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 QueenCheckBonus = 3;
204 const int RookCheckBonus = 2;
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_eval_info(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 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);
272 /// evaluate() is the main evaluation function. It always computes two
273 /// values, an endgame score and a middle game score, and interpolates
274 /// between them based on the remaining material.
275 Value evaluate(const Position& pos, Value margins[]) {
277 return CpuHasPOPCNT ? do_evaluate<true>(pos, margins)
278 : do_evaluate<false>(pos, margins);
283 template<bool HasPopCnt>
284 Value do_evaluate(const Position& pos, Value margins[]) {
287 ScaleFactor factor[2];
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 // margins[color] is the uncertainty estimation of position's evaluation
299 // and typically is used by the search for pruning decisions.
300 margins[WHITE] = margins[BLACK] = VALUE_ZERO;
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 // After get_material_info() call that modifies them
312 factor[WHITE] = mi->scale_factor(pos, WHITE);
313 factor[BLACK] = mi->scale_factor(pos, BLACK);
315 // Probe the pawn hash table
316 ei.pi = PawnTable[pos.thread()]->get_pawn_info(pos);
317 bonus += apply_weight(ei.pi->pawns_value(), Weights[PawnStructure]);
319 // Initialize attack and king safety bitboards
320 init_eval_info<WHITE, HasPopCnt>(pos, ei);
321 init_eval_info<BLACK, HasPopCnt>(pos, ei);
323 // Evaluate pieces and mobility
324 bonus += evaluate_pieces_of_color<WHITE, HasPopCnt>(pos, ei, mobilityWhite)
325 - evaluate_pieces_of_color<BLACK, HasPopCnt>(pos, ei, mobilityBlack);
327 bonus += apply_weight(mobilityWhite - mobilityBlack, Weights[Mobility]);
329 // Evaluate kings after all other pieces because we need complete attack
330 // information when computing the king safety evaluation.
331 bonus += evaluate_king<WHITE, HasPopCnt>(pos, ei, margins)
332 - evaluate_king<BLACK, HasPopCnt>(pos, ei, margins);
334 // Evaluate tactical threats, we need full attack information including king
335 bonus += evaluate_threats<WHITE>(pos, ei)
336 - evaluate_threats<BLACK>(pos, ei);
338 // Evaluate passed pawns, we need full attack information including king
339 bonus += evaluate_passed_pawns<WHITE>(pos, ei)
340 - evaluate_passed_pawns<BLACK>(pos, ei);
342 Phase phase = mi->game_phase();
344 // Evaluate space for both sides, only in middle-game.
345 if (phase > PHASE_ENDGAME && mi->space_weight() > 0)
347 int s = evaluate_space<WHITE, HasPopCnt>(pos, ei) - evaluate_space<BLACK, HasPopCnt>(pos, ei);
348 bonus += apply_weight(make_score(s * mi->space_weight(), 0), Weights[Space]);
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 && ( (factor[WHITE] == SCALE_FACTOR_NORMAL && eg_value(bonus) > VALUE_ZERO)
356 || (factor[BLACK] == SCALE_FACTOR_NORMAL && eg_value(bonus) < VALUE_ZERO)))
360 // Only the two bishops ?
361 if ( pos.non_pawn_material(WHITE) == BishopValueMidgame
362 && pos.non_pawn_material(BLACK) == BishopValueMidgame)
364 // Check for KBP vs KB with only a single pawn that is almost
365 // certainly a draw or at least two pawns.
366 bool one_pawn = (pos.piece_count(WHITE, PAWN) + pos.piece_count(BLACK, PAWN) == 1);
367 sf = one_pawn ? ScaleFactor(8) : ScaleFactor(32);
370 // Endgame with opposite-colored bishops, but also other pieces. Still
371 // a bit drawish, but not as drawish as with only the two bishops.
372 sf = ScaleFactor(50);
374 if (factor[WHITE] == SCALE_FACTOR_NORMAL)
376 if (factor[BLACK] == SCALE_FACTOR_NORMAL)
380 // Interpolate between the middle game and the endgame score
381 Value v = scale_by_game_phase(bonus, phase, factor);
382 return pos.side_to_move() == WHITE ? v : -v;
388 /// init_eval() initializes various tables used by the evaluation function
390 void init_eval(int threads) {
392 assert(threads <= MAX_THREADS);
394 for (int i = 0; i < MAX_THREADS; i++)
399 delete MaterialTable[i];
401 MaterialTable[i] = NULL;
405 PawnTable[i] = new PawnInfoTable();
407 if (!MaterialTable[i])
408 MaterialTable[i] = new MaterialInfoTable();
413 /// quit_eval() releases heap-allocated memory at program termination
421 /// read_weights() reads evaluation weights from the corresponding UCI parameters
423 void read_weights(Color us) {
425 // King safety is asymmetrical. Our king danger level is weighted by
426 // "Cowardice" UCI parameter, instead the opponent one by "Aggressiveness".
