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 // Pieces mobility bonus in middle game and endgame, indexed by piece type
65 // and number of attacked squares not occupied by friendly pieces.
66 const Score MobilityBonus[][32] = {
68 { S(-38,-33), S(-25,-23), S(-12,-13), S( 0, -3), S(12, 7), S(25, 17), // Knights
69 S( 31, 22), S( 38, 27), S( 38, 27) },
70 { S(-25,-30), S(-11,-16), S( 3, -2), S(17, 12), S(31, 26), S(45, 40), // Bishops
71 S( 57, 52), S( 65, 60), S( 71, 65), S(74, 69), S(76, 71), S(78, 73),
72 S( 79, 74), S( 80, 75), S( 81, 76), S(81, 76) },
73 { S(-20,-36), S(-14,-19), S( -8, -3), S(-2, 13), S( 4, 29), S(10, 46), // Rooks
74 S( 14, 62), S( 19, 79), S( 23, 95), S(26,106), S(27,111), S(28,114),
75 S( 29,116), S( 30,117), S( 31,118), S(32,118) },
76 { S(-10,-18), S( -8,-13), S( -6, -7), S(-3, -2), S(-1, 3), S( 1, 8), // Queens
77 S( 3, 13), S( 5, 19), S( 8, 23), S(10, 27), S(12, 32), S(15, 34),
78 S( 16, 35), S( 17, 35), S( 18, 35), S(20, 35), S(20, 35), S(20, 35),
79 S( 20, 35), S( 20, 35), S( 20, 35), S(20, 35), S(20, 35), S(20, 35),
80 S( 20, 35), S( 20, 35), S( 20, 35), S(20, 35), S(20, 35), S(20, 35),
81 S( 20, 35), S( 20, 35) }
84 // Outpost bonuses for knights and bishops, indexed by square (from white's
86 const Value OutpostBonus[][64] = {
89 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // Knights
90 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0),
91 V(0), V(0), V(4), V(8), V(8), V(4), V(0), V(0),
92 V(0), V(4),V(17),V(26),V(26),V(17), V(4), V(0),
93 V(0), V(8),V(26),V(35),V(35),V(26), V(8), V(0),
94 V(0), V(4),V(17),V(17),V(17),V(17), V(4), V(0),
95 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0),
96 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0) },
98 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // Bishops
99 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0),
100 V(0), V(0), V(5), V(5), V(5), V(5), V(0), V(0),
101 V(0), V(5),V(10),V(10),V(10),V(10), V(5), V(0),
102 V(0),V(10),V(21),V(21),V(21),V(21),V(10), V(0),
103 V(0), V(5), V(8), V(8), V(8), V(8), V(5), V(0),
104 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0),
105 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0) }
108 // ThreatBonus[attacking][attacked] contains bonus according to which
109 // piece type attacks which one.
110 const Score ThreatBonus[8][8] = {
112 { S(0, 0), S( 7, 39), S( 0, 0), S(24, 49), S(41,100), S(41,100) }, // KNIGHT
113 { S(0, 0), S( 7, 39), S(24, 49), S( 0, 0), S(41,100), S(41,100) }, // BISHOP
114 { S(0, 0), S(-1, 29), S(15, 49), S(15, 49), S( 0, 0), S(24, 49) }, // ROOK
115 { S(0, 0), S(15, 39), S(15, 39), S(15, 39), S(15, 39), S( 0, 0) } // QUEEN
118 // ThreatedByPawnPenalty[] contains a penalty according to which piece
119 // type is attacked by an enemy pawn.
120 const Score ThreatedByPawnPenalty[8] = {
121 S(0, 0), S(0, 0), S(56, 70), S(56, 70), S(76, 99), S(86, 118)
126 // Rooks and queens on the 7th rank (modified by Joona Kiiski)
127 const Score RookOn7thBonus = make_score(47, 98);
128 const Score QueenOn7thBonus = make_score(27, 54);
130 // Rooks on open files (modified by Joona Kiiski)
131 const Score RookOpenFileBonus = make_score(43, 43);
132 const Score RookHalfOpenFileBonus = make_score(19, 19);
134 // Penalty for rooks trapped inside a friendly king which has lost the
136 const Value TrappedRookPenalty = Value(180);
138 // The SpaceMask[color] contains the area of the board which is considered
139 // by the space evaluation. In the middle game, each side is given a bonus
140 // based on how many squares inside this area are safe and available for
141 // friendly minor pieces.
