X-Git-Url: https://git.sesse.net/?a=blobdiff_plain;f=src%2Fposition.cpp;h=c09a953b62e3a7612d53f03069266a2a00493d6d;hb=99f3ad6858889bbc40c016c96c9f7e53a773e49e;hp=2126741e717ae4fbb2cf1d14013d3d47f9d79c2f;hpb=c2048136ec73a1d4437d286d34539a05910d83d7;p=stockfish diff --git a/src/position.cpp b/src/position.cpp index 2126741e..c09a953b 100644 --- a/src/position.cpp +++ b/src/position.cpp @@ -1,7 +1,8 @@ /* Stockfish, a UCI chess playing engine derived from Glaurung 2.1 Copyright (C) 2004-2008 Tord Romstad (Glaurung author) - Copyright (C) 2008-2010 Marco Costalba, Joona Kiiski, Tord Romstad + Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad + Copyright (C) 2015-2016 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 @@ -17,1079 +18,798 @@ along with this program. If not, see . */ - -//// -//// Includes -//// - +#include #include -#include -#include -#include -#include +#include // For offsetof() +#include // For std::memset, std::memcmp +#include #include -#include "bitcount.h" -#include "mersenne.h" +#include "bitboard.h" +#include "misc.h" #include "movegen.h" -#include "movepick.h" #include "position.h" -#include "psqtab.h" -#include "san.h" +#include "thread.h" #include "tt.h" -#include "ucioption.h" +#include "uci.h" using std::string; -using std::cout; -using std::endl; -struct PieceLetters : std::map { +namespace PSQT { + extern Score psq[PIECE_NB][SQUARE_NB]; +} - PieceLetters() { +namespace Zobrist { - operator[]('K') = WK; operator[]('k') = BK; - operator[]('Q') = WQ; operator[]('q') = BQ; - operator[]('R') = WR; operator[]('r') = BR; - operator[]('B') = WB; operator[]('b') = BB; - operator[]('N') = WN; operator[]('n') = BN; - operator[]('P') = WP; operator[]('p') = BP; - } -}; + Key psq[PIECE_NB][SQUARE_NB]; + Key enpassant[FILE_NB]; + Key castling[CASTLING_RIGHT_NB]; + Key side; +} -//// -//// Variables -//// +namespace { -Key Position::zobrist[2][8][64]; -Key Position::zobEp[64]; -Key Position::zobCastle[16]; -Key Position::zobSideToMove; -Key Position::zobExclusion; +const string PieceToChar(" PNBRQK pnbrqk"); -Score Position::PieceSquareTable[16][64]; +// min_attacker() is a helper function used by see() to locate the least +// valuable attacker for the side to move, remove the attacker we just found +// from the bitboards and scan for new X-ray attacks behind it. -static bool RequestPending = false; +template +PieceType min_attacker(const Bitboard* bb, Square to, Bitboard stmAttackers, + Bitboard& occupied, Bitboard& attackers) { + Bitboard b = stmAttackers & bb[Pt]; + if (!b) + return min_attacker(bb, to, stmAttackers, occupied, attackers); -/// Constructors + occupied ^= b & ~(b - 1); -CheckInfo::CheckInfo(const Position& pos) { + if (Pt == PAWN || Pt == BISHOP || Pt == QUEEN) + attackers |= attacks_bb(to, occupied) & (bb[BISHOP] | bb[QUEEN]); - Color us = pos.side_to_move(); - Color them = opposite_color(us); + if (Pt == ROOK || Pt == QUEEN) + attackers |= attacks_bb(to, occupied) & (bb[ROOK] | bb[QUEEN]); - ksq = pos.king_square(them); - dcCandidates = pos.discovered_check_candidates(us); + attackers &= occupied; // After X-ray that may add already processed pieces + return (PieceType)Pt; +} - checkSq[PAWN] = pos.attacks_from(ksq, them); - checkSq[KNIGHT] = pos.attacks_from(ksq); - checkSq[BISHOP] = pos.attacks_from(ksq); - checkSq[ROOK] = pos.attacks_from(ksq); - checkSq[QUEEN] = checkSq[BISHOP] | checkSq[ROOK]; - checkSq[KING] = EmptyBoardBB; +template<> +PieceType min_attacker(const Bitboard*, Square, Bitboard, Bitboard&, Bitboard&) { + return KING; // No need to update bitboards: it is the last cycle } +} // namespace -/// Position c'tors. Here we always create a copy of the original position -/// or the FEN string, we want the new born Position object do not depend -/// on any external data so we detach state pointer from the source one. -Position::Position(int th) : threadID(th) {} +/// operator<<(Position) returns an ASCII representation of the position -Position::Position(const Position& pos, int th) { +std::ostream& operator<<(std::ostream& os, const Position& pos) { - memcpy(this, &pos, sizeof(Position)); - detach(); // Always detach() in copy c'tor to avoid surprises - threadID = th; -} + os << "\n +---+---+---+---+---+---+---+---+\n"; -Position::Position(const string& fen, int th) { + for (Rank r = RANK_8; r >= RANK_1; --r) + { + for (File f = FILE_A; f <= FILE_H; ++f) + os << " | " << PieceToChar[pos.piece_on(make_square(f, r))]; + + os << " |\n +---+---+---+---+---+---+---+---+\n"; + } + + os << "\nFen: " << pos.fen() << "\nKey: " << std::hex << std::uppercase + << std::setfill('0') << std::setw(16) << pos.key() << std::dec << "\nCheckers: "; - from_fen(fen); - threadID = th; + for (Bitboard b = pos.checkers(); b; ) + os << UCI::square(pop_lsb(&b)) << " "; + + return os; } -/// Position::detach() copies the content of the current state and castling -/// masks inside the position itself. This is needed when the st pointee could -/// become stale, as example because the caller is about to going out of scope. +/// Position::init() initializes at startup the various arrays used to compute +/// hash keys. + +void Position::init() { + + PRNG rng(1070372); -void Position::detach() { + for (Piece pc : Pieces) + for (Square s = SQ_A1; s <= SQ_H8; ++s) + Zobrist::psq[pc][s] = rng.rand(); - startState = *st; - st = &startState; - st->previous = NULL; // as a safe guard + for (File f = FILE_A; f <= FILE_H; ++f) + Zobrist::enpassant[f] = rng.rand(); + + for (int cr = NO_CASTLING; cr <= ANY_CASTLING; ++cr) + { + Zobrist::castling[cr] = 0; + Bitboard b = cr; + while (b) + { + Key k = Zobrist::castling[1ULL << pop_lsb(&b)]; + Zobrist::castling[cr] ^= k ? k : rng.rand(); + } + } + + Zobrist::side = rng.rand(); } -/// Position::from_fen() initializes the position object with the given FEN -/// string. This function is not very robust - make sure that input FENs are -/// correct (this is assumed to be the responsibility of the GUI). +/// Position::set() initializes the position object with the given FEN string. +/// This function is not very robust - make sure that input FENs are correct, +/// this is assumed to be the responsibility of the GUI. -void Position::from_fen(const string& fen) { +Position& Position::set(const string& fenStr, bool isChess960, StateInfo* si, Thread* th) { /* A FEN string defines a particular position using only the ASCII character set. - A FEN string contains six fields. The separator between fields is a space. The fields are: + A FEN string contains six fields separated by a space. The fields are: - 1) Piece placement (from white's perspective). Each rank is described, starting with rank 8 and ending - with rank 1; within each rank, the contents of each square are described from file a through file h. - Following the Standard Algebraic Notation (SAN), each piece is identified by a single letter taken - from the standard English names. White pieces are designated using upper-case letters ("PNBRQK") - while Black take lowercase ("pnbrqk"). Blank squares are noted using digits 1 through 8 (the number - of blank squares), and "/" separate ranks. + 1) Piece placement (from white's perspective). Each rank is described, starting + with rank 8 and ending with rank 1. Within each rank, the contents of each + square are described from file A through file H. Following the Standard + Algebraic Notation (SAN), each piece is identified by a single letter taken + from the standard English names. White pieces are designated using upper-case + letters ("PNBRQK") whilst Black uses lowercase ("pnbrqk"). Blank squares are + noted using digits 1 through 8 (the number of blank squares), and "/" + separates ranks. 2) Active color. "w" means white moves next, "b" means black. - 3) Castling availability. If neither side can castle, this is "-". Otherwise, this has one or more - letters: "K" (White can castle kingside), "Q" (White can castle queenside), "k" (Black can castle - kingside), and/or "q" (Black can castle queenside). + 3) Castling availability. If neither side can castle, this is "-". Otherwise, + this has one or more letters: "K" (White can castle kingside), "Q" (White + can castle queenside), "k" (Black can castle kingside), and/or "q" (Black + can castle queenside). - 4) En passant target square in algebraic notation. If there's no en passant target square, this is "-". - If a pawn has just made a 2-square move, this is the position "behind" the pawn. This is recorded - regardless of whether there is a pawn in position to make an en passant capture. + 4) En passant target square (in algebraic notation). If there's no en passant + target square, this is "-". If a pawn has just made a 2-square move, this + is the position "behind" the pawn. This is recorded regardless of whether + there is a pawn in position to make an en passant capture. - 5) Halfmove clock: This is the number of halfmoves since the last pawn advance or capture. This is used - to determine if a draw can be claimed under the fifty-move rule. + 5) Halfmove clock. This is the number of halfmoves since the last pawn advance + or capture. This is used to determine if a draw can be claimed under the + fifty-move rule. - 6) Fullmove number: The number of the full move. It starts at 1, and is incremented after Black's move. + 6) Fullmove number. The number of the full move. It starts at 1, and is + incremented after Black's move. */ - static PieceLetters pieceLetters; + unsigned char col, row, token; + size_t idx; + Square sq = SQ_A8; + std::istringstream ss(fenStr); - char token; - std::istringstream ss(fen); - Rank rank = RANK_8; - File file = FILE_A; + std::memset(this, 0, sizeof(Position)); + std::memset(si, 0, sizeof(StateInfo)); + std::fill_n(&pieceList[0][0], sizeof(pieceList) / sizeof(Square), SQ_NONE); + st = si; - clear(); + ss >> std::noskipws; - // 1. Piece placement field - while (ss.get(token) && token != ' ') + // 1. Piece placement + while ((ss >> token) && !isspace(token)) { if (isdigit(token)) - { - file += token - '0'; // Skip the given number of files - continue; - } + sq += Square(token - '0'); // Advance the given number of files + else if (token == '/') + sq -= Square(16); + + else if ((idx = PieceToChar.find(token)) != string::npos) { - file = FILE_A; - rank--; - continue; + put_piece(Piece(idx), sq); + ++sq; } - - if (pieceLetters.find(token) == pieceLetters.end()) - goto incorrect_fen; - - put_piece(pieceLetters[token], make_square(file, rank)); - file++; } // 2. Active color - if (!ss.get(token) || (token != 'w' && token != 'b')) - goto incorrect_fen; - + ss >> token; sideToMove = (token == 'w' ? WHITE : BLACK); + ss >> token; + + // 3. Castling availability. Compatible with 3 standards: Normal FEN standard, + // Shredder-FEN that uses the letters of the columns on which the rooks began + // the game instead of KQkq and also X-FEN standard that, in case of Chess960, + // if an inner rook is associated with the castling right, the castling tag is + // replaced by the file letter of the involved rook, as for the Shredder-FEN. + while ((ss >> token) && !isspace(token)) + { + Square rsq; + Color c = islower(token) ? BLACK : WHITE; + Piece rook = make_piece(c, ROOK); - if (!ss.get(token) || token != ' ') - goto incorrect_fen; + token = char(toupper(token)); - // 3. Castling availability - while (ss.get(token) && token != ' ') - { - if (token == '-') + if (token == 'K') + for (rsq = relative_square(c, SQ_H1); piece_on(rsq) != rook; --rsq) {} + + else if (token == 'Q') + for (rsq = relative_square(c, SQ_A1); piece_on(rsq) != rook; ++rsq) {} + + else if (token >= 'A' && token <= 'H') + rsq = make_square(File(token - 'A'), relative_rank(c, RANK_1)); + + else continue; - if (!set_castling_rights(token)) - goto incorrect_fen; + set_castling_right(c, rsq); } - // 4. En passant square -- ignore if no capture is possible - char col, row; - if ( (ss.get(col) && (col >= 'a' && col <= 'h')) - && (ss.get(row) && (row == '3' || row == '6'))) + // 4. En passant square. Ignore if no pawn capture is possible + if ( ((ss >> col) && (col >= 'a' && col <= 'h')) + && ((ss >> row) && (row == '3' || row == '6'))) { - Square fenEpSquare = make_square(file_from_char(col), rank_from_char(row)); - Color them = opposite_color(sideToMove); + st->epSquare = make_square(File(col - 'a'), Rank(row - '1')); - if (attacks_from(fenEpSquare, them) & pieces(PAWN, sideToMove)) - st->epSquare = fenEpSquare; + if (!