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(18,37), S( 0, 0), S(37,47), S(55,97), S(55,97) }, // KNIGHT
138 { S(0, 0), S(18,37), S(37,47), S( 0, 0), S(55,97), S(55,97) }, // BISHOP
139 { S(0, 0), S( 9,27), S(27,47), S(27,47), S( 0, 0), S(37,47) }, // ROOK
140 { S(0, 0), S(27,37), S(27,37), S(27,37), S(27,37), S( 0, 0) }, // QUEEN
144 // ThreatedByPawnPenalty[] contains a penalty according to which piece
145 // type is attacked by an enemy pawn.
146 const Score ThreatedByPawnPenalty[8] = {
147 S(0, 0), S(0, 0), S(56, 70), S(56, 70), S(76, 99), S(86, 118)
152 // Bonus for unstoppable passed pawns
153 const Value UnstoppablePawnValue = Value(0x500);
155 // Rooks and queens on the 7th rank (modified by Joona Kiiski)
156 const Score RookOn7thBonus = make_score(47, 98);
157 const Score QueenOn7thBonus = make_score(27, 54);
159 // Rooks on open files (modified by Joona Kiiski)
160 const Score RookOpenFileBonus = make_score(43, 43);
161 const Score RookHalfOpenFileBonus = make_score(19, 19);
163 // Penalty for rooks trapped inside a friendly king which has lost the
165 const Value TrappedRookPenalty = Value(180);
167 // Penalty for a bishop on a7/h7 (a2/h2 for black) which is trapped by
169 const Score TrappedBishopA7H7Penalty = make_score(300, 300);
171 // Bitboard masks for detecting trapped bishops on a7/h7 (a2/h2 for black)
172 const Bitboard MaskA7H7[2] = {
173 ((1ULL << SQ_A7) | (1ULL << SQ_H7)),
174 ((1ULL << SQ_A2) | (1ULL << SQ_H2))
177 // Penalty for a bishop on a1/h1 (a8/h8 for black) which is trapped by
178 // a friendly pawn on b2/g2 (b7/g7 for black). This can obviously only
179 // happen in Chess960 games.
180 const Score TrappedBishopA1H1Penalty = make_score(100, 100);
182 // Bitboard masks for detecting trapped bishops on a1/h1 (a8/h8 for black)
183 const Bitboard MaskA1H1[2] = {
184 ((1ULL << SQ_A1) | (1ULL << SQ_H1)),
185 ((1ULL << SQ_A8) | (1ULL << SQ_H8))
188 // The SpaceMask[color] contains the area of the board which is considered
189 // by the space evaluation. In the middle game, each side is given a bonus
190 // based on how many squares inside this area are safe and available for
191 // friendly minor pieces.
192 const Bitboard SpaceMask[2] = {
193 (1ULL<<SQ_C2) | (1ULL<<SQ_D2) | (1ULL<<SQ_E2) | (1ULL<<SQ_F2) |
194 (1ULL<<SQ_C3) | (1ULL<<SQ_D3) | (1ULL<<SQ_E3) | (1ULL<<SQ_F3) |
195 (1ULL<<SQ_C4) | (1ULL<<SQ_D4) | (1ULL<<SQ_E4) | (1ULL<<SQ_F4),
196 (1ULL<<SQ_C7) | (1ULL<<SQ_D7) | (1ULL<<SQ_E7) | (1ULL<<SQ_F7) |
197 (1ULL<<SQ_C6) | (1ULL<<SQ_D6) | (1ULL<<SQ_E6) | (1ULL<<SQ_F6) |
198 (1ULL<<SQ_C5) | (1ULL<<SQ_D5) | (1ULL<<SQ_E5) | (1ULL<<SQ_F5)
201 /// King danger constants and variables. The king danger scores are taken
202 /// from the KingDangerTable[]. Various little "meta-bonuses" measuring
203 /// the strength of the enemy attack are added up into an integer, which
204 /// is used as an index to KingDangerTable[].
206 // KingAttackWeights[] contains king attack weights by piece type
207 const int KingAttackWeights[8] = { 0, 0, 2, 2, 3, 5 };
209 // Bonuses for enemy's safe checks
210 const int QueenContactCheckBonus = 3;
211 const int DiscoveredCheckBonus = 3;
212 const int QueenCheckBonus = 2;
213 const int RookCheckBonus = 1;
214 const int BishopCheckBonus = 1;
215 const int KnightCheckBonus = 1;
217 // InitKingDanger[] contains bonuses based on the position of the defending
219 const int InitKingDanger[64] = {
220 2, 0, 2, 5, 5, 2, 0, 2,
221 2, 2, 4, 8, 8, 4, 2, 2,
222 7, 10, 12, 12, 12, 12, 10, 7,
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,
227 15, 15, 15, 15, 15, 15, 15, 15
230 // KingDangerTable[color][] contains the actual king danger weighted scores
231 Score KingDangerTable[2][128];
233 // Pawn and material hash tables, indexed by the current thread id.
234 // Note that they will be initialized at 0 being global variables.
