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 // Pointer to pawn hash table entry
48 // attackedBy[color][piece type] is a bitboard representing all squares
49 // attacked by a given color and piece type, attackedBy[color][0] contains
50 // all squares attacked by the given color.
51 Bitboard attackedBy[2][8];
53 // kingZone[color] is the zone around the enemy king which is considered
54 // by the king safety evaluation. This consists of the squares directly
55 // adjacent to the king, and the three (or two, for a king on an edge file)
56 // squares two ranks in front of the king. For instance, if black's king
57 // is on g8, kingZone[WHITE] is a bitboard containing the squares f8, h8,
58 // f7, g7, h7, f6, g6 and h6.
61 // kingAttackersCount[color] is the number of pieces of the given color
62 // which attack a square in the kingZone of the enemy king.
63 int kingAttackersCount[2];
65 // kingAttackersWeight[color] is the sum of the "weight" of the pieces of the
66 // given color which attack a square in the kingZone of the enemy king. The
67 // weights of the individual piece types are given by the variables
68 // QueenAttackWeight, RookAttackWeight, BishopAttackWeight and
69 // KnightAttackWeight in evaluate.cpp
70 int kingAttackersWeight[2];
72 // kingAdjacentZoneAttacksCount[color] is the number of attacks to squares
73 // directly adjacent to the king of the given color. Pieces which attack
74 // more than one square are counted multiple times. For instance, if black's
75 // king is on g8 and there's a white knight on g5, this knight adds
76 // 2 to kingAdjacentZoneAttacksCount[BLACK].
77 int kingAdjacentZoneAttacksCount[2];
80 const int Sign[2] = { 1, -1 };
82 // Evaluation grain size, must be a power of 2
83 const int GrainSize = 8;
85 // Evaluation weights, initialized from UCI options
86 enum { Mobility, PawnStructure, PassedPawns, Space, KingDangerUs, KingDangerThem };
90 #define S(mg, eg) make_score(mg, eg)
92 // Internal evaluation weights. These are applied on top of the evaluation
93 // weights read from UCI parameters. The purpose is to be able to change
94 // the evaluation weights while keeping the default values of the UCI
95 // parameters at 100, which looks prettier.
97 // Values modified by Joona Kiiski
98 const Score WeightsInternal[] = {
99 S(248, 271), S(233, 201), S(252, 259), S(46, 0), S(247, 0), S(259, 0)
102 // MobilityBonus[PieceType][attacked] contains mobility bonuses for middle and
103 // end game, indexed by piece type and number of attacked squares not occupied
104 // by friendly pieces.
105 const Score MobilityBonus[][32] = {
107 { S(-38,-33), S(-25,-23), S(-12,-13), S( 0, -3), S(12, 7), S(25, 17), // Knights
108 S( 31, 22), S( 38, 27), S( 38, 27) },
109 { S(-25,-30), S(-11,-16), S( 3, -2), S(17, 12), S(31, 26), S(45, 40), // Bishops
110 S( 57, 52), S( 65, 60), S( 71, 65), S(74, 69), S(76, 71), S(78, 73),
111 S( 79, 74), S( 80, 75), S( 81, 76), S(81, 76) },
112 { S(-20,-36), S(-14,-19), S( -8, -3), S(-2, 13), S( 4, 29), S(10, 46), // Rooks
113 S( 14, 62), S( 19, 79), S( 23, 95), S(26,106), S(27,111), S(28,114),
114 S( 29,116), S( 30,117), S( 31,118), S(32,118) },
115 { S(-10,-18), S( -8,-13), S( -6, -7), S(-3, -2), S(-1, 3), S( 1, 8), // Queens
116 S( 3, 13), S( 5, 19), S( 8, 23), S(10, 27), S(12, 32), S(15, 34),
117 S( 16, 35), S( 17, 35), S( 18, 35), S(20, 35), S(20, 35), S(20, 35),
118 S( 20, 35), S( 20, 35), S( 20, 35), S(20, 35), S(20, 35), S(20, 35),
119 S( 20, 35), S( 20, 35), S( 20, 35), S(20, 35), S(20, 35), S(20, 35),
120 S( 20, 35), S( 20, 35) }
123 // OutpostBonus[PieceType][Square] contains outpost bonuses of knights and
124 // bishops, indexed by piece type and square (from white's point of view).
