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 // Evaluation grain size, must be a power of 2
81 const int GrainSize = 8;
83 // Evaluation weights, initialized from UCI options
84 enum { Mobility, PawnStructure, PassedPawns, Space, KingDangerUs, KingDangerThem };
88 #define S(mg, eg) make_score(mg, eg)
90 // Internal evaluation weights. These are applied on top of the evaluation
91 // weights read from UCI parameters. The purpose is to be able to change
92 // the evaluation weights while keeping the default values of the UCI
93 // parameters at 100, which looks prettier.
95 // Values modified by Joona Kiiski
96 const Score WeightsInternal[] = {
97 S(248, 271), S(233, 201), S(252, 259), S(46, 0), S(247, 0), S(259, 0)
100 // MobilityBonus[PieceType][attacked] contains mobility bonuses for middle and
101 // end game, indexed by piece type and number of attacked squares not occupied
102 // by friendly pieces.
103 const Score MobilityBonus[][32] = {
105 { S(-38,-33), S(-25,-23), S(-12,-13), S( 0, -3), S(12, 7), S(25, 17), // Knights
106 S( 31, 22), S( 38, 27), S( 38, 27) },
107 { S(-25,-30), S(-11,-16), S( 3, -2), S(17, 12), S(31, 26), S(45, 40), // Bishops
108 S( 57, 52), S( 65, 60), S( 71, 65), S(74, 69), S(76, 71), S(78, 73),
109 S( 79, 74), S( 80, 75), S( 81, 76), S(81, 76) },
110 { S(-20,-36), S(-14,-19), S( -8, -3), S(-2, 13), S( 4, 29), S(10, 46), // Rooks
111 S( 14, 62), S( 19, 79), S( 23, 95), S(26,106), S(27,111), S(28,114),
112 S( 29,116), S( 30,117), S( 31,118), S(32,118) },
113 { S(-10,-18), S( -8,-13), S( -6, -7), S(-3, -2), S(-1, 3), S( 1, 8), // Queens
114 S( 3, 13), S( 5, 19), S( 8, 23), S(10, 27), S(12, 32), S(15, 34),
115 S( 16, 35), S( 17, 35), S( 18, 35), S(20, 35), S(20, 35), S(20, 35),
116 S( 20, 35), S( 20, 35), S( 20, 35), S(20, 35), S(20, 35), S(20, 35),
117 S( 20, 35), S( 20, 35), S( 20, 35), S(20, 35), S(20, 35), S(20, 35),
118 S( 20, 35), S( 20, 35) }
121 // OutpostBonus[PieceType][Square] contains outpost bonuses of knights and
122 // bishops, indexed by piece type and square (from white's point of view).
123 const Value OutpostBonus[][64] = {
126 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // Knights
127 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0),
128 V(0), V(0), V(4), V(8), V(8), V(4), V(0), V(0),
129 V(0), V(4),V(17),V(26),V(26),V(17), V(4), V(0),
130 V(0), V(8),V(26),V(35),V(35),V(26), V(8), V(0),
131 V(0), V(4),V(17),V(17),V(17),V(17), V(4), V(0),
132 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0),
133 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), // Bishops
136 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0),
137 V(0), V(0), V(5), V(5), V(5), V(5), V(0), V(0),
138 V(0), V(5),V(10),V(10),V(10),V(10), V(5), V(0),
139 V(0),V(10),V(21),V(21),V(21),V(21),V(10), V(0),
140 V(0), V(5), V(8), V(8), V(8), V(8), V(5), V(0),
141 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0),
142 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0) }
145 // ThreatBonus[attacking][attacked] contains threat bonuses according to
146 // which piece type attacks which one.
147 const Score ThreatBonus[][8] = {
149 { S(0, 0), S( 7, 39), S( 0, 0), S(24, 49), S(41,100), S(41,100) }, // KNIGHT
150 { S(0, 0), S( 7, 39), S(24, 49), S( 0, 0), S(41,100), S(41,100) }, // BISHOP
151 { S(0, 0), S(-1, 29), S(15, 49), S(15, 49), S( 0, 0), S(24, 49) }, // ROOK
152 { S(0, 0), S(15, 39), S(15, 39), S(15, 39), S(15, 39), S( 0, 0) } // QUEEN
155 // ThreatedByPawnPenalty[PieceType] contains a penalty according to which
156 // piece type is attacked by an enemy pawn.
