stockfish/src/pawns.h

/*
  Stockfish, a UCI chess playing engine derived from Glaurung 2.1
  Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
  Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad
  Copyright (C) 2015-2019 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
  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/>.
*/

#ifndef PAWNS_H_INCLUDED
#define PAWNS_H_INCLUDED

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

namespace Pawns {

/// Pawns::Entry contains various information about a pawn structure. A lookup
/// to the pawn hash table (performed by calling the probe function) returns a
/// pointer to an Entry object.

struct Entry {

  Score pawn_score(Color c) const { return scores[c]; }
  Bitboard pawn_attacks(Color c) const { return pawnAttacks[c]; }
  Bitboard passed_pawns(Color c) const { return passedPawns[c]; }
  Bitboard pawn_attacks_span(Color c) const { return pawnAttacksSpan[c]; }
  int weak_unopposed(Color c) const { return weakUnopposed[c]; }
  int passed_count() const { return popcount(passedPawns[WHITE] | passedPawns[BLACK]); };

  template<Color Us>
  Score king_safety(const Position& pos) {
    return  kingSquares[Us] == pos.square<KING>(Us) && castlingRights[Us] == pos.castling_rights(Us)
          ? kingSafety[Us] : (kingSafety[Us] = do_king_safety<Us>(pos));
  }

  template<Color Us>
  Score do_king_safety(const Position& pos);

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

  Key key;
  Score scores[COLOR_NB];
  Bitboard passedPawns[COLOR_NB];
  Bitboard pawnAttacks[COLOR_NB];
  Bitboard pawnAttacksSpan[COLOR_NB];
  Square kingSquares[COLOR_NB];
  Score kingSafety[COLOR_NB];
  int weakUnopposed[COLOR_NB];
  int castlingRights[COLOR_NB];
  int pawnsOnSquares[COLOR_NB][COLOR_NB]; // [color][light/dark squares]
};

typedef HashTable<Entry, 16384> Table;

Entry* probe(const Position& pos);

} // namespace Pawns

#endif // #ifndef PAWNS_H_INCLUDED