// 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. public static void init_magics(PieceType pt, Bitboard[][] attacks, Bitboard[] magics, Bitboard[] masks, uint[] shifts, Square[] deltas, Fn index) { int[][] MagicBoosters = new int[2][] { new int[] { 969, 1976, 2850, 542, 2069, 2852, 1708, 164 }, new int[] { 3101, 552, 3555, 926, 834, 26, 2131, 1117 } }; RKISS rk = new RKISS(); Bitboard[] occupancy = new UInt64[4096], reference = new UInt64[4096]; Bitboard edges, b; int i, size, booster; for (Square s = SquareS.SQ_A1; s <= SquareS.SQ_H8; s++) { // Board edges are not considered in the relevant occupancies edges = ((BitBoard.Rank1BB | BitBoard.Rank8BB) & ~BitBoard.rank_bb_square(s)) | ((BitBoard.FileABB | BitBoard.FileHBB) & ~BitBoard.file_bb_square(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_attack(deltas, s, 0) & ~edges; shifts[s] = 32 - (uint)Bitcount.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 = 0; size = 0; do { occupancy[size] = b; reference[size] = sliding_attack(deltas, s, b); size++; b = (b - masks[s]) & masks[s]; } while (b != 0); // Set the offset for the table of the next square. We have individual // table sizes for each square with "Fancy Magic Bitboards". attacks[s] = new Bitboard[size]; booster = MagicBoosters[0][Types.rank_of(s)]; // 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] = rk.magic_rand(booster); }while (Bitcount.popcount_Max15((magics[s] * masks[s]) >> 56) < 6); Array.Clear(attacks[s], 0, size); // 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], pt)]; if (attack != 0 && attack != reference[i]) { break; } Debug.Assert(reference[i] != 0); //attack = reference[i]; attacks[s][index(s, occupancy[i], pt)] = reference[i]; } } while (i != size); } }
/// move_to_san() takes a position and a legal Move as input and returns its /// short algebraic notation representation. public static string move_to_san(Position pos, Move m) { if (m == MoveS.MOVE_NONE) { return("(none)"); } if (m == MoveS.MOVE_NULL) { return("(null)"); } Debug.Assert((new MoveList(pos, GenTypeS.LEGAL).contains(m))); Bitboard others, b; string san = ""; Color us = pos.side_to_move(); Square from = Types.from_sq(m); Square to = Types.to_sq(m); Piece pc = pos.piece_on(from); PieceType pt = Types.type_of_piece(pc); if (Types.type_of_move(m) == MoveTypeS.CASTLING) { san = to > from ? "O-O" : "O-O-O"; } else { if (pt != PieceTypeS.PAWN) { san = "" + PieceToChar[ColorS.WHITE][pt]; // Upper case // A disambiguation occurs if we have more then one piece of type 'pt' // that can reach 'to' with a legal move. others = b = (pos.attacks_from_piece_square(pc, to) & pos.pieces_color_piecetype(us, pt)) ^ BitBoard.SquareBB[from]; while (b != 0) { Square s = BitBoard.pop_lsb(ref b); if (!pos.legal(Types.make_move(s, to), pos.pinned_pieces(us))) { others ^= BitBoard.SquareBB[s]; } } if (0 == others) { /* Disambiguation is not needed */ } else if (0 == (others & BitBoard.file_bb_square(from))) { san += Types.file_to_char(Types.file_of(from)); } else if (0 == (others & BitBoard.rank_bb_square(from))) { san += Types.rank_to_char(Types.rank_of(from)); } else { san += Types.square_to_string(from); } } else if (pos.capture(m)) { san = "" + Types.file_to_char(Types.file_of(from)); } if (pos.capture(m)) { san += 'x'; } san += Types.square_to_string(to); if (Types.type_of_move(m) == MoveTypeS.PROMOTION) { san += "=" + PieceToChar[ColorS.WHITE][Types.promotion_type(m)]; } } if (pos.gives_check(m, new CheckInfo(pos))) { StateInfo st = new StateInfo(); pos.do_move(m, st); san += (new MoveList(pos, GenTypeS.LEGAL)).size() > 0 ? "+" : "#"; pos.undo_move(m); } return(san); }
