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 QueenCheckBonus = 2;
211 const int RookCheckBonus = 1;
212 const int BishopCheckBonus = 1;
213 const int KnightCheckBonus = 1;
215 // InitKingDanger[] contains bonuses based on the position of the defending
217 const int InitKingDanger[64] = {
218 2, 0, 2, 5, 5, 2, 0, 2,
219 2, 2, 4, 8, 8, 4, 2, 2,
220 7, 10, 12, 12, 12, 12, 10, 7,
221 15, 15, 15, 15, 15, 15, 15, 15,
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
228 // KingDangerTable[color][] contains the actual king danger weighted scores
229 Score KingDangerTable[2][128];
231 // Pawn and material hash tables, indexed by the current thread id.
232 // Note that they will be initialized at 0 being global variables.
233 MaterialInfoTable* MaterialTable[MAX_THREADS];
234 PawnInfoTable* PawnTable[MAX_THREADS];
236 // Sizes of pawn and material hash tables
237 const int PawnTableSize = 16384;
238 const int MaterialTableSize = 1024;
240 // Function prototypes
241 template<bool HasPopCnt>
242 Value do_evaluate(const Position& pos, EvalInfo& ei);
244 template<Color Us, bool HasPopCnt>
245 void init_attack_tables(const Position& pos, EvalInfo& ei);
247 template<Color Us, bool HasPopCnt>
248 void evaluate_pieces_of_color(const Position& pos, EvalInfo& ei);
250 template<Color Us, bool HasPopCnt>
251 void evaluate_king(const Position& pos, EvalInfo& ei);
254 void evaluate_threats(const Position& pos, EvalInfo& ei);
256 template<Color Us, bool HasPopCnt>
257 int evaluate_space(const Position& pos, EvalInfo& ei);
260 void evaluate_passed_pawns(const Position& pos, EvalInfo& ei);
262 void evaluate_unstoppable_pawns(const Position& pos, EvalInfo& ei);
263 void evaluate_trapped_bishop_a7h7(const Position& pos, Square s, Color us, EvalInfo& ei);
264 void evaluate_trapped_bishop_a1h1(const Position& pos, Square s, Color us, EvalInfo& ei);
265 inline Score apply_weight(Score v, Score weight);
266 Value scale_by_game_phase(const Score& v, Phase ph, const ScaleFactor sf[]);
267 Score weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight);
276 /// evaluate() is the main evaluation function. It always computes two
277 /// values, an endgame score and a middle game score, and interpolates
278 /// between them based on the remaining material.
279 Value evaluate(const Position& pos, EvalInfo& ei) {
281 return CpuHasPOPCNT ? do_evaluate<true>(pos, ei)
282 : do_evaluate<false>(pos, ei);
287 template<bool HasPopCnt>
288 Value do_evaluate(const Position& pos, EvalInfo& ei) {
290 ScaleFactor factor[2];
293 assert(pos.thread() >= 0 && pos.thread() < MAX_THREADS);
294 assert(!pos.is_check());
296 memset(&ei, 0, sizeof(EvalInfo));
298 // Initialize by reading the incrementally updated scores included in the
299 // position object (material + piece square tables)
300 ei.value = pos.value();
302 // Probe the material hash table
303 ei.mi = MaterialTable[pos.thread()]->get_material_info(pos);
304 ei.value += ei.mi->material_value();
306 // If we have a specialized evaluation function for the current material
307 // configuration, call it and return
308 if (ei.mi->specialized_eval_exists())
309 return ei.mi->evaluate(pos);
311 // After get_material_info() call that modifies them
312 factor[WHITE] = ei.mi->scale_factor(pos, WHITE);
313 factor[BLACK] = ei.mi->scale_factor(pos, BLACK);
315 // Probe the pawn hash table
316 ei.pi = PawnTable[pos.thread()]->get_pawn_info(pos);
317 ei.value += apply_weight(ei.pi->pawns_value(), Weights[PawnStructure]);
319 // Initialize attack bitboards with pawns evaluation
320 init_attack_tables<WHITE, HasPopCnt>(pos, ei);
321 init_attack_tables<BLACK, HasPopCnt>(pos, ei);
324 evaluate_pieces_of_color<WHITE, HasPopCnt>(pos, ei);
325 evaluate_pieces_of_color<BLACK, HasPopCnt>(pos, ei);
327 // Kings. Kings are evaluated after all other pieces for both sides,
328 // because we need complete attack information for all pieces when computing
329 // the king safety evaluation.
