X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fbitboard.cpp;h=b19d401af19ad6e13bf36071cdba05cbca9bca5f;hp=4ea69ebc757df81fbea8f70d79e1d54c7d568446;hb=255df4ffae29f4a038c9881c1f2f675e2f21f71e;hpb=db4b0d8b7db8db15c16a71212990354094f00b0d diff --git a/src/bitboard.cpp b/src/bitboard.cpp index 4ea69ebc..b19d401a 100644 --- a/src/bitboard.cpp +++ b/src/bitboard.cpp @@ -2,7 +2,7 @@ Stockfish, a UCI chess playing engine derived from Glaurung 2.1 Copyright (C) 2004-2008 Tord Romstad (Glaurung author) Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad - Copyright (C) 2015-2016 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad + Copyright (C) 2015-2018 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 @@ -21,99 +21,45 @@ #include #include "bitboard.h" -#include "bitcount.h" #include "misc.h" +uint8_t PopCnt16[1 << 16]; int SquareDistance[SQUARE_NB][SQUARE_NB]; -Bitboard RookMasks [SQUARE_NB]; -Bitboard RookMagics [SQUARE_NB]; -Bitboard* RookAttacks[SQUARE_NB]; -unsigned RookShifts [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 ForwardRanksBB[COLOR_NB][RANK_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 ForwardFileBB[COLOR_NB][SQUARE_NB]; Bitboard PassedPawnMask[COLOR_NB][SQUARE_NB]; Bitboard PawnAttackSpan[COLOR_NB][SQUARE_NB]; Bitboard PseudoAttacks[PIECE_TYPE_NB][SQUARE_NB]; +Bitboard PawnAttacks[COLOR_NB][SQUARE_NB]; -namespace { +Magic RookMagics[SQUARE_NB]; +Magic BishopMagics[SQUARE_NB]; - // De Bruijn sequences. See chessprogramming.wikispaces.com/BitScan - const uint64_t DeBruijn64 = 0x3F79D71B4CB0A89ULL; - const uint32_t DeBruijn32 = 0x783A9B23; +namespace { - int MSBTable[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 - typedef unsigned (Fn)(Square, Bitboard); - - void init_magics(Bitboard table[], Bitboard* attacks[], Bitboard magics[], - Bitboard masks[], unsigned shifts[], Square deltas[], Fn index); - - // 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. - - unsigned bsf_index(Bitboard b) { - b ^= b - 1; - return Is64Bit ? (b * DeBruijn64) >> 58 - : ((unsigned(b) ^ unsigned(b >> 32)) * DeBruijn32) >> 26; - } -} - -#ifdef NO_BSF - -/// Software fall-back of lsb() and msb() for CPU lacking hardware support - -Square lsb(Bitboard b) { - return BSFTable[bsf_index(b)]; -} - -Square msb(Bitboard b) { - - unsigned b32; - int result = 0; - - if (b > 0xFFFFFFFF) - { - b >>= 32; - result = 32; - } - - b32 = unsigned(b); + void init_magics(Bitboard table[], Magic magics[], Direction directions[]); - if (b32 > 0xFFFF) - { - b32 >>= 16; - result += 16; - } + // popcount16() counts the non-zero bits using SWAR-Popcount algorithm - if (b32 > 0xFF) - { - b32 >>= 8; - result += 8; + unsigned popcount16(unsigned u) { + u -= (u >> 1) & 0x5555U; + u = ((u >> 2) & 0x3333U) + (u & 0x3333U); + u = ((u >> 4) + u) & 0x0F0FU; + return (u * 0x0101U) >> 8; } - - return Square(result + MSBTable[b32]); } -#endif // ifdef NO_BSF - /// Bitboards::pretty() returns an ASCII representation of a bitboard suitable /// to be printed to standard output. Useful for debugging. @@ -139,14 +85,11 @@ const std::string Bitboards::pretty(Bitboard b) { void Bitboards::init() { - for (Square s = SQ_A1; s <= SQ_H8; ++s) - { - SquareBB[s] = 1ULL << s; - BSFTable[bsf_index(SquareBB[s])] = s; - } + for (unsigned i = 0; i < (1 << 16); ++i) + PopCnt16[i] = (uint8_t) popcount16(i); - for (Bitboard b = 2; b < 256; ++b) - MSBTable[b] = MSBTable[b - 1] + !more_than_one(b); + for (Square s = SQ_A1; s <= SQ_H8; ++s) + SquareBB[s] = make_bitboard(s); for (File f = FILE_A; f <= FILE_H; ++f) FileBB[f] = f > FILE_A ? FileBB[f - 1] << 1 : FileABB; @@ -158,14 +101,14 @@ void Bitboards::init() { 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]); + ForwardRanksBB[WHITE][r] = ~(ForwardRanksBB[BLACK][r + 1] = ForwardRanksBB[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]; + ForwardFileBB [c][s] = ForwardRanksBB[c][rank_of(s)] & FileBB[file_of(s)]; + PawnAttackSpan[c][s] = ForwardRanksBB[c][rank_of(s)] & AdjacentFilesBB[file_of(s)]; + PassedPawnMask[c][s] = ForwardFileBB [c][s] | PawnAttackSpan[c][s]; } for (Square s1 = SQ_A1; s1 <= SQ_H8; ++s1) @@ -176,39 +119,43 @@ void Bitboards::init() { 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 } }; + int steps[][5] = { {}, { 7, 9 }, { 6, 10, 15, 17 }, {}, {}, {}, { 1, 7, 8, 9 } }; for (Color c = WHITE; c <= BLACK; ++c) - for (PieceType pt = PAWN; pt <= KING; ++pt) + for (PieceType pt : { PAWN, KNIGHT, KING }) 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]); + Square to = s + Direction(c == WHITE ? steps[pt][i] : -steps[pt][i]); if (is_ok(to) && distance(s, to) < 3) - StepAttacksBB[make_piece(c, pt)][s] |= to; + { + if (pt == PAWN) + PawnAttacks[c][s] |= to; + else + PseudoAttacks[pt][s] |= to; + } } - Square RookDeltas[] = { DELTA_N, DELTA_E, DELTA_S, DELTA_W }; - Square BishopDeltas[] = { DELTA_NE, DELTA_SE, DELTA_SW, DELTA_NW }; + Direction RookDirections[] = { NORTH, EAST, SOUTH, WEST }; + Direction BishopDirections[] = { NORTH_EAST, SOUTH_EAST, SOUTH_WEST, NORTH_WEST }; - init_magics(RookTable, RookAttacks, RookMagics, RookMasks, RookShifts, RookDeltas, magic_index); - init_magics(BishopTable, BishopAttacks, BishopMagics, BishopMasks, BishopShifts, BishopDeltas, magic_index); + init_magics(RookTable, RookMagics, RookDirections); + init_magics(BishopTable, BishopMagics, BishopDirections); for (Square s1 = SQ_A1; s1 <= SQ_H8; ++s1) { PseudoAttacks[QUEEN][s1] = PseudoAttacks[BISHOP][s1] = attacks_bb(s1, 0); PseudoAttacks[QUEEN][s1] |= PseudoAttacks[ ROOK][s1] = attacks_bb< ROOK>(s1, 0); - for (Piece pc = W_BISHOP; pc <= W_ROOK; ++pc) + for (PieceType pt : { BISHOP, ROOK }) for (Square s2 = SQ_A1; s2 <= SQ_H8; ++s2) { - if (!(PseudoAttacks[pc][s1] & s2)) + if (!(PseudoAttacks[pt][s1] & s2)) 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]); + LineBB[s1][s2] = (attacks_bb(pt, s1, 0) & attacks_bb(pt, s2, 0)) | s1 | s2; + BetweenBB[s1][s2] = attacks_bb(pt, s1, SquareBB[s2]) & attacks_bb(pt, s2, SquareBB[s1]); } } } @@ -216,14 +163,14 @@ void Bitboards::init() { namespace { - Bitboard sliding_attack(Square deltas[], Square sq, Bitboard occupied) { + Bitboard sliding_attack(Direction directions[], Square sq, Bitboard occupied) { Bitboard attack = 0; 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]) + for (Square s = sq + directions[i]; + is_ok(s) && distance(s, s - directions[i]) == 1; + s += directions[i]) { attack |= s; @@ -240,17 +187,14 @@ namespace { // 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) { + void init_magics(Bitboard table[], Magic magics[], Direction directions[]) { + // 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 age[4096] = {0}, current = 0, 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) { @@ -262,28 +206,28 @@ namespace { // 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(masks[s]); + 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[size] = b; - reference[size] = sliding_attack(deltas, s, b); + reference[size] = sliding_attack(directions, s, b); if (HasPext) - attacks[s][pext(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; @@ -291,28 +235,30 @@ namespace { // 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(); - while (popcount((magics[s] * masks[s]) >> 56) < 6); + for (int i = 0; i < size; ) + { + for (m.magic = 0; popcount((m.magic * m.mask) >> 56) < 6; ) + m.magic = rng.sparse_rand(); // 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 (++current, 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) { - unsigned idx = index(s, occupancy[i]); + unsigned idx = m.index(occupancy[i]); - if (age[idx] < current) + if (epoch[idx] < cnt) { - age[idx] = current; - attacks[s][idx] = reference[i]; + epoch[idx] = cnt; + m.attacks[idx] = reference[i]; } - else if (attacks[s][idx] != reference[i]) + else if (m.attacks[idx] != reference[i]) break; } - } while (i < size); + } } } }