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 void evaluate_knight(const Position &p, Square s, Color us, EvalInfo &ei);
276 void evaluate_bishop(const Position &p, Square s, Color us, EvalInfo &ei);
277 void evaluate_rook(const Position &p, Square s, Color us, EvalInfo &ei);
278 void evaluate_queen(const Position &p, Square s, Color us, EvalInfo &ei);
279 void evaluate_king(const Position &p, Square s, 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++)
356 for (int i = 0; i < pos.piece_count(c, KNIGHT); i++)
357 evaluate_knight(pos, pos.piece_list(c, KNIGHT, i), c, ei);
360 for (int i = 0; i < pos.piece_count(c, BISHOP); i++)
361 evaluate_bishop(pos, pos.piece_list(c, BISHOP, i), c, ei);
364 for (int i = 0; i < pos.piece_count(c, ROOK); i++)
365 evaluate_rook(pos, pos.piece_list(c, ROOK, i), c, ei);
368 for(int i = 0; i < pos.piece_count(c, QUEEN); i++)
369 evaluate_queen(pos, pos.piece_list(c, QUEEN, i), c, ei);
371 // Special pattern: trapped bishops on a7/h7/a2/h2
372 Bitboard b = pos.bishops(c) & MaskA7H7[c];
375 Square s = pop_1st_bit(&b);
376 evaluate_trapped_bishop_a7h7(pos, s, c, ei);
379 // Special pattern: trapped bishops on a1/h1/a8/h8 in Chess960:
382 b = pos.bishops(c) & MaskA1H1[c];
385 Square s = pop_1st_bit(&b);
386 evaluate_trapped_bishop_a1h1(pos, s, c, ei);
390 // Sum up all attacked squares
391 ei.attackedBy[c][0] = ei.attackedBy[c][PAWN] | ei.attackedBy[c][KNIGHT]
392 | ei.attackedBy[c][BISHOP] | ei.attackedBy[c][ROOK]
393 | ei.attackedBy[c][QUEEN] | ei.attackedBy[c][KING];
396 // Kings. Kings are evaluated after all other pieces for both sides,
397 // because we need complete attack information for all pieces when computing
398 // the king safety evaluation.
399 for (Color c = WHITE; c <= BLACK; c++)
400 evaluate_king(pos, pos.king_square(c), c, ei);
402 // Evaluate passed pawns. We evaluate passed pawns for both sides at once,
403 // because we need to know which side promotes first in positions where
404 // both sides have an unstoppable passed pawn.
405 if (ei.pi->passed_pawns())
406 evaluate_passed_pawns(pos, ei);
408 Phase phase = pos.game_phase();
410 // Middle-game specific evaluation terms
411 if (phase > PHASE_ENDGAME)
413 // Pawn storms in positions with opposite castling.
414 if ( square_file(pos.king_square(WHITE)) >= FILE_E
415 && square_file(pos.king_square(BLACK)) <= FILE_D)
417 ei.mgValue += ei.pi->queenside_storm_value(WHITE)
418 - ei.pi->kingside_storm_value(BLACK);
420 else if ( square_file(pos.king_square(WHITE)) <= FILE_D
421 && square_file(pos.king_square(BLACK)) >= FILE_E)
423 ei.mgValue += ei.pi->kingside_storm_value(WHITE)
424 - ei.pi->queenside_storm_value(BLACK);
426 // Evaluate space for both sides
427 if (ei.mi->space_weight() > 0)
429 evaluate_space(pos, WHITE, ei);
430 evaluate_space(pos, BLACK, ei);
435 ei.mgValue += apply_weight(ei.mgMobility, WeightMobilityMidgame);
436 ei.egValue += apply_weight(ei.egMobility, WeightMobilityEndgame);
438 // If we don't already have an unusual scale factor, check for opposite
439 // colored bishop endgames, and use a lower scale for those
440 if ( phase < PHASE_MIDGAME
441 && pos.opposite_colored_bishops()
442 && ( (factor[WHITE] == SCALE_FACTOR_NORMAL && ei.egValue > Value(0))
443 || (factor[BLACK] == SCALE_FACTOR_NORMAL && ei.egValue < Value(0))))
447 // Only the two bishops ?
448 if ( pos.non_pawn_material(WHITE) == BishopValueMidgame
449 && pos.non_pawn_material(BLACK) == BishopValueMidgame)
451 // Check for KBP vs KB with only a single pawn that is almost
452 // certainly a draw or at least two pawns.
