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/>.
34 #include "ucioption.h"
38 //// Local definitions
43 const int Sign[2] = { 1, -1 };
45 // Evaluation grain size, must be a power of 2
46 const int GrainSize = 8;
48 // Evaluation weights, initialized from UCI options
49 enum { Mobility, PawnStructure, PassedPawns, Space, KingDangerUs, KingDangerThem };
53 #define S(mg, eg) make_score(mg, eg)
55 // Internal evaluation weights. These are applied on top of the evaluation
56 // weights read from UCI parameters. The purpose is to be able to change
57 // the evaluation weights while keeping the default values of the UCI
58 // parameters at 100, which looks prettier.
60 // Values modified by Joona Kiiski
61 const Score WeightsInternal[] = {
62 S(248, 271), S(233, 201), S(252, 259), S(46, 0), S(247, 0), S(259, 0)
65 // Knight mobility bonus in middle game and endgame, indexed by the number
66 // of attacked squares not occupied by friendly piecess.
67 const Score KnightMobilityBonus[16] = {
68 S(-38,-33), S(-25,-23), S(-12,-13), S( 0,-3),
69 S( 12, 7), S( 25, 17), S( 31, 22), S(38, 27), S(38, 27)
72 // Bishop mobility bonus in middle game and endgame, indexed by the number
73 // of attacked squares not occupied by friendly pieces. X-ray attacks through
74 // queens are also included.
75 const Score BishopMobilityBonus[16] = {
76 S(-25,-30), S(-11,-16), S( 3, -2), S(17, 12),
77 S( 31, 26), S( 45, 40), S(57, 52), S(65, 60),
78 S( 71, 65), S( 74, 69), S(76, 71), S(78, 73),
79 S( 79, 74), S( 80, 75), S(81, 76), S(81, 76)
82 // Rook mobility bonus in middle game and endgame, indexed by the number
83 // of attacked squares not occupied by friendly pieces. X-ray attacks through
84 // queens and rooks are also included.
85 const Score RookMobilityBonus[16] = {
86 S(-20,-36), S(-14,-19), S(-8, -3), S(-2, 13),
87 S( 4, 29), S( 10, 46), S(14, 62), S(19, 79),
88 S( 23, 95), S( 26,106), S(27,111), S(28,114),
89 S( 29,116), S( 30,117), S(31,118), S(32,118)
92 // Queen mobility bonus in middle game and endgame, indexed by the number
93 // of attacked squares not occupied by friendly pieces.
94 const Score QueenMobilityBonus[32] = {
95 S(-10,-18), S(-8,-13), S(-6, -7), S(-3, -2), S(-1, 3), S( 1, 8),
96 S( 3, 13), S( 5, 19), S( 8, 23), S(10, 27), S(12, 32), S(15, 34),
97 S( 16, 35), S(17, 35), S(18, 35), S(20, 35), S(20, 35), S(20, 35),
98 S( 20, 35), S(20, 35), S(20, 35), S(20, 35), S(20, 35), S(20, 35),
99 S( 20, 35), S(20, 35), S(20, 35), S(20, 35), S(20, 35), S(20, 35),
100 S( 20, 35), S(20, 35)
103 // Pointers table to access mobility tables through piece type
104 const Score* MobilityBonus[8] = { 0, 0, KnightMobilityBonus, BishopMobilityBonus,
105 RookMobilityBonus, QueenMobilityBonus, 0, 0 };
107 // Outpost bonuses for knights and bishops, indexed by square (from white's
109 const Value KnightOutpostBonus[64] = {
111 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 1
112 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 2
113 V(0), V(0), V(4), V(8), V(8), V(4), V(0), V(0), // 3
114 V(0), V(4),V(17),V(26),V(26),V(17), V(4), V(0), // 4
115 V(0), V(8),V(26),V(35),V(35),V(26), V(8), V(0), // 5
116 V(0), V(4),V(17),V(17),V(17),V(17), V(4), V(0), // 6
117 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 7
118 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0) // 8
121 const Value BishopOutpostBonus[64] = {
123 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 1
124 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 2
125 V(0), V(0), V(5), V(5), V(5), V(5), V(0), V(0), // 3
126 V(0), V(5),V(10),V(10),V(10),V(10), V(5), V(0), // 4
127 V(0),V(10),V(21),V(21),V(21),V(21),V(10), V(0), // 5
128 V(0), V(5), V(8), V(8), V(8), V(8), V(5), V(0), // 6
129 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 7
130 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0) // 8
133 // ThreatBonus[attacking][attacked] contains bonus according to which
134 // piece type attacks which one.
135 const Score ThreatBonus[8][8] = {
137 { S(0, 0), S( 7, 39), S( 0, 0), S(24, 49), S(41,100), S(41,100) }, // KNIGHT
138 { S(0, 0), S( 7, 39), S(24, 49), S( 0, 0), S(41,100), S(41,100) }, // BISHOP
139 { S(0, 0), S(-1, 29), S(15, 49), S(15, 49), S( 0, 0), S(24, 49) }, // ROOK
140 { S(0, 0), S(15, 39), S(15, 39), S(15, 39), S(15, 39), S( 0, 0) } // QUEEN
143 // ThreatedByPawnPenalty[] contains a penalty according to which piece
144 // type is attacked by an enemy pawn.
