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);
60 typedef EndgameEvaluationFunctionBase EF;
61 typedef EndgameScalingFunctionBase SF;
63 /// See header for a class description. It is declared here to avoid
64 /// to include <map> in the header file.
66 class EndgameFunctions {
70 template<class T> T* get(Key key) const;
73 template<class T> void add(const string& keyCode);
75 static Key buildKey(const string& keyCode);
76 static const string swapColors(const string& keyCode);
78 std::map<Key, EF*> EEFmap;
79 std::map<Key, SF*> ESFmap;
81 // Maps accessing functions for const and non-const references
82 template<typename T> const std::map<Key, T*>& map() const { return EEFmap; }
83 template<typename T> std::map<Key, T*>& map() { return EEFmap; }
86 // Explicit specializations of a member function shall be declared in
87 // the namespace of which the class template is a member.
88 template<> const std::map<Key, SF*>&
89 EndgameFunctions::map<SF>() const { return ESFmap; }
91 template<> std::map<Key, SF*>&
92 EndgameFunctions::map<SF>() { return ESFmap; }
100 /// Constructor for the MaterialInfoTable class
102 MaterialInfoTable::MaterialInfoTable(unsigned int numOfEntries) {
105 entries = new MaterialInfo[size];
106 funcs = new EndgameFunctions();
107 if (!entries || !funcs)
109 std::cerr << "Failed to allocate " << (numOfEntries * sizeof(MaterialInfo))
110 << " bytes for material hash table." << std::endl;
111 Application::exit_with_failure();
116 /// Destructor for the MaterialInfoTable class
118 MaterialInfoTable::~MaterialInfoTable() {
125 /// MaterialInfoTable::get_material_info() takes a position object as input,
126 /// computes or looks up a MaterialInfo object, and returns a pointer to it.
127 /// If the material configuration is not already present in the table, it
128 /// is stored there, so we don't have to recompute everything when the
129 /// same material configuration occurs again.
131 MaterialInfo* MaterialInfoTable::get_material_info(const Position& pos) {
133 Key key = pos.get_material_key();
134 int index = key & (size - 1);
135 MaterialInfo* mi = entries + index;
137 // If mi->key matches the position's material hash key, it means that we
138 // have analysed this material configuration before, and we can simply
139 // return the information we found the last time instead of recomputing it.
143 // Clear the MaterialInfo object, and set its key
147 // A special case before looking for a specialized evaluation function
148 // KNN vs K is a draw.
149 if (key == KNNKMaterialKey || key == KKNNMaterialKey)
151 mi->factor[WHITE] = mi->factor[BLACK] = 0;
155 // Let's look if we have a specialized evaluation function for this
156 // particular material configuration. First we look for a fixed
157 // configuration one, then a generic one if previous search failed.
158 if ((mi->evaluationFunction = funcs->get<EF>(key)) != NULL)
161 else if ( pos.non_pawn_material(BLACK) == Value(0)
162 && pos.piece_count(BLACK, PAWN) == 0
163 && pos.non_pawn_material(WHITE) >= RookValueMidgame)
165 mi->evaluationFunction = &EvaluateKXK;
168 else if ( pos.non_pawn_material(WHITE) == Value(0)
169 && pos.piece_count(WHITE, PAWN) == 0
170 && pos.non_pawn_material(BLACK) >= RookValueMidgame)
172 mi->evaluationFunction = &EvaluateKKX;
175 else if ( pos.pawns() == EmptyBoardBB
176 && pos.rooks() == EmptyBoardBB
177 && pos.queens() == EmptyBoardBB)
179 // Minor piece endgame with at least one minor piece per side,
181 assert(pos.knights(WHITE) | pos.bishops(WHITE));
182 assert(pos.knights(BLACK) | pos.bishops(BLACK));
184 if ( pos.piece_count(WHITE, BISHOP) + pos.piece_count(WHITE, KNIGHT) <= 2
185 && pos.piece_count(BLACK, BISHOP) + pos.piece_count(BLACK, KNIGHT) <= 2)
187 mi->evaluationFunction = &EvaluateKmmKm;
192 // OK, we didn't find any special evaluation function for the current
193 // material configuration. Is there a suitable scaling function?