142 const Bitboard SpaceMask[2] = {
143 (1ULL<<SQ_C2) | (1ULL<<SQ_D2) | (1ULL<<SQ_E2) | (1ULL<<SQ_F2) |
144 (1ULL<<SQ_C3) | (1ULL<<SQ_D3) | (1ULL<<SQ_E3) | (1ULL<<SQ_F3) |
145 (1ULL<<SQ_C4) | (1ULL<<SQ_D4) | (1ULL<<SQ_E4) | (1ULL<<SQ_F4),
146 (1ULL<<SQ_C7) | (1ULL<<SQ_D7) | (1ULL<<SQ_E7) | (1ULL<<SQ_F7) |
147 (1ULL<<SQ_C6) | (1ULL<<SQ_D6) | (1ULL<<SQ_E6) | (1ULL<<SQ_F6) |
148 (1ULL<<SQ_C5) | (1ULL<<SQ_D5) | (1ULL<<SQ_E5) | (1ULL<<SQ_F5)
151 /// King danger constants and variables. The king danger scores are taken
152 /// from the KingDangerTable[]. Various little "meta-bonuses" measuring
153 /// the strength of the enemy attack are added up into an integer, which
154 /// is used as an index to KingDangerTable[].
156 // KingAttackWeights[] contains king attack weights by piece type
157 const int KingAttackWeights[8] = { 0, 0, 2, 2, 3, 5 };
159 // Bonuses for enemy's safe checks
160 const int QueenContactCheckBonus = 3;
161 const int QueenCheckBonus = 2;
162 const int RookCheckBonus = 1;
163 const int BishopCheckBonus = 1;
164 const int KnightCheckBonus = 1;
166 // InitKingDanger[] contains bonuses based on the position of the defending
168 const int InitKingDanger[64] = {
169 2, 0, 2, 5, 5, 2, 0, 2,
170 2, 2, 4, 8, 8, 4, 2, 2,
171 7, 10, 12, 12, 12, 12, 10, 7,
172 15, 15, 15, 15, 15, 15, 15, 15,
173 15, 15, 15, 15, 15, 15, 15, 15,
174 15, 15, 15, 15, 15, 15, 15, 15,
175 15, 15, 15, 15, 15, 15, 15, 15,
176 15, 15, 15, 15, 15, 15, 15, 15
179 // KingDangerTable[color][] contains the actual king danger weighted scores
180 Score KingDangerTable[2][128];
182 // Pawn and material hash tables, indexed by the current thread id.
183 // Note that they will be initialized at 0 being global variables.
184 MaterialInfoTable* MaterialTable[MAX_THREADS];
185 PawnInfoTable* PawnTable[MAX_THREADS];
187 // Function prototypes
188 template<bool HasPopCnt>
189 Value do_evaluate(const Position& pos, EvalInfo& ei);
191 template<Color Us, bool HasPopCnt>
192 void init_attack_tables(const Position& pos, EvalInfo& ei);
194 template<Color Us, bool HasPopCnt>
195 void evaluate_pieces_of_color(const Position& pos, EvalInfo& ei);
197 template<Color Us, bool HasPopCnt>
198 void evaluate_king(const Position& pos, EvalInfo& ei);
201 void evaluate_threats(const Position& pos, EvalInfo& ei);
203 template<Color Us, bool HasPopCnt>
204 int evaluate_space(const Position& pos, EvalInfo& ei);
207 void evaluate_passed_pawns(const Position& pos, EvalInfo& ei);
209 inline Score apply_weight(Score v, Score weight);
210 Value scale_by_game_phase(const Score& v, Phase ph, const ScaleFactor sf[]);
211 Score weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight);
221 /// Prefetches in pawn hash tables
223 void prefetchPawn(Key key, int threadID) {
225 PawnTable[threadID]->prefetch(key);
228 /// evaluate() is the main evaluation function. It always computes two
229 /// values, an endgame score and a middle game score, and interpolates
230 /// between them based on the remaining material.