125 const Value OutpostBonus[][64] = {
128 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // Knights
129 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0),
130 V(0), V(0), V(4), V(8), V(8), V(4), V(0), V(0),
131 V(0), V(4),V(17),V(26),V(26),V(17), V(4), V(0),
132 V(0), V(8),V(26),V(35),V(35),V(26), V(8), V(0),
133 V(0), V(4),V(17),V(17),V(17),V(17), V(4), V(0),
134 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0),
135 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0) },
137 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // Bishops
138 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0),
139 V(0), V(0), V(5), V(5), V(5), V(5), V(0), V(0),
140 V(0), V(5),V(10),V(10),V(10),V(10), V(5), V(0),
141 V(0),V(10),V(21),V(21),V(21),V(21),V(10), V(0),
142 V(0), V(5), V(8), V(8), V(8), V(8), V(5), V(0),
143 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0),
144 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0) }
147 // ThreatBonus[attacking][attacked] contains threat bonuses according to
148 // which piece type attacks which one.
149 const Score ThreatBonus[][8] = {
151 { S(0, 0), S( 7, 39), S( 0, 0), S(24, 49), S(41,100), S(41,100) }, // KNIGHT
152 { S(0, 0), S( 7, 39), S(24, 49), S( 0, 0), S(41,100), S(41,100) }, // BISHOP
153 { S(0, 0), S(-1, 29), S(15, 49), S(15, 49), S( 0, 0), S(24, 49) }, // ROOK
154 { S(0, 0), S(15, 39), S(15, 39), S(15, 39), S(15, 39), S( 0, 0) } // QUEEN
157 // ThreatedByPawnPenalty[PieceType] contains a penalty according to which
158 // piece type is attacked by an enemy pawn.
159 const Score ThreatedByPawnPenalty[] = {
160 S(0, 0), S(0, 0), S(56, 70), S(56, 70), S(76, 99), S(86, 118)
165 // Rooks and queens on the 7th rank (modified by Joona Kiiski)
166 const Score RookOn7thBonus = make_score(47, 98);
167 const Score QueenOn7thBonus = make_score(27, 54);
169 // Rooks on open files (modified by Joona Kiiski)
170 const Score RookOpenFileBonus = make_score(43, 43);
171 const Score RookHalfOpenFileBonus = make_score(19, 19);
173 // Penalty for rooks trapped inside a friendly king which has lost the
175 const Value TrappedRookPenalty = Value(180);
177 // The SpaceMask[Color] contains the area of the board which is considered
178 // by the space evaluation. In the middle game, each side is given a bonus
179 // based on how many squares inside this area are safe and available for
180 // friendly minor pieces.
181 const Bitboard SpaceMask[2] = {
182 (1ULL << SQ_C2) | (1ULL << SQ_D2) | (1ULL << SQ_E2) | (1ULL << SQ_F2) |
183 (1ULL << SQ_C3) | (1ULL << SQ_D3) | (1ULL << SQ_E3) | (1ULL << SQ_F3) |
184 (1ULL << SQ_C4) | (1ULL << SQ_D4) | (1ULL << SQ_E4) | (1ULL << SQ_F4),
185 (1ULL << SQ_C7) | (1ULL << SQ_D7) | (1ULL << SQ_E7) | (1ULL << SQ_F7) |
186 (1ULL << SQ_C6) | (1ULL << SQ_D6) | (1ULL << SQ_E6) | (1ULL << SQ_F6) |
187 (1ULL << SQ_C5) | (1ULL << SQ_D5) | (1ULL << SQ_E5) | (1ULL << SQ_F5)
190 // King danger constants and variables. The king danger scores are taken
191 // from the KingDangerTable[]. Various little "meta-bonuses" measuring
192 // the strength of the enemy attack are added up into an integer, which
193 // is used as an index to KingDangerTable[].
195 // KingAttackWeights[PieceType] contains king attack weights by piece type
196 const int KingAttackWeights[] = { 0, 0, 2, 2, 3, 5 };
198 // Bonuses for enemy's safe checks
199 const int QueenContactCheckBonus = 3;
200 const int QueenCheckBonus = 2;
201 const int RookCheckBonus = 1;
202 const int BishopCheckBonus = 1;
203 const int KnightCheckBonus = 1;
205 // InitKingDanger[Square] contains penalties based on the position of the
206 // defending king, indexed by king's square (from white's point of view).
