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    1 /*
    2   Stockfish, a UCI chess playing engine derived from Glaurung 2.1
    3   Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
    4   Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad
    5   Copyright (C) 2015-2020 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
    6 
    7   Stockfish is free software: you can redistribute it and/or modify
    8   it under the terms of the GNU General Public License as published by
    9   the Free Software Foundation, either version 3 of the License, or
   10   (at your option) any later version.
   11 
   12   Stockfish is distributed in the hope that it will be useful,
   13   but WITHOUT ANY WARRANTY; without even the implied warranty of
   14   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   15   GNU General Public License for more details.
   16 
   17   You should have received a copy of the GNU General Public License
   18   along with this program.  If not, see <http://www.gnu.org/licenses/>.
   19 */
   20 
   21 #ifndef BITBOARD_H_INCLUDED
   22 #define BITBOARD_H_INCLUDED
   23 
   24 #include <string>
   25 
   26 #include "types.h"
   27 
   28 namespace Bitbases {
   29 
   30 void init();
   31 bool probe(Square wksq, Square wpsq, Square bksq, Color us);
   32 
   33 }
   34 
   35 namespace Bitboards {
   36 
   37 void init();
   38 const std::string pretty(Bitboard b);
   39 
   40 }
   41 
   42 constexpr Bitboard AllSquares = ~Bitboard(0);
   43 constexpr Bitboard DarkSquares = 0xAA55AA55AA55AA55ULL;
   44 
   45 constexpr Bitboard FileABB = 0x0101010101010101ULL;
   46 constexpr Bitboard FileBBB = FileABB << 1;
   47 constexpr Bitboard FileCBB = FileABB << 2;
   48 constexpr Bitboard FileDBB = FileABB << 3;
   49 constexpr Bitboard FileEBB = FileABB << 4;
   50 constexpr Bitboard FileFBB = FileABB << 5;
   51 constexpr Bitboard FileGBB = FileABB << 6;
   52 constexpr Bitboard FileHBB = FileABB << 7;
   53 
   54 constexpr Bitboard Rank1BB = 0xFF;
   55 constexpr Bitboard Rank2BB = Rank1BB << (8 * 1);
   56 constexpr Bitboard Rank3BB = Rank1BB << (8 * 2);
   57 constexpr Bitboard Rank4BB = Rank1BB << (8 * 3);
   58 constexpr Bitboard Rank5BB = Rank1BB << (8 * 4);
   59 constexpr Bitboard Rank6BB = Rank1BB << (8 * 5);
   60 constexpr Bitboard Rank7BB = Rank1BB << (8 * 6);
   61 constexpr Bitboard Rank8BB = Rank1BB << (8 * 7);
   62 
   63 constexpr Bitboard QueenSide   = FileABB | FileBBB | FileCBB | FileDBB;
   64 constexpr Bitboard CenterFiles = FileCBB | FileDBB | FileEBB | FileFBB;
   65 constexpr Bitboard KingSide    = FileEBB | FileFBB | FileGBB | FileHBB;
   66 constexpr Bitboard Center      = (FileDBB | FileEBB) & (Rank4BB | Rank5BB);
   67 
   68 constexpr Bitboard KingFlank[FILE_NB] = {
   69   QueenSide ^ FileDBB, QueenSide, QueenSide,
   70   CenterFiles, CenterFiles,
   71   KingSide, KingSide, KingSide ^ FileEBB
   72 };
   73 
   74 extern uint8_t PopCnt16[1 << 16];
   75 extern uint8_t SquareDistance[SQUARE_NB][SQUARE_NB];
   76 
   77 extern Bitboard SquareBB[SQUARE_NB];
   78 extern Bitboard LineBB[SQUARE_NB][SQUARE_NB];
   79 extern Bitboard PseudoAttacks[PIECE_TYPE_NB][SQUARE_NB];
   80 extern Bitboard PawnAttacks[COLOR_NB][SQUARE_NB];
   81 
   82 
   83 /// Magic holds all magic bitboards relevant data for a single square
   84 struct Magic {
   85   Bitboard  mask;
   86   Bitboard  magic;
   87   Bitboard* attacks;
   88   unsigned  shift;
   89 
   90   // Compute the attack's index using the 'magic bitboards' approach
   91   unsigned index(Bitboard occupied) const {
   92 
   93     if (HasPext)
   94         return unsigned(pext(occupied, mask));
   95 
   96     if (Is64Bit)
   97         return unsigned(((occupied & mask) * magic) >> shift);
   98 
   99     unsigned lo = unsigned(occupied) & unsigned(mask);
  100     unsigned hi = unsigned(occupied >> 32) & unsigned(mask >> 32);
  101     return (lo * unsigned(magic) ^ hi * unsigned(magic >> 32)) >> shift;
  102   }
  103 };
  104 
  105 extern Magic RookMagics[SQUARE_NB];
  106 extern Magic BishopMagics[SQUARE_NB];
  107 
  108 inline Bitboard square_bb(Square s) {
  109   assert(s >= SQ_A1 && s <= SQ_H8);
  110   return SquareBB[s];
  111 }
  112 
  113 /// Overloads of bitwise operators between a Bitboard and a Square for testing
  114 /// whether a given bit is set in a bitboard, and for setting and clearing bits.
