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 Marco Costalba
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/>.
32 //// Local definitions
37 const Value BishopPairMidgameBonus = Value(100);
38 const Value BishopPairEndgameBonus = Value(100);
40 Key KNNKMaterialKey, KKNNMaterialKey;
49 /// See header for a class description. It is declared here to avoid
50 /// to include <map> in the header file.
52 class EndgameFunctions {
56 EndgameEvaluationFunction* getEEF(Key key) const;
57 ScalingFunction* getESF(Key key, Color* c) const;
60 void add(Key k, EndgameEvaluationFunction* f);
61 void add(Key k, Color c, ScalingFunction* f);
69 std::map<Key, EndgameEvaluationFunction*> EEFmap;
70 std::map<Key, ScalingInfo> ESFmap;
79 /// Constructor for the MaterialInfoTable class
81 MaterialInfoTable::MaterialInfoTable(unsigned int numOfEntries) {
84 entries = new MaterialInfo[size];
85 funcs = new EndgameFunctions();
86 if (!entries || !funcs)
88 std::cerr << "Failed to allocate " << (numOfEntries * sizeof(MaterialInfo))
89 << " bytes for material hash table." << std::endl;
96 /// Destructor for the MaterialInfoTable class
98 MaterialInfoTable::~MaterialInfoTable() {
105 /// MaterialInfoTable::clear() clears a material hash table by setting
106 /// all entries to 0.
108 void MaterialInfoTable::clear() {
110 memset(entries, 0, size * sizeof(MaterialInfo));
114 /// MaterialInfoTable::get_material_info() takes a position object as input,
115 /// computes or looks up a MaterialInfo object, and returns a pointer to it.
116 /// If the material configuration is not already present in the table, it
117 /// is stored there, so we don't have to recompute everything when the
118 /// same material configuration occurs again.
120 MaterialInfo* MaterialInfoTable::get_material_info(const Position& pos) {
122 Key key = pos.get_material_key();
123 int index = key & (size - 1);
124 MaterialInfo* mi = entries + index;
126 // If mi->key matches the position's material hash key, it means that we
127 // have analysed this material configuration before, and we can simply
128 // return the information we found the last time instead of recomputing it.
132 // Clear the MaterialInfo object, and set its key
136 // A special case before looking for a specialized evaluation function
137 // KNN vs K is a draw.
138 if (key == KNNKMaterialKey || key == KKNNMaterialKey)
140 mi->factor[WHITE] = mi->factor[BLACK] = 0;
144 // Let's look if we have a specialized evaluation function for this
145 // particular material configuration.
146 if ((mi->evaluationFunction = funcs->getEEF(key)) != NULL)
149 else if ( pos.non_pawn_material(BLACK) == Value(0)
150 && pos.piece_count(BLACK, PAWN) == 0
151 && pos.non_pawn_material(WHITE) >= RookValueEndgame)
153 mi->evaluationFunction = &EvaluateKXK;
156 else if ( pos.non_pawn_material(WHITE) == Value(0)
157 && pos.piece_count(WHITE, PAWN) == 0
158 && pos.non_pawn_material(BLACK) >= RookValueEndgame)
160 mi->evaluationFunction = &EvaluateKKX;
164 // OK, we didn't find any special evaluation function for the current
165 // material configuration. Is there a suitable scaling function?
167 // The code below is rather messy, and it could easily get worse later,
168 // if we decide to add more special cases. We face problems when there
169 // are several conflicting applicable scaling functions and we need to
170 // decide which one to use.