157 const Score ThreatedByPawnPenalty[] = {
158 S(0, 0), S(0, 0), S(56, 70), S(56, 70), S(76, 99), S(86, 118)
163 // Rooks and queens on the 7th rank (modified by Joona Kiiski)
164 const Score RookOn7thBonus = make_score(47, 98);
165 const Score QueenOn7thBonus = make_score(27, 54);
167 // Rooks on open files (modified by Joona Kiiski)
168 const Score RookOpenFileBonus = make_score(43, 43);
169 const Score RookHalfOpenFileBonus = make_score(19, 19);
171 // Penalty for rooks trapped inside a friendly king which has lost the
173 const Value TrappedRookPenalty = Value(180);
175 // The SpaceMask[Color] contains the area of the board which is considered
176 // by the space evaluation. In the middle game, each side is given a bonus
177 // based on how many squares inside this area are safe and available for
178 // friendly minor pieces.
179 const Bitboard SpaceMask[] = {
180 (1ULL << SQ_C2) | (1ULL << SQ_D2) | (1ULL << SQ_E2) | (1ULL << SQ_F2) |
181 (1ULL << SQ_C3) | (1ULL << SQ_D3) | (1ULL << SQ_E3) | (1ULL << SQ_F3) |
182 (1ULL << SQ_C4) | (1ULL << SQ_D4) | (1ULL << SQ_E4) | (1ULL << SQ_F4),
183 (1ULL << SQ_C7) | (1ULL << SQ_D7) | (1ULL << SQ_E7) | (1ULL << SQ_F7) |
184 (1ULL << SQ_C6) | (1ULL << SQ_D6) | (1ULL << SQ_E6) | (1ULL << SQ_F6) |
185 (1ULL << SQ_C5) | (1ULL << SQ_D5) | (1ULL << SQ_E5) | (1ULL << SQ_F5)
188 // King danger constants and variables. The king danger scores are taken
189 // from the KingDangerTable[]. Various little "meta-bonuses" measuring
190 // the strength of the enemy attack are added up into an integer, which
191 // is used as an index to KingDangerTable[].
193 // KingAttackWeights[PieceType] contains king attack weights by piece type
194 const int KingAttackWeights[] = { 0, 0, 2, 2, 3, 5 };
196 // Bonuses for enemy's safe checks
197 const int QueenContactCheckBonus = 3;
198 const int QueenCheckBonus = 2;
199 const int RookCheckBonus = 1;
200 const int BishopCheckBonus = 1;
201 const int KnightCheckBonus = 1;
203 // InitKingDanger[Square] contains penalties based on the position of the
204 // defending king, indexed by king's square (from white's point of view).
205 const int InitKingDanger[] = {
206 2, 0, 2, 5, 5, 2, 0, 2,
207 2, 2, 4, 8, 8, 4, 2, 2,
208 7, 10, 12, 12, 12, 12, 10, 7,
209 15, 15, 15, 15, 15, 15, 15, 15,
210 15, 15, 15, 15, 15, 15, 15, 15,
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
216 // KingDangerTable[Color][attackUnits] contains the actual king danger
217 // weighted scores, indexed by color and by a calculated integer number.
218 Score KingDangerTable[2][128];
220 // Pawn and material hash tables, indexed by the current thread id.
221 // Note that they will be initialized at 0 being global variables.
222 MaterialInfoTable* MaterialTable[MAX_THREADS];
223 PawnInfoTable* PawnTable[MAX_THREADS];
225 // Function prototypes
226 template<bool HasPopCnt>
227 Value do_evaluate(const Position& pos, Value margins[]);
229 template<Color Us, bool HasPopCnt>
230 void init_eval_info(const Position& pos, EvalInfo& ei);
232 template<Color Us, bool HasPopCnt>
233 Score evaluate_pieces_of_color(const Position& pos, EvalInfo& ei, Score& mobility);
235 template<Color Us, bool HasPopCnt>
236 Score evaluate_king(const Position& pos, EvalInfo& ei, Value margins[]);
239 Score evaluate_threats(const Position& pos, EvalInfo& ei);
241 template<Color Us, bool HasPopCnt>
242 int evaluate_space(const Position& pos, EvalInfo& ei);
245 Score evaluate_passed_pawns(const Position& pos, EvalInfo& ei);
247 Score apply_weight(Score v, Score weight);
248 Value scale_by_game_phase(const Score& v, Phase ph, const ScaleFactor sf[]);
249 Score weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight);
259 /// Prefetches in pawn hash tables
261 void prefetchPawn(Key key, int threadID) {
263 PawnTable[threadID]->prefetch(key);
267 /// evaluate() is the main evaluation function. It always computes two
268 /// values, an endgame score and a middle game score, and interpolates
269 /// between them based on the remaining material.
