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, const 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 ScaleFactor factor[2];
289 Score mobilityWhite, mobilityBlack;
292 assert(pos.thread() >= 0 && pos.thread() < MAX_THREADS);
293 assert(!pos.is_check());
295 // Initialize value by reading the incrementally updated scores included
296 // in the position object (material + piece square tables).
297 Score bonus = pos.value();
299 // margin is the uncertainty estimation of position's evaluation
300 // and typically is used by the search for pruning decisions.
303 // Probe the material hash table
304 MaterialInfo* mi = MaterialTable[pos.thread()]->get_material_info(pos);
305 bonus += mi->material_value();
307 // If we have a specialized evaluation function for the current material
308 // configuration, call it and return.
309 if (mi->specialized_eval_exists())
310 return mi->evaluate(pos);
312 // After get_material_info() call that modifies them
313 factor[WHITE] = mi->scale_factor(pos, WHITE);
314 factor[BLACK] = mi->scale_factor(pos, BLACK);
316 // Probe the pawn hash table
317 ei.pi = PawnTable[pos.thread()]->get_pawn_info(pos);
318 bonus += apply_weight(ei.pi->pawns_value(), Weights[PawnStructure]);
320 // Initialize attack and king safety bitboards
321 init_eval_info<WHITE, HasPopCnt>(pos, ei);
322 init_eval_info<BLACK, HasPopCnt>(pos, ei);
324 // Evaluate pieces and mobility
325 bonus += evaluate_pieces_of_color<WHITE, HasPopCnt>(pos, ei, mobilityWhite)
326 - evaluate_pieces_of_color<BLACK, HasPopCnt>(pos, ei, mobilityBlack);
328 bonus += apply_weight(mobilityWhite - mobilityBlack, Weights[Mobility]);
330 // Evaluate kings after all other pieces because we need complete attack
331 // information when computing the king safety evaluation.
332 bonus += evaluate_king<WHITE, HasPopCnt>(pos, ei, margin)
333 - evaluate_king<BLACK, HasPopCnt>(pos, ei, margin);
335 // Evaluate tactical threats, we need full attack information including king
336 bonus += evaluate_threats<WHITE>(pos, ei)
337 - evaluate_threats<BLACK>(pos, ei);
339 // Evaluate passed pawns, we need full attack information including king
340 bonus += evaluate_passed_pawns<WHITE>(pos, ei)
341 - evaluate_passed_pawns<BLACK>(pos, ei);
343 Phase phase = mi->game_phase();
345 // Evaluate space for both sides, only in middle-game.
346 if (phase > PHASE_ENDGAME && mi->space_weight() > 0)
348 int s = evaluate_space<WHITE, HasPopCnt>(pos, ei) - evaluate_space<BLACK, HasPopCnt>(pos, ei);
349 bonus += apply_weight(make_score(s * mi->space_weight(), 0), Weights[Space]);
352 // If we don't already have an unusual scale factor, check for opposite
353 // colored bishop endgames, and use a lower scale for those
354 if ( phase < PHASE_MIDGAME
355 && pos.opposite_colored_bishops()
356 && ( (factor[WHITE] == SCALE_FACTOR_NORMAL && eg_value(bonus) > VALUE_ZERO)
357 || (factor[BLACK] == SCALE_FACTOR_NORMAL && eg_value(bonus) < VALUE_ZERO)))
361 // Only the two bishops ?
362 if ( pos.non_pawn_material(WHITE) == BishopValueMidgame
363 && pos.non_pawn_material(BLACK) == BishopValueMidgame)
365 // Check for KBP vs KB with only a single pawn that is almost
366 // certainly a draw or at least two pawns.
367 bool one_pawn = (pos.piece_count(WHITE, PAWN) + pos.piece_count(BLACK, PAWN) == 1);
368 sf = one_pawn ? ScaleFactor(8) : ScaleFactor(32);
371 // Endgame with opposite-colored bishops, but also other pieces. Still
372 // a bit drawish, but not as drawish as with only the two bishops.
