/*
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) 2008-2013 Marco Costalba, Joona Kiiski, 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 <algorithm>
#include <cstring>
#include <iostream>
#include "bitboard.h"
#include "bitcount.h"
+#include "misc.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];
+CACHE_LINE_ALIGNMENT
+
+Bitboard RMasks[SQUARE_NB];
+Bitboard RMagics[SQUARE_NB];
+Bitboard* RAttacks[SQUARE_NB];
+unsigned RShifts[SQUARE_NB];
+
+Bitboard BMasks[SQUARE_NB];
+Bitboard BMagics[SQUARE_NB];
+Bitboard* BAttacks[SQUARE_NB];
+unsigned BShifts[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 DistanceRingsBB[SQUARE_NB][8];
+Bitboard ForwardBB[COLOR_NB][SQUARE_NB];
+Bitboard PassedPawnMask[COLOR_NB][SQUARE_NB];
+Bitboard PawnAttackSpan[COLOR_NB][SQUARE_NB];
+Bitboard PseudoAttacks[PIECE_TYPE_NB][SQUARE_NB];
+
+int SquareDistance[SQUARE_NB][SQUARE_NB];
namespace {
- CACHE_LINE_ALIGNMENT
+ // De Bruijn sequences. See chessprogramming.wikispaces.com/BitScan
+ const uint64_t DeBruijn_64 = 0x3F79D71B4CB0A89ULL;
+ const uint32_t DeBruijn_32 = 0x783A9B23;
- int BSFTable[64];
- Bitboard RAttacksTable[0x19000];
- Bitboard BAttacksTable[0x1480];
+ CACHE_LINE_ALIGNMENT
- void init_sliding_attacks(Bitboard magic[], Bitboard* attack[], Bitboard attTable[],
- Bitboard mask[], int shift[], Square delta[]);
-}
+ int MS1BTable[256];
+ Square BSFTable[SQUARE_NB];
+ Bitboard RTable[0x19000]; // Storage space for rook attacks
+ Bitboard BTable[0x1480]; // Storage space for bishop attacks
+ typedef unsigned (Fn)(Square, Bitboard);
-/// print_bitboard() prints a bitboard in an easily readable format to the
-/// standard output. This is sometimes useful for debugging.
+ void init_magics(Bitboard table[], Bitboard* attacks[], Bitboard magics[],
+ Bitboard masks[], unsigned shifts[], Square deltas[], Fn index);
-void print_bitboard(Bitboard b) {
-
- 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 " : " ");
+ FORCE_INLINE unsigned bsf_index(Bitboard b) {
- std::cout << "|\n";
+ // Matt Taylor's folding for 32 bit systems, extended to 64 bits by Kim Walisch
+ b ^= (b - 1);
+ return Is64Bit ? (b * DeBruijn_64) >> 58
+ : ((unsigned(b) ^ unsigned(b >> 32)) * DeBruijn_32) >> 26;
}
- std::cout << "+---+---+---+---+---+---+---+---+" << std::endl;
}
+/// lsb()/msb() finds the least/most significant bit in a nonzero bitboard.
+/// pop_lsb() finds and clears the least significant bit in a nonzero bitboard.
-/// 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.
+#ifndef USE_BSFQ
-#if defined(IS_64BIT) && !defined(USE_BSFQ)
+Square lsb(Bitboard b) { return BSFTable[bsf_index(b)]; }
-Square first_1(Bitboard b) {
- return Square(BSFTable[((b & -b) * 0x218A392CD3D5DBFULL) >> 58]);
-}
+Square pop_lsb(Bitboard* b) {
-Square pop_1st_bit(Bitboard* b) {
Bitboard bb = *b;
- *b &= (*b - 1);
- return Square(BSFTable[((bb & -bb) * 0x218A392CD3D5DBFULL) >> 58]);
+ *b = bb & (bb - 1);
+ return BSFTable[bsf_index(bb)];
}
-#elif !defined(USE_BSFQ)
+Square msb(Bitboard b) {
-Square first_1(Bitboard b) {
- b ^= (b - 1);
- uint32_t fold = unsigned(b) ^ unsigned(b >> 32);
- return Square(BSFTable[(fold * 0x783A9B23) >> 26]);
-}
+ unsigned b32;
+ int result = 0;
-// 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;
-}
+ if (b > 0xFFFFFFFF)
+ {
+ b >>= 32;
+ result = 32;
+ }
-#endif // !defined(USE_BSFQ)
+ b32 = unsigned(b);
+ if (b32 > 0xFFFF)
+ {
+ b32 >>= 16;
+ result += 16;
+ }
-/// init_bitboards() initializes various bitboard arrays. It is called during
-/// program initialization.
