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/>.
33 #include "ucioption.h"
37 //// Local definitions
42 const int Sign[2] = { 1, -1 };
44 // Evaluation grain size, must be a power of 2
45 const int GrainSize = 8;
47 // Evaluation weights, initialized from UCI options
48 enum { Mobility, PawnStructure, PassedPawns, Space, KingDangerUs, KingDangerThem };
52 #define S(mg, eg) make_score(mg, eg)
54 // Internal evaluation weights. These are applied on top of the evaluation
55 // weights read from UCI parameters. The purpose is to be able to change
56 // the evaluation weights while keeping the default values of the UCI
57 // parameters at 100, which looks prettier.
59 // Values modified by Joona Kiiski
60 const Score WeightsInternal[] = {
61 S(248, 271), S(233, 201), S(252, 259), S(46, 0), S(247, 0), S(259, 0)
64 // Knight mobility bonus in middle game and endgame, indexed by the number
65 // of attacked squares not occupied by friendly piecess.
66 const Score KnightMobilityBonus[16] = {
67 S(-38,-33), S(-25,-23), S(-12,-13), S( 0,-3),
68 S( 12, 7), S( 25, 17), S( 31, 22), S(38, 27), S(38, 27)
71 // Bishop mobility bonus in middle game and endgame, indexed by the number
72 // of attacked squares not occupied by friendly pieces. X-ray attacks through
73 // queens are also included.
74 const Score BishopMobilityBonus[16] = {
75 S(-25,-30), S(-11,-16), S( 3, -2), S(17, 12),
76 S( 31, 26), S( 45, 40), S(57, 52), S(65, 60),
77 S( 71, 65), S( 74, 69), S(76, 71), S(78, 73),
78 S( 79, 74), S( 80, 75), S(81, 76), S(81, 76)
81 // Rook mobility bonus in middle game and endgame, indexed by the number
82 // of attacked squares not occupied by friendly pieces. X-ray attacks through
83 // queens and rooks are also included.
84 const Score RookMobilityBonus[16] = {
85 S(-20,-36), S(-14,-19), S(-8, -3), S(-2, 13),
86 S( 4, 29), S( 10, 46), S(14, 62), S(19, 79),
87 S( 23, 95), S( 26,106), S(27,111), S(28,114),
88 S( 29,116), S( 30,117), S(31,118), S(32,118)
91 // Queen mobility bonus in middle game and endgame, indexed by the number
92 // of attacked squares not occupied by friendly pieces.
93 const Score QueenMobilityBonus[32] = {
94 S(-10,-18), S(-8,-13), S(-6, -7), S(-3, -2), S(-1, 3), S( 1, 8),
95 S( 3, 13), S( 5, 19), S( 8, 23), S(10, 27), S(12, 32), S(15, 34),
96 S( 16, 35), S(17, 35), S(18, 35), S(20, 35), S(20, 35), S(20, 35),
97 S( 20, 35), S(20, 35), S(20, 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),
102 // Pointers table to access mobility tables through piece type
103 const Score* MobilityBonus[8] = { 0, 0, KnightMobilityBonus, BishopMobilityBonus,
104 RookMobilityBonus, QueenMobilityBonus, 0, 0 };
106 // Outpost bonuses for knights and bishops, indexed by square (from white's
108 const Value KnightOutpostBonus[64] = {
110 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 1
111 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 2
112 V(0), V(0), V(4), V(8), V(8), V(4), V(0), V(0), // 3
113 V(0), V(4),V(17),V(26),V(26),V(17), V(4), V(0), // 4
114 V(0), V(8),V(26),V(35),V(35),V(26), V(8), V(0), // 5
115 V(0), V(4),V(17),V(17),V(17),V(17), V(4), V(0), // 6
116 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 7
117 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0) // 8
120 const Value BishopOutpostBonus[64] = {
122 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 1
123 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 2
124 V(0), V(0), V(5), V(5), V(5), V(5), V(0), V(0), // 3
125 V(0), V(5),V(10),V(10),V(10),V(10), V(5), V(0), // 4
126 V(0),V(10),V(21),V(21),V(21),V(21),V(10), V(0), // 5
127 V(0), V(5), V(8), V(8), V(8), V(8), V(5), V(0), // 6
128 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 7
129 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0) // 8
132 // ThreatBonus[attacking][attacked] contains bonus according to which
133 // piece type attacks which one.
134 const Score ThreatBonus[8][8] = {
136 { S(0, 0), S( 7, 39), S( 0, 0), S(24, 49), S(41,100), S(41,100) }, // KNIGHT
137 { S(0, 0), S( 7, 39), S(24, 49), S( 0, 0), S(41,100), S(41,100) }, // BISHOP
138 { S(0, 0), S(-1, 29), S(15, 49), S(15, 49), S( 0, 0), S(24, 49) }, // ROOK
139 { S(0, 0), S(15, 39), S(15, 39), S(15, 39), S(15, 39), S( 0, 0) } // QUEEN
142 // ThreatedByPawnPenalty[] contains a penalty according to which piece
143 // type is attacked by an enemy pawn.
