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/>.
32 #include "ucioption.h"
36 //// Local definitions
41 // Struct EvalInfo contains various information computed and collected
42 // by the evaluation functions.
45 // Middle and end game position's static evaluations
48 // margin[color] stores the evaluation margins we should consider for
49 // the given position. This is a kind of uncertainty estimation and
50 // typically is used by the search for pruning decisions.
53 // Pointer to pawn hash table entry
56 // attackedBy[color][piece type] is a bitboard representing all squares
57 // attacked by a given color and piece type, attackedBy[color][0] contains
58 // all squares attacked by the given color.
59 Bitboard attackedBy[2][8];
61 // kingZone[color] is the zone around the enemy king which is considered
62 // by the king safety evaluation. This consists of the squares directly
63 // adjacent to the king, and the three (or two, for a king on an edge file)
64 // squares two ranks in front of the king. For instance, if black's king
65 // is on g8, kingZone[WHITE] is a bitboard containing the squares f8, h8,
66 // f7, g7, h7, f6, g6 and h6.
69 // kingAttackersCount[color] is the number of pieces of the given color
70 // which attack a square in the kingZone of the enemy king.
71 int kingAttackersCount[2];
73 // kingAttackersWeight[color] is the sum of the "weight" of the pieces of the
74 // given color which attack a square in the kingZone of the enemy king. The
75 // weights of the individual piece types are given by the variables
76 // QueenAttackWeight, RookAttackWeight, BishopAttackWeight and
77 // KnightAttackWeight in evaluate.cpp
78 int kingAttackersWeight[2];
80 // kingAdjacentZoneAttacksCount[color] is the number of attacks to squares
81 // directly adjacent to the king of the given color. Pieces which attack
82 // more than one square are counted multiple times. For instance, if black's
83 // king is on g8 and there's a white knight on g5, this knight adds
84 // 2 to kingAdjacentZoneAttacksCount[BLACK].
85 int kingAdjacentZoneAttacksCount[2];
88 const int Sign[2] = { 1, -1 };
90 // Evaluation grain size, must be a power of 2
91 const int GrainSize = 8;
93 // Evaluation weights, initialized from UCI options
94 enum { Mobility, PawnStructure, PassedPawns, Space, KingDangerUs, KingDangerThem };
98 #define S(mg, eg) make_score(mg, eg)
100 // Internal evaluation weights. These are applied on top of the evaluation
101 // weights read from UCI parameters. The purpose is to be able to change
102 // the evaluation weights while keeping the default values of the UCI
103 // parameters at 100, which looks prettier.
105 // Values modified by Joona Kiiski
106 const Score WeightsInternal[] = {
107 S(248, 271), S(233, 201), S(252, 259), S(46, 0), S(247, 0), S(259, 0)
110 // MobilityBonus[PieceType][attacked] contains mobility bonuses for middle and
111 // end game, indexed by piece type and number of attacked squares not occupied
112 // by friendly pieces.
113 const Score MobilityBonus[][32] = {
115 { S(-38,-33), S(-25,-23), S(-12,-13), S( 0, -3), S(12, 7), S(25, 17), // Knights
116 S( 31, 22), S( 38, 27), S( 38, 27) },
117 { S(-25,-30), S(-11,-16), S( 3, -2), S(17, 12), S(31, 26), S(45, 40), // Bishops
118 S( 57, 52), S( 65, 60), S( 71, 65), S(74, 69), S(76, 71), S(78, 73),
119 S( 79, 74), S( 80, 75), S( 81, 76), S(81, 76) },
120 { S(-20,-36), S(-14,-19), S( -8, -3), S(-2, 13), S( 4, 29), S(10, 46), // Rooks
121 S( 14, 62), S( 19, 79), S( 23, 95), S(26,106), S(27,111), S(28,114),
122 S( 29,116), S( 30,117), S( 31,118), S(32,118) },
123 { S(-10,-18), S( -8,-13), S( -6, -7), S(-3, -2), S(-1, 3), S( 1, 8), // Queens
124 S( 3, 13), S( 5, 19), S( 8, 23), S(10, 27), S(12, 32), S(15, 34),
125 S( 16, 35), S( 17, 35), S( 18, 35), S(20, 35), S(20, 35), S(20, 35),
126 S( 20, 35), S( 20, 35), S( 20, 35), S(20, 35), S(20, 35), S(20, 35),
127 S( 20, 35), S( 20, 35), S( 20, 35), S(20, 35), S(20, 35), S(20, 35),
128 S( 20, 35), S( 20, 35) }
131 // OutpostBonus[PieceType][Square] contains outpost bonuses of knights and
132 // bishops, indexed by piece type and square (from white's point of view).
