2 Stockfish, a UCI chess playing engine derived from Glaurung 2.1
3 Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
4 Copyright (C) 2008-2010 Marco Costalba, Joona Kiiski, Tord Romstad
6 Stockfish is free software: you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation, either version 3 of the License, or
9 (at your option) any later version.
11 Stockfish is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
16 You should have received a copy of the GNU General Public License
17 along with this program. If not, see <http://www.gnu.org/licenses/>.
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 = 8;
47 // Evaluation weights, initialized from UCI options
48 enum { Mobility, PawnStructure, PassedPawns, Space, KingDangerUs, KingDangerThem };
52 #define S(mg, eg) make_score(mg, eg)
54 // Internal evaluation weights. These are applied on top of the evaluation
55 // weights read from UCI parameters. The purpose is to be able to change
56 // the evaluation weights while keeping the default values of the UCI
57 // parameters at 100, which looks prettier.
59 // Values modified by Joona Kiiski
60 const Score WeightsInternal[] = {
61 S(248, 271), S(233, 201), S(252, 259), S(46, 0), S(247, 0), S(259, 0)
64 // Knight mobility bonus in middle game and endgame, indexed by the number
65 // of attacked squares not occupied by friendly piecess.
66 const Score KnightMobilityBonus[16] = {
67 S(-38,-33), S(-25,-23), S(-12,-13), S( 0,-3),
68 S( 12, 7), S( 25, 17), S( 31, 22), S(38, 27), S(38, 27)
71 // Bishop mobility bonus in middle game and endgame, indexed by the number
72 // of attacked squares not occupied by friendly pieces. X-ray attacks through
73 // queens are also included.
74 const Score BishopMobilityBonus[16] = {
75 S(-25,-30), S(-11,-16), S( 3, -2), S(17, 12),
76 S( 31, 26), S( 45, 40), S(57, 52), S(65, 60),
77 S( 71, 65), S( 74, 69), S(76, 71), S(78, 73),
78 S( 79, 74), S( 80, 75), S(81, 76), S(81, 76)
81 // Rook mobility bonus in middle game and endgame, indexed by the number
82 // of attacked squares not occupied by friendly pieces. X-ray attacks through
83 // queens and rooks are also included.
84 const Score RookMobilityBonus[16] = {
85 S(-20,-36), S(-14,-19), S(-8, -3), S(-2, 13),
86 S( 4, 29), S( 10, 46), S(14, 62), S(19, 79),
87 S( 23, 95), S( 26,106), S(27,111), S(28,114),
88 S( 29,116), S( 30,117), S(31,118), S(32,118)
91 // Queen mobility bonus in middle game and endgame, indexed by the number
92 // of attacked squares not occupied by friendly pieces.
93 const Score QueenMobilityBonus[32] = {
94 S(-10,-18), S(-8,-13), S(-6, -7), S(-3, -2), S(-1, 3), S( 1, 8),
95 S( 3, 13), S( 5, 19), S( 8, 23), S(10, 27), S(12, 32), S(15, 34),
96 S( 16, 35), S(17, 35), S(18, 35), S(20, 35), S(20, 35), S(20, 35),
97 S( 20, 35), S(20, 35), S(20, 35), S(20, 35), S(20, 35), S(20, 35),
98 S( 20, 35), S(20, 35), S(20, 35), S(20, 35), S(20, 35), S(20, 35),
102 // Pointers table to access mobility tables through piece type
103 const Score* MobilityBonus[8] = { 0, 0, KnightMobilityBonus, BishopMobilityBonus,
104 RookMobilityBonus, QueenMobilityBonus, 0, 0 };
106 // Outpost bonuses for knights and bishops, indexed by square (from white's
108 const Value KnightOutpostBonus[64] = {
110 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 1
111 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 2
112 V(0), V(0), V(4), V(8), V(8), V(4), V(0), V(0), // 3
113 V(0), V(4),V(17),V(26),V(26),V(17), V(4), V(0), // 4
114 V(0), V(8),V(26),V(35),V(35),V(26), V(8), V(0), // 5
115 V(0), V(4),V(17),V(17),V(17),V(17), V(4), V(0), // 6
116 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 7
117 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0) // 8
120 const Value BishopOutpostBonus[64] = {
122 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 1
123 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 2
124 V(0), V(0), V(5), V(5), V(5), V(5), V(0), V(0), // 3
125 V(0), V(5),V(10),V(10),V(10),V(10), V(5), V(0), // 4
126 V(0),V(10),V(21),V(21),V(21),V(21),V(10), V(0), // 5
127 V(0), V(5), V(8), V(8), V(8), V(8), V(5), V(0), // 6
128 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 7
129 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0) // 8
132 // ThreatBonus[attacking][attacked] contains bonus according to which
133 // piece type attacks which one.