453 bool one_pawn = (pos.piece_count(WHITE, PAWN) + pos.piece_count(BLACK, PAWN) == 1);
454 sf = one_pawn ? ScaleFactor(8) : ScaleFactor(32);
457 // Endgame with opposite-colored bishops, but also other pieces. Still
458 // a bit drawish, but not as drawish as with only the two bishops.
459 sf = ScaleFactor(50);
461 if (factor[WHITE] == SCALE_FACTOR_NORMAL)
463 if (factor[BLACK] == SCALE_FACTOR_NORMAL)
467 // Interpolate between the middle game and the endgame score, and
469 Color stm = pos.side_to_move();
471 Value v = Sign[stm] * scale_by_game_phase(ei.mgValue, ei.egValue, phase, factor);
473 return (ei.mateThreat[stm] == MOVE_NONE ? v : 8 * QueenValueMidgame - v);
477 /// quick_evaluate() does a very approximate evaluation of the current position.
478 /// It currently considers only material and piece square table scores. Perhaps
479 /// we should add scores from the pawn and material hash tables?
481 Value quick_evaluate(const Position &pos) {
486 ScaleFactor sf[2] = {SCALE_FACTOR_NORMAL, SCALE_FACTOR_NORMAL};
488 Value mgv = pos.mg_value();
489 Value egv = pos.eg_value();
490 Phase ph = pos.game_phase();
491 Color stm = pos.side_to_move();
493 return Sign[stm] * scale_by_game_phase(mgv, egv, ph, sf);
497 /// init_eval() initializes various tables used by the evaluation function.
499 void init_eval(int threads) {
501 assert(threads <= THREAD_MAX);
503 for (int i = 0; i < THREAD_MAX; i++)
508 delete MaterialTable[i];
510 MaterialTable[i] = NULL;
514 PawnTable[i] = new PawnInfoTable(PawnTableSize);
515 if (!MaterialTable[i])
516 MaterialTable[i] = new MaterialInfoTable(MaterialTableSize);
519 for (Bitboard b = 0ULL; b < 256ULL; b++)
520 BitCount8Bit[b] = count_1s(b);
524 /// quit_eval() releases heap-allocated memory at program termination.
528 for (int i = 0; i < THREAD_MAX; i++)
531 delete MaterialTable[i];
536 /// read_weights() reads evaluation weights from the corresponding UCI
539 void read_weights(Color us) {
541 WeightMobilityMidgame = weight_option("Mobility (Middle Game)", WeightMobilityMidgameInternal);
542 WeightMobilityEndgame = weight_option("Mobility (Endgame)", WeightMobilityEndgameInternal);
543 WeightPawnStructureMidgame = weight_option("Pawn Structure (Middle Game)", WeightPawnStructureMidgameInternal);
544 WeightPawnStructureEndgame = weight_option("Pawn Structure (Endgame)", WeightPawnStructureEndgameInternal);
545 WeightPassedPawnsMidgame = weight_option("Passed Pawns (Middle Game)", WeightPassedPawnsMidgameInternal);
546 WeightPassedPawnsEndgame = weight_option("Passed Pawns (Endgame)", WeightPassedPawnsEndgameInternal);
548 Color them = opposite_color(us);
550 WeightKingSafety[us] = weight_option("Cowardice", WeightKingSafetyInternal);
551 WeightKingSafety[them] = weight_option("Aggressiveness", WeightKingOppSafetyInternal);
552 WeightSpace = weight_option("Space", WeightSpaceInternal);
560 // evaluate_common() computes terms common to all pieces attack
562 int evaluate_common(const Position&p, const Bitboard& b, Color us, EvalInfo& ei,
563 int AttackWeight, const Value* mgBonus, const Value* egBonus,
564 Square s = SQ_NONE, const Value* OutpostBonus = NULL) {
566 Color them = opposite_color(us);
569 if (b & ei.kingZone[us])
571 ei.kingAttackersCount[us]++;
572 ei.kingAttackersWeight[us] += AttackWeight;
573 Bitboard bb = (b & ei.attackedBy[them][KING]);
575 ei.kingAdjacentZoneAttacksCount[us] += count_1s_max_15(bb);
579 int mob = count_1s_max_15(b & ~p.pieces_of_color(us));
580 ei.mgMobility += Sign[us] * mgBonus[mob];
581 ei.egMobility += Sign[us] * egBonus[mob];
583 // Bishop and Knight outposts
584 if (!OutpostBonus || !p.square_is_weak(s, them))
587 // Initial bonus based on square
589 v = bonus = OutpostBonus[relative_square(us, s)];
591 // Increase bonus if supported by pawn, especially if the opponent has
592 // no minor piece which can exchange the outpost piece
593 if (v && (p.pawn_attacks(them, s) & p.pawns(us)))
596 if ( p.piece_count(them, KNIGHT) == 0
597 && (SquaresByColorBB[square_color(s)] & p.bishops(them)) == EmptyBoardBB)
600 ei.mgValue += Sign[us] * bonus;
601 ei.egValue += Sign[us] * bonus;
606 // evaluate_knight() assigns bonuses and penalties to a knight of a given
607 // color on a given square.