133 const Value OutpostBonus[][64] = {
136 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // Knights
137 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0),
138 V(0), V(0), V(4), V(8), V(8), V(4), V(0), V(0),
139 V(0), V(4),V(17),V(26),V(26),V(17), V(4), V(0),
140 V(0), V(8),V(26),V(35),V(35),V(26), V(8), V(0),
141 V(0), V(4),V(17),V(17),V(17),V(17), V(4), V(0),
142 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0),
143 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0) },
145 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // Bishops
146 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0),
147 V(0), V(0), V(5), V(5), V(5), V(5), V(0), V(0),
148 V(0), V(5),V(10),V(10),V(10),V(10), V(5), V(0),
149 V(0),V(10),V(21),V(21),V(21),V(21),V(10), V(0),
150 V(0), V(5), V(8), V(8), V(8), V(8), V(5), V(0),
151 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0),
152 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0) }
155 // ThreatBonus[attacking][attacked] contains threat bonuses according to
156 // which piece type attacks which one.
157 const Score ThreatBonus[][8] = {
159 { S(0, 0), S( 7, 39), S( 0, 0), S(24, 49), S(41,100), S(41,100) }, // KNIGHT
160 { S(0, 0), S( 7, 39), S(24, 49), S( 0, 0), S(41,100), S(41,100) }, // BISHOP
161 { S(0, 0), S(-1, 29), S(15, 49), S(15, 49), S( 0, 0), S(24, 49) }, // ROOK
162 { S(0, 0), S(15, 39), S(15, 39), S(15, 39), S(15, 39), S( 0, 0) } // QUEEN
165 // ThreatedByPawnPenalty[PieceType] contains a penalty according to which
166 // piece type is attacked by an enemy pawn.
167 const Score ThreatedByPawnPenalty[] = {
168 S(0, 0), S(0, 0), S(56, 70), S(56, 70), S(76, 99), S(86, 118)
173 // Rooks and queens on the 7th rank (modified by Joona Kiiski)
174 const Score RookOn7thBonus = make_score(47, 98);
175 const Score QueenOn7thBonus = make_score(27, 54);
177 // Rooks on open files (modified by Joona Kiiski)
178 const Score RookOpenFileBonus = make_score(43, 43);
179 const Score RookHalfOpenFileBonus = make_score(19, 19);
181 // Penalty for rooks trapped inside a friendly king which has lost the
183 const Value TrappedRookPenalty = Value(180);
185 // The SpaceMask[Color] contains the area of the board which is considered
186 // by the space evaluation. In the middle game, each side is given a bonus
187 // based on how many squares inside this area are safe and available for
188 // friendly minor pieces.
189 const Bitboard SpaceMask[2] = {
190 (1ULL << SQ_C2) | (1ULL << SQ_D2) | (1ULL << SQ_E2) | (1ULL << SQ_F2) |
191 (1ULL << SQ_C3) | (1ULL << SQ_D3) | (1ULL << SQ_E3) | (1ULL << SQ_F3) |
192 (1ULL << SQ_C4) | (1ULL << SQ_D4) | (1ULL << SQ_E4) | (1ULL << SQ_F4),
193 (1ULL << SQ_C7) | (1ULL << SQ_D7) | (1ULL << SQ_E7) | (1ULL << SQ_F7) |
194 (1ULL << SQ_C6) | (1ULL << SQ_D6) | (1ULL << SQ_E6) | (1ULL << SQ_F6) |
195 (1ULL << SQ_C5) | (1ULL << SQ_D5) | (1ULL << SQ_E5) | (1ULL << SQ_F5)
198 // King danger constants and variables. The king danger scores are taken
199 // from the KingDangerTable[]. Various little "meta-bonuses" measuring
200 // the strength of the enemy attack are added up into an integer, which
201 // is used as an index to KingDangerTable[].
203 // KingAttackWeights[PieceType] contains king attack weights by piece type
204 const int KingAttackWeights[] = { 0, 0, 2, 2, 3, 5 };
206 // Bonuses for enemy's safe checks
207 const int QueenContactCheckBonus = 3;
208 const int QueenCheckBonus = 2;
209 const int RookCheckBonus = 1;
210 const int BishopCheckBonus = 1;
211 const int KnightCheckBonus = 1;
213 // InitKingDanger[Square] contains penalties based on the position of the
214 // defending king, indexed by king's square (from white's point of view).
215 const int InitKingDanger[] = {
216 2, 0, 2, 5, 5, 2, 0, 2,
217 2, 2, 4, 8, 8, 4, 2, 2,
218 7, 10, 12, 12, 12, 12, 10, 7,
219 15, 15, 15, 15, 15, 15, 15, 15,
220 15, 15, 15, 15, 15, 15, 15, 15,
221 15, 15, 15, 15, 15, 15, 15, 15,
222 15, 15, 15, 15, 15, 15, 15, 15,
223 15, 15, 15, 15, 15, 15, 15, 15
226 // KingDangerTable[Color][attackUnits] contains the actual king danger
227 // weighted scores, indexed by color and by a calculated integer number.
228 Score KingDangerTable[2][128];
230 // Pawn and material hash tables, indexed by the current thread id.
231 // Note that they will be initialized at 0 being global variables.
