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position.h
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position.h
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/*
Stockfish, a UCI chess playing engine derived from Glaurung 2.1
Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
Copyright (C) 2008-2009 Marco Costalba
Stockfish is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
Stockfish is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#if !defined(POSITION_H_INCLUDED)
#define POSITION_H_INCLUDED
// Disable some silly and noisy warning from MSVC compiler
#if defined(_MSC_VER)
// Forcing value to bool 'true' or 'false' (performance warning)
#pragma warning(disable: 4800)
// Conditional expression is constant
#pragma warning(disable: 4127)
#endif
////
//// Includes
////
#include "bitboard.h"
#include "color.h"
#include "direction.h"
#include "move.h"
#include "piece.h"
#include "square.h"
#include "value.h"
////
//// Constants
////
/// FEN string for the initial position
const std::string StartPosition = "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1";
/// Maximum number of plies per game (220 should be enough, because the
/// maximum search depth is 100, and during position setup we reset the
/// move counter for every non-reversible move).
const int MaxGameLength = 220;
////
//// Types
////
/// Castle rights, encoded as bit fields
enum CastleRights {
NO_CASTLES = 0,
WHITE_OO = 1,
BLACK_OO = 2,
WHITE_OOO = 4,
BLACK_OOO = 8,
ALL_CASTLES = 15
};
/// Game phase
enum Phase {
PHASE_ENDGAME = 0,
PHASE_MIDGAME = 128
};
/// The StateInfo struct stores information we need to restore a Position
/// object to its previous state when we retract a move. Whenever a move
/// is made on the board (by calling Position::do_move), an StateInfo object
/// must be passed as a parameter.
struct StateInfo {
Key key, pawnKey, materialKey;
int castleRights, rule50, pliesFromNull;
Square epSquare;
Value mgValue, egValue;
Value npMaterial[2];
PieceType capture;
Bitboard checkersBB;
StateInfo* previous;
};
/// The position data structure. A position consists of the following data:
///
/// * For each piece type, a bitboard representing the squares occupied
/// by pieces of that type.
/// * For each color, a bitboard representing the squares occupied by
/// pieces of that color.
/// * A bitboard of all occupied squares.
/// * A bitboard of all checking pieces.
/// * A 64-entry array of pieces, indexed by the squares of the board.
/// * The current side to move.
/// * Information about the castling rights for both sides.
/// * The initial files of the kings and both pairs of rooks. This is
/// used to implement the Chess960 castling rules.
/// * The en passant square (which is SQ_NONE if no en passant capture is
/// possible).
/// * The squares of the kings for both sides.
/// * Hash keys for the position itself, the current pawn structure, and
/// the current material situation.
/// * Hash keys for all previous positions in the game for detecting
/// repetition draws.
/// * A counter for detecting 50 move rule draws.
class Position {
friend class MaterialInfo;
friend class EndgameFunctions;
public:
enum GamePhase {
MidGame,
EndGame
};
// Constructors
Position() {}
Position(const Position& pos);
Position(const std::string& fen);
// Text input/output
void from_fen(const std::string& fen);
const std::string to_fen() const;
void print(Move m = MOVE_NONE) const;
// Copying
void copy(const Position& pos);
void flipped_copy(const Position& pos);
// The piece on a given square
Piece piece_on(Square s) const;
PieceType type_of_piece_on(Square s) const;
Color color_of_piece_on(Square s) const;
bool square_is_empty(Square s) const;
bool square_is_occupied(Square s) const;
