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 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/>.
33 #include "ucioption.h"
37 //// Local definitions
42 const int Sign[2] = {1, -1};
44 // Evaluation grain size, must be a power of 2.
45 const int GrainSize = 4;
48 int WeightMobilityMidgame = 0x100;
49 int WeightMobilityEndgame = 0x100;
50 int WeightPawnStructureMidgame = 0x100;
51 int WeightPawnStructureEndgame = 0x100;
52 int WeightPassedPawnsMidgame = 0x100;
53 int WeightPassedPawnsEndgame = 0x100;
54 int WeightKingSafety[2] = { 0x100, 0x100 };
57 // Internal evaluation weights. These are applied on top of the evaluation
58 // weights read from UCI parameters. The purpose is to be able to change
59 // the evaluation weights while keeping the default values of the UCI
60 // parameters at 100, which looks prettier.
61 const int WeightMobilityMidgameInternal = 0x100;
62 const int WeightMobilityEndgameInternal = 0x100;
63 const int WeightPawnStructureMidgameInternal = 0x100;
64 const int WeightPawnStructureEndgameInternal = 0x100;
65 const int WeightPassedPawnsMidgameInternal = 0x100;
66 const int WeightPassedPawnsEndgameInternal = 0x100;
67 const int WeightKingSafetyInternal = 0x110;
68 const int WeightKingOppSafetyInternal = 0x110;
69 const int WeightSpaceInternal = 0x30;
71 // Visually better to define tables constants
74 // Knight mobility bonus in middle game and endgame, indexed by the number
75 // of attacked squares not occupied by friendly piecess.
76 const Value MidgameKnightMobilityBonus[] = {
78 V(-30), V(-20),V(-10), V(0), V(10), V(20), V(25), V(30), V(30)
81 const Value EndgameKnightMobilityBonus[] = {
83 V(-30), V(-20),V(-10), V(0), V(10), V(20), V(25), V(30), V(30)
86 // Bishop mobility bonus in middle game and endgame, indexed by the number
87 // of attacked squares not occupied by friendly pieces. X-ray attacks through
88 // queens are also included.
89 const Value MidgameBishopMobilityBonus[] = {
91 V(-30), V(-15), V(0), V(15), V(30), V(45), V(58), V(66),
92 // 8 9 10 11 12 13 14 15
93 V( 72), V( 76), V(78), V(80), V(81), V(82), V(83), V(83)
96 const Value EndgameBishopMobilityBonus[] = {
98 V(-30), V(-15), V(0), V(15), V(30), V(45), V(58), V(66),
99 // 8 9 10 11 12 13 14 15
100 V( 72), V( 76), V(78), V(80), V(81), V(82), V(83), V(83)
103 // Rook mobility bonus in middle game and endgame, indexed by the number
104 // of attacked squares not occupied by friendly pieces. X-ray attacks through
105 // queens and rooks are also included.
106 const Value MidgameRookMobilityBonus[] = {
108 V(-18), V(-12), V(-6), V(0), V(6), V(12), V(16), V(21),
109 // 8 9 10 11 12 13 14 15
110 V( 24), V( 27), V(28), V(29), V(30), V(31), V(32), V(33)
113 const Value EndgameRookMobilityBonus[] = {
115 V(-30), V(-18), V(-6), V(6), V(18), V(30), V(42), V(54),
116 // 8 9 10 11 12 13 14 15
117 V( 66), V( 74), V(78), V(80), V(81), V(82), V(83), V(83)
120 // Queen mobility bonus in middle game and endgame, indexed by the number
121 // of attacked squares not occupied by friendly pieces.
122 const Value MidgameQueenMobilityBonus[] = {
124 V(-10), V(-8), V(-6), V(-4), V(-2), V( 0), V( 2), V( 4),
125 // 8 9 10 11 12 13 14 15
126 V( 6), V( 8), V(10), V(12), V(13), V(14), V(15), V(16),
127 // 16 17 18 19 20 21 22 23
128 V( 16), V(16), V(16), V(16), V(16), V(16), V(16), V(16),
129 // 24 25 26 27 28 29 30 31
130 V( 16), V(16), V(16), V(16), V(16), V(16), V(16), V(16)
133 const Value EndgameQueenMobilityBonus[] = {
135 V(-20),V(-15),V(-10), V(-5), V( 0), V( 5), V(10), V(15),
136 // 8 9 10 11 12 13 14 15
137 V( 19), V(23), V(27), V(29), V(30), V(30), V(30), V(30),
138 // 16 17 18 19 20 21 22 23
139 V( 30), V(30), V(30), V(30), V(30), V(30), V(30), V(30),
140 // 24 25 26 27 28 29 30 31
141 V( 30), V(30), V(30), V(30), V(30), V(30), V(30), V(30)
144 // Outpost bonuses for knights and bishops, indexed by square (from white's
146 const Value KnightOutpostBonus[64] = {
148 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 1
149 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 2
150 V(0), V(0), V(5),V(10),V(10), V(5), V(0), V(0), // 3
151 V(0), V(5),V(20),V(30),V(30),V(20), V(5), V(0), // 4
152 V(0),V(10),V(30),V(40),V(40),V(30),V(10), V(0), // 5
153 V(0), V(5),V(20),V(20),V(20),V(20), V(5), V(0), // 6
154 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 7
155 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0) // 8
158 const Value BishopOutpostBonus[64] = {
160 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 1
161 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 2
162 V(0), V(0), V(5), V(5), V(5), V(5), V(0), V(0), // 3
163 V(0), V(5),V(10),V(10),V(10),V(10), V(5), V(0), // 4
164 V(0),V(10),V(20),V(20),V(20),V(20),V(10), V(0), // 5
165 V(0), V(5), V(8), V(8), V(8), V(8), V(5), V(0), // 6
166 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 7
167 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0) // 8
170 // Bonus for unstoppable passed pawns:
171 const Value UnstoppablePawnValue = Value(0x500);
173 // Rooks and queens on the 7th rank:
174 const Value MidgameRookOn7thBonus = Value(50);
175 const Value EndgameRookOn7thBonus = Value(100);
176 const Value MidgameQueenOn7thBonus = Value(25);
177 const Value EndgameQueenOn7thBonus = Value(50);
179 // Rooks on open files:
180 const Value RookOpenFileBonus = Value(40);
181 const Value RookHalfOpenFileBonus = Value(20);
183 // Penalty for rooks trapped inside a friendly king which has lost the
185 const Value TrappedRookPenalty = Value(180);
187 // Penalty for a bishop on a7/h7 (a2/h2 for black) which is trapped by
189 const Value TrappedBishopA7H7Penalty = Value(300);
191 // Bitboard masks for detecting trapped bishops on a7/h7 (a2/h2 for black):
192 const Bitboard MaskA7H7[2] = {
193 ((1ULL << SQ_A7) | (1ULL << SQ_H7)),
194 ((1ULL << SQ_A2) | (1ULL << SQ_H2))
197 // Penalty for a bishop on a1/h1 (a8/h8 for black) which is trapped by
198 // a friendly pawn on b2/g2 (b7/g7 for black). This can obviously only
199 // happen in Chess960 games.