373 sf = ScaleFactor(50);
375 if (factor[WHITE] == SCALE_FACTOR_NORMAL)
377 if (factor[BLACK] == SCALE_FACTOR_NORMAL)
381 // Interpolate between the middle game and the endgame score
382 Value v = scale_by_game_phase(bonus, phase, factor);
383 return pos.side_to_move() == WHITE ? v : -v;
389 /// init_eval() initializes various tables used by the evaluation function
391 void init_eval(int threads) {
393 assert(threads <= MAX_THREADS);
395 for (int i = 0; i < MAX_THREADS; i++)
400 delete MaterialTable[i];
402 MaterialTable[i] = NULL;
406 PawnTable[i] = new PawnInfoTable();
408 if (!MaterialTable[i])
409 MaterialTable[i] = new MaterialInfoTable();
414 /// quit_eval() releases heap-allocated memory at program termination
422 /// read_weights() reads evaluation weights from the corresponding UCI parameters
424 void read_weights(Color us) {
426 // King safety is asymmetrical. Our king danger level is weighted by
427 // "Cowardice" UCI parameter, instead the opponent one by "Aggressiveness".
428 const int kingDangerUs = (us == WHITE ? KingDangerUs : KingDangerThem);
429 const int kingDangerThem = (us == WHITE ? KingDangerThem : KingDangerUs);
431 Weights[Mobility] = weight_option("Mobility (Middle Game)", "Mobility (Endgame)", WeightsInternal[Mobility]);
432 Weights[PawnStructure] = weight_option("Pawn Structure (Middle Game)", "Pawn Structure (Endgame)", WeightsInternal[PawnStructure]);
433 Weights[PassedPawns] = weight_option("Passed Pawns (Middle Game)", "Passed Pawns (Endgame)", WeightsInternal[PassedPawns]);
434 Weights[Space] = weight_option("Space", "Space", WeightsInternal[Space]);
435 Weights[kingDangerUs] = weight_option("Cowardice", "Cowardice", WeightsInternal[KingDangerUs]);
436 Weights[kingDangerThem] = weight_option("Aggressiveness", "Aggressiveness", WeightsInternal[KingDangerThem]);
438 // If running in analysis mode, make sure we use symmetrical king safety. We do this
439 // by replacing both Weights[kingDangerUs] and Weights[kingDangerThem] by their average.
440 if (get_option_value_bool("UCI_AnalyseMode"))
441 Weights[kingDangerUs] = Weights[kingDangerThem] = (Weights[kingDangerUs] + Weights[kingDangerThem]) / 2;
449 // init_eval_info() initializes king bitboards for given color adding
450 // pawn attacks. To be done at the beginning of the evaluation.
452 template<Color Us, bool HasPopCnt>
453 void init_eval_info(const Position& pos, EvalInfo& ei) {
455 const Color Them = (Us == WHITE ? BLACK : WHITE);
457 Bitboard b = ei.attackedBy[Them][KING] = pos.attacks_from<KING>(pos.king_square(Them));
458 ei.kingZone[Us] = (b | (Us == WHITE ? b >> 8 : b << 8));
459 ei.attackedBy[Us][PAWN] = ei.pi->pawn_attacks(Us);
460 ei.updateKingTables[Us] = pos.piece_count(Us, QUEEN) && pos.non_pawn_material(Us) >= QueenValueMidgame + RookValueMidgame;
461 if (ei.updateKingTables[Us])
463 b &= ei.attackedBy[Us][PAWN];
464 ei.kingAttackersCount[Us] = b ? count_1s_max_15<HasPopCnt>(b) / 2 : EmptyBoardBB;
465 ei.kingAdjacentZoneAttacksCount[Us] = ei.kingAttackersWeight[Us] = EmptyBoardBB;
470 // evaluate_outposts() evaluates bishop and knight outposts squares
472 template<PieceType Piece, Color Us>
473 Score evaluate_outposts(const Position& pos, EvalInfo& ei, Square s) {
475 const Color Them = (Us == WHITE ? BLACK : WHITE);
477 assert (Piece == BISHOP || Piece == KNIGHT);
479 // Initial bonus based on square
480 Value bonus = OutpostBonus[Piece == BISHOP][relative_square(Us, s)];
482 // Increase bonus if supported by pawn, especially if the opponent has
483 // no minor piece which can exchange the outpost piece.