232 MaterialInfoTable* MaterialTable[MAX_THREADS];
233 PawnInfoTable* PawnTable[MAX_THREADS];
235 // Function prototypes
236 template<bool HasPopCnt>
237 Value do_evaluate(const Position& pos, Value margins[]);
239 template<Color Us, bool HasPopCnt>
240 void init_attack_tables(const Position& pos, EvalInfo& ei);
242 template<Color Us, bool HasPopCnt>
243 Score evaluate_pieces_of_color(const Position& pos, EvalInfo& ei);
245 template<Color Us, bool HasPopCnt>
246 void evaluate_king(const Position& pos, EvalInfo& ei);
249 void evaluate_threats(const Position& pos, EvalInfo& ei);
251 template<Color Us, bool HasPopCnt>
252 int evaluate_space(const Position& pos, EvalInfo& ei);
255 void evaluate_passed_pawns(const Position& pos, EvalInfo& ei);
257 inline Score apply_weight(Score v, Score weight);
258 Value scale_by_game_phase(const Score& v, Phase ph, const ScaleFactor sf[]);
259 Score weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight);
269 /// Prefetches in pawn hash tables
271 void prefetchPawn(Key key, int threadID) {
273 PawnTable[threadID]->prefetch(key);
276 /// evaluate() is the main evaluation function. It always computes two
277 /// values, an endgame score and a middle game score, and interpolates
278 /// between them based on the remaining material.
279 Value evaluate(const Position& pos, Value margins[]) {
281 return CpuHasPOPCNT ? do_evaluate<true>(pos, margins)
282 : do_evaluate<false>(pos, margins);
287 template<bool HasPopCnt>
288 Value do_evaluate(const Position& pos, Value margins[]) {
291 ScaleFactor factor[2];
295 assert(pos.thread() >= 0 && pos.thread() < MAX_THREADS);
296 assert(!pos.is_check());
298 // Initialize by reading the incrementally updated scores included in the
299 // position object (material + piece square tables).
300 ei.value = pos.value();
302 // Probe the material hash table
303 MaterialInfo* mi = MaterialTable[pos.thread()]->get_material_info(pos);
304 ei.value += mi->material_value();
306 // If we have a specialized evaluation function for the current material
307 // configuration, call it and return.
308 if (mi->specialized_eval_exists())
309 return mi->evaluate(pos);
311 // After get_material_info() call that modifies them
312 factor[WHITE] = mi->scale_factor(pos, WHITE);
313 factor[BLACK] = mi->scale_factor(pos, BLACK);
315 // Probe the pawn hash table
316 ei.pi = PawnTable[pos.thread()]->get_pawn_info(pos);
317 ei.value += apply_weight(ei.pi->pawns_value(), Weights[PawnStructure]);
319 // Initialize attack bitboards with pawns evaluation
320 init_attack_tables<WHITE, HasPopCnt>(pos, ei);
321 init_attack_tables<BLACK, HasPopCnt>(pos, ei);
323 // Evaluate pieces and mobility
324 mobility = evaluate_pieces_of_color<WHITE, HasPopCnt>(pos, ei)
325 - evaluate_pieces_of_color<BLACK, HasPopCnt>(pos, ei);
326 ei.value += apply_weight(mobility, Weights[Mobility]);
328 // Kings. Kings are evaluated after all other pieces for both sides,
329 // because we need complete attack information for all pieces when computing
330 // the king safety evaluation.
331 evaluate_king<WHITE, HasPopCnt>(pos, ei);
332 evaluate_king<BLACK, HasPopCnt>(pos, ei);
334 // Evaluate tactical threats, we need full attack info including king
335 evaluate_threats<WHITE>(pos, ei);
336 evaluate_threats<BLACK>(pos, ei);
338 // Evaluate passed pawns, we need full attack info including king
339 evaluate_passed_pawns<WHITE>(pos, ei);
340 evaluate_passed_pawns<BLACK>(pos, ei);
342 Phase phase = mi->game_phase();
344 // Middle-game specific evaluation terms
345 if (phase > PHASE_ENDGAME)
347 // Evaluate pawn storms in positions with opposite castling
348 if ( square_file(pos.king_square(WHITE)) >= FILE_E
349 && square_file(pos.king_square(BLACK)) <= FILE_D)
351 ei.value += make_score(ei.pi->queenside_storm_value(WHITE) - ei.pi->kingside_storm_value(BLACK), 0);
353 else if ( square_file(pos.king_square(WHITE)) <= FILE_D
354 && square_file(pos.king_square(BLACK)) >= FILE_E)
356 ei.value += make_score(ei.pi->kingside_storm_value(WHITE) - ei.pi->queenside_storm_value(BLACK), 0);
358 // Evaluate space for both sides
359 if (mi->space_weight() > 0)
361 int s = evaluate_space<WHITE, HasPopCnt>(pos, ei) - evaluate_space<BLACK, HasPopCnt>(pos, ei);
362 ei.value += apply_weight(make_score(s * mi->space_weight(), 0), Weights[Space]);
366 // If we don't already have an unusual scale factor, check for opposite
367 // colored bishop endgames, and use a lower scale for those
368 if ( phase < PHASE_MIDGAME
369 && pos.opposite_colored_bishops()
370 && ( (factor[WHITE] == SCALE_FACTOR_NORMAL && eg_value(ei.value) > VALUE_ZERO)
371 || (factor[BLACK] == SCALE_FACTOR_NORMAL && eg_value(ei.value) < VALUE_ZERO)))
375 // Only the two bishops ?
