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 // Pointer to pawn hash table entry
51 // attackedBy[color][piece type] is a bitboard representing all squares
52 // attacked by a given color and piece type, attackedBy[color][0] contains
53 // all squares attacked by the given color.
54 Bitboard attackedBy[2][8];
56 // kingZone[color] is the zone around the enemy king which is considered
57 // by the king safety evaluation. This consists of the squares directly
58 // adjacent to the king, and the three (or two, for a king on an edge file)
59 // squares two ranks in front of the king. For instance, if black's king
60 // is on g8, kingZone[WHITE] is a bitboard containing the squares f8, h8,
61 // f7, g7, h7, f6, g6 and h6.
64 // kingAttackersCount[color] is the number of pieces of the given color
65 // which attack a square in the kingZone of the enemy king.
66 int kingAttackersCount[2];
68 // kingAttackersWeight[color] is the sum of the "weight" of the pieces of the
69 // given color which attack a square in the kingZone of the enemy king. The
70 // weights of the individual piece types are given by the variables
71 // QueenAttackWeight, RookAttackWeight, BishopAttackWeight and
72 // KnightAttackWeight in evaluate.cpp
73 int kingAttackersWeight[2];
75 // kingAdjacentZoneAttacksCount[color] is the number of attacks to squares
76 // directly adjacent to the king of the given color. Pieces which attack
77 // more than one square are counted multiple times. For instance, if black's
78 // king is on g8 and there's a white knight on g5, this knight adds
79 // 2 to kingAdjacentZoneAttacksCount[BLACK].
80 int kingAdjacentZoneAttacksCount[2];
83 const int Sign[2] = { 1, -1 };
85 // Evaluation grain size, must be a power of 2
86 const int GrainSize = 8;
88 // Evaluation weights, initialized from UCI options
89 enum { Mobility, PawnStructure, PassedPawns, Space, KingDangerUs, KingDangerThem };
93 #define S(mg, eg) make_score(mg, eg)
95 // Internal evaluation weights. These are applied on top of the evaluation
96 // weights read from UCI parameters. The purpose is to be able to change
97 // the evaluation weights while keeping the default values of the UCI
98 // parameters at 100, which looks prettier.
100 // Values modified by Joona Kiiski
101 const Score WeightsInternal[] = {
102 S(248, 271), S(233, 201), S(252, 259), S(46, 0), S(247, 0), S(259, 0)
105 // MobilityBonus[PieceType][attacked] contains mobility bonuses for middle and
106 // end game, indexed by piece type and number of attacked squares not occupied
107 // by friendly pieces.
108 const Score MobilityBonus[][32] = {
110 { S(-38,-33), S(-25,-23), S(-12,-13), S( 0, -3), S(12, 7), S(25, 17), // Knights
111 S( 31, 22), S( 38, 27), S( 38, 27) },
112 { S(-25,-30), S(-11,-16), S( 3, -2), S(17, 12), S(31, 26), S(45, 40), // Bishops
113 S( 57, 52), S( 65, 60), S( 71, 65), S(74, 69), S(76, 71), S(78, 73),
114 S( 79, 74), S( 80, 75), S( 81, 76), S(81, 76) },
115 { S(-20,-36), S(-14,-19), S( -8, -3), S(-2, 13), S( 4, 29), S(10, 46), // Rooks
116 S( 14, 62), S( 19, 79), S( 23, 95), S(26,106), S(27,111), S(28,114),
117 S( 29,116), S( 30,117), S( 31,118), S(32,118) },
118 { S(-10,-18), S( -8,-13), S( -6, -7), S(-3, -2), S(-1, 3), S( 1, 8), // Queens
119 S( 3, 13), S( 5, 19), S( 8, 23), S(10, 27), S(12, 32), S(15, 34),
120 S( 16, 35), S( 17, 35), S( 18, 35), S(20, 35), S(20, 35), S(20, 35),
121 S( 20, 35), S( 20, 35), S( 20, 35), S(20, 35), S(20, 35), S(20, 35),
122 S( 20, 35), S( 20, 35), S( 20, 35), S(20, 35), S(20, 35), S(20, 35),
123 S( 20, 35), S( 20, 35) }
126 // OutpostBonus[PieceType][Square] contains outpost bonuses of knights and
127 // bishops, indexed by piece type and square (from white's point of view).
128 const Value OutpostBonus[][64] = {
131 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // Knights
132 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0),
133 V(0), V(0), V(4), V(8), V(8), V(4), V(0), V(0),
134 V(0), V(4),V(17),V(26),V(26),V(17), V(4), V(0),
135 V(0), V(8),V(26),V(35),V(35),V(26), V(8), V(0),
136 V(0), V(4),V(17),V(17),V(17),V(17), V(4), V(0),
137 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0),
138 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0) },
140 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // Bishops
141 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0),
142 V(0), V(0), V(5), V(5), V(5), V(5), V(0), V(0),
143 V(0), V(5),V(10),V(10),V(10),V(10), V(5), V(0),
144 V(0),V(10),V(21),V(21),V(21),V(21),V(10), V(0),
145 V(0), V(5), V(8), V(8), V(8), V(8), V(5), V(0),
146 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0),
147 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0) }
150 // ThreatBonus[attacking][attacked] contains threat bonuses according to
151 // which piece type attacks which one.
