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/>.
35 //// Local definitions
40 // Values modified by Joona Kiiski
41 const Value MidgameLimit = Value(15581);
42 const Value EndgameLimit = Value(3998);
44 // Polynomial material balance parameters
45 const Value RedundantQueenPenalty = Value(320);
46 const Value RedundantRookPenalty = Value(554);
48 const int LinearCoefficients[6] = { 1617, -162, -1172, -190, 105, 26 };
50 const int QuadraticCoefficientsSameColor[][8] = {
51 { 7, 7, 7, 7, 7, 7 }, { 39, 2, 7, 7, 7, 7 }, { 35, 271, -4, 7, 7, 7 },
52 { 7, 25, 4, 7, 7, 7 }, { -27, -2, 46, 100, 56, 7 }, { 58, 29, 83, 148, -3, -25 } };
54 const int QuadraticCoefficientsOppositeColor[][8] = {
55 { 41, 41, 41, 41, 41, 41 }, { 37, 41, 41, 41, 41, 41 }, { 10, 62, 41, 41, 41, 41 },
56 { 57, 64, 39, 41, 41, 41 }, { 50, 40, 23, -22, 41, 41 }, { 106, 101, 3, 151, 171, 41 } };
58 typedef EndgameEvaluationFunctionBase EF;
59 typedef EndgameScalingFunctionBase SF;
60 typedef map<Key, EF*> EFMap;
61 typedef map<Key, SF*> SFMap;
63 // Endgame evaluation and scaling functions accessed direcly and not through
64 // the function maps because correspond to more then one material hash key.
65 EvaluationFunction<KmmKm> EvaluateKmmKm[] = { EvaluationFunction<KmmKm>(WHITE), EvaluationFunction<KmmKm>(BLACK) };
66 EvaluationFunction<KXK> EvaluateKXK[] = { EvaluationFunction<KXK>(WHITE), EvaluationFunction<KXK>(BLACK) };
67 ScalingFunction<KBPsK> ScaleKBPsK[] = { ScalingFunction<KBPsK>(WHITE), ScalingFunction<KBPsK>(BLACK) };
68 ScalingFunction<KQKRPs> ScaleKQKRPs[] = { ScalingFunction<KQKRPs>(WHITE), ScalingFunction<KQKRPs>(BLACK) };
69 ScalingFunction<KPsK> ScaleKPsK[] = { ScalingFunction<KPsK>(WHITE), ScalingFunction<KPsK>(BLACK) };
70 ScalingFunction<KPKP> ScaleKPKP[] = { ScalingFunction<KPKP>(WHITE), ScalingFunction<KPKP>(BLACK) };
72 // Helper templates used to detect a given material distribution
73 template<Color Us> bool is_KXK(const Position& pos) {
74 const Color Them = (Us == WHITE ? BLACK : WHITE);
75 return pos.non_pawn_material(Them) == VALUE_ZERO
76 && pos.piece_count(Them, PAWN) == 0
77 && pos.non_pawn_material(Us) >= RookValueMidgame;
80 template<Color Us> bool is_KBPsK(const Position& pos) {
81 return pos.non_pawn_material(Us) == BishopValueMidgame
82 && pos.piece_count(Us, BISHOP) == 1
83 && pos.piece_count(Us, PAWN) >= 1;
86 template<Color Us> bool is_KQKRPs(const Position& pos) {
87 const Color Them = (Us == WHITE ? BLACK : WHITE);
88 return pos.piece_count(Us, PAWN) == 0
89 && pos.non_pawn_material(Us) == QueenValueMidgame
90 && pos.piece_count(Us, QUEEN) == 1
91 && pos.piece_count(Them, ROOK) == 1
92 && pos.piece_count(Them, PAWN) >= 1;
101 /// EndgameFunctions class stores endgame evaluation and scaling functions
102 /// in two std::map. Because STL library is not guaranteed to be thread
103 /// safe even for read access, the maps, although with identical content,
104 /// are replicated for each thread. This is faster then using locks.