609 void evaluate_knight(const Position &p, Square s, Color us, EvalInfo &ei) {
611 Bitboard b = p.piece_attacks<KNIGHT>(s);
612 ei.attackedBy[us][KNIGHT] |= b;
614 // King attack, mobility and outposts
615 evaluate_common(p, b, us, ei, KnightAttackWeight, MidgameKnightMobilityBonus,
616 EndgameKnightMobilityBonus, s, KnightOutpostBonus);
620 // evaluate_bishop() assigns bonuses and penalties to a bishop of a given
621 // color on a given square.
623 void evaluate_bishop(const Position &p, Square s, Color us, EvalInfo &ei) {
625 Bitboard b = bishop_attacks_bb(s, p.occupied_squares() & ~p.queens(us));
626 ei.attackedBy[us][BISHOP] |= b;
628 // King attack, mobility and outposts
629 evaluate_common(p, b, us, ei, BishopAttackWeight, MidgameBishopMobilityBonus,
630 EndgameBishopMobilityBonus, s, BishopOutpostBonus);
634 // evaluate_rook() assigns bonuses and penalties to a rook of a given
635 // color on a given square.
637 void evaluate_rook(const Position &p, Square s, Color us, EvalInfo &ei) {
639 Bitboard b = rook_attacks_bb(s, p.occupied_squares() & ~p.rooks_and_queens(us));
640 ei.attackedBy[us][ROOK] |= b;
642 // King attack and mobility
643 int mob = evaluate_common(p, b, us, ei, RookAttackWeight, MidgameRookMobilityBonus,
644 EndgameRookMobilityBonus);
647 Color them = opposite_color(us);
649 if ( relative_rank(us, s) == RANK_7
650 && relative_rank(us, p.king_square(them)) == RANK_8)
652 ei.mgValue += Sign[us] * MidgameRookOn7thBonus;
653 ei.egValue += Sign[us] * EndgameRookOn7thBonus;
656 // Open and half-open files
657 File f = square_file(s);
658 if (ei.pi->file_is_half_open(us, f))
660 if (ei.pi->file_is_half_open(them, f))
662 ei.mgValue += Sign[us] * RookOpenFileBonus;
663 ei.egValue += Sign[us] * RookOpenFileBonus;
667 ei.mgValue += Sign[us] * RookHalfOpenFileBonus;
668 ei.egValue += Sign[us] * RookHalfOpenFileBonus;
672 // Penalize rooks which are trapped inside a king. Penalize more if
673 // king has lost right to castle
674 if (mob > 6 || ei.pi->file_is_half_open(us, f))
677 Square ksq = p.king_square(us);
679 if ( square_file(ksq) >= FILE_E
680 && square_file(s) > square_file(ksq)
681 && (relative_rank(us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
683 // Is there a half-open file between the king and the edge of the board?
684 if (!ei.pi->has_open_file_to_right(us, square_file(ksq)))
685 ei.mgValue -= p.can_castle(us)? Sign[us] * ((TrappedRookPenalty - mob * 16) / 2)
686 : Sign[us] * (TrappedRookPenalty - mob * 16);
688 else if ( square_file(ksq) <= FILE_D
689 && square_file(s) < square_file(ksq)
690 && (relative_rank(us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
692 // Is there a half-open file between the king and the edge of the board?
693 if (!ei.pi->has_open_file_to_left(us, square_file(ksq)))
694 ei.mgValue -= p.can_castle(us)? Sign[us] * ((TrappedRookPenalty - mob * 16) / 2)
695 : Sign[us] * (TrappedRookPenalty - mob * 16);
700 // evaluate_queen() assigns bonuses and penalties to a queen of a given
701 // color on a given square.