174 if ((sf = funcs->getESF(key, &c)) != NULL)
176 mi->scalingFunction[c] = sf;
180 if ( pos.non_pawn_material(WHITE) == BishopValueMidgame
181 && pos.piece_count(WHITE, BISHOP) == 1
182 && pos.piece_count(WHITE, PAWN) >= 1)
183 mi->scalingFunction[WHITE] = &ScaleKBPK;
185 if ( pos.non_pawn_material(BLACK) == BishopValueMidgame
186 && pos.piece_count(BLACK, BISHOP) == 1
187 && pos.piece_count(BLACK, PAWN) >= 1)
188 mi->scalingFunction[BLACK] = &ScaleKKBP;
190 if ( pos.piece_count(WHITE, PAWN) == 0
191 && pos.non_pawn_material(WHITE) == QueenValueMidgame
192 && pos.piece_count(WHITE, QUEEN) == 1
193 && pos.piece_count(BLACK, ROOK) == 1
194 && pos.piece_count(BLACK, PAWN) >= 1)
195 mi->scalingFunction[WHITE] = &ScaleKQKRP;
197 else if ( pos.piece_count(BLACK, PAWN) == 0
198 && pos.non_pawn_material(BLACK) == QueenValueMidgame
199 && pos.piece_count(BLACK, QUEEN) == 1
200 && pos.piece_count(WHITE, ROOK) == 1
201 && pos.piece_count(WHITE, PAWN) >= 1)
202 mi->scalingFunction[BLACK] = &ScaleKRPKQ;
204 if (pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK) == Value(0))
206 if (pos.piece_count(BLACK, PAWN) == 0)
208 assert(pos.piece_count(WHITE, PAWN) >= 2);
209 mi->scalingFunction[WHITE] = &ScaleKPsK;
211 else if (pos.piece_count(WHITE, PAWN) == 0)
213 assert(pos.piece_count(BLACK, PAWN) >= 2);
214 mi->scalingFunction[BLACK] = &ScaleKKPs;
216 else if (pos.piece_count(WHITE, PAWN) == 1 && pos.piece_count(BLACK, PAWN) == 1)
218 mi->scalingFunction[WHITE] = &ScaleKPKPw;
219 mi->scalingFunction[BLACK] = &ScaleKPKPb;
223 // Evaluate the material balance
226 Value egValue = Value(0);
227 Value mgValue = Value(0);
229 for (c = WHITE, sign = 1; c <= BLACK; c++, sign = -sign)
231 // No pawns makes it difficult to win, even with a material advantage
232 if ( pos.piece_count(c, PAWN) == 0
233 && pos.non_pawn_material(c) - pos.non_pawn_material(opposite_color(c)) <= BishopValueMidgame)
235 if ( pos.non_pawn_material(c) == pos.non_pawn_material(opposite_color(c))
236 || pos.non_pawn_material(c) < RookValueMidgame)
240 switch (pos.piece_count(c, BISHOP)) {
255 if (pos.piece_count(c, BISHOP) >= 2)
257 mgValue += sign * BishopPairMidgameBonus;
258 egValue += sign * BishopPairEndgameBonus;
261 // Knights are stronger when there are many pawns on the board. The
262 // formula is taken from Larry Kaufman's paper "The Evaluation of Material
263 // Imbalances in Chess":
264 // http://mywebpages.comcast.net/danheisman/Articles/evaluation_of_material_imbalance.htm
265 mgValue += sign * Value(pos.piece_count(c, KNIGHT)*(pos.piece_count(c, PAWN)-5)*16);
266 egValue += sign * Value(pos.piece_count(c, KNIGHT)*(pos.piece_count(c, PAWN)-5)*16);
268 // Redundancy of major pieces, again based on Kaufman's paper:
269 if (pos.piece_count(c, ROOK) >= 1)
271 Value v = Value((pos.piece_count(c, ROOK) - 1) * 32 + pos.piece_count(c, QUEEN) * 16);
276 mi->mgValue = int16_t(mgValue);
277 mi->egValue = int16_t(egValue);
282 /// EndgameFunctions member definitions. This class is used to store the maps
283 /// of end game and scaling functions that MaterialInfoTable will query for
284 /// each key. The maps are constant and are populated only at construction,
285 /// but are per-thread instead of globals to avoid expensive locks.