106 class EndgameFunctions {
110 template<class T> T* get(Key key) const;
113 template<class T> void add(const string& keyCode);
115 static Key buildKey(const string& keyCode);
116 static const string swapColors(const string& keyCode);
118 // Here we store two maps, for evaluate and scaling functions...
119 pair<EFMap, SFMap> maps;
121 // ...and here is the accessing template function
122 template<typename T> const map<Key, T*>& get() const;
125 // Explicit specializations of a member function shall be declared in
126 // the namespace of which the class template is a member.
127 template<> const EFMap& EndgameFunctions::get<EF>() const { return maps.first; }
128 template<> const SFMap& EndgameFunctions::get<SF>() const { return maps.second; }
135 /// MaterialInfoTable c'tor and d'tor, called once by each thread
137 MaterialInfoTable::MaterialInfoTable() {
139 entries = new MaterialInfo[MaterialTableSize];
140 funcs = new EndgameFunctions();
142 if (!entries || !funcs)
144 cerr << "Failed to allocate " << MaterialTableSize * sizeof(MaterialInfo)
145 << " bytes for material hash table." << endl;
148 memset(entries, 0, MaterialTableSize * sizeof(MaterialInfo));
151 MaterialInfoTable::~MaterialInfoTable() {
158 /// MaterialInfoTable::game_phase() calculates the phase given the current
159 /// position. Because the phase is strictly a function of the material, it
160 /// is stored in MaterialInfo.
162 Phase MaterialInfoTable::game_phase(const Position& pos) {
164 Value npm = pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK);
166 if (npm >= MidgameLimit)
167 return PHASE_MIDGAME;
169 if (npm <= EndgameLimit)
170 return PHASE_ENDGAME;
172 return Phase(((npm - EndgameLimit) * 128) / (MidgameLimit - EndgameLimit));
175 /// MaterialInfoTable::get_material_info() takes a position object as input,
176 /// computes or looks up a MaterialInfo object, and returns a pointer to it.
177 /// If the material configuration is not already present in the table, it
178 /// is stored there, so we don't have to recompute everything when the
179 /// same material configuration occurs again.
181 MaterialInfo* MaterialInfoTable::get_material_info(const Position& pos) {
183 Key key = pos.get_material_key();
184 unsigned index = unsigned(key & (MaterialTableSize - 1));
185 MaterialInfo* mi = entries + index;
187 // If mi->key matches the position's material hash key, it means that we
188 // have analysed this material configuration before, and we can simply
189 // return the information we found the last time instead of recomputing it.
193 // Clear the MaterialInfo object, and set its key
194 memset(mi, 0, sizeof(MaterialInfo));
195 mi->factor[WHITE] = mi->factor[BLACK] = uint8_t(SCALE_FACTOR_NORMAL);
199 mi->gamePhase = MaterialInfoTable::game_phase(pos);
201 // Let's look if we have a specialized evaluation function for this
202 // particular material configuration. First we look for a fixed
203 // configuration one, then a generic one if previous search failed.
204 if ((mi->evaluationFunction = funcs->get<EF>(key)) != NULL)
207 if (is_KXK<WHITE>(pos) || is_KXK<BLACK>(pos))
209 mi->evaluationFunction = is_KXK<WHITE>(pos) ? &EvaluateKXK[WHITE] : &EvaluateKXK[BLACK];
213 if ( pos.pieces(PAWN) == EmptyBoardBB
214 && pos.pieces(ROOK) == EmptyBoardBB
215 && pos.pieces(QUEEN) == EmptyBoardBB)
217 // Minor piece endgame with at least one minor piece per side and
218 // no pawns. Note that the case KmmK is already handled by KXK.
219 assert((pos.pieces(KNIGHT, WHITE) | pos.pieces(BISHOP, WHITE)));
220 assert((pos.pieces(KNIGHT, BLACK) | pos.pieces(BISHOP, BLACK)));
222 if ( pos.piece_count(WHITE, BISHOP) + pos.piece_count(WHITE, KNIGHT) <= 2
223 && pos.piece_count(BLACK, BISHOP) + pos.piece_count(BLACK, KNIGHT) <= 2)
225 mi->evaluationFunction = &EvaluateKmmKm[WHITE];
230 // OK, we didn't find any special evaluation function for the current
231 // material configuration. Is there a suitable scaling function?
