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/>.
35 //// Local definitions
40 // Values modified by Joona Kiiski
41 const Value BishopPairMidgameBonus = Value(109);
42 const Value BishopPairEndgameBonus = Value(97);
44 Key KNNKMaterialKey, KKNNMaterialKey;
53 /// See header for a class description. It is declared here to avoid
54 /// to include <map> in the header file.
56 class EndgameFunctions {
60 EndgameEvaluationFunctionBase* getEEF(Key key) const;
61 EndgameScalingFunctionBase* getESF(Key key, Color* c) const;
64 void add(const string& keyCode, EndgameEvaluationFunctionBase* f);
65 void add(const string& keyCode, Color c, EndgameScalingFunctionBase* f);
66 Key buildKey(const string& keyCode);
71 EndgameScalingFunctionBase* fun;
74 std::map<Key, EndgameEvaluationFunctionBase*> EEFmap;
75 std::map<Key, ScalingInfo> ESFmap;
84 /// Constructor for the MaterialInfoTable class
86 MaterialInfoTable::MaterialInfoTable(unsigned int numOfEntries) {
89 entries = new MaterialInfo[size];
90 funcs = new EndgameFunctions();
91 if (!entries || !funcs)
93 std::cerr << "Failed to allocate " << (numOfEntries * sizeof(MaterialInfo))
94 << " bytes for material hash table." << std::endl;
95 Application::exit_with_failure();
101 /// Destructor for the MaterialInfoTable class
103 MaterialInfoTable::~MaterialInfoTable() {
110 /// MaterialInfoTable::clear() clears a material hash table by setting
111 /// all entries to 0.
113 void MaterialInfoTable::clear() {
115 memset(entries, 0, size * sizeof(MaterialInfo));
119 /// MaterialInfoTable::get_material_info() takes a position object as input,
120 /// computes or looks up a MaterialInfo object, and returns a pointer to it.
121 /// If the material configuration is not already present in the table, it
122 /// is stored there, so we don't have to recompute everything when the
123 /// same material configuration occurs again.
125 MaterialInfo* MaterialInfoTable::get_material_info(const Position& pos) {
127 Key key = pos.get_material_key();
128 int index = key & (size - 1);
129 MaterialInfo* mi = entries + index;
131 // If mi->key matches the position's material hash key, it means that we
132 // have analysed this material configuration before, and we can simply
133 // return the information we found the last time instead of recomputing it.
137 // Clear the MaterialInfo object, and set its key
141 // A special case before looking for a specialized evaluation function
142 // KNN vs K is a draw.
143 if (key == KNNKMaterialKey || key == KKNNMaterialKey)
145 mi->factor[WHITE] = mi->factor[BLACK] = 0;
149 // Let's look if we have a specialized evaluation function for this
150 // particular material configuration. First we look for a fixed
151 // configuration one, then a generic one if previous search failed.
152 if ((mi->evaluationFunction = funcs->getEEF(key)) != NULL)
155 else if ( pos.non_pawn_material(BLACK) == Value(0)
156 && pos.piece_count(BLACK, PAWN) == 0
157 && pos.non_pawn_material(WHITE) >= RookValueEndgame)
159 mi->evaluationFunction = &EvaluateKXK;
162 else if ( pos.non_pawn_material(WHITE) == Value(0)
163 && pos.piece_count(WHITE, PAWN) == 0
164 && pos.non_pawn_material(BLACK) >= RookValueEndgame)
166 mi->evaluationFunction = &EvaluateKKX;
169 else if ( pos.pawns() == EmptyBoardBB
170 && pos.rooks() == EmptyBoardBB
171 && pos.queens() == EmptyBoardBB)
173 // Minor piece endgame with at least one minor piece per side,
175 assert(pos.knights(WHITE) | pos.bishops(WHITE));
176 assert(pos.knights(BLACK) | pos.bishops(BLACK));
178 if ( pos.piece_count(WHITE, BISHOP) + pos.piece_count(WHITE, KNIGHT) <= 2
179 && pos.piece_count(BLACK, BISHOP) + pos.piece_count(BLACK, KNIGHT) <= 2)
181 mi->evaluationFunction = &EvaluateKmmKm;
186 // OK, we didn't find any special evaluation function for the current
187 // material configuration. Is there a suitable scaling function?