152 const Score ThreatBonus[][8] = {
154 { S(0, 0), S( 7, 39), S( 0, 0), S(24, 49), S(41,100), S(41,100) }, // KNIGHT
155 { S(0, 0), S( 7, 39), S(24, 49), S( 0, 0), S(41,100), S(41,100) }, // BISHOP
156 { S(0, 0), S(-1, 29), S(15, 49), S(15, 49), S( 0, 0), S(24, 49) }, // ROOK
157 { S(0, 0), S(15, 39), S(15, 39), S(15, 39), S(15, 39), S( 0, 0) } // QUEEN
160 // ThreatedByPawnPenalty[PieceType] contains a penalty according to which
161 // piece type is attacked by an enemy pawn.
162 const Score ThreatedByPawnPenalty[] = {
163 S(0, 0), S(0, 0), S(56, 70), S(56, 70), S(76, 99), S(86, 118)
168 // Rooks and queens on the 7th rank (modified by Joona Kiiski)
169 const Score RookOn7thBonus = make_score(47, 98);
170 const Score QueenOn7thBonus = make_score(27, 54);
172 // Rooks on open files (modified by Joona Kiiski)
173 const Score RookOpenFileBonus = make_score(43, 43);
174 const Score RookHalfOpenFileBonus = make_score(19, 19);
176 // Penalty for rooks trapped inside a friendly king which has lost the
178 const Value TrappedRookPenalty = Value(180);
180 // The SpaceMask[Color] contains the area of the board which is considered
181 // by the space evaluation. In the middle game, each side is given a bonus
182 // based on how many squares inside this area are safe and available for
183 // friendly minor pieces.
184 const Bitboard SpaceMask[2] = {
185 (1ULL << SQ_C2) | (1ULL << SQ_D2) | (1ULL << SQ_E2) | (1ULL << SQ_F2) |
186 (1ULL << SQ_C3) | (1ULL << SQ_D3) | (1ULL << SQ_E3) | (1ULL << SQ_F3) |
187 (1ULL << SQ_C4) | (1ULL << SQ_D4) | (1ULL << SQ_E4) | (1ULL << SQ_F4),
188 (1ULL << SQ_C7) | (1ULL << SQ_D7) | (1ULL << SQ_E7) | (1ULL << SQ_F7) |
189 (1ULL << SQ_C6) | (1ULL << SQ_D6) | (1ULL << SQ_E6) | (1ULL << SQ_F6) |
190 (1ULL << SQ_C5) | (1ULL << SQ_D5) | (1ULL << SQ_E5) | (1ULL << SQ_F5)
193 // King danger constants and variables. The king danger scores are taken
194 // from the KingDangerTable[]. Various little "meta-bonuses" measuring
195 // the strength of the enemy attack are added up into an integer, which
196 // is used as an index to KingDangerTable[].
198 // KingAttackWeights[PieceType] contains king attack weights by piece type
199 const int KingAttackWeights[] = { 0, 0, 2, 2, 3, 5 };
201 // Bonuses for enemy's safe checks
202 const int QueenContactCheckBonus = 3;
203 const int QueenCheckBonus = 2;
204 const int RookCheckBonus = 1;
205 const int BishopCheckBonus = 1;
206 const int KnightCheckBonus = 1;
208 // InitKingDanger[Square] contains penalties based on the position of the
209 // defending king, indexed by king's square (from white's point of view).
210 const int InitKingDanger[] = {
211 2, 0, 2, 5, 5, 2, 0, 2,
212 2, 2, 4, 8, 8, 4, 2, 2,
213 7, 10, 12, 12, 12, 12, 10, 7,
214 15, 15, 15, 15, 15, 15, 15, 15,
215 15, 15, 15, 15, 15, 15, 15, 15,
216 15, 15, 15, 15, 15, 15, 15, 15,
217 15, 15, 15, 15, 15, 15, 15, 15,
218 15, 15, 15, 15, 15, 15, 15, 15
221 // KingDangerTable[Color][attackUnits] contains the actual king danger
222 // weighted scores, indexed by color and by a calculated integer number.
223 Score KingDangerTable[2][128];
225 // Pawn and material hash tables, indexed by the current thread id.
226 // Note that they will be initialized at 0 being global variables.