207 const int InitKingDanger[] = {
208 2, 0, 2, 5, 5, 2, 0, 2,
209 2, 2, 4, 8, 8, 4, 2, 2,
210 7, 10, 12, 12, 12, 12, 10, 7,
211 15, 15, 15, 15, 15, 15, 15, 15,
212 15, 15, 15, 15, 15, 15, 15, 15,
213 15, 15, 15, 15, 15, 15, 15, 15,
214 15, 15, 15, 15, 15, 15, 15, 15,
215 15, 15, 15, 15, 15, 15, 15, 15
218 // KingDangerTable[Color][attackUnits] contains the actual king danger
219 // weighted scores, indexed by color and by a calculated integer number.
220 Score KingDangerTable[2][128];
222 // Pawn and material hash tables, indexed by the current thread id.
223 // Note that they will be initialized at 0 being global variables.
224 MaterialInfoTable* MaterialTable[MAX_THREADS];
225 PawnInfoTable* PawnTable[MAX_THREADS];
227 // Function prototypes
228 template<bool HasPopCnt>
229 Value do_evaluate(const Position& pos, Value margins[]);
231 template<Color Us, bool HasPopCnt>
232 void init_attack_tables(const Position& pos, EvalInfo& ei);
234 template<Color Us, bool HasPopCnt>
235 Score evaluate_pieces_of_color(const Position& pos, EvalInfo& ei, Score& mobility);
237 template<Color Us, bool HasPopCnt>
238 Score evaluate_king(const Position& pos, EvalInfo& ei, Value margins[]);
241 Score evaluate_threats(const Position& pos, EvalInfo& ei);
243 template<Color Us, bool HasPopCnt>
244 int evaluate_space(const Position& pos, EvalInfo& ei);
247 Score evaluate_passed_pawns(const Position& pos, EvalInfo& ei);
249 inline Score apply_weight(Score v, Score weight);
250 Value scale_by_game_phase(const Score& v, Phase ph, const ScaleFactor sf[]);
251 Score weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight);
261 /// Prefetches in pawn hash tables
263 void prefetchPawn(Key key, int threadID) {
265 PawnTable[threadID]->prefetch(key);
268 /// evaluate() is the main evaluation function. It always computes two
269 /// values, an endgame score and a middle game score, and interpolates
270 /// between them based on the remaining material.
271 Value evaluate(const Position& pos, Value margins[]) {
273 return CpuHasPOPCNT ? do_evaluate<true>(pos, margins)
274 : do_evaluate<false>(pos, margins);
279 template<bool HasPopCnt>
280 Value do_evaluate(const Position& pos, Value margins[]) {
283 ScaleFactor factor[2];
287 assert(pos.thread() >= 0 && pos.thread() < MAX_THREADS);
288 assert(!pos.is_check());
290 // Initialize by reading the incrementally updated scores included in the
291 // position object (material + piece square tables).
292 Score value = pos.value();
294 // margins[color] stores the uncertainty estimation of position's evaluation
295 // and typically is used by the search for pruning decisions.
296 margins[WHITE] = margins[BLACK] = VALUE_ZERO;
298 // Probe the material hash table
299 MaterialInfo* mi = MaterialTable[pos.thread()]->get_material_info(pos);
300 value += mi->material_value();
302 // If we have a specialized evaluation function for the current material
303 // configuration, call it and return.
304 if (mi->specialized_eval_exists())
305 return mi->evaluate(pos);
307 // After get_material_info() call that modifies them
308 factor[WHITE] = mi->scale_factor(pos, WHITE);
309 factor[BLACK] = mi->scale_factor(pos, BLACK);
311 // Probe the pawn hash table
312 ei.pi = PawnTable[pos.thread()]->get_pawn_info(pos);
313 value += apply_weight(ei.pi->pawns_value(), Weights[PawnStructure]);
315 // Initialize attack bitboards with pawns evaluation
316 init_attack_tables<WHITE, HasPopCnt>(pos, ei);
317 init_attack_tables<BLACK, HasPopCnt>(pos, ei);
319 // Evaluate pieces and mobility
320 value += evaluate_pieces_of_color<WHITE, HasPopCnt>(pos, ei, w_mob)
321 - evaluate_pieces_of_color<BLACK, HasPopCnt>(pos, ei, b_mob);
323 value += apply_weight(w_mob - b_mob, Weights[Mobility]);
325 // Evaluate kings after all other pieces for both sides, because we
326 // need complete attack information for all pieces when computing
327 // the king safety evaluation.