484 if (bonus && bit_is_set(ei.attackedBy[Us][PAWN], s))
486 if ( pos.pieces(KNIGHT, Them) == EmptyBoardBB
487 && (SquaresByColorBB[square_color(s)] & pos.pieces(BISHOP, Them)) == EmptyBoardBB)
488 bonus += bonus + bonus / 2;
492 return make_score(bonus, bonus);
496 // evaluate_pieces<>() assigns bonuses and penalties to the pieces of a given color
498 template<PieceType Piece, Color Us, bool HasPopCnt>
499 Score evaluate_pieces(const Position& pos, EvalInfo& ei, Score& mobility, Bitboard mobilityArea) {
505 Score bonus = SCORE_ZERO;
507 const Color Them = (Us == WHITE ? BLACK : WHITE);
508 const Square* ptr = pos.piece_list_begin(Us, Piece);
510 ei.attackedBy[Us][Piece] = EmptyBoardBB;
512 while ((s = *ptr++) != SQ_NONE)
514 // Find attacked squares, including x-ray attacks for bishops and rooks
515 if (Piece == KNIGHT || Piece == QUEEN)
516 b = pos.attacks_from<Piece>(s);
517 else if (Piece == BISHOP)
518 b = bishop_attacks_bb(s, pos.occupied_squares() & ~pos.pieces(QUEEN, Us));
519 else if (Piece == ROOK)
520 b = rook_attacks_bb(s, pos.occupied_squares() & ~pos.pieces(ROOK, QUEEN, Us));
524 // Update attack info
525 ei.attackedBy[Us][Piece] |= b;
528 if (ei.updateKingTables[Us] && (b & ei.kingZone[Us]))
530 ei.kingAttackersCount[Us]++;
531 ei.kingAttackersWeight[Us] += KingAttackWeights[Piece];
532 Bitboard bb = (b & ei.attackedBy[Them][KING]);
534 ei.kingAdjacentZoneAttacksCount[Us] += count_1s_max_15<HasPopCnt>(bb);
538 mob = (Piece != QUEEN ? count_1s_max_15<HasPopCnt>(b & mobilityArea)
539 : count_1s<HasPopCnt>(b & mobilityArea));
541 mobility += MobilityBonus[Piece][mob];
543 // Decrease score if we are attacked by an enemy pawn. Remaining part
544 // of threat evaluation must be done later when we have full attack info.
545 if (bit_is_set(ei.attackedBy[Them][PAWN], s))
546 bonus -= ThreatedByPawnPenalty[Piece];
548 // Bishop and knight outposts squares
549 if ((Piece == BISHOP || Piece == KNIGHT) && pos.square_is_weak(s, Us))
550 bonus += evaluate_outposts<Piece, Us>(pos, ei, s);
552 // Queen or rook on 7th rank
553 if ( (Piece == ROOK || Piece == QUEEN)
554 && relative_rank(Us, s) == RANK_7
555 && relative_rank(Us, pos.king_square(Them)) == RANK_8)
557 bonus += (Piece == ROOK ? RookOn7thBonus : QueenOn7thBonus);
560 // Special extra evaluation for rooks
563 // Open and half-open files
565 if (ei.pi->file_is_half_open(Us, f))
567 if (ei.pi->file_is_half_open(Them, f))
568 bonus += RookOpenFileBonus;
570 bonus += RookHalfOpenFileBonus;
573 // Penalize rooks which are trapped inside a king. Penalize more if
574 // king has lost right to castle.
575 if (mob > 6 || ei.pi->file_is_half_open(Us, f))
578 ksq = pos.king_square(Us);
580 if ( square_file(ksq) >= FILE_E
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_right(Us, square_file(ksq)))
586 bonus -= make_score(pos.can_castle(Us) ? (TrappedRookPenalty - mob * 16) / 2
587 : (TrappedRookPenalty - mob * 16), 0);
589 else if ( square_file(ksq) <= FILE_D
590 && square_file(s) < square_file(ksq)
591 && (relative_rank(Us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
593 // Is there a half-open file between the king and the edge of the board?
594 if (!ei.pi->has_open_file_to_left(Us, square_file(ksq)))
595 bonus -= make_score(pos.can_castle(Us) ? (TrappedRookPenalty - mob * 16) / 2
596 : (TrappedRookPenalty - mob * 16), 0);
604 // evaluate_threats<>() assigns bonuses according to the type of attacking piece
605 // and the type of attacked one.
