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 // updateKingTables[color] is set to true if we have enough material
49 // to trigger the opponent's king safety calculation. When is false we
50 // skip the time consuming update of the king attackers tables.
51 bool updateKingTables[2];
53 // attackedBy[color][piece type] is a bitboard representing all squares
54 // attacked by a given color and piece type, attackedBy[color][0] contains
55 // all squares attacked by the given color.
56 Bitboard attackedBy[2][8];
58 // kingZone[color] is the zone around the enemy king which is considered
59 // by the king safety evaluation. This consists of the squares directly
60 // adjacent to the king, and the three (or two, for a king on an edge file)
61 // squares two ranks in front of the king. For instance, if black's king
62 // is on g8, kingZone[WHITE] is a bitboard containing the squares f8, h8,
63 // f7, g7, h7, f6, g6 and h6.
66 // kingAttackersCount[color] is the number of pieces of the given color
67 // which attack a square in the kingZone of the enemy king.
68 int kingAttackersCount[2];
70 // kingAttackersWeight[color] is the sum of the "weight" of the pieces of the
71 // given color which attack a square in the kingZone of the enemy king. The
72 // weights of the individual piece types are given by the variables
73 // QueenAttackWeight, RookAttackWeight, BishopAttackWeight and
74 // KnightAttackWeight in evaluate.cpp
75 int kingAttackersWeight[2];
77 // kingAdjacentZoneAttacksCount[color] is the number of attacks to squares
78 // directly adjacent to the king of the given color. Pieces which attack
79 // more than one square are counted multiple times. For instance, if black's
80 // king is on g8 and there's a white knight on g5, this knight adds
81 // 2 to kingAdjacentZoneAttacksCount[BLACK].
82 int kingAdjacentZoneAttacksCount[2];
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[] = {
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 = 6;
203 const int RookContactCheckBonus = 4;
204 const int QueenCheckBonus = 3;
205 const int RookCheckBonus = 2;
206 const int BishopCheckBonus = 1;
207 const int KnightCheckBonus = 1;
209 // InitKingDanger[Square] contains penalties based on the position of the
210 // defending king, indexed by king's square (from white's point of view).
211 const int InitKingDanger[] = {
212 2, 0, 2, 5, 5, 2, 0, 2,
213 2, 2, 4, 8, 8, 4, 2, 2,
214 7, 10, 12, 12, 12, 12, 10, 7,
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,
219 15, 15, 15, 15, 15, 15, 15, 15
222 // KingDangerTable[Color][attackUnits] contains the actual king danger
223 // weighted scores, indexed by color and by a calculated integer number.
224 Score KingDangerTable[2][128];
226 // Pawn and material hash tables, indexed by the current thread id.
227 // Note that they will be initialized at 0 being global variables.
228 MaterialInfoTable* MaterialTable[MAX_THREADS];
229 PawnInfoTable* PawnTable[MAX_THREADS];
231 // Function prototypes
232 template<bool HasPopCnt>
233 Value do_evaluate(const Position& pos, Value& margin);
235 template<Color Us, bool HasPopCnt>
236 void init_eval_info(const Position& pos, EvalInfo& ei);
238 template<Color Us, bool HasPopCnt>
239 Score evaluate_pieces_of_color(const Position& pos, EvalInfo& ei, Score& mobility);
241 template<Color Us, bool HasPopCnt>
242 Score evaluate_king(const Position& pos, EvalInfo& ei, Value& margin);
245 Score evaluate_threats(const Position& pos, EvalInfo& ei);
247 template<Color Us, bool HasPopCnt>
248 int evaluate_space(const Position& pos, EvalInfo& ei);
251 Score evaluate_passed_pawns(const Position& pos, EvalInfo& ei);
253 Score apply_weight(Score v, Score weight);
254 Value scale_by_game_phase(const Score& v, Phase ph, ScaleFactor sf);
255 Score weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight);
265 /// Prefetches in pawn hash tables
267 void prefetchPawn(Key key, int threadID) {
269 PawnTable[threadID]->prefetch(key);
273 /// evaluate() is the main evaluation function. It always computes two
274 /// values, an endgame score and a middle game score, and interpolates
275 /// between them based on the remaining material.