427 const int kingDangerUs = (us == WHITE ? KingDangerUs : KingDangerThem);
428 const int kingDangerThem = (us == WHITE ? KingDangerThem : KingDangerUs);
430 Weights[Mobility] = weight_option("Mobility (Middle Game)", "Mobility (Endgame)", WeightsInternal[Mobility]);
431 Weights[PawnStructure] = weight_option("Pawn Structure (Middle Game)", "Pawn Structure (Endgame)", WeightsInternal[PawnStructure]);
432 Weights[PassedPawns] = weight_option("Passed Pawns (Middle Game)", "Passed Pawns (Endgame)", WeightsInternal[PassedPawns]);
433 Weights[Space] = weight_option("Space", "Space", WeightsInternal[Space]);
434 Weights[kingDangerUs] = weight_option("Cowardice", "Cowardice", WeightsInternal[KingDangerUs]);
435 Weights[kingDangerThem] = weight_option("Aggressiveness", "Aggressiveness", WeightsInternal[KingDangerThem]);
437 // If running in analysis mode, make sure we use symmetrical king safety. We do this
438 // by replacing both Weights[kingDangerUs] and Weights[kingDangerThem] by their average.
439 if (get_option_value_bool("UCI_AnalyseMode"))
440 Weights[kingDangerUs] = Weights[kingDangerThem] = (Weights[kingDangerUs] + Weights[kingDangerThem]) / 2;
448 // init_eval_info() initializes king bitboards for given color adding
449 // pawn attacks. To be done at the beginning of the evaluation.
451 template<Color Us, bool HasPopCnt>
452 void init_eval_info(const Position& pos, EvalInfo& ei) {
454 const Color Them = (Us == WHITE ? BLACK : WHITE);
456 Bitboard b = ei.attackedBy[Them][KING] = pos.attacks_from<KING>(pos.king_square(Them));
457 ei.kingZone[Us] = (b | (Us == WHITE ? b >> 8 : b << 8));
458 ei.attackedBy[Us][PAWN] = ei.pi->pawn_attacks(Us);
459 ei.updateKingTables[Us] = pos.piece_count(Us, QUEEN) && pos.non_pawn_material(Us) >= QueenValueMidgame + RookValueMidgame;
460 if (ei.updateKingTables[Us])
462 b &= ei.attackedBy[Us][PAWN];
463 ei.kingAttackersCount[Us] = b ? count_1s_max_15<HasPopCnt>(b) / 2 : EmptyBoardBB;
464 ei.kingAdjacentZoneAttacksCount[Us] = ei.kingAttackersWeight[Us] = EmptyBoardBB;
469 // evaluate_outposts() evaluates bishop and knight outposts squares
471 template<PieceType Piece, Color Us>
472 Score evaluate_outposts(const Position& pos, EvalInfo& ei, Square s) {
474 const Color Them = (Us == WHITE ? BLACK : WHITE);
476 assert (Piece == BISHOP || Piece == KNIGHT);
478 // Initial bonus based on square
479 Value bonus = OutpostBonus[Piece == BISHOP][relative_square(Us, s)];
481 // Increase bonus if supported by pawn, especially if the opponent has
482 // no minor piece which can exchange the outpost piece.