200 const Value TrappedBishopA1H1Penalty = Value(100);
202 // Bitboard masks for detecting trapped bishops on a1/h1 (a8/h8 for black):
203 const Bitboard MaskA1H1[2] = {
204 ((1ULL << SQ_A1) | (1ULL << SQ_H1)),
205 ((1ULL << SQ_A8) | (1ULL << SQ_H8))
208 // The SpaceMask[color] contains area of the board which is consdered by
209 // the space evaluation. In the middle game, each side is given a bonus
210 // based on how many squares inside this area are safe and available for
211 // friendly minor pieces.
212 const Bitboard SpaceMask[2] = {
213 (1ULL<<SQ_C2) | (1ULL<<SQ_D2) | (1ULL<<SQ_E2) | (1ULL<<SQ_F2) |
214 (1ULL<<SQ_C3) | (1ULL<<SQ_D3) | (1ULL<<SQ_E3) | (1ULL<<SQ_F3) |
215 (1ULL<<SQ_C4) | (1ULL<<SQ_D4) | (1ULL<<SQ_E4) | (1ULL<<SQ_F4),
216 (1ULL<<SQ_C7) | (1ULL<<SQ_D7) | (1ULL<<SQ_E7) | (1ULL<<SQ_F7) |
217 (1ULL<<SQ_C6) | (1ULL<<SQ_D6) | (1ULL<<SQ_E6) | (1ULL<<SQ_F6) |
218 (1ULL<<SQ_C5) | (1ULL<<SQ_D5) | (1ULL<<SQ_E5) | (1ULL<<SQ_F5)
221 /// King safety constants and variables. The king safety scores are taken
222 /// from the array SafetyTable[]. Various little "meta-bonuses" measuring
223 /// the strength of the attack are added up into an integer, which is used
224 /// as an index to SafetyTable[].
226 // Attack weights for each piece type.
227 const int QueenAttackWeight = 5;
228 const int RookAttackWeight = 3;
229 const int BishopAttackWeight = 2;
230 const int KnightAttackWeight = 2;
232 // Bonuses for safe checks for each piece type.
233 int QueenContactCheckBonus = 3;
234 int QueenCheckBonus = 2;
235 int RookCheckBonus = 1;
236 int BishopCheckBonus = 1;
237 int KnightCheckBonus = 1;
238 int DiscoveredCheckBonus = 3;
240 // Scan for queen contact mates?
241 const bool QueenContactMates = true;
243 // Bonus for having a mate threat.
244 int MateThreatBonus = 3;
246 // InitKingDanger[] contains bonuses based on the position of the defending
248 const int InitKingDanger[64] = {
249 2, 0, 2, 5, 5, 2, 0, 2,
250 2, 2, 4, 8, 8, 4, 2, 2,
251 7, 10, 12, 12, 12, 12, 10, 7,
252 15, 15, 15, 15, 15, 15, 15, 15,
253 15, 15, 15, 15, 15, 15, 15, 15,
254 15, 15, 15, 15, 15, 15, 15, 15,
255 15, 15, 15, 15, 15, 15, 15, 15,
256 15, 15, 15, 15, 15, 15, 15, 15
259 // SafetyTable[] contains the actual king safety scores. It is initialized
261 Value SafetyTable[100];
263 // Pawn and material hash tables, indexed by the current thread id
264 PawnInfoTable *PawnTable[8] = {0, 0, 0, 0, 0, 0, 0, 0};
265 MaterialInfoTable *MaterialTable[8] = {0, 0, 0, 0, 0, 0, 0, 0};
267 // Sizes of pawn and material hash tables
268 const int PawnTableSize = 16384;
269 const int MaterialTableSize = 1024;
271 // Array which gives the number of nonzero bits in an 8-bit integer:
272 uint8_t BitCount8Bit[256];
274 // Function prototypes
275 template<PieceType Piece>
276 void evaluate_pieces(const Position& p, Color us, EvalInfo& ei);
279 void evaluate_pieces<KING>(const Position& p, Color us, EvalInfo &ei);
281 void evaluate_passed_pawns(const Position &pos, EvalInfo &ei);
282 void evaluate_trapped_bishop_a7h7(const Position &pos, Square s, Color us,
284 void evaluate_trapped_bishop_a1h1(const Position &pos, Square s, Color us,
287 void evaluate_space(const Position &p, Color us, EvalInfo &ei);
288 inline Value apply_weight(Value v, int w);
289 Value scale_by_game_phase(Value mv, Value ev, Phase ph, const ScaleFactor sf[]);
291 int count_1s_8bit(Bitboard b);
293 int compute_weight(int uciWeight, int internalWeight);
294 int weight_option(const std::string& opt, int weight);
304 /// evaluate() is the main evaluation function. It always computes two
305 /// values, an endgame score and a middle game score, and interpolates
306 /// between them based on the remaining material.