231 Value evaluate(const Position& pos, EvalInfo& ei) {
233 return CpuHasPOPCNT ? do_evaluate<true>(pos, ei)
234 : do_evaluate<false>(pos, ei);
239 template<bool HasPopCnt>
240 Value do_evaluate(const Position& pos, EvalInfo& ei) {
242 ScaleFactor factor[2];
245 assert(pos.thread() >= 0 && pos.thread() < MAX_THREADS);
246 assert(!pos.is_check());
248 memset(&ei, 0, sizeof(EvalInfo));
250 // Initialize by reading the incrementally updated scores included in the
251 // position object (material + piece square tables)
252 ei.value = pos.value();
254 // Probe the material hash table
255 ei.mi = MaterialTable[pos.thread()]->get_material_info(pos);
256 ei.value += ei.mi->material_value();
258 // If we have a specialized evaluation function for the current material
259 // configuration, call it and return
260 if (ei.mi->specialized_eval_exists())
261 return ei.mi->evaluate(pos);
263 // After get_material_info() call that modifies them
264 factor[WHITE] = ei.mi->scale_factor(pos, WHITE);
265 factor[BLACK] = ei.mi->scale_factor(pos, BLACK);
267 // Probe the pawn hash table
268 ei.pi = PawnTable[pos.thread()]->get_pawn_info(pos);
269 ei.value += apply_weight(ei.pi->pawns_value(), Weights[PawnStructure]);
271 // Initialize attack bitboards with pawns evaluation
272 init_attack_tables<WHITE, HasPopCnt>(pos, ei);
273 init_attack_tables<BLACK, HasPopCnt>(pos, ei);
276 evaluate_pieces_of_color<WHITE, HasPopCnt>(pos, ei);
277 evaluate_pieces_of_color<BLACK, HasPopCnt>(pos, ei);
279 // Kings. Kings are evaluated after all other pieces for both sides,
280 // because we need complete attack information for all pieces when computing
281 // the king safety evaluation.
282 evaluate_king<WHITE, HasPopCnt>(pos, ei);
283 evaluate_king<BLACK, HasPopCnt>(pos, ei);
285 // Evaluate tactical threats, we need full attack info including king
286 evaluate_threats<WHITE>(pos, ei);
287 evaluate_threats<BLACK>(pos, ei);
289 // Evaluate passed pawns, we need full attack info including king
290 evaluate_passed_pawns<WHITE>(pos, ei);
291 evaluate_passed_pawns<BLACK>(pos, ei);
293 Phase phase = ei.mi->game_phase();
295 // Middle-game specific evaluation terms
296 if (phase > PHASE_ENDGAME)
298 // Evaluate pawn storms in positions with opposite castling
299 if ( square_file(pos.king_square(WHITE)) >= FILE_E
300 && square_file(pos.king_square(BLACK)) <= FILE_D)
302 ei.value += make_score(ei.pi->queenside_storm_value(WHITE) - ei.pi->kingside_storm_value(BLACK), 0);
304 else if ( square_file(pos.king_square(WHITE)) <= FILE_D
305 && square_file(pos.king_square(BLACK)) >= FILE_E)
307 ei.value += make_score(ei.pi->kingside_storm_value(WHITE) - ei.pi->queenside_storm_value(BLACK), 0);
309 // Evaluate space for both sides
310 if (ei.mi->space_weight() > 0)
312 int s = evaluate_space<WHITE, HasPopCnt>(pos, ei) - evaluate_space<BLACK, HasPopCnt>(pos, ei);
313 ei.value += apply_weight(make_score(s * ei.mi->space_weight(), 0), Weights[Space]);
318 ei.value += apply_weight(ei.mobility, Weights[Mobility]);
320 // If we don't already have an unusual scale factor, check for opposite
321 // colored bishop endgames, and use a lower scale for those
322 if ( phase < PHASE_MIDGAME
323 && pos.opposite_colored_bishops()
324 && ( (factor[WHITE] == SCALE_FACTOR_NORMAL && eg_value(ei.value) > VALUE_ZERO)
325 || (factor[BLACK] == SCALE_FACTOR_NORMAL && eg_value(ei.value) < VALUE_ZERO)))
329 // Only the two bishops ?
330 if ( pos.non_pawn_material(WHITE) == BishopValueMidgame
331 && pos.non_pawn_material(BLACK) == BishopValueMidgame)
333 // Check for KBP vs KB with only a single pawn that is almost
334 // certainly a draw or at least two pawns.
335 bool one_pawn = (pos.piece_count(WHITE, PAWN) + pos.piece_count(BLACK, PAWN) == 1);
336 sf = one_pawn ? ScaleFactor(8) : ScaleFactor(32);
339 // Endgame with opposite-colored bishops, but also other pieces. Still
340 // a bit drawish, but not as drawish as with only the two bishops.