+ if (b32 > 0xFF)
+ {
+ b32 >>= 8;
+ result += 8;
+ }
-void init_bitboards() {
+ return (Square)(result + MS1BTable[b32]);
+}
+
+#endif // ifndef USE_BSFQ
- for (Bitboard b = 0; b < 256; b++)
- BitCount8Bit[b] = (uint8_t)count_1s<CNT32_MAX15>(b);
- for (Square s1 = SQ_A1; s1 <= SQ_H8; s1++)
- for (Square s2 = SQ_A1; s2 <= SQ_H8; s2++)
- SquareDistance[s1][s2] = Max(file_distance(s1, s2), rank_distance(s1, s2));
+/// Bitboards::print() prints a bitboard in an easily readable format to the
+/// standard output. This is sometimes useful for debugging.
- SquaresByColorBB[DARK] = 0xAA55AA55AA55AA55ULL;
- SquaresByColorBB[LIGHT] = ~SquaresByColorBB[DARK];
+void Bitboards::print(Bitboard b) {
- for (Square s = SQ_A1; s <= SQ_H8; s++)
+ sync_cout;
+
+ for (Rank rank = RANK_8; rank >= RANK_1; --rank)
{
- SetMaskBB[s] = 1ULL << s;
- ClearMaskBB[s] = ~SetMaskBB[s];
+ std::cout << "+---+---+---+---+---+---+---+---+" << '\n';
+
+ for (File file = FILE_A; file <= FILE_H; ++file)
+ std::cout << "| " << (b & (file | rank) ? "X " : " ");
+
+ std::cout << "|\n";
}
+ std::cout << "+---+---+---+---+---+---+---+---+" << sync_endl;
+}
- ClearMaskBB[SQ_NONE] = ~EmptyBoardBB;
+
+/// Bitboards::init() initializes various bitboard arrays. It is called during
+/// program initialization.
+
+void Bitboards::init() {
+
+ for (int k = 0, i = 0; i < 8; ++i)
+ while (k < (2 << i))
+ MS1BTable[k++] = i;
+
+ for (int i = 0; i < 64; ++i)
+ BSFTable[bsf_index(1ULL << i)] = Square(i);
+
+ for (Square s = SQ_A1; s <= SQ_H8; ++s)
+ SquareBB[s] = 1ULL << s;
FileBB[FILE_A] = FileABB;
RankBB[RANK_1] = Rank1BB;
- for (int f = FILE_B; f <= FILE_H; f++)
+ for (int i = 1; i < 8; ++i)
{
- FileBB[f] = FileBB[f - 1] << 1;
- RankBB[f] = RankBB[f - 1] << 8;
+ FileBB[i] = FileBB[i - 1] << 1;
+ RankBB[i] = RankBB[i - 1] << 8;
}
- for (int f = FILE_A; f <= FILE_H; f++)
- {
- NeighboringFilesBB[f] = (f > FILE_A ? FileBB[f - 1] : 0) | (f < FILE_H ? FileBB[f + 1] : 0);
- ThisAndNeighboringFilesBB[f] = FileBB[f] | NeighboringFilesBB[f];
- }
+ 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 (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 (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++)
+ 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);
+ 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 (int i = 0; i < 64; i++)
- if (!CpuIs64Bit) // Matt Taylor's folding trick for 32 bit systems
+ for (Square s1 = SQ_A1; s1 <= SQ_H8; ++s1)
+ for (Square s2 = SQ_A1; s2 <= SQ_H8; ++s2)
{
- Bitboard b = 1ULL << i;
- b ^= b - 1;
- b ^= b >> 32;
- BSFTable[uint32_t(b * 0x783A9B23) >> 26] = i;
+ SquareDistance[s1][s2] = std::max(file_distance(s1, s2), rank_distance(s1, s2));
+ if (s1 != s2)
+ DistanceRingsBB[s1][SquareDistance[s1][s2] - 1] |= s2;
}
- 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++)
+ 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);
+ if (is_ok(to) && square_distance(s, to) < 3)
+ 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 };
+ Square RDeltas[] = { DELTA_N, DELTA_E, DELTA_S, DELTA_W };
+ Square BDeltas[] = { 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);
+ init_magics(RTable, RAttacks, RMagics, RMasks, RShifts, RDeltas, magic_index<ROOK>);
+ init_magics(BTable, BAttacks, BMagics, BMasks, BShifts, BDeltas, magic_index<BISHOP>);
- for (Square s = SQ_A1; s <= SQ_H8; s++)
+ 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);
+ PseudoAttacks[QUEEN][s] = PseudoAttacks[BISHOP][s] = attacks_bb<BISHOP>(s, 0);
+ PseudoAttacks[QUEEN][s] |= PseudoAttacks[ ROOK][s] = attacks_bb< ROOK>(s, 0);
}
- 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))