308 Value evaluate(const Position &pos, EvalInfo &ei, int threadID) {
311 assert(threadID >= 0 && threadID < THREAD_MAX);
313 memset(&ei, 0, sizeof(EvalInfo));
315 // Initialize by reading the incrementally updated scores included in the
316 // position object (material + piece square tables)
317 ei.mgValue = pos.mg_value();
318 ei.egValue = pos.eg_value();
320 // Probe the material hash table
321 ei.mi = MaterialTable[threadID]->get_material_info(pos);
322 ei.mgValue += ei.mi->mg_value();
323 ei.egValue += ei.mi->eg_value();
325 // If we have a specialized evaluation function for the current material
326 // configuration, call it and return
327 if (ei.mi->specialized_eval_exists())
328 return ei.mi->evaluate(pos);
330 // After get_material_info() call that modifies them
331 ScaleFactor factor[2];
332 factor[WHITE] = ei.mi->scale_factor(pos, WHITE);
333 factor[BLACK] = ei.mi->scale_factor(pos, BLACK);
335 // Probe the pawn hash table
336 ei.pi = PawnTable[threadID]->get_pawn_info(pos);
337 ei.mgValue += apply_weight(ei.pi->mg_value(), WeightPawnStructureMidgame);
338 ei.egValue += apply_weight(ei.pi->eg_value(), WeightPawnStructureEndgame);
340 // Initialize king attack bitboards and king attack zones for both sides
341 ei.attackedBy[WHITE][KING] = pos.piece_attacks<KING>(pos.king_square(WHITE));
342 ei.attackedBy[BLACK][KING] = pos.piece_attacks<KING>(pos.king_square(BLACK));
343 ei.kingZone[WHITE] = ei.attackedBy[BLACK][KING] | (ei.attackedBy[BLACK][KING] >> 8);
344 ei.kingZone[BLACK] = ei.attackedBy[WHITE][KING] | (ei.attackedBy[WHITE][KING] << 8);
346 // Initialize pawn attack bitboards for both sides
347 ei.attackedBy[WHITE][PAWN] = ((pos.pawns(WHITE) << 9) & ~FileABB) | ((pos.pawns(WHITE) << 7) & ~FileHBB);
348 ei.attackedBy[BLACK][PAWN] = ((pos.pawns(BLACK) >> 7) & ~FileABB) | ((pos.pawns(BLACK) >> 9) & ~FileHBB);
349 ei.kingAttackersCount[WHITE] = count_1s_max_15(ei.attackedBy[WHITE][PAWN] & ei.attackedBy[BLACK][KING])/2;
350 ei.kingAttackersCount[BLACK] = count_1s_max_15(ei.attackedBy[BLACK][PAWN] & ei.attackedBy[WHITE][KING])/2;
353 for (Color c = WHITE; c <= BLACK; c++)
355 evaluate_pieces<KNIGHT>(pos, c, ei);
356 evaluate_pieces<BISHOP>(pos, c, ei);
357 evaluate_pieces<ROOK>(pos, c, ei);
358 evaluate_pieces<QUEEN>(pos, c, ei);
360 // Sum up all attacked squares
361 ei.attackedBy[c][0] = ei.attackedBy[c][PAWN] | ei.attackedBy[c][KNIGHT]
362 | ei.attackedBy[c][BISHOP] | ei.attackedBy[c][ROOK]
363 | ei.attackedBy[c][QUEEN] | ei.attackedBy[c][KING];
366 // Kings. Kings are evaluated after all other pieces for both sides,
367 // because we need complete attack information for all pieces when computing
368 // the king safety evaluation.
369 for (Color c = WHITE; c <= BLACK; c++)
370 evaluate_pieces<KING>(pos, c, ei);
372 // Evaluate passed pawns. We evaluate passed pawns for both sides at once,
373 // because we need to know which side promotes first in positions where
374 // both sides have an unstoppable passed pawn.
375 if (ei.pi->passed_pawns())
376 evaluate_passed_pawns(pos, ei);
378 Phase phase = pos.game_phase();
380 // Middle-game specific evaluation terms
381 if (phase > PHASE_ENDGAME)
383 // Pawn storms in positions with opposite castling.
384 if ( square_file(pos.king_square(WHITE)) >= FILE_E
385 && square_file(pos.king_square(BLACK)) <= FILE_D)
387 ei.mgValue += ei.pi->queenside_storm_value(WHITE)
388 - ei.pi->kingside_storm_value(BLACK);
390 else if ( square_file(pos.king_square(WHITE)) <= FILE_D
391 && square_file(pos.king_square(BLACK)) >= FILE_E)
393 ei.mgValue += ei.pi->kingside_storm_value(WHITE)
394 - ei.pi->queenside_storm_value(BLACK);
396 // Evaluate space for both sides
397 if (ei.mi->space_weight() > 0)
399 evaluate_space(pos, WHITE, ei);
400 evaluate_space(pos, BLACK, ei);
405 ei.mgValue += apply_weight(ei.mgMobility, WeightMobilityMidgame);
406 ei.egValue += apply_weight(ei.egMobility, WeightMobilityEndgame);
408 // If we don't already have an unusual scale factor, check for opposite
409 // colored bishop endgames, and use a lower scale for those
410 if ( phase < PHASE_MIDGAME
411 && pos.opposite_colored_bishops()
412 && ( (factor[WHITE] == SCALE_FACTOR_NORMAL && ei.egValue > Value(0))
413 || (factor[BLACK] == SCALE_FACTOR_NORMAL && ei.egValue < Value(0))))
417 // Only the two bishops ?
418 if ( pos.non_pawn_material(WHITE) == BishopValueMidgame
419 && pos.non_pawn_material(BLACK) == BishopValueMidgame)
421 // Check for KBP vs KB with only a single pawn that is almost
422 // certainly a draw or at least two pawns.
423 bool one_pawn = (pos.piece_count(WHITE, PAWN) + pos.piece_count(BLACK, PAWN) == 1);
424 sf = one_pawn ? ScaleFactor(8) : ScaleFactor(32);
427 // Endgame with opposite-colored bishops, but also other pieces. Still
428 // a bit drawish, but not as drawish as with only the two bishops.