134 const Score ThreatBonus[8][8] = {
136 { S(0, 0), S( 7, 39), S( 0, 0), S(24, 49), S(41,100), S(41,100) }, // KNIGHT
137 { S(0, 0), S( 7, 39), S(24, 49), S( 0, 0), S(41,100), S(41,100) }, // BISHOP
138 { S(0, 0), S(-1, 29), S(15, 49), S(15, 49), S( 0, 0), S(24, 49) }, // ROOK
139 { S(0, 0), S(15, 39), S(15, 39), S(15, 39), S(15, 39), S( 0, 0) } // QUEEN
142 // ThreatedByPawnPenalty[] contains a penalty according to which piece
143 // type is attacked by an enemy pawn.
144 const Score ThreatedByPawnPenalty[8] = {
145 S(0, 0), S(0, 0), S(56, 70), S(56, 70), S(76, 99), S(86, 118)
150 // Rooks and queens on the 7th rank (modified by Joona Kiiski)
151 const Score RookOn7thBonus = make_score(47, 98);
152 const Score QueenOn7thBonus = make_score(27, 54);
154 // Rooks on open files (modified by Joona Kiiski)
155 const Score RookOpenFileBonus = make_score(43, 43);
156 const Score RookHalfOpenFileBonus = make_score(19, 19);
158 // Penalty for rooks trapped inside a friendly king which has lost the
160 const Value TrappedRookPenalty = Value(180);
162 // The SpaceMask[color] contains the area of the board which is considered
163 // by the space evaluation. In the middle game, each side is given a bonus
164 // based on how many squares inside this area are safe and available for
165 // friendly minor pieces.
166 const Bitboard SpaceMask[2] = {
167 (1ULL<<SQ_C2) | (1ULL<<SQ_D2) | (1ULL<<SQ_E2) | (1ULL<<SQ_F2) |
168 (1ULL<<SQ_C3) | (1ULL<<SQ_D3) | (1ULL<<SQ_E3) | (1ULL<<SQ_F3) |
169 (1ULL<<SQ_C4) | (1ULL<<SQ_D4) | (1ULL<<SQ_E4) | (1ULL<<SQ_F4),
170 (1ULL<<SQ_C7) | (1ULL<<SQ_D7) | (1ULL<<SQ_E7) | (1ULL<<SQ_F7) |
171 (1ULL<<SQ_C6) | (1ULL<<SQ_D6) | (1ULL<<SQ_E6) | (1ULL<<SQ_F6) |
172 (1ULL<<SQ_C5) | (1ULL<<SQ_D5) | (1ULL<<SQ_E5) | (1ULL<<SQ_F5)
175 /// King danger constants and variables. The king danger scores are taken
176 /// from the KingDangerTable[]. Various little "meta-bonuses" measuring
177 /// the strength of the enemy attack are added up into an integer, which
178 /// is used as an index to KingDangerTable[].
180 // KingAttackWeights[] contains king attack weights by piece type
181 const int KingAttackWeights[8] = { 0, 0, 2, 2, 3, 5 };
183 // Bonuses for enemy's safe checks
184 const int QueenContactCheckBonus = 3;
185 const int QueenCheckBonus = 2;
186 const int RookCheckBonus = 1;
187 const int BishopCheckBonus = 1;
188 const int KnightCheckBonus = 1;
190 // InitKingDanger[] contains bonuses based on the position of the defending
192 const int InitKingDanger[64] = {
193 2, 0, 2, 5, 5, 2, 0, 2,
194 2, 2, 4, 8, 8, 4, 2, 2,
195 7, 10, 12, 12, 12, 12, 10, 7,
196 15, 15, 15, 15, 15, 15, 15, 15,
197 15, 15, 15, 15, 15, 15, 15, 15,
198 15, 15, 15, 15, 15, 15, 15, 15,
199 15, 15, 15, 15, 15, 15, 15, 15,
200 15, 15, 15, 15, 15, 15, 15, 15
203 // KingDangerTable[color][] contains the actual king danger weighted scores
204 Score KingDangerTable[2][128];
206 // Pawn and material hash tables, indexed by the current thread id.
207 // Note that they will be initialized at 0 being global variables.