145 const Score ThreatedByPawnPenalty[8] = {
146 S(0, 0), S(0, 0), S(56, 70), S(56, 70), S(76, 99), S(86, 118)
151 // Bonus for unstoppable passed pawns
152 const Value UnstoppablePawnValue = Value(0x500);
154 // Rooks and queens on the 7th rank (modified by Joona Kiiski)
155 const Score RookOn7thBonus = make_score(47, 98);
156 const Score QueenOn7thBonus = make_score(27, 54);
158 // Rooks on open files (modified by Joona Kiiski)
159 const Score RookOpenFileBonus = make_score(43, 43);
160 const Score RookHalfOpenFileBonus = make_score(19, 19);
162 // Penalty for rooks trapped inside a friendly king which has lost the
164 const Value TrappedRookPenalty = Value(180);
166 // Penalty for a bishop on a7/h7 (a2/h2 for black) which is trapped by
168 const Score TrappedBishopA7H7Penalty = make_score(300, 300);
170 // Bitboard masks for detecting trapped bishops on a7/h7 (a2/h2 for black)
171 const Bitboard MaskA7H7[2] = {
172 ((1ULL << SQ_A7) | (1ULL << SQ_H7)),
173 ((1ULL << SQ_A2) | (1ULL << SQ_H2))
176 // Penalty for a bishop on a1/h1 (a8/h8 for black) which is trapped by
177 // a friendly pawn on b2/g2 (b7/g7 for black). This can obviously only
178 // happen in Chess960 games.
179 const Score TrappedBishopA1H1Penalty = make_score(100, 100);
181 // Bitboard masks for detecting trapped bishops on a1/h1 (a8/h8 for black)
182 const Bitboard MaskA1H1[2] = {
183 ((1ULL << SQ_A1) | (1ULL << SQ_H1)),
184 ((1ULL << SQ_A8) | (1ULL << SQ_H8))
187 // The SpaceMask[color] contains the area of the board which is considered
188 // by the space evaluation. In the middle game, each side is given a bonus
189 // based on how many squares inside this area are safe and available for
190 // friendly minor pieces.
191 const Bitboard SpaceMask[2] = {
192 (1ULL<<SQ_C2) | (1ULL<<SQ_D2) | (1ULL<<SQ_E2) | (1ULL<<SQ_F2) |
193 (1ULL<<SQ_C3) | (1ULL<<SQ_D3) | (1ULL<<SQ_E3) | (1ULL<<SQ_F3) |
194 (1ULL<<SQ_C4) | (1ULL<<SQ_D4) | (1ULL<<SQ_E4) | (1ULL<<SQ_F4),
195 (1ULL<<SQ_C7) | (1ULL<<SQ_D7) | (1ULL<<SQ_E7) | (1ULL<<SQ_F7) |
196 (1ULL<<SQ_C6) | (1ULL<<SQ_D6) | (1ULL<<SQ_E6) | (1ULL<<SQ_F6) |
197 (1ULL<<SQ_C5) | (1ULL<<SQ_D5) | (1ULL<<SQ_E5) | (1ULL<<SQ_F5)
200 /// King danger constants and variables. The king danger scores are taken
201 /// from the KingDangerTable[]. Various little "meta-bonuses" measuring
202 /// the strength of the enemy attack are added up into an integer, which
203 /// is used as an index to KingDangerTable[].
205 // KingAttackWeights[] contains king attack weights by piece type
206 const int KingAttackWeights[8] = { 0, 0, 2, 2, 3, 5 };
208 // Bonuses for enemy's safe checks
209 const int QueenContactCheckBonus = 3;
210 const int DiscoveredCheckBonus = 3;
211 const int QueenCheckBonus = 2;
212 const int RookCheckBonus = 1;
213 const int BishopCheckBonus = 1;
214 const int KnightCheckBonus = 1;
216 // InitKingDanger[] contains bonuses based on the position of the defending
218 const int InitKingDanger[64] = {
219 2, 0, 2, 5, 5, 2, 0, 2,
220 2, 2, 4, 8, 8, 4, 2, 2,
221 7, 10, 12, 12, 12, 12, 10, 7,
222 15, 15, 15, 15, 15, 15, 15, 15,
223 15, 15, 15, 15, 15, 15, 15, 15,
224 15, 15, 15, 15, 15, 15, 15, 15,
225 15, 15, 15, 15, 15, 15, 15, 15,
226 15, 15, 15, 15, 15, 15, 15, 15
229 // KingDangerTable[color][] contains the actual king danger weighted scores
230 Score KingDangerTable[2][128];
232 // Pawn and material hash tables, indexed by the current thread id.
233 // Note that they will be initialized at 0 being global variables.
234 MaterialInfoTable* MaterialTable[MAX_THREADS];
235 PawnInfoTable* PawnTable[MAX_THREADS];
237 // Sizes of pawn and material hash tables
238 const int PawnTableSize = 16384;
239 const int MaterialTableSize = 1024;
241 // Function prototypes
242 template<bool HasPopCnt>
243 Value do_evaluate(const Position& pos, EvalInfo& ei);
245 template<Color Us, bool HasPopCnt>
246 void init_attack_tables(const Position& pos, EvalInfo& ei);
248 template<Color Us, bool HasPopCnt>
249 void evaluate_pieces_of_color(const Position& pos, EvalInfo& ei);
251 template<Color Us, bool HasPopCnt>
252 void evaluate_king(const Position& pos, EvalInfo& ei);
255 void evaluate_threats(const Position& pos, EvalInfo& ei);
257 template<Color Us, bool HasPopCnt>
258 void evaluate_space(const Position& pos, EvalInfo& ei);
261 void evaluate_passed_pawns(const Position& pos, EvalInfo& ei);
263 void evaluate_unstoppable_pawns(const Position& pos, EvalInfo& ei);
264 void evaluate_trapped_bishop_a7h7(const Position& pos, Square s, Color us, EvalInfo& ei);
265 void evaluate_trapped_bishop_a1h1(const Position& pos, Square s, Color us, EvalInfo& ei);
266 inline Score apply_weight(Score v, Score weight);
267 Value scale_by_game_phase(const Score& v, Phase ph, const ScaleFactor sf[]);
268 Score weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight);
277 /// evaluate() is the main evaluation function. It always computes two
278 /// values, an endgame score and a middle game score, and interpolates
279 /// between them based on the remaining material.