341 sf = ScaleFactor(50);
343 if (factor[WHITE] == SCALE_FACTOR_NORMAL)
345 if (factor[BLACK] == SCALE_FACTOR_NORMAL)
349 // Interpolate between the middle game and the endgame score
350 return Sign[pos.side_to_move()] * scale_by_game_phase(ei.value, phase, factor);
355 /// init_eval() initializes various tables used by the evaluation function
357 void init_eval(int threads) {
359 assert(threads <= MAX_THREADS);
361 for (int i = 0; i < MAX_THREADS; i++)
366 delete MaterialTable[i];
368 MaterialTable[i] = NULL;
372 PawnTable[i] = new PawnInfoTable();
373 if (!MaterialTable[i])
374 MaterialTable[i] = new MaterialInfoTable();
379 /// quit_eval() releases heap-allocated memory at program termination
383 for (int i = 0; i < MAX_THREADS; i++)
386 delete MaterialTable[i];
388 MaterialTable[i] = NULL;
393 /// read_weights() reads evaluation weights from the corresponding UCI parameters
395 void read_weights(Color us) {
397 // King safety is asymmetrical. Our king danger level is weighted by
398 // "Cowardice" UCI parameter, instead the opponent one by "Aggressiveness".
399 const int kingDangerUs = (us == WHITE ? KingDangerUs : KingDangerThem);
400 const int kingDangerThem = (us == WHITE ? KingDangerThem : KingDangerUs);
402 Weights[Mobility] = weight_option("Mobility (Middle Game)", "Mobility (Endgame)", WeightsInternal[Mobility]);
403 Weights[PawnStructure] = weight_option("Pawn Structure (Middle Game)", "Pawn Structure (Endgame)", WeightsInternal[PawnStructure]);
404 Weights[PassedPawns] = weight_option("Passed Pawns (Middle Game)", "Passed Pawns (Endgame)", WeightsInternal[PassedPawns]);
405 Weights[Space] = weight_option("Space", "Space", WeightsInternal[Space]);
406 Weights[kingDangerUs] = weight_option("Cowardice", "Cowardice", WeightsInternal[KingDangerUs]);
407 Weights[kingDangerThem] = weight_option("Aggressiveness", "Aggressiveness", WeightsInternal[KingDangerThem]);
409 // If running in analysis mode, make sure we use symmetrical king safety. We do this
410 // by replacing both Weights[kingDangerUs] and Weights[kingDangerThem] by their average.
411 if (get_option_value_bool("UCI_AnalyseMode"))
412 Weights[kingDangerUs] = Weights[kingDangerThem] = (Weights[kingDangerUs] + Weights[kingDangerThem]) / 2;
420 // init_attack_tables() initializes king bitboards for both sides adding
421 // pawn attacks. To be done before other evaluations.
423 template<Color Us, bool HasPopCnt>
424 void init_attack_tables(const Position& pos, EvalInfo& ei) {
426 const Color Them = (Us == WHITE ? BLACK : WHITE);
428 Bitboard b = ei.attackedBy[Them][KING] = pos.attacks_from<KING>(pos.king_square(Them));
429 ei.kingZone[Us] = (b | (Us == WHITE ? b >> 8 : b << 8));
430 ei.attackedBy[Us][PAWN] = ei.pi->pawn_attacks(Us);
431 b &= ei.attackedBy[Us][PAWN];
433 ei.kingAttackersCount[Us] = count_1s_max_15<HasPopCnt>(b) / 2;
437 // evaluate_outposts() evaluates bishop and knight outposts squares
439 template<PieceType Piece, Color Us>
440 void evaluate_outposts(const Position& pos, EvalInfo& ei, Square s) {
442 const Color Them = (Us == WHITE ? BLACK : WHITE);
444 assert (Piece == BISHOP || Piece == KNIGHT);
446 // Initial bonus based on square
447 Value bonus = OutpostBonus[Piece == BISHOP][relative_square(Us, s)];
449 // Increase bonus if supported by pawn, especially if the opponent has
450 // no minor piece which can exchange the outpost piece
451 if (bonus && bit_is_set(ei.attackedBy[Us][PAWN], s))
453 if ( pos.pieces(KNIGHT, Them) == EmptyBoardBB
454 && (SquaresByColorBB[square_color(s)] & pos.pieces(BISHOP, Them)) == EmptyBoardBB)
455 bonus += bonus + bonus / 2;
459 ei.value += Sign[Us] * make_score(bonus, bonus);
463 // evaluate_pieces<>() assigns bonuses and penalties to the pieces of a given color
465 template<PieceType Piece, Color Us, bool HasPopCnt>
466 void evaluate_pieces(const Position& pos, EvalInfo& ei, Bitboard no_mob_area) {
473 const Color Them = (Us == WHITE ? BLACK : WHITE);
474 const Square* ptr = pos.piece_list_begin(Us, Piece);
476 while ((s = *ptr++) != SQ_NONE)
478 // Find attacked squares, including x-ray attacks for bishops and rooks
479 if (Piece == KNIGHT || Piece == QUEEN)
480 b = pos.attacks_from<Piece>(s);
481 else if (Piece == BISHOP)
482 b = bishop_attacks_bb(s, pos.occupied_squares() & ~pos.pieces(QUEEN, Us));
483 else if (Piece == ROOK)
484 b = rook_attacks_bb(s, pos.occupied_squares() & ~pos.pieces(ROOK, QUEEN, Us));
488 // Update attack info
489 ei.attackedBy[Us][Piece] |= b;
492 if (b & ei.kingZone[Us])
494 ei.kingAttackersCount[Us]++;
495 ei.kingAttackersWeight[Us] += KingAttackWeights[Piece];
496 Bitboard bb = (b & ei.attackedBy[Them][KING]);
498 ei.kingAdjacentZoneAttacksCount[Us] += count_1s_max_15<HasPopCnt>(bb);
502 mob = (Piece != QUEEN ? count_1s_max_15<HasPopCnt>(b & no_mob_area)
503 : count_1s<HasPopCnt>(b & no_mob_area));
505 ei.mobility += Sign[Us] * MobilityBonus[Piece][mob];
507 // Decrease score if we are attacked by an enemy pawn. Remaining part
508 // of threat evaluation must be done later when we have full attack info.