330 evaluate_king<WHITE, HasPopCnt>(pos, ei);
331 evaluate_king<BLACK, HasPopCnt>(pos, ei);
333 // Evaluate tactical threats, we need full attack info including king
334 evaluate_threats<WHITE>(pos, ei);
335 evaluate_threats<BLACK>(pos, ei);
337 // Evaluate passed pawns, we need full attack info including king
338 evaluate_passed_pawns<WHITE>(pos, ei);
339 evaluate_passed_pawns<BLACK>(pos, ei);
341 // If one side has only a king, check whether exsists any unstoppable passed pawn
342 if (!pos.non_pawn_material(WHITE) || !pos.non_pawn_material(BLACK))
343 evaluate_unstoppable_pawns(pos, ei);
345 Phase phase = ei.mi->game_phase();
347 // Middle-game specific evaluation terms
348 if (phase > PHASE_ENDGAME)
350 // Pawn storms in positions with opposite castling
351 if ( square_file(pos.king_square(WHITE)) >= FILE_E
352 && square_file(pos.king_square(BLACK)) <= FILE_D)
354 ei.value += make_score(ei.pi->queenside_storm_value(WHITE) - ei.pi->kingside_storm_value(BLACK), 0);
356 else if ( square_file(pos.king_square(WHITE)) <= FILE_D
357 && square_file(pos.king_square(BLACK)) >= FILE_E)
359 ei.value += make_score(ei.pi->kingside_storm_value(WHITE) - ei.pi->queenside_storm_value(BLACK), 0);
361 // Evaluate space for both sides
362 if (ei.mi->space_weight() > 0)
364 int s = evaluate_space<WHITE, HasPopCnt>(pos, ei) - evaluate_space<BLACK, HasPopCnt>(pos, ei);
365 ei.value += apply_weight(make_score(s * ei.mi->space_weight(), 0), Weights[Space]);
370 ei.value += apply_weight(ei.mobility, Weights[Mobility]);
372 // If we don't already have an unusual scale factor, check for opposite
373 // colored bishop endgames, and use a lower scale for those
374 if ( phase < PHASE_MIDGAME
375 && pos.opposite_colored_bishops()
376 && ( (factor[WHITE] == SCALE_FACTOR_NORMAL && eg_value(ei.value) > Value(0))
377 || (factor[BLACK] == SCALE_FACTOR_NORMAL && eg_value(ei.value) < Value(0))))
381 // Only the two bishops ?
382 if ( pos.non_pawn_material(WHITE) == BishopValueMidgame
383 && pos.non_pawn_material(BLACK) == BishopValueMidgame)
385 // Check for KBP vs KB with only a single pawn that is almost
386 // certainly a draw or at least two pawns.
387 bool one_pawn = (pos.piece_count(WHITE, PAWN) + pos.piece_count(BLACK, PAWN) == 1);
388 sf = one_pawn ? ScaleFactor(8) : ScaleFactor(32);
391 // Endgame with opposite-colored bishops, but also other pieces. Still
392 // a bit drawish, but not as drawish as with only the two bishops.
393 sf = ScaleFactor(50);
395 if (factor[WHITE] == SCALE_FACTOR_NORMAL)
397 if (factor[BLACK] == SCALE_FACTOR_NORMAL)
401 // Interpolate between the middle game and the endgame score
402 return Sign[pos.side_to_move()] * scale_by_game_phase(ei.value, phase, factor);
407 /// init_eval() initializes various tables used by the evaluation function
409 void init_eval(int threads) {
411 assert(threads <= MAX_THREADS);
413 for (int i = 0; i < MAX_THREADS; i++)
418 delete MaterialTable[i];
420 MaterialTable[i] = NULL;
424 PawnTable[i] = new PawnInfoTable(PawnTableSize);
425 if (!MaterialTable[i])
426 MaterialTable[i] = new MaterialInfoTable(MaterialTableSize);
431 /// quit_eval() releases heap-allocated memory at program termination
435 for (int i = 0; i < MAX_THREADS; i++)
438 delete MaterialTable[i];
440 MaterialTable[i] = NULL;
445 /// read_weights() reads evaluation weights from the corresponding UCI parameters
447 void read_weights(Color us) {
449 // King safety is asymmetrical. Our king danger level is weighted by
450 // "Cowardice" UCI parameter, instead the opponent one by "Aggressiveness".
451 const int kingDangerUs = (us == WHITE ? KingDangerUs : KingDangerThem);
452 const int kingDangerThem = (us == WHITE ? KingDangerThem : KingDangerUs);
454 Weights[Mobility] = weight_option("Mobility (Middle Game)", "Mobility (Endgame)", WeightsInternal[Mobility]);
455 Weights[PawnStructure] = weight_option("Pawn Structure (Middle Game)", "Pawn Structure (Endgame)", WeightsInternal[PawnStructure]);
456 Weights[PassedPawns] = weight_option("Passed Pawns (Middle Game)", "Passed Pawns (Endgame)", WeightsInternal[PassedPawns]);
457 Weights[Space] = weight_option("Space", "Space", WeightsInternal[Space]);
458 Weights[kingDangerUs] = weight_option("Cowardice", "Cowardice", WeightsInternal[KingDangerUs]);
459 Weights[kingDangerThem] = weight_option("Aggressiveness", "Aggressiveness", WeightsInternal[KingDangerThem]);
461 // If running in analysis mode, make sure we use symmetrical king safety. We do this
462 // by replacing both Weights[kingDangerUs] and Weights[kingDangerThem] by their average.