276 Value evaluate(const Position& pos, Value& margin) {
278 return CpuHasPOPCNT ? do_evaluate<true>(pos, margin)
279 : do_evaluate<false>(pos, margin);
284 template<bool HasPopCnt>
285 Value do_evaluate(const Position& pos, Value& margin) {
288 Score mobilityWhite, mobilityBlack;
291 assert(pos.thread() >= 0 && pos.thread() < MAX_THREADS);
292 assert(!pos.is_check());
294 // Initialize value by reading the incrementally updated scores included
295 // in the position object (material + piece square tables).
296 Score bonus = pos.value();
298 // margin is the uncertainty estimation of position's evaluation
299 // and typically is used by the search for pruning decisions.
302 // Probe the material hash table
303 MaterialInfo* mi = MaterialTable[pos.thread()]->get_material_info(pos);
304 bonus += mi->material_value();
306 // If we have a specialized evaluation function for the current material
307 // configuration, call it and return.
308 if (mi->specialized_eval_exists())
309 return mi->evaluate(pos);
311 // Probe the pawn hash table
312 ei.pi = PawnTable[pos.thread()]->get_pawn_info(pos);
313 bonus += apply_weight(ei.pi->pawns_value(), Weights[PawnStructure]);
315 // Initialize attack and king safety bitboards
316 init_eval_info<WHITE, HasPopCnt>(pos, ei);
317 init_eval_info<BLACK, HasPopCnt>(pos, ei);
319 // Evaluate pieces and mobility
320 bonus += evaluate_pieces_of_color<WHITE, HasPopCnt>(pos, ei, mobilityWhite)
321 - evaluate_pieces_of_color<BLACK, HasPopCnt>(pos, ei, mobilityBlack);
323 bonus += apply_weight(mobilityWhite - mobilityBlack, Weights[Mobility]);
325 // Evaluate kings after all other pieces because we need complete attack
326 // information when computing the king safety evaluation.
327 bonus += evaluate_king<WHITE, HasPopCnt>(pos, ei, margin)
328 - evaluate_king<BLACK, HasPopCnt>(pos, ei, margin);
330 // Evaluate tactical threats, we need full attack information including king
331 bonus += evaluate_threats<WHITE>(pos, ei)
332 - evaluate_threats<BLACK>(pos, ei);
334 // Evaluate passed pawns, we need full attack information including king
335 bonus += evaluate_passed_pawns<WHITE>(pos, ei)
336 - evaluate_passed_pawns<BLACK>(pos, ei);
338 Phase phase = mi->game_phase();
340 // Evaluate space for both sides, only in middle-game.
341 if (phase > PHASE_ENDGAME && mi->space_weight() > 0)
343 int s = evaluate_space<WHITE, HasPopCnt>(pos, ei) - evaluate_space<BLACK, HasPopCnt>(pos, ei);
344 bonus += apply_weight(make_score(s * mi->space_weight(), 0), Weights[Space]);
347 // Scale winning side if position is more drawish that what it appears
348 ScaleFactor sf = eg_value(bonus) > VALUE_ZERO ? mi->scale_factor(pos, WHITE)
349 : mi->scale_factor(pos, BLACK);
351 // If we don't already have an unusual scale factor, check for opposite
352 // colored bishop endgames, and use a lower scale for those.
353 if ( phase < PHASE_MIDGAME
354 && pos.opposite_colored_bishops()
355 && sf == SCALE_FACTOR_NORMAL)
357 // Only the two bishops ?
358 if ( pos.non_pawn_material(WHITE) == BishopValueMidgame
359 && pos.non_pawn_material(BLACK) == BishopValueMidgame)
361 // Check for KBP vs KB with only a single pawn that is almost
362 // certainly a draw or at least two pawns.