227 MaterialInfoTable* MaterialTable[MAX_THREADS];
228 PawnInfoTable* PawnTable[MAX_THREADS];
230 // Function prototypes
231 template<bool HasPopCnt>
232 Value do_evaluate(const Position& pos, Value margins[]);
234 template<Color Us, bool HasPopCnt>
235 void init_attack_tables(const Position& pos, EvalInfo& ei);
237 template<Color Us, bool HasPopCnt>
238 Score evaluate_pieces_of_color(const Position& pos, EvalInfo& ei);
240 template<Color Us, bool HasPopCnt>
241 void evaluate_king(const Position& pos, EvalInfo& ei, Value margins[]);
244 void evaluate_threats(const Position& pos, EvalInfo& ei);
246 template<Color Us, bool HasPopCnt>
247 int evaluate_space(const Position& pos, EvalInfo& ei);
250 void evaluate_passed_pawns(const Position& pos, EvalInfo& ei);
252 inline Score apply_weight(Score v, Score weight);
253 Value scale_by_game_phase(const Score& v, Phase ph, const ScaleFactor sf[]);
254 Score weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight);
264 /// Prefetches in pawn hash tables
266 void prefetchPawn(Key key, int threadID) {
268 PawnTable[threadID]->prefetch(key);
271 /// evaluate() is the main evaluation function. It always computes two
272 /// values, an endgame score and a middle game score, and interpolates
273 /// between them based on the remaining material.
274 Value evaluate(const Position& pos, Value margins[]) {
276 return CpuHasPOPCNT ? do_evaluate<true>(pos, margins)
277 : do_evaluate<false>(pos, margins);
282 template<bool HasPopCnt>
283 Value do_evaluate(const Position& pos, Value margins[]) {
286 ScaleFactor factor[2];
290 assert(pos.thread() >= 0 && pos.thread() < MAX_THREADS);
291 assert(!pos.is_check());
293 // Initialize by reading the incrementally updated scores included in the
294 // position object (material + piece square tables).
295 ei.value = pos.value();
297 // margins[color] stores the uncertainty estimation of position's evaluation
298 // and typically is used by the search for pruning decisions.
299 margins[WHITE] = margins[BLACK] = VALUE_ZERO;
301 // Probe the material hash table
302 MaterialInfo* mi = MaterialTable[pos.thread()]->get_material_info(pos);
303 ei.value += mi->material_value();
305 // If we have a specialized evaluation function for the current material
306 // configuration, call it and return.
307 if (mi->specialized_eval_exists())
308 return mi->evaluate(pos);
310 // After get_material_info() call that modifies them
311 factor[WHITE] = mi->scale_factor(pos, WHITE);
312 factor[BLACK] = mi->scale_factor(pos, BLACK);
314 // Probe the pawn hash table
315 ei.pi = PawnTable[pos.thread()]->get_pawn_info(pos);
316 ei.value += apply_weight(ei.pi->pawns_value(), Weights[PawnStructure]);
318 // Initialize attack bitboards with pawns evaluation
319 init_attack_tables<WHITE, HasPopCnt>(pos, ei);
320 init_attack_tables<BLACK, HasPopCnt>(pos, ei);
322 // Evaluate pieces and mobility
323 mobility = evaluate_pieces_of_color<WHITE, HasPopCnt>(pos, ei)
324 - evaluate_pieces_of_color<BLACK, HasPopCnt>(pos, ei);
325 ei.value += apply_weight(mobility, Weights[Mobility]);
327 // Kings. Kings are evaluated after all other pieces for both sides,
328 // because we need complete attack information for all pieces when computing
329 // the king safety evaluation.
330 evaluate_king<WHITE, HasPopCnt>(pos, ei, margins);
331 evaluate_king<BLACK, HasPopCnt>(pos, ei, margins);
333 // Evaluate tactical threats, we need full attack info including king
334 evaluate_threats<WHITE>(pos, ei);
335 evaluate_threats<BLACK>(pos, ei);
337 // Evaluate passed pawns, we need full attack info including king
338 evaluate_passed_pawns<WHITE>(pos, ei);
339 evaluate_passed_pawns<BLACK>(pos, ei);
341 Phase phase = mi->game_phase();
343 // Middle-game specific evaluation terms
344 if (phase > PHASE_ENDGAME)
346 // Evaluate pawn storms in positions with opposite castling
347 if ( square_file(pos.king_square(WHITE)) >= FILE_E
348 && square_file(pos.king_square(BLACK)) <= FILE_D)
350 ei.value += make_score(ei.pi->queenside_storm_value(WHITE) - ei.pi->kingside_storm_value(BLACK), 0);
352 else if ( square_file(pos.king_square(WHITE)) <= FILE_D
353 && square_file(pos.king_square(BLACK)) >= FILE_E)
355 ei.value += make_score(ei.pi->kingside_storm_value(WHITE) - ei.pi->queenside_storm_value(BLACK), 0);
357 // Evaluate space for both sides
358 if (mi->space_weight() > 0)
360 int s = evaluate_space<WHITE, HasPopCnt>(pos, ei) - evaluate_space<BLACK, HasPopCnt>(pos, ei);
361 ei.value += apply_weight(make_score(s * mi->space_weight(), 0), Weights[Space]);
365 // If we don't already have an unusual scale factor, check for opposite
366 // colored bishop endgames, and use a lower scale for those
367 if ( phase < PHASE_MIDGAME
368 && pos.opposite_colored_bishops()
369 && ( (factor[WHITE] == SCALE_FACTOR_NORMAL && eg_value(ei.value) > VALUE_ZERO)
370 || (factor[BLACK] == SCALE_FACTOR_NORMAL && eg_value(ei.value) < VALUE_ZERO)))
374 // Only the two bishops ?