463 if (get_option_value_bool("UCI_AnalyseMode"))
464 Weights[kingDangerUs] = Weights[kingDangerThem] = (Weights[kingDangerUs] + Weights[kingDangerThem]) / 2;
472 // init_attack_tables() initializes king bitboards for both sides adding
473 // pawn attacks. To be done before other evaluations.
475 template<Color Us, bool HasPopCnt>
476 void init_attack_tables(const Position& pos, EvalInfo& ei) {
478 const Color Them = (Us == WHITE ? BLACK : WHITE);
480 Bitboard b = ei.attackedBy[Them][KING] = pos.attacks_from<KING>(pos.king_square(Them));
481 ei.kingZone[Us] = (b | (Us == WHITE ? b >> 8 : b << 8));
482 ei.attackedBy[Us][PAWN] = ei.pi->pawn_attacks(Us);
483 b &= ei.attackedBy[Us][PAWN];
485 ei.kingAttackersCount[Us] = count_1s_max_15<HasPopCnt>(b) / 2;
489 // evaluate_outposts() evaluates bishop and knight outposts squares
491 template<PieceType Piece, Color Us>
492 void evaluate_outposts(const Position& pos, EvalInfo& ei, Square s) {
494 const Color Them = (Us == WHITE ? BLACK : WHITE);
496 // Initial bonus based on square
497 Value bonus = (Piece == BISHOP ? BishopOutpostBonus[relative_square(Us, s)]
498 : KnightOutpostBonus[relative_square(Us, s)]);
500 // Increase bonus if supported by pawn, especially if the opponent has
501 // no minor piece which can exchange the outpost piece
502 if (bonus && bit_is_set(ei.attackedBy[Us][PAWN], s))
504 if ( pos.pieces(KNIGHT, Them) == EmptyBoardBB
505 && (SquaresByColorBB[square_color(s)] & pos.pieces(BISHOP, Them)) == EmptyBoardBB)
506 bonus += bonus + bonus / 2;
510 ei.value += Sign[Us] * make_score(bonus, bonus);
514 // evaluate_pieces<>() assigns bonuses and penalties to the pieces of a given color
516 template<PieceType Piece, Color Us, bool HasPopCnt>
517 void evaluate_pieces(const Position& pos, EvalInfo& ei, Bitboard no_mob_area) {
524 const Color Them = (Us == WHITE ? BLACK : WHITE);
525 const Square* ptr = pos.piece_list_begin(Us, Piece);
527 while ((s = *ptr++) != SQ_NONE)
529 // Find attacked squares, including x-ray attacks for bishops and rooks
530 if (Piece == KNIGHT || Piece == QUEEN)
531 b = pos.attacks_from<Piece>(s);
532 else if (Piece == BISHOP)
533 b = bishop_attacks_bb(s, pos.occupied_squares() & ~pos.pieces(QUEEN, Us));
534 else if (Piece == ROOK)
535 b = rook_attacks_bb(s, pos.occupied_squares() & ~pos.pieces(ROOK, QUEEN, Us));
539 // Update attack info
540 ei.attackedBy[Us][Piece] |= b;
543 if (b & ei.kingZone[Us])
545 ei.kingAttackersCount[Us]++;
546 ei.kingAttackersWeight[Us] += KingAttackWeights[Piece];
547 Bitboard bb = (b & ei.attackedBy[Them][KING]);
549 ei.kingAdjacentZoneAttacksCount[Us] += count_1s_max_15<HasPopCnt>(bb);
553 mob = (Piece != QUEEN ? count_1s_max_15<HasPopCnt>(b & no_mob_area)
554 : count_1s<HasPopCnt>(b & no_mob_area));
556 ei.mobility += Sign[Us] * MobilityBonus[Piece][mob];
558 // Decrease score if we are attacked by an enemy pawn. Remaining part
559 // of threat evaluation must be done later when we have full attack info.
560 if (bit_is_set(ei.attackedBy[Them][PAWN], s))
561 ei.value -= Sign[Us] * ThreatedByPawnPenalty[Piece];
563 // Bishop and knight outposts squares
564 if ((Piece == BISHOP || Piece == KNIGHT) && pos.square_is_weak(s, Us))
565 evaluate_outposts<Piece, Us>(pos, ei, s);
567 // Special patterns: trapped bishops on a7/h7/a2/h2
568 // and trapped bishops on a1/h1/a8/h8 in Chess960.