208 MaterialInfoTable* MaterialTable[MAX_THREADS];
209 PawnInfoTable* PawnTable[MAX_THREADS];
211 // Function prototypes
212 template<bool HasPopCnt>
213 Value do_evaluate(const Position& pos, EvalInfo& ei);
215 template<Color Us, bool HasPopCnt>
216 void init_attack_tables(const Position& pos, EvalInfo& ei);
218 template<Color Us, bool HasPopCnt>
219 void evaluate_pieces_of_color(const Position& pos, EvalInfo& ei);
221 template<Color Us, bool HasPopCnt>
222 void evaluate_king(const Position& pos, EvalInfo& ei);
225 void evaluate_threats(const Position& pos, EvalInfo& ei);
227 template<Color Us, bool HasPopCnt>
228 int evaluate_space(const Position& pos, EvalInfo& ei);
231 void evaluate_passed_pawns(const Position& pos, EvalInfo& ei);
233 inline Score apply_weight(Score v, Score weight);
234 Value scale_by_game_phase(const Score& v, Phase ph, const ScaleFactor sf[]);
235 Score weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight);
245 /// Prefetches in pawn hash tables
247 void prefetchPawn(Key key, int threadID) {
249 PawnTable[threadID]->prefetch(key);
252 /// evaluate() is the main evaluation function. It always computes two
253 /// values, an endgame score and a middle game score, and interpolates
254 /// between them based on the remaining material.
255 Value evaluate(const Position& pos, EvalInfo& ei) {
257 return CpuHasPOPCNT ? do_evaluate<true>(pos, ei)
258 : do_evaluate<false>(pos, ei);
263 template<bool HasPopCnt>
264 Value do_evaluate(const Position& pos, EvalInfo& ei) {
266 ScaleFactor factor[2];
269 assert(pos.thread() >= 0 && pos.thread() < MAX_THREADS);
270 assert(!pos.is_check());
272 memset(&ei, 0, sizeof(EvalInfo));
274 // Initialize by reading the incrementally updated scores included in the
275 // position object (material + piece square tables)
276 ei.value = pos.value();
278 // Probe the material hash table
279 ei.mi = MaterialTable[pos.thread()]->get_material_info(pos);
280 ei.value += ei.mi->material_value();
282 // If we have a specialized evaluation function for the current material
283 // configuration, call it and return
284 if (ei.mi->specialized_eval_exists())
285 return ei.mi->evaluate(pos);
287 // After get_material_info() call that modifies them
288 factor[WHITE] = ei.mi->scale_factor(pos, WHITE);
289 factor[BLACK] = ei.mi->scale_factor(pos, BLACK);
291 // Probe the pawn hash table
292 ei.pi = PawnTable[pos.thread()]->get_pawn_info(pos);
293 ei.value += apply_weight(ei.pi->pawns_value(), Weights[PawnStructure]);
295 // Initialize attack bitboards with pawns evaluation
296 init_attack_tables<WHITE, HasPopCnt>(pos, ei);
297 init_attack_tables<BLACK, HasPopCnt>(pos, ei);
300 evaluate_pieces_of_color<WHITE, HasPopCnt>(pos, ei);
301 evaluate_pieces_of_color<BLACK, HasPopCnt>(pos, ei);
303 // Kings. Kings are evaluated after all other pieces for both sides,
304 // because we need complete attack information for all pieces when computing
305 // the king safety evaluation.
306 evaluate_king<WHITE, HasPopCnt>(pos, ei);
307 evaluate_king<BLACK, HasPopCnt>(pos, ei);
309 // Evaluate tactical threats, we need full attack info including king
310 evaluate_threats<WHITE>(pos, ei);
311 evaluate_threats<BLACK>(pos, ei);
313 // Evaluate passed pawns, we need full attack info including king
314 evaluate_passed_pawns<WHITE>(pos, ei);
315 evaluate_passed_pawns<BLACK>(pos, ei);
317 Phase phase = ei.mi->game_phase();
319 // Middle-game specific evaluation terms
320 if (phase > PHASE_ENDGAME)
322 // Pawn storms in positions with opposite castling
323 if ( square_file(pos.king_square(WHITE)) >= FILE_E
324 && square_file(pos.king_square(BLACK)) <= FILE_D)
326 ei.value += make_score(ei.pi->queenside_storm_value(WHITE) - ei.pi->kingside_storm_value(BLACK), 0);
328 else if ( square_file(pos.king_square(WHITE)) <= FILE_D
329 && square_file(pos.king_square(BLACK)) >= FILE_E)
331 ei.value += make_score(ei.pi->kingside_storm_value(WHITE) - ei.pi->queenside_storm_value(BLACK), 0);
333 // Evaluate space for both sides
334 if (ei.mi->space_weight() > 0)
336 int s = evaluate_space<WHITE, HasPopCnt>(pos, ei) - evaluate_space<BLACK, HasPopCnt>(pos, ei);
337 ei.value += apply_weight(make_score(s * ei.mi->space_weight(), 0), Weights[Space]);
342 ei.value += apply_weight(ei.mobility, Weights[Mobility]);
344 // If we don't already have an unusual scale factor, check for opposite
345 // colored bishop endgames, and use a lower scale for those
346 if ( phase < PHASE_MIDGAME
347 && pos.opposite_colored_bishops()
348 && ( (factor[WHITE] == SCALE_FACTOR_NORMAL && eg_value(ei.value) > VALUE_ZERO)
349 || (factor[BLACK] == SCALE_FACTOR_NORMAL && eg_value(ei.value) < VALUE_ZERO)))
353 // Only the two bishops ?