429 sf = ScaleFactor(50);
431 if (factor[WHITE] == SCALE_FACTOR_NORMAL)
433 if (factor[BLACK] == SCALE_FACTOR_NORMAL)
437 // Interpolate between the middle game and the endgame score, and
439 Color stm = pos.side_to_move();
441 Value v = Sign[stm] * scale_by_game_phase(ei.mgValue, ei.egValue, phase, factor);
443 return (ei.mateThreat[stm] == MOVE_NONE ? v : 8 * QueenValueMidgame - v);
447 /// quick_evaluate() does a very approximate evaluation of the current position.
448 /// It currently considers only material and piece square table scores. Perhaps
449 /// we should add scores from the pawn and material hash tables?
451 Value quick_evaluate(const Position &pos) {
456 ScaleFactor sf[2] = {SCALE_FACTOR_NORMAL, SCALE_FACTOR_NORMAL};
458 Value mgv = pos.mg_value();
459 Value egv = pos.eg_value();
460 Phase ph = pos.game_phase();
461 Color stm = pos.side_to_move();
463 return Sign[stm] * scale_by_game_phase(mgv, egv, ph, sf);
467 /// init_eval() initializes various tables used by the evaluation function.
469 void init_eval(int threads) {
471 assert(threads <= THREAD_MAX);
473 for (int i = 0; i < THREAD_MAX; i++)
478 delete MaterialTable[i];
480 MaterialTable[i] = NULL;
484 PawnTable[i] = new PawnInfoTable(PawnTableSize);
485 if (!MaterialTable[i])
486 MaterialTable[i] = new MaterialInfoTable(MaterialTableSize);
489 for (Bitboard b = 0ULL; b < 256ULL; b++)
490 BitCount8Bit[b] = count_1s(b);
494 /// quit_eval() releases heap-allocated memory at program termination.
498 for (int i = 0; i < THREAD_MAX; i++)
501 delete MaterialTable[i];
506 /// read_weights() reads evaluation weights from the corresponding UCI
509 void read_weights(Color us) {
511 WeightMobilityMidgame = weight_option("Mobility (Middle Game)", WeightMobilityMidgameInternal);
512 WeightMobilityEndgame = weight_option("Mobility (Endgame)", WeightMobilityEndgameInternal);
513 WeightPawnStructureMidgame = weight_option("Pawn Structure (Middle Game)", WeightPawnStructureMidgameInternal);
514 WeightPawnStructureEndgame = weight_option("Pawn Structure (Endgame)", WeightPawnStructureEndgameInternal);
515 WeightPassedPawnsMidgame = weight_option("Passed Pawns (Middle Game)", WeightPassedPawnsMidgameInternal);
516 WeightPassedPawnsEndgame = weight_option("Passed Pawns (Endgame)", WeightPassedPawnsEndgameInternal);
518 Color them = opposite_color(us);
520 WeightKingSafety[us] = weight_option("Cowardice", WeightKingSafetyInternal);
521 WeightKingSafety[them] = weight_option("Aggressiveness", WeightKingOppSafetyInternal);
522 WeightSpace = weight_option("Space", WeightSpaceInternal);
530 // evaluate_common() computes terms common to all pieces attack
532 template<PieceType Piece>
533 int evaluate_common(const Position& p, const Bitboard& b, Color us, EvalInfo& ei, Square s = SQ_NONE) {
535 static const int AttackWeight[] = { 0, 0, KnightAttackWeight, BishopAttackWeight, RookAttackWeight, QueenAttackWeight };
536 static const Value* MgBonus[] = { 0, 0, MidgameKnightMobilityBonus, MidgameBishopMobilityBonus, MidgameRookMobilityBonus, MidgameQueenMobilityBonus };
537 static const Value* EgBonus[] = { 0, 0, EndgameKnightMobilityBonus, EndgameBishopMobilityBonus, EndgameRookMobilityBonus, EndgameQueenMobilityBonus };
538 static const Value* OutpostBonus[] = { 0, 0, KnightOutpostBonus, BishopOutpostBonus, 0, 0 };
540 Color them = opposite_color(us);
542 // Update attack info
543 ei.attackedBy[us][Piece] |= b;
546 if (b & ei.kingZone[us])
548 ei.kingAttackersCount[us]++;
549 ei.kingAttackersWeight[us] += AttackWeight[Piece];
550 Bitboard bb = (b & ei.attackedBy[them][KING]);
552 ei.kingAdjacentZoneAttacksCount[us] += count_1s_max_15(bb);
555 // Remove squares protected by enemy pawns
556 Bitboard bb = (b & ~ei.attackedBy[them][PAWN]);
559 int mob = (Piece != QUEEN ? count_1s_max_15(bb & ~p.pieces_of_color(us))
560 : count_1s(bb & ~p.pieces_of_color(us)));
562 ei.mgMobility += Sign[us] * MgBonus[Piece][mob];
563 ei.egMobility += Sign[us] * EgBonus[Piece][mob];
565 // Bishop and Knight outposts
566 if ( (Piece != BISHOP && Piece != KNIGHT) // compile time condition
567 || !p.square_is_weak(s, them))
570 // Initial bonus based on square
572 v = bonus = OutpostBonus[Piece][relative_square(us, s)];
574 // Increase bonus if supported by pawn, especially if the opponent has
575 // no minor piece which can exchange the outpost piece
576 if (v && (p.pawn_attacks(them, s) & p.pawns(us)))
579 if ( p.piece_count(them, KNIGHT) == 0
580 && (SquaresByColorBB[square_color(s)] & p.bishops(them)) == EmptyBoardBB)
583 ei.mgValue += Sign[us] * bonus;
584 ei.egValue += Sign[us] * bonus;
589 // evaluate_pieces<>() assigns bonuses and penalties to the pieces of a given
592 template<PieceType Piece>
593 void evaluate_pieces(const Position& pos, Color us, EvalInfo& ei) {
597 for (int i = 0; i < pos.piece_count(us, Piece); i++)
599 Square s = pos.piece_list(us, Piece, i);
601 if (Piece == KNIGHT || Piece == QUEEN)
602 b = pos.piece_attacks<Piece>(s);
603 else if (Piece == BISHOP)
604 b = bishop_attacks_bb(s, pos.occupied_squares() & ~pos.queens(us));
605 else if (Piece == ROOK)
606 b = rook_attacks_bb(s, pos.occupied_squares() & ~pos.rooks_and_queens(us));
608 // Attacks, mobility and outposts
609 int mob = evaluate_common<Piece>(pos, b, us, ei, s);
611 // Special patterns: trapped bishops on a7/h7/a2/h2
612 // and trapped bishops on a1/h1/a8/h8 in Chess960.