  115 
  116 inline Bitboard  operator&( Bitboard  b, Square s) { return b &  square_bb(s); }
  117 inline Bitboard  operator|( Bitboard  b, Square s) { return b |  square_bb(s); }
  118 inline Bitboard  operator^( Bitboard  b, Square s) { return b ^  square_bb(s); }
  119 inline Bitboard& operator|=(Bitboard& b, Square s) { return b |= square_bb(s); }
  120 inline Bitboard& operator^=(Bitboard& b, Square s) { return b ^= square_bb(s); }
  121 
  122 inline Bitboard  operator&(Square s, Bitboard b) { return b & s; }
  123 inline Bitboard  operator|(Square s, Bitboard b) { return b | s; }
  124 inline Bitboard  operator^(Square s, Bitboard b) { return b ^ s; }
  125 
  126 inline Bitboard  operator|(Square s, Square s2) { return square_bb(s) | square_bb(s2); }
  127 
  128 constexpr bool more_than_one(Bitboard b) {
  129   return b & (b - 1);
  130 }
  131 
  132 inline bool opposite_colors(Square s1, Square s2) {
  133   return bool(DarkSquares & s1) != bool(DarkSquares & s2);
  134 }
  135 
  136 
  137 /// rank_bb() and file_bb() return a bitboard representing all the squares on
  138 /// the given file or rank.
  139 
  140 inline Bitboard rank_bb(Rank r) {
  141   return Rank1BB << (8 * r);
  142 }
  143 
  144 inline Bitboard rank_bb(Square s) {
  145   return rank_bb(rank_of(s));
  146 }
  147 
  148 inline Bitboard file_bb(File f) {
  149   return FileABB << f;
  150 }
  151 
  152 inline Bitboard file_bb(Square s) {
  153   return file_bb(file_of(s));
  154 }
  155 
  156 
  157 /// shift() moves a bitboard one step along direction D
  158 
  159 template<Direction D>
  160 constexpr Bitboard shift(Bitboard b) {
  161   return  D == NORTH      ?  b             << 8 : D == SOUTH      ?  b             >> 8
  162         : D == NORTH+NORTH?  b             <<16 : D == SOUTH+SOUTH?  b             >>16
  163         : D == EAST       ? (b & ~FileHBB) << 1 : D == WEST       ? (b & ~FileABB) >> 1
  164         : D == NORTH_EAST ? (b & ~FileHBB) << 9 : D == NORTH_WEST ? (b & ~FileABB) << 7
  165         : D == SOUTH_EAST ? (b & ~FileHBB) >> 7 : D == SOUTH_WEST ? (b & ~FileABB) >> 9
  166         : 0;
  167 }
  168 
  169 
  170 /// pawn_attacks_bb() returns the squares attacked by pawns of the given color
  171 /// from the squares in the given bitboard.
  172 
  173 template<Color C>
  174 constexpr Bitboard pawn_attacks_bb(Bitboard b) {
  175   return C == WHITE ? shift<NORTH_WEST>(b) | shift<NORTH_EAST>(b)
  176                     : shift<SOUTH_WEST>(b) | shift<SOUTH_EAST>(b);
  177 }
  178 
  179 
  180 /// pawn_double_attacks_bb() returns the squares doubly attacked by pawns of the
  181 /// given color from the squares in the given bitboard.