328 value += evaluate_king<WHITE, HasPopCnt>(pos, ei, margins)
329 - evaluate_king<BLACK, HasPopCnt>(pos, ei, margins);
331 // Evaluate tactical threats, we need full attack info including king
332 value += evaluate_threats<WHITE>(pos, ei)
333 - evaluate_threats<BLACK>(pos, ei);
335 // Evaluate passed pawns, we need full attack info including king
336 value += evaluate_passed_pawns<WHITE>(pos, ei)
337 - evaluate_passed_pawns<BLACK>(pos, ei);
339 Phase phase = mi->game_phase();
341 // Middle-game specific evaluation terms
342 if (phase > PHASE_ENDGAME)
344 // Evaluate pawn storms in positions with opposite castling
345 if ( square_file(pos.king_square(WHITE)) >= FILE_E
346 && square_file(pos.king_square(BLACK)) <= FILE_D)
348 value += make_score(ei.pi->queenside_storm_value(WHITE) - ei.pi->kingside_storm_value(BLACK), 0);
350 else if ( square_file(pos.king_square(WHITE)) <= FILE_D
351 && square_file(pos.king_square(BLACK)) >= FILE_E)
353 value += make_score(ei.pi->kingside_storm_value(WHITE) - ei.pi->queenside_storm_value(BLACK), 0);
355 // Evaluate space for both sides
356 if (mi->space_weight() > 0)
358 int s = evaluate_space<WHITE, HasPopCnt>(pos, ei) - evaluate_space<BLACK, HasPopCnt>(pos, ei);
359 value += apply_weight(make_score(s * mi->space_weight(), 0), Weights[Space]);
363 // If we don't already have an unusual scale factor, check for opposite
364 // colored bishop endgames, and use a lower scale for those
365 if ( phase < PHASE_MIDGAME
366 && pos.opposite_colored_bishops()
367 && ( (factor[WHITE] == SCALE_FACTOR_NORMAL && eg_value(value) > VALUE_ZERO)
368 || (factor[BLACK] == SCALE_FACTOR_NORMAL && eg_value(value) < VALUE_ZERO)))
372 // Only the two bishops ?
373 if ( pos.non_pawn_material(WHITE) == BishopValueMidgame
374 && pos.non_pawn_material(BLACK) == BishopValueMidgame)
376 // Check for KBP vs KB with only a single pawn that is almost
377 // certainly a draw or at least two pawns.
378 bool one_pawn = (pos.piece_count(WHITE, PAWN) + pos.piece_count(BLACK, PAWN) == 1);
379 sf = one_pawn ? ScaleFactor(8) : ScaleFactor(32);
382 // Endgame with opposite-colored bishops, but also other pieces. Still
383 // a bit drawish, but not as drawish as with only the two bishops.
384 sf = ScaleFactor(50);
386 if (factor[WHITE] == SCALE_FACTOR_NORMAL)
388 if (factor[BLACK] == SCALE_FACTOR_NORMAL)
392 // Interpolate between the middle game and the endgame score
393 return Sign[pos.side_to_move()] * scale_by_game_phase(value, phase, factor);
398 /// init_eval() initializes various tables used by the evaluation function
400 void init_eval(int threads) {
402 assert(threads <= MAX_THREADS);
404 for (int i = 0; i < MAX_THREADS; i++)
409 delete MaterialTable[i];
411 MaterialTable[i] = NULL;
415 PawnTable[i] = new PawnInfoTable();
416 if (!MaterialTable[i])
417 MaterialTable[i] = new MaterialInfoTable();
422 /// quit_eval() releases heap-allocated memory at program termination
426 for (int i = 0; i < MAX_THREADS; i++)
429 delete MaterialTable[i];
431 MaterialTable[i] = NULL;
436 /// read_weights() reads evaluation weights from the corresponding UCI parameters
438 void read_weights(Color us) {
440 // King safety is asymmetrical. Our king danger level is weighted by
441 // "Cowardice" UCI parameter, instead the opponent one by "Aggressiveness".