270 Value evaluate(const Position& pos, Value margins[]) {
272 return CpuHasPOPCNT ? do_evaluate<true>(pos, margins)
273 : do_evaluate<false>(pos, margins);
278 template<bool HasPopCnt>
279 Value do_evaluate(const Position& pos, Value margins[]) {
282 ScaleFactor factor[2];
283 Score mobilityWhite, mobilityBlack;
286 assert(pos.thread() >= 0 && pos.thread() < MAX_THREADS);
287 assert(!pos.is_check());
289 // Initialize value by reading the incrementally updated scores included
290 // in the position object (material + piece square tables).
291 Score bonus = pos.value();
293 // margins[color] is the uncertainty estimation of position's evaluation
294 // and typically is used by the search for pruning decisions.
295 margins[WHITE] = margins[BLACK] = VALUE_ZERO;
297 // Probe the material hash table
298 MaterialInfo* mi = MaterialTable[pos.thread()]->get_material_info(pos);
299 bonus += mi->material_value();
301 // If we have a specialized evaluation function for the current material
302 // configuration, call it and return.
303 if (mi->specialized_eval_exists())
304 return mi->evaluate(pos);
306 // After get_material_info() call that modifies them
307 factor[WHITE] = mi->scale_factor(pos, WHITE);
308 factor[BLACK] = mi->scale_factor(pos, BLACK);
310 // Probe the pawn hash table
311 ei.pi = PawnTable[pos.thread()]->get_pawn_info(pos);
312 bonus += apply_weight(ei.pi->pawns_value(), Weights[PawnStructure]);
314 // Initialize attack and king safety bitboards
315 init_eval_info<WHITE, HasPopCnt>(pos, ei);
316 init_eval_info<BLACK, HasPopCnt>(pos, ei);
318 // Evaluate pieces and mobility
319 bonus += evaluate_pieces_of_color<WHITE, HasPopCnt>(pos, ei, mobilityWhite)
320 - evaluate_pieces_of_color<BLACK, HasPopCnt>(pos, ei, mobilityBlack);
322 bonus += apply_weight(mobilityWhite - mobilityBlack, Weights[Mobility]);
324 // Evaluate kings after all other pieces because we need complete attack
325 // information when computing the king safety evaluation.
326 bonus += evaluate_king<WHITE, HasPopCnt>(pos, ei, margins)
327 - evaluate_king<BLACK, HasPopCnt>(pos, ei, margins);
329 // Evaluate tactical threats, we need full attack information including king
330 bonus += evaluate_threats<WHITE>(pos, ei)
331 - evaluate_threats<BLACK>(pos, ei);
333 // Evaluate passed pawns, we need full attack information including king
334 bonus += evaluate_passed_pawns<WHITE>(pos, ei)
335 - evaluate_passed_pawns<BLACK>(pos, ei);
337 Phase phase = mi->game_phase();
339 // Middle-game specific evaluation terms
340 if (phase > PHASE_ENDGAME)
342 // Evaluate pawn storms in positions with opposite castling
343 if ( square_file(pos.king_square(WHITE)) >= FILE_E
344 && square_file(pos.king_square(BLACK)) <= FILE_D)
346 bonus += make_score(ei.pi->queenside_storm_value(WHITE) - ei.pi->kingside_storm_value(BLACK), 0);
348 else if ( square_file(pos.king_square(WHITE)) <= FILE_D
349 && square_file(pos.king_square(BLACK)) >= FILE_E)
351 bonus += make_score(ei.pi->kingside_storm_value(WHITE) - ei.pi->queenside_storm_value(BLACK), 0);
353 // Evaluate space for both sides
354 if (mi->space_weight() > 0)
356 int s = evaluate_space<WHITE, HasPopCnt>(pos, ei) - evaluate_space<BLACK, HasPopCnt>(pos, ei);
357 bonus += apply_weight(make_score(s * mi->space_weight(), 0), Weights[Space]);
361 // If we don't already have an unusual scale factor, check for opposite
362 // colored bishop endgames, and use a lower scale for those
363 if ( phase < PHASE_MIDGAME
364 && pos.opposite_colored_bishops()
365 && ( (factor[WHITE] == SCALE_FACTOR_NORMAL && eg_value(bonus) > VALUE_ZERO)
366 || (factor[BLACK] == SCALE_FACTOR_NORMAL && eg_value(bonus) < VALUE_ZERO)))
370 // Only the two bishops ?
371 if ( pos.non_pawn_material(WHITE) == BishopValueMidgame
372 && pos.non_pawn_material(BLACK) == BishopValueMidgame)
374 // Check for KBP vs KB with only a single pawn that is almost
375 // certainly a draw or at least two pawns.
