X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fbitboard.cpp;h=758796bed0bf4ac0122174ca0cad1a065b9852bb;hp=8c70a8e27b10820e27f288f28febfced33f91657;hb=90890844ade67d8081a5284700cc2ef3ebdbb62d;hpb=d632e77058114e87a6d7c02fda3a40768546e1d6 diff --git a/src/bitboard.cpp b/src/bitboard.cpp index 8c70a8e2..758796be 100644 --- a/src/bitboard.cpp +++ b/src/bitboard.cpp @@ -19,6 +19,7 @@ #include #include +#include #include "bitboard.h" #include "bitcount.h" @@ -26,15 +27,15 @@ // Global bitboards definitions with static storage duration are // automatically set to zero before enter main(). -Bitboard RMask[64]; -Bitboard RMult[64]; +Bitboard RMasks[64]; +Bitboard RMagics[64]; Bitboard* RAttacks[64]; -int RShift[64]; +int RShifts[64]; -Bitboard BMask[64]; -Bitboard BMult[64]; +Bitboard BMasks[64]; +Bitboard BMagics[64]; Bitboard* BAttacks[64]; -int BShift[64]; +int BShifts[64]; Bitboard SetMaskBB[65]; Bitboard ClearMaskBB[65]; @@ -56,17 +57,18 @@ Bitboard RookPseudoAttacks[64]; Bitboard QueenPseudoAttacks[64]; uint8_t BitCount8Bit[256]; +int SquareDistance[64][64]; namespace { CACHE_LINE_ALIGNMENT int BSFTable[64]; - Bitboard RAttacksTable[0x19000]; - Bitboard BAttacksTable[0x1480]; + Bitboard RookTable[0x19000]; // Storage space for rook attacks + Bitboard BishopTable[0x1480]; // Storage space for bishop attacks - void do_magics(Bitboard magic[], Bitboard* attack[], Bitboard attTabl[], - Bitboard mask[], int shift[], Square deltas[]); + void init_magic_bitboards(Bitboard* attacks[], Bitboard magics[], + Bitboard masks[], int shifts[], Square deltas[]); } @@ -79,7 +81,7 @@ void print_bitboard(Bitboard b) { { 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 << "| " << (bit_is_set(b, make_square(f, r)) ? "X " : " "); std::cout << "|\n"; } @@ -154,12 +156,19 @@ Square pop_1st_bit(Bitboard* bb) { void init_bitboards() { + for (Bitboard b = 0; b < 256; b++) + BitCount8Bit[b] = (uint8_t)count_1s(b); + + 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)); + SquaresByColorBB[DARK] = 0xAA55AA55AA55AA55ULL; SquaresByColorBB[LIGHT] = ~SquaresByColorBB[DARK]; for (Square s = SQ_A1; s <= SQ_H8; s++) { - SetMaskBB[s] = (1ULL << s); + SetMaskBB[s] = 1ULL << s; ClearMaskBB[s] = ~SetMaskBB[s]; } @@ -194,10 +203,7 @@ void init_bitboards() { AttackSpanMask[c][s] = in_front_bb(c, s) & neighboring_files_bb(s); } - for (Bitboard b = 0; b < 256; b++) - BitCount8Bit[b] = (uint8_t)count_1s(b); - - for (int i = 1; i < 64; i++) + for (int i = 0; i < 64; i++) if (!CpuIs64Bit) // Matt Taylor's folding trick for 32 bit systems { Bitboard b = 1ULL << i; @@ -208,13 +214,12 @@ void init_bitboards() { else BSFTable[((1ULL << i) * 0x218A392CD3D5DBFULL) >> 58] = i; - int steps[][9] = { - {0}, {7,9,0}, {17,15,10,6,-6,-10,-15,-17,0}, {0}, {0}, {0}, {9,7,-7,-9,8,1,-1,-8,0} - }; + 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 (Square s = SQ_A1; s <= SQ_H8; s++) - for (PieceType pt = PAWN; pt <= KING; pt++) + 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]); @@ -226,8 +231,11 @@ void init_bitboards() { Square RDeltas[] = { DELTA_N, DELTA_E, DELTA_S, DELTA_W }; Square BDeltas[] = { DELTA_NE, DELTA_SE, DELTA_SW, DELTA_NW }; - do_magics(BMult, BAttacks, BAttacksTable, BMask, BShift, BDeltas); - do_magics(RMult, RAttacks, RAttacksTable, RMask, RShift, RDeltas); + RAttacks[0] = RookTable; + BAttacks[0] = BishopTable; + + init_magic_bitboards(RAttacks, RMagics, RMasks, RShifts, RDeltas); + init_magic_bitboards(BAttacks, BMagics, BMasks, BShifts, BDeltas); for (Square s = SQ_A1; s <= SQ_H8; s++) { @@ -243,7 +251,7 @@ void init_bitboards() { int f = file_distance(s1, s2); int r = rank_distance(s1, s2); - Square d = (s2 - s1) / Max(f, r); + Square d = (s2 - s1) / std::max(f, r); for (Square s3 = s1 + d; s3 != s2; s3 += d) set_bit(&BetweenBB[s1][s2], s3); @@ -253,20 +261,7 @@ void init_bitboards() { namespace { - Bitboard submask(Bitboard mask, int key) { - - Bitboard subMask = 0; - int bitNum = -1; - - // Extract an unique submask out of a mask according to the given key - for (Square s = SQ_A1; s <= SQ_H8; s++) - if (bit_is_set(mask, s) && bit_is_set(key, Square(++bitNum))) - set_bit(&subMask, s); - - return subMask; - } - - Bitboard sliding_attacks(Square sq, Bitboard