703 void evaluate_queen(const Position &p, Square s, Color us, EvalInfo &ei) {
705 Bitboard b = p.piece_attacks<QUEEN>(s);
706 ei.attackedBy[us][QUEEN] |= b;
708 // King attack and mobility
709 evaluate_common(p, b, us, ei, QueenAttackWeight, MidgameQueenMobilityBonus,
710 EndgameQueenMobilityBonus);
713 Color them = opposite_color(us);
715 if ( relative_rank(us, s) == RANK_7
716 && relative_rank(us, p.king_square(them)) == RANK_8)
718 ei.mgValue += Sign[us] * MidgameQueenOn7thBonus;
719 ei.egValue += Sign[us] * EndgameQueenOn7thBonus;
723 inline Bitboard shiftRowsDown(const Bitboard& b, int num) {
725 return b >> (num << 3);
728 // evaluate_king() assigns bonuses and penalties to a king of a given
729 // color on a given square.
731 void evaluate_king(const Position &p, Square s, Color us, EvalInfo &ei) {
733 int shelter = 0, sign = Sign[us];
736 if (relative_rank(us, s) <= RANK_4)
738 Bitboard pawns = p.pawns(us) & this_and_neighboring_files_bb(s);
739 Rank r = square_rank(s);
740 for (int i = 1; i < 4; i++)
741 shelter += count_1s_8bit(shiftRowsDown(pawns, r+i*sign)) * (128>>i);
743 ei.mgValue += sign * Value(shelter);
746 // King safety. This is quite complicated, and is almost certainly far
747 // from optimally tuned.
748 Color them = opposite_color(us);
750 if ( p.piece_count(them, QUEEN) >= 1
751 && ei.kingAttackersCount[them] >= 2
752 && p.non_pawn_material(them) >= QueenValueMidgame + RookValueMidgame
753 && ei.kingAdjacentZoneAttacksCount[them])
755 // Is it the attackers turn to move?
756 bool sente = (them == p.side_to_move());
758 // Find the attacked squares around the king which has no defenders
759 // apart from the king itself
760 Bitboard undefended =
761 ei.attacked_by(them) & ~ei.attacked_by(us, PAWN)
762 & ~ei.attacked_by(us, KNIGHT) & ~ei.attacked_by(us, BISHOP)
763 & ~ei.attacked_by(us, ROOK) & ~ei.attacked_by(us, QUEEN)
764 & ei.attacked_by(us, KING);
766 Bitboard occ = p.occupied_squares(), b, b2;
768 // Initialize the 'attackUnits' variable, which is used later on as an
769 // index to the SafetyTable[] array. The initial value is based on the
770 // number and types of the attacking pieces, the number of attacked and
771 // undefended squares around the king, the square of the king, and the
772 // quality of the pawn shelter.
774 Min((ei.kingAttackersCount[them] * ei.kingAttackersWeight[them]) / 2, 25)
775 + (ei.kingAdjacentZoneAttacksCount[them] + count_1s_max_15(undefended)) * 3
776 + InitKingDanger[relative_square(us, s)] - (shelter >> 5);
778 // Analyse safe queen contact checks
779 b = undefended & ei.attacked_by(them, QUEEN) & ~p.pieces_of_color(them);
782 Bitboard attackedByOthers =
783 ei.attacked_by(them, PAWN) | ei.attacked_by(them, KNIGHT)
784 | ei.attacked_by(them, BISHOP) | ei.attacked_by(them, ROOK);
786 b &= attackedByOthers;
789 // The bitboard b now contains the squares available for safe queen
791 int count = count_1s_max_15(b);
792 attackUnits += QueenContactCheckBonus * count * (sente ? 2 : 1);
794 // Is there a mate threat?
795 if (QueenContactMates && !p.is_check())
797 Bitboard escapeSquares =
798 p.piece_attacks<KING>(s) & ~p.pieces_of_color(us) & ~attackedByOthers;
802 Square from, to = pop_1st_bit(&b);
803 if (!(escapeSquares & ~queen_attacks_bb(to, occ & ClearMaskBB[s])))
805 // We have a mate, unless the queen is pinned or there
806 // is an X-ray attack through the queen.