(attackers_to(st->epSquare) & pieces(sideToMove, PAWN))) + st->epSquare = SQ_NONE; } + else + st->epSquare = SQ_NONE; - // 5-6. Halfmove clock and fullmove number are not parsed + // 5-6. Halfmove clock and fullmove number + ss >> std::skipws >> st->rule50 >> gamePly; - // Various initialisations - castleRightsMask[make_square(initialKFile, RANK_1)] ^= WHITE_OO | WHITE_OOO; - castleRightsMask[make_square(initialKFile, RANK_8)] ^= BLACK_OO | BLACK_OOO; - castleRightsMask[make_square(initialKRFile, RANK_1)] ^= WHITE_OO; - castleRightsMask[make_square(initialKRFile, RANK_8)] ^= BLACK_OO; - castleRightsMask[make_square(initialQRFile, RANK_1)] ^= WHITE_OOO; - castleRightsMask[make_square(initialQRFile, RANK_8)] ^= BLACK_OOO; + // Convert from fullmove starting from 1 to ply starting from 0, + // handle also common incorrect FEN with fullmove = 0. + gamePly = std::max(2 * (gamePly - 1), 0) + (sideToMove == BLACK); - find_checkers(); + chess960 = isChess960; + thisThread = th; + set_state(st); - st->key = compute_key(); - st->pawnKey = compute_pawn_key(); - st->materialKey = compute_material_key(); - st->value = compute_value(); - st->npMaterial[WHITE] = compute_non_pawn_material(WHITE); - st->npMaterial[BLACK] = compute_non_pawn_material(BLACK); - return; + assert(pos_is_ok()); -incorrect_fen: - cout << "Error in FEN string: " << fen << endl; + return *this; } -/// Position::set_castling_rights() sets castling parameters castling avaiability. -/// This function is compatible with 3 standards: Normal FEN standard, Shredder-FEN -/// that uses the letters of the columns on which the rooks began the game instead -/// of KQkq and also X-FEN standard that, in case of Chess960, if an inner Rook is -/// associated with the castling right, the traditional castling tag will be replaced -/// by the file letter of the involved rook as for the Shredder-FEN. +/// Position::set_castling_right() is a helper function used to set castling +/// rights given the corresponding color and the rook starting square. -bool Position::set_castling_rights(char token) { +void Position::set_castling_right(Color c, Square rfrom) { - Color c = token >= 'a' ? BLACK : WHITE; - Square sqA = (c == WHITE ? SQ_A1 : SQ_A8); - Square sqH = (c == WHITE ? SQ_H1 : SQ_H8); - Piece rook = (c == WHITE ? WR : BR); + Square kfrom = square(c); + CastlingSide cs = kfrom < rfrom ? KING_SIDE : QUEEN_SIDE; + CastlingRight cr = (c | cs); - initialKFile = square_file(king_square(c)); - token = char(toupper(token)); + st->castlingRights |= cr; + castlingRightsMask[kfrom] |= cr; + castlingRightsMask[rfrom] |= cr; + castlingRookSquare[cr] = rfrom; - if (token == 'K') - { - for (Square sq = sqH; sq >= sqA; sq--) - if (piece_on(sq) == rook) - { - allow_oo(c); - initialKRFile = square_file(sq); - break; - } - } - else if (token == 'Q') - { - for (Square sq = sqA; sq <= sqH; sq++) - if (piece_on(sq) == rook) - { - allow_ooo(c); - initialQRFile = square_file(sq); - break; - } - } - else if (token >= 'A' && token <= 'H') - { - File rookFile = File(token - 'A') + FILE_A; - if (rookFile < initialKFile) - { - allow_ooo(c); - initialQRFile = rookFile; - } - else - { - allow_oo(c); - initialKRFile = rookFile; - } - } - else return false; + Square kto = relative_square(c, cs == KING_SIDE ? SQ_G1 : SQ_C1); + Square rto = relative_square(c, cs == KING_SIDE ? SQ_F1 : SQ_D1); - return true; + for (Square s = std::min(rfrom, rto); s <= std::max(rfrom, rto); ++s) + if (s != kfrom && s != rfrom) + castlingPath[cr] |= s; + + for (Square s = std::min(kfrom, kto); s <= std::max(kfrom, kto); ++s) + if (s != kfrom && s != rfrom) + castlingPath[cr] |= s; } -/// Position::to_fen() converts the position object to a FEN string. This is -/// probably only useful for debugging. +/// Position::set_check_info() sets king attacks to detect if a move gives check -const string Position::to_fen() const { +void Position::set_check_info(StateInfo* si) const { - static const string pieceLetters = " PNBRQK pnbrqk"; - string fen; - int skip; + si->blockersForKing[WHITE] = slider_blockers(pieces(BLACK), square(WHITE), si->pinnersForKing[WHITE]); + si->blockersForKing[BLACK] = slider_blockers(pieces(WHITE), square(BLACK), si->pinnersForKing[BLACK]); - for (Rank rank = RANK_8; rank >= RANK_1; rank--) - { - skip = 0; - for (File file = FILE_A; file <= FILE_H; file++) - { - Square sq = make_square(file, rank); - if (!square_is_occupied(sq)) - { skip++; - continue; - } - if (skip > 0) - { - fen += (char)skip + '0'; - skip = 0; - } - fen += pieceLetters[piece_on(sq)]; - } - if (skip > 0) - fen += (char)skip + '0'; - - fen += (rank > RANK_1 ? '/' : ' '); - } - fen += (sideToMove == WHITE ? "w " : "b "); - if (st->castleRights != NO_CASTLES) - { - if (initialKFile == FILE_E && initialQRFile == FILE_A && initialKRFile == FILE_H) - { - if (can_castle_kingside(WHITE)) fen += 'K'; - if (can_castle_queenside(WHITE)) fen += 'Q'; - if (can_castle_kingside(BLACK)) fen += 'k'; - if (can_castle_queenside(BLACK)) fen += 'q'; - } - else - { - if (can_castle_kingside(WHITE)) - fen += char(toupper(file_to_char(initialKRFile))); - if (can_castle_queenside(WHITE)) - fen += char(toupper(file_to_char(initialQRFile))); - if (can_castle_kingside(BLACK)) - fen += file_to_char(initialKRFile); - if (can_castle_queenside(BLACK)) - fen += file_to_char(initialQRFile); - } - } else - fen += '-'; - - fen += ' '; - if (ep_square() != SQ_NONE) - fen += square_to_string(ep_square()); - else - fen += '-'; + Square ksq = square(~sideToMove); - return fen; + si->checkSquares[PAWN] = attacks_from(ksq, ~sideToMove); + si->checkSquares[KNIGHT] = attacks_from(ksq); + si->checkSquares[BISHOP] = attacks_from(ksq); + si->checkSquares[ROOK] = attacks_from(ksq); + si->checkSquares[QUEEN] = si->checkSquares[BISHOP] | si->checkSquares[ROOK]; + si->checkSquares[KING] = 0; } -/// Position::print() prints an ASCII representation of the position to -/// the standard output. If a move is given then also the san is print. +/// Position::set_state() computes the hash keys of the position, and other +/// data that once computed is updated incrementally as moves are made. +/// The function is only used when a new position is set up, and to verify +/// the correctness of the StateInfo data when running in debug mode. -void Position::print(Move m) const { +void Position::set_state(StateInfo* si) const { - static const string pieceLetters = " PNBRQK PNBRQK ."; + si->key = si->pawnKey = si->materialKey = 0; + si->nonPawnMaterial[WHITE] = si->nonPawnMaterial[BLACK] = VALUE_ZERO; + si->psq = SCORE_ZERO; + si->checkersBB = attackers_to(square(sideToMove)) & pieces(~sideToMove); - // Check for reentrancy, as example when called from inside - // MovePicker that is used also here in move_to_san() - if (RequestPending) - return; + set_check_info(si); - RequestPending = true; - - cout << endl; - if (m != MOVE_NONE) + for (Bitboard b = pieces(); b; ) { - Position p(*this, thread()); - string col = (color_of_piece_on(move_from(m)) == BLACK ? ".." : ""); - cout << "Move is: " << col << move_to_san(p, m) << endl; + Square s = pop_lsb(&b); + Piece pc = piece_on(s); + si->key ^= Zobrist::psq[pc][s]; + si->psq += PSQT::psq[pc][s]; } - for (Rank rank = RANK_8; rank >= RANK_1; rank--) - { - cout << "+---+---+---+---+---+---+---+---+" << endl; - for (File file = FILE_A; file <= FILE_H; file++) - { - Square sq = make_square(file, rank); - Piece piece = piece_on(sq); - if (piece == EMPTY && square_color(sq) == WHITE) - piece = NO_PIECE; - char col = (color_of_piece_on(sq) == BLACK ? '=' : ' '); - cout << '|' << col << pieceLetters[piece] << col; - } - cout << '|' << endl; - } - cout << "+---+---+---+---+---+---+---+---+" << endl - << "Fen is: " << to_fen() << endl - << "Key is: " << st->key << endl; + if (si->epSquare != SQ_NONE) + si->key ^= Zobrist::enpassant[file_of(si->epSquare)]; - RequestPending = false; -} + if (sideToMove == BLACK) + si->key ^= Zobrist::side; + si->key ^= Zobrist::castling[si->castlingRights]; -/// Position:hidden_checkers<>() returns a bitboard of all pinned (against the -/// king) pieces for the given color and for the given pinner type. Or, when -/// template parameter FindPinned is false, the pieces of the given color -/// candidate for a discovery check against the enemy king. -/// Bitboard checkersBB must be already updated when looking for pinners. + for (Bitboard b = pieces(PAWN); b; ) + { + Square s = pop_lsb(&b); + si->pawnKey ^= Zobrist::psq[piece_on(s)][s]; + } -template -Bitboard Position::hidden_checkers(Color c) const { + for (Piece pc : Pieces) + { + if (type_of(pc) != PAWN && type_of(pc) != KING) + si->nonPawnMaterial[color_of(pc)] += pieceCount[pc] * PieceValue[MG][pc]; + + for (int cnt = 0; cnt < pieceCount[pc]; ++cnt) + si->materialKey ^= Zobrist::psq[pc][cnt]; + } +} - Bitboard result = EmptyBoardBB; - Bitboard pinners = pieces_of_color(FindPinned ? opposite_color(c) : c); - // Pinned pieces protect our king, dicovery checks attack - // the enemy king. - Square ksq = king_square(FindPinned ? c : opposite_color(c)); +/// Position::fen() returns a FEN representation of the position. In case of +/// Chess960 the Shredder-FEN notation is used. This is mainly a debugging function. - // Pinners are sliders, not checkers, that give check when candidate pinned is removed - pinners &= (pieces(ROOK, QUEEN) & RookPseudoAttacks[ksq]) | (pieces(BISHOP, QUEEN) & BishopPseudoAttacks[ksq]); +const string Position::fen() const { - if (FindPinned && pinners) - pinners &= ~st->checkersBB; + int emptyCnt; + std::ostringstream ss; - while (pinners) + for (Rank r = RANK_8; r >= RANK_1; --r) { - Square s = pop_1st_bit(&pinners); - Bitboard b = squares_between(s, ksq) & occupied_squares(); + for (File f = FILE_A; f <= FILE_H; ++f) + { + for (emptyCnt = 0; f <= FILE_H && empty(make_square(f, r)); ++f) + ++emptyCnt; + + if (emptyCnt) + ss << emptyCnt; - assert(b); + if (f <= FILE_H) + ss << PieceToChar[piece_on(make_square(f, r))]; + } - if ( !