375 if ( pos.non_pawn_material(WHITE) == BishopValueMidgame
376 && pos.non_pawn_material(BLACK) == BishopValueMidgame)
378 // Check for KBP vs KB with only a single pawn that is almost
379 // certainly a draw or at least two pawns.
380 bool one_pawn = (pos.piece_count(WHITE, PAWN) + pos.piece_count(BLACK, PAWN) == 1);
381 sf = one_pawn ? ScaleFactor(8) : ScaleFactor(32);
384 // Endgame with opposite-colored bishops, but also other pieces. Still
385 // a bit drawish, but not as drawish as with only the two bishops.
386 sf = ScaleFactor(50);
388 if (factor[WHITE] == SCALE_FACTOR_NORMAL)
390 if (factor[BLACK] == SCALE_FACTOR_NORMAL)
394 // Interpolate between the middle game and the endgame score
395 return Sign[pos.side_to_move()] * scale_by_game_phase(ei.value, phase, factor);
400 /// init_eval() initializes various tables used by the evaluation function
402 void init_eval(int threads) {
404 assert(threads <= MAX_THREADS);
406 for (int i = 0; i < MAX_THREADS; i++)
411 delete MaterialTable[i];
413 MaterialTable[i] = NULL;
417 PawnTable[i] = new PawnInfoTable();
418 if (!MaterialTable[i])
419 MaterialTable[i] = new MaterialInfoTable();
424 /// quit_eval() releases heap-allocated memory at program termination
428 for (int i = 0; i < MAX_THREADS; i++)
431 delete MaterialTable[i];
433 MaterialTable[i] = NULL;
438 /// read_weights() reads evaluation weights from the corresponding UCI parameters
440 void read_weights(Color us) {
442 // King safety is asymmetrical. Our king danger level is weighted by
443 // "Cowardice" UCI parameter, instead the opponent one by "Aggressiveness".
444 const int kingDangerUs = (us == WHITE ? KingDangerUs : KingDangerThem);
445 const int kingDangerThem = (us == WHITE ? KingDangerThem : KingDangerUs);
447 Weights[Mobility] = weight_option("Mobility (Middle Game)", "Mobility (Endgame)", WeightsInternal[Mobility]);
448 Weights[PawnStructure] = weight_option("Pawn Structure (Middle Game)", "Pawn Structure (Endgame)", WeightsInternal[PawnStructure]);
449 Weights[PassedPawns] = weight_option("Passed Pawns (Middle Game)", "Passed Pawns (Endgame)", WeightsInternal[PassedPawns]);
450 Weights[Space] = weight_option("Space", "Space", WeightsInternal[Space]);
451 Weights[kingDangerUs] = weight_option("Cowardice", "Cowardice", WeightsInternal[KingDangerUs]);
452 Weights[kingDangerThem] = weight_option("Aggressiveness", "Aggressiveness", WeightsInternal[KingDangerThem]);
454 // If running in analysis mode, make sure we use symmetrical king safety. We do this
455 // by replacing both Weights[kingDangerUs] and Weights[kingDangerThem] by their average.
456 if (get_option_value_bool("UCI_AnalyseMode"))
457 Weights[kingDangerUs] = Weights[kingDangerThem] = (Weights[kingDangerUs] + Weights[kingDangerThem]) / 2;
465 // init_attack_tables() initializes king bitboards for both sides adding
466 // pawn attacks. To be done before other evaluations.