354 if ( pos.non_pawn_material(WHITE) == BishopValueMidgame
355 && pos.non_pawn_material(BLACK) == BishopValueMidgame)
357 // Check for KBP vs KB with only a single pawn that is almost
358 // certainly a draw or at least two pawns.
359 bool one_pawn = (pos.piece_count(WHITE, PAWN) + pos.piece_count(BLACK, PAWN) == 1);
360 sf = one_pawn ? ScaleFactor(8) : ScaleFactor(32);
363 // Endgame with opposite-colored bishops, but also other pieces. Still
364 // a bit drawish, but not as drawish as with only the two bishops.
365 sf = ScaleFactor(50);
367 if (factor[WHITE] == SCALE_FACTOR_NORMAL)
369 if (factor[BLACK] == SCALE_FACTOR_NORMAL)
373 // Interpolate between the middle game and the endgame score
374 return Sign[pos.side_to_move()] * scale_by_game_phase(ei.value, phase, factor);
379 /// init_eval() initializes various tables used by the evaluation function
381 void init_eval(int threads) {
383 assert(threads <= MAX_THREADS);
385 for (int i = 0; i < MAX_THREADS; i++)
390 delete MaterialTable[i];
392 MaterialTable[i] = NULL;
396 PawnTable[i] = new PawnInfoTable();
397 if (!MaterialTable[i])
398 MaterialTable[i] = new MaterialInfoTable();
403 /// quit_eval() releases heap-allocated memory at program termination
407 for (int i = 0; i < MAX_THREADS; i++)
410 delete MaterialTable[i];
412 MaterialTable[i] = NULL;
417 /// read_weights() reads evaluation weights from the corresponding UCI parameters
419 void read_weights(Color us) {
421 // King safety is asymmetrical. Our king danger level is weighted by
422 // "Cowardice" UCI parameter, instead the opponent one by "Aggressiveness".
423 const int kingDangerUs = (us == WHITE ? KingDangerUs : KingDangerThem);
424 const int kingDangerThem = (us == WHITE ? KingDangerThem : KingDangerUs);
426 Weights[Mobility] = weight_option("Mobility (Middle Game)", "Mobility (Endgame)", WeightsInternal[Mobility]);
427 Weights[PawnStructure] = weight_option("Pawn Structure (Middle Game)", "Pawn Structure (Endgame)", WeightsInternal[PawnStructure]);
428 Weights[PassedPawns] = weight_option("Passed Pawns (Middle Game)", "Passed Pawns (Endgame)", WeightsInternal[PassedPawns]);
429 Weights[Space] = weight_option("Space", "Space", WeightsInternal[Space]);
430 Weights[kingDangerUs] = weight_option("Cowardice", "Cowardice", WeightsInternal[KingDangerUs]);
431 Weights[kingDangerThem] = weight_option("Aggressiveness", "Aggressiveness", WeightsInternal[KingDangerThem]);
433 // If running in analysis mode, make sure we use symmetrical king safety. We do this
434 // by replacing both Weights[kingDangerUs] and Weights[kingDangerThem] by their average.
435 if (get_option_value_bool("UCI_AnalyseMode"))
436 Weights[kingDangerUs] = Weights[kingDangerThem] = (Weights[kingDangerUs] + Weights[kingDangerThem]) / 2;
444 // init_attack_tables() initializes king bitboards for both sides adding
445 // pawn attacks. To be done before other evaluations.