509 if (bit_is_set(ei.attackedBy[Them][PAWN], s))
510 ei.value -= Sign[Us] * ThreatedByPawnPenalty[Piece];
512 // Bishop and knight outposts squares
513 if ((Piece == BISHOP || Piece == KNIGHT) && pos.square_is_weak(s, Us))
514 evaluate_outposts<Piece, Us>(pos, ei, s);
516 // Queen or rook on 7th rank
517 if ( (Piece == ROOK || Piece == QUEEN)
518 && relative_rank(Us, s) == RANK_7
519 && relative_rank(Us, pos.king_square(Them)) == RANK_8)
521 ei.value += Sign[Us] * (Piece == ROOK ? RookOn7thBonus : QueenOn7thBonus);
524 // Special extra evaluation for rooks
527 // Open and half-open files
529 if (ei.pi->file_is_half_open(Us, f))
531 if (ei.pi->file_is_half_open(Them, f))
532 ei.value += Sign[Us] * RookOpenFileBonus;
534 ei.value += Sign[Us] * RookHalfOpenFileBonus;
537 // Penalize rooks which are trapped inside a king. Penalize more if
538 // king has lost right to castle.
539 if (mob > 6 || ei.pi->file_is_half_open(Us, f))
542 ksq = pos.king_square(Us);
544 if ( square_file(ksq) >= FILE_E
545 && square_file(s) > square_file(ksq)
546 && (relative_rank(Us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
548 // Is there a half-open file between the king and the edge of the board?
549 if (!ei.pi->has_open_file_to_right(Us, square_file(ksq)))
550 ei.value -= Sign[Us] * make_score(pos.can_castle(Us) ? (TrappedRookPenalty - mob * 16) / 2
551 : (TrappedRookPenalty - mob * 16), 0);
553 else if ( square_file(ksq) <= FILE_D
554 && square_file(s) < square_file(ksq)
555 && (relative_rank(Us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
557 // Is there a half-open file between the king and the edge of the board?
558 if (!ei.pi->has_open_file_to_left(Us, square_file(ksq)))
559 ei.value -= Sign[Us] * make_score(pos.can_castle(Us) ? (TrappedRookPenalty - mob * 16) / 2
560 : (TrappedRookPenalty - mob * 16), 0);
567 // evaluate_threats<>() assigns bonuses according to the type of attacking piece
568 // and the type of attacked one.
571 void evaluate_threats(const Position& pos, EvalInfo& ei) {
573 const Color Them = (Us == WHITE ? BLACK : WHITE);
576 Score bonus = SCORE_ZERO;
578 // Enemy pieces not defended by a pawn and under our attack
579 Bitboard weakEnemies = pos.pieces_of_color(Them)
580 & ~ei.attackedBy[Them][PAWN]
581 & ei.attackedBy[Us][0];
585 // Add bonus according to type of attacked enemy pieces and to the
586 // type of attacking piece, from knights to queens. Kings are not
587 // considered because are already special handled in king evaluation.
588 for (PieceType pt1 = KNIGHT; pt1 < KING; pt1++)
590 b = ei.attackedBy[Us][pt1] & weakEnemies;
592 for (PieceType pt2 = PAWN; pt2 < KING; pt2++)
593 if (b & pos.pieces(pt2))
594 bonus += ThreatBonus[pt1][pt2];
596 ei.value += Sign[Us] * bonus;
600 // evaluate_pieces_of_color<>() assigns bonuses and penalties to all the
601 // pieces of a given color.