615 if (bit_is_set(MaskA7H7[us], s))
616 evaluate_trapped_bishop_a7h7(pos, s, us, ei);
618 if (Chess960 && bit_is_set(MaskA1H1[us], s))
619 evaluate_trapped_bishop_a1h1(pos, s, us, ei);
622 if (Piece != ROOK && Piece != QUEEN)
625 // Queen or rook on 7th rank
626 Color them = opposite_color(us);
628 if ( relative_rank(us, s) == RANK_7
629 && relative_rank(us, pos.king_square(them)) == RANK_8)
631 ei.mgValue += Sign[us] * (Piece == ROOK ? MidgameRookOn7thBonus : MidgameQueenOn7thBonus);
632 ei.egValue += Sign[us] * (Piece == ROOK ? EndgameRookOn7thBonus : EndgameQueenOn7thBonus);
635 // Special extra evaluation for rooks
639 // Open and half-open files
640 File f = square_file(s);
641 if (ei.pi->file_is_half_open(us, f))
643 if (ei.pi->file_is_half_open(them, f))
645 ei.mgValue += Sign[us] * RookOpenFileBonus;
646 ei.egValue += Sign[us] * RookOpenFileBonus;
650 ei.mgValue += Sign[us] * RookHalfOpenFileBonus;
651 ei.egValue += Sign[us] * RookHalfOpenFileBonus;
655 // Penalize rooks which are trapped inside a king. Penalize more if
656 // king has lost right to castle.
657 if (mob > 6 || ei.pi->file_is_half_open(us, f))
660 Square ksq = pos.king_square(us);
662 if ( square_file(ksq) >= FILE_E
663 && square_file(s) > square_file(ksq)
664 && (relative_rank(us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
666 // Is there a half-open file between the king and the edge of the board?
667 if (!ei.pi->has_open_file_to_right(us, square_file(ksq)))
668 ei.mgValue -= pos.can_castle(us)? Sign[us] * ((TrappedRookPenalty - mob * 16) / 2)
669 : Sign[us] * (TrappedRookPenalty - mob * 16);
671 else if ( square_file(ksq) <= FILE_D
672 && square_file(s) < square_file(ksq)
673 && (relative_rank(us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
675 // Is there a half-open file between the king and the edge of the board?
676 if (!ei.pi->has_open_file_to_left(us, square_file(ksq)))
677 ei.mgValue -= pos.can_castle(us)? Sign[us] * ((TrappedRookPenalty - mob * 16) / 2)
678 : Sign[us] * (TrappedRookPenalty - mob * 16);
683 inline Bitboard shiftRowsDown(const Bitboard& b, int num) {
685 return b >> (num << 3);
688 // evaluate_pieces<KING>() assigns bonuses and penalties to a king of a given
692 void evaluate_pieces<KING>(const Position& p, Color us, EvalInfo& ei) {
694 int shelter = 0, sign = Sign[us];
695 Square s = p.king_square(us);
698 if (relative_rank(us, s) <= RANK_4)
700 Bitboard pawns = p.pawns(us) & this_and_neighboring_files_bb(s);
701 Rank r = square_rank(s);
702 for (int i = 1; i < 4; i++)
703 shelter += count_1s_8bit(shiftRowsDown(pawns, r+i*sign)) * (128>>i);
705 ei.mgValue += sign * Value(shelter);
708 // King safety. This is quite complicated, and is almost certainly far
709 // from optimally tuned.
710 Color them = opposite_color(us);
712 if ( p.piece_count(them, QUEEN) >= 1
713 && ei.kingAttackersCount[them] >= 2
714 && p.non_pawn_material(them) >= QueenValueMidgame + RookValueMidgame
715 && ei.kingAdjacentZoneAttacksCount[them])
717 // Is it the attackers turn to move?
718 bool sente = (them == p.side_to_move());
720 // Find the attacked squares around the king which has no defenders
721 // apart from the king itself
722 Bitboard undefended =
723 ei.attacked_by(them) & ~ei.attacked_by(us, PAWN)
724 & ~ei.attacked_by(us, KNIGHT) & ~ei.attacked_by(us, BISHOP)
725 & ~ei.attacked_by(us, ROOK) & ~ei.attacked_by(us, QUEEN)
726 & ei.attacked_by(us, KING);
728 Bitboard occ = p.occupied_squares(), b, b2;
730 // Initialize the 'attackUnits' variable, which is used later on as an
731 // index to the SafetyTable[] array. The initial value is based on the
732 // number and types of the attacking pieces, the number of attacked and
733 // undefended squares around the king, the square of the king, and the
734 // quality of the pawn shelter.
736 Min((ei.kingAttackersCount[them] * ei.kingAttackersWeight[them]) / 2, 25)
737 + (ei.kingAdjacentZoneAttacksCount[them] + count_1s_max_15(undefended)) * 3
738 + InitKingDanger[relative_square(us, s)] - (shelter >> 5);
740 // Analyse safe queen contact checks
741 b = undefended & ei.attacked_by(them, QUEEN) & ~p.pieces_of_color(them);
744 Bitboard attackedByOthers =
745 ei.attacked_by(them, PAWN) | ei.attacked_by(them, KNIGHT)
746 | ei.attacked_by(them, BISHOP) | ei.attacked_by(them, ROOK);
748 b &= attackedByOthers;
751 // The bitboard b now contains the squares available for safe queen
753 int count = count_1s_max_15(b);
754 attackUnits += QueenContactCheckBonus * count * (sente ? 2 : 1);
756 // Is there a mate threat?
