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, Score& mobility);
240 template<Color Us, bool HasPopCnt>
241 Score evaluate_king(const Position& pos, EvalInfo& ei, Value margins[]);
244 Score evaluate_threats(const Position& pos, EvalInfo& ei);
246 template<Color Us, bool HasPopCnt>
247 int evaluate_space(const Position& pos, EvalInfo& ei);
250 Score 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 ei.value += evaluate_pieces_of_color<WHITE, HasPopCnt>(pos, ei, w_mob)
324 - evaluate_pieces_of_color<BLACK, HasPopCnt>(pos, ei, b_mob);
326 ei.value += apply_weight(w_mob - b_mob, Weights[Mobility]);
328 // Kings. Kings are evaluated after all other pieces for both sides,
329 // because we need complete attack information for all pieces when computing
330 // the king safety evaluation.
331 ei.value += evaluate_king<WHITE, HasPopCnt>(pos, ei, margins)
332 - evaluate_king<BLACK, HasPopCnt>(pos, ei, margins);
334 // Evaluate tactical threats, we need full attack info including king
335 ei.value += evaluate_threats<WHITE>(pos, ei)
336 - evaluate_threats<BLACK>(pos, ei);
338 // Evaluate passed pawns, we need full attack info including king
339 ei.value += evaluate_passed_pawns<WHITE>(pos, ei)
340 - evaluate_passed_pawns<BLACK>(pos, ei);
342 Phase phase = mi->game_phase();
344 // Middle-game specific evaluation terms
345 if (phase > PHASE_ENDGAME)
347 // Evaluate pawn storms in positions with opposite castling
348 if ( square_file(pos.king_square(WHITE)) >= FILE_E
349 && square_file(pos.king_square(BLACK)) <= FILE_D)
351 ei.value += make_score(ei.pi->queenside_storm_value(WHITE) - ei.pi->kingside_storm_value(BLACK), 0);
353 else if ( square_file(pos.king_square(WHITE)) <= FILE_D
354 && square_file(pos.king_square(BLACK)) >= FILE_E)
356 ei.value += make_score(ei.pi->kingside_storm_value(WHITE) - ei.pi->queenside_storm_value(BLACK), 0);
358 // Evaluate space for both sides
359 if (mi->space_weight() > 0)
361 int s = evaluate_space<WHITE, HasPopCnt>(pos, ei) - evaluate_space<BLACK, HasPopCnt>(pos, ei);
362 ei.value += apply_weight(make_score(s * mi->space_weight(), 0), Weights[Space]);
366 // If we don't already have an unusual scale factor, check for opposite
367 // colored bishop endgames, and use a lower scale for those
368 if ( phase < PHASE_MIDGAME
369 && pos.opposite_colored_bishops()
370 && ( (factor[WHITE] == SCALE_FACTOR_NORMAL && eg_value(ei.value) > VALUE_ZERO)
371 || (factor[BLACK] == SCALE_FACTOR_NORMAL && eg_value(ei.value) < VALUE_ZERO)))
375 // Only the two bishops ?
376 if ( pos.non_pawn_material(WHITE) == BishopValueMidgame
377 && pos.non_pawn_material(BLACK) == BishopValueMidgame)
379 // Check for KBP vs KB with only a single pawn that is almost
380 // certainly a draw or at least two pawns.
381 bool one_pawn = (pos.piece_count(WHITE, PAWN) + pos.piece_count(BLACK, PAWN) == 1);
382 sf = one_pawn ? ScaleFactor(8) : ScaleFactor(32);
385 // Endgame with opposite-colored bishops, but also other pieces. Still
386 // a bit drawish, but not as drawish as with only the two bishops.
387 sf = ScaleFactor(50);
389 if (factor[WHITE] == SCALE_FACTOR_NORMAL)
391 if (factor[BLACK] == SCALE_FACTOR_NORMAL)
395 // Interpolate between the middle game and the endgame score
396 return Sign[pos.side_to_move()] * scale_by_game_phase(ei.value, phase, factor);
401 /// init_eval() initializes various tables used by the evaluation function
403 void init_eval(int threads) {
405 assert(threads <= MAX_THREADS);
407 for (int i = 0; i < MAX_THREADS; i++)
412 delete MaterialTable[i];
414 MaterialTable[i] = NULL;
418 PawnTable[i] = new PawnInfoTable();
419 if (!MaterialTable[i])
420 MaterialTable[i] = new MaterialInfoTable();
425 /// quit_eval() releases heap-allocated memory at program termination
429 for (int i = 0; i < MAX_THREADS; i++)
432 delete MaterialTable[i];
434 MaterialTable[i] = NULL;
439 /// read_weights() reads evaluation weights from the corresponding UCI parameters
441 void read_weights(Color us) {
443 // King safety is asymmetrical. Our king danger level is weighted by
444 // "Cowardice" UCI parameter, instead the opponent one by "Aggressiveness".