447 template<Color Us, bool HasPopCnt>
448 void init_attack_tables(const Position& pos, EvalInfo& ei) {
450 const Color Them = (Us == WHITE ? BLACK : WHITE);
452 Bitboard b = ei.attackedBy[Them][KING] = pos.attacks_from<KING>(pos.king_square(Them));
453 ei.kingZone[Us] = (b | (Us == WHITE ? b >> 8 : b << 8));
454 ei.attackedBy[Us][PAWN] = ei.pi->pawn_attacks(Us);
455 b &= ei.attackedBy[Us][PAWN];
457 ei.kingAttackersCount[Us] = count_1s_max_15<HasPopCnt>(b) / 2;
461 // evaluate_outposts() evaluates bishop and knight outposts squares
463 template<PieceType Piece, Color Us>
464 void evaluate_outposts(const Position& pos, EvalInfo& ei, Square s) {
466 const Color Them = (Us == WHITE ? BLACK : WHITE);
468 // Initial bonus based on square
469 Value bonus = (Piece == BISHOP ? BishopOutpostBonus[relative_square(Us, s)]
470 : KnightOutpostBonus[relative_square(Us, s)]);
472 // Increase bonus if supported by pawn, especially if the opponent has
473 // no minor piece which can exchange the outpost piece
474 if (bonus && bit_is_set(ei.attackedBy[Us][PAWN], s))
476 if ( pos.pieces(KNIGHT, Them) == EmptyBoardBB
477 && (SquaresByColorBB[square_color(s)] & pos.pieces(BISHOP, Them)) == EmptyBoardBB)
478 bonus += bonus + bonus / 2;
482 ei.value += Sign[Us] * make_score(bonus, bonus);
486 // evaluate_pieces<>() assigns bonuses and penalties to the pieces of a given color
488 template<PieceType Piece, Color Us, bool HasPopCnt>
489 void evaluate_pieces(const Position& pos, EvalInfo& ei, Bitboard no_mob_area) {
496 const Color Them = (Us == WHITE ? BLACK : WHITE);
497 const Square* ptr = pos.piece_list_begin(Us, Piece);
499 while ((s = *ptr++) != SQ_NONE)
501 // Find attacked squares, including x-ray attacks for bishops and rooks
502 if (Piece == KNIGHT || Piece == QUEEN)
503 b = pos.attacks_from<Piece>(s);
504 else if (Piece == BISHOP)
505 b = bishop_attacks_bb(s, pos.occupied_squares() & ~pos.pieces(QUEEN, Us));
506 else if (Piece == ROOK)
507 b = rook_attacks_bb(s, pos.occupied_squares() & ~pos.pieces(ROOK, QUEEN, Us));
511 // Update attack info
512 ei.attackedBy[Us][Piece] |= b;
515 if (b & ei.kingZone[Us])
517 ei.kingAttackersCount[Us]++;
518 ei.kingAttackersWeight[Us] += KingAttackWeights[Piece];
519 Bitboard bb = (b & ei.attackedBy[Them][KING]);
521 ei.kingAdjacentZoneAttacksCount[Us] += count_1s_max_15<HasPopCnt>(bb);
525 mob = (Piece != QUEEN ? count_1s_max_15<HasPopCnt>(b & no_mob_area)
526 : count_1s<HasPopCnt>(b & no_mob_area));
528 ei.mobility += Sign[Us] * MobilityBonus[Piece][mob];
530 // Decrease score if we are attacked by an enemy pawn. Remaining part
531 // of threat evaluation must be done later when we have full attack info.
532 if (bit_is_set(ei.attackedBy[Them][PAWN], s))
533 ei.value -= Sign[Us] * ThreatedByPawnPenalty[Piece];
535 // Bishop and knight outposts squares
536 if ((Piece == BISHOP || Piece == KNIGHT) && pos.square_is_weak(s, Us))
537 evaluate_outposts<Piece, Us>(pos, ei, s);
539 // Queen or rook on 7th rank
540 if ( (Piece == ROOK || Piece == QUEEN)
541 && relative_rank(Us, s) == RANK_7
542 && relative_rank(Us, pos.king_square(Them)) == RANK_8)
544 ei.value += Sign[Us] * (Piece == ROOK ? RookOn7thBonus : QueenOn7thBonus);
547 // Special extra evaluation for rooks
550 // Open and half-open files
552 if (ei.pi->file_is_half_open(Us, f))
554 if (ei.pi->file_is_half_open(Them, f))
555 ei.value += Sign[Us] * RookOpenFileBonus;
557 ei.value += Sign[Us] * RookHalfOpenFileBonus;
560 // Penalize rooks which are trapped inside a king. Penalize more if
561 // king has lost right to castle.
562 if (mob > 6 || ei.pi->file_is_half_open(Us, f))
565 ksq = pos.king_square(Us);
567 if ( square_file(ksq) >= FILE_E
568 && square_file(s) > square_file(ksq)
569 && (relative_rank(Us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
571 // Is there a half-open file between the king and the edge of the board?
572 if (!ei.pi->has_open_file_to_right(Us, square_file(ksq)))
573 ei.value -= Sign[Us] * make_score(pos.can_castle(Us) ? (TrappedRookPenalty - mob * 16) / 2
574 : (TrappedRookPenalty - mob * 16), 0);
576 else if ( square_file(ksq) <= FILE_D
577 && square_file(s) < square_file(ksq)
578 && (relative_rank(Us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
580 // Is there a half-open file between the king and the edge of the board?
581 if (!ei.pi->has_open_file_to_left(Us, square_file(ksq)))
582 ei.value -= Sign[Us] * make_score(pos.can_castle(Us) ? (TrappedRookPenalty - mob * 16) / 2
583 : (TrappedRookPenalty - mob * 16), 0);
590 // evaluate_threats<>() assigns bonuses according to the type of attacking piece
591 // and the type of attacked one.