603 template<Color Us, bool HasPopCnt>
604 void evaluate_pieces_of_color(const Position& pos, EvalInfo& ei) {
606 const Color Them = (Us == WHITE ? BLACK : WHITE);
608 // Do not include in mobility squares protected by enemy pawns or occupied by our pieces
609 const Bitboard no_mob_area = ~(ei.attackedBy[Them][PAWN] | pos.pieces_of_color(Us));
611 evaluate_pieces<KNIGHT, Us, HasPopCnt>(pos, ei, no_mob_area);
612 evaluate_pieces<BISHOP, Us, HasPopCnt>(pos, ei, no_mob_area);
613 evaluate_pieces<ROOK, Us, HasPopCnt>(pos, ei, no_mob_area);
614 evaluate_pieces<QUEEN, Us, HasPopCnt>(pos, ei, no_mob_area);
616 // Sum up all attacked squares
617 ei.attackedBy[Us][0] = ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
618 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
619 | ei.attackedBy[Us][QUEEN] | ei.attackedBy[Us][KING];
623 // evaluate_king<>() assigns bonuses and penalties to a king of a given color
625 template<Color Us, bool HasPopCnt>
626 void evaluate_king(const Position& pos, EvalInfo& ei) {
628 const Color Them = (Us == WHITE ? BLACK : WHITE);
630 Bitboard undefended, b, b1, b2, safe;
633 const Square ksq = pos.king_square(Us);
636 ei.value += Sign[Us] * ei.pi->king_shelter(pos, Us, ksq);
638 // King safety. This is quite complicated, and is almost certainly far
639 // from optimally tuned.
640 if ( pos.piece_count(Them, QUEEN) >= 1
641 && ei.kingAttackersCount[Them] >= 2
642 && pos.non_pawn_material(Them) >= QueenValueMidgame + RookValueMidgame
643 && ei.kingAdjacentZoneAttacksCount[Them])
645 // Is it the attackers turn to move?
646 sente = (Them == pos.side_to_move());
648 // Find the attacked squares around the king which has no defenders
649 // apart from the king itself
650 undefended = ei.attacked_by(Them) & ei.attacked_by(Us, KING);
651 undefended &= ~( ei.attacked_by(Us, PAWN) | ei.attacked_by(Us, KNIGHT)
652 | ei.attacked_by(Us, BISHOP) | ei.attacked_by(Us, ROOK)
653 | ei.attacked_by(Us, QUEEN));
655 // Initialize the 'attackUnits' variable, which is used later on as an
656 // index to the KingDangerTable[] array. The initial value is based on
657 // the number and types of the enemy's attacking pieces, the number of
658 // attacked and undefended squares around our king, the square of the
659 // king, and the quality of the pawn shelter.
660 attackUnits = Min(25, (ei.kingAttackersCount[Them] * ei.kingAttackersWeight[Them]) / 2)
661 + 3 * (ei.kingAdjacentZoneAttacksCount[Them] + count_1s_max_15<HasPopCnt>(undefended))
662 + InitKingDanger[relative_square(Us, ksq)]
663 - mg_value(ei.pi->king_shelter(pos, Us, ksq)) / 32;
665 // Analyse enemy's safe queen contact checks. First find undefended
666 // squares around the king attacked by enemy queen...