757 if (QueenContactMates && !p.is_check())
759 Bitboard escapeSquares =
760 p.piece_attacks<KING>(s) & ~p.pieces_of_color(us) & ~attackedByOthers;
764 Square from, to = pop_1st_bit(&b);
765 if (!(escapeSquares & ~queen_attacks_bb(to, occ & ClearMaskBB[s])))
767 // We have a mate, unless the queen is pinned or there
768 // is an X-ray attack through the queen.
769 for (int i = 0; i < p.piece_count(them, QUEEN); i++)
771 from = p.piece_list(them, QUEEN, i);
772 if ( bit_is_set(p.piece_attacks<QUEEN>(from), to)
773 && !bit_is_set(p.pinned_pieces(them), from)
774 && !(rook_attacks_bb(to, occ & ClearMaskBB[from]) & p.rooks_and_queens(us))
775 && !(rook_attacks_bb(to, occ & ClearMaskBB[from]) & p.rooks_and_queens(us)))
777 ei.mateThreat[them] = make_move(from, to);
785 // Analyse safe distance checks
786 if (QueenCheckBonus > 0 || RookCheckBonus > 0)
788 b = p.piece_attacks<ROOK>(s) & ~p.pieces_of_color(them) & ~ei.attacked_by(us);
791 b2 = b & ei.attacked_by(them, QUEEN);
793 attackUnits += QueenCheckBonus * count_1s_max_15(b2);
796 b2 = b & ei.attacked_by(them, ROOK);
798 attackUnits += RookCheckBonus * count_1s_max_15(b2);
800 if (QueenCheckBonus > 0 || BishopCheckBonus > 0)
802 b = p.piece_attacks<BISHOP>(s) & ~p.pieces_of_color(them) & ~ei.attacked_by(us);
805 b2 = b & ei.attacked_by(them, QUEEN);
807 attackUnits += QueenCheckBonus * count_1s_max_15(b2);
810 b2 = b & ei.attacked_by(them, BISHOP);
812 attackUnits += BishopCheckBonus * count_1s_max_15(b2);
814 if (KnightCheckBonus > 0)
816 b = p.piece_attacks<KNIGHT>(s) & ~p.pieces_of_color(them) & ~ei.attacked_by(us);
819 b2 = b & ei.attacked_by(them, KNIGHT);
821 attackUnits += KnightCheckBonus * count_1s_max_15(b2);
824 // Analyse discovered checks (only for non-pawns right now, consider
825 // adding pawns later).
826 if (DiscoveredCheckBonus)
828 b = p.discovered_check_candidates(them) & ~p.pawns();
830 attackUnits += DiscoveredCheckBonus * count_1s_max_15(b) * (sente? 2 : 1);
833 // Has a mate threat been found? We don't do anything here if the
834 // side with the mating move is the side to move, because in that
835 // case the mating side will get a huge bonus at the end of the main
836 // evaluation function instead.
837 if (ei.mateThreat[them] != MOVE_NONE)
838 attackUnits += MateThreatBonus;
840 // Ensure that attackUnits is between 0 and 99, in order to avoid array
841 // out of bounds errors:
845 if (attackUnits >= 100)
848 // Finally, extract the king safety score from the SafetyTable[] array.
849 // Add the score to the evaluation, and also to ei.futilityMargin. The
850 // reason for adding the king safety score to the futility margin is
851 // that the king safety scores can sometimes be very big, and that
852 // capturing a single attacking piece can therefore result in a score
853 // change far bigger than the value of the captured piece.
854 Value v = apply_weight(SafetyTable[attackUnits], WeightKingSafety[us]);
856 ei.mgValue -= sign * v;
858 if (us == p.side_to_move())
859 ei.futilityMargin += v;
864 // evaluate_passed_pawns() evaluates the passed pawns for both sides.
866 void evaluate_passed_pawns(const Position &pos, EvalInfo &ei) {
868 bool hasUnstoppable[2] = {false, false};
869 int movesToGo[2] = {100, 100};
871 for (Color us = WHITE; us <= BLACK; us++)
873 Color them = opposite_color(us);
874 Square ourKingSq = pos.king_square(us);
875 Square theirKingSq = pos.king_square(them);
876 Bitboard b = ei.pi->passed_pawns() & pos.pawns(us), b2, b3, b4;
880 Square s = pop_1st_bit(&b);
882 assert(pos.piece_on(s) == piece_of_color_and_type(us, PAWN));
883 assert(pos.pawn_is_passed(us, s));
885 int r = int(relative_rank(us, s) - RANK_2);
886 int tr = Max(0, r * (r - 1));
887 Square blockSq = s + pawn_push(us);
889 // Base bonus based on rank
890 Value mbonus = Value(20 * tr);
891 Value ebonus = Value(10 + r * r * 10);
893 // Adjust bonus based on king proximity
896 ebonus -= Value(square_distance(ourKingSq, blockSq) * 3 * tr);
897 ebonus -= Value(square_distance(ourKingSq, blockSq + pawn_push(us)) * 1 * tr);
898 ebonus += Value(square_distance(theirKingSq, blockSq) * 6 * tr);
900 // If the pawn is free to advance, increase bonus
901 if (pos.square_is_empty(blockSq))
903 b2 = squares_in_front_of(us, s);
904 b3 = b2 & ei.attacked_by(them);
905 b4 = b2 & ei.attacked_by(us);
907 // If there is an enemy rook or queen attacking the pawn from behind,
908 // add all X-ray attacks by the rook or queen.
909 if ( bit_is_set(ei.attacked_by(them,ROOK) | ei.attacked_by(them,QUEEN),s)
910 && (squares_behind(us, s) & pos.rooks_and_queens(them)))
913 if ((b2 & pos.pieces_of_color(them)) == EmptyBoardBB)
915 // There are no enemy pieces in the pawn's path! Are any of the
916 // squares in the pawn's path attacked by the enemy?