195 // The code below is rather messy, and it could easily get worse later,
196 // if we decide to add more special cases. We face problems when there
197 // are several conflicting applicable scaling functions and we need to
198 // decide which one to use.
201 if ((sf = funcs->get<SF>(key)) != NULL)
203 mi->scalingFunction[sf->color()] = sf;
207 if ( pos.non_pawn_material(WHITE) == BishopValueMidgame
208 && pos.piece_count(WHITE, BISHOP) == 1
209 && pos.piece_count(WHITE, PAWN) >= 1)
210 mi->scalingFunction[WHITE] = &ScaleKBPK;
212 if ( pos.non_pawn_material(BLACK) == BishopValueMidgame
213 && pos.piece_count(BLACK, BISHOP) == 1
214 && pos.piece_count(BLACK, PAWN) >= 1)
215 mi->scalingFunction[BLACK] = &ScaleKKBP;
217 if ( pos.piece_count(WHITE, PAWN) == 0
218 && pos.non_pawn_material(WHITE) == QueenValueMidgame
219 && pos.piece_count(WHITE, QUEEN) == 1
220 && pos.piece_count(BLACK, ROOK) == 1
221 && pos.piece_count(BLACK, PAWN) >= 1)
222 mi->scalingFunction[WHITE] = &ScaleKQKRP;
224 else if ( pos.piece_count(BLACK, PAWN) == 0
225 && pos.non_pawn_material(BLACK) == QueenValueMidgame
226 && pos.piece_count(BLACK, QUEEN) == 1
227 && pos.piece_count(WHITE, ROOK) == 1
228 && pos.piece_count(WHITE, PAWN) >= 1)
229 mi->scalingFunction[BLACK] = &ScaleKRPKQ;
231 if (pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK) == Value(0))
233 if (pos.piece_count(BLACK, PAWN) == 0)
235 assert(pos.piece_count(WHITE, PAWN) >= 2);
236 mi->scalingFunction[WHITE] = &ScaleKPsK;
238 else if (pos.piece_count(WHITE, PAWN) == 0)
240 assert(pos.piece_count(BLACK, PAWN) >= 2);
241 mi->scalingFunction[BLACK] = &ScaleKKPs;
243 else if (pos.piece_count(WHITE, PAWN) == 1 && pos.piece_count(BLACK, PAWN) == 1)
245 mi->scalingFunction[WHITE] = &ScaleKPKPw;
246 mi->scalingFunction[BLACK] = &ScaleKPKPb;
250 // Compute the space weight
251 if (pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK) >=
252 2*QueenValueMidgame + 4*RookValueMidgame + 2*KnightValueMidgame)
254 int minorPieceCount = pos.piece_count(WHITE, KNIGHT)
255 + pos.piece_count(BLACK, KNIGHT)
256 + pos.piece_count(WHITE, BISHOP)
257 + pos.piece_count(BLACK, BISHOP);
259 mi->spaceWeight = minorPieceCount * minorPieceCount;
262 // Evaluate the material balance
266 Value egValue = Value(0);
267 Value mgValue = Value(0);
269 for (c = WHITE, sign = 1; c <= BLACK; c++, sign = -sign)
271 // No pawns makes it difficult to win, even with a material advantage
272 if ( pos.piece_count(c, PAWN) == 0
273 && pos.non_pawn_material(c) - pos.non_pawn_material(opposite_color(c)) <= BishopValueMidgame)
275 if ( pos.non_pawn_material(c) == pos.non_pawn_material(opposite_color(c))
276 || pos.non_pawn_material(c) < RookValueMidgame)
280 switch (pos.piece_count(c, BISHOP)) {
295 if (pos.piece_count(c, BISHOP) >= 2)
297 mgValue += sign * BishopPairMidgameBonus;
298 egValue += sign * BishopPairEndgameBonus;
301 // Knights are stronger when there are many pawns on the board. The
302 // formula is taken from Larry Kaufman's paper "The Evaluation of Material
303 // Imbalances in Chess":
304 // http://mywebpages.comcast.net/danheisman/Articles/evaluation_of_material_imbalance.htm
305 mgValue += sign * Value(pos.piece_count(c, KNIGHT)*(pos.piece_count(c, PAWN)-5)*16);
306 egValue += sign * Value(pos.piece_count(c, KNIGHT)*(pos.piece_count(c, PAWN)-5)*16);
308 // Redundancy of major pieces, again based on Kaufman's paper:
309 if (pos.piece_count(c, ROOK) >= 1)
311 Value v = Value((pos.piece_count(c, ROOK) - 1) * 32 + pos.piece_count(c, QUEEN) * 16);
316 mi->mgValue = int16_t(mgValue);
317 mi->egValue = int16_t(egValue);
322 /// EndgameFunctions member definitions. This class is used to store the maps
323 /// of end game and scaling functions that MaterialInfoTable will query for
324 /// each key. The maps are constant and are populated only at construction,
325 /// but are per-thread instead of globals to avoid expensive locks needed
326 /// because std::map is not guaranteed to be thread-safe even if accessed
327 /// only for a lookup.