442 const int kingDangerUs = (us == WHITE ? KingDangerUs : KingDangerThem);
443 const int kingDangerThem = (us == WHITE ? KingDangerThem : KingDangerUs);
445 Weights[Mobility] = weight_option("Mobility (Middle Game)", "Mobility (Endgame)", WeightsInternal[Mobility]);
446 Weights[PawnStructure] = weight_option("Pawn Structure (Middle Game)", "Pawn Structure (Endgame)", WeightsInternal[PawnStructure]);
447 Weights[PassedPawns] = weight_option("Passed Pawns (Middle Game)", "Passed Pawns (Endgame)", WeightsInternal[PassedPawns]);
448 Weights[Space] = weight_option("Space", "Space", WeightsInternal[Space]);
449 Weights[kingDangerUs] = weight_option("Cowardice", "Cowardice", WeightsInternal[KingDangerUs]);
450 Weights[kingDangerThem] = weight_option("Aggressiveness", "Aggressiveness", WeightsInternal[KingDangerThem]);
452 // If running in analysis mode, make sure we use symmetrical king safety. We do this
453 // by replacing both Weights[kingDangerUs] and Weights[kingDangerThem] by their average.
454 if (get_option_value_bool("UCI_AnalyseMode"))
455 Weights[kingDangerUs] = Weights[kingDangerThem] = (Weights[kingDangerUs] + Weights[kingDangerThem]) / 2;
463 // init_attack_tables() initializes king bitboards for both sides adding
464 // pawn attacks. To be done before other evaluations.
466 template<Color Us, bool HasPopCnt>
467 void init_attack_tables(const Position& pos, EvalInfo& ei) {
469 const Color Them = (Us == WHITE ? BLACK : WHITE);
471 Bitboard b = ei.attackedBy[Them][KING] = pos.attacks_from<KING>(pos.king_square(Them));
472 ei.kingZone[Us] = (b | (Us == WHITE ? b >> 8 : b << 8));
473 ei.attackedBy[Us][PAWN] = ei.pi->pawn_attacks(Us);
474 b &= ei.attackedBy[Us][PAWN];
475 ei.kingAttackersCount[Us] = b ? count_1s_max_15<HasPopCnt>(b) / 2 : 0;
476 ei.kingAdjacentZoneAttacksCount[Us] = ei.kingAttackersWeight[Us] = 0;
480 // evaluate_outposts() evaluates bishop and knight outposts squares
482 template<PieceType Piece, Color Us>
483 Score evaluate_outposts(const Position& pos, EvalInfo& ei, Square s) {
485 const Color Them = (Us == WHITE ? BLACK : WHITE);
487 assert (Piece == BISHOP || Piece == KNIGHT);
489 // Initial bonus based on square
490 Value bonus = OutpostBonus[Piece == BISHOP][relative_square(Us, s)];
492 // Increase bonus if supported by pawn, especially if the opponent has
493 // no minor piece which can exchange the outpost piece
494 if (bonus && bit_is_set(ei.attackedBy[Us][PAWN], s))
496 if ( pos.pieces(KNIGHT, Them) == EmptyBoardBB
497 && (SquaresByColorBB[square_color(s)] & pos.pieces(BISHOP, Them)) == EmptyBoardBB)
498 bonus += bonus + bonus / 2;
502 return make_score(bonus, bonus);
506 // evaluate_pieces<>() assigns bonuses and penalties to the pieces of a given color
508 template<PieceType Piece, Color Us, bool HasPopCnt>
509 Score evaluate_pieces(const Position& pos, EvalInfo& ei, Score& mobility, Bitboard no_mob_area) {
515 Score bonus = SCORE_ZERO;
517 const Color Them = (Us == WHITE ? BLACK : WHITE);
518 const Square* ptr = pos.piece_list_begin(Us, Piece);
520 ei.attackedBy[Us][Piece] = 0;
522 while ((s = *ptr++) != SQ_NONE)
524 // Find attacked squares, including x-ray attacks for bishops and rooks
525 if (Piece == KNIGHT || Piece == QUEEN)
526 b = pos.attacks_from<Piece>(s);
527 else if (Piece == BISHOP)
528 b = bishop_attacks_bb(s, pos.occupied_squares() & ~pos.pieces(QUEEN, Us));
529 else if (Piece == ROOK)
530 b = rook_attacks_bb(s, pos.occupied_squares() & ~pos.pieces(ROOK, QUEEN, Us));
534 // Update attack info
535 ei.attackedBy[Us][Piece] |= b;
538 if (b & ei.kingZone[Us])
540 ei.kingAttackersCount[Us]++;
541 ei.kingAttackersWeight[Us] += KingAttackWeights[Piece];
542 Bitboard bb = (b & ei.attackedBy[Them][KING]);
544 ei.kingAdjacentZoneAttacksCount[Us] += count_1s_max_15<HasPopCnt>(bb);
548 mob = (Piece != QUEEN ? count_1s_max_15<HasPopCnt>(b & no_mob_area)
549 : count_1s<HasPopCnt>(b & no_mob_area));
551 mobility += MobilityBonus[Piece][mob];
553 // Decrease score if we are attacked by an enemy pawn. Remaining part
554 // of threat evaluation must be done later when we have full attack info.