807 for (int i = 0; i < p.piece_count(them, QUEEN); i++)
809 from = p.piece_list(them, QUEEN, i);
810 if ( bit_is_set(p.piece_attacks<QUEEN>(from), to)
811 && !bit_is_set(p.pinned_pieces(them), from)
812 && !(rook_attacks_bb(to, occ & ClearMaskBB[from]) & p.rooks_and_queens(us))
813 && !(rook_attacks_bb(to, occ & ClearMaskBB[from]) & p.rooks_and_queens(us)))
815 ei.mateThreat[them] = make_move(from, to);
823 // Analyse safe distance checks
824 if (QueenCheckBonus > 0 || RookCheckBonus > 0)
826 b = p.piece_attacks<ROOK>(s) & ~p.pieces_of_color(them) & ~ei.attacked_by(us);
829 b2 = b & ei.attacked_by(them, QUEEN);
831 attackUnits += QueenCheckBonus * count_1s_max_15(b2);
834 b2 = b & ei.attacked_by(them, ROOK);
836 attackUnits += RookCheckBonus * count_1s_max_15(b2);
838 if (QueenCheckBonus > 0 || BishopCheckBonus > 0)
840 b = p.piece_attacks<BISHOP>(s) & ~p.pieces_of_color(them) & ~ei.attacked_by(us);
843 b2 = b & ei.attacked_by(them, QUEEN);
845 attackUnits += QueenCheckBonus * count_1s_max_15(b2);
848 b2 = b & ei.attacked_by(them, BISHOP);
850 attackUnits += BishopCheckBonus * count_1s_max_15(b2);
852 if (KnightCheckBonus > 0)
854 b = p.piece_attacks<KNIGHT>(s) & ~p.pieces_of_color(them) & ~ei.attacked_by(us);
857 b2 = b & ei.attacked_by(them, KNIGHT);
859 attackUnits += KnightCheckBonus * count_1s_max_15(b2);
862 // Analyse discovered checks (only for non-pawns right now, consider
863 // adding pawns later).
864 if (DiscoveredCheckBonus)
866 b = p.discovered_check_candidates(them) & ~p.pawns();
868 attackUnits += DiscoveredCheckBonus * count_1s_max_15(b) * (sente? 2 : 1);
871 // Has a mate threat been found? We don't do anything here if the
872 // side with the mating move is the side to move, because in that
873 // case the mating side will get a huge bonus at the end of the main
874 // evaluation function instead.
875 if (ei.mateThreat[them] != MOVE_NONE)
876 attackUnits += MateThreatBonus;
878 // Ensure that attackUnits is between 0 and 99, in order to avoid array
879 // out of bounds errors:
883 if (attackUnits >= 100)
886 // Finally, extract the king safety score from the SafetyTable[] array.
887 // Add the score to the evaluation, and also to ei.futilityMargin. The
888 // reason for adding the king safety score to the futility margin is
889 // that the king safety scores can sometimes be very big, and that
890 // capturing a single attacking piece can therefore result in a score
891 // change far bigger than the value of the captured piece.
892 Value v = apply_weight(SafetyTable[attackUnits], WeightKingSafety[us]);
894 ei.mgValue -= sign * v;
896 if (us == p.side_to_move())
897 ei.futilityMargin += v;
902 // evaluate_passed_pawns() evaluates the passed pawns for both sides.
904 void evaluate_passed_pawns(const Position &pos, EvalInfo &ei) {
905 bool hasUnstoppable[2] = {false, false};
906 int movesToGo[2] = {100, 100};
908 for(Color us = WHITE; us <= BLACK; us++) {
909 Color them = opposite_color(us);
910 Square ourKingSq = pos.king_square(us);
911 Square theirKingSq = pos.king_square(them);
912 Bitboard b = ei.pi->passed_pawns() & pos.pawns(us), b2, b3, b4;
915 Square s = pop_1st_bit(&b);
916 assert(pos.piece_on(s) == pawn_of_color(us));
917 assert(pos.pawn_is_passed(us, s));
919 int r = int(relative_rank(us, s) - RANK_2);
920 int tr = Max(0, r * (r-1));
921 Square blockSq = s + pawn_push(us);
923 // Base bonus based on rank:
924 Value mbonus = Value(20 * tr);
925 Value ebonus = Value(10 + r * r * 10);
927 // Adjust bonus based on king proximity:
928 ebonus -= Value(square_distance(ourKingSq, blockSq) * 3 * tr);
930 Value(square_distance(ourKingSq, blockSq + pawn_push(us)) * 1 * tr);
931 ebonus += Value(square_distance(theirKingSq, blockSq) * 6 * tr);
933 // If the pawn is free to advance, increase bonus:
934 if(pos.square_is_empty(blockSq)) {
936 b2 = squares_in_front_of(us, s);
937 b3 = b2 & ei.attacked_by(them);
938 b4 = b2 & ei.attacked_by(us);
940 // If there is an enemy rook or queen attacking the pawn from behind,
941 // add all X-ray attacks by the rook or queen.