594 void evaluate_threats(const Position& pos, EvalInfo& ei) {
596 const Color Them = (Us == WHITE ? BLACK : WHITE);
599 Score bonus = SCORE_ZERO;
601 // Enemy pieces not defended by a pawn and under our attack
602 Bitboard weakEnemies = pos.pieces_of_color(Them)
603 & ~ei.attackedBy[Them][PAWN]
604 & ei.attackedBy[Us][0];
608 // Add bonus according to type of attacked enemy pieces and to the
609 // type of attacking piece, from knights to queens. Kings are not
610 // considered because are already special handled in king evaluation.
611 for (PieceType pt1 = KNIGHT; pt1 < KING; pt1++)
613 b = ei.attackedBy[Us][pt1] & weakEnemies;
615 for (PieceType pt2 = PAWN; pt2 < KING; pt2++)
616 if (b & pos.pieces(pt2))
617 bonus += ThreatBonus[pt1][pt2];
619 ei.value += Sign[Us] * bonus;
623 // evaluate_pieces_of_color<>() assigns bonuses and penalties to all the
624 // pieces of a given color.
626 template<Color Us, bool HasPopCnt>
627 void evaluate_pieces_of_color(const Position& pos, EvalInfo& ei) {
629 const Color Them = (Us == WHITE ? BLACK : WHITE);
631 // Do not include in mobility squares protected by enemy pawns or occupied by our pieces
632 const Bitboard no_mob_area = ~(ei.attackedBy[Them][PAWN] | pos.pieces_of_color(Us));
634 evaluate_pieces<KNIGHT, Us, HasPopCnt>(pos, ei, no_mob_area);
635 evaluate_pieces<BISHOP, Us, HasPopCnt>(pos, ei, no_mob_area);
636 evaluate_pieces<ROOK, Us, HasPopCnt>(pos, ei, no_mob_area);
637 evaluate_pieces<QUEEN, Us, HasPopCnt>(pos, ei, no_mob_area);
639 // Sum up all attacked squares
640 ei.attackedBy[Us][0] = ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
641 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
642 | ei.attackedBy[Us][QUEEN] | ei.attackedBy[Us][KING];
646 // evaluate_king<>() assigns bonuses and penalties to a king of a given color
648 template<Color Us, bool HasPopCnt>
649 void evaluate_king(const Position& pos, EvalInfo& ei) {
651 const Color Them = (Us == WHITE ? BLACK : WHITE);
653 Bitboard undefended, b, b1, b2, safe;
656 const Square ksq = pos.king_square(Us);
659 ei.value += Sign[Us] * ei.pi->king_shelter(pos, Us, ksq);
661 // King safety. This is quite complicated, and is almost certainly far
662 // from optimally tuned.
663 if ( pos.piece_count(Them, QUEEN) >= 1
664 && ei.kingAttackersCount[Them] >= 2
665 && pos.non_pawn_material(Them) >= QueenValueMidgame + RookValueMidgame
666 && ei.kingAdjacentZoneAttacksCount[Them])
668 // Is it the attackers turn to move?
669 sente = (Them == pos.side_to_move());
671 // Find the attacked squares around the king which has no defenders
672 // apart from the king itself
673 undefended = ei.attacked_by(Them) & ei.attacked_by(Us, KING);
674 undefended &= ~( ei.attacked_by(Us, PAWN) | ei.attacked_by(Us, KNIGHT)
675 | ei.attacked_by(Us, BISHOP) | ei.attacked_by(Us, ROOK)
676 | ei.attacked_by(Us, QUEEN));
678 // Initialize the 'attackUnits' variable, which is used later on as an
679 // index to the KingDangerTable[] array. The initial value is based on
680 // the number and types of the enemy's attacking pieces, the number of
681 // attacked and undefended squares around our king, the square of the
682 // king, and the quality of the pawn shelter.
683 attackUnits = Min(25, (ei.kingAttackersCount[Them] * ei.kingAttackersWeight[Them]) / 2)
684 + 3 * (ei.kingAdjacentZoneAttacksCount[Them] + count_1s_max_15<HasPopCnt>(undefended))
685 + InitKingDanger[relative_square(Us, ksq)]
686 - mg_value(ei.pi->king_shelter(pos, Us, ksq)) / 32;
688 // Analyse enemy's safe queen contact checks. First find undefended
689 // squares around the king attacked by enemy queen...
