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stockfish/src/position.h

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/*
Glaurung, a UCI chess playing engine.
Copyright (C) 2004-2008 Tord Romstad
Glaurung 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.
Glaurung 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
////
//// Includes
////
#include "bitboard.h"
#include "color.h"
#include "direction.h"
#include "move.h"
#include "piece.h"
#include "phase.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
};
/// The UndoInfo 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 UndoInfo object
/// must be passed as a parameter. When the move is unmade (by calling
/// Position::undo_move), the same UndoInfo object must be passed again.
struct UndoInfo {
int castleRights;
Square epSquare;
Bitboard checkersBB;
Key key, pawnKey, materialKey;
int rule50;
Move lastMove;
PieceType capture;
Value mgValue, egValue;
};
/// 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 occupiecd 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.
/// * The last move played.
/// * 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;
public:
// 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() 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_of_type(PieceType pt) const;
Bitboard pieces_of_color_and_type(Color c, PieceType pt) const;
Bitboard pawns() const;
Bitboard knights() const;
Bitboard bishops() const;
Bitboard rooks() const;
Bitboard queens() const;
Bitboard kings() const;
Bitboard rooks_and_queens() const;
Bitboard bishops_and_queens() const;
Bitboard sliders() const;
Bitboard pawns(Color c) const;
Bitboard knights(Color c) const;
Bitboard bishops(Color c) const;
Bitboard rooks(Color c) const;
Bitboard queens(Color c) const;
Bitboard kings(Color c) const;
Bitboard rooks_and_queens(Color c) const;
Bitboard bishops_and_queens(Color c) const;
Bitboard sliders_of_color(Color c) const;
// Number of pieces of each color and type
int piece_count(Color c, PieceType pt) const;
int pawn_count(Color c) const;
int knight_count(Color c) const;
int bishop_count(Color c) const;
int rook_count(Color c) const;
int queen_count(Color c) 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;
// Attack bitboards
Bitboard sliding_attacks(Square s, Direction d) const;
Bitboard ray_attacks(Square s, SignedDirection d) const;
Bitboard pawn_attacks(Color c, Square s) const;
Bitboard white_pawn_attacks(Square s) const;
Bitboard black_pawn_attacks(Square s) const;
Bitboard knight_attacks(Square s) const;
Bitboard bishop_attacks(Square s) const;
Bitboard rook_attacks(Square s) const;
Bitboard queen_attacks(Square s) const;
Bitboard king_attacks(Square s) const;
// Bitboards for pinned pieces and discovered check candidates
Bitboard discovered_check_candidates(Color c) const;
Bitboard pinned_pieces(Color c) const;
// Checking pieces
Bitboard checkers() const;
// Piece lists:
Square piece_list(Color c, PieceType pt, int index) const;
Square pawn_list(Color c, int index) const;
Square knight_list(Color c, int index) const;
Square bishop_list(Color c, int index) const;
Square rook_list(Color c, int index) const;
Square queen_list(Color c, int index) const;
// Attack information for a given square
bool square_is_attacked(Square s, Color c) const;
Bitboard attacks_to(Square s) const;
Bitboard attacks_to(Square s, Color c) const;
bool is_check() const;
bool piece_attacks_square(Square f, Square t) const;
bool white_pawn_attacks_square(Square f, Square t) const;
bool black_pawn_attacks_square(Square f, Square t) const;
bool knight_attacks_square(Square f, Square t) const;
bool bishop_attacks_square(Square f, Square t) const;
bool rook_attacks_square(Square f, Square t) const;