942 if(bit_is_set(ei.attacked_by(them,ROOK)|ei.attacked_by(them,QUEEN),s)
943 && squares_behind(us, s) & pos.rooks_and_queens(them))
946 if((b2 & pos.pieces_of_color(them)) == EmptyBoardBB) {
947 // There are no enemy pieces in the pawn's path! Are any of the
948 // squares in the pawn's path attacked by the enemy?
949 if(b3 == EmptyBoardBB)
950 // No enemy attacks, huge bonus!
951 ebonus += Value(tr * ((b2 == b4)? 17 : 15));
953 // OK, there are enemy attacks. Are those squares which are
954 // attacked by the enemy also attacked by us? If yes, big bonus
955 // (but smaller than when there are no enemy attacks), if no,
956 // somewhat smaller bonus.
957 ebonus += Value(tr * (((b3 & b4) == b3)? 13 : 8));
960 // There are some enemy pieces in the pawn's path. While this is
961 // sad, we still assign a moderate bonus if all squares in the path
962 // which are either occupied by or attacked by enemy pieces are
963 // also attacked by us.
964 if(((b3 | (b2 & pos.pieces_of_color(them))) & ~b4) == EmptyBoardBB)
965 ebonus += Value(tr * 6);
967 // At last, add a small bonus when there are no *friendly* pieces
968 // in the pawn's path:
969 if((b2 & pos.pieces_of_color(us)) == EmptyBoardBB)
973 // If the pawn is supported by a friendly pawn, increase bonus.
974 b2 = pos.pawns(us) & neighboring_files_bb(s);
976 ebonus += Value(r * 20);
977 else if(pos.pawn_attacks(them, s) & b2)
978 ebonus += Value(r * 12);
980 // If the other side has only a king, check whether the pawn is
982 if(pos.non_pawn_material(them) == Value(0)) {
986 qsq = relative_square(us, make_square(square_file(s), RANK_8));
987 d = square_distance(s, qsq) - square_distance(theirKingSq, qsq)
988 + ((us == pos.side_to_move())? 0 : 1);
991 int mtg = RANK_8 - relative_rank(us, s);
993 count_1s_max_15(squares_in_front_of(us,s)&pos.occupied_squares());
997 hasUnstoppable[us] = true;
998 movesToGo[us] = Min(movesToGo[us], mtg);
1002 // Rook pawns are a special case: They are sometimes worse, and
1003 // sometimes better than other passed pawns. It is difficult to find
1004 // good rules for determining whether they are good or bad. For now,
1005 // we try the following: Increase the value for rook pawns if the
1006 // other side has no pieces apart from a knight, and decrease the
1007 // value if the other side has a rook or queen.
1008 if(square_file(s) == FILE_A || square_file(s) == FILE_H) {
1009 if(pos.non_pawn_material(them) == KnightValueMidgame
1010 && pos.piece_count(them, KNIGHT) == 1)
1011 ebonus += ebonus / 4;
1012 else if(pos.rooks_and_queens(them))
1013 ebonus -= ebonus / 4;
1016 // Add the scores for this pawn to the middle game and endgame eval.
1017 ei.mgValue += apply_weight(Sign[us] * mbonus, WeightPassedPawnsMidgame);
1018 ei.egValue += apply_weight(Sign[us] * ebonus, WeightPassedPawnsEndgame);
1022 // Does either side have an unstoppable passed pawn?