690 b = undefended & ei.attacked_by(Them, QUEEN) & ~pos.pieces_of_color(Them);
693 // ...then remove squares not supported by another enemy piece
694 b &= ( ei.attacked_by(Them, PAWN) | ei.attacked_by(Them, KNIGHT)
695 | ei.attacked_by(Them, BISHOP) | ei.attacked_by(Them, ROOK));
697 attackUnits += QueenContactCheckBonus * count_1s_max_15<HasPopCnt>(b) * (sente ? 2 : 1);
700 // Analyse enemy's safe distance checks for sliders and knights
701 safe = ~(pos.pieces_of_color(Them) | ei.attacked_by(Us));
703 b1 = pos.attacks_from<ROOK>(ksq) & safe;
704 b2 = pos.attacks_from<BISHOP>(ksq) & safe;
706 // Enemy queen safe checks
707 b = (b1 | b2) & ei.attacked_by(Them, QUEEN);
709 attackUnits += QueenCheckBonus * count_1s_max_15<HasPopCnt>(b);
711 // Enemy rooks safe checks
712 b = b1 & ei.attacked_by(Them, ROOK);
714 attackUnits += RookCheckBonus * count_1s_max_15<HasPopCnt>(b);
716 // Enemy bishops safe checks
717 b = b2 & ei.attacked_by(Them, BISHOP);
719 attackUnits += BishopCheckBonus * count_1s_max_15<HasPopCnt>(b);
721 // Enemy knights safe checks
722 b = pos.attacks_from<KNIGHT>(ksq) & ei.attacked_by(Them, KNIGHT) & safe;
724 attackUnits += KnightCheckBonus * count_1s_max_15<HasPopCnt>(b);
726 // To index KingDangerTable[] attackUnits must be in [0, 99] range
727 attackUnits = Min(99, Max(0, attackUnits));
729 // Finally, extract the king danger score from the KingDangerTable[]
730 // array and subtract the score from evaluation. Set also ei.kingDanger[]
731 // value that will be used for pruning because this value can sometimes
732 // be very big, and so capturing a single attacking piece can therefore
733 // result in a score change far bigger than the value of the captured piece.
734 ei.value -= Sign[Us] * KingDangerTable[Us][attackUnits];
735 ei.kingDanger[Us] = mg_value(KingDangerTable[Us][attackUnits]);
740 // evaluate_passed_pawns<>() evaluates the passed pawns of the given color
743 void evaluate_passed_pawns(const Position& pos, EvalInfo& ei) {
745 const Color Them = (Us == WHITE ? BLACK : WHITE);
747 Bitboard squaresToQueen, defendedSquares, unsafeSquares, supportingPawns;
748 Bitboard b = ei.pi->passed_pawns(Us);
752 Square s = pop_1st_bit(&b);
754 assert(pos.pawn_is_passed(Us, s));
756 int r = int(relative_rank(Us, s) - RANK_2);
757 int tr = r * (r - 1);
759 // Base bonus based on rank
760 Value mbonus = Value(20 * tr);
761 Value ebonus = Value(10 + r * r * 10);
765 Square blockSq = s + pawn_push(Us);
767 // Adjust bonus based on kings proximity
768 ebonus -= Value(square_distance(pos.king_square(Us), blockSq) * 3 * tr);
769 ebonus -= Value(square_distance(pos.king_square(Us), blockSq + pawn_push(Us)) * 1 * tr);
770 ebonus += Value(square_distance(pos.king_square(Them), blockSq) * 6 * tr);
772 // If the pawn is free to advance, increase bonus
773 if (pos.square_is_empty(blockSq))
775 squaresToQueen = squares_in_front_of(Us, s);
776 defendedSquares = squaresToQueen & ei.attacked_by(Us);
778 // If there is an enemy rook or queen attacking the pawn from behind,
779 // add all X-ray attacks by the rook or queen. Otherwise consider only
780 // the squares in the pawn's path attacked or occupied by the enemy.
781 if ( (squares_behind(Us, s) & pos.pieces(ROOK, QUEEN, Them))
782 && (squares_behind(Us, s) & pos.pieces(ROOK, QUEEN, Them) & pos.attacks_from<ROOK>(s)))
783 unsafeSquares = squaresToQueen;
785 unsafeSquares = squaresToQueen & (ei.attacked_by(Them) | pos.pieces_of_color(Them));
787 // If there aren't enemy attacks or pieces along the path to queen give
788 // huge bonus. Even bigger if we protect the pawn's path.
790 ebonus += Value(tr * (squaresToQueen == defendedSquares ? 17 : 15));
792 // OK, there are enemy attacks or pieces (but not pawns). Are those
793 // squares which are attacked by the enemy also attacked by us ?
794 // If yes, big bonus (but smaller than when there are no enemy attacks),
795 // if no, somewhat smaller bonus.
796 ebonus += Value(tr * ((unsafeSquares & defendedSquares) == unsafeSquares ? 13 : 8));
798 // At last, add a small bonus when there are no *friendly* pieces
799 // in the pawn's path.
800 if (!(squaresToQueen & pos.pieces_of_color(Us)))
805 // Increase the bonus if the passed pawn is supported by a friendly pawn
806 // on the same rank and a bit smaller if it's on the previous rank.