280 Value evaluate(const Position& pos, EvalInfo& ei) {
282 return CpuHasPOPCNT ? do_evaluate<true>(pos, ei)
283 : do_evaluate<false>(pos, ei);
288 template<bool HasPopCnt>
289 Value do_evaluate(const Position& pos, EvalInfo& ei) {
291 ScaleFactor factor[2];
294 assert(pos.thread() >= 0 && pos.thread() < MAX_THREADS);
295 assert(!pos.is_check());
297 memset(&ei, 0, sizeof(EvalInfo));
299 // Initialize by reading the incrementally updated scores included in the
300 // position object (material + piece square tables)
301 ei.value = pos.value();
303 // Probe the material hash table
304 ei.mi = MaterialTable[pos.thread()]->get_material_info(pos);
305 ei.value += ei.mi->material_value();
307 // If we have a specialized evaluation function for the current material
308 // configuration, call it and return
309 if (ei.mi->specialized_eval_exists())
310 return ei.mi->evaluate(pos);
312 // After get_material_info() call that modifies them
313 factor[WHITE] = ei.mi->scale_factor(pos, WHITE);
314 factor[BLACK] = ei.mi->scale_factor(pos, BLACK);
316 // Probe the pawn hash table
317 ei.pi = PawnTable[pos.thread()]->get_pawn_info(pos);
318 ei.value += apply_weight(ei.pi->pawns_value(), Weights[PawnStructure]);
320 // Initialize attack bitboards with pawns evaluation
321 init_attack_tables<WHITE, HasPopCnt>(pos, ei);
322 init_attack_tables<BLACK, HasPopCnt>(pos, ei);
325 evaluate_pieces_of_color<WHITE, HasPopCnt>(pos, ei);
326 evaluate_pieces_of_color<BLACK, HasPopCnt>(pos, ei);
328 // Kings. Kings are evaluated after all other pieces for both sides,
329 // because we need complete attack information for all pieces when computing
330 // the king safety evaluation.
331 evaluate_king<WHITE, HasPopCnt>(pos, ei);
332 evaluate_king<BLACK, HasPopCnt>(pos, ei);
334 // Evaluate tactical threats, we need full attack info including king
335 evaluate_threats<WHITE>(pos, ei);
336 evaluate_threats<BLACK>(pos, ei);
338 // Evaluate passed pawns, we need full attack info including king
339 evaluate_passed_pawns<WHITE>(pos, ei);
340 evaluate_passed_pawns<BLACK>(pos, ei);
342 // If one side has only a king, check whether exsists any unstoppable passed pawn
343 if (!pos.non_pawn_material(WHITE) || !pos.non_pawn_material(BLACK))
344 evaluate_unstoppable_pawns(pos, ei);
346 Phase phase = ei.mi->game_phase();
348 // Middle-game specific evaluation terms
349 if (phase > PHASE_ENDGAME)
351 // Pawn storms in positions with opposite castling
352 if ( square_file(pos.king_square(WHITE)) >= FILE_E
353 && square_file(pos.king_square(BLACK)) <= FILE_D)
355 ei.value += make_score(ei.pi->queenside_storm_value(WHITE) - ei.pi->kingside_storm_value(BLACK), 0);
357 else if ( square_file(pos.king_square(WHITE)) <= FILE_D
358 && square_file(pos.king_square(BLACK)) >= FILE_E)
360 ei.value += make_score(ei.pi->kingside_storm_value(WHITE) - ei.pi->queenside_storm_value(BLACK), 0);
362 // Evaluate space for both sides
363 if (ei.mi->space_weight() > 0)
365 evaluate_space<WHITE, HasPopCnt>(pos, ei);
366 evaluate_space<BLACK, HasPopCnt>(pos, ei);
371 ei.value += apply_weight(ei.mobility, Weights[Mobility]);
373 // If we don't already have an unusual scale factor, check for opposite
374 // colored bishop endgames, and use a lower scale for those
375 if ( phase < PHASE_MIDGAME
376 && pos.opposite_colored_bishops()
377 && ( (factor[WHITE] == SCALE_FACTOR_NORMAL && eg_value(ei.value) > Value(0))
378 || (factor[BLACK] == SCALE_FACTOR_NORMAL && eg_value(ei.value) < Value(0))))
382 // Only the two bishops ?
383 if ( pos.non_pawn_material(WHITE) == BishopValueMidgame
384 && pos.non_pawn_material(BLACK) == BishopValueMidgame)
386 // Check for KBP vs KB with only a single pawn that is almost
387 // certainly a draw or at least two pawns.
388 bool one_pawn = (pos.piece_count(WHITE, PAWN) + pos.piece_count(BLACK, PAWN) == 1);
389 sf = one_pawn ? ScaleFactor(8) : ScaleFactor(32);
392 // Endgame with opposite-colored bishops, but also other pieces. Still
393 // a bit drawish, but not as drawish as with only the two bishops.
394 sf = ScaleFactor(50);
396 if (factor[WHITE] == SCALE_FACTOR_NORMAL)
398 if (factor[BLACK] == SCALE_FACTOR_NORMAL)
402 // Interpolate between the middle game and the endgame score
403 return Sign[pos.side_to_move()] * scale_by_game_phase(ei.value, phase, factor);
408 /// init_eval() initializes various tables used by the evaluation function
410 void init_eval(int threads) {
412 assert(threads <= MAX_THREADS);
414 for (int i = 0; i < MAX_THREADS; i++)
419 delete MaterialTable[i];
421 MaterialTable[i] = NULL;
425 PawnTable[i] = new PawnInfoTable(PawnTableSize);
426 if (!MaterialTable[i])
427 MaterialTable[i] = new MaterialInfoTable(MaterialTableSize);
432 /// quit_eval() releases heap-allocated memory at program termination
436 for (int i = 0; i < MAX_THREADS; i++)
439 delete MaterialTable[i];
441 MaterialTable[i] = NULL;
446 /// read_weights() reads evaluation weights from the corresponding UCI parameters
448 void read_weights(Color us) {
450 // King safety is asymmetrical. Our king danger level is weighted by
451 // "Cowardice" UCI parameter, instead the opponent one by "Aggressiveness".
