2 Stockfish, a UCI chess playing engine derived from Glaurung 2.1
3 Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
4 Copyright (C) 2008-2010 Marco Costalba, Joona Kiiski, Tord Romstad
6 Stockfish is free software: you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation, either version 3 of the License, or
9 (at your option) any later version.
11 Stockfish is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
16 You should have received a copy of the GNU General Public License
17 along with this program. If not, see <http://www.gnu.org/licenses/>.
21 #if !defined(MATERIAL_H_INCLUDED)
22 #define MATERIAL_H_INCLUDED
36 /// MaterialInfo is a class which contains various information about a
37 /// material configuration. It contains a material balance evaluation,
38 /// a function pointer to a special endgame evaluation function (which in
39 /// most cases is NULL, meaning that the standard evaluation function will
40 /// be used), and "scale factors" for black and white.
42 /// The scale factors are used to scale the evaluation score up or down.
43 /// For instance, in KRB vs KR endgames, the score is scaled down by a factor
44 /// of 4, which will result in scores of absolute value less than one pawn.
48 friend class MaterialInfoTable;
51 MaterialInfo() : key(0) { clear(); }
53 Score material_value() const;
54 ScaleFactor scale_factor(const Position& pos, Color c) const;
55 int space_weight() const;
56 Phase game_phase() const;
57 bool specialized_eval_exists() const;
58 Value evaluate(const Position& pos) const;
66 EndgameEvaluationFunctionBase* evaluationFunction;
67 EndgameScalingFunctionBase* scalingFunction[2];
72 /// The MaterialInfoTable class represents a pawn hash table. It is basically
73 /// just an array of MaterialInfo objects and a few methods for accessing these
74 /// objects. The most important method is get_material_info, which looks up a
75 /// position in the table and returns a pointer to a MaterialInfo object.
76 class EndgameFunctions;
78 class MaterialInfoTable {
81 MaterialInfoTable(unsigned numOfEntries);
83 MaterialInfo* get_material_info(const Position& pos);
85 static Phase game_phase(const Position& pos);
89 MaterialInfo* entries;
90 EndgameFunctions* funcs;
99 /// MaterialInfo::material_value simply returns the material balance
100 /// evaluation that is independent from game phase.
102 inline Score MaterialInfo::material_value() const {
104 return make_score(value, value);
108 /// MaterialInfo::clear() resets a MaterialInfo object to an empty state,
109 /// with all slots at their default values but the key.
111 inline void MaterialInfo::clear() {
114 factor[WHITE] = factor[BLACK] = uint8_t(SCALE_FACTOR_NORMAL);
115 evaluationFunction = NULL;
116 scalingFunction[WHITE] = scalingFunction[BLACK] = NULL;
121 /// MaterialInfo::scale_factor takes a position and a color as input, and
122 /// returns a scale factor for the given color. We have to provide the
123 /// position in addition to the color, because the scale factor need not
124 /// to be a constant: It can also be a function which should be applied to
125 /// the position. For instance, in KBP vs K endgames, a scaling function
126 /// which checks for draws with rook pawns and wrong-colored bishops.
128 inline ScaleFactor MaterialInfo::scale_factor(const Position& pos, Color c) const {
130 if (scalingFunction[c] != NULL)
132 ScaleFactor sf = scalingFunction[c]->apply(pos);
133 if (sf != SCALE_FACTOR_NONE)
136 return ScaleFactor(factor[c]);
140 /// MaterialInfo::space_weight() simply returns the weight for the space
141 /// evaluation for this material configuration.
143 inline int MaterialInfo::space_weight() const {
148 /// MaterialInfo::game_phase() returns the game phase according
149 /// to this material configuration.
151 inline Phase MaterialInfo::game_phase() const {
157 /// MaterialInfo::specialized_eval_exists decides whether there is a
158 /// specialized evaluation function for the current material configuration,
159 /// or if the normal evaluation function should be used.
161 inline bool MaterialInfo::specialized_eval_exists() const {
163 return evaluationFunction != NULL;
167 /// MaterialInfo::evaluate applies a specialized evaluation function
168 /// to a given position object. It should only be called when
169 /// specialized_eval_exists() returns 'true'.
171 inline Value MaterialInfo::evaluate(const Position& pos) const {
173 return evaluationFunction->apply(pos);
176 #endif // !defined(MATERIAL_H_INCLUDED)