917 if (b3 == EmptyBoardBB)
918 // No enemy attacks, huge bonus!
919 ebonus += Value(tr * (b2 == b4 ? 17 : 15));
921 // OK, there are enemy attacks. Are those squares which are
922 // attacked by the enemy also attacked by us? If yes, big bonus
923 // (but smaller than when there are no enemy attacks), if no,
924 // somewhat smaller bonus.
925 ebonus += Value(tr * ((b3 & b4) == b3 ? 13 : 8));
929 // There are some enemy pieces in the pawn's path. While this is
930 // sad, we still assign a moderate bonus if all squares in the path
931 // which are either occupied by or attacked by enemy pieces are
932 // also attacked by us.
933 if (((b3 | (b2 & pos.pieces_of_color(them))) & ~b4) == EmptyBoardBB)
934 ebonus += Value(tr * 6);
936 // At last, add a small bonus when there are no *friendly* pieces
937 // in the pawn's path.
938 if ((b2 & pos.pieces_of_color(us)) == EmptyBoardBB)
943 // If the pawn is supported by a friendly pawn, increase bonus
944 b2 = pos.pawns(us) & neighboring_files_bb(s);
946 ebonus += Value(r * 20);
947 else if (pos.pawn_attacks(them, s) & b2)
948 ebonus += Value(r * 12);
950 // If the other side has only a king, check whether the pawn is
952 if (pos.non_pawn_material(them) == Value(0))
957 qsq = relative_square(us, make_square(square_file(s), RANK_8));
958 d = square_distance(s, qsq)
959 - square_distance(theirKingSq, qsq)
960 + (us != pos.side_to_move());
964 int mtg = RANK_8 - relative_rank(us, s);
965 int blockerCount = count_1s_max_15(squares_in_front_of(us,s) & pos.occupied_squares());
970 hasUnstoppable[us] = true;
971 movesToGo[us] = Min(movesToGo[us], mtg);
975 // Rook pawns are a special case: They are sometimes worse, and
976 // sometimes better than other passed pawns. It is difficult to find
977 // good rules for determining whether they are good or bad. For now,
978 // we try the following: Increase the value for rook pawns if the
979 // other side has no pieces apart from a knight, and decrease the
980 // value if the other side has a rook or queen.
981 if (square_file(s) == FILE_A || square_file(s) == FILE_H)
983 if( pos.non_pawn_material(them) <= KnightValueMidgame
984 && pos.piece_count(them, KNIGHT) <= 1)
985 ebonus += ebonus / 4;
986 else if(pos.rooks_and_queens(them))
987 ebonus -= ebonus / 4;
990 // Add the scores for this pawn to the middle game and endgame eval.
991 ei.mgValue += apply_weight(Sign[us] * mbonus, WeightPassedPawnsMidgame);
992 ei.egValue += apply_weight(Sign[us] * ebonus, WeightPassedPawnsEndgame);
996 // Does either side have an unstoppable passed pawn?
997 if (hasUnstoppable[WHITE] && !hasUnstoppable[BLACK])
998 ei.egValue += UnstoppablePawnValue - Value(0x40 * movesToGo[WHITE]);
999 else if (hasUnstoppable[BLACK] && !hasUnstoppable[WHITE])
1000 ei.egValue -= UnstoppablePawnValue - Value(0x40 * movesToGo[BLACK]);
1001 else if (hasUnstoppable[BLACK] && hasUnstoppable[WHITE])
1003 // Both sides have unstoppable pawns! Try to find out who queens
1004 // first. We begin by transforming 'movesToGo' to the number of
1005 // plies until the pawn queens for both sides.
1006 movesToGo[WHITE] *= 2;
1007 movesToGo[BLACK] *= 2;
1008 movesToGo[pos.side_to_move()]--;
1010 // If one side queens at least three plies before the other, that
1012 if (movesToGo[WHITE] <= movesToGo[BLACK] - 3)
1013 ei.egValue += UnstoppablePawnValue - Value(0x40 * (movesToGo[WHITE]/2));
1014 else if(movesToGo[BLACK] <= movesToGo[WHITE] - 3)
1015 ei.egValue -= UnstoppablePawnValue - Value(0x40 * (movesToGo[BLACK]/2));
1017 // We could also add some rules about the situation when one side
1018 // queens exactly one ply before the other: Does the first queen
1019 // check the opponent's king, or attack the opponent's queening square?
1020 // This is slightly tricky to get right, because it is possible that
1021 // the opponent's king has moved somewhere before the first pawn queens.
1026 // evaluate_trapped_bishop_a7h7() determines whether a bishop on a7/h7
1027 // (a2/h2 for black) is trapped by enemy pawns, and assigns a penalty
1030 void evaluate_trapped_bishop_a7h7(const Position &pos, Square s, Color us,
1032 assert(square_is_ok(s));
1033 assert(pos.piece_on(s) == piece_of_color_and_type(us, BISHOP));
1035 Square b6 = relative_square(us, (square_file(s) == FILE_A) ? SQ_B6 : SQ_G6);
1036 Square b8 = relative_square(us, (square_file(s) == FILE_A) ? SQ_B8 : SQ_G8);
1038 if ( pos.piece_on(b6) == piece_of_color_and_type(opposite_color(us), PAWN)
1039 && pos.see(s, b6) < 0
1040 && pos.see(s, b8) < 0)
1042 ei.mgValue -= Sign[us] * TrappedBishopA7H7Penalty;
1043 ei.egValue -= Sign[us] * TrappedBishopA7H7Penalty;
1048 // evaluate_trapped_bishop_a1h1() determines whether a bishop on a1/h1
1049 // (a8/h8 for black) is trapped by a friendly pawn on b2/g2 (b7/g7 for
1050 // black), and assigns a penalty if it is. This pattern can obviously
1051 // only occur in Chess960 games.
