDirections);
+ init_magics(BishopTable, BishopMagics, BishopDirections);
- Square d = (s2 - s1) / std::max(f, r);
+ 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 s3 = s1 + d; s3 != s2; s3 += d)
- set_bit(&BetweenBB[s1][s2], s3);
- }
+ 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;
+ }
}
namespace {
- Bitboard sliding_attacks(Square sq, Bitboard occupied, Square delta[]) {
+ Bitboard sliding_attack(Direction directions[], Square sq, Bitboard occupied) {
- Bitboard attacks = 0;
-
- for (int i = 0; i < 4; i++)
- {
- Square s = sq + delta[i];
+ Bitboard attack = 0;
- while (square_is_ok(s) && square_distance(s, s - delta[i]) == 1)
+ for (int i = 0; i < 4; ++i)
+ for (Square s = sq + directions[i];
+ is_ok(s) && distance(s, s - directions[i]) == 1;
+ s += directions[i])
{
- set_bit(&attacks, s);
+ attack |= s;
- if (bit_is_set(occupied, s))
+ if (occupied & s)
break;
-
- s += delta[i];
}
- }
- return attacks;
- }
- Bitboard pick_magic(Bitboard mask, RKISS& rk, int booster) {
+ return attack;
+ }
- Bitboard magic;
- // Values s1 and s2 are used to rotate the candidate magic of a
- // quantity known to be the optimal to quickly find the magics.
- int s1 = booster & 63, s2 = (booster >> 6) & 63;
+ // 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
+ // www.chessprogramming.org/Magic_Bitboards. In particular, here we use the so
+ // called "fancy" approach.
- while (true)
- {
- magic = rk.rand<Bitboard>();
- magic = (magic >> s1) | (magic << (64 - s1));
- magic &= rk.rand<Bitboard>();
- magic = (magic >> s2) | (magic << (64 - s2));
- magic &= rk.rand<Bitboard>();
-
- if (BitCount8Bit[(mask * magic) >> 56] >= 6)
- return magic;
- }
- }
+ void init_magics(Bitboard table[], Magic magics[], Direction directions[]) {
- void init_sliding_attacks(Bitboard magic[], Bitboard* attack[], Bitboard attTable[],
- Bitboard mask[], int shift[], Square delta[]) {
+ // 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 } };
- const int MagicBoosters[][8] = { { 3191, 2184, 1310, 3618, 2091, 1308, 2452, 3996 },
- { 1059, 3608, 605, 3234, 3326, 38, 2029, 3043 } };
- RKISS rk;
Bitboard occupancy[4096], reference[4096], edges, b;
- int key, maxKey, index, booster, offset = 0;
+ int epoch[4096] = {}, cnt = 0, size = 0;
- for (Square s = SQ_A1; s <= SQ_H8; s++)
+ for (Square s = SQ_A1; s <= SQ_H8; ++s)
{
+ // Board edges are not considered in the relevant occupancies
edges = ((Rank1BB | Rank8BB) & ~rank_bb(s)) | ((FileABB | FileHBB) & ~file_bb(s));
- attack[s] = &attTable[offset];
- mask[s] = sliding_attacks(s, EmptyBoardBB, delta) & ~edges;
- shift[s] = (CpuIs64Bit ? 64 : 32) - count_1s<CNT32_MAX15>(mask[s]);
-
- // Use Carry-Rippler trick to enumerate all subsets of mask[s]
- b = maxKey = 0;
+ // Given a square 's', the mask is the bitboard of sliding attacks from
+ // 's' computed on an empty board. The index must be big enough to contain
+ // 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.
+ Magic& m = magics[s];
+ m.mask = sliding_attack(directions, 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 {
- occupancy[maxKey] = b;
- reference[maxKey++] = sliding_attacks(s, b, delta);
- b = (b - mask[s]) & mask[s];
- } while (b);
+ occupancy[size] = b;
+ reference[size] = sliding_attack(directions, s, b);
- offset += maxKey;
- booster = MagicBoosters[CpuIs64Bit][rank_of(s)];
+ if (HasPext)
+ m.attacks[pext(b, m.mask)] = reference[size];
- // Then find a possible magic and the corresponding attacks
- do {
- magic[s] = pick_magic(mask[s], rk, booster);
- memset(attack[s], 0, maxKey * sizeof(Bitboard));
+ size++;
+ b = (b - m.mask) & m.mask;
+ } while (b);
- for (key = 0; key < maxKey; key++)
- {
- index = CpuIs64Bit ? unsigned((occupancy[key] * magic[s]) >> shift[s])
- : unsigned(occupancy[key] * magic[s] ^ (occupancy[key] >> 32) * (magic[s] >> 32)) >> shift[s];
+ if (HasPext)
+ continue;
- if (!attack[s][index])
- attack[s][index] = reference[key];
+ PRNG rng(seeds[Is64Bit][rank_of(s)]);
- else if (attack[s][index] != reference[key])
+ // Find a magic for square 's' picking up an (almost) random number
+ // until we find the one that passes the verification test.
+ 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. 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)
+ {
+ 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;
}
- } while (key != maxKey);
+ }
}
}
}