droidfish/DroidFish/jni/stockfish/pawns.h

/*
  Stockfish, a UCI chess playing engine derived from Glaurung 2.1
  Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
  Copyright (C) 2008-2012 Marco Costalba, Joona Kiiski, 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
  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(PAWNS_H_INCLUDED)
#define PAWNS_H_INCLUDED

#include "misc.h"
#include "position.h"
#include "types.h"

const int PawnTableSize = 16384;

/// PawnEntry is a class which contains various information about a pawn
/// structure. Currently, it only includes a middle game and an end game
/// pawn structure evaluation, and a bitboard of passed pawns. We may want
/// to add further information in the future. A lookup to the pawn hash
/// table (performed by calling the probe method in a PawnTable object)
/// returns a pointer to a PawnEntry object.

class PawnEntry {

  friend struct PawnTable;

public:
  Score pawns_value() const;
  Bitboard pawn_attacks(Color c) const;
  Bitboard passed_pawns(Color c) const;
  int file_is_half_open(Color c, File f) const;
  int has_open_file_to_left(Color c, File f) const;
  int has_open_file_to_right(Color c, File f) const;

  template<Color Us>
  Score king_safety(const Position& pos, Square ksq);

private:
  template<Color Us>
  Score update_safety(const Position& pos, Square ksq);

  template<Color Us>
  Value shelter_storm(const Position& pos, Square ksq);

  Key key;
  Bitboard passedPawns[2];
  Bitboard pawnAttacks[2];
  Square kingSquares[2];
  int minKPdistance[2];
  int castleRights[2];
  Score value;
  int halfOpenFiles[2];
  Score kingSafety[2];
};


/// The PawnTable class represents a pawn hash table. The most important
/// method is probe, which returns a pointer to a PawnEntry object.

struct PawnTable {

  PawnEntry* probe(const Position& pos);

  template<Color Us>
  static Score evaluate_pawns(const Position& pos, Bitboard ourPawns,
                              Bitboard theirPawns, PawnEntry* e);

  HashTable<PawnEntry, PawnTableSize> entries;
};


inline Score PawnEntry::pawns_value() const {
  return value;
}

inline Bitboard PawnEntry::pawn_attacks(Color c) const {
  return pawnAttacks[c];
}

inline Bitboard PawnEntry::passed_pawns(Color c) const {
  return passedPawns[c];
}

inline int PawnEntry::file_is_half_open(Color c, File f) const {
  return halfOpenFiles[c] & (1 << int(f));
}

inline int PawnEntry::has_open_file_to_left(Color c, File f) const {
  return halfOpenFiles[c] & ((1 << int(f)) - 1);
}

inline int PawnEntry::has_open_file_to_right(Color c, File f) const {
  return halfOpenFiles[c] & ~((1 << int(f+1)) - 1);
}

template<Color Us>
inline Score PawnEntry::king_safety(const Position& pos, Square ksq) {
  return kingSquares[Us] == ksq && castleRights[Us] == pos.can_castle(Us)
       ? kingSafety[Us] : update_safety<Us>(pos, ksq);
}

#endif // !defined(PAWNS_H_INCLUDED)