445 const int kingDangerUs = (us == WHITE ? KingDangerUs : KingDangerThem);
446 const int kingDangerThem = (us == WHITE ? KingDangerThem : KingDangerUs);
448 Weights[Mobility] = weight_option("Mobility (Middle Game)", "Mobility (Endgame)", WeightsInternal[Mobility]);
449 Weights[PawnStructure] = weight_option("Pawn Structure (Middle Game)", "Pawn Structure (Endgame)", WeightsInternal[PawnStructure]);
450 Weights[PassedPawns] = weight_option("Passed Pawns (Middle Game)", "Passed Pawns (Endgame)", WeightsInternal[PassedPawns]);
451 Weights[Space] = weight_option("Space", "Space", WeightsInternal[Space]);
452 Weights[kingDangerUs] = weight_option("Cowardice", "Cowardice", WeightsInternal[KingDangerUs]);
453 Weights[kingDangerThem] = weight_option("Aggressiveness", "Aggressiveness", WeightsInternal[KingDangerThem]);
455 // If running in analysis mode, make sure we use symmetrical king safety. We do this
456 // by replacing both Weights[kingDangerUs] and Weights[kingDangerThem] by their average.
457 if (get_option_value_bool("UCI_AnalyseMode"))
458 Weights[kingDangerUs] = Weights[kingDangerThem] = (Weights[kingDangerUs] + Weights[kingDangerThem]) / 2;
466 // init_attack_tables() initializes king bitboards for both sides adding
467 // pawn attacks. To be done before other evaluations.
469 template<Color Us, bool HasPopCnt>
470 void init_attack_tables(const Position& pos, EvalInfo& ei) {
472 const Color Them = (Us == WHITE ? BLACK : WHITE);
474 Bitboard b = ei.attackedBy[Them][KING] = pos.attacks_from<KING>(pos.king_square(Them));
475 ei.kingZone[Us] = (b | (Us == WHITE ? b >> 8 : b << 8));
476 ei.attackedBy[Us][PAWN] = ei.pi->pawn_attacks(Us);
477 b &= ei.attackedBy[Us][PAWN];
478 ei.kingAttackersCount[Us] = b ? count_1s_max_15<HasPopCnt>(b) / 2 : 0;
479 ei.kingAdjacentZoneAttacksCount[Us] = ei.kingAttackersWeight[Us] = 0;
483 // evaluate_outposts() evaluates bishop and knight outposts squares
485 template<PieceType Piece, Color Us>
486 Score evaluate_outposts(const Position& pos, EvalInfo& ei, Square s) {
488 const Color Them = (Us == WHITE ? BLACK : WHITE);
490 assert (Piece == BISHOP || Piece == KNIGHT);
492 // Initial bonus based on square
493 Value bonus = OutpostBonus[Piece == BISHOP][relative_square(Us, s)];
495 // Increase bonus if supported by pawn, especially if the opponent has
496 // no minor piece which can exchange the outpost piece
497 if (bonus && bit_is_set(ei.attackedBy[Us][PAWN], s))
499 if ( pos.pieces(KNIGHT, Them) == EmptyBoardBB
500 && (SquaresByColorBB[square_color(s)] & pos.pieces(BISHOP, Them)) == EmptyBoardBB)
501 bonus += bonus + bonus / 2;
505 return make_score(bonus, bonus);
509 // evaluate_pieces<>() assigns bonuses and penalties to the pieces of a given color
511 template<PieceType Piece, Color Us, bool HasPopCnt>
512 Score evaluate_pieces(const Position& pos, EvalInfo& ei, Score& mobility, Bitboard no_mob_area) {
518 Score bonus = SCORE_ZERO;
520 const Color Them = (Us == WHITE ? BLACK : WHITE);
521 const Square* ptr = pos.piece_list_begin(Us, Piece);
523 ei.attackedBy[Us][Piece] = 0;
525 while ((s = *ptr++) != SQ_NONE)
527 // Find attacked squares, including x-ray attacks for bishops and rooks
528 if (Piece == KNIGHT || Piece == QUEEN)
529 b = pos.attacks_from<Piece>(s);
530 else if (Piece == BISHOP)
531 b = bishop_attacks_bb(s, pos.occupied_squares() & ~pos.pieces(QUEEN, Us));
532 else if (Piece == ROOK)
533 b = rook_attacks_bb(s, pos.occupied_squares() & ~pos.pieces(ROOK, QUEEN, Us));
537 // Update attack info
538 ei.attackedBy[Us][Piece] |= b;
541 if (b & ei.kingZone[Us])
543 ei.kingAttackersCount[Us]++;
544 ei.kingAttackersWeight[Us] += KingAttackWeights[Piece];
545 Bitboard bb = (b & ei.attackedBy[Them][KING]);
547 ei.kingAdjacentZoneAttacksCount[Us] += count_1s_max_15<HasPopCnt>(bb);
551 mob = (Piece != QUEEN ? count_1s_max_15<HasPopCnt>(b & no_mob_area)
552 : count_1s<HasPopCnt>(b & no_mob_area));
554 mobility += MobilityBonus[Piece][mob];
556 // Decrease score if we are attacked by an enemy pawn. Remaining part
557 // of threat evaluation must be done later when we have full attack info.