233 // We face problems when there are several conflicting applicable
234 // scaling functions and we need to decide which one to use.
237 if ((sf = funcs->get<SF>(key)) != NULL)
239 mi->scalingFunction[sf->color()] = sf;
243 // Generic scaling functions that refer to more then one material
244 // distribution. Should be probed after the specialized ones.
245 // Note that these ones don't return after setting the function.
246 if (is_KBPsK<WHITE>(pos))
247 mi->scalingFunction[WHITE] = &ScaleKBPsK[WHITE];
249 if (is_KBPsK<BLACK>(pos))
250 mi->scalingFunction[BLACK] = &ScaleKBPsK[BLACK];
252 if (is_KQKRPs<WHITE>(pos))
253 mi->scalingFunction[WHITE] = &ScaleKQKRPs[WHITE];
255 else if (is_KQKRPs<BLACK>(pos))
256 mi->scalingFunction[BLACK] = &ScaleKQKRPs[BLACK];
258 if (pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK) == VALUE_ZERO)
260 if (pos.piece_count(BLACK, PAWN) == 0)
262 assert(pos.piece_count(WHITE, PAWN) >= 2);
263 mi->scalingFunction[WHITE] = &ScaleKPsK[WHITE];
265 else if (pos.piece_count(WHITE, PAWN) == 0)
267 assert(pos.piece_count(BLACK, PAWN) >= 2);
268 mi->scalingFunction[BLACK] = &ScaleKPsK[BLACK];
270 else if (pos.piece_count(WHITE, PAWN) == 1 && pos.piece_count(BLACK, PAWN) == 1)
272 // This is a special case because we set scaling functions
273 // for both colors instead of only one.
274 mi->scalingFunction[WHITE] = &ScaleKPKP[WHITE];
275 mi->scalingFunction[BLACK] = &ScaleKPKP[BLACK];
279 // Compute the space weight
280 if (pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK) >=
281 2*QueenValueMidgame + 4*RookValueMidgame + 2*KnightValueMidgame)
283 int minorPieceCount = pos.piece_count(WHITE, KNIGHT)
284 + pos.piece_count(BLACK, KNIGHT)
285 + pos.piece_count(WHITE, BISHOP)
286 + pos.piece_count(BLACK, BISHOP);
288 mi->spaceWeight = minorPieceCount * minorPieceCount;
291 // Evaluate the material balance
292 const int pieceCount[2][8] = {
293 { pos.piece_count(WHITE, BISHOP) > 1, pos.piece_count(WHITE, PAWN), pos.piece_count(WHITE, KNIGHT),
294 pos.piece_count(WHITE, BISHOP), pos.piece_count(WHITE, ROOK), pos.piece_count(WHITE, QUEEN) },
295 { pos.piece_count(BLACK, BISHOP) > 1, pos.piece_count(BLACK, PAWN), pos.piece_count(BLACK, KNIGHT),
296 pos.piece_count(BLACK, BISHOP), pos.piece_count(BLACK, ROOK), pos.piece_count(BLACK, QUEEN) } };
299 int sign, pt1, pt2, pc;
300 int v, vv, matValue = 0;
302 for (c = WHITE, sign = 1; c <= BLACK; c++, sign = -sign)
304 // No pawns makes it difficult to win, even with a material advantage
305 if ( pos.piece_count(c, PAWN) == 0
306 && pos.non_pawn_material(c) - pos.non_pawn_material(opposite_color(c)) <= BishopValueMidgame)
308 if ( pos.non_pawn_material(c) == pos.non_pawn_material(opposite_color(c))
309 || pos.non_pawn_material(c) < RookValueMidgame)
313 switch (pos.piece_count(c, BISHOP)) {
327 // Redundancy of major pieces, formula based on Kaufman's paper
328 // "The Evaluation of Material Imbalances in Chess"
329 // http://mywebpages.comcast.net/danheisman/Articles/evaluation_of_material_imbalance.htm
330 if (pieceCount[c][ROOK] >= 1)
331 matValue -= sign * ((pieceCount[c][ROOK] - 1) * RedundantRookPenalty + pieceCount[c][QUEEN] * RedundantQueenPenalty);
333 them = opposite_color(c);
336 // Second-degree polynomial material imbalance by Tord Romstad
338 // We use PIECE_TYPE_NONE as a place holder for the bishop pair "extended piece",
339 // this allow us to be more flexible in defining bishop pair bonuses.