235 MaterialInfoTable* MaterialTable[MAX_THREADS];
236 PawnInfoTable* PawnTable[MAX_THREADS];
238 // Sizes of pawn and material hash tables
239 const int PawnTableSize = 16384;
240 const int MaterialTableSize = 1024;
242 // Function prototypes
243 template<bool HasPopCnt>
244 Value do_evaluate(const Position& pos, EvalInfo& ei, int threadID);
246 template<Color Us, bool HasPopCnt>
247 void evaluate_pieces_of_color(const Position& pos, EvalInfo& ei);
249 template<Color Us, bool HasPopCnt>
250 void evaluate_king(const Position& pos, EvalInfo& ei);
253 void evaluate_threats(const Position& pos, EvalInfo& ei);
255 template<Color Us, bool HasPopCnt>
256 void evaluate_space(const Position& pos, EvalInfo& ei);
259 void evaluate_passed_pawns(const Position& pos, EvalInfo& ei);
261 void evaluate_unstoppable_pawns(const Position& pos, EvalInfo& ei);
262 void evaluate_trapped_bishop_a7h7(const Position& pos, Square s, Color us, EvalInfo& ei);
263 void evaluate_trapped_bishop_a1h1(const Position& pos, Square s, Color us, EvalInfo& ei);
264 inline Score apply_weight(Score v, Score weight);
265 Value scale_by_game_phase(const Score& v, Phase ph, const ScaleFactor sf[]);
266 Score weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight);
275 /// evaluate() is the main evaluation function. It always computes two
276 /// values, an endgame score and a middle game score, and interpolates
277 /// between them based on the remaining material.
278 Value evaluate(const Position& pos, EvalInfo& ei, int threadID) {
280 return CpuHasPOPCNT ? do_evaluate<true>(pos, ei, threadID)
281 : do_evaluate<false>(pos, ei, threadID);
286 template<bool HasPopCnt>
287 Value do_evaluate(const Position& pos, EvalInfo& ei, int threadID) {
290 ScaleFactor factor[2];
293 assert(threadID >= 0 && threadID < 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[threadID]->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[threadID]->get_pawn_info(pos);
317 ei.value += apply_weight(ei.pi->pawns_value(), Weights[PawnStructure]);
319 // Initialize king attack bitboards and king attack zones for both sides
320 ei.attackedBy[WHITE][KING] = pos.attacks_from<KING>(pos.king_square(WHITE));
321 ei.attackedBy[BLACK][KING] = pos.attacks_from<KING>(pos.king_square(BLACK));
322 ei.kingZone[WHITE] = ei.attackedBy[BLACK][KING] | (ei.attackedBy[BLACK][KING] >> 8);
323 ei.kingZone[BLACK] = ei.attackedBy[WHITE][KING] | (ei.attackedBy[WHITE][KING] << 8);
325 // Initialize pawn attack bitboards for both sides
326 ei.attackedBy[WHITE][PAWN] = ei.pi->pawn_attacks(WHITE);
327 b = ei.attackedBy[WHITE][PAWN] & ei.attackedBy[BLACK][KING];
329 ei.kingAttackersCount[WHITE] = count_1s_max_15<HasPopCnt>(b)/2;
331 ei.attackedBy[BLACK][PAWN] = ei.pi->pawn_attacks(BLACK);
332 b = ei.attackedBy[BLACK][PAWN] & ei.attackedBy[WHITE][KING];
334 ei.kingAttackersCount[BLACK] = count_1s_max_15<HasPopCnt>(b)/2;
337 evaluate_pieces_of_color<WHITE, HasPopCnt>(pos, ei);
338 evaluate_pieces_of_color<BLACK, HasPopCnt>(pos, ei);
340 // Kings. Kings are evaluated after all other pieces for both sides,
341 // because we need complete attack information for all pieces when computing
342 // the king safety evaluation.
343 evaluate_king<WHITE, HasPopCnt>(pos, ei);
344 evaluate_king<BLACK, HasPopCnt>(pos, ei);
346 // Evaluate tactical threats, we need full attack info including king
347 evaluate_threats<WHITE>(pos, ei);
348 evaluate_threats<BLACK>(pos, ei);
350 // Evaluate passed pawns, we need full attack info including king
351 evaluate_passed_pawns<WHITE>(pos, ei);
352 evaluate_passed_pawns<BLACK>(pos, ei);
354 // If one side has only a king, check whether exsists any unstoppable passed pawn
355 if (!pos.non_pawn_material(WHITE) || !pos.non_pawn_material(BLACK))
356 evaluate_unstoppable_pawns(pos, ei);
358 Phase phase = ei.mi->game_phase();
360 // Middle-game specific evaluation terms
361 if (phase > PHASE_ENDGAME)
363 // Pawn storms in positions with opposite castling
364 if ( square_file(pos.king_square(WHITE)) >= FILE_E
365 && square_file(pos.king_square(BLACK)) <= FILE_D)
367 ei.value += make_score(ei.pi->queenside_storm_value(WHITE) - ei.pi->kingside_storm_value(BLACK), 0);
369 else if ( square_file(pos.king_square(WHITE)) <= FILE_D
370 && square_file(pos.king_square(BLACK)) >= FILE_E)
372 ei.value += make_score(ei.pi->kingside_storm_value(WHITE) - ei.pi->queenside_storm_value(BLACK), 0);
374 // Evaluate space for both sides
375 if (ei.mi->space_weight() > 0)
377 evaluate_space<WHITE, HasPopCnt>(pos, ei);
378 evaluate_space<BLACK, HasPopCnt>(pos, ei);
383 ei.value += apply_weight(ei.mobility, Weights[Mobility]);
385 // If we don't already have an unusual scale factor, check for opposite
386 // colored bishop endgames, and use a lower scale for those
387 if ( phase < PHASE_MIDGAME
388 && pos.opposite_colored_bishops()
389 && ( (factor[WHITE] == SCALE_FACTOR_NORMAL && eg_value(ei.value) > Value(0))
390 || (factor[BLACK] == SCALE_FACTOR_NORMAL && eg_value(ei.value) < Value(0))))
394 // Only the two bishops ?
