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 EF* getEEF(Key key) const;
73 SF* getESF(Key key, Color* c) const;
76 Key buildKey(const string& keyCode);
77 const string swapColors(const string& keyCode);
78 template<EndgameType> void add_ef(const string& keyCode);
79 template<EndgameType> void add_sf(const string& keyCode);
87 std::map<Key, EF*> EEFmap;
88 std::map<Key, ScalingInfo> ESFmap;
97 /// Constructor for the MaterialInfoTable class
99 MaterialInfoTable::MaterialInfoTable(unsigned int numOfEntries) {
102 entries = new MaterialInfo[size];
103 funcs = new EndgameFunctions();
104 if (!entries || !funcs)
106 std::cerr << "Failed to allocate " << (numOfEntries * sizeof(MaterialInfo))
107 << " bytes for material hash table." << std::endl;
108 Application::exit_with_failure();
113 /// Destructor for the MaterialInfoTable class
115 MaterialInfoTable::~MaterialInfoTable() {
122 /// MaterialInfoTable::get_material_info() takes a position object as input,
123 /// computes or looks up a MaterialInfo object, and returns a pointer to it.
124 /// If the material configuration is not already present in the table, it
125 /// is stored there, so we don't have to recompute everything when the
126 /// same material configuration occurs again.
128 MaterialInfo* MaterialInfoTable::get_material_info(const Position& pos) {
130 Key key = pos.get_material_key();
131 int index = key & (size - 1);
132 MaterialInfo* mi = entries + index;
134 // If mi->key matches the position's material hash key, it means that we
135 // have analysed this material configuration before, and we can simply
136 // return the information we found the last time instead of recomputing it.
140 // Clear the MaterialInfo object, and set its key
144 // A special case before looking for a specialized evaluation function
145 // KNN vs K is a draw.
146 if (key == KNNKMaterialKey || key == KKNNMaterialKey)
148 mi->factor[WHITE] = mi->factor[BLACK] = 0;
152 // Let's look if we have a specialized evaluation function for this
153 // particular material configuration. First we look for a fixed
154 // configuration one, then a generic one if previous search failed.
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) >= RookValueMidgame)
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) >= RookValueMidgame)
169 mi->evaluationFunction = &EvaluateKKX;
172 else if ( pos.pawns() == EmptyBoardBB
173 && pos.rooks() == EmptyBoardBB
174 && pos.queens() == EmptyBoardBB)
176 // Minor piece endgame with at least one minor piece per side,
178 assert(pos.knights(WHITE) | pos.bishops(WHITE));
179 assert(pos.knights(BLACK) | pos.bishops(BLACK));
181 if ( pos.piece_count(WHITE, BISHOP) + pos.piece_count(WHITE, KNIGHT) <= 2
182 && pos.piece_count(BLACK, BISHOP) + pos.piece_count(BLACK, KNIGHT) <= 2)
184 mi->evaluationFunction = &EvaluateKmmKm;
189 // OK, we didn't find any special evaluation function for the current
190 // material configuration. Is there a suitable scaling function?
192 // The code below is rather messy, and it could easily get worse later,
193 // if we decide to add more special cases. We face problems when there
194 // are several conflicting applicable scaling functions and we need to
195 // decide which one to use.