287 EndgameFunctions::EndgameFunctions() {
289 typedef Key ZM[2][8][16];
290 const ZM& z = Position::zobMaterial;
292 static const Color W = WHITE;
293 static const Color B = BLACK;
295 KNNKMaterialKey = z[W][KNIGHT][1] ^ z[W][KNIGHT][2];
296 KKNNMaterialKey = z[B][KNIGHT][1] ^ z[B][KNIGHT][2];
298 add(z[W][PAWN][1], &EvaluateKPK);
299 add(z[B][PAWN][1], &EvaluateKKP);
301 add(z[W][BISHOP][1] ^ z[W][KNIGHT][1], &EvaluateKBNK);
302 add(z[B][BISHOP][1] ^ z[B][KNIGHT][1], &EvaluateKKBN);
303 add(z[W][ROOK][1] ^ z[B][PAWN][1], &EvaluateKRKP);
304 add(z[W][PAWN][1] ^ z[B][ROOK][1], &EvaluateKPKR);
305 add(z[W][ROOK][1] ^ z[B][BISHOP][1], &EvaluateKRKB);
306 add(z[W][BISHOP][1] ^ z[B][ROOK][1], &EvaluateKBKR);
307 add(z[W][ROOK][1] ^ z[B][KNIGHT][1], &EvaluateKRKN);
308 add(z[W][KNIGHT][1] ^ z[B][ROOK][1], &EvaluateKNKR);
309 add(z[W][QUEEN][1] ^ z[B][ROOK][1], &EvaluateKQKR);
310 add(z[W][ROOK][1] ^ z[B][QUEEN][1], &EvaluateKRKQ);
312 add(z[W][KNIGHT][1] ^ z[W][PAWN][1], W, &ScaleKNPK);
313 add(z[B][KNIGHT][1] ^ z[B][PAWN][1], B, &ScaleKKNP);
315 add(z[W][ROOK][1] ^ z[W][PAWN][1] ^ z[B][ROOK][1] , W, &ScaleKRPKR);
316 add(z[W][ROOK][1] ^ z[B][ROOK][1] ^ z[B][PAWN][1] , B, &ScaleKRKRP);
317 add(z[W][BISHOP][1] ^ z[W][PAWN][1] ^ z[B][BISHOP][1], W, &ScaleKBPKB);
318 add(z[W][BISHOP][1] ^ z[B][BISHOP][1] ^ z[B][PAWN][1] , B, &ScaleKBKBP);
319 add(z[W][BISHOP][1] ^ z[W][PAWN][1] ^ z[B][KNIGHT][1], W, &ScaleKBPKN);
320 add(z[W][KNIGHT][1] ^ z[B][BISHOP][1] ^ z[B][PAWN][1] , B, &ScaleKNKBP);
322 add(z[W][ROOK][1] ^ z[W][PAWN][1] ^ z[W][PAWN][2] ^ z[B][ROOK][1] ^ z[B][PAWN][1], W, &ScaleKRPPKRP);
323 add(z[W][ROOK][1] ^ z[W][PAWN][1] ^ z[B][ROOK][1] ^ z[B][PAWN][1] ^ z[B][PAWN][2], B, &ScaleKRPKRPP);
326 void EndgameFunctions::add(Key k, EndgameEvaluationFunction* f) {
328 EEFmap.insert(std::pair<Key, EndgameEvaluationFunction*>(k, f));
331 void EndgameFunctions::add(Key k, Color c, ScalingFunction* f) {
333 ScalingInfo s = {c, f};
334 ESFmap.insert(std::pair<Key, ScalingInfo>(k, s));
337 EndgameEvaluationFunction* EndgameFunctions::getEEF(Key key) const {
339 std::map<Key, EndgameEvaluationFunction*>::const_iterator it(EEFmap.find(key));
340 return (it != EEFmap.end() ? it->second : NULL);
343 ScalingFunction* EndgameFunctions::getESF(Key key, Color* c) const {
345 std::map<Key, ScalingInfo>::const_iterator it(ESFmap.find(key));
346 if (it == ESFmap.end())
350 return it->second.fun;