452 const int kingDangerUs = (us == WHITE ? KingDangerUs : KingDangerThem);
453 const int kingDangerThem = (us == WHITE ? KingDangerThem : KingDangerUs);
455 Weights[Mobility] = weight_option("Mobility (Middle Game)", "Mobility (Endgame)", WeightsInternal[Mobility]);
456 Weights[PawnStructure] = weight_option("Pawn Structure (Middle Game)", "Pawn Structure (Endgame)", WeightsInternal[PawnStructure]);
457 Weights[PassedPawns] = weight_option("Passed Pawns (Middle Game)", "Passed Pawns (Endgame)", WeightsInternal[PassedPawns]);
458 Weights[Space] = weight_option("Space", "Space", WeightsInternal[Space]);
459 Weights[kingDangerUs] = weight_option("Cowardice", "Cowardice", WeightsInternal[KingDangerUs]);
460 Weights[kingDangerThem] = weight_option("Aggressiveness", "Aggressiveness", WeightsInternal[KingDangerThem]);
462 // If running in analysis mode, make sure we use symmetrical king safety. We do this
463 // by replacing both Weights[kingDangerUs] and Weights[kingDangerThem] by their average.
464 if (get_option_value_bool("UCI_AnalyseMode"))
465 Weights[kingDangerUs] = Weights[kingDangerThem] = (Weights[kingDangerUs] + Weights[kingDangerThem]) / 2;
473 // init_king_tables() initializes king bitboards for both sides adding
474 // pawn attacks. To be done before other evaluations.
476 template<Color Us, bool HasPopCnt>
477 void init_attack_tables(const Position& pos, EvalInfo& ei) {
479 const Color Them = (Us == WHITE ? BLACK : WHITE);
481 Bitboard b = ei.attackedBy[Them][KING] = pos.attacks_from<KING>(pos.king_square(Them));
482 ei.kingZone[Us] = (b | (Us == WHITE ? b >> 8 : b << 8));
483 ei.attackedBy[Us][PAWN] = ei.pi->pawn_attacks(Us);
484 b &= ei.attackedBy[Us][PAWN];
486 ei.kingAttackersCount[Us] = count_1s_max_15<HasPopCnt>(b) / 2;
490 // evaluate_outposts() evaluates bishop and knight outposts squares
492 template<PieceType Piece, Color Us>
493 void evaluate_outposts(const Position& pos, EvalInfo& ei, Square s) {
495 const Color Them = (Us == WHITE ? BLACK : WHITE);
497 // Initial bonus based on square
498 Value bonus = (Piece == BISHOP ? BishopOutpostBonus[relative_square(Us, s)]
499 : KnightOutpostBonus[relative_square(Us, s)]);
501 // Increase bonus if supported by pawn, especially if the opponent has
502 // no minor piece which can exchange the outpost piece
503 if (bonus && bit_is_set(ei.attackedBy[Us][PAWN], s))
505 if ( pos.pieces(KNIGHT, Them) == EmptyBoardBB
506 && (SquaresByColorBB[square_color(s)] & pos.pieces(BISHOP, Them)) == EmptyBoardBB)
507 bonus += bonus + bonus / 2;
511 ei.value += Sign[Us] * make_score(bonus, bonus);
515 // evaluate_pieces<>() assigns bonuses and penalties to the pieces of a given color
517 template<PieceType Piece, Color Us, bool HasPopCnt>
518 void evaluate_pieces(const Position& pos, EvalInfo& ei, Bitboard no_mob_area) {
525 const Color Them = (Us == WHITE ? BLACK : WHITE);
526 const Square* ptr = pos.piece_list_begin(Us, Piece);
528 while ((s = *ptr++) != SQ_NONE)
530 // Find attacked squares, including x-ray attacks for bishops and rooks
531 if (Piece == KNIGHT || Piece == QUEEN)
532 b = pos.attacks_from<Piece>(s);
533 else if (Piece == BISHOP)
534 b = bishop_attacks_bb(s, pos.occupied_squares() & ~pos.pieces(QUEEN, Us));
535 else if (Piece == ROOK)
536 b = rook_attacks_bb(s, pos.occupied_squares() & ~pos.pieces(ROOK, QUEEN, Us));
540 // Update attack info
541 ei.attackedBy[Us][Piece] |= b;
544 if (b & ei.kingZone[Us])
546 ei.kingAttackersCount[Us]++;
547 ei.kingAttackersWeight[Us] += KingAttackWeights[Piece];
548 Bitboard bb = (b & ei.attackedBy[Them][KING]);
550 ei.kingAdjacentZoneAttacksCount[Us] += count_1s_max_15<HasPopCnt>(bb);
554 mob = (Piece != QUEEN ? count_1s_max_15<HasPopCnt>(b & no_mob_area)
555 : count_1s<HasPopCnt>(b & no_mob_area));
557 ei.mobility += Sign[Us] * MobilityBonus[Piece][mob];
559 // Decrease score if we are attacked by an enemy pawn. Remaining part
560 // of threat evaluation must be done later when we have full attack info.
561 if (bit_is_set(ei.attackedBy[Them][PAWN], s))
562 ei.value -= Sign[Us] * ThreatedByPawnPenalty[Piece];
564 // Bishop and knight outposts squares
565 if ((Piece == BISHOP || Piece == KNIGHT) && pos.square_is_weak(s, Us))
566 evaluate_outposts<Piece, Us>(pos, ei, s);
568 // Special patterns: trapped bishops on a7/h7/a2/h2
569 // and trapped bishops on a1/h1/a8/h8 in Chess960.