667 b = undefended & ei.attacked_by(Them, QUEEN) & ~pos.pieces_of_color(Them);
670 // ...then remove squares not supported by another enemy piece
671 b &= ( ei.attacked_by(Them, PAWN) | ei.attacked_by(Them, KNIGHT)
672 | ei.attacked_by(Them, BISHOP) | ei.attacked_by(Them, ROOK));
674 attackUnits += QueenContactCheckBonus * count_1s_max_15<HasPopCnt>(b) * (sente ? 2 : 1);
677 // Analyse enemy's safe distance checks for sliders and knights
678 safe = ~(pos.pieces_of_color(Them) | ei.attacked_by(Us));
680 b1 = pos.attacks_from<ROOK>(ksq) & safe;
681 b2 = pos.attacks_from<BISHOP>(ksq) & safe;
683 // Enemy queen safe checks
684 b = (b1 | b2) & ei.attacked_by(Them, QUEEN);
686 attackUnits += QueenCheckBonus * count_1s_max_15<HasPopCnt>(b);
688 // Enemy rooks safe checks
689 b = b1 & ei.attacked_by(Them, ROOK);
691 attackUnits += RookCheckBonus * count_1s_max_15<HasPopCnt>(b);
693 // Enemy bishops safe checks
694 b = b2 & ei.attacked_by(Them, BISHOP);
696 attackUnits += BishopCheckBonus * count_1s_max_15<HasPopCnt>(b);
698 // Enemy knights safe checks
699 b = pos.attacks_from<KNIGHT>(ksq) & ei.attacked_by(Them, KNIGHT) & safe;
701 attackUnits += KnightCheckBonus * count_1s_max_15<HasPopCnt>(b);
703 // To index KingDangerTable[] attackUnits must be in [0, 99] range
704 attackUnits = Min(99, Max(0, attackUnits));
706 // Finally, extract the king danger score from the KingDangerTable[]
707 // array and subtract the score from evaluation. Set also ei.kingDanger[]
708 // value that will be used for pruning because this value can sometimes
709 // be very big, and so capturing a single attacking piece can therefore
710 // result in a score change far bigger than the value of the captured piece.
711 ei.value -= Sign[Us] * KingDangerTable[Us][attackUnits];
712 ei.kingDanger[Us] = mg_value(KingDangerTable[Us][attackUnits]);
717 // evaluate_passed_pawns<>() evaluates the passed pawns of the given color
720 void evaluate_passed_pawns(const Position& pos, EvalInfo& ei) {
722 const Color Them = (Us == WHITE ? BLACK : WHITE);
724 Bitboard squaresToQueen, defendedSquares, unsafeSquares, supportingPawns;
725 Bitboard b = ei.pi->passed_pawns(Us);
729 Square s = pop_1st_bit(&b);
731 assert(pos.pawn_is_passed(Us, s));
733 int r = int(relative_rank(Us, s) - RANK_2);
734 int tr = r * (r - 1);
736 // Base bonus based on rank
737 Value mbonus = Value(20 * tr);
738 Value ebonus = Value(10 + r * r * 10);
742 Square blockSq = s + pawn_push(Us);
744 // Adjust bonus based on kings proximity
745 ebonus -= Value(square_distance(pos.king_square(Us), blockSq) * 3 * tr);
746 ebonus -= Value(square_distance(pos.king_square(Us), blockSq + pawn_push(Us)) * 1 * tr);
747 ebonus += Value(square_distance(pos.king_square(Them), blockSq) * 6 * tr);
749 // If the pawn is free to advance, increase bonus
750 if (pos.square_is_empty(blockSq))
752 squaresToQueen = squares_in_front_of(Us, s);
753 defendedSquares = squaresToQueen & ei.attacked_by(Us);
755 // If there is an enemy rook or queen attacking the pawn from behind,
756 // add all X-ray attacks by the rook or queen. Otherwise consider only
757 // the squares in the pawn's path attacked or occupied by the enemy.
758 if ( (squares_behind(Us, s) & pos.pieces(ROOK, QUEEN, Them))
759 && (squares_behind(Us, s) & pos.pieces(ROOK, QUEEN, Them) & pos.attacks_from<ROOK>(s)))
760 unsafeSquares = squaresToQueen;
762 unsafeSquares = squaresToQueen & (ei.attacked_by(Them) | pos.pieces_of_color(Them));
764 // If there aren't enemy attacks or pieces along the path to queen give
765 // huge bonus. Even bigger if we protect the pawn's path.
767 ebonus += Value(tr * (squaresToQueen == defendedSquares ? 17 : 15));
769 // OK, there are enemy attacks or pieces (but not pawns). Are those
770 // squares which are attacked by the enemy also attacked by us ?
771 // If yes, big bonus (but smaller than when there are no enemy attacks),
772 // if no, somewhat smaller bonus.
773 ebonus += Value(tr * ((unsafeSquares & defendedSquares) == unsafeSquares ? 13 : 8));
775 // At last, add a small bonus when there are no *friendly* pieces
776 // in the pawn's path.
777 if (!(squaresToQueen & pos.pieces_of_color(Us)))
782 // Increase the bonus if the passed pawn is supported by a friendly pawn
783 // on the same rank and a bit smaller if it's on the previous rank.
784 supportingPawns = pos.pieces(PAWN, Us) & neighboring_files_bb(s);
785 if (supportingPawns & rank_bb(s))
786 ebonus += Value(r * 20);
787 else if (supportingPawns & rank_bb(s - pawn_push(Us)))
788 ebonus += Value(r * 12);
790 // Rook pawns are a special case: They are sometimes worse, and
791 // sometimes better than other passed pawns. It is difficult to find
792 // good rules for determining whether they are good or bad. For now,
793 // we try the following: Increase the value for rook pawns if the
794 // other side has no pieces apart from a knight, and decrease the
795 // value if the other side has a rook or queen.