Value midgame_value_of_piece_on(Square s) const;
Value endgame_value_of_piece_on(Square s) const;
// Side to move
Color side_to_move() const;
// Bitboard representation of the position
Bitboard empty_squares() const;
Bitboard occupied_squares() const;
Bitboard pieces_of_color(Color c) const;
Bitboard pieces(PieceType pt) const;
Bitboard pieces(PieceType pt, Color c) const;
Bitboard pieces(PieceType pt1, PieceType pt2) const;
Bitboard pieces(PieceType pt1, PieceType pt2, Color c) const;
// Number of pieces of each color and type
int piece_count(Color c, PieceType pt) const;
// The en passant square
Square ep_square() const;
// Current king position for each color
Square king_square(Color c) const;
// Castling rights
bool can_castle_kingside(Color c) const;
bool can_castle_queenside(Color c) const;
bool can_castle(Color c) const;
Square initial_kr_square(Color c) const;
Square initial_qr_square(Color c) const;
// Bitboards for pinned pieces and discovered check candidates
Bitboard discovered_check_candidates(Color c) const;
Bitboard pinned_pieces(Color c) const;
// Checking pieces and under check information
Bitboard checkers() const;
bool is_check() const;
// Piece lists
Square piece_list(Color c, PieceType pt, int index) const;
const Square* piece_list_begin(Color c, PieceType pt) const;
// Information about attacks to or from a given square
Bitboard attackers_to(Square s) const;
Bitboard attacks_from(Piece p, Square s) const;
template<PieceType> Bitboard attacks_from(Square s) const;
template<PieceType> Bitboard attacks_from(Square s, Color c) const;
// Properties of moves
bool pl_move_is_legal(Move m) const;
bool pl_move_is_legal(Move m, Bitboard pinned) const;
bool move_is_check(Move m) const;
bool move_is_check(Move m, Bitboard dcCandidates) const;
bool move_is_capture(Move m) const;
bool move_is_passed_pawn_push(Move m) const;
bool move_attacks_square(Move m, Square s) const;
// Information about pawns
bool pawn_is_passed(Color c, Square s) const;
static bool pawn_is_passed(Bitboard theirPawns, Color c, Square s);
static bool pawn_is_isolated(Bitboard ourPawns, Square s);
static bool pawn_is_doubled(Bitboard ourPawns, Color c, Square s);
// Weak squares
bool square_is_weak(Square s, Color c) const;
// Doing and undoing moves
void saveState();
void do_move(Move m, StateInfo& st);
void do_move(Move m, StateInfo& st, Bitboard dcCandidates);
void undo_move(Move m);
void do_null_move(StateInfo& st);
void undo_null_move();
// Static exchange evaluation
int see(Square from, Square to) const;
int see(Move m) const;
int see(Square to) const;
int see_sign(Move m) const;
// Accessing hash keys
Key get_key() const;
Key get_pawn_key() const;
Key get_material_key() const;
// Incremental evaluation
Value mg_value() const;
Value eg_value() const;
Value non_pawn_material(Color c) const;
Phase game_phase() const;
template<GamePhase> Value pst_delta(Piece piece, Square from, Square to) const;
// Game termination checks
bool is_mate() const;
bool is_draw() const;
// Check if one side threatens a mate in one
bool has_mate_threat(Color c);
// Number of plies since the last non-reversible move
int rule_50_counter() const;
// Other properties of the position
bool opposite_colored_bishops() const;
bool has_pawn_on_7th(Color c) const;
// Reset the gamePly variable to 0
void reset_game_ply();
// Position consistency check, for debugging
bool is_ok(int* failedStep = NULL) const;
// Static member functions
static void init_zobrist();
static void init_piece_square_tables();
private:
// Initialization helper functions (used while setting up a position)
void clear();
void put_piece(Piece p, Square s);
void allow_oo(Color c);
void allow_ooo(Color c);
// Helper functions for doing and undoing moves