144 const Score ThreatedByPawnPenalty[8] = {
145 S(0, 0), S(0, 0), S(56, 70), S(56, 70), S(76, 99), S(86, 118)
150 // Rooks and queens on the 7th rank (modified by Joona Kiiski)
151 const Score RookOn7thBonus = make_score(47, 98);
152 const Score QueenOn7thBonus = make_score(27, 54);
154 // Rooks on open files (modified by Joona Kiiski)
155 const Score RookOpenFileBonus = make_score(43, 43);
156 const Score RookHalfOpenFileBonus = make_score(19, 19);
158 // Penalty for rooks trapped inside a friendly king which has lost the
160 const Value TrappedRookPenalty = Value(180);
162 // Penalty for a bishop on a7/h7 (a2/h2 for black) which is trapped by
164 const Score TrappedBishopA7H7Penalty = make_score(300, 300);
166 // Bitboard masks for detecting trapped bishops on a7/h7 (a2/h2 for black)
167 const Bitboard MaskA7H7[2] = {
168 ((1ULL << SQ_A7) | (1ULL << SQ_H7)),
169 ((1ULL << SQ_A2) | (1ULL << SQ_H2))
172 // Penalty for a bishop on a1/h1 (a8/h8 for black) which is trapped by
173 // a friendly pawn on b2/g2 (b7/g7 for black). This can obviously only
174 // happen in Chess960 games.
175 const Score TrappedBishopA1H1Penalty = make_score(100, 100);
177 // Bitboard masks for detecting trapped bishops on a1/h1 (a8/h8 for black)
178 const Bitboard MaskA1H1[2] = {
179 ((1ULL << SQ_A1) | (1ULL << SQ_H1)),
180 ((1ULL << SQ_A8) | (1ULL << SQ_H8))
183 // The SpaceMask[color] contains the area of the board which is considered
184 // by the space evaluation. In the middle game, each side is given a bonus
185 // based on how many squares inside this area are safe and available for
186 // friendly minor pieces.
187 const Bitboard SpaceMask[2] = {
188 (1ULL<<SQ_C2) | (1ULL<<SQ_D2) | (1ULL<<SQ_E2) | (1ULL<<SQ_F2) |
189 (1ULL<<SQ_C3) | (1ULL<<SQ_D3) | (1ULL<<SQ_E3) | (1ULL<<SQ_F3) |
190 (1ULL<<SQ_C4) | (1ULL<<SQ_D4) | (1ULL<<SQ_E4) | (1ULL<<SQ_F4),
191 (1ULL<<SQ_C7) | (1ULL<<SQ_D7) | (1ULL<<SQ_E7) | (1ULL<<SQ_F7) |
192 (1ULL<<SQ_C6) | (1ULL<<SQ_D6) | (1ULL<<SQ_E6) | (1ULL<<SQ_F6) |
193 (1ULL<<SQ_C5) | (1ULL<<SQ_D5) | (1ULL<<SQ_E5) | (1ULL<<SQ_F5)
196 /// King danger constants and variables. The king danger scores are taken
197 /// from the KingDangerTable[]. Various little "meta-bonuses" measuring
198 /// the strength of the enemy attack are added up into an integer, which
199 /// is used as an index to KingDangerTable[].
201 // KingAttackWeights[] contains king attack weights by piece type
202 const int KingAttackWeights[8] = { 0, 0, 2, 2, 3, 5 };
204 // Bonuses for enemy's safe checks
205 const int QueenContactCheckBonus = 3;
206 const int QueenCheckBonus = 2;
207 const int RookCheckBonus = 1;
208 const int BishopCheckBonus = 1;
209 const int KnightCheckBonus = 1;
211 // InitKingDanger[] contains bonuses based on the position of the defending
213 const int InitKingDanger[64] = {
214 2, 0, 2, 5, 5, 2, 0, 2,
215 2, 2, 4, 8, 8, 4, 2, 2,
216 7, 10, 12, 12, 12, 12, 10, 7,
217 15, 15, 15, 15, 15, 15, 15, 15,
218 15, 15, 15, 15, 15, 15, 15, 15,
219 15, 15, 15, 15, 15, 15, 15, 15,
220 15, 15, 15, 15, 15, 15, 15, 15,
221 15, 15, 15, 15, 15, 15, 15, 15
224 // KingDangerTable[color][] contains the actual king danger weighted scores
225 Score KingDangerTable[2][128];
227 // Pawn and material hash tables, indexed by the current thread id.
228 // Note that they will be initialized at 0 being global variables.
229 MaterialInfoTable* MaterialTable[MAX_THREADS];
230 PawnInfoTable* PawnTable[MAX_THREADS];
232 // Sizes of pawn and material hash tables
233 const int PawnTableSize = 16384;
234 const int MaterialTableSize = 1024;
236 // Function prototypes
237 template<bool HasPopCnt>
238 Value do_evaluate(const Position& pos, EvalInfo& ei);
240 template<Color Us, bool HasPopCnt>
241 void init_attack_tables(const Position& pos, EvalInfo& ei);
243 template<Color Us, bool HasPopCnt>
244 void evaluate_pieces_of_color(const Position& pos, EvalInfo& ei);
246 template<Color Us, bool HasPopCnt>
247 void evaluate_king(const Position& pos, EvalInfo& ei);
250 void evaluate_threats(const Position& pos, EvalInfo& ei);
252 template<Color Us, bool HasPopCnt>
253 int evaluate_space(const Position& pos, EvalInfo& ei);
256 void evaluate_passed_pawns(const Position& pos, EvalInfo& ei);
258 void evaluate_trapped_bishop_a7h7(const Position& pos, Square s, Color us, EvalInfo& ei);
259 void evaluate_trapped_bishop_a1h1(const Position& pos, Square s, Color us, EvalInfo& ei);
260 inline Score apply_weight(Score v, Score weight);
261 Value scale_by_game_phase(const Score& v, Phase ph, const ScaleFactor sf[]);
262 Score weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight);
271 /// evaluate() is the main evaluation function. It always computes two
272 /// values, an endgame score and a middle game score, and interpolates
273 /// between them based on the remaining material.