189 // The code below is rather messy, and it could easily get worse later,
190 // if we decide to add more special cases. We face problems when there
191 // are several conflicting applicable scaling functions and we need to
192 // decide which one to use.
194 EndgameScalingFunctionBase* sf;
196 if ((sf = funcs->getESF(key, &c)) != NULL)
198 mi->scalingFunction[c] = sf;
202 if ( pos.non_pawn_material(WHITE) == BishopValueMidgame
203 && pos.piece_count(WHITE, BISHOP) == 1
204 && pos.piece_count(WHITE, PAWN) >= 1)
205 mi->scalingFunction[WHITE] = &ScaleKBPK;
207 if ( pos.non_pawn_material(BLACK) == BishopValueMidgame
208 && pos.piece_count(BLACK, BISHOP) == 1
209 && pos.piece_count(BLACK, PAWN) >= 1)
210 mi->scalingFunction[BLACK] = &ScaleKKBP;
212 if ( pos.piece_count(WHITE, PAWN) == 0
213 && pos.non_pawn_material(WHITE) == QueenValueMidgame
214 && pos.piece_count(WHITE, QUEEN) == 1
215 && pos.piece_count(BLACK, ROOK) == 1
216 && pos.piece_count(BLACK, PAWN) >= 1)
217 mi->scalingFunction[WHITE] = &ScaleKQKRP;
219 else if ( pos.piece_count(BLACK, PAWN) == 0
220 && pos.non_pawn_material(BLACK) == QueenValueMidgame
221 && pos.piece_count(BLACK, QUEEN) == 1
222 && pos.piece_count(WHITE, ROOK) == 1
223 && pos.piece_count(WHITE, PAWN) >= 1)
224 mi->scalingFunction[BLACK] = &ScaleKRPKQ;
226 if (pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK) == Value(0))
228 if (pos.piece_count(BLACK, PAWN) == 0)
230 assert(pos.piece_count(WHITE, PAWN) >= 2);
231 mi->scalingFunction[WHITE] = &ScaleKPsK;
233 else if (pos.piece_count(WHITE, PAWN) == 0)
235 assert(pos.piece_count(BLACK, PAWN) >= 2);
236 mi->scalingFunction[BLACK] = &ScaleKKPs;
238 else if (pos.piece_count(WHITE, PAWN) == 1 && pos.piece_count(BLACK, PAWN) == 1)
240 mi->scalingFunction[WHITE] = &ScaleKPKPw;
241 mi->scalingFunction[BLACK] = &ScaleKPKPb;
245 // Compute the space weight
246 if (pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK) >=
247 2*QueenValueMidgame + 4*RookValueMidgame + 2*KnightValueMidgame)
249 int minorPieceCount = pos.piece_count(WHITE, KNIGHT)
250 + pos.piece_count(BLACK, KNIGHT)
251 + pos.piece_count(WHITE, BISHOP)
252 + pos.piece_count(BLACK, BISHOP);
254 mi->spaceWeight = minorPieceCount * minorPieceCount;
257 // Evaluate the material balance
260 Value egValue = Value(0);
261 Value mgValue = Value(0);
263 for (c = WHITE, sign = 1; c <= BLACK; c++, sign = -sign)
265 // No pawns makes it difficult to win, even with a material advantage
266 if ( pos.piece_count(c, PAWN) == 0
267 && pos.non_pawn_material(c) - pos.non_pawn_material(opposite_color(c)) <= BishopValueMidgame)
269 if ( pos.non_pawn_material(c) == pos.non_pawn_material(opposite_color(c))
270 || pos.non_pawn_material(c) < RookValueMidgame)
274 switch (pos.piece_count(c, BISHOP)) {
289 if (pos.piece_count(c, BISHOP) >= 2)
291 mgValue += sign * BishopPairMidgameBonus;
292 egValue += sign * BishopPairEndgameBonus;
295 // Knights are stronger when there are many pawns on the board. The
296 // formula is taken from Larry Kaufman's paper "The Evaluation of Material
297 // Imbalances in Chess":
298 // http://mywebpages.comcast.net/danheisman/Articles/evaluation_of_material_imbalance.htm
299 mgValue += sign * Value(pos.piece_count(c, KNIGHT)*(pos.piece_count(c, PAWN)-5)*16);
300 egValue += sign * Value(pos.piece_count(c, KNIGHT)*(pos.piece_count(c, PAWN)-5)*16);
302 // Redundancy of major pieces, again based on Kaufman's paper:
303 if (pos.piece_count(c, ROOK) >= 1)
305 Value v = Value((pos.piece_count(c, ROOK) - 1) * 32 + pos.piece_count(c, QUEEN) * 16);
310 mi->mgValue = int16_t(mgValue);
311 mi->egValue = int16_t(egValue);
316 /// EndgameFunctions member definitions. This class is used to store the maps
317 /// of end game and scaling functions that MaterialInfoTable will query for
318 /// each key. The maps are constant and are populated only at construction,
319 /// but are per-thread instead of globals to avoid expensive locks.