376 if ( pos.non_pawn_material(WHITE) == BishopValueMidgame
377 && pos.non_pawn_material(BLACK) == BishopValueMidgame)
379 // Check for KBP vs KB with only a single pawn that is almost
380 // certainly a draw or at least two pawns.
381 bool one_pawn = (pos.piece_count(WHITE, PAWN) + pos.piece_count(BLACK, PAWN) == 1);
382 sf = one_pawn ? ScaleFactor(8) : ScaleFactor(32);
385 // Endgame with opposite-colored bishops, but also other pieces. Still
386 // a bit drawish, but not as drawish as with only the two bishops.
387 sf = ScaleFactor(50);
389 if (factor[WHITE] == SCALE_FACTOR_NORMAL)
391 if (factor[BLACK] == SCALE_FACTOR_NORMAL)
395 // Populate margins[]
396 margins[WHITE] = ei.margin[WHITE];
397 margins[BLACK] = ei.margin[BLACK];
399 // Interpolate between the middle game and the endgame score
400 return Sign[pos.side_to_move()] * scale_by_game_phase(ei.value, phase, factor);
405 /// init_eval() initializes various tables used by the evaluation function
407 void init_eval(int threads) {
409 assert(threads <= MAX_THREADS);
411 for (int i = 0; i < MAX_THREADS; i++)
416 delete MaterialTable[i];
418 MaterialTable[i] = NULL;
422 PawnTable[i] = new PawnInfoTable();
423 if (!MaterialTable[i])
424 MaterialTable[i] = new MaterialInfoTable();
429 /// quit_eval() releases heap-allocated memory at program termination
433 for (int i = 0; i < MAX_THREADS; i++)
436 delete MaterialTable[i];
438 MaterialTable[i] = NULL;
443 /// read_weights() reads evaluation weights from the corresponding UCI parameters
445 void read_weights(Color us) {
447 // King safety is asymmetrical. Our king danger level is weighted by
448 // "Cowardice" UCI parameter, instead the opponent one by "Aggressiveness".
449 const int kingDangerUs = (us == WHITE ? KingDangerUs : KingDangerThem);
450 const int kingDangerThem = (us == WHITE ? KingDangerThem : KingDangerUs);
452 Weights[Mobility] = weight_option("Mobility (Middle Game)", "Mobility (Endgame)", WeightsInternal[Mobility]);
453 Weights[PawnStructure] = weight_option("Pawn Structure (Middle Game)", "Pawn Structure (Endgame)", WeightsInternal[PawnStructure]);
454 Weights[PassedPawns] = weight_option("Passed Pawns (Middle Game)", "Passed Pawns (Endgame)", WeightsInternal[PassedPawns]);
455 Weights[Space] = weight_option("Space", "Space", WeightsInternal[Space]);
456 Weights[kingDangerUs] = weight_option("Cowardice", "Cowardice", WeightsInternal[KingDangerUs]);
457 Weights[kingDangerThem] = weight_option("Aggressiveness", "Aggressiveness", WeightsInternal[KingDangerThem]);
459 // If running in analysis mode, make sure we use symmetrical king safety. We do this
460 // by replacing both Weights[kingDangerUs] and Weights[kingDangerThem] by their average.
461 if (get_option_value_bool("UCI_AnalyseMode"))
462 Weights[kingDangerUs] = Weights[kingDangerThem] = (Weights[kingDangerUs] + Weights[kingDangerThem]) / 2;
470 // init_attack_tables() initializes king bitboards for both sides adding
471 // pawn attacks. To be done before other evaluations.