572 if (bit_is_set(MaskA7H7[Us], s))
573 evaluate_trapped_bishop_a7h7(pos, s, Us, ei);
575 if (Chess960 && bit_is_set(MaskA1H1[Us], s))
576 evaluate_trapped_bishop_a1h1(pos, s, Us, ei);
579 // Queen or rook on 7th rank
580 if ( (Piece == ROOK || Piece == QUEEN)
581 && relative_rank(Us, s) == RANK_7
582 && relative_rank(Us, pos.king_square(Them)) == RANK_8)
584 ei.value += Sign[Us] * (Piece == ROOK ? RookOn7thBonus : QueenOn7thBonus);
587 // Special extra evaluation for rooks
590 // Open and half-open files
592 if (ei.pi->file_is_half_open(Us, f))
594 if (ei.pi->file_is_half_open(Them, f))
595 ei.value += Sign[Us] * RookOpenFileBonus;
597 ei.value += Sign[Us] * RookHalfOpenFileBonus;
600 // Penalize rooks which are trapped inside a king. Penalize more if
601 // king has lost right to castle.
602 if (mob > 6 || ei.pi->file_is_half_open(Us, f))
605 ksq = pos.king_square(Us);
607 if ( square_file(ksq) >= FILE_E
608 && square_file(s) > square_file(ksq)
609 && (relative_rank(Us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
611 // Is there a half-open file between the king and the edge of the board?
612 if (!ei.pi->has_open_file_to_right(Us, square_file(ksq)))
613 ei.value -= Sign[Us] * make_score(pos.can_castle(Us) ? (TrappedRookPenalty - mob * 16) / 2
614 : (TrappedRookPenalty - mob * 16), 0);
616 else if ( square_file(ksq) <= FILE_D
617 && square_file(s) < square_file(ksq)
618 && (relative_rank(Us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
620 // Is there a half-open file between the king and the edge of the board?
621 if (!ei.pi->has_open_file_to_left(Us, square_file(ksq)))
622 ei.value -= Sign[Us] * make_score(pos.can_castle(Us) ? (TrappedRookPenalty - mob * 16) / 2
623 : (TrappedRookPenalty - mob * 16), 0);
630 // evaluate_threats<>() assigns bonuses according to the type of attacking piece
631 // and the type of attacked one.
634 void evaluate_threats(const Position& pos, EvalInfo& ei) {
636 const Color Them = (Us == WHITE ? BLACK : WHITE);
639 Score bonus = make_score(0, 0);
641 // Enemy pieces not defended by a pawn and under our attack
642 Bitboard weakEnemies = pos.pieces_of_color(Them)
643 & ~ei.attackedBy[Them][PAWN]
644 & ei.attackedBy[Us][0];
648 // Add bonus according to type of attacked enemy pieces and to the
649 // type of attacking piece, from knights to queens. Kings are not
650 // considered because are already special handled in king evaluation.
651 for (PieceType pt1 = KNIGHT; pt1 < KING; pt1++)
653 b = ei.attackedBy[Us][pt1] & weakEnemies;
655 for (PieceType pt2 = PAWN; pt2 < KING; pt2++)
656 if (b & pos.pieces(pt2))
657 bonus += ThreatBonus[pt1][pt2];
659 ei.value += Sign[Us] * bonus;
663 // evaluate_pieces_of_color<>() assigns bonuses and penalties to all the
664 // pieces of a given color.
666 template<Color Us, bool HasPopCnt>
667 void evaluate_pieces_of_color(const Position& pos, EvalInfo& ei) {
669 const Color Them = (Us == WHITE ? BLACK : WHITE);
671 // Do not include in mobility squares protected by enemy pawns or occupied by our pieces
672 const Bitboard no_mob_area = ~(ei.attackedBy[Them][PAWN] | pos.pieces_of_color(Us));
674 evaluate_pieces<KNIGHT, Us, HasPopCnt>(pos, ei, no_mob_area);
675 evaluate_pieces<BISHOP, Us, HasPopCnt>(pos, ei, no_mob_area);
676 evaluate_pieces<ROOK, Us, HasPopCnt>(pos, ei, no_mob_area);
677 evaluate_pieces<QUEEN, Us, HasPopCnt>(pos, ei, no_mob_area);
679 // Sum up all attacked squares
680 ei.attackedBy[Us][0] = ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
681 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
682 | ei.attackedBy[Us][QUEEN] | ei.attackedBy[Us][KING];
686 // evaluate_king<>() assigns bonuses and penalties to a king of a given color
688 template<Color Us, bool HasPopCnt>
689 void evaluate_king(const Position& pos, EvalInfo& ei) {
691 const Color Them = (Us == WHITE ? BLACK : WHITE);
693 Bitboard undefended, b, b1, b2, safe;
695 int attackUnits, shelter = 0;
696 const Square ksq = pos.king_square(Us);
699 if (relative_rank(Us, ksq) <= RANK_4)
701 shelter = ei.pi->get_king_shelter(pos, Us, ksq);
702 ei.value += Sign[Us] * make_score(shelter, 0);
705 // King safety. This is quite complicated, and is almost certainly far
706 // from optimally tuned.
707 if ( pos.piece_count(Them, QUEEN) >= 1
708 && ei.kingAttackersCount[Them] >= 2
709 && pos.non_pawn_material(Them) >= QueenValueMidgame + RookValueMidgame
710 && ei.kingAdjacentZoneAttacksCount[Them])
712 // Is it the attackers turn to move?
713 sente = (Them == pos.side_to_move());
715 // Find the attacked squares around the king which has no defenders
716 // apart from the king itself
717 undefended = ei.attacked_by(Them) & ei.attacked_by(Us, KING);
718 undefended &= ~( ei.attacked_by(Us, PAWN) | ei.attacked_by(Us, KNIGHT)
719 | ei.attacked_by(Us, BISHOP) | ei.attacked_by(Us, ROOK)
720 | ei.attacked_by(Us, QUEEN));
722 // Initialize the 'attackUnits' variable, which is used later on as an
723 // index to the KingDangerTable[] array. The initial value is based on
724 // the number and types of the enemy's attacking pieces, the number of
725 // attacked and undefended squares around our king, the square of the
726 // king, and the quality of the pawn shelter.