571 if (bit_is_set(MaskA7H7[Us], s))
572 evaluate_trapped_bishop_a7h7(pos, s, Us, ei);
574 if (Chess960 && bit_is_set(MaskA1H1[Us], s))
575 evaluate_trapped_bishop_a1h1(pos, s, Us, ei);
578 // Queen or rook on 7th rank
579 if ( (Piece == ROOK || Piece == QUEEN)
580 && relative_rank(Us, s) == RANK_7
581 && relative_rank(Us, pos.king_square(Them)) == RANK_8)
583 ei.value += Sign[Us] * (Piece == ROOK ? RookOn7thBonus : QueenOn7thBonus);
586 // Special extra evaluation for rooks
589 // Open and half-open files
591 if (ei.pi->file_is_half_open(Us, f))
593 if (ei.pi->file_is_half_open(Them, f))
594 ei.value += Sign[Us] * RookOpenFileBonus;
596 ei.value += Sign[Us] * RookHalfOpenFileBonus;
599 // Penalize rooks which are trapped inside a king. Penalize more if
600 // king has lost right to castle.
601 if (mob > 6 || ei.pi->file_is_half_open(Us, f))
604 ksq = pos.king_square(Us);
606 if ( square_file(ksq) >= FILE_E
607 && square_file(s) > square_file(ksq)
608 && (relative_rank(Us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
610 // Is there a half-open file between the king and the edge of the board?
611 if (!ei.pi->has_open_file_to_right(Us, square_file(ksq)))
612 ei.value -= Sign[Us] * make_score(pos.can_castle(Us) ? (TrappedRookPenalty - mob * 16) / 2
613 : (TrappedRookPenalty - mob * 16), 0);
615 else if ( square_file(ksq) <= FILE_D
616 && square_file(s) < square_file(ksq)
617 && (relative_rank(Us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
619 // Is there a half-open file between the king and the edge of the board?
620 if (!ei.pi->has_open_file_to_left(Us, square_file(ksq)))
621 ei.value -= Sign[Us] * make_score(pos.can_castle(Us) ? (TrappedRookPenalty - mob * 16) / 2
622 : (TrappedRookPenalty - mob * 16), 0);
629 // evaluate_threats<>() assigns bonuses according to the type of attacking piece
630 // and the type of attacked one.
633 void evaluate_threats(const Position& pos, EvalInfo& ei) {
635 const Color Them = (Us == WHITE ? BLACK : WHITE);
638 Score bonus = make_score(0, 0);
640 // Enemy pieces not defended by a pawn and under our attack
641 Bitboard weakEnemies = pos.pieces_of_color(Them)
642 & ~ei.attackedBy[Them][PAWN]
643 & ei.attackedBy[Us][0];
647 // Add bonus according to type of attacked enemy pieces and to the
648 // type of attacking piece, from knights to queens. Kings are not
649 // considered because are already special handled in king evaluation.
650 for (PieceType pt1 = KNIGHT; pt1 < KING; pt1++)
652 b = ei.attackedBy[Us][pt1] & weakEnemies;
654 for (PieceType pt2 = PAWN; pt2 < KING; pt2++)
655 if (b & pos.pieces(pt2))
656 bonus += ThreatBonus[pt1][pt2];
658 ei.value += Sign[Us] * bonus;
662 // evaluate_pieces_of_color<>() assigns bonuses and penalties to all the
663 // pieces of a given color.
665 template<Color Us, bool HasPopCnt>
666 void evaluate_pieces_of_color(const Position& pos, EvalInfo& ei) {
668 const Color Them = (Us == WHITE ? BLACK : WHITE);
670 // Do not include in mobility squares protected by enemy pawns or occupied by our pieces
671 const Bitboard no_mob_area = ~(ei.attackedBy[Them][PAWN] | pos.pieces_of_color(Us));
673 evaluate_pieces<KNIGHT, Us, HasPopCnt>(pos, ei, no_mob_area);
674 evaluate_pieces<BISHOP, Us, HasPopCnt>(pos, ei, no_mob_area);
675 evaluate_pieces<ROOK, Us, HasPopCnt>(pos, ei, no_mob_area);
676 evaluate_pieces<QUEEN, Us, HasPopCnt>(pos, ei, no_mob_area);
678 // Sum up all attacked squares
679 ei.attackedBy[Us][0] = ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
680 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
681 | ei.attackedBy[Us][QUEEN] | ei.attackedBy[Us][KING];
685 // evaluate_king<>() assigns bonuses and penalties to a king of a given color
687 template<Color Us, bool HasPopCnt>
688 void evaluate_king(const Position& pos, EvalInfo& ei) {
690 const Color Them = (Us == WHITE ? BLACK : WHITE);
692 Bitboard undefended, b, b1, b2, safe;
694 int attackUnits, shelter = 0;
695 const Square ksq = pos.king_square(Us);
698 if (relative_rank(Us, ksq) <= RANK_4)
700 shelter = ei.pi->get_king_shelter(pos, Us, ksq);
701 ei.value += Sign[Us] * make_score(shelter, 0);
704 // King safety. This is quite complicated, and is almost certainly far
705 // from optimally tuned.