468 template<Color Us, bool HasPopCnt>
469 void init_attack_tables(const Position& pos, EvalInfo& ei) {
471 const Color Them = (Us == WHITE ? BLACK : WHITE);
473 Bitboard b = ei.attackedBy[Them][KING] = pos.attacks_from<KING>(pos.king_square(Them));
474 ei.kingZone[Us] = (b | (Us == WHITE ? b >> 8 : b << 8));
475 ei.attackedBy[Us][PAWN] = ei.pi->pawn_attacks(Us);
476 b &= ei.attackedBy[Us][PAWN];
477 ei.kingAttackersCount[Us] = b ? count_1s_max_15<HasPopCnt>(b) / 2 : 0;
478 ei.kingAdjacentZoneAttacksCount[Us] = ei.kingAttackersWeight[Us] = 0;
482 // evaluate_outposts() evaluates bishop and knight outposts squares
484 template<PieceType Piece, Color Us>
485 void evaluate_outposts(const Position& pos, EvalInfo& ei, Square s) {
487 const Color Them = (Us == WHITE ? BLACK : WHITE);
489 assert (Piece == BISHOP || Piece == KNIGHT);
491 // Initial bonus based on square
492 Value bonus = OutpostBonus[Piece == BISHOP][relative_square(Us, s)];
494 // Increase bonus if supported by pawn, especially if the opponent has
495 // no minor piece which can exchange the outpost piece
496 if (bonus && bit_is_set(ei.attackedBy[Us][PAWN], s))
498 if ( pos.pieces(KNIGHT, Them) == EmptyBoardBB
499 && (SquaresByColorBB[square_color(s)] & pos.pieces(BISHOP, Them)) == EmptyBoardBB)
500 bonus += bonus + bonus / 2;
504 ei.value += Sign[Us] * make_score(bonus, bonus);
508 // evaluate_pieces<>() assigns bonuses and penalties to the pieces of a given color
510 template<PieceType Piece, Color Us, bool HasPopCnt>
511 Score evaluate_pieces(const Position& pos, EvalInfo& ei, Bitboard no_mob_area) {
517 Score mobility = SCORE_ZERO;
519 const Color Them = (Us == WHITE ? BLACK : WHITE);
520 const Square* ptr = pos.piece_list_begin(Us, Piece);
522 ei.attackedBy[Us][Piece] = 0;
524 while ((s = *ptr++) != SQ_NONE)
526 // Find attacked squares, including x-ray attacks for bishops and rooks
527 if (Piece == KNIGHT || Piece == QUEEN)
528 b = pos.attacks_from<Piece>(s);
529 else if (Piece == BISHOP)
530 b = bishop_attacks_bb(s, pos.occupied_squares() & ~pos.pieces(QUEEN, Us));
531 else if (Piece == ROOK)
532 b = rook_attacks_bb(s, pos.occupied_squares() & ~pos.pieces(ROOK, QUEEN, Us));
536 // Update attack info
537 ei.attackedBy[Us][Piece] |= b;
540 if (b & ei.kingZone[Us])
542 ei.kingAttackersCount[Us]++;
543 ei.kingAttackersWeight[Us] += KingAttackWeights[Piece];
544 Bitboard bb = (b & ei.attackedBy[Them][KING]);
546 ei.kingAdjacentZoneAttacksCount[Us] += count_1s_max_15<HasPopCnt>(bb);
550 mob = (Piece != QUEEN ? count_1s_max_15<HasPopCnt>(b & no_mob_area)
551 : count_1s<HasPopCnt>(b & no_mob_area));
553 mobility += MobilityBonus[Piece][mob];
555 // Decrease score if we are attacked by an enemy pawn. Remaining part
556 // of threat evaluation must be done later when we have full attack info.
557 if (bit_is_set(ei.attackedBy[Them][PAWN], s))
558 ei.value -= Sign[Us] * ThreatedByPawnPenalty[Piece];
560 // Bishop and knight outposts squares
561 if ((Piece == BISHOP || Piece == KNIGHT) && pos.square_is_weak(s, Us))
562 evaluate_outposts<Piece, Us>(pos, ei, s);
564 // Queen or rook on 7th rank
565 if ( (Piece == ROOK || Piece == QUEEN)
566 && relative_rank(Us, s) == RANK_7
567 && relative_rank(Us, pos.king_square(Them)) == RANK_8)
569 ei.value += Sign[Us] * (Piece == ROOK ? RookOn7thBonus : QueenOn7thBonus);
572 // Special extra evaluation for rooks
575 // Open and half-open files
577 if (ei.pi->file_is_half_open(Us, f))
579 if (ei.pi->file_is_half_open(Them, f))
580 ei.value += Sign[Us] * RookOpenFileBonus;
582 ei.value += Sign[Us] * RookHalfOpenFileBonus;
585 // Penalize rooks which are trapped inside a king. Penalize more if
586 // king has lost right to castle.
587 if (mob > 6 || ei.pi->file_is_half_open(Us, f))
590 ksq = pos.king_square(Us);
592 if ( square_file(ksq) >= FILE_E
593 && square_file(s) > square_file(ksq)
594 && (relative_rank(Us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
596 // Is there a half-open file between the king and the edge of the board?
597 if (!ei.pi->has_open_file_to_right(Us, square_file(ksq)))
598 ei.value -= Sign[Us] * make_score(pos.can_castle(Us) ? (TrappedRookPenalty - mob * 16) / 2
599 : (TrappedRookPenalty - mob * 16), 0);
601 else if ( square_file(ksq) <= FILE_D
602 && square_file(s) < square_file(ksq)
603 && (relative_rank(Us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
605 // Is there a half-open file between the king and the edge of the board?