274 Value evaluate(const Position& pos, EvalInfo& ei) {
276 return CpuHasPOPCNT ? do_evaluate<true>(pos, ei)
277 : do_evaluate<false>(pos, ei);
282 template<bool HasPopCnt>
283 Value do_evaluate(const Position& pos, EvalInfo& ei) {
285 ScaleFactor factor[2];
288 assert(pos.thread() >= 0 && pos.thread() < MAX_THREADS);
289 assert(!pos.is_check());
291 memset(&ei, 0, sizeof(EvalInfo));
293 // Initialize by reading the incrementally updated scores included in the
294 // position object (material + piece square tables)
295 ei.value = pos.value();
297 // Probe the material hash table
298 ei.mi = MaterialTable[pos.thread()]->get_material_info(pos);
299 ei.value += ei.mi->material_value();
301 // If we have a specialized evaluation function for the current material
302 // configuration, call it and return
303 if (ei.mi->specialized_eval_exists())
304 return ei.mi->evaluate(pos);
306 // After get_material_info() call that modifies them
307 factor[WHITE] = ei.mi->scale_factor(pos, WHITE);
308 factor[BLACK] = ei.mi->scale_factor(pos, BLACK);
310 // Probe the pawn hash table
311 ei.pi = PawnTable[pos.thread()]->get_pawn_info(pos);
312 ei.value += apply_weight(ei.pi->pawns_value(), Weights[PawnStructure]);
314 // Initialize attack bitboards with pawns evaluation
315 init_attack_tables<WHITE, HasPopCnt>(pos, ei);
316 init_attack_tables<BLACK, HasPopCnt>(pos, ei);
319 evaluate_pieces_of_color<WHITE, HasPopCnt>(pos, ei);
320 evaluate_pieces_of_color<BLACK, HasPopCnt>(pos, ei);
322 // Kings. Kings are evaluated after all other pieces for both sides,
323 // because we need complete attack information for all pieces when computing
324 // the king safety evaluation.
325 evaluate_king<WHITE, HasPopCnt>(pos, ei);
326 evaluate_king<BLACK, HasPopCnt>(pos, ei);
328 // Evaluate tactical threats, we need full attack info including king
329 evaluate_threats<WHITE>(pos, ei);
330 evaluate_threats<BLACK>(pos, ei);
332 // Evaluate passed pawns, we need full attack info including king
333 evaluate_passed_pawns<WHITE>(pos, ei);
334 evaluate_passed_pawns<BLACK>(pos, ei);
336 Phase phase = ei.mi->game_phase();
338 // Middle-game specific evaluation terms
339 if (phase > PHASE_ENDGAME)
341 // Pawn storms in positions with opposite castling
342 if ( square_file(pos.king_square(WHITE)) >= FILE_E
343 && square_file(pos.king_square(BLACK)) <= FILE_D)
345 ei.value += make_score(ei.pi->queenside_storm_value(WHITE) - ei.pi->kingside_storm_value(BLACK), 0);
347 else if ( square_file(pos.king_square(WHITE)) <= FILE_D
348 && square_file(pos.king_square(BLACK)) >= FILE_E)
350 ei.value += make_score(ei.pi->kingside_storm_value(WHITE) - ei.pi->queenside_storm_value(BLACK), 0);
352 // Evaluate space for both sides
353 if (ei.mi->space_weight() > 0)
355 int s = evaluate_space<WHITE, HasPopCnt>(pos, ei) - evaluate_space<BLACK, HasPopCnt>(pos, ei);
356 ei.value += apply_weight(make_score(s * ei.mi->space_weight(), 0), Weights[Space]);
361 ei.value += apply_weight(ei.mobility, Weights[Mobility]);
363 // If we don't already have an unusual scale factor, check for opposite
364 // colored bishop endgames, and use a lower scale for those
365 if ( phase < PHASE_MIDGAME
366 && pos.opposite_colored_bishops()
367 && ( (factor[WHITE] == SCALE_FACTOR_NORMAL && eg_value(ei.value) > VALUE_ZERO)
368 || (factor[BLACK] == SCALE_FACTOR_NORMAL && eg_value(ei.value) < VALUE_ZERO)))
372 // Only the two bishops ?
373 if ( pos.non_pawn_material(WHITE) == BishopValueMidgame
374 && pos.non_pawn_material(BLACK) == BishopValueMidgame)
376 // Check for KBP vs KB with only a single pawn that is almost
377 // certainly a draw or at least two pawns.