558 if (bit_is_set(ei.attackedBy[Them][PAWN], s))
559 bonus -= ThreatedByPawnPenalty[Piece];
561 // Bishop and knight outposts squares
562 if ((Piece == BISHOP || Piece == KNIGHT) && pos.square_is_weak(s, Us))
563 bonus += evaluate_outposts<Piece, Us>(pos, ei, s);
565 // Queen or rook on 7th rank
566 if ( (Piece == ROOK || Piece == QUEEN)
567 && relative_rank(Us, s) == RANK_7
568 && relative_rank(Us, pos.king_square(Them)) == RANK_8)
570 bonus += (Piece == ROOK ? RookOn7thBonus : QueenOn7thBonus);
573 // Special extra evaluation for rooks
576 // Open and half-open files
578 if (ei.pi->file_is_half_open(Us, f))
580 if (ei.pi->file_is_half_open(Them, f))
581 bonus += RookOpenFileBonus;
583 bonus += RookHalfOpenFileBonus;
586 // Penalize rooks which are trapped inside a king. Penalize more if
587 // king has lost right to castle.
588 if (mob > 6 || ei.pi->file_is_half_open(Us, f))
591 ksq = pos.king_square(Us);
593 if ( square_file(ksq) >= FILE_E
594 && square_file(s) > square_file(ksq)
595 && (relative_rank(Us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
597 // Is there a half-open file between the king and the edge of the board?
598 if (!ei.pi->has_open_file_to_right(Us, square_file(ksq)))
599 ei.value -= Sign[Us] * make_score(pos.can_castle(Us) ? (TrappedRookPenalty - mob * 16) / 2
600 : (TrappedRookPenalty - mob * 16), 0);
602 else if ( square_file(ksq) <= FILE_D
603 && square_file(s) < square_file(ksq)
604 && (relative_rank(Us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
606 // Is there a half-open file between the king and the edge of the board?
607 if (!ei.pi->has_open_file_to_left(Us, square_file(ksq)))
608 ei.value -= Sign[Us] * make_score(pos.can_castle(Us) ? (TrappedRookPenalty - mob * 16) / 2
609 : (TrappedRookPenalty - mob * 16), 0);
617 // evaluate_threats<>() assigns bonuses according to the type of attacking piece
618 // and the type of attacked one.
621 Score evaluate_threats(const Position& pos, EvalInfo& ei) {
623 const Color Them = (Us == WHITE ? BLACK : WHITE);
626 Score bonus = SCORE_ZERO;
628 // Enemy pieces not defended by a pawn and under our attack
629 Bitboard weakEnemies = pos.pieces_of_color(Them)
630 & ~ei.attackedBy[Them][PAWN]
631 & ei.attackedBy[Us][0];
635 // Add bonus according to type of attacked enemy pieces and to the
636 // type of attacking piece, from knights to queens. Kings are not
637 // considered because are already special handled in king evaluation.
638 for (PieceType pt1 = KNIGHT; pt1 < KING; pt1++)
640 b = ei.attackedBy[Us][pt1] & weakEnemies;
642 for (PieceType pt2 = PAWN; pt2 < KING; pt2++)
643 if (b & pos.pieces(pt2))
644 bonus += ThreatBonus[pt1][pt2];
650 // evaluate_pieces_of_color<>() assigns bonuses and penalties to all the
651 // pieces of a given color.