363 bool one_pawn = (pos.piece_count(WHITE, PAWN) + pos.piece_count(BLACK, PAWN) == 1);
364 sf = one_pawn ? ScaleFactor(8) : ScaleFactor(32);
367 // Endgame with opposite-colored bishops, but also other pieces. Still
368 // a bit drawish, but not as drawish as with only the two bishops.
369 sf = ScaleFactor(50);
372 // Interpolate between the middle game and the endgame score
373 Value v = scale_by_game_phase(bonus, phase, sf);
374 return pos.side_to_move() == WHITE ? v : -v;
380 /// init_eval() initializes various tables used by the evaluation function
382 void init_eval(int threads) {
384 assert(threads <= MAX_THREADS);
386 for (int i = 0; i < MAX_THREADS; i++)
391 delete MaterialTable[i];
393 MaterialTable[i] = NULL;
397 PawnTable[i] = new PawnInfoTable();
399 if (!MaterialTable[i])
400 MaterialTable[i] = new MaterialInfoTable();
405 /// quit_eval() releases heap-allocated memory at program termination
413 /// read_weights() reads evaluation weights from the corresponding UCI parameters
415 void read_weights(Color us) {
417 // King safety is asymmetrical. Our king danger level is weighted by
418 // "Cowardice" UCI parameter, instead the opponent one by "Aggressiveness".
419 const int kingDangerUs = (us == WHITE ? KingDangerUs : KingDangerThem);
420 const int kingDangerThem = (us == WHITE ? KingDangerThem : KingDangerUs);
422 Weights[Mobility] = weight_option("Mobility (Middle Game)", "Mobility (Endgame)", WeightsInternal[Mobility]);
423 Weights[PawnStructure] = weight_option("Pawn Structure (Middle Game)", "Pawn Structure (Endgame)", WeightsInternal[PawnStructure]);
424 Weights[PassedPawns] = weight_option("Passed Pawns (Middle Game)", "Passed Pawns (Endgame)", WeightsInternal[PassedPawns]);
425 Weights[Space] = weight_option("Space", "Space", WeightsInternal[Space]);
426 Weights[kingDangerUs] = weight_option("Cowardice", "Cowardice", WeightsInternal[KingDangerUs]);
427 Weights[kingDangerThem] = weight_option("Aggressiveness", "Aggressiveness", WeightsInternal[KingDangerThem]);
429 // If running in analysis mode, make sure we use symmetrical king safety. We do this
430 // by replacing both Weights[kingDangerUs] and Weights[kingDangerThem] by their average.
431 if (get_option_value_bool("UCI_AnalyseMode"))
432 Weights[kingDangerUs] = Weights[kingDangerThem] = (Weights[kingDangerUs] + Weights[kingDangerThem]) / 2;
440 // init_eval_info() initializes king bitboards for given color adding
441 // pawn attacks. To be done at the beginning of the evaluation.
443 template<Color Us, bool HasPopCnt>
444 void init_eval_info(const Position& pos, EvalInfo& ei) {
446 const Color Them = (Us == WHITE ? BLACK : WHITE);
448 Bitboard b = ei.attackedBy[Them][KING] = pos.attacks_from<KING>(pos.king_square(Them));
449 ei.kingZone[Us] = (b | (Us == WHITE ? b >> 8 : b << 8));
450 ei.attackedBy[Us][PAWN] = ei.pi->pawn_attacks(Us);
451 ei.updateKingTables[Us] = pos.piece_count(Us, QUEEN) && pos.non_pawn_material(Us) >= QueenValueMidgame + RookValueMidgame;
452 if (ei.updateKingTables[Us])
454 b &= ei.attackedBy[Us][PAWN];
455 ei.kingAttackersCount[Us] = b ? count_1s_max_15<HasPopCnt>(b) / 2 : EmptyBoardBB;
456 ei.kingAdjacentZoneAttacksCount[Us] = ei.kingAttackersWeight[Us] = EmptyBoardBB;
461 // evaluate_outposts() evaluates bishop and knight outposts squares
463 template<PieceType Piece, Color Us>
464 Score evaluate_outposts(const Position& pos, EvalInfo& ei, Square s) {
466 const Color Them = (Us == WHITE ? BLACK : WHITE);
468 assert (Piece == BISHOP || Piece == KNIGHT);
470 // Initial bonus based on square
471 Value bonus = OutpostBonus[Piece == BISHOP][relative_square(Us, s)];
473 // Increase bonus if supported by pawn, especially if the opponent has
474 // no minor piece which can exchange the outpost piece.