378 bool one_pawn = (pos.piece_count(WHITE, PAWN) + pos.piece_count(BLACK, PAWN) == 1);
379 sf = one_pawn ? ScaleFactor(8) : ScaleFactor(32);
382 // Endgame with opposite-colored bishops, but also other pieces. Still
383 // a bit drawish, but not as drawish as with only the two bishops.
384 sf = ScaleFactor(50);
386 if (factor[WHITE] == SCALE_FACTOR_NORMAL)
388 if (factor[BLACK] == SCALE_FACTOR_NORMAL)
392 // Interpolate between the middle game and the endgame score
393 return Sign[pos.side_to_move()] * scale_by_game_phase(ei.value, phase, factor);
398 /// init_eval() initializes various tables used by the evaluation function
400 void init_eval(int threads) {
402 assert(threads <= MAX_THREADS);
404 for (int i = 0; i < MAX_THREADS; i++)
409 delete MaterialTable[i];
411 MaterialTable[i] = NULL;
415 PawnTable[i] = new PawnInfoTable(PawnTableSize);
416 if (!MaterialTable[i])
417 MaterialTable[i] = new MaterialInfoTable(MaterialTableSize);
422 /// quit_eval() releases heap-allocated memory at program termination
426 for (int i = 0; i < MAX_THREADS; i++)
429 delete MaterialTable[i];
431 MaterialTable[i] = NULL;
436 /// read_weights() reads evaluation weights from the corresponding UCI parameters
438 void read_weights(Color us) {
440 // King safety is asymmetrical. Our king danger level is weighted by
441 // "Cowardice" UCI parameter, instead the opponent one by "Aggressiveness".
442 const int kingDangerUs = (us == WHITE ? KingDangerUs : KingDangerThem);
443 const int kingDangerThem = (us == WHITE ? KingDangerThem : KingDangerUs);
445 Weights[Mobility] = weight_option("Mobility (Middle Game)", "Mobility (Endgame)", WeightsInternal[Mobility]);
446 Weights[PawnStructure] = weight_option("Pawn Structure (Middle Game)", "Pawn Structure (Endgame)", WeightsInternal[PawnStructure]);
447 Weights[PassedPawns] = weight_option("Passed Pawns (Middle Game)", "Passed Pawns (Endgame)", WeightsInternal[PassedPawns]);
448 Weights[Space] = weight_option("Space", "Space", WeightsInternal[Space]);
449 Weights[kingDangerUs] = weight_option("Cowardice", "Cowardice", WeightsInternal[KingDangerUs]);
450 Weights[kingDangerThem] = weight_option("Aggressiveness", "Aggressiveness", WeightsInternal[KingDangerThem]);
452 // If running in analysis mode, make sure we use symmetrical king safety. We do this
453 // by replacing both Weights[kingDangerUs] and Weights[kingDangerThem] by their average.
454 if (get_option_value_bool("UCI_AnalyseMode"))
455 Weights[kingDangerUs] = Weights[kingDangerThem] = (Weights[kingDangerUs] + Weights[kingDangerThem]) / 2;
463 // init_attack_tables() initializes king bitboards for both sides adding
464 // pawn attacks. To be done before other evaluations.
466 template<Color Us, bool HasPopCnt>
467 void init_attack_tables(const Position& pos, EvalInfo& ei) {
469 const Color Them = (Us == WHITE ? BLACK : WHITE);
471 Bitboard b = ei.attackedBy[Them][KING] = pos.attacks_from<KING>(pos.king_square(Them));
472 ei.kingZone[Us] = (b | (Us == WHITE ? b >> 8 : b << 8));
473 ei.attackedBy[Us][PAWN] = ei.pi->pawn_attacks(Us);
474 b &= ei.attackedBy[Us][PAWN];
476 ei.kingAttackersCount[Us] = count_1s_max_15<HasPopCnt>(b) / 2;
480 // evaluate_outposts() evaluates bishop and knight outposts squares
482 template<PieceType Piece, Color Us>
483 void evaluate_outposts(const Position& pos, EvalInfo& ei, Square s) {
485 const Color Them = (Us == WHITE ? BLACK : WHITE);
487 // Initial bonus based on square
488 Value bonus = (Piece == BISHOP ? BishopOutpostBonus[relative_square(Us, s)]
489 : KnightOutpostBonus[relative_square(Us, s)]);
491 // Increase bonus if supported by pawn, especially if the opponent has
492 // no minor piece which can exchange the outpost piece
493 if (bonus && bit_is_set(ei.attackedBy[Us][PAWN], s))
495 if ( pos.pieces(KNIGHT, Them) == EmptyBoardBB
496 && (SquaresByColorBB[square_color(s)] & pos.pieces(BISHOP, Them)) == EmptyBoardBB)
497 bonus += bonus + bonus / 2;
501 ei.value += Sign[Us] * make_score(bonus, bonus);
505 // evaluate_pieces<>() assigns bonuses and penalties to the pieces of a given color
507 template<PieceType Piece, Color Us, bool HasPopCnt>
508 void evaluate_pieces(const Position& pos, EvalInfo& ei, Bitboard no_mob_area) {
515 const Color Them = (Us == WHITE ? BLACK : WHITE);
516 const Square* ptr = pos.piece_list_begin(Us, Piece);
518 while ((s = *ptr++) != SQ_NONE)
520 // Find attacked squares, including x-ray attacks for bishops and rooks
521 if (Piece == KNIGHT || Piece == QUEEN)
522 b = pos.attacks_from<Piece>(s);
523 else if (Piece == BISHOP)
524 b = bishop_attacks_bb(s, pos.occupied_squares() & ~pos.pieces(QUEEN, Us));
525 else if (Piece == ROOK)
526 b = rook_attacks_bb(s, pos.occupied_squares() & ~pos.pieces(ROOK, QUEEN, Us));
530 // Update attack info
531 ei.attackedBy[Us][Piece] |= b;
534 if (b & ei.kingZone[Us])
536 ei.kingAttackersCount[Us]++;
537 ei.kingAttackersWeight[Us] += KingAttackWeights[Piece];
538 Bitboard bb = (b & ei.attackedBy[Them][KING]);
540 ei.kingAdjacentZoneAttacksCount[Us] += count_1s_max_15<HasPopCnt>(bb);
544 mob = (Piece != QUEEN ? count_1s_max_15<HasPopCnt>(b & no_mob_area)
545 : count_1s<HasPopCnt>(b & no_mob_area));
547 ei.mobility += Sign[Us] * MobilityBonus[Piece][mob];
549 // Decrease score if we are attacked by an enemy pawn. Remaining part
550 // of threat evaluation must be done later when we have full attack info.