376 bool one_pawn = (pos.piece_count(WHITE, PAWN) + pos.piece_count(BLACK, PAWN) == 1);
377 sf = one_pawn ? ScaleFactor(8) : ScaleFactor(32);
380 // Endgame with opposite-colored bishops, but also other pieces. Still
381 // a bit drawish, but not as drawish as with only the two bishops.
382 sf = ScaleFactor(50);
384 if (factor[WHITE] == SCALE_FACTOR_NORMAL)
386 if (factor[BLACK] == SCALE_FACTOR_NORMAL)
390 // Interpolate between the middle game and the endgame score
391 Value v = scale_by_game_phase(bonus, phase, factor);
392 return pos.side_to_move() == WHITE ? v : -v;
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();
417 if (!MaterialTable[i])
418 MaterialTable[i] = new MaterialInfoTable();
423 /// quit_eval() releases heap-allocated memory at program termination
431 /// read_weights() reads evaluation weights from the corresponding UCI parameters
433 void read_weights(Color us) {
435 // King safety is asymmetrical. Our king danger level is weighted by
436 // "Cowardice" UCI parameter, instead the opponent one by "Aggressiveness".
437 const int kingDangerUs = (us == WHITE ? KingDangerUs : KingDangerThem);
438 const int kingDangerThem = (us == WHITE ? KingDangerThem : KingDangerUs);
440 Weights[Mobility] = weight_option("Mobility (Middle Game)", "Mobility (Endgame)", WeightsInternal[Mobility]);
441 Weights[PawnStructure] = weight_option("Pawn Structure (Middle Game)", "Pawn Structure (Endgame)", WeightsInternal[PawnStructure]);
442 Weights[PassedPawns] = weight_option("Passed Pawns (Middle Game)", "Passed Pawns (Endgame)", WeightsInternal[PassedPawns]);
443 Weights[Space] = weight_option("Space", "Space", WeightsInternal[Space]);
444 Weights[kingDangerUs] = weight_option("Cowardice", "Cowardice", WeightsInternal[KingDangerUs]);
445 Weights[kingDangerThem] = weight_option("Aggressiveness", "Aggressiveness", WeightsInternal[KingDangerThem]);
447 // If running in analysis mode, make sure we use symmetrical king safety. We do this
448 // by replacing both Weights[kingDangerUs] and Weights[kingDangerThem] by their average.
449 if (get_option_value_bool("UCI_AnalyseMode"))
450 Weights[kingDangerUs] = Weights[kingDangerThem] = (Weights[kingDangerUs] + Weights[kingDangerThem]) / 2;
458 // init_eval_info() initializes king bitboards for given color adding
459 // pawn attacks. To be done at the beginning of the evaluation.
461 template<Color Us, bool HasPopCnt>
462 void init_eval_info(const Position& pos, EvalInfo& ei) {
464 const Color Them = (Us == WHITE ? BLACK : WHITE);
466 Bitboard b = ei.attackedBy[Them][KING] = pos.attacks_from<KING>(pos.king_square(Them));
467 ei.kingZone[Us] = (b | (Us == WHITE ? b >> 8 : b << 8));
468 ei.attackedBy[Us][PAWN] = ei.pi->pawn_attacks(Us);
469 b &= ei.attackedBy[Us][PAWN];
470 ei.kingAttackersCount[Us] = b ? count_1s_max_15<HasPopCnt>(b) / 2 : EmptyBoardBB;
471 ei.kingAdjacentZoneAttacksCount[Us] = ei.kingAttackersWeight[Us] = EmptyBoardBB;
475 // evaluate_outposts() evaluates bishop and knight outposts squares
477 template<PieceType Piece, Color Us>
478 Score evaluate_outposts(const Position& pos, EvalInfo& ei, Square s) {
480 const Color Them = (Us == WHITE ? BLACK : WHITE);
482 assert (Piece == BISHOP || Piece == KNIGHT);
484 // Initial bonus based on square
485 Value bonus = OutpostBonus[Piece == BISHOP][relative_square(Us, s)];
487 // Increase bonus if supported by pawn, especially if the opponent has
488 // no minor piece which can exchange the outpost piece.