475 if (bonus && bit_is_set(ei.attackedBy[Us][PAWN], s))
477 if ( pos.pieces(KNIGHT, Them) == EmptyBoardBB
478 && (SquaresByColorBB[square_color(s)] & pos.pieces(BISHOP, Them)) == EmptyBoardBB)
479 bonus += bonus + bonus / 2;
483 return make_score(bonus, bonus);
487 // evaluate_pieces<>() assigns bonuses and penalties to the pieces of a given color
489 template<PieceType Piece, Color Us, bool HasPopCnt>
490 Score evaluate_pieces(const Position& pos, EvalInfo& ei, Score& mobility, Bitboard mobilityArea) {
496 Score bonus = SCORE_ZERO;
498 const Color Them = (Us == WHITE ? BLACK : WHITE);
499 const Square* ptr = pos.piece_list_begin(Us, Piece);
501 ei.attackedBy[Us][Piece] = EmptyBoardBB;
503 while ((s = *ptr++) != SQ_NONE)
505 // Find attacked squares, including x-ray attacks for bishops and rooks
506 if (Piece == KNIGHT || Piece == QUEEN)
507 b = pos.attacks_from<Piece>(s);
508 else if (Piece == BISHOP)
509 b = bishop_attacks_bb(s, pos.occupied_squares() & ~pos.pieces(QUEEN, Us));
510 else if (Piece == ROOK)
511 b = rook_attacks_bb(s, pos.occupied_squares() & ~pos.pieces(ROOK, QUEEN, Us));
515 // Update attack info
516 ei.attackedBy[Us][Piece] |= b;
519 if (ei.updateKingTables[Us] && (b & ei.kingZone[Us]))
521 ei.kingAttackersCount[Us]++;
522 ei.kingAttackersWeight[Us] += KingAttackWeights[Piece];
523 Bitboard bb = (b & ei.attackedBy[Them][KING]);
525 ei.kingAdjacentZoneAttacksCount[Us] += count_1s_max_15<HasPopCnt>(bb);
529 mob = (Piece != QUEEN ? count_1s_max_15<HasPopCnt>(b & mobilityArea)
530 : count_1s<HasPopCnt>(b & mobilityArea));
532 mobility += MobilityBonus[Piece][mob];
534 // Decrease score if we are attacked by an enemy pawn. Remaining part
535 // of threat evaluation must be done later when we have full attack info.
536 if (bit_is_set(ei.attackedBy[Them][PAWN], s))
537 bonus -= ThreatedByPawnPenalty[Piece];
539 // Bishop and knight outposts squares
540 if ((Piece == BISHOP || Piece == KNIGHT) && pos.square_is_weak(s, Us))
541 bonus += evaluate_outposts<Piece, Us>(pos, ei, s);
543 // Queen or rook on 7th rank
544 if ( (Piece == ROOK || Piece == QUEEN)
545 && relative_rank(Us, s) == RANK_7
546 && relative_rank(Us, pos.king_square(Them)) == RANK_8)
548 bonus += (Piece == ROOK ? RookOn7thBonus : QueenOn7thBonus);
551 // Special extra evaluation for rooks
554 // Open and half-open files
556 if (ei.pi->file_is_half_open(Us, f))
558 if (ei.pi->file_is_half_open(Them, f))
559 bonus += RookOpenFileBonus;
561 bonus += RookHalfOpenFileBonus;
564 // Penalize rooks which are trapped inside a king. Penalize more if
565 // king has lost right to castle.