551 if (bit_is_set(ei.attackedBy[Them][PAWN], s))
552 ei.value -= Sign[Us] * ThreatedByPawnPenalty[Piece];
554 // Bishop and knight outposts squares
555 if ((Piece == BISHOP || Piece == KNIGHT) && pos.square_is_weak(s, Us))
556 evaluate_outposts<Piece, Us>(pos, ei, s);
558 // Special patterns: trapped bishops on a7/h7/a2/h2
559 // and trapped bishops on a1/h1/a8/h8 in Chess960.
562 if (bit_is_set(MaskA7H7[Us], s))
563 evaluate_trapped_bishop_a7h7(pos, s, Us, ei);
565 if (Chess960 && bit_is_set(MaskA1H1[Us], s))
566 evaluate_trapped_bishop_a1h1(pos, s, Us, ei);
569 // Queen or rook on 7th rank
570 if ( (Piece == ROOK || Piece == QUEEN)
571 && relative_rank(Us, s) == RANK_7
572 && relative_rank(Us, pos.king_square(Them)) == RANK_8)
574 ei.value += Sign[Us] * (Piece == ROOK ? RookOn7thBonus : QueenOn7thBonus);
577 // Special extra evaluation for rooks
580 // Open and half-open files
582 if (ei.pi->file_is_half_open(Us, f))
584 if (ei.pi->file_is_half_open(Them, f))
585 ei.value += Sign[Us] * RookOpenFileBonus;
587 ei.value += Sign[Us] * RookHalfOpenFileBonus;
590 // Penalize rooks which are trapped inside a king. Penalize more if
591 // king has lost right to castle.
592 if (mob > 6 || ei.pi->file_is_half_open(Us, f))
595 ksq = pos.king_square(Us);
597 if ( square_file(ksq) >= FILE_E
598 && square_file(s) > square_file(ksq)
599 && (relative_rank(Us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
601 // Is there a half-open file between the king and the edge of the board?
602 if (!ei.pi->has_open_file_to_right(Us, square_file(ksq)))
603 ei.value -= Sign[Us] * make_score(pos.can_castle(Us) ? (TrappedRookPenalty - mob * 16) / 2
604 : (TrappedRookPenalty - mob * 16), 0);
606 else if ( square_file(ksq) <= FILE_D
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_left(Us, square_file(ksq)))
612 ei.value -= Sign[Us] * make_score(pos.can_castle(Us) ? (TrappedRookPenalty - mob * 16) / 2
613 : (TrappedRookPenalty - mob * 16), 0);
620 // evaluate_threats<>() assigns bonuses according to the type of attacking piece
621 // and the type of attacked one.
624 void evaluate_threats(const Position& pos, EvalInfo& ei) {
626 const Color Them = (Us == WHITE ? BLACK : WHITE);
629 Score bonus = SCORE_ZERO;
631 // Enemy pieces not defended by a pawn and under our attack
632 Bitboard weakEnemies = pos.pieces_of_color(Them)
633 & ~ei.attackedBy[Them][PAWN]
634 & ei.attackedBy[Us][0];
638 // Add bonus according to type of attacked enemy pieces and to the
639 // type of attacking piece, from knights to queens. Kings are not
640 // considered because are already special handled in king evaluation.
641 for (PieceType pt1 = KNIGHT; pt1 < KING; pt1++)
643 b = ei.attackedBy[Us][pt1] & weakEnemies;
645 for (PieceType pt2 = PAWN; pt2 < KING; pt2++)
646 if (b & pos.pieces(pt2))
647 bonus += ThreatBonus[pt1][pt2];
649 ei.value += Sign[Us] * bonus;
653 // evaluate_pieces_of_color<>() assigns bonuses and penalties to all the
654 // pieces of a given color.
