2 Stockfish, a UCI chess playing engine derived from Glaurung 2.1
3 Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
4 Copyright (C) 2008-2009 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/>.
34 //// Local definitions
39 // Values modified by Joona Kiiski
40 const Value BishopPairMidgameBonus = Value(109);
41 const Value BishopPairEndgameBonus = Value(97);
43 Key KNNKMaterialKey, KKNNMaterialKey;
45 // Unmapped endgame evaluation and scaling functions, these
46 // are accessed direcly and not through the function maps.
47 EvaluationFunction<KmmKm> EvaluateKmmKm(WHITE);
48 EvaluationFunction<KXK> EvaluateKXK(WHITE), EvaluateKKX(BLACK);
49 ScalingFunction<KBPK> ScaleKBPK(WHITE), ScaleKKBP(BLACK);
50 ScalingFunction<KQKRP> ScaleKQKRP(WHITE), ScaleKRPKQ(BLACK);
51 ScalingFunction<KPsK> ScaleKPsK(WHITE), ScaleKKPs(BLACK);
52 ScalingFunction<KPKP> ScaleKPKPw(WHITE), ScaleKPKPb(BLACK);
61 /// See header for a class description. It is declared here to avoid
62 /// to include <map> in the header file.
64 class EndgameFunctions {
66 typedef EndgameEvaluationFunctionBase EF;
67 typedef EndgameScalingFunctionBase SF;
72 template<class T> T* get(Key key) const;
75 template<class T> void add(const string& keyCode);
77 static Key buildKey(const string& keyCode);
78 static const string swapColors(const string& keyCode);
80 std::map<Key, EF*> EEFmap;
81 std::map<Key, SF*> ESFmap;
83 // Maps accessing functions for const and non-const references
84 template<typename T> const std::map<Key, T*>& map() const { return EEFmap; }
85 template<> const std::map<Key, SF*>& map<SF>() const { return ESFmap; }
86 template<typename T> std::map<Key, T*>& map() { return EEFmap; }
87 template<> std::map<Key, SF*>& map<SF>() { return ESFmap; }
96 /// Constructor for the MaterialInfoTable class
98 MaterialInfoTable::MaterialInfoTable(unsigned int numOfEntries) {
101 entries = new MaterialInfo[size];
102 funcs = new EndgameFunctions();
103 if (!entries || !funcs)
105 std::cerr << "Failed to allocate " << (numOfEntries * sizeof(MaterialInfo))
106 << " bytes for material hash table." << std::endl;
107 Application::exit_with_failure();
112 /// Destructor for the MaterialInfoTable class
114 MaterialInfoTable::~MaterialInfoTable() {
121 /// MaterialInfoTable::get_material_info() takes a position object as input,
122 /// computes or looks up a MaterialInfo object, and returns a pointer to it.
123 /// If the material configuration is not already present in the table, it
124 /// is stored there, so we don't have to recompute everything when the
125 /// same material configuration occurs again.
127 MaterialInfo* MaterialInfoTable::get_material_info(const Position& pos) {
129 Key key = pos.get_material_key();
130 int index = key & (size - 1);
131 MaterialInfo* mi = entries + index;
133 // If mi->key matches the position's material hash key, it means that we
134 // have analysed this material configuration before, and we can simply
135 // return the information we found the last time instead of recomputing it.
139 // Clear the MaterialInfo object, and set its key
143 // A special case before looking for a specialized evaluation function
144 // KNN vs K is a draw.
145 if (key == KNNKMaterialKey || key == KKNNMaterialKey)
147 mi->factor[WHITE] = mi->factor[BLACK] = 0;
151 // Let's look if we have a specialized evaluation function for this
152 // particular material configuration. First we look for a fixed
153 // configuration one, then a generic one if previous search failed.