807 supportingPawns = pos.pieces(PAWN, Us) & neighboring_files_bb(s);
808 if (supportingPawns & rank_bb(s))
809 ebonus += Value(r * 20);
810 else if (supportingPawns & rank_bb(s - pawn_push(Us)))
811 ebonus += Value(r * 12);
813 // Rook pawns are a special case: They are sometimes worse, and
814 // sometimes better than other passed pawns. It is difficult to find
815 // good rules for determining whether they are good or bad. For now,
816 // we try the following: Increase the value for rook pawns if the
817 // other side has no pieces apart from a knight, and decrease the
818 // value if the other side has a rook or queen.
819 if (square_file(s) == FILE_A || square_file(s) == FILE_H)
821 if (pos.non_pawn_material(Them) <= KnightValueMidgame)
822 ebonus += ebonus / 4;
823 else if (pos.pieces(ROOK, QUEEN, Them))
824 ebonus -= ebonus / 4;
827 // Add the scores for this pawn to the middle game and endgame eval
828 ei.value += Sign[Us] * apply_weight(make_score(mbonus, ebonus), Weights[PassedPawns]);
834 // evaluate_space() computes the space evaluation for a given side. The
835 // space evaluation is a simple bonus based on the number of safe squares
836 // available for minor pieces on the central four files on ranks 2--4. Safe
837 // squares one, two or three squares behind a friendly pawn are counted
838 // twice. Finally, the space bonus is scaled by a weight taken from the
839 // material hash table.
840 template<Color Us, bool HasPopCnt>
841 int evaluate_space(const Position& pos, EvalInfo& ei) {
843 const Color Them = (Us == WHITE ? BLACK : WHITE);
845 // Find the safe squares for our pieces inside the area defined by
846 // SpaceMask[us]. A square is unsafe if it is attacked by an enemy
847 // pawn, or if it is undefended and attacked by an enemy piece.
848 Bitboard safe = SpaceMask[Us]
849 & ~pos.pieces(PAWN, Us)
850 & ~ei.attacked_by(Them, PAWN)
851 & (ei.attacked_by(Us) | ~ei.attacked_by(Them));
853 // Find all squares which are at most three squares behind some friendly pawn
854 Bitboard behind = pos.pieces(PAWN, Us);
855 behind |= (Us == WHITE ? behind >> 8 : behind << 8);
856 behind |= (Us == WHITE ? behind >> 16 : behind << 16);
858 return count_1s_max_15<HasPopCnt>(safe) + count_1s_max_15<HasPopCnt>(behind & safe);
862 // apply_weight() applies an evaluation weight to a value trying to prevent overflow
864 inline Score apply_weight(Score v, Score w) {
865 return make_score((int(mg_value(v)) * mg_value(w)) / 0x100, (int(eg_value(v)) * eg_value(w)) / 0x100);
869 // scale_by_game_phase() interpolates between a middle game and an endgame score,
870 // based on game phase. It also scales the return value by a ScaleFactor array.
872 Value scale_by_game_phase(const Score& v, Phase ph, const ScaleFactor sf[]) {
874 assert(mg_value(v) > -VALUE_INFINITE && mg_value(v) < VALUE_INFINITE);
875 assert(eg_value(v) > -VALUE_INFINITE && eg_value(v) < VALUE_INFINITE);
876 assert(ph >= PHASE_ENDGAME && ph <= PHASE_MIDGAME);
878 Value eg = eg_value(v);
879 ScaleFactor f = sf[eg > VALUE_ZERO ? WHITE : BLACK];
880 Value ev = Value((eg * int(f)) / SCALE_FACTOR_NORMAL);
882 int result = (mg_value(v) * int(ph) + ev * int(128 - ph)) / 128;
883 return Value(result & ~(GrainSize - 1));
887 // weight_option() computes the value of an evaluation weight, by combining
888 // two UCI-configurable weights (midgame and endgame) with an internal weight.
890 Score weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight) {
892 // Scale option value from 100 to 256
893 int mg = get_option_value_int(mgOpt) * 256 / 100;
894 int eg = get_option_value_int(egOpt) * 256 / 100;
896 return apply_weight(make_score(mg, eg), internalWeight);
899 // init_safety() initizes the king safety evaluation, based on UCI
900 // parameters. It is called from read_weights().
904 const Value MaxSlope = Value(30);
905 const Value Peak = Value(1280);
908 // First setup the base table
909 for (int i = 0; i < 100; i++)
911 t[i] = Value(int(0.4 * i * i));
914 t[i] = Min(t[i], t[i - 1] + MaxSlope);
916 t[i] = Min(t[i], Peak);
919 // Then apply the weights and get the final KingDangerTable[] array
920 for (Color c = WHITE; c <= BLACK; c++)
921 for (int i = 0; i < 100; i++)
922 KingDangerTable[c][i] = apply_weight(make_score(t[i], 0), Weights[KingDangerUs + c]);