653 template<Color Us, bool HasPopCnt>
654 Score evaluate_pieces_of_color(const Position& pos, EvalInfo& ei, Score& mobility) {
656 const Color Them = (Us == WHITE ? BLACK : WHITE);
658 Score bonus = SCORE_ZERO;
660 mobility = SCORE_ZERO;
662 // Do not include in mobility squares protected by enemy pawns or occupied by our pieces
663 const Bitboard no_mob_area = ~(ei.attackedBy[Them][PAWN] | pos.pieces_of_color(Us));
665 bonus += evaluate_pieces<KNIGHT, Us, HasPopCnt>(pos, ei, mobility, no_mob_area);
666 bonus += evaluate_pieces<BISHOP, Us, HasPopCnt>(pos, ei, mobility, no_mob_area);
667 bonus += evaluate_pieces<ROOK, Us, HasPopCnt>(pos, ei, mobility, no_mob_area);
668 bonus += evaluate_pieces<QUEEN, Us, HasPopCnt>(pos, ei, mobility, no_mob_area);
670 // Sum up all attacked squares
671 ei.attackedBy[Us][0] = ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
672 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
673 | ei.attackedBy[Us][QUEEN] | ei.attackedBy[Us][KING];
678 // evaluate_king<>() assigns bonuses and penalties to a king of a given color
680 template<Color Us, bool HasPopCnt>
681 Score evaluate_king(const Position& pos, EvalInfo& ei, Value margins[]) {
683 const Color Them = (Us == WHITE ? BLACK : WHITE);
685 Bitboard undefended, b, b1, b2, safe;
688 const Square ksq = pos.king_square(Us);
691 Score bonus = ei.pi->king_shelter(pos, Us, ksq);
693 // King safety. This is quite complicated, and is almost certainly far
694 // from optimally tuned.
695 if ( pos.piece_count(Them, QUEEN) >= 1
696 && ei.kingAttackersCount[Them] >= 2
697 && pos.non_pawn_material(Them) >= QueenValueMidgame + RookValueMidgame
698 && ei.kingAdjacentZoneAttacksCount[Them])
700 // Is it the attackers turn to move?
701 sente = (Them == pos.side_to_move());
703 // Find the attacked squares around the king which has no defenders
704 // apart from the king itself
705 undefended = ei.attackedBy[Them][0] & ei.attackedBy[Us][KING];
706 undefended &= ~( ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
707 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
708 | ei.attackedBy[Us][QUEEN]);
710 // Initialize the 'attackUnits' variable, which is used later on as an
711 // index to the KingDangerTable[] array. The initial value is based on
712 // the number and types of the enemy's attacking pieces, the number of
713 // attacked and undefended squares around our king, the square of the
714 // king, and the quality of the pawn shelter.
715 attackUnits = Min(25, (ei.kingAttackersCount[Them] * ei.kingAttackersWeight[Them]) / 2)
716 + 3 * (ei.kingAdjacentZoneAttacksCount[Them] + count_1s_max_15<HasPopCnt>(undefended))
717 + InitKingDanger[relative_square(Us, ksq)]
718 - mg_value(ei.pi->king_shelter(pos, Us, ksq)) / 32;
720 // Analyse enemy's safe queen contact checks. First find undefended
721 // squares around the king attacked by enemy queen...
722 b = undefended & ei.attackedBy[Them][QUEEN] & ~pos.pieces_of_color(Them);
725 // ...then remove squares not supported by another enemy piece
726 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
727 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][ROOK]);
729 attackUnits += QueenContactCheckBonus * count_1s_max_15<HasPopCnt>(b) * (sente ? 2 : 1);
732 // Analyse enemy's safe distance checks for sliders and knights
733 safe = ~(pos.pieces_of_color(Them) | ei.attackedBy[Us][0]);
735 b1 = pos.attacks_from<ROOK>(ksq) & safe;
736 b2 = pos.attacks_from<BISHOP>(ksq) & safe;
738 // Enemy queen safe checks
739 b = (b1 | b2) & ei.attackedBy[Them][QUEEN];
741 attackUnits += QueenCheckBonus * count_1s_max_15<HasPopCnt>(b);
743 // Enemy rooks safe checks
744 b = b1 & ei.attackedBy[Them][ROOK];
746 attackUnits += RookCheckBonus * count_1s_max_15<HasPopCnt>(b);
748 // Enemy bishops safe checks
749 b = b2 & ei.attackedBy[Them][BISHOP];
751 attackUnits += BishopCheckBonus * count_1s_max_15<HasPopCnt>(b);
753 // Enemy knights safe checks
754 b = pos.attacks_from<KNIGHT>(ksq) & ei.attackedBy[Them][KNIGHT] & safe;
756 attackUnits += KnightCheckBonus * count_1s_max_15<HasPopCnt>(b);
758 // To index KingDangerTable[] attackUnits must be in [0, 99] range
759 attackUnits = Min(99, Max(0, attackUnits));
761 // Finally, extract the king danger score from the KingDangerTable[]
762 // array and subtract the score from evaluation. Set also margins[]
763 // value that will be used for pruning because this value can sometimes
764 // be very big, and so capturing a single attacking piece can therefore
765 // result in a score change far bigger than the value of the captured piece.