154 if ((mi->evaluationFunction = funcs->get<EndgameEvaluationFunctionBase>(key)) != NULL)
157 else if ( pos.non_pawn_material(BLACK) == Value(0)
158 && pos.piece_count(BLACK, PAWN) == 0
159 && pos.non_pawn_material(WHITE) >= RookValueMidgame)
161 mi->evaluationFunction = &EvaluateKXK;
164 else if ( pos.non_pawn_material(WHITE) == Value(0)
165 && pos.piece_count(WHITE, PAWN) == 0
166 && pos.non_pawn_material(BLACK) >= RookValueMidgame)
168 mi->evaluationFunction = &EvaluateKKX;
171 else if ( pos.pawns() == EmptyBoardBB
172 && pos.rooks() == EmptyBoardBB
173 && pos.queens() == EmptyBoardBB)
175 // Minor piece endgame with at least one minor piece per side,
177 assert(pos.knights(WHITE) | pos.bishops(WHITE));
178 assert(pos.knights(BLACK) | pos.bishops(BLACK));
180 if ( pos.piece_count(WHITE, BISHOP) + pos.piece_count(WHITE, KNIGHT) <= 2
181 && pos.piece_count(BLACK, BISHOP) + pos.piece_count(BLACK, KNIGHT) <= 2)
183 mi->evaluationFunction = &EvaluateKmmKm;
188 // OK, we didn't find any special evaluation function for the current
189 // material configuration. Is there a suitable scaling function?
191 // The code below is rather messy, and it could easily get worse later,
192 // if we decide to add more special cases. We face problems when there
193 // are several conflicting applicable scaling functions and we need to
194 // decide which one to use.
195 EndgameScalingFunctionBase* sf;
197 if ((sf = funcs->get<EndgameScalingFunctionBase>(key)) != NULL)
199 mi->scalingFunction[sf->color()] = sf;
203 if ( pos.non_pawn_material(WHITE) == BishopValueMidgame
204 && pos.piece_count(WHITE, BISHOP) == 1
205 && pos.piece_count(WHITE, PAWN) >= 1)
206 mi->scalingFunction[WHITE] = &ScaleKBPK;
208 if ( pos.non_pawn_material(BLACK) == BishopValueMidgame
209 && pos.piece_count(BLACK, BISHOP) == 1
210 && pos.piece_count(BLACK, PAWN) >= 1)
211 mi->scalingFunction[BLACK] = &ScaleKKBP;
213 if ( pos.piece_count(WHITE, PAWN) == 0
214 && pos.non_pawn_material(WHITE) == QueenValueMidgame
215 && pos.piece_count(WHITE, QUEEN) == 1
216 && pos.piece_count(BLACK, ROOK) == 1
217 && pos.piece_count(BLACK, PAWN) >= 1)
218 mi->scalingFunction[WHITE] = &ScaleKQKRP;
220 else if ( pos.piece_count(BLACK, PAWN) == 0
221 && pos.non_pawn_material(BLACK) == QueenValueMidgame
222 && pos.piece_count(BLACK, QUEEN) == 1
223 && pos.piece_count(WHITE, ROOK) == 1
224 && pos.piece_count(WHITE, PAWN) >= 1)
225 mi->scalingFunction[BLACK] = &ScaleKRPKQ;
227 if (pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK) == Value(0))
229 if (pos.piece_count(BLACK, PAWN) == 0)
231 assert(pos.piece_count(WHITE, PAWN) >= 2);
232 mi->scalingFunction[WHITE] = &ScaleKPsK;
234 else if (pos.piece_count(WHITE, PAWN) == 0)
236 assert(pos.piece_count(BLACK, PAWN) >= 2);
237 mi->scalingFunction[BLACK] = &ScaleKKPs;
239 else if (pos.piece_count(WHITE, PAWN) == 1 && pos.piece_count(BLACK, PAWN) == 1)
241 mi->scalingFunction[WHITE] = &ScaleKPKPw;
242 mi->scalingFunction[BLACK] = &ScaleKPKPb;
246 // Compute the space weight
247 if (pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK) >=
248 2*QueenValueMidgame + 4*RookValueMidgame + 2*KnightValueMidgame)
250 int minorPieceCount = pos.piece_count(WHITE, KNIGHT)
251 + pos.piece_count(BLACK, KNIGHT)
252 + pos.piece_count(WHITE, BISHOP)
253 + pos.piece_count(BLACK, BISHOP);
255 mi->spaceWeight = minorPieceCount * minorPieceCount;
258 // Evaluate the material balance
262 Value egValue = Value(0);
263 Value mgValue = Value(0);
265 for (c = WHITE, sign = 1; c <= BLACK; c++, sign = -sign)
267 // No pawns makes it difficult to win, even with a material advantage
268 if ( pos.piece_count(c, PAWN) == 0