606 if (!ei.pi->has_open_file_to_left(Us, square_file(ksq)))
607 ei.value -= Sign[Us] * make_score(pos.can_castle(Us) ? (TrappedRookPenalty - mob * 16) / 2
608 : (TrappedRookPenalty - mob * 16), 0);
616 // evaluate_threats<>() assigns bonuses according to the type of attacking piece
617 // and the type of attacked one.
620 void evaluate_threats(const Position& pos, EvalInfo& ei) {
622 const Color Them = (Us == WHITE ? BLACK : WHITE);
625 Score bonus = SCORE_ZERO;
627 // Enemy pieces not defended by a pawn and under our attack
628 Bitboard weakEnemies = pos.pieces_of_color(Them)
629 & ~ei.attackedBy[Them][PAWN]
630 & ei.attackedBy[Us][0];
634 // Add bonus according to type of attacked enemy pieces and to the
635 // type of attacking piece, from knights to queens. Kings are not
636 // considered because are already special handled in king evaluation.
637 for (PieceType pt1 = KNIGHT; pt1 < KING; pt1++)
639 b = ei.attackedBy[Us][pt1] & weakEnemies;
641 for (PieceType pt2 = PAWN; pt2 < KING; pt2++)
642 if (b & pos.pieces(pt2))
643 bonus += ThreatBonus[pt1][pt2];
645 ei.value += Sign[Us] * bonus;
649 // evaluate_pieces_of_color<>() assigns bonuses and penalties to all the
650 // pieces of a given color.
652 template<Color Us, bool HasPopCnt>
653 Score evaluate_pieces_of_color(const Position& pos, EvalInfo& ei) {
655 const Color Them = (Us == WHITE ? BLACK : WHITE);
657 Score mobility = SCORE_ZERO;
659 // Do not include in mobility squares protected by enemy pawns or occupied by our pieces
660 const Bitboard no_mob_area = ~(ei.attackedBy[Them][PAWN] | pos.pieces_of_color(Us));
662 mobility += evaluate_pieces<KNIGHT, Us, HasPopCnt>(pos, ei, no_mob_area);
663 mobility += evaluate_pieces<BISHOP, Us, HasPopCnt>(pos, ei, no_mob_area);
664 mobility += evaluate_pieces<ROOK, Us, HasPopCnt>(pos, ei, no_mob_area);
665 mobility += evaluate_pieces<QUEEN, Us, HasPopCnt>(pos, ei, no_mob_area);
667 // Sum up all attacked squares
668 ei.attackedBy[Us][0] = ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
669 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
670 | ei.attackedBy[Us][QUEEN] | ei.attackedBy[Us][KING];
675 // evaluate_king<>() assigns bonuses and penalties to a king of a given color
677 template<Color Us, bool HasPopCnt>
678 void evaluate_king(const Position& pos, EvalInfo& ei, Value margins[]) {
680 const Color Them = (Us == WHITE ? BLACK : WHITE);
682 Bitboard undefended, b, b1, b2, safe;
685 const Square ksq = pos.king_square(Us);
688 ei.value += Sign[Us] * ei.pi->king_shelter(pos, Us, ksq);
690 // King safety. This is quite complicated, and is almost certainly far
691 // from optimally tuned.
692 if ( pos.piece_count(Them, QUEEN) >= 1
693 && ei.kingAttackersCount[Them] >= 2
694 && pos.non_pawn_material(Them) >= QueenValueMidgame + RookValueMidgame
695 && ei.kingAdjacentZoneAttacksCount[Them])
697 // Is it the attackers turn to move?
698 sente = (Them == pos.side_to_move());
700 // Find the attacked squares around the king which has no defenders
701 // apart from the king itself
702 undefended = ei.attackedBy[Them][0] & ei.attackedBy[Us][KING];
703 undefended &= ~( ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
704 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
705 | ei.attackedBy[Us][QUEEN]);
707 // Initialize the 'attackUnits' variable, which is used later on as an
708 // index to the KingDangerTable[] array. The initial value is based on
709 // the number and types of the enemy's attacking pieces, the number of
710 // attacked and undefended squares around our king, the square of the
711 // king, and the quality of the pawn shelter.
712 attackUnits = Min(25, (ei.kingAttackersCount[Them] * ei.kingAttackersWeight[Them]) / 2)
713 + 3 * (ei.kingAdjacentZoneAttacksCount[Them] + count_1s_max_15<HasPopCnt>(undefended))
714 + InitKingDanger[relative_square(Us, ksq)]
715 - mg_value(ei.pi->king_shelter(pos, Us, ksq)) / 32;
717 // Analyse enemy's safe queen contact checks. First find undefended
718 // squares around the king attacked by enemy queen...
