X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fbitboard.cpp;h=b19d401af19ad6e13bf36071cdba05cbca9bca5f;hp=04d12c5ebfe389d942a85236542a75b0cf095d90;hb=76f9cd4df1292ffa919e039edcfb8069f576e698;hpb=6d24ef8585c2ed5618eb9b4ab1d8ee35a05ce2cd diff --git a/src/bitboard.cpp b/src/bitboard.cpp index 04d12c5e..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) 2015-2017 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 @@ -45,26 +45,10 @@ Magic BishopMagics[SQUARE_NB]; namespace { - // De Bruijn sequences. See chessprogramming.wikispaces.com/BitScan - const uint64_t DeBruijn64 = 0x3F79D71B4CB0A89ULL; - const uint32_t DeBruijn32 = 0x783A9B23; - - 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 - void init_magics(Bitboard table[], Magic magics[], Square deltas[]); - - // 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; - } - + void init_magics(Bitboard table[], Magic magics[], Direction directions[]); // popcount16() counts the non-zero bits using SWAR-Popcount algorithm @@ -76,46 +60,6 @@ namespace { } } -#ifdef NO_BSF - -/// Software fall-back of lsb() and msb() for CPU lacking hardware support - -Square lsb(Bitboard b) { - assert(b); - return BSFTable[bsf_index(b)]; -} - -Square msb(Bitboard b) { - - assert(b); - unsigned b32; - int result = 0; - - if (b > 0xFFFFFFFF) - { - b >>= 32; - result = 32; - } - - b32 = unsigned(b); - - if (b32 > 0xFFFF) - { - b32 >>= 16; - result += 16; - } - - if (b32 > 0xFF) - { - b32 >>= 8; - result += 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. @@ -145,13 +89,7 @@ void Bitboards::init() { PopCnt16[i] = (uint8_t) popcount16(i); for (Square s = SQ_A1; s <= SQ_H8; ++s) - { - SquareBB[s] = 1ULL << s; - BSFTable[bsf_index(SquareBB[s])] = s; - } - - for (Bitboard b = 2; b < 256; ++b) - MSBTable[b] = MSBTable[b - 1] + !more_than_one(b); + SquareBB[s] = make_bitboard(s); for (File f = FILE_A; f <= FILE_H; ++f) FileBB[f] = f > FILE_A ? FileBB[f - 1] << 1 : FileABB; @@ -188,7 +126,7 @@ void Bitboards::init() { 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) { @@ -199,11 +137,11 @@ void Bitboards::init() { } } - Square RookDeltas[] = { NORTH, EAST, SOUTH, WEST }; - Square BishopDeltas[] = { NORTH_EAST, SOUTH_EAST, SOUTH_WEST, NORTH_WEST }; + Direction RookDirections[] = { NORTH, EAST, SOUTH, WEST }; + Direction BishopDirections[] = { NORTH_EAST, SOUTH_EAST, SOUTH_WEST, NORTH_WEST }; - init_magics(RookTable, RookMagics, RookDeltas); - init_magics(BishopTable, BishopMagics, BishopDeltas); + init_magics(RookTable, RookMagics, RookDirections); + init_magics(BishopTable, BishopMagics, BishopDirections); for (Square s1 = SQ_A1; s1 <= SQ_H8; ++s1) { @@ -225,14 +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; @@ -249,8 +187,9 @@ namespace { // chessprogramming.wikispaces.com/Magic+Bitboards. In particular, here we // use the so called "fancy" approach. - void init_magics(Bitboard table[], Magic magics[], Square deltas[]) { + 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 } }; @@ -268,7 +207,7 @@ namespace { // 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(deltas, s, 0) & ~edges; + 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 @@ -280,7 +219,7 @@ namespace { b = size = 0; do { occupancy[size] = b; - reference[size] = sliding_attack(deltas, s, b); + reference[size] = sliding_attack(directions, s, b); if (HasPext) m.attacks[pext(b, m.mask)] = reference[size];