269 && pos.non_pawn_material(c) - pos.non_pawn_material(opposite_color(c)) <= BishopValueMidgame)
271 if ( pos.non_pawn_material(c) == pos.non_pawn_material(opposite_color(c))
272 || pos.non_pawn_material(c) < RookValueMidgame)
276 switch (pos.piece_count(c, BISHOP)) {
291 if (pos.piece_count(c, BISHOP) >= 2)
293 mgValue += sign * BishopPairMidgameBonus;
294 egValue += sign * BishopPairEndgameBonus;
297 // Knights are stronger when there are many pawns on the board. The
298 // formula is taken from Larry Kaufman's paper "The Evaluation of Material
299 // Imbalances in Chess":
300 // http://mywebpages.comcast.net/danheisman/Articles/evaluation_of_material_imbalance.htm
301 mgValue += sign * Value(pos.piece_count(c, KNIGHT)*(pos.piece_count(c, PAWN)-5)*16);
302 egValue += sign * Value(pos.piece_count(c, KNIGHT)*(pos.piece_count(c, PAWN)-5)*16);
304 // Redundancy of major pieces, again based on Kaufman's paper:
305 if (pos.piece_count(c, ROOK) >= 1)
307 Value v = Value((pos.piece_count(c, ROOK) - 1) * 32 + pos.piece_count(c, QUEEN) * 16);
312 mi->mgValue = int16_t(mgValue);
313 mi->egValue = int16_t(egValue);
318 /// EndgameFunctions member definitions. This class is used to store the maps
319 /// of end game and scaling functions that MaterialInfoTable will query for
320 /// each key. The maps are constant and are populated only at construction,
321 /// but are per-thread instead of globals to avoid expensive locks needed
322 /// because std::map is not guaranteed to be thread-safe even if accessed
323 /// only for a lookup.
325 EndgameFunctions::EndgameFunctions() {
327 KNNKMaterialKey = buildKey("KNNK");
328 KKNNMaterialKey = buildKey("KKNN");
330 add<EvaluationFunction<KPK> >("KPK");
331 add<EvaluationFunction<KBNK> >("KBNK");
332 add<EvaluationFunction<KRKP> >("KRKP");
333 add<EvaluationFunction<KRKB> >("KRKB");
334 add<EvaluationFunction<KRKN> >("KRKN");
335 add<EvaluationFunction<KQKR> >("KQKR");
336 add<EvaluationFunction<KBBKN> >("KBBKN");
338 add<ScalingFunction<KNPK> >("KNPK");
339 add<ScalingFunction<KRPKR> >("KRPKR");
340 add<ScalingFunction<KBPKB> >("KBPKB");
341 add<ScalingFunction<KBPPKB> >("KBPPKB");
342 add<ScalingFunction<KBPKN> >("KBPKN");
343 add<ScalingFunction<KRPPKRP> >("KRPPKRP");
344 add<ScalingFunction<KRPPKRP> >("KRPPKRP");
347 EndgameFunctions::~EndgameFunctions() {
349 for (std::map<Key, EF*>::iterator it = EEFmap.begin(); it != EEFmap.end(); ++it)
352 for (std::map<Key, SF*>::iterator it = ESFmap.begin(); it != ESFmap.end(); ++it)
356 Key EndgameFunctions::buildKey(const string& keyCode) {
358 assert(keyCode.length() > 0 && keyCode[0] == 'K');
359 assert(keyCode.length() < 8);
364 // Build up a fen substring with the given pieces, note
365 // that the fen string could be of an illegal position.
366 for (size_t i = 0; i < keyCode.length(); i++)
368 if (keyCode[i] == 'K')
371 s << char(upcase? toupper(keyCode[i]) : tolower(keyCode[i]));
373 s << 8 - keyCode.length() << "/8/8/8/8/8/8/8 w -";
374 return Position(s.str()).get_material_key();
377 const string EndgameFunctions::swapColors(const string& keyCode) {
379 // Build corresponding key for the opposite color: "KBPKN" -> "KNKBP"
380 size_t idx = keyCode.find("K", 1);
381 return keyCode.substr(idx) + keyCode.substr(0, idx);
385 void EndgameFunctions::add(const string& keyCode) {
387 typedef typename T::Base F;
389 map<F>().insert(std::pair<Key, F*>(buildKey(keyCode), new T(WHITE)));
390 map<F>().insert(std::pair<Key, F*>(buildKey(swapColors(keyCode)), new T(BLACK)));
394 T* EndgameFunctions::get(Key key) const {
396 std::map<Key, T*>::const_iterator it(map<T>().find(key));
397 return (it != map<T>().end() ? it->second : NULL);