(b & (b - 1)) // Only one bit set? - && (b & pieces_of_color(c))) // Is an our piece? - result |= b; + if (r > RANK_1) + ss << '/'; } - return result; -} + ss << (sideToMove == WHITE ? " w " : " b "); -/// Position:pinned_pieces() returns a bitboard of all pinned (against the -/// king) pieces for the given color. Note that checkersBB bitboard must -/// be already updated. + if (can_castle(WHITE_OO)) + ss << (chess960 ? char('A' + file_of(castling_rook_square(WHITE | KING_SIDE))) : 'K'); -Bitboard Position::pinned_pieces(Color c) const { + if (can_castle(WHITE_OOO)) + ss << (chess960 ? char('A' + file_of(castling_rook_square(WHITE | QUEEN_SIDE))) : 'Q'); - return hidden_checkers(c); -} + if (can_castle(BLACK_OO)) + ss << (chess960 ? char('a' + file_of(castling_rook_square(BLACK | KING_SIDE))) : 'k'); + if (can_castle(BLACK_OOO)) + ss << (chess960 ? char('a' + file_of(castling_rook_square(BLACK | QUEEN_SIDE))) : 'q'); -/// Position:discovered_check_candidates() returns a bitboard containing all -/// pieces for the given side which are candidates for giving a discovered -/// check. Contrary to pinned_pieces() here there is no need of checkersBB -/// to be already updated. + if (!can_castle(WHITE) && !can_castle(BLACK)) + ss << '-'; -Bitboard Position::discovered_check_candidates(Color c) const { + ss << (ep_square() == SQ_NONE ? " - " : " " + UCI::square(ep_square()) + " ") + << st->rule50 << " " << 1 + (gamePly - (sideToMove == BLACK)) / 2; - return hidden_checkers(c); + return ss.str(); } -/// Position::attackers_to() computes a bitboard containing all pieces which -/// attacks a given square. -Bitboard Position::attackers_to(Square s) const { +/// Position::game_phase() calculates the game phase interpolating total non-pawn +/// material between endgame and midgame limits. - return (attacks_from(s, BLACK) & pieces(PAWN, WHITE)) - | (attacks_from(s, WHITE) & pieces(PAWN, BLACK)) - | (attacks_from(s) & pieces(KNIGHT)) - | (attacks_from(s) & pieces(ROOK, QUEEN)) - | (attacks_from(s) & pieces(BISHOP, QUEEN)) - | (attacks_from(s) & pieces(KING)); -} +Phase Position::game_phase() const { -/// Position::attacks_from() computes a bitboard of all attacks -/// of a given piece put in a given square. + Value npm = st->nonPawnMaterial[WHITE] + st->nonPawnMaterial[BLACK]; -Bitboard Position::attacks_from(Piece p, Square s) const { + npm = std::max(EndgameLimit, std::min(npm, MidgameLimit)); - assert(square_is_ok(s)); - - switch (p) - { - case WP: return attacks_from(s, WHITE); - case BP: return attacks_from(s, BLACK); - case WN: case BN: return attacks_from(s); - case WB: case BB: return attacks_from(s); - case WR: case BR: return attacks_from(s); - case WQ: case BQ: return attacks_from(s); - case WK: case BK: return attacks_from(s); - default: break; - } - return false; + return Phase(((npm - EndgameLimit) * PHASE_MIDGAME) / (MidgameLimit - EndgameLimit)); } -/// Position::move_attacks_square() tests whether a move from the current -/// position attacks a given square. - -bool Position::move_attacks_square(Move m, Square s) const { +/// Position::slider_blockers() returns a bitboard of all the pieces (both colors) +/// that are blocking attacks on the square 's' from 'sliders'. A piece blocks a +/// slider if removing that piece from the board would result in a position where +/// square 's' is attacked. For example, a king-attack blocking piece can be either +/// a pinned or a discovered check piece, according if its color is the opposite +/// or the same of the color of the slider. - assert(move_is_ok(m)); - assert(square_is_ok(s)); +Bitboard Position::slider_blockers(Bitboard sliders, Square s, Bitboard& pinners) const { - Square f = move_from(m), t = move_to(m); + Bitboard result = 0; + pinners = 0; - assert(square_is_occupied(f)); + // Snipers are sliders that attack 's' when a piece is removed + Bitboard snipers = ( (PseudoAttacks[ROOK ][s] & pieces(QUEEN, ROOK)) + | (PseudoAttacks[BISHOP][s] & pieces(QUEEN, BISHOP))) & sliders; - if (bit_is_set(attacks_from(piece_on(f), t), s)) - return true; + while (snipers) + { + Square sniperSq = pop_lsb(&snipers); + Bitboard b = between_bb(s, sniperSq) & pieces(); - // Move the piece and scan for X-ray attacks behind it - Bitboard occ = occupied_squares(); - Color us = color_of_piece_on(f); - clear_bit(&occ, f); - set_bit(&occ, t); - Bitboard xray = ( (rook_attacks_bb(s, occ) & pieces(ROOK, QUEEN)) - |(bishop_attacks_bb(s, occ) & pieces(BISHOP, QUEEN))) & pieces_of_color(us); - - // If we have attacks we need to verify that are caused by our move - // and are not already existent ones. - return xray && (xray ^ (xray & attacks_from(s))); + if (!more_than_one(b)) + { + result |= b; + if (b & pieces(color_of(piece_on(s)))) + pinners |= sniperSq; + } + } + return result; } -/// Position::find_checkers() computes the checkersBB bitboard, which -/// contains a nonzero bit for each checking piece (0, 1 or 2). It -/// currently works by calling Position::attackers_to, which is probably -/// inefficient. Consider rewriting this function to use the last move -/// played, like in non-bitboard versions of Glaurung. +/// Position::attackers_to() computes a bitboard of all pieces which attack a +/// given square. Slider attacks use the occupied bitboard to indicate occupancy. -void Position::find_checkers() { +Bitboard Position::attackers_to(Square s, Bitboard occupied) const { - Color us = side_to_move(); - st->checkersBB = attackers_to(king_square(us)) & pieces_of_color(opposite_color(us)); + return (attacks_from(s, BLACK) & pieces(WHITE, PAWN)) + | (attacks_from(s, WHITE) & pieces(BLACK, PAWN)) + | (attacks_from(s) & pieces(KNIGHT)) + | (attacks_bb(s, occupied) & pieces(ROOK, QUEEN)) + | (attacks_bb(s, occupied) & pieces(BISHOP, QUEEN)) + | (attacks_from(s) & pieces(KING)); } -/// Position::pl_move_is_legal() tests whether a pseudo-legal move is legal - -bool Position::pl_move_is_legal(Move m, Bitboard pinned) const { +/// Position::legal() tests whether a pseudo-legal move is legal - assert(is_ok()); - assert(move_is_ok(m)); - assert(pinned == pinned_pieces(side_to_move())); +bool Position::legal(Move m) const { - // Castling moves are checked for legality during move generation. - if (move_is_castle(m)) - return true; + assert(is_ok(m)); - Color us = side_to_move(); - Square from = move_from(m); + Color us = sideToMove; + Square from = from_sq(m); - assert(color_of_piece_on(from) == us); - assert(piece_on(king_square(us)) == piece_of_color_and_type(us, KING)); + assert(color_of(moved_piece(m)) == us); + assert(piece_on(square(us)) == make_piece(us, KING)); - // En passant captures are a tricky special case. Because they are - // rather uncommon, we do it simply by testing whether the king is attacked - // after the move is made - if (move_is_ep(m)) + // En passant captures are a tricky special case. Because they are rather + // uncommon, we do it simply by testing whether the king is attacked after + // the move is made. + if (type_of(m) == ENPASSANT) { - Color them = opposite_color(us); - Square to = move_to(m); - Square capsq = make_square(square_file(to), square_rank(from)); - Bitboard b = occupied_squares(); - Square ksq = king_square(us); + Square ksq = square(us); + Square to = to_sq(m); + Square capsq = to - pawn_push(us); + Bitboard occupied = (pieces() ^ from ^ capsq) | to; assert(to == ep_square()); - assert(piece_on(from) == piece_of_color_and_type(us, PAWN)); - assert(piece_on(capsq) == piece_of_color_and_type(them, PAWN)); - assert(piece_on(to) == EMPTY); + assert(moved_piece(m) == make_piece(us, PAWN)); + assert(piece_on(capsq) == make_piece(~us, PAWN)); + assert(piece_on(to) == NO_PIECE); - clear_bit(&b, from); - clear_bit(&b, capsq); - set_bit(&b, to); - - return !(rook_attacks_bb(ksq, b) & pieces(ROOK, QUEEN, them)) - && !(bishop_attacks_bb(ksq, b) & pieces(BISHOP, QUEEN, them)); + return !(attacks_bb< ROOK>(ksq, occupied) & pieces(~us, QUEEN, ROOK)) + && !(attacks_bb(ksq, occupied) & pieces(~us, QUEEN, BISHOP)); } // If the moving piece is a king, check whether the destination - // square is attacked by the opponent. - if (type_of_piece_on(from) == KING) - return !(attackers_to(move_to(m)) & pieces_of_color(opposite_color(us))); + // square is attacked by the opponent. Castling moves are checked + // for legality during move generation. + if (type_of(piece_on(from)) == KING) + return type_of(m) == CASTLING || !(attackers_to(to_sq(m)) & pieces(~us)); // A non-king move is legal if and only if it is not pinned or it // is moving along the ray towards or away from the king. - return ( !pinned - || !bit_is_set(pinned, from) - || (direction_between_squares(from, king_square(us)) == direction_between_squares(move_to(m), king_square(us)))); + return !(pinned_pieces(us) & from) + || aligned(from, to_sq(m), square(us)); } -/// Position::pl_move_is_evasion() tests whether a pseudo-legal move is a legal evasion +/// Position::pseudo_legal() takes a random move and tests whether the move is +/// pseudo legal. It is used to validate moves from TT that can be corrupted +/// due to SMP concurrent access or hash position key aliasing. -bool Position::pl_move_is_evasion(Move m, Bitboard pinned) const -{ - assert(is_check()); +bool Position::pseudo_legal(const Move m) const { - Color us = side_to_move(); - Square from = move_from(m); - Square to = move_to(m); + Color us = sideToMove; + Square from = from_sq(m); + Square to = to_sq(m); + Piece pc = moved_piece(m); - // King moves and en-passant captures are verified in pl_move_is_legal() - if (type_of_piece_on(from) == KING || move_is_ep(m)) - return pl_move_is_legal(m, pinned); + // Use a slower but simpler function for uncommon cases + if (type_of(m) != NORMAL) + return MoveList(*this).contains(m); - Bitboard target = checkers(); - Square checksq = pop_1st_bit(&target); + // Is not a promotion, so promotion piece must be empty + if (promotion_type(m) - KNIGHT != NO_PIECE_TYPE) + return false; - if (target) // double check ? + // If the 'from' square is not occupied by a piece belonging to the side to + // move, the move is obviously not legal. + if (pc == NO_PIECE || color_of(pc) != us) return false; - // Our move must be a blocking evasion or a capture of the checking piece - target = squares_between(checksq, king_square(us)) | checkers(); - return bit_is_set(target, to) && pl_move_is_legal(m, pinned); -} + // The destination square cannot be occupied by a friendly piece + if (pieces(us) & to) + return false; + // Handle the special case of a pawn move + if (type_of(pc) == PAWN) + { + // We have already handled promotion moves, so destination + // cannot be on the 8th/1st rank. + if (rank_of(to) == relative_rank(us, RANK_8)) + return false; -/// Position::move_is_check() tests whether a pseudo-legal move is a check + if ( !(attacks_from(from, us) & pieces(~us) & to) // Not a capture + && !((from + pawn_push(us) == to) && empty(to)) // Not a single push + && !( (from + 2 * pawn_push(us) == to) // Not a double push + && (rank_of(from) == relative_rank(us, RANK_2)) + && empty(to) + && empty(to - pawn_push(us)))) + return false; + } + else if (!