489 if (bonus && bit_is_set(ei.attackedBy[Us][PAWN], s))
491 if ( pos.pieces(KNIGHT, Them) == EmptyBoardBB
492 && (SquaresByColorBB[square_color(s)] & pos.pieces(BISHOP, Them)) == EmptyBoardBB)
493 bonus += bonus + bonus / 2;
497 return make_score(bonus, bonus);
501 // evaluate_pieces<>() assigns bonuses and penalties to the pieces of a given color
503 template<PieceType Piece, Color Us, bool HasPopCnt>
504 Score evaluate_pieces(const Position& pos, EvalInfo& ei, Score& mobility, Bitboard no_mob_area) {
510 Score bonus = SCORE_ZERO;
512 const Color Them = (Us == WHITE ? BLACK : WHITE);
513 const Square* ptr = pos.piece_list_begin(Us, Piece);
515 ei.attackedBy[Us][Piece] = EmptyBoardBB;
517 while ((s = *ptr++) != SQ_NONE)
519 // Find attacked squares, including x-ray attacks for bishops and rooks
520 if (Piece == KNIGHT || Piece == QUEEN)
521 b = pos.attacks_from<Piece>(s);
522 else if (Piece == BISHOP)
523 b = bishop_attacks_bb(s, pos.occupied_squares() & ~pos.pieces(QUEEN, Us));
524 else if (Piece == ROOK)
525 b = rook_attacks_bb(s, pos.occupied_squares() & ~pos.pieces(ROOK, QUEEN, Us));
529 // Update attack info
530 ei.attackedBy[Us][Piece] |= b;
533 if (b & ei.kingZone[Us])
535 ei.kingAttackersCount[Us]++;
536 ei.kingAttackersWeight[Us] += KingAttackWeights[Piece];
537 Bitboard bb = (b & ei.attackedBy[Them][KING]);
539 ei.kingAdjacentZoneAttacksCount[Us] += count_1s_max_15<HasPopCnt>(bb);
543 mob = (Piece != QUEEN ? count_1s_max_15<HasPopCnt>(b & no_mob_area)
544 : count_1s<HasPopCnt>(b & no_mob_area));
546 mobility += MobilityBonus[Piece][mob];
548 // Decrease score if we are attacked by an enemy pawn. Remaining part
549 // of threat evaluation must be done later when we have full attack info.
550 if (bit_is_set(ei.attackedBy[Them][PAWN], s))
551 bonus -= ThreatedByPawnPenalty[Piece];
553 // Bishop and knight outposts squares
554 if ((Piece == BISHOP || Piece == KNIGHT) && pos.square_is_weak(s, Us))
555 bonus += evaluate_outposts<Piece, Us>(pos, ei, s);
557 // Queen or rook on 7th rank
558 if ( (Piece == ROOK || Piece == QUEEN)
559 && relative_rank(Us, s) == RANK_7
560 && relative_rank(Us, pos.king_square(Them)) == RANK_8)
562 bonus += (Piece == ROOK ? RookOn7thBonus : QueenOn7thBonus);
565 // Special extra evaluation for rooks
568 // Open and half-open files
570 if (ei.pi->file_is_half_open(Us, f))
572 if (ei.pi->file_is_half_open(Them, f))
573 bonus += RookOpenFileBonus;
575 bonus += RookHalfOpenFileBonus;
578 // Penalize rooks which are trapped inside a king. Penalize more if
579 // king has lost right to castle.
580 if (mob > 6 || ei.pi->file_is_half_open(Us, f))
583 ksq = pos.king_square(Us);
585 if ( square_file(ksq) >= FILE_E
586 && square_file(s) > square_file(ksq)
587 && (relative_rank(Us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
589 // Is there a half-open file between the king and the edge of the board?
590 if (!ei.pi->has_open_file_to_right(Us, square_file(ksq)))
591 bonus -= make_score(pos.can_castle(Us) ? (TrappedRookPenalty - mob * 16) / 2
592 : (TrappedRookPenalty - mob * 16), 0);
594 else if ( square_file(ksq) <= FILE_D
595 && square_file(s) < square_file(ksq)
596 && (relative_rank(Us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
598 // Is there a half-open file between the king and the edge of the board?
599 if (!ei.pi->has_open_file_to_left(Us, square_file(ksq)))
600 bonus -= make_score(pos.can_castle(Us) ? (TrappedRookPenalty - mob * 16) / 2
601 : (TrappedRookPenalty - mob * 16), 0);
609 // evaluate_threats<>() assigns bonuses according to the type of attacking piece
610 // and the type of attacked one.
613 Score evaluate_threats(const Position& pos, EvalInfo& ei) {
615 const Color Them = (Us == WHITE ? BLACK : WHITE);
618 Score bonus = SCORE_ZERO;
620 // Enemy pieces not defended by a pawn and under our attack
621 Bitboard weakEnemies = pos.pieces_of_color(Them)
622 & ~ei.attackedBy[Them][PAWN]
623 & ei.attackedBy[Us][0];
627 // Add bonus according to type of attacked enemy piece and to the
628 // type of attacking piece, from knights to queens. Kings are not
629 // considered because are already handled in king evaluation.