727 attackUnits = Min(25, (ei.kingAttackersCount[Them] * ei.kingAttackersWeight[Them]) / 2)
728 + 3 * (ei.kingAdjacentZoneAttacksCount[Them] + count_1s_max_15<HasPopCnt>(undefended))
729 + InitKingDanger[relative_square(Us, ksq)]
732 // Analyse enemy's safe queen contact checks. First find undefended
733 // squares around the king attacked by enemy queen...
734 b = undefended & ei.attacked_by(Them, QUEEN) & ~pos.pieces_of_color(Them);
737 // ...then remove squares not supported by another enemy piece
738 b &= ( ei.attacked_by(Them, PAWN) | ei.attacked_by(Them, KNIGHT)
739 | ei.attacked_by(Them, BISHOP) | ei.attacked_by(Them, ROOK));
741 attackUnits += QueenContactCheckBonus * count_1s_max_15<HasPopCnt>(b) * (sente ? 2 : 1);
744 // Analyse enemy's safe distance checks for sliders and knights
745 safe = ~(pos.pieces_of_color(Them) | ei.attacked_by(Us));
747 b1 = pos.attacks_from<ROOK>(ksq) & safe;
748 b2 = pos.attacks_from<BISHOP>(ksq) & safe;
750 // Enemy queen safe checks
751 b = (b1 | b2) & ei.attacked_by(Them, QUEEN);
753 attackUnits += QueenCheckBonus * count_1s_max_15<HasPopCnt>(b);
755 // Enemy rooks safe checks
756 b = b1 & ei.attacked_by(Them, ROOK);
758 attackUnits += RookCheckBonus * count_1s_max_15<HasPopCnt>(b);
760 // Enemy bishops safe checks
761 b = b2 & ei.attacked_by(Them, BISHOP);
763 attackUnits += BishopCheckBonus * count_1s_max_15<HasPopCnt>(b);
765 // Enemy knights safe checks
766 b = pos.attacks_from<KNIGHT>(ksq) & ei.attacked_by(Them, KNIGHT) & safe;
768 attackUnits += KnightCheckBonus * count_1s_max_15<HasPopCnt>(b);
770 // To index KingDangerTable[] attackUnits must be in [0, 99] range
771 attackUnits = Min(99, Max(0, attackUnits));
773 // Finally, extract the king danger score from the KingDangerTable[]
774 // array and subtract the score from evaluation. Set also ei.kingDanger[]
775 // value that will be used for pruning because this value can sometimes
776 // be very big, and so capturing a single attacking piece can therefore
777 // result in a score change far bigger than the value of the captured piece.
778 ei.value -= Sign[Us] * KingDangerTable[Us][attackUnits];
779 ei.kingDanger[Us] = mg_value(KingDangerTable[Us][attackUnits]);
784 // evaluate_passed_pawns<>() evaluates the passed pawns of the given color
787 void evaluate_passed_pawns(const Position& pos, EvalInfo& ei) {
789 const Color Them = (Us == WHITE ? BLACK : WHITE);
791 Bitboard squaresToQueen, defendedSquares, unsafeSquares, supportingPawns;
792 Bitboard b = ei.pi->passed_pawns() & pos.pieces_of_color(Us);
796 Square s = pop_1st_bit(&b);
798 assert(pos.pawn_is_passed(Us, s));
800 int r = int(relative_rank(Us, s) - RANK_2);
801 int tr = r * (r - 1);
803 // Base bonus based on rank
804 Value mbonus = Value(20 * tr);
805 Value ebonus = Value(10 + r * r * 10);
809 Square blockSq = s + pawn_push(Us);
811 // Adjust bonus based on kings proximity
812 ebonus -= Value(square_distance(pos.king_square(Us), blockSq) * 3 * tr);
813 ebonus -= Value(square_distance(pos.king_square(Us), blockSq + pawn_push(Us)) * 1 * tr);
814 ebonus += Value(square_distance(pos.king_square(Them), blockSq) * 6 * tr);
816 // If the pawn is free to advance, increase bonus
817 if (pos.square_is_empty(blockSq))
819 squaresToQueen = squares_in_front_of(Us, s);
820 defendedSquares = squaresToQueen & ei.attacked_by(Us);
822 // If there is an enemy rook or queen attacking the pawn from behind,
823 // add all X-ray attacks by the rook or queen. Otherwise consider only
824 // the squares in the pawn's path attacked or occupied by the enemy.
825 if ( (squares_behind(Us, s) & pos.pieces(ROOK, QUEEN, Them))
826 && (squares_behind(Us, s) & pos.pieces(ROOK, QUEEN, Them) & pos.attacks_from<QUEEN>(s)))
827 unsafeSquares = squaresToQueen;
829 unsafeSquares = squaresToQueen & (ei.attacked_by(Them) | pos.pieces_of_color(Them));
831 // If there aren't enemy attacks or pieces along the path to queen give
832 // huge bonus. Even bigger if we protect the pawn's path.
834 ebonus += Value(tr * (squaresToQueen == defendedSquares ? 17 : 15));
836 // OK, there are enemy attacks or pieces (but not pawns). Are those
837 // squares which are attacked by the enemy also attacked by us ?
838 // If yes, big bonus (but smaller than when there are no enemy attacks),
839 // if no, somewhat smaller bonus.
840 ebonus += Value(tr * ((unsafeSquares & defendedSquares) == unsafeSquares ? 13 : 8));
842 // At last, add a small bonus when there are no *friendly* pieces
843 // in the pawn's path.
844 if (!(squaresToQueen & pos.pieces_of_color(Us)))
849 // Increase the bonus if the passed pawn is supported by a friendly pawn
850 // on the same rank and a bit smaller if it's on the previous rank.