1053 void evaluate_trapped_bishop_a1h1(const Position &pos, Square s, Color us,
1055 Piece pawn = piece_of_color_and_type(us, PAWN);
1059 assert(square_is_ok(s));
1060 assert(pos.piece_on(s) == piece_of_color_and_type(us, BISHOP));
1062 if (square_file(s) == FILE_A)
1064 b2 = relative_square(us, SQ_B2);
1065 b3 = relative_square(us, SQ_B3);
1066 c3 = relative_square(us, SQ_C3);
1070 b2 = relative_square(us, SQ_G2);
1071 b3 = relative_square(us, SQ_G3);
1072 c3 = relative_square(us, SQ_F3);
1075 if (pos.piece_on(b2) == pawn)
1079 if (!pos.square_is_empty(b3))
1080 penalty = 2*TrappedBishopA1H1Penalty;
1081 else if (pos.piece_on(c3) == pawn)
1082 penalty = TrappedBishopA1H1Penalty;
1084 penalty = TrappedBishopA1H1Penalty / 2;
1086 ei.mgValue -= Sign[us] * penalty;
1087 ei.egValue -= Sign[us] * penalty;
1092 // evaluate_space() computes the space evaluation for a given side. The
1093 // space evaluation is a simple bonus based on the number of safe squares
1094 // available for minor pieces on the central four files on ranks 2--4. Safe
1095 // squares one, two or three squares behind a friendly pawn are counted
1096 // twice. Finally, the space bonus is scaled by a weight taken from the
1097 // material hash table.
1099 void evaluate_space(const Position &pos, Color us, EvalInfo &ei) {
1101 Color them = opposite_color(us);
1103 // Find the safe squares for our pieces inside the area defined by
1104 // SpaceMask[us]. A square is unsafe it is attacked by an enemy
1105 // pawn, or if it is undefended and attacked by an enemy piece.
1107 Bitboard safeSquares = SpaceMask[us]
1109 & ~ei.attacked_by(them, PAWN)
1110 & ~(~ei.attacked_by(us) & ei.attacked_by(them));
1112 // Find all squares which are at most three squares behind some friendly
1114 Bitboard behindFriendlyPawns = pos.pawns(us);
1117 behindFriendlyPawns |= (behindFriendlyPawns >> 8);
1118 behindFriendlyPawns |= (behindFriendlyPawns >> 16);
1122 behindFriendlyPawns |= (behindFriendlyPawns << 8);
1123 behindFriendlyPawns |= (behindFriendlyPawns << 16);
1126 int space = count_1s_max_15(safeSquares)
1127 + count_1s_max_15(behindFriendlyPawns & safeSquares);
1129 ei.mgValue += Sign[us] * apply_weight(Value(space * ei.mi->space_weight()), WeightSpace);
1133 // apply_weight() applies an evaluation weight to a value
1135 inline Value apply_weight(Value v, int w) {
1136 return (v*w) / 0x100;
1140 // scale_by_game_phase() interpolates between a middle game and an endgame
1141 // score, based on game phase. It also scales the return value by a
1142 // ScaleFactor array.
1144 Value scale_by_game_phase(Value mv, Value ev, Phase ph, const ScaleFactor sf[]) {
1146 assert(mv > -VALUE_INFINITE && mv < VALUE_INFINITE);
1147 assert(ev > -VALUE_INFINITE && ev < VALUE_INFINITE);
1148 assert(ph >= PHASE_ENDGAME && ph <= PHASE_MIDGAME);
1150 ev = apply_scale_factor(ev, sf[(ev > Value(0) ? WHITE : BLACK)]);
1152 Value result = Value(int((mv * ph + ev * (128 - ph)) / 128));
1153 return Value(int(result) & ~(GrainSize - 1));
1157 // count_1s_8bit() counts the number of nonzero bits in the 8 least
1158 // significant bits of a Bitboard. This function is used by the king
1159 // shield evaluation.
1161 int count_1s_8bit(Bitboard b) {
1162 return int(BitCount8Bit[b & 0xFF]);
1166 // compute_weight() computes the value of an evaluation weight, by combining
1167 // an UCI-configurable weight with an internal weight.
1169 int compute_weight(int uciWeight, int internalWeight) {
1171 uciWeight = (uciWeight * 0x100) / 100;
1172 return (uciWeight * internalWeight) / 0x100;
1176 // helper used in read_weights()
1177 int weight_option(const std::string& opt, int weight) {
1179 return compute_weight(get_option_value_int(opt), weight);
1183 // init_safety() initizes the king safety evaluation, based on UCI
1184 // parameters. It is called from read_weights().
1186 void init_safety() {
1188 QueenContactCheckBonus = get_option_value_int("Queen Contact Check Bonus");
1189 QueenCheckBonus = get_option_value_int("Queen Check Bonus");
1190 RookCheckBonus = get_option_value_int("Rook Check Bonus");
1191 BishopCheckBonus = get_option_value_int("Bishop Check Bonus");
1192 KnightCheckBonus = get_option_value_int("Knight Check Bonus");
1193 DiscoveredCheckBonus = get_option_value_int("Discovered Check Bonus");
1194 MateThreatBonus = get_option_value_int("Mate Threat Bonus");
1196 int maxSlope = get_option_value_int("King Safety Max Slope");
1197 int peak = get_option_value_int("King Safety Max Value") * 256 / 100;
1198 double a = get_option_value_int("King Safety Coefficient") / 100.0;
1199 double b = get_option_value_int("King Safety X Intercept");
1200 bool quad = (get_option_value_string("King Safety Curve") == "Quadratic");
1201 bool linear = (get_option_value_string("King Safety Curve") == "Linear");
1203 for (int i = 0; i < 100; i++)
1206 SafetyTable[i] = Value(0);
1208 SafetyTable[i] = Value((int)(a * (i - b) * (i - b)));
1210 SafetyTable[i] = Value((int)(100 * a * (i - b)));
1213 for (int i = 0; i < 100; i++)
1215 if (SafetyTable[i+1] - SafetyTable[i] > maxSlope)
1216 for (int j = i + 1; j < 100; j++)
1217 SafetyTable[j] = SafetyTable[j-1] + Value(maxSlope);
1219 if (SafetyTable[i] > Value(peak))
1220 SafetyTable[i] = Value(peak);