608 Score evaluate_threats(const Position& pos, EvalInfo& ei) {
610 const Color Them = (Us == WHITE ? BLACK : WHITE);
613 Score bonus = SCORE_ZERO;
615 // Enemy pieces not defended by a pawn and under our attack
616 Bitboard weakEnemies = pos.pieces_of_color(Them)
617 & ~ei.attackedBy[Them][PAWN]
618 & ei.attackedBy[Us][0];
622 // Add bonus according to type of attacked enemy piece and to the
623 // type of attacking piece, from knights to queens. Kings are not
624 // considered because are already handled in king evaluation.
625 for (PieceType pt1 = KNIGHT; pt1 < KING; pt1++)
627 b = ei.attackedBy[Us][pt1] & weakEnemies;
629 for (PieceType pt2 = PAWN; pt2 < KING; pt2++)
630 if (b & pos.pieces(pt2))
631 bonus += ThreatBonus[pt1][pt2];
637 // evaluate_pieces_of_color<>() assigns bonuses and penalties to all the
638 // pieces of a given color.
640 template<Color Us, bool HasPopCnt>
641 Score evaluate_pieces_of_color(const Position& pos, EvalInfo& ei, Score& mobility) {
643 const Color Them = (Us == WHITE ? BLACK : WHITE);
645 Score bonus = mobility = SCORE_ZERO;
647 // Do not include in mobility squares protected by enemy pawns or occupied by our pieces
648 const Bitboard mobilityArea = ~(ei.attackedBy[Them][PAWN] | pos.pieces_of_color(Us));
650 bonus += evaluate_pieces<KNIGHT, Us, HasPopCnt>(pos, ei, mobility, mobilityArea);
651 bonus += evaluate_pieces<BISHOP, Us, HasPopCnt>(pos, ei, mobility, mobilityArea);
652 bonus += evaluate_pieces<ROOK, Us, HasPopCnt>(pos, ei, mobility, mobilityArea);
653 bonus += evaluate_pieces<QUEEN, Us, HasPopCnt>(pos, ei, mobility, mobilityArea);
655 // Sum up all attacked squares
656 ei.attackedBy[Us][0] = ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
657 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
658 | ei.attackedBy[Us][QUEEN] | ei.attackedBy[Us][KING];
663 // evaluate_king<>() assigns bonuses and penalties to a king of a given color
665 template<Color Us, bool HasPopCnt>
666 Score evaluate_king(const Position& pos, EvalInfo& ei, Value& margin) {
668 const Color Them = (Us == WHITE ? BLACK : WHITE);
670 Bitboard undefended, b, b1, b2, safe;
672 const Square ksq = pos.king_square(Us);
675 Score bonus = ei.pi->king_shelter<Us>(pos, ksq);
677 // King safety. This is quite complicated, and is almost certainly far
678 // from optimally tuned.
679 if ( ei.updateKingTables[Them]
680 && ei.kingAttackersCount[Them] >= 2
681 && ei.kingAdjacentZoneAttacksCount[Them])
683 // Find the attacked squares around the king which has no defenders
684 // apart from the king itself
685 undefended = ei.attackedBy[Them][0] & ei.attackedBy[Us][KING];
686 undefended &= ~( ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
687 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
688 | ei.attackedBy[Us][QUEEN]);
690 // Initialize the 'attackUnits' variable, which is used later on as an
691 // index to the KingDangerTable[] array. The initial value is based on
692 // the number and types of the enemy's attacking pieces, the number of
693 // attacked and undefended squares around our king, the square of the
694 // king, and the quality of the pawn shelter.
695 attackUnits = Min(25, (ei.kingAttackersCount[Them] * ei.kingAttackersWeight[Them]) / 2)
696 + 3 * (ei.kingAdjacentZoneAttacksCount[Them] + count_1s_max_15<HasPopCnt>(undefended))
697 + InitKingDanger[relative_square(Us, ksq)]
698 - mg_value(ei.pi->king_shelter<Us>(pos, ksq)) / 32;
700 // Analyse enemy's safe queen contact checks. First find undefended
701 // squares around the king attacked by enemy queen...
702 b = undefended & ei.attackedBy[Them][QUEEN] & ~pos.pieces_of_color(Them);
705 // ...then remove squares not supported by another enemy piece
706 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
707 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][ROOK]);
709 attackUnits += QueenContactCheckBonus
710 * count_1s_max_15<HasPopCnt>(b)
711 * (Them == pos.side_to_move() ? 2 : 1);
714 // Analyse enemy's safe rook contact checks. First find undefended
715 // squares around the king attacked by enemy rooks...