321 EndgameFunctions::EndgameFunctions() {
323 KNNKMaterialKey = buildKey("KNNK");
324 KKNNMaterialKey = buildKey("KKNN");
326 add("KPK", &EvaluateKPK);
327 add("KKP", &EvaluateKKP);
328 add("KBNK", &EvaluateKBNK);
329 add("KKBN", &EvaluateKKBN);
330 add("KRKP", &EvaluateKRKP);
331 add("KPKR", &EvaluateKPKR);
332 add("KRKB", &EvaluateKRKB);
333 add("KBKR", &EvaluateKBKR);
334 add("KRKN", &EvaluateKRKN);
335 add("KNKR", &EvaluateKNKR);
336 add("KQKR", &EvaluateKQKR);
337 add("KRKQ", &EvaluateKRKQ);
338 add("KBBKN", &EvaluateKBBKN);
339 add("KNKBB", &EvaluateKNKBB);
341 add("KNPK", WHITE, &ScaleKNPK);
342 add("KKNP", BLACK, &ScaleKKNP);
343 add("KRPKR", WHITE, &ScaleKRPKR);
344 add("KRKRP", BLACK, &ScaleKRKRP);
345 add("KBPKB", WHITE, &ScaleKBPKB);
346 add("KBKBP", BLACK, &ScaleKBKBP);
347 add("KBPPKB", WHITE, &ScaleKBPPKB);
348 add("KBKBPP", BLACK, &ScaleKBKBPP);
349 add("KBPKN", WHITE, &ScaleKBPKN);
350 add("KNKBP", BLACK, &ScaleKNKBP);
351 add("KRPPKRP", WHITE, &ScaleKRPPKRP);
352 add("KRPKRPP", BLACK, &ScaleKRPKRPP);
353 add("KRPPKRP", WHITE, &ScaleKRPPKRP);
354 add("KRPKRPP", BLACK, &ScaleKRPKRPP);
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 void EndgameFunctions::add(const string& keyCode, EndgameEvaluationFunctionBase* f) {
380 EEFmap.insert(std::pair<Key, EndgameEvaluationFunctionBase*>(buildKey(keyCode), f));
383 void EndgameFunctions::add(const string& keyCode, Color c, EndgameScalingFunctionBase* f) {
385 ScalingInfo s = {c, f};
386 ESFmap.insert(std::pair<Key, ScalingInfo>(buildKey(keyCode), s));
389 EndgameEvaluationFunctionBase* EndgameFunctions::getEEF(Key key) const {
391 std::map<Key, EndgameEvaluationFunctionBase*>::const_iterator it(EEFmap.find(key));
392 return (it != EEFmap.end() ? it->second : NULL);
395 EndgameScalingFunctionBase* EndgameFunctions::getESF(Key key, Color* c) const {
397 std::map<Key, ScalingInfo>::const_iterator it(ESFmap.find(key));
398 if (it == ESFmap.end())
402 return it->second.fun;