656 template<Color Us, bool HasPopCnt>
657 void evaluate_pieces_of_color(const Position& pos, EvalInfo& ei) {
659 const Color Them = (Us == WHITE ? BLACK : WHITE);
661 // Do not include in mobility squares protected by enemy pawns or occupied by our pieces
662 const Bitboard no_mob_area = ~(ei.attackedBy[Them][PAWN] | pos.pieces_of_color(Us));
664 evaluate_pieces<KNIGHT, Us, HasPopCnt>(pos, ei, no_mob_area);
665 evaluate_pieces<BISHOP, Us, HasPopCnt>(pos, ei, no_mob_area);
666 evaluate_pieces<ROOK, Us, HasPopCnt>(pos, ei, no_mob_area);
667 evaluate_pieces<QUEEN, Us, HasPopCnt>(pos, ei, no_mob_area);
669 // Sum up all attacked squares
670 ei.attackedBy[Us][0] = ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
671 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
672 | ei.attackedBy[Us][QUEEN] | ei.attackedBy[Us][KING];
676 // evaluate_king<>() assigns bonuses and penalties to a king of a given color
678 template<Color Us, bool HasPopCnt>
679 void evaluate_king(const Position& pos, EvalInfo& ei) {
681 const Color Them = (Us == WHITE ? BLACK : WHITE);
683 Bitboard undefended, b, b1, b2, safe;
685 int attackUnits, shelter = 0;
686 const Square ksq = pos.king_square(Us);
689 if (relative_rank(Us, ksq) <= RANK_4)
691 shelter = ei.pi->get_king_shelter(pos, Us, ksq);
692 ei.value += Sign[Us] * make_score(shelter, 0);
695 // King safety. This is quite complicated, and is almost certainly far
696 // from optimally tuned.
697 if ( pos.piece_count(Them, QUEEN) >= 1
698 && ei.kingAttackersCount[Them] >= 2
699 && pos.non_pawn_material(Them) >= QueenValueMidgame + RookValueMidgame
700 && ei.kingAdjacentZoneAttacksCount[Them])
702 // Is it the attackers turn to move?
703 sente = (Them == pos.side_to_move());
705 // Find the attacked squares around the king which has no defenders
706 // apart from the king itself
707 undefended = ei.attacked_by(Them) & ei.attacked_by(Us, KING);
708 undefended &= ~( ei.attacked_by(Us, PAWN) | ei.attacked_by(Us, KNIGHT)
709 | ei.attacked_by(Us, BISHOP) | ei.attacked_by(Us, ROOK)
710 | ei.attacked_by(Us, QUEEN));
712 // Initialize the 'attackUnits' variable, which is used later on as an
713 // index to the KingDangerTable[] array. The initial value is based on
714 // the number and types of the enemy's attacking pieces, the number of
715 // attacked and undefended squares around our king, the square of the
716 // king, and the quality of the pawn shelter.
717 attackUnits = Min(25, (ei.kingAttackersCount[Them] * ei.kingAttackersWeight[Them]) / 2)
718 + 3 * (ei.kingAdjacentZoneAttacksCount[Them] + count_1s_max_15<HasPopCnt>(undefended))
719 + InitKingDanger[relative_square(Us, ksq)]
722 // Analyse enemy's safe queen contact checks. First find undefended
723 // squares around the king attacked by enemy queen...
724 b = undefended & ei.attacked_by(Them, QUEEN) & ~pos.pieces_of_color(Them);
727 // ...then remove squares not supported by another enemy piece
728 b &= ( ei.attacked_by(Them, PAWN) | ei.attacked_by(Them, KNIGHT)
729 | ei.attacked_by(Them, BISHOP) | ei.attacked_by(Them, ROOK));
731 attackUnits += QueenContactCheckBonus * count_1s_max_15<HasPopCnt>(b) * (sente ? 2 : 1);
734 // Analyse enemy's safe distance checks for sliders and knights
735 safe = ~(pos.pieces_of_color(Them) | ei.attacked_by(Us));
737 b1 = pos.attacks_from<ROOK>(ksq) & safe;
738 b2 = pos.attacks_from<BISHOP>(ksq) & safe;
740 // Enemy queen safe checks
741 b = (b1 | b2) & ei.attacked_by(Them, QUEEN);
743 attackUnits += QueenCheckBonus * count_1s_max_15<HasPopCnt>(b);
745 // Enemy rooks safe checks
746 b = b1 & ei.attacked_by(Them, ROOK);
748 attackUnits += RookCheckBonus * count_1s_max_15<HasPopCnt>(b);
750 // Enemy bishops safe checks
751 b = b2 & ei.attacked_by(Them, BISHOP);
753 attackUnits += BishopCheckBonus * count_1s_max_15<HasPopCnt>(b);
755 // Enemy knights safe checks
756 b = pos.attacks_from<KNIGHT>(ksq) & ei.attacked_by(Them, KNIGHT) & safe;
758 attackUnits += KnightCheckBonus * count_1s_max_15<HasPopCnt>(b);
760 // To index KingDangerTable[] attackUnits must be in [0, 99] range
761 attackUnits = Min(99, Max(0, attackUnits));
763 // Finally, extract the king danger score from the KingDangerTable[]
764 // array and subtract the score from evaluation. Set also ei.kingDanger[]
765 // value that will be used for pruning because this value can sometimes
766 // be very big, and so capturing a single attacking piece can therefore
767 // result in a score change far bigger than the value of the captured piece.