197 EndgameScalingFunctionBase* sf;
199 if ((sf = funcs->getESF(key, &c)) != NULL)
201 mi->scalingFunction[c] = sf;
205 if ( pos.non_pawn_material(WHITE) == BishopValueMidgame
206 && pos.piece_count(WHITE, BISHOP) == 1
207 && pos.piece_count(WHITE, PAWN) >= 1)
208 mi->scalingFunction[WHITE] = &ScaleKBPK;
210 if ( pos.non_pawn_material(BLACK) == BishopValueMidgame
211 && pos.piece_count(BLACK, BISHOP) == 1
212 && pos.piece_count(BLACK, PAWN) >= 1)
213 mi->scalingFunction[BLACK] = &ScaleKKBP;
215 if ( pos.piece_count(WHITE, PAWN) == 0
216 && pos.non_pawn_material(WHITE) == QueenValueMidgame
217 && pos.piece_count(WHITE, QUEEN) == 1
218 && pos.piece_count(BLACK, ROOK) == 1
219 && pos.piece_count(BLACK, PAWN) >= 1)
220 mi->scalingFunction[WHITE] = &ScaleKQKRP;
222 else if ( pos.piece_count(BLACK, PAWN) == 0
223 && pos.non_pawn_material(BLACK) == QueenValueMidgame
224 && pos.piece_count(BLACK, QUEEN) == 1
225 && pos.piece_count(WHITE, ROOK) == 1
226 && pos.piece_count(WHITE, PAWN) >= 1)
227 mi->scalingFunction[BLACK] = &ScaleKRPKQ;
229 if (pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK) == Value(0))
231 if (pos.piece_count(BLACK, PAWN) == 0)
233 assert(pos.piece_count(WHITE, PAWN) >= 2);
234 mi->scalingFunction[WHITE] = &ScaleKPsK;
236 else if (pos.piece_count(WHITE, PAWN) == 0)
238 assert(pos.piece_count(BLACK, PAWN) >= 2);
239 mi->scalingFunction[BLACK] = &ScaleKKPs;
241 else if (pos.piece_count(WHITE, PAWN) == 1 && pos.piece_count(BLACK, PAWN) == 1)
243 mi->scalingFunction[WHITE] = &ScaleKPKPw;
244 mi->scalingFunction[BLACK] = &ScaleKPKPb;
248 // Compute the space weight
249 if (pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK) >=
250 2*QueenValueMidgame + 4*RookValueMidgame + 2*KnightValueMidgame)
252 int minorPieceCount = pos.piece_count(WHITE, KNIGHT)
253 + pos.piece_count(BLACK, KNIGHT)
254 + pos.piece_count(WHITE, BISHOP)
255 + pos.piece_count(BLACK, BISHOP);
257 mi->spaceWeight = minorPieceCount * minorPieceCount;
260 // Evaluate the material balance
263 Value egValue = Value(0);
264 Value mgValue = Value(0);
266 for (c = WHITE, sign = 1; c <= BLACK; c++, sign = -sign)
268 // No pawns makes it difficult to win, even with a material advantage
269 if ( pos.piece_count(c, PAWN) == 0
270 && pos.non_pawn_material(c) - pos.non_pawn_material(opposite_color(c)) <= BishopValueMidgame)
272 if ( pos.non_pawn_material(c) == pos.non_pawn_material(opposite_color(c))
273 || pos.non_pawn_material(c) < RookValueMidgame)
277 switch (pos.piece_count(c, BISHOP)) {
292 if (pos.piece_count(c, BISHOP) >= 2)
294 mgValue += sign * BishopPairMidgameBonus;
295 egValue += sign * BishopPairEndgameBonus;
298 // Knights are stronger when there are many pawns on the board. The
299 // formula is taken from Larry Kaufman's paper "The Evaluation of Material
300 // Imbalances in Chess":
301 // http://mywebpages.comcast.net/danheisman/Articles/evaluation_of_material_imbalance.htm
302 mgValue += sign * Value(pos.piece_count(c, KNIGHT)*(pos.piece_count(c, PAWN)-5)*16);
303 egValue += sign * Value(pos.piece_count(c, KNIGHT)*(pos.piece_count(c, PAWN)-5)*16);
305 // Redundancy of major pieces, again based on Kaufman's paper:
306 if (pos.piece_count(c, ROOK) >= 1)
308 Value v = Value((pos.piece_count(c, ROOK) - 1) * 32 + pos.piece_count(c, QUEEN) * 16);
313 mi->mgValue = int16_t(mgValue);
314 mi->egValue = int16_t(egValue);
319 /// EndgameFunctions member definitions. This class is used to store the maps
320 /// of end game and scaling functions that MaterialInfoTable will query for
321 /// each key. The maps are constant and are populated only at construction,
322 /// but are per-thread instead of globals to avoid expensive locks needed
323 /// because std::map is not guaranteed to be thread-safe even if accessed
324 /// only for a lookup.