630 for (PieceType pt1 = KNIGHT; pt1 < KING; pt1++)
632 b = ei.attackedBy[Us][pt1] & weakEnemies;
634 for (PieceType pt2 = PAWN; pt2 < KING; pt2++)
635 if (b & pos.pieces(pt2))
636 bonus += ThreatBonus[pt1][pt2];
642 // evaluate_pieces_of_color<>() assigns bonuses and penalties to all the
643 // pieces of a given color.
645 template<Color Us, bool HasPopCnt>
646 Score evaluate_pieces_of_color(const Position& pos, EvalInfo& ei, Score& mobility) {
648 const Color Them = (Us == WHITE ? BLACK : WHITE);
650 Score bonus = mobility = SCORE_ZERO;
652 // Do not include in mobility squares protected by enemy pawns or occupied by our pieces
653 const Bitboard no_mob_area = ~(ei.attackedBy[Them][PAWN] | pos.pieces_of_color(Us));
655 bonus += evaluate_pieces<KNIGHT, Us, HasPopCnt>(pos, ei, mobility, no_mob_area);
656 bonus += evaluate_pieces<BISHOP, Us, HasPopCnt>(pos, ei, mobility, no_mob_area);
657 bonus += evaluate_pieces<ROOK, Us, HasPopCnt>(pos, ei, mobility, no_mob_area);
658 bonus += evaluate_pieces<QUEEN, Us, HasPopCnt>(pos, ei, mobility, no_mob_area);
660 // Sum up all attacked squares
661 ei.attackedBy[Us][0] = ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
662 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
663 | ei.attackedBy[Us][QUEEN] | ei.attackedBy[Us][KING];
668 // evaluate_king<>() assigns bonuses and penalties to a king of a given color
670 template<Color Us, bool HasPopCnt>
671 Score evaluate_king(const Position& pos, EvalInfo& ei, Value margins[]) {
673 const Color Them = (Us == WHITE ? BLACK : WHITE);
675 Bitboard undefended, b, b1, b2, safe;
677 const Square ksq = pos.king_square(Us);
680 Score bonus = ei.pi->king_shelter<Us>(pos, ksq);
682 // King safety. This is quite complicated, and is almost certainly far
683 // from optimally tuned.
684 if ( ei.kingAttackersCount[Them] >= 2
685 && pos.non_pawn_material(Them) >= QueenValueMidgame + RookValueMidgame
686 && pos.piece_count(Them, QUEEN) >= 1
687 && ei.kingAdjacentZoneAttacksCount[Them])
689 // Find the attacked squares around the king which has no defenders
690 // apart from the king itself
691 undefended = ei.attackedBy[Them][0] & ei.attackedBy[Us][KING];
692 undefended &= ~( ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
693 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
694 | ei.attackedBy[Us][QUEEN]);
696 // Initialize the 'attackUnits' variable, which is used later on as an
697 // index to the KingDangerTable[] array. The initial value is based on
698 // the number and types of the enemy's attacking pieces, the number of
699 // attacked and undefended squares around our king, the square of the
700 // king, and the quality of the pawn shelter.
701 attackUnits = Min(25, (ei.kingAttackersCount[Them] * ei.kingAttackersWeight[Them]) / 2)
702 + 3 * (ei.kingAdjacentZoneAttacksCount[Them] + count_1s_max_15<HasPopCnt>(undefended))
703 + InitKingDanger[relative_square(Us, ksq)]
704 - mg_value(ei.pi->king_shelter<Us>(pos, ksq)) / 32;
706 // Analyse enemy's safe queen contact checks. First find undefended
707 // squares around the king attacked by enemy queen...