768 ei.value -= Sign[Us] * KingDangerTable[Us][attackUnits];
769 ei.kingDanger[Us] = mg_value(KingDangerTable[Us][attackUnits]);
774 // evaluate_passed_pawns<>() evaluates the passed pawns of the given color
777 void evaluate_passed_pawns(const Position& pos, EvalInfo& ei) {
779 const Color Them = (Us == WHITE ? BLACK : WHITE);
781 Bitboard squaresToQueen, defendedSquares, unsafeSquares, supportingPawns;
782 Bitboard b = ei.pi->passed_pawns() & pos.pieces_of_color(Us);
786 Square s = pop_1st_bit(&b);
788 assert(pos.pawn_is_passed(Us, s));
790 int r = int(relative_rank(Us, s) - RANK_2);
791 int tr = r * (r - 1);
793 // Base bonus based on rank
794 Value mbonus = Value(20 * tr);
795 Value ebonus = Value(10 + r * r * 10);
799 Square blockSq = s + pawn_push(Us);
801 // Adjust bonus based on kings proximity
802 ebonus -= Value(square_distance(pos.king_square(Us), blockSq) * 3 * tr);
803 ebonus -= Value(square_distance(pos.king_square(Us), blockSq + pawn_push(Us)) * 1 * tr);
804 ebonus += Value(square_distance(pos.king_square(Them), blockSq) * 6 * tr);
806 // If the pawn is free to advance, increase bonus
807 if (pos.square_is_empty(blockSq))
809 squaresToQueen = squares_in_front_of(Us, s);
810 defendedSquares = squaresToQueen & ei.attacked_by(Us);
812 // If there is an enemy rook or queen attacking the pawn from behind,
813 // add all X-ray attacks by the rook or queen. Otherwise consider only
814 // the squares in the pawn's path attacked or occupied by the enemy.
815 if ( (squares_behind(Us, s) & pos.pieces(ROOK, QUEEN, Them))
816 && (squares_behind(Us, s) & pos.pieces(ROOK, QUEEN, Them) & pos.attacks_from<ROOK>(s)))
817 unsafeSquares = squaresToQueen;
819 unsafeSquares = squaresToQueen & (ei.attacked_by(Them) | pos.pieces_of_color(Them));
821 // If there aren't enemy attacks or pieces along the path to queen give
822 // huge bonus. Even bigger if we protect the pawn's path.
824 ebonus += Value(tr * (squaresToQueen == defendedSquares ? 17 : 15));
826 // OK, there are enemy attacks or pieces (but not pawns). Are those
827 // squares which are attacked by the enemy also attacked by us ?
828 // If yes, big bonus (but smaller than when there are no enemy attacks),
829 // if no, somewhat smaller bonus.
830 ebonus += Value(tr * ((unsafeSquares & defendedSquares) == unsafeSquares ? 13 : 8));
832 // At last, add a small bonus when there are no *friendly* pieces
833 // in the pawn's path.
834 if (!(squaresToQueen & pos.pieces_of_color(Us)))
839 // Increase the bonus if the passed pawn is supported by a friendly pawn
840 // on the same rank and a bit smaller if it's on the previous rank.
841 supportingPawns = pos.pieces(PAWN, Us) & neighboring_files_bb(s);
842 if (supportingPawns & rank_bb(s))
843 ebonus += Value(r * 20);
844 else if (supportingPawns & rank_bb(s - pawn_push(Us)))
845 ebonus += Value(r * 12);
847 // Rook pawns are a special case: They are sometimes worse, and
848 // sometimes better than other passed pawns. It is difficult to find
849 // good rules for determining whether they are good or bad. For now,
850 // we try the following: Increase the value for rook pawns if the
851 // other side has no pieces apart from a knight, and decrease the
852 // value if the other side has a rook or queen.
853 if (square_file(s) == FILE_A || square_file(s) == FILE_H)
855 if (pos.non_pawn_material(Them) <= KnightValueMidgame)
856 ebonus += ebonus / 4;
857 else if (pos.pieces(ROOK, QUEEN, Them))
858 ebonus -= ebonus / 4;
861 // Add the scores for this pawn to the middle game and endgame eval
862 ei.value += Sign[Us] * apply_weight(make_score(mbonus, ebonus), Weights[PassedPawns]);
868 // evaluate_trapped_bishop_a7h7() determines whether a bishop on a7/h7
869 // (a2/h2 for black) is trapped by enemy pawns, and assigns a penalty
872 void evaluate_trapped_bishop_a7h7(const Position& pos, Square s, Color us, EvalInfo &ei) {
874 assert(square_is_ok(s));
875 assert(pos.piece_on(s) == piece_of_color_and_type(us, BISHOP));
877 Square b6 = relative_square(us, (square_file(s) == FILE_A) ? SQ_B6 : SQ_G6);
878 Square b8 = relative_square(us, (square_file(s) == FILE_A) ? SQ_B8 : SQ_G8);
880 if ( pos.piece_on(b6) == piece_of_color_and_type(opposite_color(us), PAWN)
881 && pos.see(s, b6) < 0
882 && pos.see(s, b8) < 0)
884 ei.value -= Sign[us] * TrappedBishopA7H7Penalty;
889 // evaluate_trapped_bishop_a1h1() determines whether a bishop on a1/h1
890 // (a8/h8 for black) is trapped by a friendly pawn on b2/g2 (b7/g7 for
891 // black), and assigns a penalty if it is. This pattern can obviously
892 // only occur in Chess960 games.
