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) 2015-2019 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
29namespace 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
40struct 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 const EndgameBase<Value>* evaluationFunction;
60 const EndgameBase<ScaleFactor>* scalingFunction[COLOR_NB]; // Could be one for each
61 // side (e.g. KPKP, KBPsK)
62 int16_t value;
63 uint8_t factor[COLOR_NB];
64 Phase gamePhase;
65};
66
67typedef HashTable<Entry, 8192> Table;
68
69Entry* probe(const Position& pos);
70
71} // namespace Material
72
73#endif // #ifndef MATERIAL_H_INCLUDED
74