716 b = undefended & ei.attackedBy[Them][ROOK] & ~pos.pieces_of_color(Them);
718 // Consider only squares where the enemy rook gives check
719 b &= RookPseudoAttacks[ksq];
723 // ...then remove squares not supported by another enemy piece
724 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
725 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][QUEEN]);
727 attackUnits += RookContactCheckBonus
728 * count_1s_max_15<HasPopCnt>(b)
729 * (Them == pos.side_to_move() ? 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 if (pos.side_to_move() == Us)
768 margin += mg_value(KingDangerTable[Us][attackUnits]);
774 // evaluate_passed_pawns<>() evaluates the passed pawns of the given color
777 Score evaluate_passed_pawns(const Position& pos, EvalInfo& ei) {
779 const Color Them = (Us == WHITE ? BLACK : WHITE);
781 Score bonus = SCORE_ZERO;
782 Bitboard squaresToQueen, defendedSquares, unsafeSquares, supportingPawns;
783 Bitboard b = ei.pi->passed_pawns(Us);
789 Square s = pop_1st_bit(&b);
791 assert(pos.pawn_is_passed(Us, s));
793 int r = int(relative_rank(Us, s) - RANK_2);
794 int rr = r * (r - 1);
796 // Base bonus based on rank
797 Value mbonus = Value(20 * rr);
798 Value ebonus = Value(10 * (rr + r + 1));
802 Square blockSq = s + pawn_push(Us);
804 // Adjust bonus based on kings proximity
805 ebonus -= Value(square_distance(pos.king_square(Us), blockSq) * 3 * rr);
806 ebonus -= Value(square_distance(pos.king_square(Us), blockSq + pawn_push(Us)) * rr);
807 ebonus += Value(square_distance(pos.king_square(Them), blockSq) * 6 * rr);
809 // If the pawn is free to advance, increase bonus
810 if (pos.square_is_empty(blockSq))
812 squaresToQueen = squares_in_front_of(Us, s);
813 defendedSquares = squaresToQueen & ei.attackedBy[Us][0];
815 // If there is an enemy rook or queen attacking the pawn from behind,
816 // add all X-ray attacks by the rook or queen. Otherwise consider only
817 // the squares in the pawn's path attacked or occupied by the enemy.
818 if ( (squares_behind(Us, s) & pos.pieces(ROOK, QUEEN, Them))
819 && (squares_behind(Us, s) & pos.pieces(ROOK, QUEEN, Them) & pos.attacks_from<ROOK>(s)))
820 unsafeSquares = squaresToQueen;
822 unsafeSquares = squaresToQueen & (ei.attackedBy[Them][0] | pos.pieces_of_color(Them));
824 // If there aren't enemy attacks or pieces along the path to queen give
825 // huge bonus. Even bigger if we protect the pawn's path.
827 ebonus += Value(rr * (squaresToQueen == defendedSquares ? 17 : 15));
829 // OK, there are enemy attacks or pieces (but not pawns). Are those
830 // squares which are attacked by the enemy also attacked by us ?
831 // If yes, big bonus (but smaller than when there are no enemy attacks),
832 // if no, somewhat smaller bonus.
833 ebonus += Value(rr * ((unsafeSquares & defendedSquares) == unsafeSquares ? 13 : 8));
835 // At last, add a small bonus when there are no *friendly* pieces
836 // in the pawn's path.
837 if (!(squaresToQueen & pos.pieces_of_color(Us)))
842 // Increase the bonus if the passed pawn is supported by a friendly pawn
843 // on the same rank and a bit smaller if it's on the previous rank.
844 supportingPawns = pos.pieces(PAWN, Us) & neighboring_files_bb(s);
845 if (supportingPawns & rank_bb(s))
846 ebonus += Value(r * 20);
847 else if (supportingPawns & rank_bb(s - pawn_push(Us)))
848 ebonus += Value(r * 12);
850 // Rook pawns are a special case: They are sometimes worse, and
851 // sometimes better than other passed pawns. It is difficult to find
852 // good rules for determining whether they are good or bad. For now,
853 // we try the following: Increase the value for rook pawns if the
854 // other side has no pieces apart from a knight, and decrease the
855 // value if the other side has a rook or queen.