483 if (bonus && bit_is_set(ei.attackedBy[Us][PAWN], s))
485 if ( pos.pieces(KNIGHT, Them) == EmptyBoardBB
486 && (SquaresByColorBB[square_color(s)] & pos.pieces(BISHOP, Them)) == EmptyBoardBB)
487 bonus += bonus + bonus / 2;
491 return make_score(bonus, bonus);
495 // evaluate_pieces<>() assigns bonuses and penalties to the pieces of a given color
497 template<PieceType Piece, Color Us, bool HasPopCnt>
498 Score evaluate_pieces(const Position& pos, EvalInfo& ei, Score& mobility, Bitboard no_mob_area) {
504 Score bonus = SCORE_ZERO;
506 const Color Them = (Us == WHITE ? BLACK : WHITE);
507 const Square* ptr = pos.piece_list_begin(Us, Piece);
509 ei.attackedBy[Us][Piece] = EmptyBoardBB;
511 while ((s = *ptr++) != SQ_NONE)
513 // Find attacked squares, including x-ray attacks for bishops and rooks
514 if (Piece == KNIGHT || Piece == QUEEN)
515 b = pos.attacks_from<Piece>(s);
516 else if (Piece == BISHOP)
517 b = bishop_attacks_bb(s, pos.occupied_squares() & ~pos.pieces(QUEEN, Us));
518 else if (Piece == ROOK)
519 b = rook_attacks_bb(s, pos.occupied_squares() & ~pos.pieces(ROOK, QUEEN, Us));
523 // Update attack info
524 ei.attackedBy[Us][Piece] |= b;
527 if (ei.updateKingTables[Us] && (b & ei.kingZone[Us]))
529 ei.kingAttackersCount[Us]++;
530 ei.kingAttackersWeight[Us] += KingAttackWeights[Piece];
531 Bitboard bb = (b & ei.attackedBy[Them][KING]);
533 ei.kingAdjacentZoneAttacksCount[Us] += count_1s_max_15<HasPopCnt>(bb);
537 mob = (Piece != QUEEN ? count_1s_max_15<HasPopCnt>(b & no_mob_area)
538 : count_1s<HasPopCnt>(b & no_mob_area));
540 mobility += MobilityBonus[Piece][mob];
542 // Decrease score if we are attacked by an enemy pawn. Remaining part
543 // of threat evaluation must be done later when we have full attack info.
544 if (bit_is_set(ei.attackedBy[Them][PAWN], s))
545 bonus -= ThreatedByPawnPenalty[Piece];
547 // Bishop and knight outposts squares
548 if ((Piece == BISHOP || Piece == KNIGHT) && pos.square_is_weak(s, Us))
549 bonus += evaluate_outposts<Piece, Us>(pos, ei, s);
551 // Queen or rook on 7th rank
552 if ( (Piece == ROOK || Piece == QUEEN)
553 && relative_rank(Us, s) == RANK_7
554 && relative_rank(Us, pos.king_square(Them)) == RANK_8)
556 bonus += (Piece == ROOK ? RookOn7thBonus : QueenOn7thBonus);
559 // Special extra evaluation for rooks
562 // Open and half-open files
564 if (ei.pi->file_is_half_open(Us, f))
566 if (ei.pi->file_is_half_open(Them, f))
567 bonus += RookOpenFileBonus;
569 bonus += RookHalfOpenFileBonus;
572 // Penalize rooks which are trapped inside a king. Penalize more if
573 // king has lost right to castle.
574 if (mob > 6 || ei.pi->file_is_half_open(Us, f))
577 ksq = pos.king_square(Us);
579 if ( square_file(ksq) >= FILE_E
580 && square_file(s) > square_file(ksq)
581 && (relative_rank(Us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
583 // Is there a half-open file between the king and the edge of the board?
584 if (!ei.pi->has_open_file_to_right(Us, square_file(ksq)))
585 bonus -= make_score(pos.can_castle(Us) ? (TrappedRookPenalty - mob * 16) / 2
586 : (TrappedRookPenalty - mob * 16), 0);
588 else if ( square_file(ksq) <= FILE_D
589 && square_file(s) < square_file(ksq)
590 && (relative_rank(Us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
592 // Is there a half-open file between the king and the edge of the board?
593 if (!ei.pi->has_open_file_to_left(Us, square_file(ksq)))
594 bonus -= make_score(pos.can_castle(Us) ? (TrappedRookPenalty - mob * 16) / 2
595 : (TrappedRookPenalty - mob * 16), 0);
603 // evaluate_threats<>() assigns bonuses according to the type of attacking piece
604 // and the type of attacked one.
607 Score evaluate_threats(const Position& pos, EvalInfo& ei) {
609 const Color Them = (Us == WHITE ? BLACK : WHITE);
612 Score bonus = SCORE_ZERO;
614 // Enemy pieces not defended by a pawn and under our attack
615 Bitboard weakEnemies = pos.pieces_of_color(Them)
616 & ~ei.attackedBy[Them][PAWN]
617 & ei.attackedBy[Us][0];
621 // Add bonus according to type of attacked enemy piece and to the
622 // type of attacking piece, from knights to queens. Kings are not
623 // considered because are already handled in king evaluation.