706 if ( pos.piece_count(Them, QUEEN) >= 1
707 && ei.kingAttackersCount[Them] >= 2
708 && pos.non_pawn_material(Them) >= QueenValueMidgame + RookValueMidgame
709 && ei.kingAdjacentZoneAttacksCount[Them])
711 // Is it the attackers turn to move?
712 sente = (Them == pos.side_to_move());
714 // Find the attacked squares around the king which has no defenders
715 // apart from the king itself
716 undefended = ei.attacked_by(Them) & ei.attacked_by(Us, KING);
717 undefended &= ~( ei.attacked_by(Us, PAWN) | ei.attacked_by(Us, KNIGHT)
718 | ei.attacked_by(Us, BISHOP) | ei.attacked_by(Us, ROOK)
719 | ei.attacked_by(Us, QUEEN));
721 // Initialize the 'attackUnits' variable, which is used later on as an
722 // index to the KingDangerTable[] array. The initial value is based on
723 // the number and types of the enemy's attacking pieces, the number of
724 // attacked and undefended squares around our king, the square of the
725 // king, and the quality of the pawn shelter.
726 attackUnits = Min(25, (ei.kingAttackersCount[Them] * ei.kingAttackersWeight[Them]) / 2)
727 + 3 * (ei.kingAdjacentZoneAttacksCount[Them] + count_1s_max_15<HasPopCnt>(undefended))
728 + InitKingDanger[relative_square(Us, ksq)]
731 // Analyse enemy's safe queen contact checks. First find undefended
732 // squares around the king attacked by enemy queen...
733 b = undefended & ei.attacked_by(Them, QUEEN) & ~pos.pieces_of_color(Them);
736 // ...then remove squares not supported by another enemy piece
737 b &= ( ei.attacked_by(Them, PAWN) | ei.attacked_by(Them, KNIGHT)
738 | ei.attacked_by(Them, BISHOP) | ei.attacked_by(Them, ROOK));
740 attackUnits += QueenContactCheckBonus * count_1s_max_15<HasPopCnt>(b) * (sente ? 2 : 1);
743 // Analyse enemy's safe distance checks for sliders and knights
744 safe = ~(pos.pieces_of_color(Them) | ei.attacked_by(Us));
746 b1 = pos.attacks_from<ROOK>(ksq) & safe;
747 b2 = pos.attacks_from<BISHOP>(ksq) & safe;
749 // Enemy queen safe checks
750 b = (b1 | b2) & ei.attacked_by(Them, QUEEN);
752 attackUnits += QueenCheckBonus * count_1s_max_15<HasPopCnt>(b);
754 // Enemy rooks safe checks
755 b = b1 & ei.attacked_by(Them, ROOK);
757 attackUnits += RookCheckBonus * count_1s_max_15<HasPopCnt>(b);
759 // Enemy bishops safe checks
760 b = b2 & ei.attacked_by(Them, BISHOP);
762 attackUnits += BishopCheckBonus * count_1s_max_15<HasPopCnt>(b);
764 // Enemy knights safe checks
765 b = pos.attacks_from<KNIGHT>(ksq) & ei.attacked_by(Them, KNIGHT) & safe;
767 attackUnits += KnightCheckBonus * count_1s_max_15<HasPopCnt>(b);
769 // To index KingDangerTable[] attackUnits must be in [0, 99] range
770 attackUnits = Min(99, Max(0, attackUnits));
772 // Finally, extract the king danger score from the KingDangerTable[]
773 // array and subtract the score from evaluation. Set also ei.kingDanger[]
774 // value that will be used for pruning because this value can sometimes
775 // be very big, and so capturing a single attacking piece can therefore
776 // result in a score change far bigger than the value of the captured piece.