  182 
  183 template<Color C>
  184 constexpr Bitboard pawn_double_attacks_bb(Bitboard b) {
  185   return C == WHITE ? shift<NORTH_WEST>(b) & shift<NORTH_EAST>(b)
  186                     : shift<SOUTH_WEST>(b) & shift<SOUTH_EAST>(b);
  187 }
  188 
  189 
  190 /// adjacent_files_bb() returns a bitboard representing all the squares on the
  191 /// adjacent files of the given one.
  192 
  193 inline Bitboard adjacent_files_bb(Square s) {
  194   return shift<EAST>(file_bb(s)) | shift<WEST>(file_bb(s));
  195 }
  196 
  197 
  198 /// between_bb() returns squares that are linearly between the given squares
  199 /// If the given squares are not on a same file/rank/diagonal, return 0.
  200 
  201 inline Bitboard between_bb(Square s1, Square s2) {
  202   return LineBB[s1][s2] & ( (AllSquares << (s1 +  (s1 < s2)))
  203                            ^(AllSquares << (s2 + !(s1 < s2))));
  204 }
  205 
  206 
  207 /// forward_ranks_bb() returns a bitboard representing the squares on the ranks
  208 /// in front of the given one, from the point of view of the given color. For instance,
  209 /// forward_ranks_bb(BLACK, SQ_D3) will return the 16 squares on ranks 1 and 2.
  210 
  211 inline Bitboard forward_ranks_bb(Color c, Square s) {
  212   return c == WHITE ? ~Rank1BB << 8 * (rank_of(s) - RANK_1)
  213                     : ~Rank8BB >> 8 * (RANK_8 - rank_of(s));
  214 }
  215 
  216 
  217 /// forward_file_bb() returns a bitboard representing all the squares along the
  218 /// line in front of the given one, from the point of view of the given color.
  219 
  220 inline Bitboard forward_file_bb(Color c, Square s) {
  221   return forward_ranks_bb(c, s) & file_bb(s);
  222 }
  223 
  224 
  225 /// pawn_attack_span() returns a bitboard representing all the squares that can
  226 /// be attacked by a pawn of the given color when it moves along its file,
  227 /// starting from the given square.
  228 
  229 inline Bitboard pawn_attack_span(Color c, Square s) {
  230   return forward_ranks_bb(c, s) & adjacent_files_bb(s);
  231 }
  232 
  233 
  234 /// passed_pawn_span() returns a bitboard which can be used to test if a pawn of
  235 /// the given color and on the given square is a passed pawn.
  236 
  237 inline Bitboard passed_pawn_span(Color c, Square s) {
  238   return forward_ranks_bb(c, s) & (adjacent_files_bb(s) | file_bb(s));
  239 }
  240 
  241 
  242 /// aligned() returns true if the squares s1, s2 and s3 are aligned either on a
  243 /// straight or on a diagonal line.
  244 
  245 inline bool aligned(Square s1, Square s2, Square s3) {
  246   return LineBB[s1][s2] & s3;
  247 }
  248 
  249 
  250 /// distance() functions return the distance between x and y, defined as the
  251 /// number of steps for a king in x to reach y.
  252 
  253 template<typename T1 = Square> inline int distance(Square x, Square y);
  254 template<> inline int distance<File>(Square x, Square y) { return std::abs(file_of(x) - file_of(y)); }
  255 template<> inline int distance<Rank>(Square x, Square y) { return std::abs(rank_of(x) - rank_of(y)); }
  256 template<> inline int distance<Square>(Square x, Square y) { return SquareDistance[x][y]; }
  257 
  258 template<class T> constexpr const T& clamp(const T& v, const T& lo, const T&  hi) {
  259   return v < lo ? lo : v > hi ? hi : v;
  260 }
  261 
  262 /// attacks_bb() returns a bitboard representing all the squares attacked by a
  263 /// piece of type Pt (bishop or rook) placed on 's'.