566 if (mob > 6 || ei.pi->file_is_half_open(Us, f))
569 ksq = pos.king_square(Us);
571 if ( square_file(ksq) >= FILE_E
572 && square_file(s) > square_file(ksq)
573 && (relative_rank(Us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
575 // Is there a half-open file between the king and the edge of the board?
576 if (!ei.pi->has_open_file_to_right(Us, square_file(ksq)))
577 bonus -= make_score(pos.can_castle(Us) ? (TrappedRookPenalty - mob * 16) / 2
578 : (TrappedRookPenalty - mob * 16), 0);
580 else if ( square_file(ksq) <= FILE_D
581 && square_file(s) < square_file(ksq)
582 && (relative_rank(Us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
584 // Is there a half-open file between the king and the edge of the board?
585 if (!ei.pi->has_open_file_to_left(Us, square_file(ksq)))
586 bonus -= make_score(pos.can_castle(Us) ? (TrappedRookPenalty - mob * 16) / 2
587 : (TrappedRookPenalty - mob * 16), 0);
595 // evaluate_threats<>() assigns bonuses according to the type of attacking piece
596 // and the type of attacked one.
599 Score evaluate_threats(const Position& pos, EvalInfo& ei) {
601 const Color Them = (Us == WHITE ? BLACK : WHITE);
604 Score bonus = SCORE_ZERO;
606 // Enemy pieces not defended by a pawn and under our attack
607 Bitboard weakEnemies = pos.pieces_of_color(Them)
608 & ~ei.attackedBy[Them][PAWN]
609 & ei.attackedBy[Us][0];
613 // Add bonus according to type of attacked enemy piece and to the
614 // type of attacking piece, from knights to queens. Kings are not
615 // considered because are already handled in king evaluation.
616 for (PieceType pt1 = KNIGHT; pt1 < KING; pt1++)
618 b = ei.attackedBy[Us][pt1] & weakEnemies;
620 for (PieceType pt2 = PAWN; pt2 < KING; pt2++)
621 if (b & pos.pieces(pt2))
622 bonus += ThreatBonus[pt1][pt2];
628 // evaluate_pieces_of_color<>() assigns bonuses and penalties to all the
629 // pieces of a given color.
631 template<Color Us, bool HasPopCnt>
632 Score evaluate_pieces_of_color(const Position& pos, EvalInfo& ei, Score& mobility) {
634 const Color Them = (Us == WHITE ? BLACK : WHITE);
636 Score bonus = mobility = SCORE_ZERO;
638 // Do not include in mobility squares protected by enemy pawns or occupied by our pieces
639 const Bitboard mobilityArea = ~(ei.attackedBy[Them][PAWN] | pos.pieces_of_color(Us));
641 bonus += evaluate_pieces<KNIGHT, Us, HasPopCnt>(pos, ei, mobility, mobilityArea);
642 bonus += evaluate_pieces<BISHOP, Us, HasPopCnt>(pos, ei, mobility, mobilityArea);
643 bonus += evaluate_pieces<ROOK, Us, HasPopCnt>(pos, ei, mobility, mobilityArea);
644 bonus += evaluate_pieces<QUEEN, Us, HasPopCnt>(pos, ei, mobility, mobilityArea);
646 // Sum up all attacked squares
647 ei.attackedBy[Us][0] = ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
648 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
649 | ei.attackedBy[Us][QUEEN] | ei.attackedBy[Us][KING];
654 // evaluate_king<>() assigns bonuses and penalties to a king of a given color
656 template<Color Us, bool HasPopCnt>
657 Score evaluate_king(const Position& pos, EvalInfo& ei, Value& margin) {
659 const Color Them = (Us == WHITE ? BLACK : WHITE);
661 Bitboard undefended, b, b1, b2, safe;
663 const Square ksq = pos.king_square(Us);
666 Score bonus = ei.pi->king_shelter<Us>(pos, ksq);
668 // King safety. This is quite complicated, and is almost certainly far
669 // from optimally tuned.