395 if ( pos.non_pawn_material(WHITE) == BishopValueMidgame
396 && pos.non_pawn_material(BLACK) == BishopValueMidgame)
398 // Check for KBP vs KB with only a single pawn that is almost
399 // certainly a draw or at least two pawns.
400 bool one_pawn = (pos.piece_count(WHITE, PAWN) + pos.piece_count(BLACK, PAWN) == 1);
401 sf = one_pawn ? ScaleFactor(8) : ScaleFactor(32);
404 // Endgame with opposite-colored bishops, but also other pieces. Still
405 // a bit drawish, but not as drawish as with only the two bishops.
406 sf = ScaleFactor(50);
408 if (factor[WHITE] == SCALE_FACTOR_NORMAL)
410 if (factor[BLACK] == SCALE_FACTOR_NORMAL)
414 // Interpolate between the middle game and the endgame score
415 return Sign[pos.side_to_move()] * scale_by_game_phase(ei.value, phase, factor);
420 /// init_eval() initializes various tables used by the evaluation function
422 void init_eval(int threads) {
424 assert(threads <= MAX_THREADS);
426 for (int i = 0; i < MAX_THREADS; i++)
431 delete MaterialTable[i];
433 MaterialTable[i] = NULL;
437 PawnTable[i] = new PawnInfoTable(PawnTableSize);
438 if (!MaterialTable[i])
439 MaterialTable[i] = new MaterialInfoTable(MaterialTableSize);
444 /// quit_eval() releases heap-allocated memory at program termination
448 for (int i = 0; i < MAX_THREADS; i++)
451 delete MaterialTable[i];
453 MaterialTable[i] = NULL;
458 /// read_weights() reads evaluation weights from the corresponding UCI parameters
460 void read_weights(Color us) {
462 // King safety is asymmetrical. Our king danger level is weighted by
463 // "Cowardice" UCI parameter, instead the opponent one by "Aggressiveness".
464 const int kingDangerUs = (us == WHITE ? KingDangerUs : KingDangerThem);
465 const int kingDangerThem = (us == WHITE ? KingDangerThem : KingDangerUs);
467 Weights[Mobility] = weight_option("Mobility (Middle Game)", "Mobility (Endgame)", WeightsInternal[Mobility]);
468 Weights[PawnStructure] = weight_option("Pawn Structure (Middle Game)", "Pawn Structure (Endgame)", WeightsInternal[PawnStructure]);
469 Weights[PassedPawns] = weight_option("Passed Pawns (Middle Game)", "Passed Pawns (Endgame)", WeightsInternal[PassedPawns]);
470 Weights[Space] = weight_option("Space", "Space", WeightsInternal[Space]);
471 Weights[kingDangerUs] = weight_option("Cowardice", "Cowardice", WeightsInternal[KingDangerUs]);
472 Weights[kingDangerThem] = weight_option("Aggressiveness", "Aggressiveness", WeightsInternal[KingDangerThem]);
474 // If running in analysis mode, make sure we use symmetrical king safety. We do this
475 // by replacing both Weights[kingDangerUs] and Weights[kingDangerThem] by their average.
