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;
54 class EndgameFunctions {
58 EndgameEvaluationFunction* getEEF(Key key);
59 ScalingInfo getESF(Key key);
62 void add(Key k, EndgameEvaluationFunction* f);
63 void add(Key k, Color c, ScalingFunction* f);
65 std::map<Key, EndgameEvaluationFunction*> EEFmap;
66 std::map<Key, ScalingInfo> ESFmap;
74 /// MaterialInfo::init() is called during program initialization. It
75 /// precomputes material hash keys for a few basic endgames, in order
76 /// to make it easy to recognize such endgames when they occur.
78 void MaterialInfo::init() {
80 typedef Key ZM[2][8][16];
81 const ZM& z = Position::zobMaterial;
83 KNNKMaterialKey = z[WHITE][KNIGHT][1] ^ z[WHITE][KNIGHT][2];
84 KKNNMaterialKey = z[BLACK][KNIGHT][1] ^ z[BLACK][KNIGHT][2];
88 /// Constructor for the MaterialInfoTable class
90 MaterialInfoTable::MaterialInfoTable(unsigned int numOfEntries) {
93 entries = new MaterialInfo[size];
94 funcs = new EndgameFunctions();
95 if (!entries || !funcs)
97 std::cerr << "Failed to allocate " << (numOfEntries * sizeof(MaterialInfo))
98 << " bytes for material hash table." << std::endl;
105 /// Destructor for the MaterialInfoTable class
107 MaterialInfoTable::~MaterialInfoTable() {
114 /// MaterialInfoTable::clear() clears a material hash table by setting
115 /// all entries to 0.
117 void MaterialInfoTable::clear() {
119 memset(entries, 0, size * sizeof(MaterialInfo));
123 /// MaterialInfoTable::get_material_info() takes a position object as input,
124 /// computes or looks up a MaterialInfo object, and returns a pointer to it.
125 /// If the material configuration is not already present in the table, it
126 /// is stored there, so we don't have to recompute everything when the
127 /// same material configuration occurs again.
129 MaterialInfo *MaterialInfoTable::get_material_info(const Position& pos) {
131 Key key = pos.get_material_key();
132 int index = key & (size - 1);
133 MaterialInfo* mi = entries + index;
135 // If mi->key matches the position's material hash key, it means that we
136 // have analysed this material configuration before, and we can simply
137 // return the information we found the last time instead of recomputing it.
141 // Clear the MaterialInfo object, and set its key
145 // A special case before looking for a specialized evaluation function
146 // KNN vs K is a draw.
147 if (key == KNNKMaterialKey || key == KKNNMaterialKey)
149 mi->factor[WHITE] = mi->factor[BLACK] = 0;
153 // Let's look if we have a specialized evaluation function for this
154 // particular material configuration.
155 if ((mi->evaluationFunction = funcs->getEEF(key)) != NULL)
158 else if ( pos.non_pawn_material(BLACK) == Value(0)
159 && pos.piece_count(BLACK, PAWN) == 0
160 && pos.non_pawn_material(WHITE) >= RookValueEndgame)
162 mi->evaluationFunction = &EvaluateKXK;
165 else if ( pos.non_pawn_material(WHITE) == Value(0)
166 && pos.piece_count(WHITE, PAWN) == 0
167 && pos.non_pawn_material(BLACK) >= RookValueEndgame)
169 mi->evaluationFunction = &EvaluateKKX;
173 // OK, we didn't find any special evaluation function for the current
174 // material configuration. Is there a suitable scaling function?
176 // The code below is rather messy, and it could easily get worse later,
177 // if we decide to add more special cases. We face problems when there
178 // are several conflicting applicable scaling functions and we need to
179 // decide which one to use.