(attacks_from(pc, from) & to)) + return false; -bool Position::move_is_check(Move m) const { + // Evasions generator already takes care to avoid some kind of illegal moves + // and legal() relies on this. We therefore have to take care that the same + // kind of moves are filtered out here. + if (checkers()) + { + if (type_of(pc) != KING) + { + // Double check? In this case a king move is required + if (more_than_one(checkers())) + return false; - return move_is_check(m, CheckInfo(*this)); + // Our move must be a blocking evasion or a capture of the checking piece + if (!((between_bb(lsb(checkers()), square(us)) | checkers()) & to)) + return false; + } + // In case of king moves under check we have to remove king so as to catch + // invalid moves like b1a1 when opposite queen is on c1. + else if (attackers_to(to, pieces() ^ from) & pieces(~us)) + return false; + } + + return true; } -bool Position::move_is_check(Move m, const CheckInfo& ci) const { - assert(is_ok()); - assert(move_is_ok(m)); - assert(ci.dcCandidates == discovered_check_candidates(side_to_move())); - assert(color_of_piece_on(move_from(m)) == side_to_move()); - assert(piece_on(ci.ksq) == piece_of_color_and_type(opposite_color(side_to_move()), KING)); +/// Position::gives_check() tests whether a pseudo-legal move gives a check - Square from = move_from(m); - Square to = move_to(m); - PieceType pt = type_of_piece_on(from); +bool Position::gives_check(Move m) const { - // Direct check ? - if (bit_is_set(ci.checkSq[pt], to)) - return true; + assert(is_ok(m)); + assert(color_of(moved_piece(m)) == sideToMove); - // Discovery check ? - if (ci.dcCandidates && bit_is_set(ci.dcCandidates, from)) - { - // For pawn and king moves we need to verify also direction - if ( (pt != PAWN && pt != KING) - ||(direction_between_squares(from, ci.ksq) != direction_between_squares(to, ci.ksq))) - return true; - } + Square from = from_sq(m); + Square to = to_sq(m); - // Can we skip the ugly special cases ? - if (!move_is_special(m)) - return false; + // Is there a direct check? + if (st->checkSquares[type_of(piece_on(from))] & to) + return true; - Color us = side_to_move(); - Bitboard b = occupied_squares(); + // Is there a discovered check? + if ( (discovered_check_candidates() & from) + && !aligned(from, to, square(~sideToMove))) + return true; - // Promotion with check ? - if (move_is_promotion(m)) + switch (type_of(m)) { - clear_bit(&b, from); + case NORMAL: + return false; - switch (move_promotion_piece(m)) - { - case KNIGHT: - return bit_is_set(attacks_from(to), ci.ksq); - case BISHOP: - return bit_is_set(bishop_attacks_bb(to, b), ci.ksq); - case ROOK: - return bit_is_set(rook_attacks_bb(to, b), ci.ksq); - case QUEEN: - return bit_is_set(queen_attacks_bb(to, b), ci.ksq); - default: - assert(false); - } - } + case PROMOTION: + return attacks_bb(Piece(promotion_type(m)), to, pieces() ^ from) & square(~sideToMove); - // En passant capture with check ? We have already handled the case - // of direct checks and ordinary discovered check, the only case we + // En passant capture with check? We have already handled the case + // of direct checks and ordinary discovered check, so the only case we // need to handle is the unusual case of a discovered check through // the captured pawn. - if (move_is_ep(m)) + case ENPASSANT: { - Square capsq = make_square(square_file(to), square_rank(from)); - clear_bit(&b, from); - clear_bit(&b, capsq); - set_bit(&b, to); - return (rook_attacks_bb(ci.ksq, b) & pieces(ROOK, QUEEN, us)) - ||(bishop_attacks_bb(ci.ksq, b) & pieces(BISHOP, QUEEN, us)); - } + Square capsq = make_square(file_of(to), rank_of(from)); + Bitboard b = (pieces() ^ from ^ capsq) | to; - // Castling with check ? - if (move_is_castle(m)) + return (attacks_bb< ROOK>(square(~sideToMove), b) & pieces(sideToMove, QUEEN, ROOK)) + | (attacks_bb(square(~sideToMove), b) & pieces(sideToMove, QUEEN, BISHOP)); + } + case CASTLING: { - Square kfrom, kto, rfrom, rto; - kfrom = from; - rfrom = to; + Square kfrom = from; + Square rfrom = to; // Castling is encoded as 'King captures the rook' + Square kto = relative_square(sideToMove, rfrom > kfrom ? SQ_G1 : SQ_C1); + Square rto = relative_square(sideToMove, rfrom > kfrom ? SQ_F1 : SQ_D1); - if (rfrom > kfrom) - { - kto = relative_square(us, SQ_G1); - rto = relative_square(us, SQ_F1); - } else { - kto = relative_square(us, SQ_C1); - rto = relative_square(us, SQ_D1); - } - clear_bit(&b, kfrom); - clear_bit(&b, rfrom); - set_bit(&b, rto); - set_bit(&b, kto); - return bit_is_set(rook_attacks_bb(rto, b), ci.ksq); + return (PseudoAttacks[ROOK][rto] & square(~sideToMove)) + && (attacks_bb(rto, (pieces() ^ kfrom ^ rfrom) | rto | kto) & square(~sideToMove)); + } + default: + assert(false); + return false; } - - return false; } /// Position::do_move() makes a move, and saves all information necessary -/// to a StateInfo object. The move is assumed to be legal. -/// Pseudo-legal moves should be filtered out before this function is called. +/// to a StateInfo object. The move is assumed to be legal. Pseudo-legal +/// moves should be filtered out before this function is called. -void Position::do_move(Move m, StateInfo& newSt) { - - CheckInfo ci(*this); - do_move(m, newSt, ci, move_is_check(m, ci)); -} +void Position::do_move(Move m, StateInfo& newSt, bool givesCheck) { -void Position::do_move(Move m, StateInfo& newSt, const CheckInfo& ci, bool moveIsCheck) { + assert(is_ok(m)); + assert(&newSt != st); - assert(is_ok()); - assert(move_is_ok(m)); + ++nodes; + Key k = st->key ^ Zobrist::side; - Key key = st->key; - - // Copy some fields of old state to our new StateInfo object except the - // ones which are recalculated from scratch anyway, then switch our state - // pointer to point to the new, ready to be updated, state. - struct ReducedStateInfo { - Key pawnKey, materialKey; - int castleRights, rule50, gamePly, pliesFromNull; - Square epSquare; - Score value; - Value npMaterial[2]; - }; - - memcpy(&newSt, st, sizeof(ReducedStateInfo)); + // Copy some fields of the old state to our new StateInfo object except the + // ones which are going to be recalculated from scratch anyway and then switch + // our state pointer to point to the new (ready to be updated) state. + std::memcpy(&newSt, st, offsetof(StateInfo, key)); newSt.previous = st; st = &newSt; - // Save the current key to the history[] array, in order to be able to - // detect repetition draws. - history[st->gamePly++] = key; + // Increment ply counters. In particular, rule50 will be reset to zero later on + // in case of a capture or a pawn move. + ++gamePly; + ++st->rule50; + ++st->pliesFromNull; - // Update side to move - key ^= zobSideToMove; + Color us = sideToMove; + Color them = ~us; + Square from = from_sq(m); + Square to = to_sq(m); + Piece pc = piece_on(from); + Piece captured = type_of(m) == ENPASSANT ? make_piece(them, PAWN) : piece_on(to); - // Increment the 50 moves rule draw counter. Resetting it to zero in the - // case of non-reversible moves is taken care of later. - st->rule50++; - st->pliesFromNull++; + assert(color_of(pc) == us); + assert(captured == NO_PIECE || color_of(captured) == (type_of(m) != CASTLING ? them : us)); + assert(type_of(captured) != KING); - if (move_is_castle(m)) + if (type_of(m) == CASTLING) { - st->key = key; - do_castle_move(m); - return; - } - - Color us = side_to_move(); - Color them = opposite_color(us); - Square from = move_from(m); - Square to = move_to(m); - bool ep = move_is_ep(m); - bool pm = move_is_promotion(m); - - Piece piece = piece_on(from); - PieceType pt = type_of_piece(piece); - PieceType capture = ep ? PAWN : type_of_piece_on(to); - - assert(color_of_piece_on(from) == us); - assert(color_of_piece_on(to) == them || square_is_empty(to)); - assert(!(ep || pm) || piece == piece_of_color_and_type(us, PAWN)); - assert(!pm || relative_rank(us, to) == RANK_8); - - if (capture) - do_capture_move(key, capture, them, to, ep); - - // Update hash key - key ^= zobrist[us][pt][from] ^ zobrist[us][pt][to]; + assert(pc == make_piece(us, KING)); + assert(captured == make_piece(us, ROOK)); - // Reset en passant square - if (st->epSquare != SQ_NONE) - { - key ^= zobEp[st->epSquare]; - st->epSquare = SQ_NONE; - } + Square rfrom, rto; + do_castling(us, from, to, rfrom, rto); - // Update castle rights, try to shortcut a common case - int cm = castleRightsMask[from] & castleRightsMask[to]; - if (cm != ALL_CASTLES && ((cm & st->castleRights) != st->castleRights)) - { - key ^= zobCastle[st->castleRights]; - st->castleRights &= castleRightsMask[from]; - st->castleRights &= castleRightsMask[to]; - key ^= zobCastle[st->castleRights]; + st->psq += PSQT::psq[captured][rto] - PSQT::psq[captured][rfrom]; + k ^= Zobrist::psq[captured][rfrom] ^ Zobrist::psq[captured][rto]; + captured = NO_PIECE; } - // Prefetch TT access as soon as we know key is updated - prefetch((char*)TT.first_entry(key)); - - // Move the piece - Bitboard move_bb = make_move_bb(from, to); - do_move_bb(&(byColorBB[us]), move_bb); - do_move_bb(&(byTypeBB[pt]), move_bb); - do_move_bb(&(byTypeBB[0]), move_bb); // HACK: byTypeBB[0] == occupied squares - - board[to] = board[from]; - board[from] = EMPTY; - - // Update piece lists, note that index[from] is not updated and - // becomes stale. This works as long as index[] is accessed just - // by known occupied squares. - index[to] = index[from]; - pieceList[us][pt][index[to]] = to; - - // If the moving piece was a pawn do some special extra work - if (pt == PAWN) + if (captured) { - // Reset rule 50 draw counter - st->rule50 = 0; - - // Update pawn hash key - st->pawnKey ^= zobrist[us][PAWN][from] ^ zobrist[us][PAWN][to]; + Square capsq = to; - // Set en passant square, only if moved pawn can be captured - if ((to ^ from) == 16) + // If the captured piece is a pawn, update pawn hash key, otherwise + // update non-pawn material. + if (type_of(captured) == PAWN) { - if (attacks_from(from + (us == WHITE ? DELTA_N : DELTA_S), us) & pieces(PAWN, them)) + if (type_of(m) == ENPASSANT) { - st->epSquare = Square((int(from) + int(to)) / 2); - key ^= zobEp[st->epSquare]; - } - } - - if (pm) // promotion ? - { - PieceType promotion = move_promotion_piece(m); + capsq -= pawn_push(us); - assert(promotion >= KNIGHT && promotion <= QUEEN); + assert(pc == make_piece(us, PAWN)); + assert(to == st->epSquare); + assert(relative_rank(us, to) == RANK_6); + assert(piece_on(to) == NO_PIECE); + assert(piece_on(capsq) == make_piece(them, PAWN)); - // Insert promoted piece instead of pawn - clear_bit(&(byTypeBB[PAWN]), to); - set_bit(&(byTypeBB[promotion]), to); - board[to] = piece_of_color_and_type(us, promotion); - - // Update piece counts - pieceCount[us][promotion]++; - pieceCount[us][PAWN]--; + board[capsq] = NO_PIECE; // Not done by remove_piece() + } - // Update material key - st->materialKey ^= zobrist[us][PAWN][pieceCount[us][PAWN]]; - st->materialKey ^= zobrist[us][promotion][pieceCount[us][promotion]-1]; + st->pawnKey ^= Zobrist::psq[captured][capsq]; + } + else + st->nonPawnMaterial[them] -= PieceValue[MG][captured]; - // Update piece lists, move the last pawn at index[to] position - // and shrink the list. Add a new promotion piece to the list. - Square lastPawnSquare = pieceList[us][PAWN][pieceCount[us][PAWN]]; - index[lastPawnSquare] = index[to]; - pieceList[us][PAWN][index[lastPawnSquare]] = lastPawnSquare; - pieceList[us][PAWN][pieceCount[us][PAWN]] = SQ_NONE; - index[to] = pieceCount[us][promotion] - 1; - pieceList[us][promotion][index[to]] = to; + // Update board and