bool queen_attacks_square(Square f, Square t) const;
bool king_attacks_square(Square f, Square t) const;
// Properties of moves
bool move_is_legal(Move m) const;
bool 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_pawn_push_to_7th(Move m) const;
bool move_is_passed_pawn_push(Move m) const;
bool move_was_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;
bool pawn_is_isolated(Color c, Square s) const;
bool pawn_is_doubled(Color c, Square s) const;
// Open and half-open files
bool file_is_open(File f) const;
bool file_is_half_open(Color c, File f) const;
// Weak squares
bool square_is_weak(Square s, Color c) const;
// Doing and undoing moves
void backup(UndoInfo &u) const;
void restore(const UndoInfo &u);
void do_move(Move m, UndoInfo &u);
void do_move(Move m, UndoInfo &u, Bitboard dcCandidates);
void undo_move(Move m, const UndoInfo &u);
void do_null_move(UndoInfo &u);
void undo_null_move(const UndoInfo &u);
// Static exchange evaluation
int see(Square from, Square to) const;
int see(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;
// Game termination checks
bool is_mate();
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() 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_castle_move(Move m);
void do_promotion_move(Move m, UndoInfo &u);
void do_ep_move(Move m);
void undo_castle_move(Move m);
void undo_promotion_move(Move m, const UndoInfo &u);
void undo_ep_move(Move m);
void find_checkers();
// 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
Value mg_pst(Color c, PieceType pt, Square s) const;
Value eg_pst(Color c, PieceType pt, Square s) const;
Value compute_mg_value() const;
Value compute_eg_value() const;
Value compute_non_pawn_material(Color c) const;
// Bitboards
Bitboard byColorBB[2], byTypeBB[8];
Bitboard checkersBB;
// Board
Piece board[64];
// Piece counts
int pieceCount[2][8]; // [color][pieceType]
// Piece lists
Square pieceList[2][8][16]; // [color][pieceType][index]
int index[64];
// Other info
Color sideToMove;
int castleRights;
File initialKFile, initialKRFile, initialQRFile;
Square epSquare;
Square kingSquare[2];
Move lastMove;
Key key, pawnKey, materialKey, history[MaxGameLength];
int rule50, gamePly;
Value mgValue, egValue;
Value npMaterial[2];
// 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(this->piece_on(s));
}
inline PieceType Position::type_of_piece_on(Square s) const {
return type_of_piece(this->piece_on(s));
}
inline bool Position::square_is_empty(Square s) const {
return this->piece_on(s) == EMPTY;
}
inline bool Position::square_is_occupied(Square s) const {
return !this->square_is_empty(s);
}
inline Value Position::midgame_value_of_piece_on(Square s) const {
return piece_value_midgame(this->piece_on(s));
}
inline Value Position::endgame_value_of_piece_on(Square s) const {
return piece_value_endgame(this->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 ~(this->occupied_squares());
}
inline Bitboard Position::pieces_of_color(Color c) const {
return byColorBB[c];
}
inline Bitboard Position::pieces_of_type(PieceType pt) const {
return byTypeBB[pt];
}
inline Bitboard Position::pieces_of_color_and_type(Color c, PieceType pt)
const {
return this->pieces_of_color(c) & this->pieces_of_type(pt);
}
inline Bitboard Position::pawns() const {
return this->pieces_of_type(PAWN);
}
inline Bitboard Position::knights() const {
return this->pieces_of_type(KNIGHT);
}
inline Bitboard Position::bishops() const {
return this->pieces_of_type(BISHOP);
}
inline Bitboard Position::rooks() const {
return this->pieces_of_type(ROOK);
}
inline Bitboard Position::queens() const {
return this->pieces_of_type(QUEEN);
}
inline Bitboard Position::kings() const {
return this->pieces_of_type(KING);
}
inline Bitboard Position::rooks_and_queens() const {
return this->rooks() | this->queens();