1023 if(hasUnstoppable[WHITE] && !hasUnstoppable[BLACK])
1024 ei.egValue += UnstoppablePawnValue - Value(0x40 * movesToGo[WHITE]);
1025 else if(hasUnstoppable[BLACK] && !hasUnstoppable[WHITE])
1026 ei.egValue -= UnstoppablePawnValue - Value(0x40 * movesToGo[BLACK]);
1027 else if(hasUnstoppable[BLACK] && hasUnstoppable[WHITE]) {
1028 // Both sides have unstoppable pawns! Try to find out who queens
1029 // first. We begin by transforming 'movesToGo' to the number of
1030 // plies until the pawn queens for both sides:
1031 movesToGo[WHITE] *= 2;
1032 movesToGo[BLACK] *= 2;
1033 movesToGo[pos.side_to_move()]--;
1035 // If one side queens at least three plies before the other, that
1037 if(movesToGo[WHITE] <= movesToGo[BLACK] - 3)
1038 ei.egValue += UnstoppablePawnValue - Value(0x40 * (movesToGo[WHITE]/2));
1039 else if(movesToGo[BLACK] <= movesToGo[WHITE] - 3)
1040 ei.egValue -= UnstoppablePawnValue - Value(0x40 * (movesToGo[BLACK]/2));
1042 // We could also add some rules about the situation when one side
1043 // queens exactly one ply before the other: Does the first queen
1044 // check the opponent's king, or attack the opponent's queening square?
1045 // This is slightly tricky to get right, because it is possible that
1046 // the opponent's king has moved somewhere before the first pawn queens.
1051 // evaluate_trapped_bishop_a7h7() determines whether a bishop on a7/h7
1052 // (a2/h2 for black) is trapped by enemy pawns, and assigns a penalty
1055 void evaluate_trapped_bishop_a7h7(const Position &pos, Square s, Color us,
1058 assert(square_is_ok(s));
1059 assert(pos.piece_on(s) == bishop_of_color(us));
1061 Square b6 = relative_square(us, (square_file(s) == FILE_A) ? SQ_B6 : SQ_G6);
1062 Square b8 = relative_square(us, (square_file(s) == FILE_A) ? SQ_B8 : SQ_G8);
1064 if ( pos.piece_on(b6) == pawn_of_color(opposite_color(us))
1065 && pos.see(s, b6) < 0
1066 && pos.see(s, b8) < 0)
1068 ei.mgValue -= Sign[us] * TrappedBishopA7H7Penalty;
1069 ei.egValue -= Sign[us] * TrappedBishopA7H7Penalty;
1074 // evaluate_trapped_bishop_a1h1() determines whether a bishop on a1/h1
1075 // (a8/h8 for black) is trapped by a friendly pawn on b2/g2 (b7/g7 for
1076 // black), and assigns a penalty if it is. This pattern can obviously
1077 // only occur in Chess960 games.
1079 void evaluate_trapped_bishop_a1h1(const Position &pos, Square s, Color us,
1081 Piece pawn = pawn_of_color(us);
1085 assert(square_is_ok(s));
1086 assert(pos.piece_on(s) == bishop_of_color(us));
1088 if(square_file(s) == FILE_A) {
1089 b2 = relative_square(us, SQ_B2);
1090 b3 = relative_square(us, SQ_B3);
1091 c3 = relative_square(us, SQ_C3);
1094 b2 = relative_square(us, SQ_G2);
1095 b3 = relative_square(us, SQ_G3);
1096 c3 = relative_square(us, SQ_F3);
1099 if(pos.piece_on(b2) == pawn) {
1102 if(!pos.square_is_empty(b3))
1103 penalty = 2*TrappedBishopA1H1Penalty;
1104 else if(pos.piece_on(c3) == pawn)
1105 penalty = TrappedBishopA1H1Penalty;
1107 penalty = TrappedBishopA1H1Penalty / 2;
1109 ei.mgValue -= Sign[us] * penalty;
1110 ei.egValue -= Sign[us] * penalty;
1116 // evaluate_space() computes the space evaluation for a given side. The
1117 // space evaluation is a simple bonus based on the number of safe squares
1118 // available for minor pieces on the central four files on ranks 2--4. Safe
1119 // squares one, two or three squares behind a friendly pawn are counted
1120 // twice. Finally, the space bonus is scaled by a weight taken from the
1121 // material hash table.
1123 void evaluate_space(const Position &pos, Color us, EvalInfo &ei) {
1125 Color them = opposite_color(us);
1127 // Find the safe squares for our pieces inside the area defined by
1128 // SpaceMask[us]. A square is unsafe it is attacked by an enemy
1129 // pawn, or if it is undefended and attacked by an enemy piece.