void do_capture_move(Bitboard& key, PieceType capture, Color them, Square to, bool ep);
void do_castle_move(Move m);
void undo_castle_move(Move m);
void find_checkers();
template<PieceType Piece>
void update_checkers(Bitboard* pCheckersBB, Square ksq, Square from, Square to, Bitboard dcCandidates);
template<bool FindPinned>
Bitboard hidden_checkers(Color c) const;
// Computing hash keys from scratch (for initialization and debugging)
Key compute_key() const;
Key compute_pawn_key() const;
Key compute_material_key() const;
// Computing incremental evaluation scores and material counts
template<GamePhase> Value pst(Color c, PieceType pt, Square s) const;
template<GamePhase> Value compute_value() const;
Value compute_non_pawn_material(Color c) const;
// Board
Piece board[64];
// Bitboards
Bitboard byTypeBB[8], byColorBB[2];
// Piece counts
int pieceCount[2][8]; // [color][pieceType]
// Piece lists
Square pieceList[2][8][16]; // [color][pieceType][index]
int index[64]; // [square]
// Other info
Color sideToMove;
int gamePly;
Key history[MaxGameLength];
File initialKFile, initialKRFile, initialQRFile;
StateInfo startState;
StateInfo* st;
// Static variables
static int castleRightsMask[64];
static Key zobrist[2][8][64];
static Key zobEp[64];
static Key zobCastle[16];
static Key zobMaterial[2][8][16];
static Key zobSideToMove;
static Value MgPieceSquareTable[16][64];
static Value EgPieceSquareTable[16][64];
};
////
//// Inline functions
////
inline Piece Position::piece_on(Square s) const {
return board[s];
}
inline Color Position::color_of_piece_on(Square s) const {
return color_of_piece(piece_on(s));
}
inline PieceType Position::type_of_piece_on(Square s) const {
return type_of_piece(piece_on(s));
}
inline bool Position::square_is_empty(Square s) const {
return piece_on(s) == EMPTY;
}
inline bool Position::square_is_occupied(Square s) const {
return !square_is_empty(s);
}
inline Value Position::midgame_value_of_piece_on(Square s) const {
return piece_value_midgame(piece_on(s));
}
inline Value Position::endgame_value_of_piece_on(Square s) const {
return piece_value_endgame(piece_on(s));
}
inline Color Position::side_to_move() const {
return sideToMove;
}
inline Bitboard Position::occupied_squares() const {
return byTypeBB[0];
}
inline Bitboard Position::empty_squares() const {
return ~(occupied_squares());
}
inline Bitboard Position::pieces_of_color(Color c) const {
return byColorBB[c];
}
inline Bitboard Position::pieces(PieceType pt) const {
return byTypeBB[pt];
}
inline Bitboard Position::pieces(PieceType pt, Color c) const {
return byTypeBB[pt] & byColorBB[c];
}
inline Bitboard Position::pieces(PieceType pt1, PieceType pt2) const {
return byTypeBB[pt1] | byTypeBB[pt2];
}
inline Bitboard Position::pieces(PieceType pt1, PieceType pt2, Color c) const {
return (byTypeBB[pt1] | byTypeBB[pt2]) & byColorBB[c];
}
inline int Position::piece_count(Color c, PieceType pt) const {
return pieceCount[c][pt];
}
inline Square Position::piece_list(Color c, PieceType pt, int index) const {
return pieceList[c][pt][index];
}
inline const Square* Position::piece_list_begin(Color c, PieceType pt) const {
return pieceList[c][pt];
}
inline Square Position::ep_square() const {
return st->epSquare;
}
inline Square Position::king_square(Color c) const {
return pieceList[c][KING][0];
}
inline bool Position::can_castle_kingside(Color side) const {
return st->castleRights & (1+int(side));
}
inline bool Position::can_castle_queenside(Color side) const {
return st->castleRights & (4+4*int(side));
}
inline bool Position::can_castle(Color side) const {
return can_castle_kingside(side) || can_castle_queenside(side);
}
inline Square Position::initial_kr_square(Color c) const {
return relative_square(c, make_square(initialKRFile, RANK_1));