708 b = undefended & ei.attackedBy[Them][QUEEN] & ~pos.pieces_of_color(Them);
711 // ...then remove squares not supported by another enemy piece
712 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
713 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][ROOK]);
715 attackUnits += QueenContactCheckBonus
716 * count_1s_max_15<HasPopCnt>(b)
717 * (Them == pos.side_to_move() ? 2 : 1);
720 // Analyse enemy's safe distance checks for sliders and knights
721 safe = ~(pos.pieces_of_color(Them) | ei.attackedBy[Us][0]);
723 b1 = pos.attacks_from<ROOK>(ksq) & safe;
724 b2 = pos.attacks_from<BISHOP>(ksq) & safe;
726 // Enemy queen safe checks
727 b = (b1 | b2) & ei.attackedBy[Them][QUEEN];
729 attackUnits += QueenCheckBonus * count_1s_max_15<HasPopCnt>(b);
731 // Enemy rooks safe checks
732 b = b1 & ei.attackedBy[Them][ROOK];
734 attackUnits += RookCheckBonus * count_1s_max_15<HasPopCnt>(b);
736 // Enemy bishops safe checks
737 b = b2 & ei.attackedBy[Them][BISHOP];
739 attackUnits += BishopCheckBonus * count_1s_max_15<HasPopCnt>(b);
741 // Enemy knights safe checks
742 b = pos.attacks_from<KNIGHT>(ksq) & ei.attackedBy[Them][KNIGHT] & safe;
744 attackUnits += KnightCheckBonus * count_1s_max_15<HasPopCnt>(b);
746 // To index KingDangerTable[] attackUnits must be in [0, 99] range
747 attackUnits = Min(99, Max(0, attackUnits));
749 // Finally, extract the king danger score from the KingDangerTable[]
750 // array and subtract the score from evaluation. Set also margins[]
751 // value that will be used for pruning because this value can sometimes
752 // be very big, and so capturing a single attacking piece can therefore
753 // result in a score change far bigger than the value of the captured piece.
754 bonus -= KingDangerTable[Us][attackUnits];
755 margins[Us] += mg_value(KingDangerTable[Us][attackUnits]);
761 // evaluate_passed_pawns<>() evaluates the passed pawns of the given color
764 Score evaluate_passed_pawns(const Position& pos, EvalInfo& ei) {
766 const Color Them = (Us == WHITE ? BLACK : WHITE);
768 Score bonus = SCORE_ZERO;
769 Bitboard squaresToQueen, defendedSquares, unsafeSquares, supportingPawns;
770 Bitboard b = ei.pi->passed_pawns(Us);
776 Square s = pop_1st_bit(&b);
778 assert(pos.pawn_is_passed(Us, s));
780 int r = int(relative_rank(Us, s) - RANK_2);
781 int rr = r * (r - 1);
783 // Base bonus based on rank
784 Value mbonus = Value(20 * rr);
785 Value ebonus = Value(10 * (rr + r + 1));
789 Square blockSq = s + pawn_push(Us);
791 // Adjust bonus based on kings proximity
792 ebonus -= Value(square_distance(pos.king_square(Us), blockSq) * 3 * rr);
793 ebonus -= Value(square_distance(pos.king_square(Us), blockSq + pawn_push(Us)) * rr);
794 ebonus += Value(square_distance(pos.king_square(Them), blockSq) * 6 * rr);
796 // If the pawn is free to advance, increase bonus
797 if (pos.square_is_empty(blockSq))
799 squaresToQueen = squares_in_front_of(Us, s);
800 defendedSquares = squaresToQueen & ei.attackedBy[Us][0];
802 // If there is an enemy rook or queen attacking the pawn from behind,
803 // add all X-ray attacks by the rook or queen. Otherwise consider only
804 // the squares in the pawn's path attacked or occupied by the enemy.
805 if ( (squares_behind(Us, s) & pos.pieces(ROOK, QUEEN, Them))
806 && (squares_behind(Us, s) & pos.pieces(ROOK, QUEEN, Them) & pos.attacks_from<ROOK>(s)))
807 unsafeSquares = squaresToQueen;
809 unsafeSquares = squaresToQueen & (ei.attackedBy[Them][0] | pos.pieces_of_color(Them));
811 // If there aren't enemy attacks or pieces along the path to queen give
812 // huge bonus. Even bigger if we protect the pawn's path.
814 ebonus += Value(rr * (squaresToQueen == defendedSquares ? 17 : 15));
816 // OK, there are enemy attacks or pieces (but not pawns). Are those
817 // squares which are attacked by the enemy also attacked by us ?
818 // If yes, big bonus (but smaller than when there are no enemy attacks),
819 // if no, somewhat smaller bonus.
820 ebonus += Value(rr * ((unsafeSquares & defendedSquares) == unsafeSquares ? 13 : 8));
822 // At last, add a small bonus when there are no *friendly* pieces
823 // in the pawn's path.
824 if (!(squaresToQueen & pos.pieces_of_color(Us)))
829 // Increase the bonus if the passed pawn is supported by a friendly pawn
830 // on the same rank and a bit smaller if it's on the previous rank.
831 supportingPawns = pos.pieces(PAWN, Us) & neighboring_files_bb(s);
832 if (supportingPawns & rank_bb(s))
833 ebonus += Value(r * 20);
834 else if (supportingPawns & rank_bb(s - pawn_push(Us)))
835 ebonus += Value(r * 12);
837 // Rook pawns are a special case: They are sometimes worse, and
838 // sometimes better than other passed pawns. It is difficult to find
839 // good rules for determining whether they are good or bad. For now,
840 // we try the following: Increase the value for rook pawns if the
841 // other side has no pieces apart from a knight, and decrease the
842 // value if the other side has a rook or queen.