624 for (PieceType pt1 = KNIGHT; pt1 < KING; pt1++)
626 b = ei.attackedBy[Us][pt1] & weakEnemies;
628 for (PieceType pt2 = PAWN; pt2 < KING; pt2++)
629 if (b & pos.pieces(pt2))
630 bonus += ThreatBonus[pt1][pt2];
636 // evaluate_pieces_of_color<>() assigns bonuses and penalties to all the
637 // pieces of a given color.
639 template<Color Us, bool HasPopCnt>
640 Score evaluate_pieces_of_color(const Position& pos, EvalInfo& ei, Score& mobility) {
642 const Color Them = (Us == WHITE ? BLACK : WHITE);
644 Score bonus = mobility = SCORE_ZERO;
646 // Do not include in mobility squares protected by enemy pawns or occupied by our pieces
647 const Bitboard no_mob_area = ~(ei.attackedBy[Them][PAWN] | pos.pieces_of_color(Us));
649 bonus += evaluate_pieces<KNIGHT, Us, HasPopCnt>(pos, ei, mobility, no_mob_area);
650 bonus += evaluate_pieces<BISHOP, Us, HasPopCnt>(pos, ei, mobility, no_mob_area);
651 bonus += evaluate_pieces<ROOK, Us, HasPopCnt>(pos, ei, mobility, no_mob_area);
652 bonus += evaluate_pieces<QUEEN, Us, HasPopCnt>(pos, ei, mobility, no_mob_area);
654 // Sum up all attacked squares
655 ei.attackedBy[Us][0] = ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
656 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
657 | ei.attackedBy[Us][QUEEN] | ei.attackedBy[Us][KING];
662 // evaluate_king<>() assigns bonuses and penalties to a king of a given color
664 template<Color Us, bool HasPopCnt>
665 Score evaluate_king(const Position& pos, EvalInfo& ei, Value margins[]) {
667 const Color Them = (Us == WHITE ? BLACK : WHITE);
669 Bitboard undefended, b, b1, b2, safe;
671 const Square ksq = pos.king_square(Us);
674 Score bonus = ei.pi->king_shelter<Us>(pos, ksq);
676 // King safety. This is quite complicated, and is almost certainly far
677 // from optimally tuned.
678 if ( ei.updateKingTables[Them]
679 && ei.kingAttackersCount[Them] >= 2
680 && ei.kingAdjacentZoneAttacksCount[Them])
682 // Find the attacked squares around the king which has no defenders
683 // apart from the king itself
684 undefended = ei.attackedBy[Them][0] & ei.attackedBy[Us][KING];
685 undefended &= ~( ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
686 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
687 | ei.attackedBy[Us][QUEEN]);
689 // Initialize the 'attackUnits' variable, which is used later on as an
690 // index to the KingDangerTable[] array. The initial value is based on
691 // the number and types of the enemy's attacking pieces, the number of
692 // attacked and undefended squares around our king, the square of the
693 // king, and the quality of the pawn shelter.
694 attackUnits = Min(25, (ei.kingAttackersCount[Them] * ei.kingAttackersWeight[Them]) / 2)
695 + 3 * (ei.kingAdjacentZoneAttacksCount[Them] + count_1s_max_15<HasPopCnt>(undefended))
696 + InitKingDanger[relative_square(Us, ksq)]
697 - mg_value(ei.pi->king_shelter<Us>(pos, ksq)) / 32;
699 // Analyse enemy's safe queen contact checks. First find undefended
700 // squares around the king attacked by enemy queen...
701 b = undefended & ei.attackedBy[Them][QUEEN] & ~pos.pieces_of_color(Them);
704 // ...then remove squares not supported by another enemy piece
705 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
706 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][ROOK]);
708 attackUnits += QueenContactCheckBonus
709 * count_1s_max_15<HasPopCnt>(b)
710 * (Them == pos.side_to_move() ? 2 : 1);
713 // Analyse enemy's safe distance checks for sliders and knights
714 safe = ~(pos.pieces_of_color(Them) | ei.attackedBy[Us][0]);
716 b1 = pos.attacks_from<ROOK>(ksq) & safe;
717 b2 = pos.attacks_from<BISHOP>(ksq) & safe;
719 // Enemy queen safe checks
720 b = (b1 | b2) & ei.attackedBy[Them][QUEEN];
722 attackUnits += QueenCheckBonus * count_1s_max_15<HasPopCnt>(b);
724 // Enemy rooks safe checks
725 b = b1 & ei.attackedBy[Them][ROOK];
727 attackUnits += RookCheckBonus * count_1s_max_15<HasPopCnt>(b);
729 // Enemy bishops safe checks
730 b = b2 & ei.attackedBy[Them][BISHOP];
732 attackUnits += BishopCheckBonus * count_1s_max_15<HasPopCnt>(b);
734 // Enemy knights safe checks
735 b = pos.attacks_from<KNIGHT>(ksq) & ei.attackedBy[Them][KNIGHT] & safe;
737 attackUnits += KnightCheckBonus * count_1s_max_15<HasPopCnt>(b);
739 // To index KingDangerTable[] attackUnits must be in [0, 99] range
740 attackUnits = Min(99, Max(0, attackUnits));
742 // Finally, extract the king danger score from the KingDangerTable[]
743 // array and subtract the score from evaluation. Set also margins[]
744 // value that will be used for pruning because this value can sometimes
745 // be very big, and so capturing a single attacking piece can therefore
746 // result in a score change far bigger than the value of the captured piece.