}
inline Bitboard Position::bishops_and_queens() const {
return this->bishops() | this->queens();
}
inline Bitboard Position::sliders() const {
return this->bishops() | this->queens() | this->rooks();
}
inline Bitboard Position::pawns(Color c) const {
return this->pieces_of_color_and_type(c, PAWN);
}
inline Bitboard Position::knights(Color c) const {
return this->pieces_of_color_and_type(c, KNIGHT);
}
inline Bitboard Position::bishops(Color c) const {
return this->pieces_of_color_and_type(c, BISHOP);
}
inline Bitboard Position::rooks(Color c) const {
return this->pieces_of_color_and_type(c, ROOK);
}
inline Bitboard Position::queens(Color c) const {
return this->pieces_of_color_and_type(c, QUEEN);
}
inline Bitboard Position::kings(Color c) const {
return this->pieces_of_color_and_type(c, KING);
}
inline Bitboard Position::rooks_and_queens(Color c) const {
return this->rooks_and_queens() & this->pieces_of_color(c);
}
inline Bitboard Position::bishops_and_queens(Color c) const {
return this->bishops_and_queens() & this->pieces_of_color(c);
}
inline Bitboard Position::sliders_of_color(Color c) const {
return this->sliders() & this->pieces_of_color(c);
}
inline int Position::piece_count(Color c, PieceType pt) const {
return pieceCount[c][pt];
}
inline int Position::pawn_count(Color c) const {
return this->piece_count(c, PAWN);
}
inline int Position::knight_count(Color c) const {
return this->piece_count(c, KNIGHT);
}
inline int Position::bishop_count(Color c) const {
return this->piece_count(c, BISHOP);
}
inline int Position::rook_count(Color c) const {
return this->piece_count(c, ROOK);
}
inline int Position::queen_count(Color c) const {
return this->piece_count(c, QUEEN);
}
inline Square Position::piece_list(Color c, PieceType pt, int index) const {
return pieceList[c][pt][index];
}
inline Square Position::pawn_list(Color c, int index) const {
return this->piece_list(c, PAWN, index);
}
inline Square Position::knight_list(Color c, int index) const {
return this->piece_list(c, KNIGHT, index);
}
inline Square Position::bishop_list(Color c, int index) const {
return this->piece_list(c, BISHOP, index);
}
inline Square Position::rook_list(Color c, int index) const {
return this->piece_list(c, ROOK, index);
}
inline Square Position::queen_list(Color c, int index) const {
return this->piece_list(c, QUEEN, index);
}
inline Square Position::ep_square() const {
return epSquare;
}
inline Square Position::king_square(Color c) const {
return kingSquare[c];
}
inline bool Position::can_castle_kingside(Color side) const {
return castleRights & (1+int(side));
}
inline bool Position::can_castle_queenside(Color side) const {
return 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));
}
inline Bitboard Position::pawn_attacks(Color c, Square s) const {
return StepAttackBB[pawn_of_color(c)][s];
}
inline Bitboard Position::white_pawn_attacks(Square s) const {
return this->pawn_attacks(WHITE, s);
}
inline Bitboard Position::black_pawn_attacks(Square s) const {
return this->pawn_attacks(BLACK, s);
}
inline Bitboard Position::knight_attacks(Square s) const {
return StepAttackBB[KNIGHT][s];
}
inline Bitboard Position::rook_attacks(Square s) const {
return rook_attacks_bb(s, this->occupied_squares());
}
inline Bitboard Position::bishop_attacks(Square s) const {
return bishop_attacks_bb(s, this->occupied_squares());
}
inline Bitboard Position::queen_attacks(Square s) const {
return this->rook_attacks(s) | this->bishop_attacks(s);
}
inline Bitboard Position::king_attacks(Square s) const {
return StepAttackBB[KING][s];
}
inline Bitboard Position::checkers() const {
return checkersBB;
}
inline bool Position::is_check() const {
return this->checkers() != EmptyBoardBB;
}