766 bonus -= KingDangerTable[Us][attackUnits];
767 margins[Us] += mg_value(KingDangerTable[Us][attackUnits]);
773 // evaluate_passed_pawns<>() evaluates the passed pawns of the given color
776 Score evaluate_passed_pawns(const Position& pos, EvalInfo& ei) {
778 const Color Them = (Us == WHITE ? BLACK : WHITE);
780 Score bonus = SCORE_ZERO;
781 Bitboard squaresToQueen, defendedSquares, unsafeSquares, supportingPawns;
782 Bitboard b = ei.pi->passed_pawns(Us);
788 Square s = pop_1st_bit(&b);
790 assert(pos.pawn_is_passed(Us, s));
792 int r = int(relative_rank(Us, s) - RANK_2);
793 int tr = r * (r - 1);
795 // Base bonus based on rank
796 Value mbonus = Value(20 * tr);
797 Value ebonus = Value(10 + r * r * 10);
801 Square blockSq = s + pawn_push(Us);
803 // Adjust bonus based on kings proximity
804 ebonus -= Value(square_distance(pos.king_square(Us), blockSq) * 3 * tr);
805 ebonus -= Value(square_distance(pos.king_square(Us), blockSq + pawn_push(Us)) * 1 * tr);
806 ebonus += Value(square_distance(pos.king_square(Them), blockSq) * 6 * tr);
808 // If the pawn is free to advance, increase bonus
809 if (pos.square_is_empty(blockSq))
811 squaresToQueen = squares_in_front_of(Us, s);
812 defendedSquares = squaresToQueen & ei.attackedBy[Us][0];
814 // If there is an enemy rook or queen attacking the pawn from behind,
815 // add all X-ray attacks by the rook or queen. Otherwise consider only
816 // the squares in the pawn's path attacked or occupied by the enemy.
817 if ( (squares_behind(Us, s) & pos.pieces(ROOK, QUEEN, Them))
818 && (squares_behind(Us, s) & pos.pieces(ROOK, QUEEN, Them) & pos.attacks_from<ROOK>(s)))
819 unsafeSquares = squaresToQueen;
821 unsafeSquares = squaresToQueen & (ei.attackedBy[Them][0] | pos.pieces_of_color(Them));
823 // If there aren't enemy attacks or pieces along the path to queen give
824 // huge bonus. Even bigger if we protect the pawn's path.
826 ebonus += Value(tr * (squaresToQueen == defendedSquares ? 17 : 15));
828 // OK, there are enemy attacks or pieces (but not pawns). Are those
829 // squares which are attacked by the enemy also attacked by us ?
830 // If yes, big bonus (but smaller than when there are no enemy attacks),
831 // if no, somewhat smaller bonus.
832 ebonus += Value(tr * ((unsafeSquares & defendedSquares) == unsafeSquares ? 13 : 8));
834 // At last, add a small bonus when there are no *friendly* pieces
835 // in the pawn's path.
836 if (!(squaresToQueen & pos.pieces_of_color(Us)))
841 // Increase the bonus if the passed pawn is supported by a friendly pawn
842 // on the same rank and a bit smaller if it's on the previous rank.
843 supportingPawns = pos.pieces(PAWN, Us) & neighboring_files_bb(s);
844 if (supportingPawns & rank_bb(s))
845 ebonus += Value(r * 20);
846 else if (supportingPawns & rank_bb(s - pawn_push(Us)))
847 ebonus += Value(r * 12);
849 // Rook pawns are a special case: They are sometimes worse, and
850 // sometimes better than other passed pawns. It is difficult to find
851 // good rules for determining whether they are good or bad. For now,
852 // we try the following: Increase the value for rook pawns if the
853 // other side has no pieces apart from a knight, and decrease the
854 // value if the other side has a rook or queen.