851 supportingPawns = pos.pieces(PAWN, Us) & neighboring_files_bb(s);
852 if (supportingPawns & rank_bb(s))
853 ebonus += Value(r * 20);
854 else if (supportingPawns & rank_bb(s - pawn_push(Us)))
855 ebonus += Value(r * 12);
857 // Rook pawns are a special case: They are sometimes worse, and
858 // sometimes better than other passed pawns. It is difficult to find
859 // good rules for determining whether they are good or bad. For now,
860 // we try the following: Increase the value for rook pawns if the
861 // other side has no pieces apart from a knight, and decrease the
862 // value if the other side has a rook or queen.
863 if (square_file(s) == FILE_A || square_file(s) == FILE_H)
865 if ( pos.non_pawn_material(Them) <= KnightValueMidgame
866 && pos.piece_count(Them, KNIGHT) <= 1)
867 ebonus += ebonus / 4;
868 else if (pos.pieces(ROOK, QUEEN, Them))
869 ebonus -= ebonus / 4;
872 // Add the scores for this pawn to the middle game and endgame eval
873 ei.value += Sign[Us] * apply_weight(make_score(mbonus, ebonus), Weights[PassedPawns]);
879 // evaluate_unstoppable_pawns() evaluates the unstoppable passed pawns for both sides
881 void evaluate_unstoppable_pawns(const Position& pos, EvalInfo& ei) {
883 int movesToGo[2] = {0, 0};
884 Square pawnToGo[2] = {SQ_NONE, SQ_NONE};
886 for (Color c = WHITE; c <= BLACK; c++)
888 // Skip evaluation if other side has non-pawn pieces
889 if (pos.non_pawn_material(opposite_color(c)))
892 Bitboard b = ei.pi->passed_pawns() & pos.pieces_of_color(c);
896 Square s = pop_1st_bit(&b);
897 Square queeningSquare = relative_square(c, make_square(square_file(s), RANK_8));
898 int d = square_distance(s, queeningSquare)
899 - (relative_rank(c, s) == RANK_2) // Double pawn push
900 - square_distance(pos.king_square(opposite_color(c)), queeningSquare)
901 + int(c != pos.side_to_move());
903 // Do we protect the path to queening ?
904 bool pathDefended = (ei.attacked_by(c) & squares_in_front_of(c, s)) == squares_in_front_of(c, s);
906 if (d < 0 || pathDefended)
908 int mtg = RANK_8 - relative_rank(c, s);
909 int blockerCount = count_1s_max_15(squares_in_front_of(c, s) & pos.occupied_squares());
912 if ((d < 0 || pathDefended) && (!movesToGo[c] || movesToGo[c] > mtg))
921 // Neither side has an unstoppable passed pawn?
922 if (!(movesToGo[WHITE] | movesToGo[BLACK]))
925 // Does only one side have an unstoppable passed pawn?
926 if (!movesToGo[WHITE] || !movesToGo[BLACK])
928 Color winnerSide = movesToGo[WHITE] ? WHITE : BLACK;
929 ei.value += make_score(0, Sign[winnerSide] * (UnstoppablePawnValue - Value(0x40 * movesToGo[winnerSide])));
932 { // Both sides have unstoppable pawns! Try to find out who queens
933 // first. We begin by transforming 'movesToGo' to the number of
934 // plies until the pawn queens for both sides.
935 movesToGo[WHITE] *= 2;
936 movesToGo[BLACK] *= 2;
937 movesToGo[pos.side_to_move()]--;
939 Color winnerSide = movesToGo[WHITE] < movesToGo[BLACK] ? WHITE : BLACK;
940 Color loserSide = opposite_color(winnerSide);
942 // If one side queens at least three plies before the other, that side wins
943 if (movesToGo[winnerSide] <= movesToGo[loserSide] - 3)
944 ei.value += Sign[winnerSide] * make_score(0, UnstoppablePawnValue - Value(0x40 * (movesToGo[winnerSide]/2)));
946 // If one side queens one ply before the other and checks the king or attacks
947 // the undefended opponent's queening square, that side wins. To avoid cases
948 // where the opponent's king could move somewhere before first pawn queens we
949 // consider only free paths to queen for both pawns.
950 else if ( !(squares_in_front_of(WHITE, pawnToGo[WHITE]) & pos.occupied_squares())
951 && !(squares_in_front_of(BLACK, pawnToGo[BLACK]) & pos.occupied_squares()))
953 assert(movesToGo[loserSide] - movesToGo[winnerSide] == 1);
955 Square winnerQSq = relative_square(winnerSide, make_square(square_file(pawnToGo[winnerSide]), RANK_8));
956 Square loserQSq = relative_square(loserSide, make_square(square_file(pawnToGo[loserSide]), RANK_8));
958 Bitboard b = pos.occupied_squares();
959 clear_bit(&b, pawnToGo[winnerSide]);
960 clear_bit(&b, pawnToGo[loserSide]);
961 b = queen_attacks_bb(winnerQSq, b);
963 if ( (b & pos.pieces(KING, loserSide))
964 ||(bit_is_set(b, loserQSq) && !bit_is_set(ei.attacked_by(loserSide), loserQSq)))
965 ei.value += Sign[winnerSide] * make_score(0, UnstoppablePawnValue - Value(0x40 * (movesToGo[winnerSide]/2)));
971 // evaluate_trapped_bishop_a7h7() determines whether a bishop on a7/h7
972 // (a2/h2 for black) is trapped by enemy pawns, and assigns a penalty
975 void evaluate_trapped_bishop_a7h7(const Position& pos, Square s, Color us, EvalInfo &ei) {
977 assert(square_is_ok(s));
978 assert(pos.piece_on(s) == piece_of_color_and_type(us, BISHOP));
980 Square b6 = relative_square(us, (square_file(s) == FILE_A) ? SQ_B6 : SQ_G6);
981 Square b8 = relative_square(us, (square_file(s) == FILE_A) ? SQ_B8 : SQ_G8);
983 if ( pos.piece_on(b6) == piece_of_color_and_type(opposite_color(us), PAWN)
984 && pos.see(s, b6) < 0
985 && pos.see(s, b8) < 0)
987 ei.value -= Sign[us] * TrappedBishopA7H7Penalty;
992 // evaluate_trapped_bishop_a1h1() determines whether a bishop on a1/h1
993 // (a8/h8 for black) is trapped by a friendly pawn on b2/g2 (b7/g7 for
994 // black), and assigns a penalty if it is. This pattern can obviously
995 // only occur in Chess960 games.