473 template<Color Us, bool HasPopCnt>
474 void init_attack_tables(const Position& pos, EvalInfo& ei) {
476 const Color Them = (Us == WHITE ? BLACK : WHITE);
478 Bitboard b = ei.attackedBy[Them][KING] = pos.attacks_from<KING>(pos.king_square(Them));
479 ei.kingZone[Us] = (b | (Us == WHITE ? b >> 8 : b << 8));
480 ei.attackedBy[Us][PAWN] = ei.pi->pawn_attacks(Us);
481 b &= ei.attackedBy[Us][PAWN];
482 ei.kingAttackersCount[Us] = b ? count_1s_max_15<HasPopCnt>(b) / 2 : 0;
483 ei.kingAdjacentZoneAttacksCount[Us] = ei.kingAttackersWeight[Us] = 0;
487 // evaluate_outposts() evaluates bishop and knight outposts squares
489 template<PieceType Piece, Color Us>
490 void evaluate_outposts(const Position& pos, EvalInfo& ei, Square s) {
492 const Color Them = (Us == WHITE ? BLACK : WHITE);
494 assert (Piece == BISHOP || Piece == KNIGHT);
496 // Initial bonus based on square
497 Value bonus = OutpostBonus[Piece == BISHOP][relative_square(Us, s)];
499 // Increase bonus if supported by pawn, especially if the opponent has
500 // no minor piece which can exchange the outpost piece
501 if (bonus && bit_is_set(ei.attackedBy[Us][PAWN], s))
503 if ( pos.pieces(KNIGHT, Them) == EmptyBoardBB
504 && (SquaresByColorBB[square_color(s)] & pos.pieces(BISHOP, Them)) == EmptyBoardBB)
505 bonus += bonus + bonus / 2;
509 ei.value += Sign[Us] * make_score(bonus, bonus);
513 // evaluate_pieces<>() assigns bonuses and penalties to the pieces of a given color
515 template<PieceType Piece, Color Us, bool HasPopCnt>
516 Score evaluate_pieces(const Position& pos, EvalInfo& ei, Bitboard no_mob_area) {
522 Score mobility = SCORE_ZERO;
524 const Color Them = (Us == WHITE ? BLACK : WHITE);
525 const Square* ptr = pos.piece_list_begin(Us, Piece);
527 ei.attackedBy[Us][Piece] = 0;
529 while ((s = *ptr++) != SQ_NONE)
531 // Find attacked squares, including x-ray attacks for bishops and rooks
532 if (Piece == KNIGHT || Piece == QUEEN)
533 b = pos.attacks_from<Piece>(s);
534 else if (Piece == BISHOP)
535 b = bishop_attacks_bb(s, pos.occupied_squares() & ~pos.pieces(QUEEN, Us));
536 else if (Piece == ROOK)
537 b = rook_attacks_bb(s, pos.occupied_squares() & ~pos.pieces(ROOK, QUEEN, Us));
541 // Update attack info
542 ei.attackedBy[Us][Piece] |= b;
545 if (b & ei.kingZone[Us])
547 ei.kingAttackersCount[Us]++;
548 ei.kingAttackersWeight[Us] += KingAttackWeights[Piece];
549 Bitboard bb = (b & ei.attackedBy[Them][KING]);
551 ei.kingAdjacentZoneAttacksCount[Us] += count_1s_max_15<HasPopCnt>(bb);
555 mob = (Piece != QUEEN ? count_1s_max_15<HasPopCnt>(b & no_mob_area)
556 : count_1s<HasPopCnt>(b & no_mob_area));
558 mobility += MobilityBonus[Piece][mob];
560 // Decrease score if we are attacked by an enemy pawn. Remaining part
561 // of threat evaluation must be done later when we have full attack info.
562 if (bit_is_set(ei.attackedBy[Them][PAWN], s))
563 ei.value -= Sign[Us] * ThreatedByPawnPenalty[Piece];
565 // Bishop and knight outposts squares
566 if ((Piece == BISHOP || Piece == KNIGHT) && pos.square_is_weak(s, Us))
567 evaluate_outposts<Piece, Us>(pos, ei, s);
569 // Queen or rook on 7th rank
570 if ( (Piece == ROOK || Piece == QUEEN)
571 && relative_rank(Us, s) == RANK_7
572 && relative_rank(Us, pos.king_square(Them)) == RANK_8)
574 ei.value += Sign[Us] * (Piece == ROOK ? RookOn7thBonus : QueenOn7thBonus);
577 // Special extra evaluation for rooks
580 // Open and half-open files
582 if (ei.pi->file_is_half_open(Us, f))
584 if (ei.pi->file_is_half_open(Them, f))
585 ei.value += Sign[Us] * RookOpenFileBonus;
587 ei.value += Sign[Us] * RookHalfOpenFileBonus;
590 // Penalize rooks which are trapped inside a king. Penalize more if
591 // king has lost right to castle.
592 if (mob > 6 || ei.pi->file_is_half_open(Us, f))
595 ksq = pos.king_square(Us);
597 if ( square_file(ksq) >= FILE_E
598 && square_file(s) > square_file(ksq)
599 && (relative_rank(Us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
601 // Is there a half-open file between the king and the edge of the board?
602 if (!ei.pi->has_open_file_to_right(Us, square_file(ksq)))
603 ei.value -= Sign[Us] * make_score(pos.can_castle(Us) ? (TrappedRookPenalty - mob * 16) / 2
604 : (TrappedRookPenalty - mob * 16), 0);
606 else if ( square_file(ksq) <= FILE_D
607 && square_file(s) < square_file(ksq)
608 && (relative_rank(Us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
610 // Is there a half-open file between the king and the edge of the board?