747 bonus -= KingDangerTable[Us][attackUnits];
748 margins[Us] += mg_value(KingDangerTable[Us][attackUnits]);
754 // evaluate_passed_pawns<>() evaluates the passed pawns of the given color
757 Score evaluate_passed_pawns(const Position& pos, EvalInfo& ei) {
759 const Color Them = (Us == WHITE ? BLACK : WHITE);
761 Score bonus = SCORE_ZERO;
762 Bitboard squaresToQueen, defendedSquares, unsafeSquares, supportingPawns;
763 Bitboard b = ei.pi->passed_pawns(Us);
769 Square s = pop_1st_bit(&b);
771 assert(pos.pawn_is_passed(Us, s));
773 int r = int(relative_rank(Us, s) - RANK_2);
774 int rr = r * (r - 1);
776 // Base bonus based on rank
777 Value mbonus = Value(20 * rr);
778 Value ebonus = Value(10 * (rr + r + 1));
782 Square blockSq = s + pawn_push(Us);
784 // Adjust bonus based on kings proximity
785 ebonus -= Value(square_distance(pos.king_square(Us), blockSq) * 3 * rr);
786 ebonus -= Value(square_distance(pos.king_square(Us), blockSq + pawn_push(Us)) * rr);
787 ebonus += Value(square_distance(pos.king_square(Them), blockSq) * 6 * rr);
789 // If the pawn is free to advance, increase bonus
790 if (pos.square_is_empty(blockSq))
792 squaresToQueen = squares_in_front_of(Us, s);
793 defendedSquares = squaresToQueen & ei.attackedBy[Us][0];
795 // If there is an enemy rook or queen attacking the pawn from behind,
796 // add all X-ray attacks by the rook or queen. Otherwise consider only
797 // the squares in the pawn's path attacked or occupied by the enemy.
798 if ( (squares_behind(Us, s) & pos.pieces(ROOK, QUEEN, Them))
799 && (squares_behind(Us, s) & pos.pieces(ROOK, QUEEN, Them) & pos.attacks_from<ROOK>(s)))
800 unsafeSquares = squaresToQueen;
802 unsafeSquares = squaresToQueen & (ei.attackedBy[Them][0] | pos.pieces_of_color(Them));
804 // If there aren't enemy attacks or pieces along the path to queen give
805 // huge bonus. Even bigger if we protect the pawn's path.
807 ebonus += Value(rr * (squaresToQueen == defendedSquares ? 17 : 15));
809 // OK, there are enemy attacks or pieces (but not pawns). Are those
810 // squares which are attacked by the enemy also attacked by us ?
811 // If yes, big bonus (but smaller than when there are no enemy attacks),
812 // if no, somewhat smaller bonus.
813 ebonus += Value(rr * ((unsafeSquares & defendedSquares) == unsafeSquares ? 13 : 8));
815 // At last, add a small bonus when there are no *friendly* pieces
816 // in the pawn's path.
817 if (!(squaresToQueen & pos.pieces_of_color(Us)))
822 // Increase the bonus if the passed pawn is supported by a friendly pawn
823 // on the same rank and a bit smaller if it's on the previous rank.
824 supportingPawns = pos.pieces(PAWN, Us) & neighboring_files_bb(s);
825 if (supportingPawns & rank_bb(s))
826 ebonus += Value(r * 20);
827 else if (supportingPawns & rank_bb(s - pawn_push(Us)))
828 ebonus += Value(r * 12);
830 // Rook pawns are a special case: They are sometimes worse, and
831 // sometimes better than other passed pawns. It is difficult to find
832 // good rules for determining whether they are good or bad. For now,
833 // we try the following: Increase the value for rook pawns if the
834 // other side has no pieces apart from a knight, and decrease the
835 // value if the other side has a rook or queen.