670 if ( ei.updateKingTables[Them]
671 && ei.kingAttackersCount[Them] >= 2
672 && ei.kingAdjacentZoneAttacksCount[Them])
674 // Find the attacked squares around the king which has no defenders
675 // apart from the king itself
676 undefended = ei.attackedBy[Them][0] & ei.attackedBy[Us][KING];
677 undefended &= ~( ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
678 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
679 | ei.attackedBy[Us][QUEEN]);
681 // Initialize the 'attackUnits' variable, which is used later on as an
682 // index to the KingDangerTable[] array. The initial value is based on
683 // the number and types of the enemy's attacking pieces, the number of
684 // attacked and undefended squares around our king, the square of the
685 // king, and the quality of the pawn shelter.
686 attackUnits = Min(25, (ei.kingAttackersCount[Them] * ei.kingAttackersWeight[Them]) / 2)
687 + 3 * (ei.kingAdjacentZoneAttacksCount[Them] + count_1s_max_15<HasPopCnt>(undefended))
688 + InitKingDanger[relative_square(Us, ksq)]
689 - mg_value(ei.pi->king_shelter<Us>(pos, ksq)) / 32;
691 // Analyse enemy's safe queen contact checks. First find undefended
692 // squares around the king attacked by enemy queen...
693 b = undefended & ei.attackedBy[Them][QUEEN] & ~pos.pieces_of_color(Them);
696 // ...then remove squares not supported by another enemy piece
697 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
698 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][ROOK]);
700 attackUnits += QueenContactCheckBonus
701 * count_1s_max_15<HasPopCnt>(b)
702 * (Them == pos.side_to_move() ? 2 : 1);
705 // Analyse enemy's safe rook contact checks. First find undefended
706 // squares around the king attacked by enemy rooks...
707 b = undefended & ei.attackedBy[Them][ROOK] & ~pos.pieces_of_color(Them);
709 // Consider only squares where the enemy rook gives check
710 b &= RookPseudoAttacks[ksq];
714 // ...then remove squares not supported by another enemy piece
715 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
716 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][QUEEN]);
718 attackUnits += RookContactCheckBonus
719 * count_1s_max_15<HasPopCnt>(b)
720 * (Them == pos.side_to_move() ? 2 : 1);
723 // Analyse enemy's safe distance checks for sliders and knights
724 safe = ~(pos.pieces_of_color(Them) | ei.attackedBy[Us][0]);
726 b1 = pos.attacks_from<ROOK>(ksq) & safe;
727 b2 = pos.attacks_from<BISHOP>(ksq) & safe;
729 // Enemy queen safe checks
730 b = (b1 | b2) & ei.attackedBy[Them][QUEEN];
732 attackUnits += QueenCheckBonus * count_1s_max_15<HasPopCnt>(b);
734 // Enemy rooks safe checks
735 b = b1 & ei.attackedBy[Them][ROOK];
737 attackUnits += RookCheckBonus * count_1s_max_15<HasPopCnt>(b);
739 // Enemy bishops safe checks
740 b = b2 & ei.attackedBy[Them][BISHOP];
742 attackUnits += BishopCheckBonus * count_1s_max_15<HasPopCnt>(b);
744 // Enemy knights safe checks
745 b = pos.attacks_from<KNIGHT>(ksq) & ei.attackedBy[Them][KNIGHT] & safe;
747 attackUnits += KnightCheckBonus * count_1s_max_15<HasPopCnt>(b);
749 // To index KingDangerTable[] attackUnits must be in [0, 99] range
750 attackUnits = Min(99, Max(0, attackUnits));
752 // Finally, extract the king danger score from the KingDangerTable[]
753 // array and subtract the score from evaluation. Set also margins[]
754 // value that will be used for pruning because this value can sometimes
755 // be very big, and so capturing a single attacking piece can therefore
756 // result in a score change far bigger than the value of the captured piece.