476 if (get_option_value_bool("UCI_AnalyseMode"))
477 Weights[kingDangerUs] = Weights[kingDangerThem] = (Weights[kingDangerUs] + Weights[kingDangerThem]) / 2;
485 // evaluate_outposts() evaluates bishop and knight outposts squares
487 template<PieceType Piece, Color Us>
488 void evaluate_outposts(const Position& pos, EvalInfo& ei, Square s) {
490 const Color Them = (Us == WHITE ? BLACK : WHITE);
492 // Initial bonus based on square
493 Value bonus = (Piece == BISHOP ? BishopOutpostBonus[relative_square(Us, s)]
494 : KnightOutpostBonus[relative_square(Us, s)]);
496 // Increase bonus if supported by pawn, especially if the opponent has
497 // no minor piece which can exchange the outpost piece
498 if (bonus && bit_is_set(ei.attackedBy[Us][PAWN], s))
500 if ( pos.pieces(KNIGHT, Them) == EmptyBoardBB
501 && (SquaresByColorBB[square_color(s)] & pos.pieces(BISHOP, Them)) == EmptyBoardBB)
502 bonus += bonus + bonus / 2;
506 ei.value += Sign[Us] * make_score(bonus, bonus);
510 // evaluate_pieces<>() assigns bonuses and penalties to the pieces of a given color
512 template<PieceType Piece, Color Us, bool HasPopCnt>
513 void evaluate_pieces(const Position& pos, EvalInfo& ei, Bitboard no_mob_area) {
520 const Color Them = (Us == WHITE ? BLACK : WHITE);
521 const Square* ptr = pos.piece_list_begin(Us, Piece);
523 while ((s = *ptr++) != SQ_NONE)
525 // Find attacked squares, including x-ray attacks for bishops and rooks
526 if (Piece == KNIGHT || Piece == QUEEN)
527 b = pos.attacks_from<Piece>(s);
528 else if (Piece == BISHOP)
529 b = bishop_attacks_bb(s, pos.occupied_squares() & ~pos.pieces(QUEEN, Us));
530 else if (Piece == ROOK)
531 b = rook_attacks_bb(s, pos.occupied_squares() & ~pos.pieces(ROOK, QUEEN, Us));
535 // Update attack info
536 ei.attackedBy[Us][Piece] |= b;
539 if (b & ei.kingZone[Us])
541 ei.kingAttackersCount[Us]++;
542 ei.kingAttackersWeight[Us] += KingAttackWeights[Piece];
543 Bitboard bb = (b & ei.attackedBy[Them][KING]);
545 ei.kingAdjacentZoneAttacksCount[Us] += count_1s_max_15<HasPopCnt>(bb);
549 mob = (Piece != QUEEN ? count_1s_max_15<HasPopCnt>(b & no_mob_area)
550 : count_1s<HasPopCnt>(b & no_mob_area));
552 ei.mobility += Sign[Us] * MobilityBonus[Piece][mob];
554 // Decrease score if we are attacked by an enemy pawn. Remaining part
555 // of threat evaluation must be done later when we have full attack info.
556 if (bit_is_set(ei.attackedBy[Them][PAWN], s))
557 ei.value -= Sign[Us] * ThreatedByPawnPenalty[Piece];
559 // Bishop and knight outposts squares
560 if ((Piece == BISHOP || Piece == KNIGHT) && pos.square_is_weak(s, Them))
561 evaluate_outposts<Piece, Us>(pos, ei, s);
563 // Special patterns: trapped bishops on a7/h7/a2/h2
564 // and trapped bishops on a1/h1/a8/h8 in Chess960.
567 if (bit_is_set(MaskA7H7[Us], s))
568 evaluate_trapped_bishop_a7h7(pos, s, Us, ei);
570 if (Chess960 && bit_is_set(MaskA1H1[Us], s))
571 evaluate_trapped_bishop_a1h1(pos, s, Us, ei);
574 // Queen or rook on 7th rank
575 if ( (Piece == ROOK || Piece == QUEEN)
576 && relative_rank(Us, s) == RANK_7
577 && relative_rank(Us, pos.king_square(Them)) == RANK_8)
579 ei.value += Sign[Us] * (Piece == ROOK ? RookOn7thBonus : QueenOn7thBonus);
582 // Special extra evaluation for rooks
585 // Open and half-open files
587 if (ei.pi->file_is_half_open(Us, f))
589 if (ei.pi->file_is_half_open(Them, f))
590 ei.value += Sign[Us] * RookOpenFileBonus;
592 ei.value += Sign[Us] * RookHalfOpenFileBonus;
595 // Penalize rooks which are trapped inside a king. Penalize more if
596 // king has lost right to castle.
597 if (mob > 6 || ei.pi->file_is_half_open(Us, f))
600 ksq = pos.king_square(Us);
602 if ( square_file(ksq) >= FILE_E
603 && square_file(s) > square_file(ksq)
604 && (relative_rank(Us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
606 // Is there a half-open file between the king and the edge of the board?
607 if (!ei.pi->has_open_file_to_right(Us, square_file(ksq)))
608 ei.value -= Sign[Us] * make_score(pos.can_castle(Us) ? (TrappedRookPenalty - mob * 16) / 2
609 : (TrappedRookPenalty - mob * 16), 0);
611 else if ( square_file(ksq) <= FILE_D
612 && square_file(s) < square_file(ksq)
613 && (relative_rank(Us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
615 // Is there a half-open file between the king and the edge of the board?
616 if (!ei.pi->has_open_file_to_left(Us, square_file(ksq)))
617 ei.value -= Sign[Us] * make_score(pos.can_castle(Us) ? (TrappedRookPenalty - mob * 16) / 2
618 : (TrappedRookPenalty - mob * 16), 0);
625 // evaluate_threats<>() assigns bonuses according to the type of attacking piece
626 // and the type of attacked one.
629 void evaluate_threats(const Position& pos, EvalInfo& ei) {
631 const Color Them = (Us == WHITE ? BLACK : WHITE);
634 Score bonus = make_score(0, 0);
636 // Enemy pieces not defended by a pawn and under our attack
637 Bitboard weakEnemies = pos.pieces_of_color(Them)
638 & ~ei.attackedBy[Them][PAWN]
639 & ei.attackedBy[Us][0];
643 // Add bonus according to type of attacked enemy pieces and to the
644 // type of attacking piece, from knights to queens. Kings are not
645 // considered because are already special handled in king evaluation.
646 for (PieceType pt1 = KNIGHT; pt1 < KING; pt1++)
648 b = ei.attackedBy[Us][pt1] & weakEnemies;
650 for (PieceType pt2 = PAWN; pt2 < KING; pt2++)
651 if (b & pos.pieces(pt2))
652 bonus += ThreatBonus[pt1][pt2];
654 ei.value += Sign[Us] * bonus;
658 // evaluate_pieces_of_color<>() assigns bonuses and penalties to all the
659 // pieces of a given color.