719 b = undefended & ei.attackedBy[Them][QUEEN] & ~pos.pieces_of_color(Them);
722 // ...then remove squares not supported by another enemy piece
723 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
724 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][ROOK]);
726 attackUnits += QueenContactCheckBonus * count_1s_max_15<HasPopCnt>(b) * (sente ? 2 : 1);
729 // Analyse enemy's safe distance checks for sliders and knights
730 safe = ~(pos.pieces_of_color(Them) | ei.attackedBy[Us][0]);
732 b1 = pos.attacks_from<ROOK>(ksq) & safe;
733 b2 = pos.attacks_from<BISHOP>(ksq) & safe;
735 // Enemy queen safe checks
736 b = (b1 | b2) & ei.attackedBy[Them][QUEEN];
738 attackUnits += QueenCheckBonus * count_1s_max_15<HasPopCnt>(b);
740 // Enemy rooks safe checks
741 b = b1 & ei.attackedBy[Them][ROOK];
743 attackUnits += RookCheckBonus * count_1s_max_15<HasPopCnt>(b);
745 // Enemy bishops safe checks
746 b = b2 & ei.attackedBy[Them][BISHOP];
748 attackUnits += BishopCheckBonus * count_1s_max_15<HasPopCnt>(b);
750 // Enemy knights safe checks
751 b = pos.attacks_from<KNIGHT>(ksq) & ei.attackedBy[Them][KNIGHT] & safe;
753 attackUnits += KnightCheckBonus * count_1s_max_15<HasPopCnt>(b);
755 // To index KingDangerTable[] attackUnits must be in [0, 99] range
756 attackUnits = Min(99, Max(0, attackUnits));
758 // Finally, extract the king danger score from the KingDangerTable[]
759 // array and subtract the score from evaluation. Set also ei.margin[]
760 // value that will be used for pruning because this value can sometimes
761 // be very big, and so capturing a single attacking piece can therefore
762 // result in a score change far bigger than the value of the captured piece.
763 ei.value -= Sign[Us] * KingDangerTable[Us][attackUnits];
764 margins[Us] += mg_value(KingDangerTable[Us][attackUnits]);
769 // evaluate_passed_pawns<>() evaluates the passed pawns of the given color
772 void evaluate_passed_pawns(const Position& pos, EvalInfo& ei) {
774 const Color Them = (Us == WHITE ? BLACK : WHITE);
776 Score bonus = SCORE_ZERO;
777 Bitboard squaresToQueen, defendedSquares, unsafeSquares, supportingPawns;
778 Bitboard b = ei.pi->passed_pawns(Us);
784 Square s = pop_1st_bit(&b);
786 assert(pos.pawn_is_passed(Us, s));
788 int r = int(relative_rank(Us, s) - RANK_2);
789 int tr = r * (r - 1);
791 // Base bonus based on rank
792 Value mbonus = Value(20 * tr);
793 Value ebonus = Value(10 + r * r * 10);
797 Square blockSq = s + pawn_push(Us);
799 // Adjust bonus based on kings proximity
800 ebonus -= Value(square_distance(pos.king_square(Us), blockSq) * 3 * tr);
801 ebonus -= Value(square_distance(pos.king_square(Us), blockSq + pawn_push(Us)) * 1 * tr);
802 ebonus += Value(square_distance(pos.king_square(Them), blockSq) * 6 * tr);
804 // If the pawn is free to advance, increase bonus
805 if (pos.square_is_empty(blockSq))
807 squaresToQueen = squares_in_front_of(Us, s);
808 defendedSquares = squaresToQueen & ei.attackedBy[Us][0];
810 // If there is an enemy rook or queen attacking the pawn from behind,
811 // add all X-ray attacks by the rook or queen. Otherwise consider only
812 // the squares in the pawn's path attacked or occupied by the enemy.
813 if ( (squares_behind(Us, s) & pos.pieces(ROOK, QUEEN, Them))
814 && (squares_behind(Us, s) & pos.pieces(ROOK, QUEEN, Them) & pos.attacks_from<ROOK>(s)))
815 unsafeSquares = squaresToQueen;
817 unsafeSquares = squaresToQueen & (ei.attackedBy[Them][0] | pos.pieces_of_color(Them));
819 // If there aren't enemy attacks or pieces along the path to queen give
820 // huge bonus. Even bigger if we protect the pawn's path.
822 ebonus += Value(tr * (squaresToQueen == defendedSquares ? 17 : 15));
824 // OK, there are enemy attacks or pieces (but not pawns). Are those
825 // squares which are attacked by the enemy also attacked by us ?
826 // If yes, big bonus (but smaller than when there are no enemy attacks),
827 // if no, somewhat smaller bonus.
828 ebonus += Value(tr * ((unsafeSquares & defendedSquares) == unsafeSquares ? 13 : 8));
830 // At last, add a small bonus when there are no *friendly* pieces
831 // in the pawn's path.
832 if (!(squaresToQueen & pos.pieces_of_color(Us)))
837 // Increase the bonus if the passed pawn is supported by a friendly pawn
838 // on the same rank and a bit smaller if it's on the previous rank.