611 if (!ei.pi->has_open_file_to_left(Us, square_file(ksq)))
612 ei.value -= Sign[Us] * make_score(pos.can_castle(Us) ? (TrappedRookPenalty - mob * 16) / 2
613 : (TrappedRookPenalty - mob * 16), 0);
621 // evaluate_threats<>() assigns bonuses according to the type of attacking piece
622 // and the type of attacked one.
625 void evaluate_threats(const Position& pos, EvalInfo& ei) {
627 const Color Them = (Us == WHITE ? BLACK : WHITE);
630 Score bonus = SCORE_ZERO;
632 // Enemy pieces not defended by a pawn and under our attack
633 Bitboard weakEnemies = pos.pieces_of_color(Them)
634 & ~ei.attackedBy[Them][PAWN]
635 & ei.attackedBy[Us][0];
639 // Add bonus according to type of attacked enemy pieces and to the
640 // type of attacking piece, from knights to queens. Kings are not
641 // considered because are already special handled in king evaluation.
642 for (PieceType pt1 = KNIGHT; pt1 < KING; pt1++)
644 b = ei.attackedBy[Us][pt1] & weakEnemies;
646 for (PieceType pt2 = PAWN; pt2 < KING; pt2++)
647 if (b & pos.pieces(pt2))
648 bonus += ThreatBonus[pt1][pt2];
650 ei.value += Sign[Us] * bonus;
654 // evaluate_pieces_of_color<>() assigns bonuses and penalties to all the
655 // pieces of a given color.
657 template<Color Us, bool HasPopCnt>
658 Score evaluate_pieces_of_color(const Position& pos, EvalInfo& ei) {
660 const Color Them = (Us == WHITE ? BLACK : WHITE);
662 Score mobility = SCORE_ZERO;
664 // Do not include in mobility squares protected by enemy pawns or occupied by our pieces
665 const Bitboard no_mob_area = ~(ei.attackedBy[Them][PAWN] | pos.pieces_of_color(Us));
667 mobility += evaluate_pieces<KNIGHT, Us, HasPopCnt>(pos, ei, no_mob_area);
668 mobility += evaluate_pieces<BISHOP, Us, HasPopCnt>(pos, ei, no_mob_area);
669 mobility += evaluate_pieces<ROOK, Us, HasPopCnt>(pos, ei, no_mob_area);
670 mobility += evaluate_pieces<QUEEN, Us, HasPopCnt>(pos, ei, no_mob_area);
672 // Sum up all attacked squares
673 ei.attackedBy[Us][0] = ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
674 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
675 | ei.attackedBy[Us][QUEEN] | ei.attackedBy[Us][KING];
680 // evaluate_king<>() assigns bonuses and penalties to a king of a given color
682 template<Color Us, bool HasPopCnt>
683 void evaluate_king(const Position& pos, EvalInfo& ei) {
685 const Color Them = (Us == WHITE ? BLACK : WHITE);
687 Bitboard undefended, b, b1, b2, safe;
690 const Square ksq = pos.king_square(Us);
693 ei.value += Sign[Us] * ei.pi->king_shelter(pos, Us, ksq);
695 // King safety. This is quite complicated, and is almost certainly far
696 // from optimally tuned.
697 if ( pos.piece_count(Them, QUEEN) >= 1
698 && ei.kingAttackersCount[Them] >= 2
699 && pos.non_pawn_material(Them) >= QueenValueMidgame + RookValueMidgame
700 && ei.kingAdjacentZoneAttacksCount[Them])
702 // Is it the attackers turn to move?
703 sente = (Them == pos.side_to_move());
705 // Find the attacked squares around the king which has no defenders
706 // apart from the king itself
707 undefended = ei.attackedBy[Them][0] & ei.attackedBy[Us][KING];
708 undefended &= ~( ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
709 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
710 | ei.attackedBy[Us][QUEEN]);
712 // Initialize the 'attackUnits' variable, which is used later on as an
713 // index to the KingDangerTable[] array. The initial value is based on
714 // the number and types of the enemy's attacking pieces, the number of
715 // attacked and undefended squares around our king, the square of the
716 // king, and the quality of the pawn shelter.
717 attackUnits = Min(25, (ei.kingAttackersCount[Them] * ei.kingAttackersWeight[Them]) / 2)
718 + 3 * (ei.kingAdjacentZoneAttacksCount[Them] + count_1s_max_15<HasPopCnt>(undefended))
719 + InitKingDanger[relative_square(Us, ksq)]
720 - mg_value(ei.pi->king_shelter(pos, Us, ksq)) / 32;
722 // Analyse enemy's safe queen contact checks. First find undefended
723 // squares around the king attacked by enemy queen...