340 for (pt1 = PIECE_TYPE_NONE; pt1 <= QUEEN; pt1++)
342 pc = pieceCount[c][pt1];
346 vv = LinearCoefficients[pt1];
348 for (pt2 = PIECE_TYPE_NONE; pt2 <= pt1; pt2++)
349 vv += pieceCount[c][pt2] * QuadraticCoefficientsSameColor[pt1][pt2]
350 + pieceCount[them][pt2] * QuadraticCoefficientsOppositeColor[pt1][pt2];
354 matValue += sign * v;
356 mi->value = int16_t(matValue / 16);
361 /// EndgameFunctions member definitions
363 EndgameFunctions::EndgameFunctions() {
365 add<EvaluationFunction<KNNK> >("KNNK");
366 add<EvaluationFunction<KPK> >("KPK");
367 add<EvaluationFunction<KBNK> >("KBNK");
368 add<EvaluationFunction<KRKP> >("KRKP");
369 add<EvaluationFunction<KRKB> >("KRKB");
370 add<EvaluationFunction<KRKN> >("KRKN");
371 add<EvaluationFunction<KQKR> >("KQKR");
372 add<EvaluationFunction<KBBKN> >("KBBKN");
374 add<ScalingFunction<KNPK> >("KNPK");
375 add<ScalingFunction<KRPKR> >("KRPKR");
376 add<ScalingFunction<KBPKB> >("KBPKB");
377 add<ScalingFunction<KBPPKB> >("KBPPKB");
378 add<ScalingFunction<KBPKN> >("KBPKN");
379 add<ScalingFunction<KRPPKRP> >("KRPPKRP");
382 EndgameFunctions::~EndgameFunctions() {
384 for (EFMap::const_iterator it = maps.first.begin(); it != maps.first.end(); ++it)
387 for (SFMap::const_iterator it = maps.second.begin(); it != maps.second.end(); ++it)
391 Key EndgameFunctions::buildKey(const string& keyCode) {
393 assert(keyCode.length() > 0 && keyCode.length() < 8);
394 assert(keyCode[0] == 'K');
399 // Build up a fen string with the given pieces, note that
400 // the fen string could be of an illegal position.
401 for (size_t i = 0; i < keyCode.length(); i++)
403 if (keyCode[i] == 'K')
406 fen += char(upcase ? toupper(keyCode[i]) : tolower(keyCode[i]));
408 fen += char(8 - keyCode.length() + '0');
409 fen += "/8/8/8/8/8/8/8 w - -";
410 return Position(fen, 0).get_material_key();
413 const string EndgameFunctions::swapColors(const string& keyCode) {
415 // Build corresponding key for the opposite color: "KBPKN" -> "KNKBP"
416 size_t idx = keyCode.find('K', 1);
417 return keyCode.substr(idx) + keyCode.substr(0, idx);
421 void EndgameFunctions::add(const string& keyCode) {
423 typedef typename T::Base F;
424 typedef map<Key, F*> M;
426 const_cast<M&>(get<F>()).insert(pair<Key, F*>(buildKey(keyCode), new T(WHITE)));
427 const_cast<M&>(get<F>()).insert(pair<Key, F*>(buildKey(swapColors(keyCode)), new T(BLACK)));
431 T* EndgameFunctions::get(Key key) const {
433 typename map<Key, T*>::const_iterator it = get<T>().find(key);
434 return it != get<T>().end() ? it->second : NULL;