661 template<Color Us, bool HasPopCnt>
662 void evaluate_pieces_of_color(const Position& pos, EvalInfo& ei) {
664 const Color Them = (Us == WHITE ? BLACK : WHITE);
666 // Do not include in mobility squares protected by enemy pawns or occupied by our pieces
667 const Bitboard no_mob_area = ~(ei.attackedBy[Them][PAWN] | pos.pieces_of_color(Us));
669 evaluate_pieces<KNIGHT, Us, HasPopCnt>(pos, ei, no_mob_area);
670 evaluate_pieces<BISHOP, Us, HasPopCnt>(pos, ei, no_mob_area);
671 evaluate_pieces<ROOK, Us, HasPopCnt>(pos, ei, no_mob_area);
672 evaluate_pieces<QUEEN, Us, HasPopCnt>(pos, ei, no_mob_area);
674 // Sum up all attacked squares
675 ei.attackedBy[Us][0] = ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
676 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
677 | ei.attackedBy[Us][QUEEN] | ei.attackedBy[Us][KING];
681 // evaluate_king<>() assigns bonuses and penalties to a king of a given color
683 template<Color Us, bool HasPopCnt>
684 void evaluate_king(const Position& pos, EvalInfo& ei) {
686 const Color Them = (Us == WHITE ? BLACK : WHITE);
688 Bitboard undefended, b, b1, b2, safe;
690 int attackUnits, shelter = 0;
691 const Square ksq = pos.king_square(Us);
694 if (relative_rank(Us, ksq) <= RANK_4)
696 shelter = ei.pi->get_king_shelter(pos, Us, ksq);
697 ei.value += Sign[Us] * make_score(shelter, 0);
700 // King safety. This is quite complicated, and is almost certainly far
701 // from optimally tuned.
702 if ( pos.piece_count(Them, QUEEN) >= 1
703 && ei.kingAttackersCount[Them] >= 2
704 && pos.non_pawn_material(Them) >= QueenValueMidgame + RookValueMidgame
705 && ei.kingAdjacentZoneAttacksCount[Them])
707 // Is it the attackers turn to move?
708 sente = (Them == pos.side_to_move());
710 // Find the attacked squares around the king which has no defenders
711 // apart from the king itself
712 undefended = ei.attacked_by(Them) & ei.attacked_by(Us, KING);
713 undefended &= ~( ei.attacked_by(Us, PAWN) | ei.attacked_by(Us, KNIGHT)
714 | ei.attacked_by(Us, BISHOP) | ei.attacked_by(Us, ROOK)
715 | ei.attacked_by(Us, QUEEN));
717 // Initialize the 'attackUnits' variable, which is used later on as an
718 // index to the KingDangerTable[] array. The initial value is based on
719 // the number and types of the enemy's attacking pieces, the number of
720 // attacked and undefended squares around our king, the square of the
721 // king, and the quality of the pawn shelter.
722 attackUnits = Min(25, (ei.kingAttackersCount[Them] * ei.kingAttackersWeight[Them]) / 2)
723 + 3 * (ei.kingAdjacentZoneAttacksCount[Them] + count_1s_max_15<HasPopCnt>(undefended))
724 + InitKingDanger[relative_square(Us, ksq)]
727 // Analyse enemy's safe queen contact checks. First find undefended
728 // squares around the king attacked by enemy queen...
729 b = undefended & ei.attacked_by(Them, QUEEN) & ~pos.pieces_of_color(Them);
732 // ...then remove squares not supported by another enemy piece
733 b &= ( ei.attacked_by(Them, PAWN) | ei.attacked_by(Them, KNIGHT)
734 | ei.attacked_by(Them, BISHOP) | ei.attacked_by(Them, ROOK));
736 attackUnits += QueenContactCheckBonus * count_1s_max_15<HasPopCnt>(b) * (sente ? 2 : 1);
739 // Analyse enemy's safe distance checks for sliders and knights
740 safe = ~(pos.pieces_of_color(Them) | ei.attacked_by(Us));
742 b1 = pos.attacks_from<ROOK>(ksq) & safe;
743 b2 = pos.attacks_from<BISHOP>(ksq) & safe;
745 // Enemy queen safe checks
746 b = (b1 | b2) & ei.attacked_by(Them, QUEEN);
748 attackUnits += QueenCheckBonus * count_1s_max_15<HasPopCnt>(b);
750 // Enemy rooks safe checks
751 b = b1 & ei.attacked_by(Them, ROOK);
753 attackUnits += RookCheckBonus * count_1s_max_15<HasPopCnt>(b);
755 // Enemy bishops safe checks
756 b = b2 & ei.attacked_by(Them, BISHOP);
758 attackUnits += BishopCheckBonus * count_1s_max_15<HasPopCnt>(b);
760 // Enemy knights safe checks
761 b = pos.attacks_from<KNIGHT>(ksq) & ei.attacked_by(Them, KNIGHT) & safe;
763 attackUnits += KnightCheckBonus * count_1s_max_15<HasPopCnt>(b);
765 // Analyse enemy's discovered checks (only for non-pawns right now,
766 // consider adding pawns later).