occupied, Square deltas[], Bitboard excluded) { + Bitboard sliding_attacks(Square sq, Bitboard occupied, Square deltas[]) { Bitboard attacks = 0; @@ -274,9 +269,7 @@ namespace { { Square s = sq + deltas[i]; - while ( square_is_ok(s) - && square_distance(s, s - deltas[i]) == 1 - && !bit_is_set(excluded, s)) + while (square_is_ok(s) && square_distance(s, s - deltas[i]) == 1) { set_bit(&attacks, s); @@ -289,78 +282,93 @@ namespace { return attacks; } - template - Bitboard pick_magic(Bitboard mask, RKISS& rk, int booster) { + Bitboard pick_random(Bitboard mask, RKISS& rk, int booster) { Bitboard magic; - int lsb; - - if (!Is64) - lsb = first_1(mask); - // Advance PRNG state of a quantity known to be the optimal to - // quickly retrieve all the magics. - for (int i = 0; i < booster; i++) - rk.rand(); + // 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() & rk.rand(); - magic &= Is64 ? rk.rand() : (rk.rand() | rk.rand()); + magic = rk.rand(); + magic = (magic >> s1) | (magic << (64 - s1)); + magic &= rk.rand(); + magic = (magic >> s2) | (magic << (64 - s2)); + magic &= rk.rand(); - if ( BitCount8Bit[(mask * magic) >> 56] >= 6 - && (Is64 || BitCount8Bit[(lsb * magic) >> 56])) + if (BitCount8Bit[(mask * magic) >> 56] >= 6) return magic; } } - void do_magics(Bitboard magic[], Bitboard* attack[], Bitboard attTabl[], - Bitboard mask[], int shift[], Square deltas[]) { - const int MagicBoosters32[] = { 43, 53, 76, 17, 51, 65, 55, 23 }; - const int MagicBoosters64[] = { 26, 21, 21, 32, 31, 9, 5, 11 }; + // init_magic_bitboards() computes all rook and bishop magics at startup. + // Magic bitboards are used to look up attacks of sliding pieces. As reference + // see chessprogramming.wikispaces.com/Magic+Bitboards. In particular, here we + // use the so called "fancy" approach. + + void init_magic_bitboards(Bitboard* attacks[], Bitboard magics[], + Bitboard masks[], int shifts[], Square deltas[]) { + 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], proofs[4096], excluded; - int key, maxKey, index, booster, offset = 0; + Bitboard occupancy[4096], reference[4096], edges, b; + int key, maxKey, index, booster; for (Square s = SQ_A1; s <= SQ_H8; s++) { - excluded = ((Rank1BB | Rank8BB) & ~rank_bb(s)) | ((FileABB | FileHBB) & ~file_bb(s)); + // Board edges are not considered in the relevant occupancies + edges = ((Rank1BB | Rank8BB) & ~rank_bb(s)) | ((FileABB | FileHBB) & ~file_bb(s)); + + // 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_attacks(s, EmptyBoardBB, deltas) & ~edges; + shifts[s] = (CpuIs64Bit ? 64 : 32) - count_1s(masks[s]); + + // Use Carry-Rippler trick to enumerate all subsets of masks[s] and + // store the corresponding sliding attacks in reference[]. + b = maxKey = 0; + do { + occupancy[maxKey] = b; + reference[maxKey++] = sliding_attacks(s, b, deltas); + b = (b - masks[s]) & masks[s]; + } while (b); - attack[s] = &attTabl[offset]; - mask[s] = sliding_attacks(s, EmptyBoardBB, deltas, excluded); - shift[s] = (CpuIs64Bit ? 64 : 32) - count_1s(mask[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] + maxKey; - maxKey = 1 << count_1s(mask[s]); - booster = CpuIs64Bit ? MagicBoosters64[square_rank(s)] : MagicBoosters32[square_rank(s)]; + booster = MagicBoosters[CpuIs64Bit][rank_of(s)]; - // First compute occupancy and attacks for square 's' - for (key = 0; key < maxKey; key++) - { - occupancy[key] = submask(mask[s], key); - proofs[key] = sliding_attacks(s, occupancy[key], deltas, EmptyBoardBB); - } - - // Then find a possible magic and 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)); + magics[s] = pick_random(masks[s], rk, booster); + memset(attacks[s], 0, maxKey * sizeof(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 (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]; + index = CpuIs64Bit ? unsigned((occupancy[key] * magics[s]) >> shifts[s]) + : unsigned(occupancy[key] * magics[s] ^ (occupancy[key] >> 32) * (magics[s] >> 32)) >> shifts[s]; - if (!attack[s][index]) - attack[s][index] = proofs[key]; + if (!attacks[s][index]) + attacks[s][index] = reference[key]; - else if (attack[s][index] != proofs[key]) + else if (attacks[s][index] != reference[key]) break; } } while (key != maxKey); - - offset += maxKey; } } }