843 if (square_file(s) == FILE_A || square_file(s) == FILE_H)
845 if (pos.non_pawn_material(Them) <= KnightValueMidgame)
846 ebonus += ebonus / 4;
847 else if (pos.pieces(ROOK, QUEEN, Them))
848 ebonus -= ebonus / 4;
850 bonus += make_score(mbonus, ebonus);
854 // Add the scores to the middle game and endgame eval
855 return apply_weight(bonus, Weights[PassedPawns]);
859 // evaluate_space() computes the space evaluation for a given side. The
860 // space evaluation is a simple bonus based on the number of safe squares
861 // available for minor pieces on the central four files on ranks 2--4. Safe
862 // squares one, two or three squares behind a friendly pawn are counted
863 // twice. Finally, the space bonus is scaled by a weight taken from the
864 // material hash table. The aim is to improve play on game opening.
865 template<Color Us, bool HasPopCnt>
866 int evaluate_space(const Position& pos, EvalInfo& ei) {
868 const Color Them = (Us == WHITE ? BLACK : WHITE);
870 // Find the safe squares for our pieces inside the area defined by
871 // SpaceMask[]. A square is unsafe if it is attacked by an enemy
872 // pawn, or if it is undefended and attacked by an enemy piece.
873 Bitboard safe = SpaceMask[Us]
874 & ~pos.pieces(PAWN, Us)
875 & ~ei.attackedBy[Them][PAWN]
876 & (ei.attackedBy[Us][0] | ~ei.attackedBy[Them][0]);
878 // Find all squares which are at most three squares behind some friendly pawn
879 Bitboard behind = pos.pieces(PAWN, Us);
880 behind |= (Us == WHITE ? behind >> 8 : behind << 8);
881 behind |= (Us == WHITE ? behind >> 16 : behind << 16);
883 return count_1s_max_15<HasPopCnt>(safe) + count_1s_max_15<HasPopCnt>(behind & safe);
887 // apply_weight() applies an evaluation weight to a value trying to prevent overflow
889 inline Score apply_weight(Score v, Score w) {
890 return make_score((int(mg_value(v)) * mg_value(w)) / 0x100,
891 (int(eg_value(v)) * eg_value(w)) / 0x100);
895 // scale_by_game_phase() interpolates between a middle game and an endgame score,
896 // based on game phase. It also scales the return value by a ScaleFactor array.
898 Value scale_by_game_phase(const Score& v, Phase ph, const ScaleFactor sf[]) {
900 assert(mg_value(v) > -VALUE_INFINITE && mg_value(v) < VALUE_INFINITE);
901 assert(eg_value(v) > -VALUE_INFINITE && eg_value(v) < VALUE_INFINITE);
902 assert(ph >= PHASE_ENDGAME && ph <= PHASE_MIDGAME);
904 Value eg = eg_value(v);
905 ScaleFactor f = sf[eg > VALUE_ZERO ? WHITE : BLACK];
906 Value ev = Value((eg * int(f)) / SCALE_FACTOR_NORMAL);
908 int result = (mg_value(v) * int(ph) + ev * int(128 - ph)) / 128;
909 return Value(result & ~(GrainSize - 1));
913 // weight_option() computes the value of an evaluation weight, by combining
914 // two UCI-configurable weights (midgame and endgame) with an internal weight.
916 Score weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight) {
918 // Scale option value from 100 to 256
919 int mg = get_option_value_int(mgOpt) * 256 / 100;
920 int eg = get_option_value_int(egOpt) * 256 / 100;
922 return apply_weight(make_score(mg, eg), internalWeight);
926 // init_safety() initizes the king safety evaluation, based on UCI
927 // parameters. It is called from read_weights().
931 const Value MaxSlope = Value(30);
932 const Value Peak = Value(1280);
935 // First setup the base table
936 for (int i = 0; i < 100; i++)
938 t[i] = Value(int(0.4 * i * i));
941 t[i] = Min(t[i], t[i - 1] + MaxSlope);
943 t[i] = Min(t[i], Peak);
946 // Then apply the weights and get the final KingDangerTable[] array
947 for (Color c = WHITE; c <= BLACK; c++)
948 for (int i = 0; i < 100; i++)
949 KingDangerTable[c][i] = apply_weight(make_score(t[i], 0), Weights[KingDangerUs + c]);