767 b = pos.discovered_check_candidates(Them) & ~pos.pieces(PAWN);
769 attackUnits += DiscoveredCheckBonus * count_1s_max_15<HasPopCnt>(b) * (sente ? 2 : 1);
771 // To index KingDangerTable[] attackUnits must be in [0, 99] range
772 attackUnits = Min(99, Max(0, attackUnits));
774 // Finally, extract the king danger score from the KingDangerTable[]
775 // array and subtract the score from evaluation. Set also ei.kingDanger[]
776 // value that will be used for pruning because this value can sometimes
777 // be very big, and so capturing a single attacking piece can therefore
778 // result in a score change far bigger than the value of the captured piece.
779 ei.value -= Sign[Us] * KingDangerTable[Us][attackUnits];
780 ei.kingDanger[Us] = mg_value(KingDangerTable[Us][attackUnits]);
785 // evaluate_passed_pawns<>() evaluates the passed pawns of the given color
788 void evaluate_passed_pawns(const Position& pos, EvalInfo& ei) {
790 const Color Them = (Us == WHITE ? BLACK : WHITE);
792 Bitboard b = ei.pi->passed_pawns() & pos.pieces_of_color(Us);
796 Square s = pop_1st_bit(&b);
798 assert(pos.piece_on(s) == piece_of_color_and_type(Us, PAWN));
799 assert(pos.pawn_is_passed(Us, s));
801 int r = int(relative_rank(Us, s) - RANK_2);
802 int tr = Max(0, r * (r - 1));
804 // Base bonus based on rank
805 Value mbonus = Value(20 * tr);
806 Value ebonus = Value(10 + r * r * 10);
808 // Adjust bonus based on king proximity
811 Square blockSq = s + pawn_push(Us);
813 ebonus -= Value(square_distance(pos.king_square(Us), blockSq) * 3 * tr);
814 ebonus -= Value(square_distance(pos.king_square(Us), blockSq + pawn_push(Us)) * 1 * tr);
815 ebonus += Value(square_distance(pos.king_square(Them), blockSq) * 6 * tr);
817 // If the pawn is free to advance, increase bonus
818 if (pos.square_is_empty(blockSq))
820 // There are no enemy pawns in the pawn's path
821 Bitboard b2 = squares_in_front_of(Us, s);
823 assert((b2 & pos.pieces(PAWN, Them)) == EmptyBoardBB);
825 // Squares attacked by us
826 Bitboard b4 = b2 & ei.attacked_by(Us);
828 // Squares attacked or occupied by enemy pieces
829 Bitboard b3 = b2 & (ei.attacked_by(Them) | pos.pieces_of_color(Them));
831 // If there is an enemy rook or queen attacking the pawn from behind,
832 // add all X-ray attacks by the rook or queen.
833 if ( (squares_behind(Us, s) & pos.pieces(ROOK, QUEEN, Them))
834 && (squares_behind(Us, s) & pos.pieces(ROOK, QUEEN, Them) & pos.attacks_from<QUEEN>(s)))
837 // Are any of the squares in the pawn's path attacked or occupied by the enemy?
838 if (b3 == EmptyBoardBB)
839 // No enemy attacks or pieces, huge bonus!
840 // Even bigger if we protect the pawn's path
841 ebonus += Value(tr * (b2 == b4 ? 17 : 15));
843 // OK, there are enemy attacks or pieces (but not pawns). Are those
844 // squares which are attacked by the enemy also attacked by us ?
845 // If yes, big bonus (but smaller than when there are no enemy attacks),
846 // if no, somewhat smaller bonus.
847 ebonus += Value(tr * ((b3 & b4) == b3 ? 13 : 8));
849 // At last, add a small bonus when there are no *friendly* pieces
850 // in the pawn's path.
851 if ((b2 & pos.pieces_of_color(Us)) == EmptyBoardBB)
856 // If the pawn is supported by a friendly pawn, increase bonus
857 Bitboard b1 = pos.pieces(PAWN, Us) & neighboring_files_bb(s);
859 ebonus += Value(r * 20);
860 else if (pos.attacks_from<PAWN>(s, Them) & b1)
861 ebonus += Value(r * 12);
863 // Rook pawns are a special case: They are sometimes worse, and
864 // sometimes better than other passed pawns. It is difficult to find
865 // good rules for determining whether they are good or bad. For now,
866 // we try the following: Increase the value for rook pawns if the
867 // other side has no pieces apart from a knight, and decrease the
868 // value if the other side has a rook or queen.