180 ScalingInfo si = funcs->getESF(key);
183 mi->scalingFunction[si.col] = si.fun;
187 if ( pos.non_pawn_material(WHITE) == BishopValueMidgame
188 && pos.piece_count(WHITE, BISHOP) == 1
189 && pos.piece_count(WHITE, PAWN) >= 1)
190 mi->scalingFunction[WHITE] = &ScaleKBPK;
192 if ( pos.non_pawn_material(BLACK) == BishopValueMidgame
193 && pos.piece_count(BLACK, BISHOP) == 1
194 && pos.piece_count(BLACK, PAWN) >= 1)
195 mi->scalingFunction[BLACK] = &ScaleKKBP;
197 if ( pos.piece_count(WHITE, PAWN) == 0
198 && pos.non_pawn_material(WHITE) == QueenValueMidgame
199 && pos.piece_count(WHITE, QUEEN) == 1
200 && pos.piece_count(BLACK, ROOK) == 1
201 && pos.piece_count(BLACK, PAWN) >= 1)
202 mi->scalingFunction[WHITE] = &ScaleKQKRP;
204 else if ( pos.piece_count(BLACK, PAWN) == 0
205 && pos.non_pawn_material(BLACK) == QueenValueMidgame
206 && pos.piece_count(BLACK, QUEEN) == 1
207 && pos.piece_count(WHITE, ROOK) == 1
208 && pos.piece_count(WHITE, PAWN) >= 1)
209 mi->scalingFunction[BLACK] = &ScaleKRPKQ;
211 if (pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK) == Value(0))
213 if (pos.piece_count(BLACK, PAWN) == 0)
215 assert(pos.piece_count(WHITE, PAWN) >= 2);
216 mi->scalingFunction[WHITE] = &ScaleKPsK;
218 else if (pos.piece_count(WHITE, PAWN) == 0)
220 assert(pos.piece_count(BLACK, PAWN) >= 2);
221 mi->scalingFunction[BLACK] = &ScaleKKPs;
223 else if (pos.piece_count(WHITE, PAWN) == 1 && pos.piece_count(BLACK, PAWN) == 1)
225 mi->scalingFunction[WHITE] = &ScaleKPKPw;
226 mi->scalingFunction[BLACK] = &ScaleKPKPb;
230 // Evaluate the material balance
234 Value egValue = Value(0);
235 Value mgValue = Value(0);
237 for (c = WHITE, sign = 1; c <= BLACK; c++, sign = -sign)
239 // No pawns makes it difficult to win, even with a material advantage
240 if ( pos.piece_count(c, PAWN) == 0
241 && pos.non_pawn_material(c) - pos.non_pawn_material(opposite_color(c)) <= BishopValueMidgame)
243 if ( pos.non_pawn_material(c) == pos.non_pawn_material(opposite_color(c))
244 || pos.non_pawn_material(c) < RookValueMidgame)
248 switch (pos.piece_count(c, BISHOP)) {
263 if (pos.piece_count(c, BISHOP) >= 2)
265 mgValue += sign * BishopPairMidgameBonus;
266 egValue += sign * BishopPairEndgameBonus;
269 // Knights are stronger when there are many pawns on the board. The
270 // formula is taken from Larry Kaufman's paper "The Evaluation of Material
271 // Imbalances in Chess":
272 // http://mywebpages.comcast.net/danheisman/Articles/evaluation_of_material_imbalance.htm
273 mgValue += sign * Value(pos.piece_count(c, KNIGHT)*(pos.piece_count(c, PAWN)-5)*16);
274 egValue += sign * Value(pos.piece_count(c, KNIGHT)*(pos.piece_count(c, PAWN)-5)*16);
276 // Redundancy of major pieces, again based on Kaufman's paper:
277 if (pos.piece_count(c, ROOK) >= 1)
279 Value v = Value((pos.piece_count(c, ROOK) - 1) * 32 + pos.piece_count(c, QUEEN) * 16);
285 mi->mgValue = int16_t(mgValue);
286 mi->egValue = int16_t(egValue);
291 /// EndgameFunctions members definition. This helper class is used to
292 /// store the maps of end game and scaling functions that MaterialInfoTable
293 /// will query for each key. The maps are constant, and are populated only
294 /// at construction. Being per thread avoids to use locks to access them.