piece lists + remove_piece(captured, capsq); - // Partially revert hash keys update - key ^= zobrist[us][PAWN][to] ^ zobrist[us][promotion][to]; - st->pawnKey ^= zobrist[us][PAWN][to]; + // Update material hash key and prefetch access to materialTable + k ^= Zobrist::psq[captured][capsq]; + st->materialKey ^= Zobrist::psq[captured][pieceCount[captured]]; + prefetch(thisThread->materialTable[st->materialKey]); - // Partially revert and update incremental scores - st->value -= pst(us, PAWN, to); - st->value += pst(us, promotion, to); + // Update incremental scores + st->psq -= PSQT::psq[captured][capsq]; - // Update material - st->npMaterial[us] += piece_value_midgame(promotion); - } + // Reset rule 50 counter + st->rule50 = 0; } - // Update incremental scores - st->value += pst_delta(piece, from, to); + // Update hash key + k ^= Zobrist::psq[pc][from] ^ Zobrist::psq[pc][to]; - // Set capture piece - st->capture = capture; + // Reset en passant square + if (st->epSquare != SQ_NONE) + { + k ^= Zobrist::enpassant[file_of(st->epSquare)]; + st->epSquare = SQ_NONE; + } - // Update the key with the final value - st->key = key; + // Update castling rights if needed + if (st->castlingRights && (castlingRightsMask[from] | castlingRightsMask[to])) + { + int cr = castlingRightsMask[from] | castlingRightsMask[to]; + k ^= Zobrist::castling[st->castlingRights & cr]; + st->castlingRights &= ~cr; + } - // Update checkers bitboard, piece must be already moved - st->checkersBB = EmptyBoardBB; + // Move the piece. The tricky Chess960 castling is handled earlier + if (type_of(m) != CASTLING) + move_piece(pc, from, to); - if (moveIsCheck) + // If the moving piece is a pawn do some special extra work + if (type_of(pc) == PAWN) { - if (ep | pm) - st->checkersBB = attackers_to(king_square(them)) & pieces_of_color(us); - else + // Set en-passant square if the moved pawn can be captured + if ( (int(to) ^ int(from)) == 16 + && (attacks_from(to - pawn_push(us), us) & pieces(them, PAWN))) { - // Direct checks - if (bit_is_set(ci.checkSq[pt], to)) - st->checkersBB = SetMaskBB[to]; - - // Discovery checks - if (ci.dcCandidates && bit_is_set(ci.dcCandidates, from)) - { - if (pt != ROOK) - st->checkersBB |= (attacks_from(ci.ksq) & pieces(ROOK, QUEEN, us)); - - if (pt != BISHOP) - st->checkersBB |= (attacks_from(ci.ksq) & pieces(BISHOP, QUEEN, us)); - } + st->epSquare = (from + to) / 2; + k ^= Zobrist::enpassant[file_of(st->epSquare)]; } - } - - // Finish - sideToMove = opposite_color(sideToMove); - st->value += (sideToMove == WHITE ? TempoValue : -TempoValue); - - assert(is_ok()); -} - - -/// Position::do_capture_move() is a private method used to update captured -/// piece info. It is called from the main Position::do_move function. - -void Position::do_capture_move(Key& key, PieceType capture, Color them, Square to, bool ep) { - - assert(capture != KING); - - Square capsq = to; - - // If the captured piece was a pawn, update pawn hash key, - // otherwise update non-pawn material. - if (capture == PAWN) - { - if (ep) // en passant ? - { - capsq = (them == BLACK)? (to - DELTA_N) : (to - DELTA_S); - - assert(to == st->epSquare); - assert(relative_rank(opposite_color(them), to) == RANK_6); - assert(piece_on(to) == EMPTY); - assert(piece_on(capsq) == piece_of_color_and_type(them, PAWN)); - - board[capsq] = EMPTY; - } - st->pawnKey ^= zobrist[them][PAWN][capsq]; - } - else - st->npMaterial[them] -= piece_value_midgame(capture); - - // Remove captured piece - clear_bit(&(byColorBB[them]), capsq); - clear_bit(&(byTypeBB[capture]), capsq); - clear_bit(&(byTypeBB[0]), capsq); - - // Update hash key - key ^= zobrist[them][capture][capsq]; - - // Update incremental scores - st->value -= pst(them, capture, capsq); - - // Update piece count - pieceCount[them][capture]--; - - // Update material hash key - st->materialKey ^= zobrist[them][capture][pieceCount[them][capture]]; - - // Update piece list, move the last piece at index[capsq] position - // - // WARNING: This is a not perfectly revresible operation. When we - // will reinsert the captured piece in undo_move() we will put it - // at the end of the list and not in its original place, it means - // index[] and pieceList[] are not guaranteed to be invariant to a - // do_move() + undo_move() sequence. - Square lastPieceSquare = pieceList[them][capture][pieceCount[them][capture]]; - index[lastPieceSquare] = index[capsq]; - pieceList[them][capture][index[lastPieceSquare]] = lastPieceSquare; - pieceList[them][capture][pieceCount[them][capture]] = SQ_NONE; - - // Reset rule 50 counter - st->rule50 = 0; -} + else if (type_of(m) == PROMOTION) + { + Piece promotion = make_piece(us, promotion_type(m)); -/// Position::do_castle_move() is a private method used to make a castling -/// move. It is called from the main Position::do_move function. Note that -/// castling moves are encoded as "king captures friendly rook" moves, for -/// instance white short castling in a non-Chess960 game is encoded as e1h1. - -void Position::do_castle_move(Move m) { + assert(relative_rank(us, to) == RANK_8); + assert(type_of(promotion) >= KNIGHT && type_of(promotion) <= QUEEN); - assert(move_is_ok(m)); - assert(move_is_castle(m)); + remove_piece(pc, to); + put_piece(promotion, to); - Color us = side_to_move(); - Color them = opposite_color(us); + // Update hash keys + k ^= Zobrist::psq[pc][to] ^ Zobrist::psq[promotion][to]; + st->pawnKey ^= Zobrist::psq[pc][to]; + st->materialKey ^= Zobrist::psq[promotion][pieceCount[promotion]-1] + ^ Zobrist::psq[pc][pieceCount[pc]]; - // Reset capture field - st->capture = NO_PIECE_TYPE; + // Update incremental score + st->psq += PSQT::psq[promotion][to] - PSQT::psq[pc][to]; - // Find source squares for king and rook - Square kfrom = move_from(m); - Square rfrom = move_to(m); // HACK: See comment at beginning of function - Square kto, rto; + // Update material + st->nonPawnMaterial[us] += PieceValue[MG][promotion]; + } - assert(piece_on(kfrom) == piece_of_color_and_type(us, KING)); - assert(piece_on(rfrom) == piece_of_color_and_type(us, ROOK)); + // Update pawn hash key and prefetch access to pawnsTable + st->pawnKey ^= Zobrist::psq[pc][from] ^ Zobrist::psq[pc][to]; + prefetch(thisThread->pawnsTable[st->pawnKey]); - // Find destination squares for king and rook - if (rfrom > kfrom) // O-O - { - kto = relative_square(us, SQ_G1); - rto = relative_square(us, SQ_F1); - } else { // O-O-O - kto = relative_square(us, SQ_C1); - rto = relative_square(us, SQ_D1); + // Reset rule 50 draw counter + st->rule50 = 0; } - // Remove pieces from source squares: - clear_bit(&(byColorBB[us]), kfrom); - clear_bit(&(byTypeBB[KING]), kfrom); - clear_bit(&(byTypeBB[0]), kfrom); // HACK: byTypeBB[0] == occupied squares - clear_bit(&(byColorBB[us]), rfrom); - clear_bit(&(byTypeBB[ROOK]), rfrom); - clear_bit(&(byTypeBB[0]), rfrom); // HACK: byTypeBB[0] == occupied squares - - // Put pieces on destination squares: - set_bit(&(byColorBB[us]), kto); - set_bit(&(byTypeBB[KING]), kto); - set_bit(&(byTypeBB[0]), kto); // HACK: byTypeBB[0] == occupied squares - set_bit(&(byColorBB[us]), rto); - set_bit(&(byTypeBB[ROOK]), rto); - set_bit(&(byTypeBB[0]), rto); // HACK: byTypeBB[0] == occupied squares - - // Update board array - Piece king = piece_of_color_and_type(us, KING); - Piece rook = piece_of_color_and_type(us, ROOK); - board[kfrom] = board[rfrom] = EMPTY; - board[kto] = king; - board[rto] = rook; - - // Update piece lists - pieceList[us][KING][index[kfrom]] = kto; - pieceList[us][ROOK][index[rfrom]] = rto; - int tmp = index[rfrom]; // In Chess960 could be rto == kfrom - index[kto] = index[kfrom]; - index[rto] = tmp; - // Update incremental scores - st->value += pst_delta(king, kfrom, kto); - st->value += pst_delta(rook, rfrom, rto); - - // Update hash key - st->key ^= zobrist[us][KING][kfrom] ^ zobrist[us][KING][kto]; - st->key ^= zobrist[us][ROOK][rfrom] ^ zobrist[us][ROOK][rto]; + st->psq += PSQT::psq[pc][to] - PSQT::psq[pc][from]; - // Clear en passant square - if (st->epSquare != SQ_NONE) - { - st->key ^= zobEp[st->epSquare]; - st->epSquare = SQ_NONE; - } + // Set capture piece + st->capturedPiece = captured; - // Update castling rights - st->key ^= zobCastle[st->castleRights]; - st->castleRights &= castleRightsMask[kfrom]; - st->key ^= zobCastle[st->castleRights]; + // Update the key with the final value + st->key = k; - // Reset rule 50 counter - st->rule50 = 0; + // Calculate checkers bitboard (if move gives check) + st->checkersBB = givesCheck ? attackers_to(square(them)) & pieces(us) : 0; - // Update checkers BB - st->checkersBB = attackers_to(king_square(them)) & pieces_of_color(us); + sideToMove = ~sideToMove; - // Finish - sideToMove = opposite_color(sideToMove); - st->value += (sideToMove == WHITE ? TempoValue : -TempoValue); + // Update king attacks used for fast check detection + set_check_info(st); - assert(is_ok()); + assert(pos_is_ok()); } @@ -1098,954 +818,351 @@ void Position::do_castle_move(Move m) { void Position::undo_move(Move m) { - assert(is_ok()); - assert(move_is_ok(m)); + assert(is_ok(m)); - sideToMove = opposite_color(sideToMove); + sideToMove = ~sideToMove; - if (move_is_castle(m)) - { - undo_castle_move(m); - return; - } + Color us = sideToMove; + Square from = from_sq(m); + Square to = to_sq(m); + Piece pc = piece_on(to); - Color us = side_to_move(); - Color them = opposite_color(us); - Square from = move_from(m); - Square to = move_to(m); - bool ep = move_is_ep(m); - bool pm = move_is_promotion(m); + assert(empty(from) || type_of(m) == CASTLING); + assert(type_of(st->capturedPiece) != KING); - PieceType pt = type_of_piece_on(to); + if (type_of(m) == PROMOTION) + { + assert(relative_rank(us, to) == RANK_8); + assert(type_of(pc) == promotion_type(m)); + assert(type_of(pc) >= KNIGHT && type_of(pc) <= QUEEN); - assert(square_is_empty(from)); - assert(color_of_piece_on(to) == us); - assert(!pm || relative_rank(us, to) == RANK_8); - assert(!ep || to == st->previous->epSquare); - assert(!ep || relative_rank(us, to) == RANK_6); - assert(!ep || piece_on(to) == piece_of_color_and_type(us, PAWN)); + remove_piece(pc, to); + pc = make_piece(us, PAWN); + put_piece(pc, to); + } - if (pm) // promotion ? + if (type_of(m) == CASTLING) { - PieceType promotion = move_promotion_piece(m); - pt = PAWN; - - assert(promotion >= KNIGHT && promotion <= QUEEN); - assert(piece_on(to) == piece_of_color_and_type(us, promotion)); - - // Replace promoted piece with a pawn - clear_bit(&(byTypeBB[promotion]), to); - set_bit(&(byTypeBB[PAWN]), to); - - // Update piece counts - pieceCount[us][promotion]--; - pieceCount[us][PAWN]++; - - // Update piece list replacing promotion piece with a pawn - Square lastPromotionSquare = pieceList[us][promotion][pieceCount[us][promotion]]; - index[lastPromotionSquare] = index[to]; - pieceList[us][promotion][index[lastPromotionSquare]] = lastPromotionSquare; - pieceList[us][promotion][pieceCount[us][promotion]] = SQ_NONE; - index[to] = pieceCount[us][PAWN] - 1; - pieceList[us][PAWN][index[to]] = to; + Square rfrom, rto; + do_castling(us, from, to, rfrom, rto); } - - // Put the piece back at the source square - Bitboard move_bb = make_move_bb(to, from); - do_move_bb(&(byColorBB[us]), move_bb); - do_move_bb(&(byTypeBB[pt]), move_bb); - do_move_bb(&(byTypeBB[0]), move_bb); // HACK: byTypeBB[0] == occupied squares - - board[from] = piece_of_color_and_type(us, pt); - board[to] = EMPTY; - - // Update piece list - index[from] = index[to]; - pieceList[us][pt][index[from]] = from; - - if (st->capture) + else { - Square capsq = to; - - if (ep) - capsq = (us == WHITE)? (to - DELTA_N) : (to - DELTA_S); + move_piece(pc, to, from); // Put the piece back at the source square - assert(st->capture != KING); - assert(!ep || square_is_empty(capsq)); - - // Restore the captured piece - set_bit(&(byColorBB[them]), capsq); - set_bit(&(byTypeBB[st->capture]), capsq); - set_bit(&(byTypeBB[0]), capsq); + if (st->capturedPiece) + { + Square capsq = to; - board[capsq] = piece_of_color_and_type(them, st->capture); + if (type_of(m) == ENPASSANT) + { + capsq -= pawn_push(us); - // Update piece count - pieceCount[them][st->capture]++; + assert(type_of(pc) == PAWN); + assert(to == st->previous->epSquare); + assert(relative_rank(us, to) == RANK_6); + assert(piece_on(capsq) == NO_PIECE); + assert(st->capturedPiece == make_piece(~us, PAWN)); + } - // Update piece list, add a new captured piece in capsq square - index[capsq] = pieceCount[them][st->capture] - 1; - pieceList[them][st->capture][index[capsq]] = capsq; + put_piece(st->capturedPiece, capsq); // Restore the captured piece + } } // Finally point our state pointer back to the previous state st = st->previous; + --gamePly; - assert(is_ok()); + assert(pos_is_ok()); } -/// Position::undo_castle_move() is a private method used to unmake a castling -/// move. It is called from the main Position::undo_move function. Note that -/// castling moves are encoded as "king captures friendly rook" moves, for -/// instance white short castling in a non-Chess960 game is encoded as e1h1. - -void Position::undo_castle_move(Move m) { - - assert(move_is_ok(m)); - assert(move_is_castle(m)); +/// Position::do_castling() is a helper used to do/undo a castling move. This +/// is a bit tricky in Chess960 where from/to squares can overlap. +template +void Position::do_castling(Color us, Square from, Square& to, Square& rfrom, Square& rto) { - // When we have arrived here, some work has already been done by - // Position::undo_move. In particular, the side to move has been switched, - // so the code below is correct. - Color us = side_to_move(); + bool kingSide = to > from; + rfrom = to; // Castling is encoded as "king captures friendly rook" + rto = relative_square(us, kingSide ? SQ_F1 : SQ_D1); + to = relative_square(us, kingSide ? SQ_G1 : SQ_C1); - // Find source squares for king and rook - Square kfrom = move_from(m); - Square rfrom = move_to(m); // HACK: See comment at beginning of function - Square kto, rto; - - // Find destination squares for king and rook - if (rfrom > kfrom) // O-O - { - kto = relative_square(us, SQ_G1); - rto = relative_square(us, SQ_F1); - } else { // O-O-O - kto = relative_square(us, SQ_C1); - rto = relative_square(us, SQ_D1); - } - - assert(piece_on(kto) == piece_of_color_and_type(us, KING)); - assert(piece_on(rto) == piece_of_color_and_type(us, ROOK)); - - // Remove pieces from destination squares: - clear_bit(&(byColorBB[us]), kto); - clear_bit(&(byTypeBB[KING]), kto); - clear_bit(&(byTypeBB[0]), kto); // HACK: byTypeBB[0] == occupied squares - clear_bit(&(byColorBB[us]), rto); - clear_bit(&(byTypeBB[ROOK]), rto); - clear_bit(&(byTypeBB[0]), rto); // HACK: byTypeBB[0] == occupied squares - - // Put pieces on source squares: - set_bit(&(byColorBB[us]), kfrom); - set_bit(&(byTypeBB[KING]), kfrom); - set_bit(&(byTypeBB[0]), kfrom); // HACK: byTypeBB[0] == occupied squares - set_bit(&(byColorBB[us]), rfrom); - set_bit(&(byTypeBB[ROOK]), rfrom); - set_bit(&(byTypeBB[0]), rfrom); // HACK: byTypeBB[0] == occupied squares - - // Update board - board[rto] = board[kto] = EMPTY; - board[rfrom] = piece_of_color_and_type(us, ROOK); - board[kfrom] = piece_of_color_and_type(us, KING); - - // Update piece lists - pieceList[us][KING][index[kto]] = kfrom; - pieceList[us][ROOK][index[rto]] = rfrom; - int tmp = index[rto]; // In Chess960 could be rto == kfrom - index[kfrom] = index[kto]; - index[rfrom] = tmp; - - // Finally point our state pointer back to the previous state - st = st->previous; - - assert(is_ok()); + // Remove both pieces first since squares could overlap in Chess960 + remove_piece(make_piece(us, KING), Do ? from : to); + remove_piece(make_piece(us, ROOK), Do ? rfrom : rto); + board[Do ? from : to] = board[Do ? rfrom : rto] = NO_PIECE; // Since remove_piece doesn't do it for us + put_piece(make_piece(us, KING), Do ? to : from); + put_piece(make_piece(us, ROOK), Do ? rto : rfrom); } -/// Position::do_null_move makes() a "null move": It switches the side to move -/// and updates the hash key without executing any move on the board. - -void Position::do_null_move(StateInfo& backupSt) { +/// Position::do(undo)_null_move() is used to do(undo) a "null move": It flips +/// the side to move without executing any move on the board. - assert(is_ok()); - assert(!is_check()); +void Position::do_null_move(StateInfo& newSt) { - // Back up the information necessary to undo the null move to the supplied - // StateInfo object. - // Note that differently from normal case here backupSt is actually used as - // a backup storage not as a new state to be used. - backupSt.key = st->key; - backupSt.epSquare = st->epSquare; - backupSt.value = st->value; - backupSt.previous = st->previous; - backupSt.pliesFromNull = st->pliesFromNull; - st->previous = &backupSt; + assert(!checkers()); + assert(&newSt != st); - // Save the current key to the history[] array, in order to be able to - // detect repetition draws. - history[st->gamePly++] = st->key; + std::memcpy(&newSt, st, sizeof(StateInfo)); + newSt.previous = st; + st = &newSt; - // Update the necessary information if (st->epSquare != SQ_NONE) - st->key ^= zobEp[st->epSquare]; + { + st->key ^= Zobrist::enpassant[file_of(st->epSquare)]; + st->epSquare = SQ_NONE; + } - st->key ^= zobSideToMove; - prefetch((char*)TT.first_entry(st->key)); + st->key ^= Zobrist::side; + prefetch(TT.first_entry(st->key)); - sideToMove = opposite_color(sideToMove); - st->epSquare = SQ_NONE; - st->rule50++; + ++st->rule50; st->pliesFromNull = 0; - st->value += (sideToMove == WHITE) ? TempoValue : -TempoValue; -} - -/// Position::undo_null_move() unmakes a "null move". + sideToMove = ~sideToMove; -void Position::undo_null_move() { + set_check_info(st); - assert(is_ok()); - assert(!is_check()); - - // Restore information from the our backup StateInfo object - StateInfo* backupSt = st->previous; - st->key = backupSt->key; - st->epSquare = backupSt->epSquare; - st->value = backupSt->value; - st->previous = backupSt->previous; - st->pliesFromNull = backupSt->pliesFromNull; - - // Update the necessary information - sideToMove = opposite_color(sideToMove); - st->rule50--; - st->gamePly--; + assert(pos_is_ok()); } +void Position::undo_null_move() { -/// Position::see() is a static exchange evaluator: It tries to estimate the -/// material gain or loss resulting from a move. There are three versions of -/// this function: One which takes a destination square as input, one takes a -/// move, and one which takes a 'from' and a 'to' square. The function does -/// not yet understand promotions captures. - -int Position::see(Square to) const { + assert(!checkers()); - assert(square_is_ok(to)); - return see(SQ_NONE, to); + st = st->previous; + sideToMove = ~sideToMove; } -int Position::see(Move m) const { - assert(move_is_ok(m)); - return see(move_from(m), move_to(m)); -} - -int Position::see_sign(Move m) const { +/// Position::key_after() computes the new hash key after the given move. Needed +/// for speculative prefetch. It doesn't recognize special moves like castling, +/// en-passant and promotions. - assert(move_is_ok(m)); +Key Position::key_after(Move m) const { - Square from = move_from(m); - Square to = move_to(m); + Square from = from_sq(m); + Square to = to_sq(m); + Piece pc = piece_on(from); + Piece captured = piece_on(to); + Key k = st->key ^ Zobrist::side; - // Early return if SEE cannot be negative because captured piece value - // is not less then capturing one. Note that king moves always return - // here because king midgame value is set to 0. - if (midgame_value_of_piece_on(to) >= midgame_value_of_piece_on(from)) - return 1; + if (captured) + k ^= Zobrist::psq[captured][to]; - return see(from, to); + return k ^ Zobrist::psq[pc][to] ^ Zobrist::psq[pc][from]; } -int Position::see(Square from, Square to) const { - // Material values - static const int seeValues[18] = { - 0, PawnValueMidgame, KnightValueMidgame, BishopValueMidgame, - RookValueMidgame, QueenValueMidgame, QueenValueMidgame*10, 0, - 0, PawnValueMidgame, KnightValueMidgame, BishopValueMidgame, - RookValueMidgame, QueenValueMidgame, QueenValueMidgame*10, 0, - 0, 0 - }; +/// Position::see_ge (Static Exchange Evaluation Greater or Equal) tests if the +/// SEE value of move is greater or equal to the given value. We'll use an +/// algorithm similar to alpha-beta pruning with a null window. - Bitboard attackers, stmAttackers, b; +bool Position::see_ge(Move m, Value v) const { - assert(square_is_ok(from) || from == SQ_NONE); - assert(square_is_ok(to)); + assert(is_ok(m)); - // Initialize colors - Color us = (from != SQ_NONE ? color_of_piece_on(from) : opposite_color(color_of_piece_on(to))); - Color them = opposite_color(us); + // Castling moves are implemented as king capturing the rook so cannot be + // handled correctly. Simply assume the SEE value is VALUE_ZERO that is always + // correct unless in the rare case the rook ends up under attack. + if (type_of(m) == CASTLING) + return VALUE_ZERO >= v; - // Initialize pieces - Piece piece = piece_on(from); - Piece capture = piece_on(to); - Bitboard occ = occupied_squares(); + Square from = from_sq(m), to = to_sq(m); + PieceType nextVictim = type_of(piece_on(from)); + Color stm = ~color_of(piece_on(from)); // First consider opponent's move + Value balance; // Values of the pieces taken by us minus opponent's ones + Bitboard occupied, stmAttackers; - // King cannot be recaptured - if (type_of_piece(piece) == KING) - return seeValues[capture]; - - // Handle en passant moves - if (st->epSquare == to && type_of_piece_on(from) == PAWN) + if (type_of(m) == ENPASSANT) { - assert(capture == EMPTY); - - Square capQq = (side_to_move() == WHITE)? (to - DELTA_N) : (to - DELTA_S); - capture = piece_on(capQq); - assert(type_of_piece_on(capQq) == PAWN); - - // Remove the captured pawn - clear_bit(&occ, capQq); + occupied = SquareBB[to - pawn_push(~stm)]; // Remove the captured pawn + balance = PieceValue[MG][PAWN]; } - - while (true) + else { - // Find all attackers to the destination square, with the moving piece - // removed, but possibly an X-ray attacker added behind it. - clear_bit(&occ, from); - attackers = (rook_attacks_bb(to, occ) & pieces(ROOK, QUEEN)) - | (bishop_attacks_bb(to, occ) & pieces(BISHOP, QUEEN)) - | (attacks_from(to) & pieces(KNIGHT)) - | (attacks_from(to) & pieces(KING)) - | (attacks_from(to, WHITE) & pieces(PAWN, BLACK)) - | (attacks_from(to, BLACK) & pieces(PAWN, WHITE)); - - if (from != SQ_NONE) - break; - - // If we don't have any attacker we are finished - if ((attackers & pieces_of_color(us)) == EmptyBoardBB) - return 0; - - // Locate the least valuable attacker to the destination square - // and use it to initialize from square. - stmAttackers = attackers & pieces_of_color(us); - PieceType pt; - for (pt = PAWN; !