757 bonus -= KingDangerTable[Us][attackUnits];
758 if (pos.side_to_move() == Us)
759 margin += mg_value(KingDangerTable[Us][attackUnits]);
765 // evaluate_passed_pawns<>() evaluates the passed pawns of the given color
768 Score evaluate_passed_pawns(const Position& pos, EvalInfo& ei) {
770 const Color Them = (Us == WHITE ? BLACK : WHITE);
772 Score bonus = SCORE_ZERO;
773 Bitboard squaresToQueen, defendedSquares, unsafeSquares, supportingPawns;
774 Bitboard b = ei.pi->passed_pawns(Us);
780 Square s = pop_1st_bit(&b);
782 assert(pos.pawn_is_passed(Us, s));
784 int r = int(relative_rank(Us, s) - RANK_2);
785 int rr = r * (r - 1);
787 // Base bonus based on rank
788 Value mbonus = Value(20 * rr);
789 Value ebonus = Value(10 * (rr + r + 1));
793 Square blockSq = s + pawn_push(Us);
795 // Adjust bonus based on kings proximity
796 ebonus -= Value(square_distance(pos.king_square(Us), blockSq) * 3 * rr);
797 ebonus -= Value(square_distance(pos.king_square(Us), blockSq + pawn_push(Us)) * rr);
798 ebonus += Value(square_distance(pos.king_square(Them), blockSq) * 6 * rr);
800 // If the pawn is free to advance, increase bonus
801 if (pos.square_is_empty(blockSq))
803 squaresToQueen = squares_in_front_of(Us, s);
804 defendedSquares = squaresToQueen & ei.attackedBy[Us][0];
806 // If there is an enemy rook or queen attacking the pawn from behind,
807 // add all X-ray attacks by the rook or queen. Otherwise consider only
808 // the squares in the pawn's path attacked or occupied by the enemy.
809 if ( (squares_behind(Us, s) & pos.pieces(ROOK, QUEEN, Them))
810 && (squares_behind(Us, s) & pos.pieces(ROOK, QUEEN, Them) & pos.attacks_from<ROOK>(s)))
811 unsafeSquares = squaresToQueen;
813 unsafeSquares = squaresToQueen & (ei.attackedBy[Them][0] | pos.pieces_of_color(Them));
815 // If there aren't enemy attacks or pieces along the path to queen give
816 // huge bonus. Even bigger if we protect the pawn's path.
818 ebonus += Value(rr * (squaresToQueen == defendedSquares ? 17 : 15));
820 // OK, there are enemy attacks or pieces (but not pawns). Are those
821 // squares which are attacked by the enemy also attacked by us ?
822 // If yes, big bonus (but smaller than when there are no enemy attacks),
823 // if no, somewhat smaller bonus.
824 ebonus += Value(rr * ((unsafeSquares & defendedSquares) == unsafeSquares ? 13 : 8));
826 // At last, add a small bonus when there are no *friendly* pieces
827 // in the pawn's path.
828 if (!(squaresToQueen & pos.pieces_of_color(Us)))
833 // Increase the bonus if the passed pawn is supported by a friendly pawn
834 // on the same rank and a bit smaller if it's on the previous rank.
835 supportingPawns = pos.pieces(PAWN, Us) & neighboring_files_bb(s);
836 if (supportingPawns & rank_bb(s))
837 ebonus += Value(r * 20);
838 else if (supportingPawns & rank_bb(s - pawn_push(Us)))
839 ebonus += Value(r * 12);
841 // Rook pawns are a special case: They are sometimes worse, and
842 // sometimes better than other passed pawns. It is difficult to find
843 // good rules for determining whether they are good or bad. For now,
844 // we try the following: Increase the value for rook pawns if the
845 // other side has no pieces apart from a knight, and decrease the
846 // value if the other side has a rook or queen.