997 void evaluate_trapped_bishop_a1h1(const Position& pos, Square s, Color us, EvalInfo& ei) {
999 Piece pawn = piece_of_color_and_type(us, PAWN);
1003 assert(square_is_ok(s));
1004 assert(pos.piece_on(s) == piece_of_color_and_type(us, BISHOP));
1006 if (square_file(s) == FILE_A)
1008 b2 = relative_square(us, SQ_B2);
1009 b3 = relative_square(us, SQ_B3);
1010 c3 = relative_square(us, SQ_C3);
1014 b2 = relative_square(us, SQ_G2);
1015 b3 = relative_square(us, SQ_G3);
1016 c3 = relative_square(us, SQ_F3);
1019 if (pos.piece_on(b2) == pawn)
1023 if (!pos.square_is_empty(b3))
1024 penalty = 2 * TrappedBishopA1H1Penalty;
1025 else if (pos.piece_on(c3) == pawn)
1026 penalty = TrappedBishopA1H1Penalty;
1028 penalty = TrappedBishopA1H1Penalty / 2;
1030 ei.value -= Sign[us] * penalty;
1035 // evaluate_space() computes the space evaluation for a given side. The
1036 // space evaluation is a simple bonus based on the number of safe squares
1037 // available for minor pieces on the central four files on ranks 2--4. Safe
1038 // squares one, two or three squares behind a friendly pawn are counted
1039 // twice. Finally, the space bonus is scaled by a weight taken from the
1040 // material hash table.
1041 template<Color Us, bool HasPopCnt>
1042 void evaluate_space(const Position& pos, EvalInfo& ei) {
1044 const Color Them = (Us == WHITE ? BLACK : WHITE);
1046 // Find the safe squares for our pieces inside the area defined by
1047 // SpaceMask[us]. A square is unsafe if it is attacked by an enemy
1048 // pawn, or if it is undefended and attacked by an enemy piece.
1049 Bitboard safeSquares = SpaceMask[Us]
1050 & ~pos.pieces(PAWN, Us)
1051 & ~ei.attacked_by(Them, PAWN)
1052 & (ei.attacked_by(Us) | ~ei.attacked_by(Them));
1054 // Find all squares which are at most three squares behind some friendly pawn
1055 Bitboard behindFriendlyPawns = pos.pieces(PAWN, Us);
1056 behindFriendlyPawns |= (Us == WHITE ? behindFriendlyPawns >> 8 : behindFriendlyPawns << 8);
1057 behindFriendlyPawns |= (Us == WHITE ? behindFriendlyPawns >> 16 : behindFriendlyPawns << 16);
1059 int space = count_1s_max_15<HasPopCnt>(safeSquares)
1060 + count_1s_max_15<HasPopCnt>(behindFriendlyPawns & safeSquares);
1062 ei.value += Sign[Us] * apply_weight(make_score(space * ei.mi->space_weight(), 0), Weights[Space]);
1066 // apply_weight() applies an evaluation weight to a value trying to prevent overflow
1068 inline Score apply_weight(Score v, Score w) {
1069 return make_score((int(mg_value(v)) * mg_value(w)) / 0x100, (int(eg_value(v)) * eg_value(w)) / 0x100);
1073 // scale_by_game_phase() interpolates between a middle game and an endgame
1074 // score, based on game phase. It also scales the return value by a
1075 // ScaleFactor array.
1077 Value scale_by_game_phase(const Score& v, Phase ph, const ScaleFactor sf[]) {
1079 assert(mg_value(v) > -VALUE_INFINITE && mg_value(v) < VALUE_INFINITE);
1080 assert(eg_value(v) > -VALUE_INFINITE && eg_value(v) < VALUE_INFINITE);
1081 assert(ph >= PHASE_ENDGAME && ph <= PHASE_MIDGAME);
1083 Value ev = apply_scale_factor(eg_value(v), sf[(eg_value(v) > Value(0) ? WHITE : BLACK)]);
1085 int result = (mg_value(v) * ph + ev * (128 - ph)) / 128;
1086 return Value(result & ~(GrainSize - 1));
1090 // weight_option() computes the value of an evaluation weight, by combining
1091 // two UCI-configurable weights (midgame and endgame) with an internal weight.
1093 Score weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight) {
1095 // Scale option value from 100 to 256
1096 int mg = get_option_value_int(mgOpt) * 256 / 100;
1097 int eg = get_option_value_int(egOpt) * 256 / 100;
1099 return apply_weight(make_score(mg, eg), internalWeight);
1102 // init_safety() initizes the king safety evaluation, based on UCI
1103 // parameters. It is called from read_weights().
1105 void init_safety() {
1107 const Value MaxSlope = Value(30);
1108 const Value Peak = Value(1280);
1111 // First setup the base table
1112 for (int i = 0; i < 100; i++)
1114 t[i] = Value(int(0.4 * i * i));
1117 t[i] = Min(t[i], t[i - 1] + MaxSlope);
1119 t[i] = Min(t[i], Peak);
1122 // Then apply the weights and get the final KingDangerTable[] array
1123 for (Color c = WHITE; c <= BLACK; c++)
1124 for (int i = 0; i < 100; i++)
1125 KingDangerTable[c][i] = apply_weight(make_score(t[i], 0), Weights[KingDangerUs + c]);