(stmAttackers & pieces(pt)); pt++) - assert(pt < KING); - - from = first_1(stmAttackers & pieces(pt)); - piece = piece_on(from); + balance = PieceValue[MG][piece_on(to)]; + occupied = 0; } - // If the opponent has no attackers we are finished - stmAttackers = attackers & pieces_of_color(them); - if (!stmAttackers) - return seeValues[capture]; - - attackers &= occ; // Remove the moving piece - - // The destination square is defended, which makes things rather more - // difficult to compute. We proceed by building up a "swap list" containing - // the material gain or loss at each stop in a sequence of captures to the - // destination square, where the sides alternately capture, and always - // capture with the least valuable piece. After each capture, we look for - // new X-ray attacks from behind the capturing piece. - int lastCapturingPieceValue = seeValues[piece]; - int swapList[32], n = 1; - Color c = them; - PieceType pt; - - swapList[0] = seeValues[capture]; - - do { - // Locate the least valuable attacker for the side to move. The loop - // below looks like it is potentially infinite, but it isn't. We know - // that the side to move still has at least one attacker left. - for (pt = PAWN; !(stmAttackers & pieces(pt)); pt++) - assert(pt < KING); - - // Remove the attacker we just found from the 'attackers' bitboard, - // and scan for new X-ray attacks behind the attacker. - b = stmAttackers & pieces(pt); - occ ^= (b & (~b + 1)); - attackers |= (rook_attacks_bb(to, occ) & pieces(ROOK, QUEEN)) - | (bishop_attacks_bb(to, occ) & pieces(BISHOP, QUEEN)); - - attackers &= occ; - - // Add the new entry to the swap list - assert(n < 32); - swapList[n] = -swapList[n - 1] + lastCapturingPieceValue; - n++; - - // Remember the value of the capturing piece, and change the side to move - // before beginning the next iteration - lastCapturingPieceValue = seeValues[pt]; - c = opposite_color(c); - stmAttackers = attackers & pieces_of_color(c); - - // Stop after a king capture - if (pt == KING && stmAttackers) - { - assert(n < 32); - swapList[n++] = QueenValueMidgame*10; - break; - } - } while (stmAttackers); - - // Having built the swap list, we negamax through it to find the best - // achievable score from the point of view of the side to move - while (--n) - swapList[n-1] = Min(-swapList[n], swapList[n-1]); - - return swapList[0]; -} - - -/// Position::clear() erases the position object to a pristine state, with an -/// empty board, white to move, and no castling rights. - -void Position::clear() { - - st = &startState; - memset(st, 0, sizeof(StateInfo)); - st->epSquare = SQ_NONE; - - memset(byColorBB, 0, sizeof(Bitboard) * 2); - memset(byTypeBB, 0, sizeof(Bitboard) * 8); - memset(pieceCount, 0, sizeof(int) * 2 * 8); - memset(index, 0, sizeof(int) * 64); - - for (int i = 0; i < 64; i++) - board[i] = EMPTY; - - for (int i = 0; i < 8; i++) - for (int j = 0; j < 16; j++) - pieceList[0][i][j] = pieceList[1][i][j] = SQ_NONE; - - for (Square sq = SQ_A1; sq <= SQ_H8; sq++) - castleRightsMask[sq] = ALL_CASTLES; - - sideToMove = WHITE; - initialKFile = FILE_E; - initialKRFile = FILE_H; - initialQRFile = FILE_A; -} - - -/// Position::reset_game_ply() simply sets gamePly to 0. It is used from the -/// UCI interface code, whenever a non-reversible move is made in a -/// 'position fen moves m1 m2 ...' command. This makes it possible -/// for the program to handle games of arbitrary length, as long as the GUI -/// handles draws by the 50 move rule correctly. - -void Position::reset_game_ply() { - - st->gamePly = 0; -} - - -/// Position::put_piece() puts a piece on the given square of the board, -/// updating the board array, bitboards, and piece counts. - -void Position::put_piece(Piece p, Square s) { - - Color c = color_of_piece(p); - PieceType pt = type_of_piece(p); - - board[s] = p; - index[s] = pieceCount[c][pt]; - pieceList[c][pt][index[s]] = s; - - set_bit(&(byTypeBB[pt]), s); - set_bit(&(byColorBB[c]), s); - set_bit(&byTypeBB[0], s); // HACK: byTypeBB[0] contains all occupied squares. - - pieceCount[c][pt]++; -} - - -/// Position::allow_oo() gives the given side the right to castle kingside. -/// Used when setting castling rights during parsing of FEN strings. - -void Position::allow_oo(Color c) { - - st->castleRights |= (1 + int(c)); -} - - -/// Position::allow_ooo() gives the given side the right to castle queenside. -/// Used when setting castling rights during parsing of FEN strings. - -void Position::allow_ooo(Color c) { - - st->castleRights |= (4 + 4*int(c)); -} - - -/// Position::compute_key() computes the hash key of the position. The hash -/// key is usually updated incrementally as moves are made and unmade, the -/// compute_key() function is only used when a new position is set up, and -/// to verify the correctness of the hash key when running in debug mode. - -Key Position::compute_key() const { - - Key result = Key(0ULL); - - for (Square s = SQ_A1; s <= SQ_H8; s++) - if (square_is_occupied(s)) - result ^= zobrist[color_of_piece_on(s)][type_of_piece_on(s)][s]; - - if (ep_square() != SQ_NONE) - result ^= zobEp[ep_square()]; - - result ^= zobCastle[st->castleRights]; - if (side_to_move() == BLACK) - result ^= zobSideToMove; + if (balance < v) + return false; - return result; -} + if (nextVictim == KING) + return true; + balance -= PieceValue[MG][nextVictim]; -/// Position::compute_pawn_key() computes the hash key of the position. The -/// hash key is usually updated incrementally as moves are made and unmade, -/// the compute_pawn_key() function is only used when a new position is set -/// up, and to verify the correctness of the pawn hash key when running in -/// debug mode. + if (balance >= v) + return true; -Key Position::compute_pawn_key() const { + bool relativeStm = true; // True if the opponent is to move + occupied ^= pieces() ^ from ^ to; - Key result = Key(0ULL); - Bitboard b; - Square s; + // Find all attackers to the destination square, with the moving piece removed, + // but possibly an X-ray attacker added behind it. + Bitboard attackers = attackers_to(to, occupied) & occupied; - for (Color c = WHITE; c <= BLACK; c++) + while (true) { - b = pieces(PAWN, c); - while (b) - { - s = pop_1st_bit(&b); - result ^= zobrist[c][PAWN][s]; - } - } - return result; -} + stmAttackers = attackers & pieces(stm); + // Don't allow pinned pieces to attack pieces except the king as long all + // pinners are on their original square. + if (!(st->pinnersForKing[stm] & ~occupied)) + stmAttackers &= ~st->blockersForKing[stm]; -/// Position::compute_material_key() computes the hash key of the position. -/// The hash key is usually updated incrementally as moves are made and unmade, -/// the compute_material_key() function is only used when a new position is set -/// up, and to verify the correctness of the material hash key when running in -/// debug mode. + if (!stmAttackers) + return relativeStm; -Key Position::compute_material_key() const { - - Key result = Key(0ULL); - for (Color c = WHITE; c <= BLACK; c++) - for (PieceType pt = PAWN; pt <= QUEEN; pt++) - { - int count = piece_count(c, pt); - for (int i = 0; i < count; i++) - result ^= zobrist[c][pt][i]; - } - return result; -} - - -/// Position::compute_value() compute the incremental scores for the middle -/// game and the endgame. These functions are used to initialize the incremental -/// scores when a new position is set up, and to verify that the scores are correctly -/// updated by do_move and undo_move when the program is running in debug mode. -Score Position::compute_value() const { - - Score result = make_score(0, 0); - Bitboard b; - Square s; - - for (Color c = WHITE; c <= BLACK; c++) - for (PieceType pt = PAWN; pt <= KING; pt++) - { - b = pieces(pt, c); - while (b) - { - s = pop_1st_bit(&b); - assert(piece_on(s) == piece_of_color_and_type(c, pt)); - result += pst(c, pt, s); - } - } - - result += (side_to_move() == WHITE ? TempoValue / 2 : -TempoValue / 2); - return result; -} + // Locate and remove the next least valuable attacker + nextVictim = min_attacker(byTypeBB, to, stmAttackers, occupied, attackers); + if (nextVictim == KING) + return relativeStm == bool(attackers & pieces(~stm)); -/// Position::compute_non_pawn_material() computes the total non-pawn middle -/// game material score for the given side. Material scores are updated -/// incrementally during the search, this function is only used while -/// initializing a new Position object. + balance += relativeStm ? PieceValue[MG][nextVictim] + : -PieceValue[MG][nextVictim]; -Value Position::compute_non_pawn_material(Color c) const { + relativeStm = !relativeStm; - Value result = Value(0); + if (relativeStm == (balance >= v)) + return relativeStm; - for (PieceType pt = KNIGHT; pt <= QUEEN; pt++) - { - Bitboard b = pieces(pt, c); - while (b) - { - assert(piece_on(first_1(b)) == piece_of_color_and_type(c, pt)); - pop_1st_bit(&b); - result += piece_value_midgame(pt); - } + stm = ~stm; } - return result; } -/// Position::is_draw() tests whether the position is drawn by material, -/// repetition, or the 50 moves rule. It does not detect stalemates, this -/// must be done by the search. -// FIXME: Currently we are not handling 50 move rule correctly when in check +/// Position::is_draw() tests whether the position is drawn by 50-move rule +/// or by repetition. It does not detect stalemates. bool Position::is_draw() const { - // Draw by material? - if ( !pieces(PAWN) - && (non_pawn_material(WHITE) + non_pawn_material(BLACK) <= BishopValueMidgame)) + if (st->rule50 > 99 && (!checkers() || MoveList(*this).size())) return true; - // Draw by the 50 moves rule? - if (st->rule50 > 100 || (st->rule50 == 100 && !is_check())) - return true; + StateInfo* stp = st; + for (int i = 2, e = std::min(st->rule50, st->pliesFromNull); i <= e; i += 2) + { + stp = stp->previous->previous; - // Draw by repetition? - for (int i = 4, e = Min(Min(st->gamePly, st->rule50), st->pliesFromNull); i <= e; i += 2) - if (history[st->gamePly - i] == st->key) - return true; + if (stp->key == st->key) + return true; // Draw at first repetition + } return false; } -/// Position::is_mate() returns true or false depending on whether the -/// side to move is checkmated. - -bool Position::is_mate() const { - - MoveStack moves[256]; - return is_check() && (generate_moves(*this, moves, false) == moves); -} +/// Position::flip() flips position with the white and black sides reversed. This +/// is only useful for debugging e.g. for finding evaluation symmetry bugs. +void Position::flip() { -/// Position::has_mate_threat() tests whether a given color has a mate in one -/// from the current position. + string f, token; + std::stringstream ss(fen()); -bool Position::has_mate_threat(Color c) { - - StateInfo st1, st2; - Color stm = side_to_move(); - - if (is_check()) - return false; - - // If the input color is not equal to the side to move, do a null move - if (c != stm) - do_null_move(st1); - - MoveStack mlist[120]; - bool