847 if (square_file(s) == FILE_A || square_file(s) == FILE_H)
849 if (pos.non_pawn_material(Them) <= KnightValueMidgame)
850 ebonus += ebonus / 4;
851 else if (pos.pieces(ROOK, QUEEN, Them))
852 ebonus -= ebonus / 4;
854 bonus += make_score(mbonus, ebonus);
858 // Add the scores to the middle game and endgame eval
859 return apply_weight(bonus, Weights[PassedPawns]);
863 // evaluate_space() computes the space evaluation for a given side. The
864 // space evaluation is a simple bonus based on the number of safe squares
865 // available for minor pieces on the central four files on ranks 2--4. Safe
866 // squares one, two or three squares behind a friendly pawn are counted
867 // twice. Finally, the space bonus is scaled by a weight taken from the
868 // material hash table. The aim is to improve play on game opening.
869 template<Color Us, bool HasPopCnt>
870 int evaluate_space(const Position& pos, EvalInfo& ei) {
872 const Color Them = (Us == WHITE ? BLACK : WHITE);
874 // Find the safe squares for our pieces inside the area defined by
875 // SpaceMask[]. A square is unsafe if it is attacked by an enemy
876 // pawn, or if it is undefended and attacked by an enemy piece.
877 Bitboard safe = SpaceMask[Us]
878 & ~pos.pieces(PAWN, Us)
879 & ~ei.attackedBy[Them][PAWN]
880 & (ei.attackedBy[Us][0] | ~ei.attackedBy[Them][0]);
882 // Find all squares which are at most three squares behind some friendly pawn
883 Bitboard behind = pos.pieces(PAWN, Us);
884 behind |= (Us == WHITE ? behind >> 8 : behind << 8);
885 behind |= (Us == WHITE ? behind >> 16 : behind << 16);
887 return count_1s_max_15<HasPopCnt>(safe) + count_1s_max_15<HasPopCnt>(behind & safe);
891 // apply_weight() applies an evaluation weight to a value trying to prevent overflow
893 inline Score apply_weight(Score v, Score w) {
894 return make_score((int(mg_value(v)) * mg_value(w)) / 0x100,
895 (int(eg_value(v)) * eg_value(w)) / 0x100);
899 // scale_by_game_phase() interpolates between a middle game and an endgame score,
900 // based on game phase. It also scales the return value by a ScaleFactor array.
902 Value scale_by_game_phase(const Score& v, Phase ph, ScaleFactor sf) {
904 assert(mg_value(v) > -VALUE_INFINITE && mg_value(v) < VALUE_INFINITE);
905 assert(eg_value(v) > -VALUE_INFINITE && eg_value(v) < VALUE_INFINITE);
906 assert(ph >= PHASE_ENDGAME && ph <= PHASE_MIDGAME);
908 Value eg = eg_value(v);
909 Value ev = Value((eg * int(sf)) / SCALE_FACTOR_NORMAL);
911 int result = (mg_value(v) * int(ph) + ev * int(128 - ph)) / 128;
912 return Value(result & ~(GrainSize - 1));
916 // weight_option() computes the value of an evaluation weight, by combining
917 // two UCI-configurable weights (midgame and endgame) with an internal weight.
919 Score weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight) {
921 // Scale option value from 100 to 256
922 int mg = get_option_value_int(mgOpt) * 256 / 100;
923 int eg = get_option_value_int(egOpt) * 256 / 100;
925 return apply_weight(make_score(mg, eg), internalWeight);
929 // init_safety() initizes the king safety evaluation, based on UCI
930 // parameters. It is called from read_weights().
934 const Value MaxSlope = Value(30);
935 const Value Peak = Value(1280);
938 // First setup the base table
939 for (int i = 0; i < 100; i++)
941 t[i] = Value(int(0.4 * i * i));
944 t[i] = Min(t[i], t[i - 1] + MaxSlope);
946 t[i] = Min(t[i], Peak);
949 // Then apply the weights and get the final KingDangerTable[] array
950 for (Color c = WHITE; c <= BLACK; c++)
951 for (int i = 0; i < 100; i++)
952 KingDangerTable[c][i] = apply_weight(make_score(t[i], 0), Weights[KingDangerUs + c]);