329 EndgameFunctions::EndgameFunctions() {
331 KNNKMaterialKey = buildKey("KNNK");
332 KKNNMaterialKey = buildKey("KKNN");
334 add<EvaluationFunction<KPK> >("KPK");
335 add<EvaluationFunction<KBNK> >("KBNK");
336 add<EvaluationFunction<KRKP> >("KRKP");
337 add<EvaluationFunction<KRKB> >("KRKB");
338 add<EvaluationFunction<KRKN> >("KRKN");
339 add<EvaluationFunction<KQKR> >("KQKR");
340 add<EvaluationFunction<KBBKN> >("KBBKN");
342 add<ScalingFunction<KNPK> >("KNPK");
343 add<ScalingFunction<KRPKR> >("KRPKR");
344 add<ScalingFunction<KBPKB> >("KBPKB");
345 add<ScalingFunction<KBPPKB> >("KBPPKB");
346 add<ScalingFunction<KBPKN> >("KBPKN");
347 add<ScalingFunction<KRPPKRP> >("KRPPKRP");
348 add<ScalingFunction<KRPPKRP> >("KRPPKRP");
351 EndgameFunctions::~EndgameFunctions() {
353 for (std::map<Key, EF*>::iterator it = EEFmap.begin(); it != EEFmap.end(); ++it)
356 for (std::map<Key, SF*>::iterator it = ESFmap.begin(); it != ESFmap.end(); ++it)
360 Key EndgameFunctions::buildKey(const string& keyCode) {
362 assert(keyCode.length() > 0 && keyCode[0] == 'K');
363 assert(keyCode.length() < 8);
368 // Build up a fen substring with the given pieces, note
369 // that the fen string could be of an illegal position.
370 for (size_t i = 0; i < keyCode.length(); i++)
372 if (keyCode[i] == 'K')
375 s << char(upcase? toupper(keyCode[i]) : tolower(keyCode[i]));
377 s << 8 - keyCode.length() << "/8/8/8/8/8/8/8 w -";
378 return Position(s.str()).get_material_key();
381 const string EndgameFunctions::swapColors(const string& keyCode) {
383 // Build corresponding key for the opposite color: "KBPKN" -> "KNKBP"
384 size_t idx = keyCode.find("K", 1);
385 return keyCode.substr(idx) + keyCode.substr(0, idx);
389 void EndgameFunctions::add(const string& keyCode) {
391 typedef typename T::Base F;
393 map<F>().insert(std::pair<Key, F*>(buildKey(keyCode), new T(WHITE)));
394 map<F>().insert(std::pair<Key, F*>(buildKey(swapColors(keyCode)), new T(BLACK)));
398 T* EndgameFunctions::get(Key key) const {
400 typename std::map<Key, T*>::const_iterator it(map<T>().find(key));
401 return (it != map<T>().end() ? it->second : NULL);