296 EndgameFunctions::EndgameFunctions() {
298 typedef Key ZM[2][8][16];
299 const ZM& z = Position::zobMaterial;
301 static const Color W = WHITE;
302 static const Color B = BLACK;
304 KNNKMaterialKey = z[W][KNIGHT][1] ^ z[W][KNIGHT][2];
305 KKNNMaterialKey = z[B][KNIGHT][1] ^ z[B][KNIGHT][2];
307 add(z[W][PAWN][1], &EvaluateKPK);
308 add(z[B][PAWN][1], &EvaluateKKP);
310 add(z[W][BISHOP][1] ^ z[W][KNIGHT][1], &EvaluateKBNK);
311 add(z[B][BISHOP][1] ^ z[B][KNIGHT][1], &EvaluateKKBN);
312 add(z[W][ROOK][1] ^ z[B][PAWN][1], &EvaluateKRKP);
313 add(z[W][PAWN][1] ^ z[B][ROOK][1], &EvaluateKPKR);
314 add(z[W][ROOK][1] ^ z[B][BISHOP][1], &EvaluateKRKB);
315 add(z[W][BISHOP][1] ^ z[B][ROOK][1], &EvaluateKBKR);
316 add(z[W][ROOK][1] ^ z[B][KNIGHT][1], &EvaluateKRKN);
317 add(z[W][KNIGHT][1] ^ z[B][ROOK][1], &EvaluateKNKR);
318 add(z[W][QUEEN][1] ^ z[B][ROOK][1], &EvaluateKQKR);
319 add(z[W][ROOK][1] ^ z[B][QUEEN][1], &EvaluateKRKQ);
321 add(z[W][KNIGHT][1] ^ z[W][PAWN][1], W, &ScaleKNPK);
322 add(z[B][KNIGHT][1] ^ z[B][PAWN][1], B, &ScaleKKNP);
324 add(z[W][ROOK][1] ^ z[W][PAWN][1] ^ z[B][ROOK][1] , W, &ScaleKRPKR);
325 add(z[W][ROOK][1] ^ z[B][ROOK][1] ^ z[B][PAWN][1] , B, &ScaleKRKRP);
326 add(z[W][BISHOP][1] ^ z[W][PAWN][1] ^ z[B][BISHOP][1], W, &ScaleKBPKB);
327 add(z[W][BISHOP][1] ^ z[B][BISHOP][1] ^ z[B][PAWN][1] , B, &ScaleKBKBP);
328 add(z[W][BISHOP][1] ^ z[W][PAWN][1] ^ z[B][KNIGHT][1], W, &ScaleKBPKN);
329 add(z[W][KNIGHT][1] ^ z[B][BISHOP][1] ^ z[B][PAWN][1] , B, &ScaleKNKBP);
331 add(z[W][ROOK][1] ^ z[W][PAWN][1] ^ z[W][PAWN][2] ^ z[B][ROOK][1] ^ z[B][PAWN][1], W, &ScaleKRPPKRP);
332 add(z[W][ROOK][1] ^ z[W][PAWN][1] ^ z[B][ROOK][1] ^ z[B][PAWN][1] ^ z[B][PAWN][2], B, &ScaleKRPKRPP);
335 void EndgameFunctions::add(Key k, EndgameEvaluationFunction* f) {
337 EEFmap.insert(std::pair<Key, EndgameEvaluationFunction*>(k, f));
340 void EndgameFunctions::add(Key k, Color c, ScalingFunction* f) {
342 ScalingInfo s = {c, f};
343 ESFmap.insert(std::pair<Key, ScalingInfo>(k, s));
346 EndgameEvaluationFunction* EndgameFunctions::getEEF(Key key) {
348 EndgameEvaluationFunction* f = NULL;
349 std::map<Key, EndgameEvaluationFunction*>::iterator it(EEFmap.find(key));
350 if (it != EEFmap.end())
356 ScalingInfo EndgameFunctions::getESF(Key key) {
358 ScalingInfo si = {WHITE, NULL};
359 std::map<Key, ScalingInfo>::iterator it(ESFmap.find(key));
360 if (it != ESFmap.end())