777 ei.value -= Sign[Us] * KingDangerTable[Us][attackUnits];
778 ei.kingDanger[Us] = mg_value(KingDangerTable[Us][attackUnits]);
783 // evaluate_passed_pawns<>() evaluates the passed pawns of the given color
786 void evaluate_passed_pawns(const Position& pos, EvalInfo& ei) {
788 const Color Them = (Us == WHITE ? BLACK : WHITE);
790 Bitboard squaresToQueen, defendedSquares, unsafeSquares, supportingPawns;
791 Bitboard b = ei.pi->passed_pawns() & pos.pieces_of_color(Us);
795 Square s = pop_1st_bit(&b);
797 assert(pos.pawn_is_passed(Us, s));
799 int r = int(relative_rank(Us, s) - RANK_2);
800 int tr = r * (r - 1);
802 // Base bonus based on rank
803 Value mbonus = Value(20 * tr);
804 Value ebonus = Value(10 + r * r * 10);
808 Square blockSq = s + pawn_push(Us);
810 // Adjust bonus based on kings proximity
811 ebonus -= Value(square_distance(pos.king_square(Us), blockSq) * 3 * tr);
812 ebonus -= Value(square_distance(pos.king_square(Us), blockSq + pawn_push(Us)) * 1 * tr);
813 ebonus += Value(square_distance(pos.king_square(Them), blockSq) * 6 * tr);
815 // If the pawn is free to advance, increase bonus
816 if (pos.square_is_empty(blockSq))
818 squaresToQueen = squares_in_front_of(Us, s);
819 defendedSquares = squaresToQueen & ei.attacked_by(Us);
821 // If there is an enemy rook or queen attacking the pawn from behind,
822 // add all X-ray attacks by the rook or queen. Otherwise consider only
823 // the squares in the pawn's path attacked or occupied by the enemy.
824 if ( (squares_behind(Us, s) & pos.pieces(ROOK, QUEEN, Them))
825 && (squares_behind(Us, s) & pos.pieces(ROOK, QUEEN, Them) & pos.attacks_from<QUEEN>(s)))
826 unsafeSquares = squaresToQueen;
828 unsafeSquares = squaresToQueen & (ei.attacked_by(Them) | pos.pieces_of_color(Them));
830 // If there aren't enemy attacks or pieces along the path to queen give
831 // huge bonus. Even bigger if we protect the pawn's path.
833 ebonus += Value(tr * (squaresToQueen == defendedSquares ? 17 : 15));
835 // OK, there are enemy attacks or pieces (but not pawns). Are those
836 // squares which are attacked by the enemy also attacked by us ?
837 // If yes, big bonus (but smaller than when there are no enemy attacks),
838 // if no, somewhat smaller bonus.
839 ebonus += Value(tr * ((unsafeSquares & defendedSquares) == unsafeSquares ? 13 : 8));
841 // At last, add a small bonus when there are no *friendly* pieces
842 // in the pawn's path.
843 if (!(squaresToQueen & pos.pieces_of_color(Us)))
848 // Increase the bonus if the passed pawn is supported by a friendly pawn
849 // on the same rank and a bit smaller if it's on the previous rank.
850 supportingPawns = pos.pieces(PAWN, Us) & neighboring_files_bb(s);
851 if (supportingPawns & rank_bb(s))
852 ebonus += Value(r * 20);
853 else if (supportingPawns & rank_bb(s - pawn_push(Us)))
854 ebonus += Value(r * 12);
856 // Rook pawns are a special case: They are sometimes worse, and
857 // sometimes better than other passed pawns. It is difficult to find
858 // good rules for determining whether they are good or bad. For now,
859 // we try the following: Increase the value for rook pawns if the
860 // other side has no pieces apart from a knight, and decrease the
861 // value if the other side has a rook or queen.
862 if (square_file(s) == FILE_A || square_file(s) == FILE_H)
864 if ( pos.non_pawn_material(Them) <= KnightValueMidgame
865 && pos.piece_count(Them, KNIGHT) <= 1)
866 ebonus += ebonus / 4;
867 else if (pos.pieces(ROOK, QUEEN, Them))
868 ebonus -= ebonus / 4;
871 // Add the scores for this pawn to the middle game and endgame eval
872 ei.value += Sign[Us] * apply_weight(make_score(mbonus, ebonus), Weights[PassedPawns]);
878 // evaluate_unstoppable_pawns() evaluates the unstoppable passed pawns for both sides
880 void evaluate_unstoppable_pawns(const Position& pos, EvalInfo& ei) {
882 int movesToGo[2] = {0, 0};
883 Square pawnToGo[2] = {SQ_NONE, SQ_NONE};
885 for (Color c = WHITE; c <= BLACK; c++)
887 // Skip evaluation if other side has non-pawn pieces
888 if (pos.non_pawn_material(opposite_color(c)))
891 Bitboard b = ei.pi->passed_pawns() & pos.pieces_of_color(c);
895 Square s = pop_1st_bit(&b);
896 Square queeningSquare = relative_square(c, make_square(square_file(s), RANK_8));
897 int d = square_distance(s, queeningSquare)
898 - (relative_rank(c, s) == RANK_2) // Double pawn push
899 - square_distance(pos.king_square(opposite_color(c)), queeningSquare)
900 + int(c != pos.side_to_move());
902 // Do we protect the path to queening ?