796 if (square_file(s) == FILE_A || square_file(s) == FILE_H)
798 if (pos.non_pawn_material(Them) <= KnightValueMidgame)
799 ebonus += ebonus / 4;
800 else if (pos.pieces(ROOK, QUEEN, Them))
801 ebonus -= ebonus / 4;
804 // Add the scores for this pawn to the middle game and endgame eval
805 ei.value += Sign[Us] * apply_weight(make_score(mbonus, ebonus), Weights[PassedPawns]);
811 // evaluate_space() computes the space evaluation for a given side. The
812 // space evaluation is a simple bonus based on the number of safe squares
813 // available for minor pieces on the central four files on ranks 2--4. Safe
814 // squares one, two or three squares behind a friendly pawn are counted
815 // twice. Finally, the space bonus is scaled by a weight taken from the
816 // material hash table.
817 template<Color Us, bool HasPopCnt>
818 int evaluate_space(const Position& pos, EvalInfo& ei) {
820 const Color Them = (Us == WHITE ? BLACK : WHITE);
822 // Find the safe squares for our pieces inside the area defined by
823 // SpaceMask[us]. A square is unsafe if it is attacked by an enemy
824 // pawn, or if it is undefended and attacked by an enemy piece.
825 Bitboard safe = SpaceMask[Us]
826 & ~pos.pieces(PAWN, Us)
827 & ~ei.attacked_by(Them, PAWN)
828 & (ei.attacked_by(Us) | ~ei.attacked_by(Them));
830 // Find all squares which are at most three squares behind some friendly pawn
831 Bitboard behind = pos.pieces(PAWN, Us);
832 behind |= (Us == WHITE ? behind >> 8 : behind << 8);
833 behind |= (Us == WHITE ? behind >> 16 : behind << 16);
835 return count_1s_max_15<HasPopCnt>(safe) + count_1s_max_15<HasPopCnt>(behind & safe);
839 // apply_weight() applies an evaluation weight to a value trying to prevent overflow
841 inline Score apply_weight(Score v, Score w) {
842 return make_score((int(mg_value(v)) * mg_value(w)) / 0x100, (int(eg_value(v)) * eg_value(w)) / 0x100);
846 // scale_by_game_phase() interpolates between a middle game and an endgame score,
847 // based on game phase. It also scales the return value by a ScaleFactor array.
849 Value scale_by_game_phase(const Score& v, Phase ph, const ScaleFactor sf[]) {
851 assert(mg_value(v) > -VALUE_INFINITE && mg_value(v) < VALUE_INFINITE);
852 assert(eg_value(v) > -VALUE_INFINITE && eg_value(v) < VALUE_INFINITE);
853 assert(ph >= PHASE_ENDGAME && ph <= PHASE_MIDGAME);
855 Value eg = eg_value(v);
856 ScaleFactor f = sf[eg > VALUE_ZERO ? WHITE : BLACK];
857 Value ev = Value((eg * int(f)) / SCALE_FACTOR_NORMAL);
859 int result = (mg_value(v) * int(ph) + ev * int(128 - ph)) / 128;
860 return Value(result & ~(GrainSize - 1));
864 // weight_option() computes the value of an evaluation weight, by combining
865 // two UCI-configurable weights (midgame and endgame) with an internal weight.
867 Score weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight) {
869 // Scale option value from 100 to 256
870 int mg = get_option_value_int(mgOpt) * 256 / 100;
871 int eg = get_option_value_int(egOpt) * 256 / 100;
873 return apply_weight(make_score(mg, eg), internalWeight);
876 // init_safety() initizes the king safety evaluation, based on UCI
877 // parameters. It is called from read_weights().
881 const Value MaxSlope = Value(30);
882 const Value Peak = Value(1280);
885 // First setup the base table
886 for (int i = 0; i < 100; i++)
888 t[i] = Value(int(0.4 * i * i));
891 t[i] = Min(t[i], t[i - 1] + MaxSlope);
893 t[i] = Min(t[i], Peak);
896 // Then apply the weights and get the final KingDangerTable[] array
897 for (Color c = WHITE; c <= BLACK; c++)
898 for (int i = 0; i < 100; i++)
899 KingDangerTable[c][i] = apply_weight(make_score(t[i], 0), Weights[KingDangerUs + c]);