836 if (square_file(s) == FILE_A || square_file(s) == FILE_H)
838 if (pos.non_pawn_material(Them) <= KnightValueMidgame)
839 ebonus += ebonus / 4;
840 else if (pos.pieces(ROOK, QUEEN, Them))
841 ebonus -= ebonus / 4;
843 bonus += make_score(mbonus, ebonus);
847 // Add the scores to the middle game and endgame eval
848 return apply_weight(bonus, Weights[PassedPawns]);
852 // evaluate_space() computes the space evaluation for a given side. The
853 // space evaluation is a simple bonus based on the number of safe squares
854 // available for minor pieces on the central four files on ranks 2--4. Safe
855 // squares one, two or three squares behind a friendly pawn are counted
856 // twice. Finally, the space bonus is scaled by a weight taken from the
857 // material hash table. The aim is to improve play on game opening.
858 template<Color Us, bool HasPopCnt>
859 int evaluate_space(const Position& pos, EvalInfo& ei) {
861 const Color Them = (Us == WHITE ? BLACK : WHITE);
863 // Find the safe squares for our pieces inside the area defined by
864 // SpaceMask[]. A square is unsafe if it is attacked by an enemy
865 // pawn, or if it is undefended and attacked by an enemy piece.
866 Bitboard safe = SpaceMask[Us]
867 & ~pos.pieces(PAWN, Us)
868 & ~ei.attackedBy[Them][PAWN]
869 & (ei.attackedBy[Us][0] | ~ei.attackedBy[Them][0]);
871 // Find all squares which are at most three squares behind some friendly pawn
872 Bitboard behind = pos.pieces(PAWN, Us);
873 behind |= (Us == WHITE ? behind >> 8 : behind << 8);
874 behind |= (Us == WHITE ? behind >> 16 : behind << 16);
876 return count_1s_max_15<HasPopCnt>(safe) + count_1s_max_15<HasPopCnt>(behind & safe);
880 // apply_weight() applies an evaluation weight to a value trying to prevent overflow
882 inline Score apply_weight(Score v, Score w) {
883 return make_score((int(mg_value(v)) * mg_value(w)) / 0x100,
884 (int(eg_value(v)) * eg_value(w)) / 0x100);
888 // scale_by_game_phase() interpolates between a middle game and an endgame score,
889 // based on game phase. It also scales the return value by a ScaleFactor array.
891 Value scale_by_game_phase(const Score& v, Phase ph, const ScaleFactor sf[]) {
893 assert(mg_value(v) > -VALUE_INFINITE && mg_value(v) < VALUE_INFINITE);
894 assert(eg_value(v) > -VALUE_INFINITE && eg_value(v) < VALUE_INFINITE);
895 assert(ph >= PHASE_ENDGAME && ph <= PHASE_MIDGAME);
897 Value eg = eg_value(v);
898 ScaleFactor f = sf[eg > VALUE_ZERO ? WHITE : BLACK];
899 Value ev = Value((eg * int(f)) / SCALE_FACTOR_NORMAL);
901 int result = (mg_value(v) * int(ph) + ev * int(128 - ph)) / 128;
902 return Value(result & ~(GrainSize - 1));
906 // weight_option() computes the value of an evaluation weight, by combining
907 // two UCI-configurable weights (midgame and endgame) with an internal weight.
909 Score weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight) {
911 // Scale option value from 100 to 256
912 int mg = get_option_value_int(mgOpt) * 256 / 100;
913 int eg = get_option_value_int(egOpt) * 256 / 100;
915 return apply_weight(make_score(mg, eg), internalWeight);
919 // init_safety() initizes the king safety evaluation, based on UCI
920 // parameters. It is called from read_weights().
924 const Value MaxSlope = Value(30);
925 const Value Peak = Value(1280);
928 // First setup the base table
929 for (int i = 0; i < 100; i++)
931 t[i] = Value(int(0.4 * i * i));
934 t[i] = Min(t[i], t[i - 1] + MaxSlope);
936 t[i] = Min(t[i], Peak);
939 // Then apply the weights and get the final KingDangerTable[] array
940 for (Color c = WHITE; c <= BLACK; c++)
941 for (int i = 0; i < 100; i++)
942 KingDangerTable[c][i] = apply_weight(make_score(t[i], 0), Weights[KingDangerUs + c]);