903 bool pathDefended = (ei.attacked_by(c) & squares_in_front_of(c, s)) == squares_in_front_of(c, s);
905 if (d < 0 || pathDefended)
907 int mtg = RANK_8 - relative_rank(c, s);
908 int blockerCount = count_1s_max_15(squares_in_front_of(c, s) & pos.occupied_squares());
911 if ((d < 0 || pathDefended) && (!movesToGo[c] || movesToGo[c] > mtg))
920 // Neither side has an unstoppable passed pawn?
921 if (!(movesToGo[WHITE] | movesToGo[BLACK]))
924 // Does only one side have an unstoppable passed pawn?
925 if (!movesToGo[WHITE] || !movesToGo[BLACK])
927 Color winnerSide = movesToGo[WHITE] ? WHITE : BLACK;
928 ei.value += make_score(0, Sign[winnerSide] * (UnstoppablePawnValue - Value(0x40 * movesToGo[winnerSide])));
931 { // Both sides have unstoppable pawns! Try to find out who queens
932 // first. We begin by transforming 'movesToGo' to the number of
933 // plies until the pawn queens for both sides.
934 movesToGo[WHITE] *= 2;
935 movesToGo[BLACK] *= 2;
936 movesToGo[pos.side_to_move()]--;
938 Color winnerSide = movesToGo[WHITE] < movesToGo[BLACK] ? WHITE : BLACK;
939 Color loserSide = opposite_color(winnerSide);
941 // If one side queens at least three plies before the other, that side wins
942 if (movesToGo[winnerSide] <= movesToGo[loserSide] - 3)
943 ei.value += Sign[winnerSide] * make_score(0, UnstoppablePawnValue - Value(0x40 * (movesToGo[winnerSide]/2)));
945 // If one side queens one ply before the other and checks the king or attacks
946 // the undefended opponent's queening square, that side wins. To avoid cases
947 // where the opponent's king could move somewhere before first pawn queens we
948 // consider only free paths to queen for both pawns.
949 else if ( !(squares_in_front_of(WHITE, pawnToGo[WHITE]) & pos.occupied_squares())
950 && !(squares_in_front_of(BLACK, pawnToGo[BLACK]) & pos.occupied_squares()))
952 assert(movesToGo[loserSide] - movesToGo[winnerSide] == 1);
954 Square winnerQSq = relative_square(winnerSide, make_square(square_file(pawnToGo[winnerSide]), RANK_8));
955 Square loserQSq = relative_square(loserSide, make_square(square_file(pawnToGo[loserSide]), RANK_8));
957 Bitboard b = pos.occupied_squares();
958 clear_bit(&b, pawnToGo[winnerSide]);
959 clear_bit(&b, pawnToGo[loserSide]);
960 b = queen_attacks_bb(winnerQSq, b);
962 if ( (b & pos.pieces(KING, loserSide))
963 ||(bit_is_set(b, loserQSq) && !bit_is_set(ei.attacked_by(loserSide), loserQSq)))
964 ei.value += Sign[winnerSide] * make_score(0, UnstoppablePawnValue - Value(0x40 * (movesToGo[winnerSide]/2)));
970 // evaluate_trapped_bishop_a7h7() determines whether a bishop on a7/h7
971 // (a2/h2 for black) is trapped by enemy pawns, and assigns a penalty
974 void evaluate_trapped_bishop_a7h7(const Position& pos, Square s, Color us, EvalInfo &ei) {
976 assert(square_is_ok(s));
977 assert(pos.piece_on(s) == piece_of_color_and_type(us, BISHOP));
979 Square b6 = relative_square(us, (square_file(s) == FILE_A) ? SQ_B6 : SQ_G6);
980 Square b8 = relative_square(us, (square_file(s) == FILE_A) ? SQ_B8 : SQ_G8);
982 if ( pos.piece_on(b6) == piece_of_color_and_type(opposite_color(us), PAWN)
983 && pos.see(s, b6) < 0
984 && pos.see(s, b8) < 0)
986 ei.value -= Sign[us] * TrappedBishopA7H7Penalty;
991 // evaluate_trapped_bishop_a1h1() determines whether a bishop on a1/h1
992 // (a8/h8 for black) is trapped by a friendly pawn on b2/g2 (b7/g7 for
993 // black), and assigns a penalty if it is. This pattern can obviously
994 // only occur in Chess960 games.