  264 
  265 template<PieceType Pt>
  266 inline Bitboard attacks_bb(Square s, Bitboard occupied) {
  267 
  268   const Magic& m = Pt == ROOK ? RookMagics[s] : BishopMagics[s];
  269   return m.attacks[m.index(occupied)];
  270 }
  271 
  272 inline Bitboard attacks_bb(PieceType pt, Square s, Bitboard occupied) {
  273 
  274   assert(pt != PAWN);
  275 
  276   switch (pt)
  277   {
  278   case BISHOP: return attacks_bb<BISHOP>(s, occupied);
  279   case ROOK  : return attacks_bb<  ROOK>(s, occupied);
  280   case QUEEN : return attacks_bb<BISHOP>(s, occupied) | attacks_bb<ROOK>(s, occupied);
  281   default    : return PseudoAttacks[pt][s];
  282   }
  283 }
  284 
  285 
  286 /// popcount() counts the number of non-zero bits in a bitboard
  287 
  288 inline int popcount(Bitboard b) {
  289 
  290 #ifndef USE_POPCNT
  291 
  292   union { Bitboard bb; uint16_t u[4]; } v = { b };
  293   return PopCnt16[v.u[0]] + PopCnt16[v.u[1]] + PopCnt16[v.u[2]] + PopCnt16[v.u[3]];
  294 
  295 #elif defined(_MSC_VER) || defined(__INTEL_COMPILER)
  296 
  297   return (int)_mm_popcnt_u64(b);
  298 
  299 #else // Assumed gcc or compatible compiler
  300 
  301   return __builtin_popcountll(b);
  302 
  303 #endif
  304 }
  305 
  306 
  307 /// lsb() and msb() return the least/most significant bit in a non-zero bitboard
  308 
  309 #if defined(__GNUC__)  // GCC, Clang, ICC
  310 
  311 inline Square lsb(Bitboard b) {
  312   assert(b);
  313   return Square(__builtin_ctzll(b));
  314 }
  315 
  316 inline Square msb(Bitboard b) {
  317   assert(b);
  318   return Square(63 ^ __builtin_clzll(b));
  319 }
  320 
  321 #elif defined(_MSC_VER)  // MSVC
  322 
  323 #ifdef _WIN64  // MSVC, WIN64
  324 
  325 inline Square lsb(Bitboard b) {
  326   assert(b);
  327   unsigned long idx;
  328   _BitScanForward64(&idx, b);
  329   return (Square) idx;
  330 }
  331 
  332 inline Square msb(Bitboard b) {
  333   assert(b);
  334   unsigned long idx;
  335   _BitScanReverse64(&idx, b);
  336   return (Square) idx;
  337 }
  338 
  339 #else  // MSVC, WIN32
  340 
  341 inline Square lsb(Bitboard b) {
  342   assert(b);
  343   unsigned long idx;
  344 
  345   if (b & 0xffffffff) {
  346       _BitScanForward(&idx, int32_t(b));
  347       return Square(idx);
  348   } else {
  349       _BitScanForward(&idx, int32_t(b >> 32));
  350       return Square(idx + 32);
  351   }
  352 }
  353 
  354 inline Square msb(Bitboard b) {
  355   assert(b);
  356   unsigned long idx;
  357 
  358   if (b >> 32) {
  359       _BitScanReverse(&idx, int32_t(b >> 32));
  360       return Square(idx + 32);
  361   } else {
  362       _BitScanReverse(&idx, int32_t(b));
  363       return Square(idx);
  364   }
  365 }
  366 
  367 #endif
  368 
  369 #else  // Compiler is neither GCC nor MSVC compatible
  370 
  371 #error "Compiler not supported."
  372 
  373 #endif
  374 
  375 
  376 /// pop_lsb() finds and clears the least significant bit in a non-zero bitboard
  377 
  378 inline Square pop_lsb(Bitboard* b) {
  379   const Square s = lsb(*b);
  380   *b &= *b - 1;
  381   return s;
  382 }
  383 
  384 
  385 /// frontmost_sq() returns the most advanced square for the given color
  386 inline Square frontmost_sq(Color c, Bitboard b) {
  387   return c == WHITE ? msb(b) : lsb(b);
  388 }
  389 
  390 #endif // #ifndef BITBOARD_H_INCLUDED