555 if (bit_is_set(ei.attackedBy[Them][PAWN], s))
556 bonus -= ThreatedByPawnPenalty[Piece];
558 // Bishop and knight outposts squares
559 if ((Piece == BISHOP || Piece == KNIGHT) && pos.square_is_weak(s, Us))
560 bonus += evaluate_outposts<Piece, Us>(pos, ei, s);
562 // Queen or rook on 7th rank
563 if ( (Piece == ROOK || Piece == QUEEN)
564 && relative_rank(Us, s) == RANK_7
565 && relative_rank(Us, pos.king_square(Them)) == RANK_8)
567 bonus += (Piece == ROOK ? RookOn7thBonus : QueenOn7thBonus);
570 // Special extra evaluation for rooks
573 // Open and half-open files
575 if (ei.pi->file_is_half_open(Us, f))
577 if (ei.pi->file_is_half_open(Them, f))
578 bonus += RookOpenFileBonus;
580 bonus += RookHalfOpenFileBonus;
583 // Penalize rooks which are trapped inside a king. Penalize more if
584 // king has lost right to castle.
585 if (mob > 6 || ei.pi->file_is_half_open(Us, f))
588 ksq = pos.king_square(Us);
590 if ( square_file(ksq) >= FILE_E
591 && square_file(s) > square_file(ksq)
592 && (relative_rank(Us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
594 // Is there a half-open file between the king and the edge of the board?
595 if (!ei.pi->has_open_file_to_right(Us, square_file(ksq)))
596 bonus -= make_score(pos.can_castle(Us) ? (TrappedRookPenalty - mob * 16) / 2
597 : (TrappedRookPenalty - mob * 16), 0);
599 else if ( square_file(ksq) <= FILE_D
600 && square_file(s) < square_file(ksq)
601 && (relative_rank(Us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
603 // Is there a half-open file between the king and the edge of the board?
604 if (!ei.pi->has_open_file_to_left(Us, square_file(ksq)))
605 bonus -= make_score(pos.can_castle(Us) ? (TrappedRookPenalty - mob * 16) / 2
606 : (TrappedRookPenalty - mob * 16), 0);
614 // evaluate_threats<>() assigns bonuses according to the type of attacking piece
615 // and the type of attacked one.
618 Score evaluate_threats(const Position& pos, EvalInfo& ei) {
620 const Color Them = (Us == WHITE ? BLACK : WHITE);
623 Score bonus = SCORE_ZERO;
625 // Enemy pieces not defended by a pawn and under our attack
626 Bitboard weakEnemies = pos.pieces_of_color(Them)
627 & ~ei.attackedBy[Them][PAWN]
628 & ei.attackedBy[Us][0];
632 // Add bonus according to type of attacked enemy pieces and to the
633 // type of attacking piece, from knights to queens. Kings are not
634 // considered because are already special handled in king evaluation.
635 for (PieceType pt1 = KNIGHT; pt1 < KING; pt1++)
637 b = ei.attackedBy[Us][pt1] & weakEnemies;
639 for (PieceType pt2 = PAWN; pt2 < KING; pt2++)
640 if (b & pos.pieces(pt2))
641 bonus += ThreatBonus[pt1][pt2];
647 // evaluate_pieces_of_color<>() assigns bonuses and penalties to all the
648 // pieces of a given color.