856 if (square_file(s) == FILE_A || square_file(s) == FILE_H)
858 if (pos.non_pawn_material(Them) <= KnightValueMidgame)
859 ebonus += ebonus / 4;
860 else if (pos.pieces(ROOK, QUEEN, Them))
861 ebonus -= ebonus / 4;
863 bonus += make_score(mbonus, ebonus);
867 // Add the scores to the middle game and endgame eval
868 return apply_weight(bonus, Weights[PassedPawns]);
872 // evaluate_space() computes the space evaluation for a given side. The
873 // space evaluation is a simple bonus based on the number of safe squares
874 // available for minor pieces on the central four files on ranks 2--4. Safe
875 // squares one, two or three squares behind a friendly pawn are counted
876 // twice. Finally, the space bonus is scaled by a weight taken from the
877 // material hash table. The aim is to improve play on game opening.
878 template<Color Us, bool HasPopCnt>
879 int evaluate_space(const Position& pos, EvalInfo& ei) {
881 const Color Them = (Us == WHITE ? BLACK : WHITE);
883 // Find the safe squares for our pieces inside the area defined by
884 // SpaceMask[]. A square is unsafe if it is attacked by an enemy
885 // pawn, or if it is undefended and attacked by an enemy piece.
886 Bitboard safe = SpaceMask[Us]
887 & ~pos.pieces(PAWN, Us)
888 & ~ei.attackedBy[Them][PAWN]
889 & (ei.attackedBy[Us][0] | ~ei.attackedBy[Them][0]);
891 // Find all squares which are at most three squares behind some friendly pawn
892 Bitboard behind = pos.pieces(PAWN, Us);
893 behind |= (Us == WHITE ? behind >> 8 : behind << 8);
894 behind |= (Us == WHITE ? behind >> 16 : behind << 16);
896 return count_1s_max_15<HasPopCnt>(safe) + count_1s_max_15<HasPopCnt>(behind & safe);
900 // apply_weight() applies an evaluation weight to a value trying to prevent overflow
902 inline Score apply_weight(Score v, Score w) {
903 return make_score((int(mg_value(v)) * mg_value(w)) / 0x100,
904 (int(eg_value(v)) * eg_value(w)) / 0x100);
908 // scale_by_game_phase() interpolates between a middle game and an endgame score,
909 // based on game phase. It also scales the return value by a ScaleFactor array.
911 Value scale_by_game_phase(const Score& v, Phase ph, const ScaleFactor sf[]) {
913 assert(mg_value(v) > -VALUE_INFINITE && mg_value(v) < VALUE_INFINITE);
914 assert(eg_value(v) > -VALUE_INFINITE && eg_value(v) < VALUE_INFINITE);
915 assert(ph >= PHASE_ENDGAME && ph <= PHASE_MIDGAME);
917 Value eg = eg_value(v);
918 ScaleFactor f = sf[eg > VALUE_ZERO ? WHITE : BLACK];
919 Value ev = Value((eg * int(f)) / SCALE_FACTOR_NORMAL);
921 int result = (mg_value(v) * int(ph) + ev * int(128 - ph)) / 128;
922 return Value(result & ~(GrainSize - 1));
926 // weight_option() computes the value of an evaluation weight, by combining
927 // two UCI-configurable weights (midgame and endgame) with an internal weight.
929 Score weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight) {
931 // Scale option value from 100 to 256
932 int mg = get_option_value_int(mgOpt) * 256 / 100;
933 int eg = get_option_value_int(egOpt) * 256 / 100;
935 return apply_weight(make_score(mg, eg), internalWeight);
939 // init_safety() initizes the king safety evaluation, based on UCI
940 // parameters. It is called from read_weights().
944 const Value MaxSlope = Value(30);
945 const Value Peak = Value(1280);
948 // First setup the base table
949 for (int i = 0; i < 100; i++)
951 t[i] = Value(int(0.4 * i * i));
954 t[i] = Min(t[i], t[i - 1] + MaxSlope);
956 t[i] = Min(t[i], Peak);
959 // Then apply the weights and get the final KingDangerTable[] array
960 for (Color c = WHITE; c <= BLACK; c++)
961 for (int i = 0; i < 100; i++)
962 KingDangerTable[c][i] = apply_weight(make_score(t[i], 0), Weights[KingDangerUs + c]);