result = false; - Bitboard pinned = pinned_pieces(sideToMove); - - // Generate pseudo-legal non-capture and capture check moves - MoveStack* last = generate_non_capture_checks(*this, mlist); - last = generate_captures(*this, last); - - // Loop through the moves, and see if one of them is mate - for (MoveStack* cur = mlist; cur != last; cur++) + for (Rank r = RANK_8; r >= RANK_1; --r) // Piece placement { - Move move = cur->move; - if (!pl_move_is_legal(move, pinned)) - continue; - - do_move(move, st2); - if (is_mate()) - result = true; - - undo_move(move); + std::getline(ss, token, r > RANK_1 ? '/' : ' '); + f.insert(0, token + (f.empty() ? " " : "/")); } - // Undo null move, if necessary - if (c != stm) - undo_null_move(); - - return result; -} - - -/// Position::init_zobrist() is a static member function which initializes the -/// various arrays used to compute hash keys. - -void Position::init_zobrist() { + ss >> token; // Active color + f += (token == "w" ? "B " : "W "); // Will be lowercased later - for (int i = 0; i < 2; i++) - for (int j = 0; j < 8; j++) - for (int k = 0; k < 64; k++) - zobrist[i][j][k] = Key(genrand_int64()); + ss >> token; // Castling availability + f += token + " "; - for (int i = 0; i < 64; i++) - zobEp[i] = Key(genrand_int64()); + std::transform(f.begin(), f.end(), f.begin(), + [](char c) { return char(islower(c) ? toupper(c) : tolower(c)); }); - for (int i = 0; i < 16; i++) - zobCastle[i] = genrand_int64(); + ss >> token; // En passant square + f += (token == "-" ? token : token.replace(1, 1, token[1] == '3' ? "6" : "3")); - zobSideToMove = genrand_int64(); - zobExclusion = genrand_int64(); -} - - -/// Position::init_piece_square_tables() initializes the piece square tables. -/// This is a two-step operation: -/// First, the white halves of the tables are -/// copied from the MgPST[][] and EgPST[][] arrays. -/// Second, the black halves of the tables are initialized by mirroring -/// and changing the sign of the corresponding white scores. - -void Position::init_piece_square_tables() { + std::getline(ss, token); // Half and full moves + f += token; - for (Square s = SQ_A1; s <= SQ_H8; s++) - for (Piece p = WP; p <= WK; p++) - PieceSquareTable[p][s] = make_score(MgPST[p][s], EgPST[p][s]); + set(f, is_chess960(), st, this_thread()); - for (Square s = SQ_A1; s <= SQ_H8; s++) - for (Piece p = BP; p <= BK; p++) - PieceSquareTable[p][s] = -PieceSquareTable[p-8][flip_square(s)]; + assert(pos_is_ok()); } -/// Position::flipped_copy() makes a copy of the input position, but with -/// the white and black sides reversed. This is only useful for debugging, -/// especially for finding evaluation symmetry bugs. - -void Position::flipped_copy(const Position& pos) { - - assert(pos.is_ok()); - - clear(); - threadID = pos.thread(); - - // Board - for (Square s = SQ_A1; s <= SQ_H8; s++) - if (!pos.square_is_empty(s)) - put_piece(Piece(int(pos.piece_on(s)) ^ 8), flip_square(s)); - - // Side to move - sideToMove = opposite_color(pos.side_to_move()); - - // Castling rights - if (pos.can_castle_kingside(WHITE)) allow_oo(BLACK); - if (pos.can_castle_queenside(WHITE)) allow_ooo(BLACK); - if (pos.can_castle_kingside(BLACK)) allow_oo(WHITE); - if (pos.can_castle_queenside(BLACK)) allow_ooo(WHITE); - - initialKFile = pos.initialKFile; - initialKRFile = pos.initialKRFile; - initialQRFile = pos.initialQRFile; - - castleRightsMask[make_square(initialKFile, RANK_1)] ^= (WHITE_OO | WHITE_OOO); - castleRightsMask[make_square(initialKFile, RANK_8)] ^= (BLACK_OO | BLACK_OOO); - castleRightsMask[make_square(initialKRFile, RANK_1)] ^= WHITE_OO; - castleRightsMask[make_square(initialKRFile, RANK_8)] ^= BLACK_OO; - castleRightsMask[make_square(initialQRFile, RANK_1)] ^= WHITE_OOO; - castleRightsMask[make_square(initialQRFile, RANK_8)] ^= BLACK_OOO; - - // En passant square - if (pos.st->epSquare != SQ_NONE) - st->epSquare = flip_square(pos.st->epSquare); - - // Checkers - find_checkers(); - - // Hash keys - st->key = compute_key(); - st->pawnKey = compute_pawn_key(); - st->materialKey = compute_material_key(); - - // Incremental scores - st->value = compute_value(); - - // Material - st->npMaterial[WHITE] = compute_non_pawn_material(WHITE); - st->npMaterial[BLACK] = compute_non_pawn_material(BLACK); - - assert(is_ok()); -} - - -/// Position::is_ok() performs some consitency checks for the position object. +/// Position::pos_is_ok() performs some consistency checks for the position object. /// This is meant to be helpful when debugging. -bool Position::is_ok(int* failedStep) const { - - // What features of the position should be verified? - static const bool debugBitboards = false; - static const bool debugKingCount = false; - static const bool debugKingCapture = false; - static const bool debugCheckerCount = false; - static const bool debugKey = false; - static const bool debugMaterialKey = false; - static const bool debugPawnKey = false; - static const bool debugIncrementalEval = false; - static const bool debugNonPawnMaterial = false; - static const bool debugPieceCounts = false; - static const bool debugPieceList = false; - static const bool debugCastleSquares = false; - - if (failedStep) *failedStep = 1; - - // Side to move OK? - if (!color_is_ok(side_to_move())) - return false; - - // Are the king squares in the position correct? - if (failedStep) (*failedStep)++; - if (piece_on(king_square(WHITE)) != WK) - return false; +bool Position::pos_is_ok(int* failedStep) const { - if (failedStep) (*failedStep)++; - if (piece_on(king_square(BLACK)) != BK) - return false; - - // Castle files OK? - if (failedStep) (*failedStep)++; - if (!file_is_ok(initialKRFile)) - return false; + const bool Fast = true; // Quick (default) or full check? - if (!file_is_ok(initialQRFile)) - return false; + enum { Default, King, Bitboards, State, Lists, Castling }; - // Do both sides have exactly one king? - if (failedStep) (*failedStep)++; - if (debugKingCount) + for (int step = Default; step <= (Fast ? Default : Castling); step++) { - int kingCount[2] = {0, 0}; - for (Square s = SQ_A1; s <= SQ_H8; s++) - if (type_of_piece_on(s) == KING) - kingCount[color_of_piece_on(s)]++; - - if (kingCount[0] != 1 || kingCount[1] != 1) - return false; - } + if (failedStep) + *failedStep = step; + + if (step == Default) + if ( (sideToMove != WHITE && sideToMove != BLACK) + || piece_on(square(WHITE)) != W_KING + || piece_on(square(BLACK)) != B_KING + || ( ep_square() != SQ_NONE + && relative_rank(sideToMove, ep_square()) != RANK_6)) + return false; - // Can the side to move capture the opponent's king? - if (failedStep) (*failedStep)++; - if (debugKingCapture) - { - Color us = side_to_move(); - Color them = opposite_color(us); - Square ksq = king_square(them); - if (attackers_to(ksq) & pieces_of_color(us)) - return false; - } + if (step == King) + if ( std::count(board, board + SQUARE_NB, W_KING) != 1 + || std::count(board, board + SQUARE_NB, B_KING) != 1 + || attackers_to(square(~sideToMove)) & pieces(sideToMove)) + return false; - // Is there more than 2 checkers? - if (failedStep) (*failedStep)++; - if (debugCheckerCount && count_1s(st->checkersBB) > 2) - return false; + if (step == Bitboards) + { + if ( (pieces(WHITE) & pieces(BLACK)) + ||(pieces(WHITE) | pieces(BLACK)) != pieces()) + return false; - // Bitboards OK? - if (failedStep) (*failedStep)++; - if (debugBitboards) - { - // The intersection of the white and black pieces must be empty - if ((pieces_of_color(WHITE) & pieces_of_color(BLACK)) != EmptyBoardBB) - return false; + for (PieceType p1 = PAWN; p1 <= KING; ++p1) + for (PieceType p2 = PAWN; p2 <= KING; ++p2) + if (p1 != p2 && (pieces(p1) & pieces(p2))) + return false; + } - // The union of the white and black pieces must be equal to all - // occupied squares - if ((pieces_of_color(WHITE) | pieces_of_color(BLACK)) != occupied_squares()) - return false; + if (step == State) + { + StateInfo si = *st; + set_state(&si); + if (std::memcmp(&si, st, sizeof(StateInfo))) + return false; + } - // Separate piece type bitboards must have empty intersections - for (PieceType p1 = PAWN; p1 <= KING; p1++) - for (PieceType p2 = PAWN; p2 <= KING; p2++) - if (p1 != p2 && (pieces(p1) & pieces(p2))) + if (step == Lists) + for (Piece pc : Pieces) + { + if (pieceCount[pc] != popcount(pieces(color_of(pc), type_of(pc)))) return false; - } - - // En passant square OK? - if (failedStep) (*failedStep)++; - if (ep_square() != SQ_NONE) - { - // The en passant square must be on rank 6, from the point of view of the - // side to move. - if (relative_rank(side_to_move(), ep_square()) != RANK_6) - return false; - } - - // Hash key OK? - if (failedStep) (*failedStep)++; - if (debugKey && st->key != compute_key()) - return false; - - // Pawn hash key OK? - if (failedStep) (*failedStep)++; - if (debugPawnKey && st->pawnKey != compute_pawn_key()) - return false; - - // Material hash key OK? - if (failedStep) (*failedStep)++; - if (debugMaterialKey && st->materialKey != compute_material_key()) - return false; - - // Incremental eval OK? - if (failedStep) (*failedStep)++; - if (debugIncrementalEval && st->value != compute_value()) - return false; - // Non-pawn material OK? - if (failedStep) (*failedStep)++; - if (debugNonPawnMaterial) - { - if (st->npMaterial[WHITE] != compute_non_pawn_material(WHITE)) - return false; - - if (st->npMaterial[BLACK] != compute_non_pawn_material(BLACK)) - return false; - } - - // Piece counts OK? - if (failedStep) (*failedStep)++; - if (debugPieceCounts) - for (Color c = WHITE; c <= BLACK; c++) - for (PieceType pt = PAWN; pt <= KING; pt++) - if (pieceCount[c][pt] != count_1s(pieces(pt, c))) - return false; + for (int i = 0; i < pieceCount[pc]; ++i) + if (board[pieceList[pc][i]] != pc || index[pieceList[pc][i]] != i) + return false; + } - if (failedStep) (*failedStep)++; - if (debugPieceList) - { - for (Color c = WHITE; c <= BLACK; c++) - for (PieceType pt = PAWN; pt <= KING; pt++) - for (int i = 0; i < pieceCount[c][pt]; i++) + if (step == Castling) + for (Color c = WHITE; c <= BLACK; ++c) + for (CastlingSide s = KING_SIDE; s <= QUEEN_SIDE; s = CastlingSide(s + 1)) { - if (piece_on(piece_list(c, pt, i)) != piece_of_color_and_type(c, pt)) - return false; + if (!can_castle(c | s)) + continue; - if (index[piece_list(c, pt, i)] != i) + if ( piece_on(castlingRookSquare[c | s]) != make_piece(c, ROOK) + || castlingRightsMask[castlingRookSquare[c | s]] != (c | s) + ||(castlingRightsMask[square(c)] & (c | s)) != (c | s)) return false; } } - if (failedStep) (*failedStep)++; - if (debugCastleSquares) { - for (Color c = WHITE; c <= BLACK; c++) { - if (can_castle_kingside(c) && piece_on(initial_kr_square(c)) != piece_of_color_and_type(c, ROOK)) - return false; - if (can_castle_queenside(c) && piece_on(initial_qr_square(c)) != piece_of_color_and_type(c, ROOK)) - return false; - } - if (castleRightsMask[initial_kr_square(WHITE)] != (ALL_CASTLES ^ WHITE_OO)) - return false; - if (castleRightsMask[initial_qr_square(WHITE)] != (ALL_CASTLES ^ WHITE_OOO)) - return false; - if (castleRightsMask[initial_kr_square(BLACK)] != (ALL_CASTLES ^ BLACK_OO)) - return false; - if (castleRightsMask[initial_qr_square(BLACK)] != (ALL_CASTLES ^ BLACK_OOO)) - return false; - } - - if (failedStep) *failedStep = 0; return true; }