+ for (Square s1 = SQ_A1; s1 <= SQ_H8; ++s1)
+ for (Square s2 = SQ_A1; s2 <= SQ_H8; ++s2)
+ if (PseudoAttacks[QUEEN][s1] & s2)
{
- int f = file_distance(s1, s2);
- int r = rank_distance(s1, s2);
+ Square delta = (s2 - s1) / square_distance(s1, s2);
- Square d = (s2 - s1) / Max(f, r);
+ for (Square s = s1 + delta; s != s2; s += delta)
+ BetweenBB[s1][s2] |= s;
- for (Square s3 = s1 + d; s3 != s2; s3 += d)
- set_bit(&BetweenBB[s1][s2], s3);
+ PieceType pc = (PseudoAttacks[BISHOP][s1] & s2) ? BISHOP : ROOK;
+ LineBB[s1][s2] = (PseudoAttacks[pc][s1] & PseudoAttacks[pc][s2]) | s1 | s2;
}
}
namespace {
- Bitboard sliding_attacks(Square sq, Bitboard occupied, Square delta[]) {
+ Bitboard sliding_attack(Square deltas[], Square sq, Bitboard occupied) {
- Bitboard attacks = 0;
+ Bitboard attack = 0;
- for (int i = 0; i < 4; i++)
- {
- Square s = sq + delta[i];
-
- while (square_is_ok(s) && square_distance(s, s - delta[i]) == 1)
+ for (int i = 0; i < 4; ++i)
+ for (Square s = sq + deltas[i];
+ is_ok(s) && square_distance(s, s - deltas[i]) == 1;
+ s += deltas[i])
{
- set_bit(&attacks, s);
+ attack |= s;
- if (bit_is_set(occupied, s))
+ if (occupied & s)
break;
-
- s += delta[i];
}
- }
- return attacks;
+
+ return attack;
}
- Bitboard pick_magic(Bitboard mask, RKISS& rk, int booster) {
- Bitboard magic;
+ Bitboard pick_random(RKISS& rk, int booster) {
// 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;
- 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;
- }
+ Bitboard m = rk.rand<Bitboard>();
+ m = (m >> s1) | (m << (64 - s1));
+ m &= rk.rand<Bitboard>();
+ m = (m >> s2) | (m << (64 - s2));
+ return m & rk.rand<Bitboard>();
}
- void init_sliding_attacks(Bitboard magic[], Bitboard* attack[], Bitboard attTable[],
- Bitboard mask[], int shift[], Square delta[]) {
- const int MagicBoosters[][8] = { { 3191, 2184, 1310, 3618, 2091, 1308, 2452, 3996 },
- { 1059, 3608, 605, 3234, 3326, 38, 2029, 3043 } };
+ // 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) {
+
+ 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 i, size, booster;
+
+ // attacks[s] is a pointer to the beginning of the attacks table for square 's'
+ attacks[SQ_A1] = table;
- 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.
+ masks[s] = sliding_attack(deltas, s, 0) & ~edges;
+ shifts[s] = (Is64Bit ? 64 : 32) - popcount<Max15>(masks[s]);
+
+ // 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];
+ occupancy[size] = b;
+ reference[size++] = sliding_attack(deltas, s, b);
+ b = (b - masks[s]) & masks[s];
} while (b);
- offset += maxKey;
- booster = MagicBoosters[CpuIs64Bit][rank_of(s)];
+ // 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;
+
+ booster = MagicBoosters[Is64Bit][rank_of(s)];
- // Then find a possible magic and the corresponding attacks
+ // Find a magic for square 's' picking up an (almost) random number
+ // until we find the one that passes the verification test.
do {
- magic[s] = pick_magic(mask[s], rk, booster);
- memset(attack[s], 0, maxKey * sizeof(Bitboard));
+ do magics[s] = pick_random(rk, booster);
+ while (popcount<Max15>((magics[s] * masks[s]) >> 56) < 6);
- 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];
+ std::memset(attacks[s], 0, size * sizeof(Bitboard));
- if (!attack[s][index])
- attack[s][index] = reference[key];
+ // 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)
+ {
+ Bitboard& attack = attacks[s][index(s, occupancy[i])];
- else if (attack[s][index] != reference[key])
+ if (attack && attack != reference[i])
break;
+
+ assert(reference[i] != 0);
+
+ attack = reference[i];
}
- } while (key != maxKey);
+ } while (i != size);
}
}
}
projects / stockfish / blobdiff