}
inline Square Position::initial_qr_square(Color c) const {
return relative_square(c, make_square(initialQRFile, RANK_1));
}
template<>
inline Bitboard Position::attacks_from<PAWN>(Square s, Color c) const {
return StepAttackBB[piece_of_color_and_type(c, PAWN)][s];
}
template<PieceType Piece> // Knight and King and white pawns
inline Bitboard Position::attacks_from(Square s) const {
return StepAttackBB[Piece][s];
}
template<>
inline Bitboard Position::attacks_from<BISHOP>(Square s) const {
return bishop_attacks_bb(s, occupied_squares());
}
template<>
inline Bitboard Position::attacks_from<ROOK>(Square s) const {
return rook_attacks_bb(s, occupied_squares());
}
template<>
inline Bitboard Position::attacks_from<QUEEN>(Square s) const {
return attacks_from<ROOK>(s) | attacks_from<BISHOP>(s);
}
inline Bitboard Position::checkers() const {
return st->checkersBB;
}
inline bool Position::is_check() const {
return st->checkersBB != EmptyBoardBB;
}
inline bool Position::pawn_is_passed(Color c, Square s) const {
return !(pieces(PAWN, opposite_color(c)) & passed_pawn_mask(c, s));
}
inline bool Position::pawn_is_passed(Bitboard theirPawns, Color c, Square s) {
return !(theirPawns & passed_pawn_mask(c, s));
}
inline bool Position::pawn_is_isolated(Bitboard ourPawns, Square s) {
return !(ourPawns & neighboring_files_bb(s));
}
inline bool Position::pawn_is_doubled(Bitboard ourPawns, Color c, Square s) {
return ourPawns & squares_behind(c, s);
}
inline bool Position::square_is_weak(Square s, Color c) const {
return !(pieces(PAWN, c) & outpost_mask(opposite_color(c), s));
}
inline Key Position::get_key() const {
return st->key;
}
inline Key Position::get_pawn_key() const {
return st->pawnKey;
}
inline Key Position::get_material_key() const {
return st->materialKey;
}
template<Position::GamePhase Ph>
inline Value Position::pst(Color c, PieceType pt, Square s) const {
return (Ph == MidGame ? MgPieceSquareTable[piece_of_color_and_type(c, pt)][s]
: EgPieceSquareTable[piece_of_color_and_type(c, pt)][s]);
}
template<Position::GamePhase Ph>
inline Value Position::pst_delta(Piece piece, Square from, Square to) const {
return (Ph == MidGame ? MgPieceSquareTable[piece][to] - MgPieceSquareTable[piece][from]
: EgPieceSquareTable[piece][to] - EgPieceSquareTable[piece][from]);
}
inline Value Position::mg_value() const {
return st->mgValue;
}
inline Value Position::eg_value() const {
return st->egValue;
}
inline Value Position::non_pawn_material(Color c) const {
return st->npMaterial[c];
}
inline Phase Position::game_phase() const {
// Values modified by Joona Kiiski
static const Value MidgameLimit = Value(15581);
static const Value EndgameLimit = Value(3998);
Value npm = non_pawn_material(WHITE) + non_pawn_material(BLACK);
if (npm >= MidgameLimit)
return PHASE_MIDGAME;
else if(npm <= EndgameLimit)
return PHASE_ENDGAME;
else
return Phase(((npm - EndgameLimit) * 128) / (MidgameLimit - EndgameLimit));
}
inline bool Position::move_is_passed_pawn_push(Move m) const {
Color c = side_to_move();
return piece_on(move_from(m)) == piece_of_color_and_type(c, PAWN)
&& pawn_is_passed(c, move_to(m));
}
inline int Position::rule_50_counter() const {
return st->rule50;
}
inline bool Position::opposite_colored_bishops() const {
return piece_count(WHITE, BISHOP) == 1
&& piece_count(BLACK, BISHOP) == 1
&& square_color(piece_list(WHITE, BISHOP, 0)) != square_color(piece_list(BLACK, BISHOP, 0));
}
inline bool Position::has_pawn_on_7th(Color c) const {
return pieces(PAWN, c) & relative_rank_bb(c, RANK_7);
}
inline bool Position::move_is_capture(Move m) const {
// Move must not be MOVE_NONE !
return (!square_is_empty(move_to(m)) && !move_is_castle(m)) || move_is_ep(m);
}
#endif // !defined(POSITION_H_INCLUDED)