855 if (square_file(s) == FILE_A || square_file(s) == FILE_H)
857 if (pos.non_pawn_material(Them) <= KnightValueMidgame)
858 ebonus += ebonus / 4;
859 else if (pos.pieces(ROOK, QUEEN, Them))
860 ebonus -= ebonus / 4;
862 bonus += make_score(mbonus, ebonus);
866 // Add the scores to the middle game and endgame eval
867 return apply_weight(bonus, Weights[PassedPawns]);
871 // evaluate_space() computes the space evaluation for a given side. The
872 // space evaluation is a simple bonus based on the number of safe squares
873 // available for minor pieces on the central four files on ranks 2--4. Safe
874 // squares one, two or three squares behind a friendly pawn are counted
875 // twice. Finally, the space bonus is scaled by a weight taken from the
876 // material hash table.
877 template<Color Us, bool HasPopCnt>
878 int evaluate_space(const Position& pos, EvalInfo& ei) {
880 const Color Them = (Us == WHITE ? BLACK : WHITE);
882 // Find the safe squares for our pieces inside the area defined by
883 // SpaceMask[us]. A square is unsafe if it is attacked by an enemy
884 // pawn, or if it is undefended and attacked by an enemy piece.
885 Bitboard safe = SpaceMask[Us]
886 & ~pos.pieces(PAWN, Us)
887 & ~ei.attackedBy[Them][PAWN]
888 & (ei.attackedBy[Us][0] | ~ei.attackedBy[Them][0]);
890 // Find all squares which are at most three squares behind some friendly pawn
891 Bitboard behind = pos.pieces(PAWN, Us);
892 behind |= (Us == WHITE ? behind >> 8 : behind << 8);
893 behind |= (Us == WHITE ? behind >> 16 : behind << 16);
895 return count_1s_max_15<HasPopCnt>(safe) + count_1s_max_15<HasPopCnt>(behind & safe);
899 // apply_weight() applies an evaluation weight to a value trying to prevent overflow
901 inline Score apply_weight(Score v, Score w) {
902 return make_score((int(mg_value(v)) * mg_value(w)) / 0x100, (int(eg_value(v)) * eg_value(w)) / 0x100);
906 // scale_by_game_phase() interpolates between a middle game and an endgame score,
907 // based on game phase. It also scales the return value by a ScaleFactor array.
909 Value scale_by_game_phase(const Score& v, Phase ph, const ScaleFactor sf[]) {
911 assert(mg_value(v) > -VALUE_INFINITE && mg_value(v) < VALUE_INFINITE);
912 assert(eg_value(v) > -VALUE_INFINITE && eg_value(v) < VALUE_INFINITE);
913 assert(ph >= PHASE_ENDGAME && ph <= PHASE_MIDGAME);
915 Value eg = eg_value(v);
916 ScaleFactor f = sf[eg > VALUE_ZERO ? WHITE : BLACK];
917 Value ev = Value((eg * int(f)) / SCALE_FACTOR_NORMAL);
919 int result = (mg_value(v) * int(ph) + ev * int(128 - ph)) / 128;
920 return Value(result & ~(GrainSize - 1));
924 // weight_option() computes the value of an evaluation weight, by combining
925 // two UCI-configurable weights (midgame and endgame) with an internal weight.
927 Score weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight) {
929 // Scale option value from 100 to 256
930 int mg = get_option_value_int(mgOpt) * 256 / 100;
931 int eg = get_option_value_int(egOpt) * 256 / 100;
933 return apply_weight(make_score(mg, eg), internalWeight);
936 // init_safety() initizes the king safety evaluation, based on UCI
937 // parameters. It is called from read_weights().
941 const Value MaxSlope = Value(30);
942 const Value Peak = Value(1280);
945 // First setup the base table
946 for (int i = 0; i < 100; i++)
948 t[i] = Value(int(0.4 * i * i));
951 t[i] = Min(t[i], t[i - 1] + MaxSlope);
953 t[i] = Min(t[i], Peak);
956 // Then apply the weights and get the final KingDangerTable[] array
957 for (Color c = WHITE; c <= BLACK; c++)
958 for (int i = 0; i < 100; i++)
959 KingDangerTable[c][i] = apply_weight(make_score(t[i], 0), Weights[KingDangerUs + c]);