public static int generate_pawn_moves(Position pos, ExtMove[] mlist, int mPos, Bitboard target, CheckInfo ci, Color Us, GenType Type) { // Compute our parametrized parameters at compile time, named according to // the point of view of white side. Color Them = (Us == ColorS.WHITE ? ColorS.BLACK : ColorS.WHITE); Bitboard TRank8BB = (Us == ColorS.WHITE ? BitBoard.Rank8BB : BitBoard.Rank1BB); Bitboard TRank7BB = (Us == ColorS.WHITE ? BitBoard.Rank7BB : BitBoard.Rank2BB); Bitboard TRank3BB = (Us == ColorS.WHITE ? BitBoard.Rank3BB : BitBoard.Rank6BB); Square Up = (Us == ColorS.WHITE ? SquareS.DELTA_N : SquareS.DELTA_S); Square Right = (Us == ColorS.WHITE ? SquareS.DELTA_NE : SquareS.DELTA_SW); Square Left = (Us == ColorS.WHITE ? SquareS.DELTA_NW : SquareS.DELTA_SE); Bitboard b1, b2, dc1, dc2, emptySquares = 0; Bitboard pawnsOn7 = pos.pieces_color_piecetype(Us, PieceTypeS.PAWN) & TRank7BB; Bitboard pawnsNotOn7 = pos.pieces_color_piecetype(Us, PieceTypeS.PAWN) & ~TRank7BB; Bitboard enemies = (Type == GenTypeS.EVASIONS ? pos.pieces_color(Them) & target : Type == GenTypeS.CAPTURES ? target : pos.pieces_color(Them)); // Single and double pawn pushes, no promotions if (Type != GenTypeS.CAPTURES) { emptySquares = (Type == GenTypeS.QUIETS || Type == GenTypeS.QUIET_CHECKS ? target : ~pos.pieces()); b1 = BitBoard.shift_bb(pawnsNotOn7, Up) & emptySquares; b2 = BitBoard.shift_bb(b1 & TRank3BB, Up) & emptySquares; if (Type == GenTypeS.EVASIONS) // Consider only blocking squares { b1 &= target; b2 &= target; } if (Type == GenTypeS.QUIET_CHECKS) { b1 &= pos.attacks_from_pawn(ci.ksq, Them); b2 &= pos.attacks_from_pawn(ci.ksq, Them); // Add pawn pushes which give discovered check. This is possible only // if the pawn is not on the same file as the enemy king, because we // don't generate captures. Note that a possible discovery check // promotion has been already generated among captures. if ((pawnsNotOn7 & ci.dcCandidates) != 0) { dc1 = BitBoard.shift_bb(pawnsNotOn7 & ci.dcCandidates, Up) & emptySquares & ~BitBoard.file_bb_square(ci.ksq); dc2 = BitBoard.shift_bb(dc1 & TRank3BB, Up) & emptySquares; b1 |= dc1; b2 |= dc2; } } while (b1 != 0) { Square to = BitBoard.pop_lsb(ref b1); mlist[mPos++].move = Types.make_move(to - Up, to); } while (b2 != 0) { Square to = BitBoard.pop_lsb(ref b2); mlist[mPos++].move = Types.make_move(to - Up - Up, to); } } // Promotions and underpromotions if (pawnsOn7 != 0 && (Type != GenTypeS.EVASIONS || (target & TRank8BB) != 0)) { if (Type == GenTypeS.CAPTURES) { emptySquares = ~pos.pieces(); } if (Type == GenTypeS.EVASIONS) { emptySquares &= target; } mPos = generate_promotions(mlist, mPos, pawnsOn7, enemies, ci, Type, Right); mPos = generate_promotions(mlist, mPos, pawnsOn7, enemies, ci, Type, Left); mPos = generate_promotions(mlist, mPos, pawnsOn7, emptySquares, ci, Type, Up); } // Standard and en-passant captures if (Type == GenTypeS.CAPTURES || Type == GenTypeS.EVASIONS || Type == GenTypeS.NON_EVASIONS) { b1 = BitBoard.shift_bb(pawnsNotOn7, Right) & enemies; b2 = BitBoard.shift_bb(pawnsNotOn7, Left) & enemies; while (b1 != 0) { Square to = BitBoard.pop_lsb(ref b1); mlist[mPos++].move = Types.make_move(to - Right, to); } while (b2 != 0) { Square to = BitBoard.pop_lsb(ref b2); mlist[mPos++].move = Types.make_move(to - Left, to); } if (pos.ep_square() != SquareS.SQ_NONE) { Debug.Assert(Types.rank_of(pos.ep_square()) == Types.relative_rank_rank(Us, RankS.RANK_6)); // An en passant capture can be an evasion only if the checking piece // is the double pushed pawn and so is in the target. Otherwise this // is a discovery check and we are forced to do otherwise. if (Type == GenTypeS.EVASIONS && (target & BitBoard.SquareBB[(pos.ep_square() - Up)]) == 0) { return(mPos); } b1 = pawnsNotOn7 & pos.attacks_from_pawn(pos.ep_square(), Them); Debug.Assert(b1 != 0); while (b1 != 0) { mlist[mPos++].move = Types.make(BitBoard.pop_lsb(ref b1), pos.ep_square(), MoveTypeS.ENPASSANT); } } } return(mPos); }