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  1. /*
  2.   Stockfish, a UCI chess playing engine derived from Glaurung 2.1
  3.   Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
  4.   Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad
  5.   Copyright (C) 2015-2018 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
  6.  
  7.   Stockfish is free software: you can redistribute it and/or modify
  8.   it under the terms of the GNU General Public License as published by
  9.   the Free Software Foundation, either version 3 of the License, or
  10.   (at your option) any later version.
  11.  
  12.   Stockfish is distributed in the hope that it will be useful,
  13.   but WITHOUT ANY WARRANTY; without even the implied warranty of
  14.   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15.   GNU General Public License for more details.
  16.  
  17.   You should have received a copy of the GNU General Public License
  18.   along with this program.  If not, see <http://www.gnu.org/licenses/>.
  19. */
  20.  
  21. #ifndef MATERIAL_H_INCLUDED
  22. #define MATERIAL_H_INCLUDED
  23.  
  24. #include "endgame.h"
  25. #include "misc.h"
  26. #include "position.h"
  27. #include "types.h"
  28.  
  29. namespace Material {
  30.  
  31. /// Material::Entry contains various information about a material configuration.
  32. /// It contains a material imbalance evaluation, a function pointer to a special
  33. /// endgame evaluation function (which in most cases is NULL, meaning that the
  34. /// standard evaluation function will be used), and scale factors.
  35. ///
  36. /// The scale factors are used to scale the evaluation score up or down. For
  37. /// instance, in KRB vs KR endgames, the score is scaled down by a factor of 4,
  38. /// which will result in scores of absolute value less than one pawn.
  39.  
  40. struct Entry {
  41.  
  42.   Score imbalance() const { return make_score(value, value); }
  43.   Phase game_phase() const { return gamePhase; }
  44.   bool specialized_eval_exists() const { return evaluationFunction != nullptr; }
  45.   Value evaluate(const Position& pos) const { return (*evaluationFunction)(pos); }
  46.  
  47.   // scale_factor takes a position and a color as input and returns a scale factor
  48.   // for the given color. We have to provide the position in addition to the color
  49.   // because the scale factor may also be a function which should be applied to
  50.   // the position. For instance, in KBP vs K endgames, the scaling function looks
  51.   // for rook pawns and wrong-colored bishops.
  52.   ScaleFactor scale_factor(const Position& pos, Color c) const {
  53.     ScaleFactor sf = scalingFunction[c] ? (*scalingFunction[c])(pos)
  54.                                         :  SCALE_FACTOR_NONE;
  55.     return sf != SCALE_FACTOR_NONE ? sf : ScaleFactor(factor[c]);
  56.   }
  57.  
  58.   Key key;
  59.   EndgameBase<Value>* evaluationFunction;
  60.   EndgameBase<ScaleFactor>* scalingFunction[COLOR_NB]; // Could be one for each
  61.                                                        // side (e.g. KPKP, KBPsKs)
  62.   int16_t value;
  63.   uint8_t factor[COLOR_NB];
  64.   Phase gamePhase;
  65. };
  66.  
  67. typedef HashTable<Entry, 8192> Table;
  68.  
  69. Entry* probe(const Position& pos);
  70.  
  71. } // namespace Material
  72.  
  73. #endif // #ifndef MATERIAL_H_INCLUDED
  74.