996 void evaluate_trapped_bishop_a1h1(const Position& pos, Square s, Color us, EvalInfo& ei) {
998 Piece pawn = piece_of_color_and_type(us, PAWN);
1002 assert(square_is_ok(s));
1003 assert(pos.piece_on(s) == piece_of_color_and_type(us, BISHOP));
1005 if (square_file(s) == FILE_A)
1007 b2 = relative_square(us, SQ_B2);
1008 b3 = relative_square(us, SQ_B3);
1009 c3 = relative_square(us, SQ_C3);
1013 b2 = relative_square(us, SQ_G2);
1014 b3 = relative_square(us, SQ_G3);
1015 c3 = relative_square(us, SQ_F3);
1018 if (pos.piece_on(b2) == pawn)
1022 if (!pos.square_is_empty(b3))
1023 penalty = 2 * TrappedBishopA1H1Penalty;
1024 else if (pos.piece_on(c3) == pawn)
1025 penalty = TrappedBishopA1H1Penalty;
1027 penalty = TrappedBishopA1H1Penalty / 2;
1029 ei.value -= Sign[us] * penalty;
1034 // evaluate_space() computes the space evaluation for a given side. The
1035 // space evaluation is a simple bonus based on the number of safe squares
1036 // available for minor pieces on the central four files on ranks 2--4. Safe
1037 // squares one, two or three squares behind a friendly pawn are counted
1038 // twice. Finally, the space bonus is scaled by a weight taken from the
1039 // material hash table.
1040 template<Color Us, bool HasPopCnt>
1041 int evaluate_space(const Position& pos, EvalInfo& ei) {
1043 const Color Them = (Us == WHITE ? BLACK : WHITE);
1045 // Find the safe squares for our pieces inside the area defined by
1046 // SpaceMask[us]. A square is unsafe if it is attacked by an enemy
1047 // pawn, or if it is undefended and attacked by an enemy piece.
1048 Bitboard safe = SpaceMask[Us]
1049 & ~pos.pieces(PAWN, Us)
1050 & ~ei.attacked_by(Them, PAWN)
1051 & (ei.attacked_by(Us) | ~ei.attacked_by(Them));
1053 // Find all squares which are at most three squares behind some friendly pawn
1054 Bitboard behind = pos.pieces(PAWN, Us);
1055 behind |= (Us == WHITE ? behind >> 8 : behind << 8);
1056 behind |= (Us == WHITE ? behind >> 16 : behind << 16);
1058 return count_1s_max_15<HasPopCnt>(safe) + count_1s_max_15<HasPopCnt>(behind & safe);
1062 // apply_weight() applies an evaluation weight to a value trying to prevent overflow
1064 inline Score apply_weight(Score v, Score w) {
1065 return make_score((int(mg_value(v)) * mg_value(w)) / 0x100, (int(eg_value(v)) * eg_value(w)) / 0x100);
1069 // scale_by_game_phase() interpolates between a middle game and an endgame
1070 // score, based on game phase. It also scales the return value by a
1071 // ScaleFactor array.
1073 Value scale_by_game_phase(const Score& v, Phase ph, const ScaleFactor sf[]) {
1075 assert(mg_value(v) > -VALUE_INFINITE && mg_value(v) < VALUE_INFINITE);
1076 assert(eg_value(v) > -VALUE_INFINITE && eg_value(v) < VALUE_INFINITE);
1077 assert(ph >= PHASE_ENDGAME && ph <= PHASE_MIDGAME);
1079 Value ev = apply_scale_factor(eg_value(v), sf[(eg_value(v) > Value(0) ? WHITE : BLACK)]);
1081 int result = (mg_value(v) * ph + ev * (128 - ph)) / 128;
1082 return Value(result & ~(GrainSize - 1));
1086 // weight_option() computes the value of an evaluation weight, by combining
1087 // two UCI-configurable weights (midgame and endgame) with an internal weight.
1089 Score weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight) {
1091 // Scale option value from 100 to 256
1092 int mg = get_option_value_int(mgOpt) * 256 / 100;
1093 int eg = get_option_value_int(egOpt) * 256 / 100;
1095 return apply_weight(make_score(mg, eg), internalWeight);
1098 // init_safety() initizes the king safety evaluation, based on UCI
1099 // parameters. It is called from read_weights().
1101 void init_safety() {
1103 const Value MaxSlope = Value(30);
1104 const Value Peak = Value(1280);
1107 // First setup the base table
1108 for (int i = 0; i < 100; i++)
1110 t[i] = Value(int(0.4 * i * i));
1113 t[i] = Min(t[i], t[i - 1] + MaxSlope);
1115 t[i] = Min(t[i], Peak);
1118 // Then apply the weights and get the final KingDangerTable[] array
1119 for (Color c = WHITE; c <= BLACK; c++)
1120 for (int i = 0; i < 100; i++)
1121 KingDangerTable[c][i] = apply_weight(make_score(t[i], 0), Weights[KingDangerUs + c]);