inline bool Position::white_pawn_attacks_square(Square f, Square t) const {
return bit_is_set(this->white_pawn_attacks(f), t);
}
inline bool Position::black_pawn_attacks_square(Square f, Square t) const {
return bit_is_set(this->black_pawn_attacks(f), t);
}
inline bool Position::knight_attacks_square(Square f, Square t) const {
return bit_is_set(this->knight_attacks(f), t);
}
inline bool Position::bishop_attacks_square(Square f, Square t) const {
return bit_is_set(this->bishop_attacks(f), t);
}
inline bool Position::rook_attacks_square(Square f, Square t) const {
return bit_is_set(this->rook_attacks(f), t);
}
inline bool Position::queen_attacks_square(Square f, Square t) const {
return bit_is_set(this->queen_attacks(f), t);
}
inline bool Position::king_attacks_square(Square f, Square t) const {
return bit_is_set(this->king_attacks(f), t);
}
inline bool Position::pawn_is_passed(Color c, Square s) const {
return !(this->pawns(opposite_color(c)) & passed_pawn_mask(c, s));
}
inline bool Position::pawn_is_isolated(Color c, Square s) const {
return !(this->pawns(c) & neighboring_files_bb(s));
}
inline bool Position::pawn_is_doubled(Color c, Square s) const {
return this->pawns(c) & squares_behind(c, s);
}
inline bool Position::file_is_open(File f) const {
return !(this->pawns() & file_bb(f));
}
inline bool Position::file_is_half_open(Color c, File f) const {
return !(this->pawns(c) & file_bb(f));
}
inline bool Position::square_is_weak(Square s, Color c) const {
return !(this->pawns(c) & outpost_mask(opposite_color(c), s));
}
inline Key Position::get_key() const {
return key;
}
inline Key Position::get_pawn_key() const {
return pawnKey;
}
inline Key Position::get_material_key() const {
return materialKey;
}
inline Value Position::mg_pst(Color c, PieceType pt, Square s) const {
return MgPieceSquareTable[piece_of_color_and_type(c, pt)][s];
}
inline Value Position::eg_pst(Color c, PieceType pt, Square s) const {
return EgPieceSquareTable[piece_of_color_and_type(c, pt)][s];
}
inline Value Position::mg_value() const {
return mgValue;
}
inline Value Position::eg_value() const {
return egValue;
}
inline Value Position::non_pawn_material(Color c) const {
return npMaterial[c];
}
inline Phase Position::game_phase() const {
// The purpose of the Value(325) terms below is to make sure the difference
// between MidgameLimit and EndgameLimit is a power of 2, which should make
// the division at the end of the function a bit faster.
static const Value MidgameLimit =
2*QueenValueMidgame+2*RookValueMidgame+6*BishopValueMidgame+Value(325);
static const Value EndgameLimit = 4*RookValueMidgame-Value(325);
Value npm = this->non_pawn_material(WHITE) + this->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_pawn_push_to_7th(Move m) const {
Color c = this->side_to_move();
return
this->piece_on(move_from(m)) == pawn_of_color(c) &&
pawn_rank(c, move_to(m)) == RANK_7;
}
inline bool Position::move_is_passed_pawn_push(Move m) const {
Color c = this->side_to_move();
return
this->piece_on(move_from(m)) == pawn_of_color(c) &&
this->pawn_is_passed(c, move_to(m));
}
inline bool Position::move_was_passed_pawn_push(Move m) const {
Color c = opposite_color(this->side_to_move());
return
this->piece_on(move_to(m)) == pawn_of_color(c) &&
this->pawn_is_passed(c, move_to(m));
}
inline int Position::rule_50_counter() const {
return rule50;
}
inline bool Position::opposite_colored_bishops() const {
return
this->bishop_count(WHITE) == 1 && this->bishop_count(BLACK) == 1 &&
square_color(this->bishop_list(WHITE, 0)) !=
square_color(this->bishop_list(BLACK, 0));
}
inline bool Position::has_pawn_on_7th(Color c) const {
return this->pawns(c) & relative_rank_bb(c, RANK_7);
}
#endif // !defined(POSITION_H_INCLUDED)
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