894 void evaluate_trapped_bishop_a1h1(const Position& pos, Square s, Color us, EvalInfo& ei) {
896 Piece pawn = piece_of_color_and_type(us, PAWN);
900 assert(square_is_ok(s));
901 assert(pos.piece_on(s) == piece_of_color_and_type(us, BISHOP));
903 if (square_file(s) == FILE_A)
905 b2 = relative_square(us, SQ_B2);
906 b3 = relative_square(us, SQ_B3);
907 c3 = relative_square(us, SQ_C3);
911 b2 = relative_square(us, SQ_G2);
912 b3 = relative_square(us, SQ_G3);
913 c3 = relative_square(us, SQ_F3);
916 if (pos.piece_on(b2) == pawn)
920 if (!pos.square_is_empty(b3))
921 penalty = 2 * TrappedBishopA1H1Penalty;
922 else if (pos.piece_on(c3) == pawn)
923 penalty = TrappedBishopA1H1Penalty;
925 penalty = TrappedBishopA1H1Penalty / 2;
927 ei.value -= Sign[us] * penalty;
932 // evaluate_space() computes the space evaluation for a given side. The
933 // space evaluation is a simple bonus based on the number of safe squares
934 // available for minor pieces on the central four files on ranks 2--4. Safe
935 // squares one, two or three squares behind a friendly pawn are counted
936 // twice. Finally, the space bonus is scaled by a weight taken from the
937 // material hash table.
938 template<Color Us, bool HasPopCnt>
939 int evaluate_space(const Position& pos, EvalInfo& ei) {
941 const Color Them = (Us == WHITE ? BLACK : WHITE);
943 // Find the safe squares for our pieces inside the area defined by
944 // SpaceMask[us]. A square is unsafe if it is attacked by an enemy
945 // pawn, or if it is undefended and attacked by an enemy piece.
946 Bitboard safe = SpaceMask[Us]
947 & ~pos.pieces(PAWN, Us)
948 & ~ei.attacked_by(Them, PAWN)
949 & (ei.attacked_by(Us) | ~ei.attacked_by(Them));
951 // Find all squares which are at most three squares behind some friendly pawn
952 Bitboard behind = pos.pieces(PAWN, Us);
953 behind |= (Us == WHITE ? behind >> 8 : behind << 8);
954 behind |= (Us == WHITE ? behind >> 16 : behind << 16);
956 return count_1s_max_15<HasPopCnt>(safe) + count_1s_max_15<HasPopCnt>(behind & safe);
960 // apply_weight() applies an evaluation weight to a value trying to prevent overflow
962 inline Score apply_weight(Score v, Score w) {
963 return make_score((int(mg_value(v)) * mg_value(w)) / 0x100, (int(eg_value(v)) * eg_value(w)) / 0x100);
967 // scale_by_game_phase() interpolates between a middle game and an endgame score,
968 // based on game phase. It also scales the return value by a ScaleFactor array.
970 Value scale_by_game_phase(const Score& v, Phase ph, const ScaleFactor sf[]) {
972 assert(mg_value(v) > -VALUE_INFINITE && mg_value(v) < VALUE_INFINITE);
973 assert(eg_value(v) > -VALUE_INFINITE && eg_value(v) < VALUE_INFINITE);
974 assert(ph >= PHASE_ENDGAME && ph <= PHASE_MIDGAME);
976 Value eg = eg_value(v);
977 ScaleFactor f = sf[eg > VALUE_ZERO ? WHITE : BLACK];
978 Value ev = Value((eg * int(f)) / SCALE_FACTOR_NORMAL);
980 int result = (mg_value(v) * int(ph) + ev * int(128 - ph)) / 128;
981 return Value(result & ~(GrainSize - 1));
985 // weight_option() computes the value of an evaluation weight, by combining
986 // two UCI-configurable weights (midgame and endgame) with an internal weight.
988 Score weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight) {
990 // Scale option value from 100 to 256
991 int mg = get_option_value_int(mgOpt) * 256 / 100;
992 int eg = get_option_value_int(egOpt) * 256 / 100;
994 return apply_weight(make_score(mg, eg), internalWeight);
997 // init_safety() initizes the king safety evaluation, based on UCI
998 // parameters. It is called from read_weights().
1000 void init_safety() {
1002 const Value MaxSlope = Value(30);
1003 const Value Peak = Value(1280);
1006 // First setup the base table
1007 for (int i = 0; i < 100; i++)
1009 t[i] = Value(int(0.4 * i * i));
1012 t[i] = Min(t[i], t[i - 1] + MaxSlope);
1014 t[i] = Min(t[i], Peak);
1017 // Then apply the weights and get the final KingDangerTable[] array
1018 for (Color c = WHITE; c <= BLACK; c++)
1019 for (int i = 0; i < 100; i++)
1020 KingDangerTable[c][i] = apply_weight(make_score(t[i], 0), Weights[KingDangerUs + c]);