869 if (square_file(s) == FILE_A || square_file(s) == FILE_H)
871 if ( pos.non_pawn_material(Them) <= KnightValueMidgame
872 && pos.piece_count(Them, KNIGHT) <= 1)
873 ebonus += ebonus / 4;
874 else if (pos.pieces(ROOK, QUEEN, Them))
875 ebonus -= ebonus / 4;
878 // Add the scores for this pawn to the middle game and endgame eval
879 ei.value += Sign[Us] * apply_weight(make_score(mbonus, ebonus), Weights[PassedPawns]);
885 // evaluate_unstoppable_pawns() evaluates the unstoppable passed pawns for both sides
887 void evaluate_unstoppable_pawns(const Position& pos, EvalInfo& ei) {
889 int movesToGo[2] = {0, 0};
890 Square pawnToGo[2] = {SQ_NONE, SQ_NONE};
892 for (Color c = WHITE; c <= BLACK; c++)
894 // Skip evaluation if other side has non-pawn pieces
895 if (pos.non_pawn_material(opposite_color(c)))
898 Bitboard b = ei.pi->passed_pawns() & pos.pieces_of_color(c);
902 Square s = pop_1st_bit(&b);
903 Square queeningSquare = relative_square(c, make_square(square_file(s), RANK_8));
904 int d = square_distance(s, queeningSquare)
905 - square_distance(pos.king_square(opposite_color(c)), queeningSquare)
906 + int(c != pos.side_to_move());
910 int mtg = RANK_8 - relative_rank(c, s);
911 int blockerCount = count_1s_max_15(squares_in_front_of(c, s) & pos.occupied_squares());
914 if (d < 0 && (!movesToGo[c] || movesToGo[c] > mtg))
923 // Neither side has an unstoppable passed pawn?
924 if (!(movesToGo[WHITE] | movesToGo[BLACK]))
927 // Does only one side have an unstoppable passed pawn?
928 if (!movesToGo[WHITE] || !movesToGo[BLACK])
930 Color winnerSide = movesToGo[WHITE] ? WHITE : BLACK;
931 ei.value += make_score(0, Sign[winnerSide] * (UnstoppablePawnValue - Value(0x40 * movesToGo[winnerSide])));
934 { // Both sides have unstoppable pawns! Try to find out who queens
935 // first. We begin by transforming 'movesToGo' to the number of
936 // plies until the pawn queens for both sides.
937 movesToGo[WHITE] *= 2;
938 movesToGo[BLACK] *= 2;
939 movesToGo[pos.side_to_move()]--;
941 Color winnerSide = movesToGo[WHITE] < movesToGo[BLACK] ? WHITE : BLACK;
942 Color loserSide = opposite_color(winnerSide);
944 // If one side queens at least three plies before the other, that side wins
945 if (movesToGo[winnerSide] <= movesToGo[loserSide] - 3)
946 ei.value += Sign[winnerSide] * make_score(0, UnstoppablePawnValue - Value(0x40 * (movesToGo[winnerSide]/2)));
948 // If one side queens one ply before the other and checks the king or attacks
949 // the undefended opponent's queening square, that side wins. To avoid cases
950 // where the opponent's king could move somewhere before first pawn queens we
951 // consider only free paths to queen for both pawns.
952 else if ( !(squares_in_front_of(WHITE, pawnToGo[WHITE]) & pos.occupied_squares())
953 && !(squares_in_front_of(BLACK, pawnToGo[BLACK]) & pos.occupied_squares()))
955 assert(movesToGo[loserSide] - movesToGo[winnerSide] == 1);
957 Square winnerQSq = relative_square(winnerSide, make_square(square_file(pawnToGo[winnerSide]), RANK_8));
958 Square loserQSq = relative_square(loserSide, make_square(square_file(pawnToGo[loserSide]), RANK_8));
960 Bitboard b = pos.occupied_squares();
961 clear_bit(&b, pawnToGo[winnerSide]);
962 clear_bit(&b, pawnToGo[loserSide]);
963 b = queen_attacks_bb(winnerQSq, b);
965 if ( (b & pos.pieces(KING, loserSide))
966 ||(bit_is_set(b, loserQSq) && !bit_is_set(ei.attacked_by(loserSide), loserQSq)))
967 ei.value += Sign[winnerSide] * make_score(0, UnstoppablePawnValue - Value(0x40 * (movesToGo[winnerSide]/2)));
973 // evaluate_trapped_bishop_a7h7() determines whether a bishop on a7/h7
974 // (a2/h2 for black) is trapped by enemy pawns, and assigns a penalty
977 void evaluate_trapped_bishop_a7h7(const Position& pos, Square s, Color us, EvalInfo &ei) {
979 assert(square_is_ok(s));
980 assert(pos.piece_on(s) == piece_of_color_and_type(us, BISHOP));
982 Square b6 = relative_square(us, (square_file(s) == FILE_A) ? SQ_B6 : SQ_G6);
983 Square b8 = relative_square(us, (square_file(s) == FILE_A) ? SQ_B8 : SQ_G8);
985 if ( pos.piece_on(b6) == piece_of_color_and_type(opposite_color(us), PAWN)
986 && pos.see(s, b6) < 0
987 && pos.see(s, b8) < 0)
989 ei.value -= Sign[us] * TrappedBishopA7H7Penalty;
994 // evaluate_trapped_bishop_a1h1() determines whether a bishop on a1/h1
995 // (a8/h8 for black) is trapped by a friendly pawn on b2/g2 (b7/g7 for
996 // black), and assigns a penalty if it is. This pattern can obviously
997 // only occur in Chess960 games.