724 b = undefended & ei.attackedBy[Them][QUEEN] & ~pos.pieces_of_color(Them);
727 // ...then remove squares not supported by another enemy piece
728 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
729 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][ROOK]);
731 attackUnits += QueenContactCheckBonus * count_1s_max_15<HasPopCnt>(b) * (sente ? 2 : 1);
734 // Analyse enemy's safe distance checks for sliders and knights
735 safe = ~(pos.pieces_of_color(Them) | ei.attackedBy[Us][0]);
737 b1 = pos.attacks_from<ROOK>(ksq) & safe;
738 b2 = pos.attacks_from<BISHOP>(ksq) & safe;
740 // Enemy queen safe checks
741 b = (b1 | b2) & ei.attackedBy[Them][QUEEN];
743 attackUnits += QueenCheckBonus * count_1s_max_15<HasPopCnt>(b);
745 // Enemy rooks safe checks
746 b = b1 & ei.attackedBy[Them][ROOK];
748 attackUnits += RookCheckBonus * count_1s_max_15<HasPopCnt>(b);
750 // Enemy bishops safe checks
751 b = b2 & ei.attackedBy[Them][BISHOP];
753 attackUnits += BishopCheckBonus * count_1s_max_15<HasPopCnt>(b);
755 // Enemy knights safe checks
756 b = pos.attacks_from<KNIGHT>(ksq) & ei.attackedBy[Them][KNIGHT] & safe;
758 attackUnits += KnightCheckBonus * count_1s_max_15<HasPopCnt>(b);
760 // To index KingDangerTable[] attackUnits must be in [0, 99] range
761 attackUnits = Min(99, Max(0, attackUnits));
763 // Finally, extract the king danger score from the KingDangerTable[]
764 // array and subtract the score from evaluation. Set also ei.margin[]
765 // value that will be used for pruning because this value can sometimes
766 // be very big, and so capturing a single attacking piece can therefore
767 // result in a score change far bigger than the value of the captured piece.
768 ei.value -= Sign[Us] * KingDangerTable[Us][attackUnits];
769 ei.margin[Us] = mg_value(KingDangerTable[Us][attackUnits]);
771 ei.margin[Us] = VALUE_ZERO;
775 // evaluate_passed_pawns<>() evaluates the passed pawns of the given color
778 void evaluate_passed_pawns(const Position& pos, EvalInfo& ei) {
780 const Color Them = (Us == WHITE ? BLACK : WHITE);
782 Score bonus = SCORE_ZERO;
783 Bitboard squaresToQueen, defendedSquares, unsafeSquares, supportingPawns;
784 Bitboard b = ei.pi->passed_pawns(Us);
790 Square s = pop_1st_bit(&b);
792 assert(pos.pawn_is_passed(Us, s));
794 int r = int(relative_rank(Us, s) - RANK_2);
795 int tr = r * (r - 1);
797 // Base bonus based on rank
798 Value mbonus = Value(20 * tr);
799 Value ebonus = Value(10 + r * r * 10);
803 Square blockSq = s + pawn_push(Us);
805 // Adjust bonus based on kings proximity
806 ebonus -= Value(square_distance(pos.king_square(Us), blockSq) * 3 * tr);
807 ebonus -= Value(square_distance(pos.king_square(Us), blockSq + pawn_push(Us)) * 1 * tr);
808 ebonus += Value(square_distance(pos.king_square(Them), blockSq) * 6 * tr);
810 // If the pawn is free to advance, increase bonus
811 if (pos.square_is_empty(blockSq))
813 squaresToQueen = squares_in_front_of(Us, s);
814 defendedSquares = squaresToQueen & ei.attackedBy[Us][0];
816 // If there is an enemy rook or queen attacking the pawn from behind,
817 // add all X-ray attacks by the rook or queen. Otherwise consider only
818 // the squares in the pawn's path attacked or occupied by the enemy.
819 if ( (squares_behind(Us, s) & pos.pieces(ROOK, QUEEN, Them))
820 && (squares_behind(Us, s) & pos.pieces(ROOK, QUEEN, Them) & pos.attacks_from<ROOK>(s)))
821 unsafeSquares = squaresToQueen;
823 unsafeSquares = squaresToQueen & (ei.attackedBy[Them][0] | pos.pieces_of_color(Them));
825 // If there aren't enemy attacks or pieces along the path to queen give
826 // huge bonus. Even bigger if we protect the pawn's path.
828 ebonus += Value(tr * (squaresToQueen == defendedSquares ? 17 : 15));
830 // OK, there are enemy attacks or pieces (but not pawns). Are those
831 // squares which are attacked by the enemy also attacked by us ?
832 // If yes, big bonus (but smaller than when there are no enemy attacks),
833 // if no, somewhat smaller bonus.
834 ebonus += Value(tr * ((unsafeSquares & defendedSquares) == unsafeSquares ? 13 : 8));
836 // At last, add a small bonus when there are no *friendly* pieces
837 // in the pawn's path.
838 if (!(squaresToQueen & pos.pieces_of_color(Us)))
843 // Increase the bonus if the passed pawn is supported by a friendly pawn
844 // on the same rank and a bit smaller if it's on the previous rank.