650 template<Color Us, bool HasPopCnt>
651 Score evaluate_pieces_of_color(const Position& pos, EvalInfo& ei, Score& mobility) {
653 const Color Them = (Us == WHITE ? BLACK : WHITE);
655 Score bonus = SCORE_ZERO;
657 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 bonus += evaluate_pieces<KNIGHT, Us, HasPopCnt>(pos, ei, mobility, no_mob_area);
663 bonus += evaluate_pieces<BISHOP, Us, HasPopCnt>(pos, ei, mobility, no_mob_area);
664 bonus += evaluate_pieces<ROOK, Us, HasPopCnt>(pos, ei, mobility, no_mob_area);
665 bonus += evaluate_pieces<QUEEN, Us, HasPopCnt>(pos, ei, mobility, 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 Score 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 Score bonus = 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 margins[]
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 bonus -= KingDangerTable[Us][attackUnits];
764 margins[Us] += mg_value(KingDangerTable[Us][attackUnits]);
770 // evaluate_passed_pawns<>() evaluates the passed pawns of the given color
773 Score evaluate_passed_pawns(const Position& pos, EvalInfo& ei) {
775 const Color Them = (Us == WHITE ? BLACK : WHITE);
777 Score bonus = SCORE_ZERO;
778 Bitboard squaresToQueen, defendedSquares, unsafeSquares, supportingPawns;
779 Bitboard b = ei.pi->passed_pawns(Us);
785 Square s = pop_1st_bit(&b);
787 assert(pos.pawn_is_passed(Us, s));
789 int r = int(relative_rank(Us, s) - RANK_2);
790 int tr = r * (r - 1);
792 // Base bonus based on rank
793 Value mbonus = Value(20 * tr);
794 Value ebonus = Value(10 + r * r * 10);
798 Square blockSq = s + pawn_push(Us);
800 // Adjust bonus based on kings proximity
801 ebonus -= Value(square_distance(pos.king_square(Us), blockSq) * 3 * tr);
802 ebonus -= Value(square_distance(pos.king_square(Us), blockSq + pawn_push(Us)) * 1 * tr);
803 ebonus += Value(square_distance(pos.king_square(Them), blockSq) * 6 * tr);
805 // If the pawn is free to advance, increase bonus
806 if (pos.square_is_empty(blockSq))
808 squaresToQueen = squares_in_front_of(Us, s);
809 defendedSquares = squaresToQueen & ei.attackedBy[Us][0];
811 // If there is an enemy rook or queen attacking the pawn from behind,
812 // add all X-ray attacks by the rook or queen. Otherwise consider only
813 // the squares in the pawn's path attacked or occupied by the enemy.
814 if ( (squares_behind(Us, s) & pos.pieces(ROOK, QUEEN, Them))
815 && (squares_behind(Us, s) & pos.pieces(ROOK, QUEEN, Them) & pos.attacks_from<ROOK>(s)))
816 unsafeSquares = squaresToQueen;
818 unsafeSquares = squaresToQueen & (ei.attackedBy[Them][0] | pos.pieces_of_color(Them));
820 // If there aren't enemy attacks or pieces along the path to queen give
821 // huge bonus. Even bigger if we protect the pawn's path.
823 ebonus += Value(tr * (squaresToQueen == defendedSquares ? 17 : 15));
825 // OK, there are enemy attacks or pieces (but not pawns). Are those
826 // squares which are attacked by the enemy also attacked by us ?
827 // If yes, big bonus (but smaller than when there are no enemy attacks),
828 // if no, somewhat smaller bonus.
829 ebonus += Value(tr * ((unsafeSquares & defendedSquares) == unsafeSquares ? 13 : 8));
831 // At last, add a small bonus when there are no *friendly* pieces
832 // in the pawn's path.
833 if (!(squaresToQueen & pos.pieces_of_color(Us)))
838 // Increase the bonus if the passed pawn is supported by a friendly pawn
839 // on the same rank and a bit smaller if it's on the previous rank.
840 supportingPawns = pos.pieces(PAWN, Us) & neighboring_files_bb(s);
841 if (supportingPawns & rank_bb(s))
842 ebonus += Value(r * 20);
843 else if (supportingPawns & rank_bb(s - pawn_push(Us)))
844 ebonus += Value(r * 12);
846 // Rook pawns are a special case: They are sometimes worse, and
847 // sometimes better than other passed pawns. It is difficult to find
848 // good rules for determining whether they are good or bad. For now,
849 // we try the following: Increase the value for rook pawns if the
850 // other side has no pieces apart from a knight, and decrease the
851 // value if the other side has a rook or queen.