999 void evaluate_trapped_bishop_a1h1(const Position& pos, Square s, Color us, EvalInfo& ei) {
1001 Piece pawn = piece_of_color_and_type(us, PAWN);
1005 assert(square_is_ok(s));
1006 assert(pos.piece_on(s) == piece_of_color_and_type(us, BISHOP));
1008 if (square_file(s) == FILE_A)
1010 b2 = relative_square(us, SQ_B2);
1011 b3 = relative_square(us, SQ_B3);
1012 c3 = relative_square(us, SQ_C3);
1016 b2 = relative_square(us, SQ_G2);
1017 b3 = relative_square(us, SQ_G3);
1018 c3 = relative_square(us, SQ_F3);
1021 if (pos.piece_on(b2) == pawn)
1025 if (!pos.square_is_empty(b3))
1026 penalty = 2 * TrappedBishopA1H1Penalty;
1027 else if (pos.piece_on(c3) == pawn)
1028 penalty = TrappedBishopA1H1Penalty;
1030 penalty = TrappedBishopA1H1Penalty / 2;
1032 ei.value -= Sign[us] * penalty;
1037 // evaluate_space() computes the space evaluation for a given side. The
1038 // space evaluation is a simple bonus based on the number of safe squares
1039 // available for minor pieces on the central four files on ranks 2--4. Safe
1040 // squares one, two or three squares behind a friendly pawn are counted
1041 // twice. Finally, the space bonus is scaled by a weight taken from the
1042 // material hash table.
1043 template<Color Us, bool HasPopCnt>
1044 void evaluate_space(const Position& pos, EvalInfo& ei) {
1046 const Color Them = (Us == WHITE ? BLACK : WHITE);
1048 // Find the safe squares for our pieces inside the area defined by
1049 // SpaceMask[us]. A square is unsafe if it is attacked by an enemy
1050 // pawn, or if it is undefended and attacked by an enemy piece.
1052 Bitboard safeSquares = SpaceMask[Us]
1053 & ~pos.pieces(PAWN, Us)
1054 & ~ei.attacked_by(Them, PAWN)
1055 & ~(~ei.attacked_by(Us) & ei.attacked_by(Them));
1057 // Find all squares which are at most three squares behind some friendly
1059 Bitboard behindFriendlyPawns = pos.pieces(PAWN, Us);
1060 behindFriendlyPawns |= (Us == WHITE ? behindFriendlyPawns >> 8 : behindFriendlyPawns << 8);
1061 behindFriendlyPawns |= (Us == WHITE ? behindFriendlyPawns >> 16 : behindFriendlyPawns << 16);
1063 int space = count_1s_max_15<HasPopCnt>(safeSquares)
1064 + count_1s_max_15<HasPopCnt>(behindFriendlyPawns & safeSquares);
1066 ei.value += Sign[Us] * apply_weight(make_score(space * ei.mi->space_weight(), 0), Weights[Space]);
1070 // apply_weight() applies an evaluation weight to a value trying to prevent overflow
1072 inline Score apply_weight(Score v, Score w) {
1073 return make_score((int(mg_value(v)) * mg_value(w)) / 0x100, (int(eg_value(v)) * eg_value(w)) / 0x100);
1077 // scale_by_game_phase() interpolates between a middle game and an endgame
1078 // score, based on game phase. It also scales the return value by a
1079 // ScaleFactor array.
1081 Value scale_by_game_phase(const Score& v, Phase ph, const ScaleFactor sf[]) {
1083 assert(mg_value(v) > -VALUE_INFINITE && mg_value(v) < VALUE_INFINITE);
1084 assert(eg_value(v) > -VALUE_INFINITE && eg_value(v) < VALUE_INFINITE);
1085 assert(ph >= PHASE_ENDGAME && ph <= PHASE_MIDGAME);
1087 Value ev = apply_scale_factor(eg_value(v), sf[(eg_value(v) > Value(0) ? WHITE : BLACK)]);
1089 int result = (mg_value(v) * ph + ev * (128 - ph)) / 128;
1090 return Value(result & ~(GrainSize - 1));
1094 // weight_option() computes the value of an evaluation weight, by combining
1095 // two UCI-configurable weights (midgame and endgame) with an internal weight.
1097 Score weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight) {
1099 Score uciWeight = make_score(get_option_value_int(mgOpt), get_option_value_int(egOpt));
1101 // Convert to integer to prevent overflow
1102 int mg = mg_value(uciWeight);
1103 int eg = eg_value(uciWeight);
1105 mg = (mg * 0x100) / 100;
1106 eg = (eg * 0x100) / 100;
1107 mg = (mg * mg_value(internalWeight)) / 0x100;
1108 eg = (eg * eg_value(internalWeight)) / 0x100;
1109 return make_score(mg, eg);
1112 // init_safety() initizes the king safety evaluation, based on UCI
1113 // parameters. It is called from read_weights().
1115 void init_safety() {
1123 // First setup the base table
1124 for (int i = 0; i < 100; i++)
1129 t[i] = Value((int)(a * (i - b) * (i - b)));
1132 for (int i = 1; i < 100; i++)
1134 if (t[i] - t[i - 1] > maxSlope)
1135 t[i] = t[i - 1] + Value(maxSlope);
1137 if (t[i] > Value(peak))
1141 // Then apply the weights and get the final KingDangerTable[] array
1142 for (Color c = WHITE; c <= BLACK; c++)
1143 for (int i = 0; i < 100; i++)
1144 KingDangerTable[c][i] = apply_weight(make_score(t[i], 0), Weights[KingDangerUs + c]);