326 EndgameFunctions::EndgameFunctions() {
328 KNNKMaterialKey = buildKey("KNNK");
329 KKNNMaterialKey = buildKey("KKNN");
332 add_ef<KBNK>("KBNK");
333 add_ef<KRKP>("KRKP");
334 add_ef<KRKB>("KRKB");
335 add_ef<KRKN>("KRKN");
336 add_ef<KQKR>("KQKR");
337 add_ef<KBBKN>("KBBKN");
339 add_sf<KNPK>("KNPK");
340 add_sf<KRPKR>("KRPKR");
341 add_sf<KBPKB>("KBPKB");
342 add_sf<KBPPKB>("KBPPKB");
343 add_sf<KBPKN>("KBPKN");
344 add_sf<KRPPKRP>("KRPPKRP");
345 add_sf<KRPPKRP>("KRPPKRP");
348 EndgameFunctions::~EndgameFunctions() {
350 for (std::map<Key, EF*>::iterator it = EEFmap.begin(); it != EEFmap.end(); ++it)
353 for (std::map<Key, ScalingInfo>::iterator it = ESFmap.begin(); it != ESFmap.end(); ++it)
354 delete (*it).second.fun;
357 Key EndgameFunctions::buildKey(const string& keyCode) {
359 assert(keyCode.length() > 0 && keyCode[0] == 'K');
360 assert(keyCode.length() < 8);
365 // Build up a fen substring with the given pieces, note
366 // that the fen string could be of an illegal position.
367 for (size_t i = 0; i < keyCode.length(); i++)
369 if (keyCode[i] == 'K')
372 s << char(upcase? toupper(keyCode[i]) : tolower(keyCode[i]));
374 s << 8 - keyCode.length() << "/8/8/8/8/8/8/8 w -";
375 return Position(s.str()).get_material_key();
378 const string EndgameFunctions::swapColors(const string& keyCode) {
380 // Build corresponding key for the opposite color: "KBPKN" -> "KNKBP"
381 size_t idx = keyCode.find("K", 1);
382 return keyCode.substr(idx) + keyCode.substr(0, idx);
385 template<EndgameType et>
386 void EndgameFunctions::add_ef(const string& keyCode) {
388 EEFmap.insert(std::pair<Key, EF*>(buildKey(keyCode), new EvaluationFunction<et>(WHITE)));
389 EEFmap.insert(std::pair<Key, EF*>(buildKey(swapColors(keyCode)), new EvaluationFunction<et>(BLACK)));
392 template<EndgameType et>
393 void EndgameFunctions::add_sf(const string& keyCode) {
395 ScalingInfo s1 = {WHITE, new ScalingFunction<et>(WHITE)};
396 ScalingInfo s2 = {BLACK, new ScalingFunction<et>(BLACK)};
398 ESFmap.insert(std::pair<Key, ScalingInfo>(buildKey(keyCode), s1));
399 ESFmap.insert(std::pair<Key, ScalingInfo>(buildKey(swapColors(keyCode)), s2));
402 EndgameEvaluationFunctionBase* EndgameFunctions::getEEF(Key key) const {
404 std::map<Key, EF*>::const_iterator it(EEFmap.find(key));
405 return (it != EEFmap.end() ? it->second : NULL);
408 EndgameScalingFunctionBase* EndgameFunctions::getESF(Key key, Color* c) const {
410 std::map<Key, ScalingInfo>::const_iterator it(ESFmap.find(key));
411 if (it == ESFmap.end())
415 return it->second.fun;