839 supportingPawns = pos.pieces(PAWN, Us) & neighboring_files_bb(s);
840 if (supportingPawns & rank_bb(s))
841 ebonus += Value(r * 20);
842 else if (supportingPawns & rank_bb(s - pawn_push(Us)))
843 ebonus += Value(r * 12);
845 // Rook pawns are a special case: They are sometimes worse, and
846 // sometimes better than other passed pawns. It is difficult to find
847 // good rules for determining whether they are good or bad. For now,
848 // we try the following: Increase the value for rook pawns if the
849 // other side has no pieces apart from a knight, and decrease the
850 // value if the other side has a rook or queen.
851 if (square_file(s) == FILE_A || square_file(s) == FILE_H)
853 if (pos.non_pawn_material(Them) <= KnightValueMidgame)
854 ebonus += ebonus / 4;
855 else if (pos.pieces(ROOK, QUEEN, Them))
856 ebonus -= ebonus / 4;
858 bonus += make_score(mbonus, ebonus);
862 // Add the scores to the middle game and endgame eval
863 ei.value += Sign[Us] * apply_weight(bonus, Weights[PassedPawns]);
867 // evaluate_space() computes the space evaluation for a given side. The
868 // space evaluation is a simple bonus based on the number of safe squares
869 // available for minor pieces on the central four files on ranks 2--4. Safe
870 // squares one, two or three squares behind a friendly pawn are counted
871 // twice. Finally, the space bonus is scaled by a weight taken from the
872 // material hash table.
873 template<Color Us, bool HasPopCnt>
874 int evaluate_space(const Position& pos, EvalInfo& ei) {
876 const Color Them = (Us == WHITE ? BLACK : WHITE);
878 // Find the safe squares for our pieces inside the area defined by
879 // SpaceMask[us]. A square is unsafe if it is attacked by an enemy
880 // pawn, or if it is undefended and attacked by an enemy piece.
881 Bitboard safe = SpaceMask[Us]
882 & ~pos.pieces(PAWN, Us)
883 & ~ei.attackedBy[Them][PAWN]
884 & (ei.attackedBy[Us][0] | ~ei.attackedBy[Them][0]);
886 // Find all squares which are at most three squares behind some friendly pawn
887 Bitboard behind = pos.pieces(PAWN, Us);
888 behind |= (Us == WHITE ? behind >> 8 : behind << 8);
889 behind |= (Us == WHITE ? behind >> 16 : behind << 16);
891 return count_1s_max_15<HasPopCnt>(safe) + count_1s_max_15<HasPopCnt>(behind & safe);
895 // apply_weight() applies an evaluation weight to a value trying to prevent overflow
897 inline Score apply_weight(Score v, Score w) {
898 return make_score((int(mg_value(v)) * mg_value(w)) / 0x100, (int(eg_value(v)) * eg_value(w)) / 0x100);
902 // scale_by_game_phase() interpolates between a middle game and an endgame score,
903 // based on game phase. It also scales the return value by a ScaleFactor array.
905 Value scale_by_game_phase(const Score& v, Phase ph, const ScaleFactor sf[]) {
907 assert(mg_value(v) > -VALUE_INFINITE && mg_value(v) < VALUE_INFINITE);
908 assert(eg_value(v) > -VALUE_INFINITE && eg_value(v) < VALUE_INFINITE);
909 assert(ph >= PHASE_ENDGAME && ph <= PHASE_MIDGAME);
911 Value eg = eg_value(v);
912 ScaleFactor f = sf[eg > VALUE_ZERO ? WHITE : BLACK];
913 Value ev = Value((eg * int(f)) / SCALE_FACTOR_NORMAL);
915 int result = (mg_value(v) * int(ph) + ev * int(128 - ph)) / 128;
916 return Value(result & ~(GrainSize - 1));
920 // weight_option() computes the value of an evaluation weight, by combining
921 // two UCI-configurable weights (midgame and endgame) with an internal weight.
923 Score weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight) {
925 // Scale option value from 100 to 256
926 int mg = get_option_value_int(mgOpt) * 256 / 100;
927 int eg = get_option_value_int(egOpt) * 256 / 100;
929 return apply_weight(make_score(mg, eg), internalWeight);
932 // init_safety() initizes the king safety evaluation, based on UCI
933 // parameters. It is called from read_weights().
937 const Value MaxSlope = Value(30);
938 const Value Peak = Value(1280);
941 // First setup the base table
942 for (int i = 0; i < 100; i++)
944 t[i] = Value(int(0.4 * i * i));
947 t[i] = Min(t[i], t[i - 1] + MaxSlope);
949 t[i] = Min(t[i], Peak);
952 // Then apply the weights and get the final KingDangerTable[] array
953 for (Color c = WHITE; c <= BLACK; c++)
954 for (int i = 0; i < 100; i++)
955 KingDangerTable[c][i] = apply_weight(make_score(t[i], 0), Weights[KingDangerUs + c]);