845 supportingPawns = pos.pieces(PAWN, Us) & neighboring_files_bb(s);
846 if (supportingPawns & rank_bb(s))
847 ebonus += Value(r * 20);
848 else if (supportingPawns & rank_bb(s - pawn_push(Us)))
849 ebonus += Value(r * 12);
851 // Rook pawns are a special case: They are sometimes worse, and
852 // sometimes better than other passed pawns. It is difficult to find
853 // good rules for determining whether they are good or bad. For now,
854 // we try the following: Increase the value for rook pawns if the
855 // other side has no pieces apart from a knight, and decrease the
856 // value if the other side has a rook or queen.
857 if (square_file(s) == FILE_A || square_file(s) == FILE_H)
859 if (pos.non_pawn_material(Them) <= KnightValueMidgame)
860 ebonus += ebonus / 4;
861 else if (pos.pieces(ROOK, QUEEN, Them))
862 ebonus -= ebonus / 4;
864 bonus += make_score(mbonus, ebonus);
868 // Add the scores to the middle game and endgame eval
869 ei.value += Sign[Us] * apply_weight(bonus, Weights[PassedPawns]);
873 // evaluate_space() computes the space evaluation for a given side. The
874 // space evaluation is a simple bonus based on the number of safe squares
875 // available for minor pieces on the central four files on ranks 2--4. Safe
876 // squares one, two or three squares behind a friendly pawn are counted
877 // twice. Finally, the space bonus is scaled by a weight taken from the
878 // material hash table.
879 template<Color Us, bool HasPopCnt>
880 int evaluate_space(const Position& pos, EvalInfo& ei) {
882 const Color Them = (Us == WHITE ? BLACK : WHITE);
884 // Find the safe squares for our pieces inside the area defined by
885 // SpaceMask[us]. A square is unsafe if it is attacked by an enemy
886 // pawn, or if it is undefended and attacked by an enemy piece.
887 Bitboard safe = SpaceMask[Us]
888 & ~pos.pieces(PAWN, Us)
889 & ~ei.attackedBy[Them][PAWN]
890 & (ei.attackedBy[Us][0] | ~ei.attackedBy[Them][0]);
892 // Find all squares which are at most three squares behind some friendly pawn
893 Bitboard behind = pos.pieces(PAWN, Us);
894 behind |= (Us == WHITE ? behind >> 8 : behind << 8);
895 behind |= (Us == WHITE ? behind >> 16 : behind << 16);
897 return count_1s_max_15<HasPopCnt>(safe) + count_1s_max_15<HasPopCnt>(behind & safe);
901 // apply_weight() applies an evaluation weight to a value trying to prevent overflow
903 inline Score apply_weight(Score v, Score w) {
904 return make_score((int(mg_value(v)) * mg_value(w)) / 0x100, (int(eg_value(v)) * eg_value(w)) / 0x100);
908 // scale_by_game_phase() interpolates between a middle game and an endgame score,
909 // based on game phase. It also scales the return value by a ScaleFactor array.
911 Value scale_by_game_phase(const Score& v, Phase ph, const ScaleFactor sf[]) {
913 assert(mg_value(v) > -VALUE_INFINITE && mg_value(v) < VALUE_INFINITE);
914 assert(eg_value(v) > -VALUE_INFINITE && eg_value(v) < VALUE_INFINITE);
915 assert(ph >= PHASE_ENDGAME && ph <= PHASE_MIDGAME);
917 Value eg = eg_value(v);
918 ScaleFactor f = sf[eg > VALUE_ZERO ? WHITE : BLACK];
919 Value ev = Value((eg * int(f)) / SCALE_FACTOR_NORMAL);
921 int result = (mg_value(v) * int(ph) + ev * int(128 - ph)) / 128;
922 return Value(result & ~(GrainSize - 1));
926 // weight_option() computes the value of an evaluation weight, by combining
927 // two UCI-configurable weights (midgame and endgame) with an internal weight.
929 Score weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight) {
931 // Scale option value from 100 to 256
932 int mg = get_option_value_int(mgOpt) * 256 / 100;
933 int eg = get_option_value_int(egOpt) * 256 / 100;
935 return apply_weight(make_score(mg, eg), internalWeight);
938 // init_safety() initizes the king safety evaluation, based on UCI
939 // parameters. It is called from read_weights().
943 const Value MaxSlope = Value(30);
944 const Value Peak = Value(1280);
947 // First setup the base table
948 for (int i = 0; i < 100; i++)
950 t[i] = Value(int(0.4 * i * i));
953 t[i] = Min(t[i], t[i - 1] + MaxSlope);
955 t[i] = Min(t[i], Peak);
958 // Then apply the weights and get the final KingDangerTable[] array
959 for (Color c = WHITE; c <= BLACK; c++)
960 for (int i = 0; i < 100; i++)
961 KingDangerTable[c][i] = apply_weight(make_score(t[i], 0), Weights[KingDangerUs + c]);