Subversion Repositories Games.Chess Giants

/*

  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 MATERIAL_H_INCLUDED

#define MATERIAL_H_INCLUDED

#include "endgame.h"

#include "misc.h"

#include "position.h"

#include "types.h"

namespace Material {

/// Material::Entry contains various information about a material configuration.

/// It contains a material imbalance evaluation, a function pointer to a special

/// endgame evaluation function (which in most cases is NULL, meaning that the

/// standard evaluation function will be used), and scale factors.

///

/// The scale factors are used to scale the evaluation score up or down. For

/// instance, in KRB vs KR endgames, the score is scaled down by a factor of 4,

/// which will result in scores of absolute value less than one pawn.

struct Entry {

  Score imbalance() const { return make_score(value, value); }

  Phase game_phase() const { return gamePhase; }

  bool specialized_eval_exists() const { return evaluationFunction != nullptr; }

  Value evaluate(const Position& pos) const { return (*evaluationFunction)(pos); }

  // scale_factor takes a position and a color as input and returns a scale factor

  // for the given color. We have to provide the position in addition to the color

  // because the scale factor may also be a function which should be applied to

  // the position. For instance, in KBP vs K endgames, the scaling function looks

  // for rook pawns and wrong-colored bishops.

  ScaleFactor scale_factor(const Position& pos, Color c) const {

    ScaleFactor sf = scalingFunction[c] ? (*scalingFunction[c])(pos)

                                        :  SCALE_FACTOR_NONE;

    return sf != SCALE_FACTOR_NONE ? sf : ScaleFactor(factor[c]);

  }

  Key key;

  const EndgameBase<Value>* evaluationFunction;

  const EndgameBase<ScaleFactor>* scalingFunction[COLOR_NB]; // Could be one for each

                                                             // side (e.g. KPKP, KBPsKs)

  int16_t value;

  uint8_t factor[COLOR_NB];

  Phase gamePhase;

};

typedef HashTable<Entry, 8192> Table;

Entry* probe(const Position& pos);

} // namespace Material

#endif // #ifndef MATERIAL_H_INCLUDED