1131 Bitboard safeSquares =
1132 SpaceMask[us] & ~pos.pawns(us) & ~ei.attacked_by(them, PAWN)
1133 & ~(~ei.attacked_by(us) & ei.attacked_by(them));
1135 // Find all squares which are at most three squares behind some friendly
1137 Bitboard behindFriendlyPawns = pos.pawns(us);
1139 behindFriendlyPawns |= (behindFriendlyPawns >> 8);
1140 behindFriendlyPawns |= (behindFriendlyPawns >> 16);
1143 behindFriendlyPawns |= (behindFriendlyPawns << 8);
1144 behindFriendlyPawns |= (behindFriendlyPawns << 16);
1148 count_1s_max_15(safeSquares)
1149 + count_1s_max_15(behindFriendlyPawns & safeSquares);
1151 ei.mgValue += Sign[us] *
1152 apply_weight(Value(space * ei.mi->space_weight()), WeightSpace);
1156 // apply_weight() applies an evaluation weight to a value
1158 inline Value apply_weight(Value v, int w) {
1159 return (v*w) / 0x100;
1163 // scale_by_game_phase() interpolates between a middle game and an endgame
1164 // score, based on game phase. It also scales the return value by a
1165 // ScaleFactor array.
1167 Value scale_by_game_phase(Value mv, Value ev, Phase ph, const ScaleFactor sf[]) {
1169 assert(mv > -VALUE_INFINITE && mv < VALUE_INFINITE);
1170 assert(ev > -VALUE_INFINITE && ev < VALUE_INFINITE);
1171 assert(ph >= PHASE_ENDGAME && ph <= PHASE_MIDGAME);
1173 ev = apply_scale_factor(ev, sf[(ev > Value(0) ? WHITE : BLACK)]);
1175 Value result = Value(int((mv * ph + ev * (128 - ph)) / 128));
1176 return Value(int(result) & ~(GrainSize - 1));
1180 // count_1s_8bit() counts the number of nonzero bits in the 8 least
1181 // significant bits of a Bitboard. This function is used by the king
1182 // shield evaluation.
1184 int count_1s_8bit(Bitboard b) {
1185 return int(BitCount8Bit[b & 0xFF]);
1189 // compute_weight() computes the value of an evaluation weight, by combining
1190 // an UCI-configurable weight with an internal weight.
1192 int compute_weight(int uciWeight, int internalWeight) {
1193 uciWeight = (uciWeight * 0x100) / 100;
1194 return (uciWeight * internalWeight) / 0x100;
1198 // helper used in read_weights()
1199 int weight_option(const std::string& opt, int weight) {
1201 return compute_weight(get_option_value_int(opt), weight);
1205 // init_safety() initizes the king safety evaluation, based on UCI
1206 // parameters. It is called from read_weights().
1208 void init_safety() {
1210 QueenContactCheckBonus = get_option_value_int("Queen Contact Check Bonus");
1211 QueenCheckBonus = get_option_value_int("Queen Check Bonus");
1212 RookCheckBonus = get_option_value_int("Rook Check Bonus");
1213 BishopCheckBonus = get_option_value_int("Bishop Check Bonus");
1214 KnightCheckBonus = get_option_value_int("Knight Check Bonus");
1215 DiscoveredCheckBonus = get_option_value_int("Discovered Check Bonus");
1216 MateThreatBonus = get_option_value_int("Mate Threat Bonus");
1218 int maxSlope = get_option_value_int("King Safety Max Slope");
1219 int peak = get_option_value_int("King Safety Max Value") * 256 / 100;
1220 double a = get_option_value_int("King Safety Coefficient") / 100.0;
1221 double b = get_option_value_int("King Safety X Intercept");
1222 bool quad = (get_option_value_string("King Safety Curve") == "Quadratic");
1223 bool linear = (get_option_value_string("King Safety Curve") == "Linear");
1225 for (int i = 0; i < 100; i++)
1228 SafetyTable[i] = Value(0);
1230 SafetyTable[i] = Value((int)(a * (i - b) * (i - b)));
1232 SafetyTable[i] = Value((int)(100 * a * (i - b)));
1235 for (int i = 0; i < 100; i++)
1237 if (SafetyTable[i+1] - SafetyTable[i] > maxSlope)
1238 for (int j = i + 1; j < 100; j++)
1239 SafetyTable[j] = SafetyTable[j-1] + Value(maxSlope);
1241 if (SafetyTable[i] > Value(peak))
1242 SafetyTable[i] = Value(peak);