852 if (square_file(s) == FILE_A || square_file(s) == FILE_H)
854 if (pos.non_pawn_material(Them) <= KnightValueMidgame)
855 ebonus += ebonus / 4;
856 else if (pos.pieces(ROOK, QUEEN, Them))
857 ebonus -= ebonus / 4;
859 bonus += make_score(mbonus, ebonus);
863 // Add the scores to the middle game and endgame eval
864 return apply_weight(bonus, Weights[PassedPawns]);
868 // evaluate_space() computes the space evaluation for a given side. The
869 // space evaluation is a simple bonus based on the number of safe squares
870 // available for minor pieces on the central four files on ranks 2--4. Safe
871 // squares one, two or three squares behind a friendly pawn are counted
872 // twice. Finally, the space bonus is scaled by a weight taken from the
873 // material hash table.
874 template<Color Us, bool HasPopCnt>
875 int evaluate_space(const Position& pos, EvalInfo& ei) {
877 const Color Them = (Us == WHITE ? BLACK : WHITE);
879 // Find the safe squares for our pieces inside the area defined by
880 // SpaceMask[us]. A square is unsafe if it is attacked by an enemy
881 // pawn, or if it is undefended and attacked by an enemy piece.
882 Bitboard safe = SpaceMask[Us]
883 & ~pos.pieces(PAWN, Us)
884 & ~ei.attackedBy[Them][PAWN]
885 & (ei.attackedBy[Us][0] | ~ei.attackedBy[Them][0]);
887 // Find all squares which are at most three squares behind some friendly pawn
888 Bitboard behind = pos.pieces(PAWN, Us);
889 behind |= (Us == WHITE ? behind >> 8 : behind << 8);
890 behind |= (Us == WHITE ? behind >> 16 : behind << 16);
892 return count_1s_max_15<HasPopCnt>(safe) + count_1s_max_15<HasPopCnt>(behind & safe);
896 // apply_weight() applies an evaluation weight to a value trying to prevent overflow
898 inline Score apply_weight(Score v, Score w) {
899 return make_score((int(mg_value(v)) * mg_value(w)) / 0x100, (int(eg_value(v)) * eg_value(w)) / 0x100);
903 // scale_by_game_phase() interpolates between a middle game and an endgame score,
904 // based on game phase. It also scales the return value by a ScaleFactor array.
906 Value scale_by_game_phase(const Score& v, Phase ph, const ScaleFactor sf[]) {
908 assert(mg_value(v) > -VALUE_INFINITE && mg_value(v) < VALUE_INFINITE);
909 assert(eg_value(v) > -VALUE_INFINITE && eg_value(v) < VALUE_INFINITE);
910 assert(ph >= PHASE_ENDGAME && ph <= PHASE_MIDGAME);
912 Value eg = eg_value(v);
913 ScaleFactor f = sf[eg > VALUE_ZERO ? WHITE : BLACK];
914 Value ev = Value((eg * int(f)) / SCALE_FACTOR_NORMAL);
916 int result = (mg_value(v) * int(ph) + ev * int(128 - ph)) / 128;
917 return Value(result & ~(GrainSize - 1));
921 // weight_option() computes the value of an evaluation weight, by combining
922 // two UCI-configurable weights (midgame and endgame) with an internal weight.
924 Score weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight) {
926 // Scale option value from 100 to 256
927 int mg = get_option_value_int(mgOpt) * 256 / 100;
928 int eg = get_option_value_int(egOpt) * 256 / 100;
930 return apply_weight(make_score(mg, eg), internalWeight);
933 // init_safety() initizes the king safety evaluation, based on UCI
934 // parameters. It is called from read_weights().
938 const Value MaxSlope = Value(30);
939 const Value Peak = Value(1280);
942 // First setup the base table
943 for (int i = 0; i < 100; i++)
945 t[i] = Value(int(0.4 * i * i));
948 t[i] = Min(t[i], t[i - 1] + MaxSlope);
950 t[i] = Min(t[i], Peak);
953 // Then apply the weights and get the final KingDangerTable[] array
954 for (Color c = WHITE; c <= BLACK; c++)
955 for (int i = 0; i < 100; i++)
956 KingDangerTable[c][i] = apply_weight(make_score(t[i], 0), Weights[KingDangerUs + c]);