2 Stockfish, a UCI chess playing engine derived from Glaurung 2.1
3 Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
4 Copyright (C) 2008-2010 Marco Costalba, Joona Kiiski, Tord Romstad
6 Stockfish is free software: you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation, either version 3 of the License, or
9 (at your option) any later version.
11 Stockfish is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
16 You should have received a copy of the GNU General Public License
17 along with this program. If not, see <http://www.gnu.org/licenses/>.
32 #include "ucioption.h"
36 //// Local definitions
41 // Struct EvalInfo contains various information computed and collected
42 // by the evaluation functions.
45 // Pointer to pawn hash table entry
48 // attackedBy[color][piece type] is a bitboard representing all squares
49 // attacked by a given color and piece type, attackedBy[color][0] contains
50 // all squares attacked by the given color.
51 Bitboard attackedBy[2][8];
53 // kingZone[color] is the zone around the enemy king which is considered
54 // by the king safety evaluation. This consists of the squares directly
55 // adjacent to the king, and the three (or two, for a king on an edge file)
56 // squares two ranks in front of the king. For instance, if black's king
57 // is on g8, kingZone[WHITE] is a bitboard containing the squares f8, h8,
58 // f7, g7, h7, f6, g6 and h6.
61 // kingAttackersCount[color] is the number of pieces of the given color
62 // which attack a square in the kingZone of the enemy king.
63 int kingAttackersCount[2];
65 // kingAttackersWeight[color] is the sum of the "weight" of the pieces of the
66 // given color which attack a square in the kingZone of the enemy king. The
67 // weights of the individual piece types are given by the variables
68 // QueenAttackWeight, RookAttackWeight, BishopAttackWeight and
69 // KnightAttackWeight in evaluate.cpp
70 int kingAttackersWeight[2];
72 // kingAdjacentZoneAttacksCount[color] is the number of attacks to squares
73 // directly adjacent to the king of the given color. Pieces which attack
74 // more than one square are counted multiple times. For instance, if black's
75 // king is on g8 and there's a white knight on g5, this knight adds
76 // 2 to kingAdjacentZoneAttacksCount[BLACK].
77 int kingAdjacentZoneAttacksCount[2];
80 // Evaluation grain size, must be a power of 2
81 const int GrainSize = 8;
83 // Evaluation weights, initialized from UCI options
84 enum { Mobility, PawnStructure, PassedPawns, Space, KingDangerUs, KingDangerThem };
88 #define S(mg, eg) make_score(mg, eg)
90 // Internal evaluation weights. These are applied on top of the evaluation
91 // weights read from UCI parameters. The purpose is to be able to change
92 // the evaluation weights while keeping the default values of the UCI
93 // parameters at 100, which looks prettier.
95 // Values modified by Joona Kiiski
96 const Score WeightsInternal[] = {
97 S(248, 271), S(233, 201), S(252, 259), S(46, 0), S(247, 0), S(259, 0)
100 // MobilityBonus[PieceType][attacked] contains mobility bonuses for middle and
101 // end game, indexed by piece type and number of attacked squares not occupied
102 // by friendly pieces.
103 const Score MobilityBonus[][32] = {
105 { S(-38,-33), S(-25,-23), S(-12,-13), S( 0, -3), S(12, 7), S(25, 17), // Knights
106 S( 31, 22), S( 38, 27), S( 38, 27) },
107 { S(-25,-30), S(-11,-16), S( 3, -2), S(17, 12), S(31, 26), S(45, 40), // Bishops
108 S( 57, 52), S( 65, 60), S( 71, 65), S(74, 69), S(76, 71), S(78, 73),
109 S( 79, 74), S( 80, 75), S( 81, 76), S(81, 76) },
110 { S(-20,-36), S(-14,-19), S( -8, -3), S(-2, 13), S( 4, 29), S(10, 46), // Rooks
111 S( 14, 62), S( 19, 79), S( 23, 95), S(26,106), S(27,111), S(28,114),
112 S( 29,116), S( 30,117), S( 31,118), S(32,118) },
113 { S(-10,-18), S( -8,-13), S( -6, -7), S(-3, -2), S(-1, 3), S( 1, 8), // Queens
114 S( 3, 13), S( 5, 19), S( 8, 23), S(10, 27), S(12, 32), S(15, 34),
115 S( 16, 35), S( 17, 35), S( 18, 35), S(20, 35), S(20, 35), S(20, 35),
116 S( 20, 35), S( 20, 35), S( 20, 35), S(20, 35), S(20, 35), S(20, 35),
117 S( 20, 35), S( 20, 35), S( 20, 35), S(20, 35), S(20, 35), S(20, 35),
118 S( 20, 35), S( 20, 35) }
121 // OutpostBonus[PieceType][Square] contains outpost bonuses of knights and
122 // bishops, indexed by piece type and square (from white's point of view).
123 const Value OutpostBonus[][64] = {
126 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // Knights
127 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0),
128 V(0), V(0), V(4), V(8), V(8), V(4), V(0), V(0),
129 V(0), V(4),V(17),V(26),V(26),V(17), V(4), V(0),
130 V(0), V(8),V(26),V(35),V(35),V(26), V(8), V(0),
131 V(0), V(4),V(17),V(17),V(17),V(17), V(4), V(0) },
133 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // Bishops
134 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0),
135 V(0), V(0), V(5), V(5), V(5), V(5), V(0), V(0),
136 V(0), V(5),V(10),V(10),V(10),V(10), V(5), V(0),
137 V(0),V(10),V(21),V(21),V(21),V(21),V(10), V(0),
138 V(0), V(5), V(8), V(8), V(8), V(8), V(5), V(0) }
141 // ThreatBonus[attacking][attacked] contains threat bonuses according to
142 // which piece type attacks which one.
143 const Score ThreatBonus[][8] = {
145 { S(0, 0), S( 7, 39), S( 0, 0), S(24, 49), S(41,100), S(41,100) }, // KNIGHT
146 { S(0, 0), S( 7, 39), S(24, 49), S( 0, 0), S(41,100), S(41,100) }, // BISHOP
147 { S(0, 0), S(-1, 29), S(15, 49), S(15, 49), S( 0, 0), S(24, 49) }, // ROOK
148 { S(0, 0), S(15, 39), S(15, 39), S(15, 39), S(15, 39), S( 0, 0) } // QUEEN
151 // ThreatedByPawnPenalty[PieceType] contains a penalty according to which
152 // piece type is attacked by an enemy pawn.
153 const Score ThreatedByPawnPenalty[] = {
154 S(0, 0), S(0, 0), S(56, 70), S(56, 70), S(76, 99), S(86, 118)
159 // Rooks and queens on the 7th rank (modified by Joona Kiiski)
160 const Score RookOn7thBonus = make_score(47, 98);
161 const Score QueenOn7thBonus = make_score(27, 54);
163 // Rooks on open files (modified by Joona Kiiski)
164 const Score RookOpenFileBonus = make_score(43, 43);
165 const Score RookHalfOpenFileBonus = make_score(19, 19);
167 // Penalty for rooks trapped inside a friendly king which has lost the
169 const Value TrappedRookPenalty = Value(180);
171 // Penalty for a bishop on a1/h1 (a8/h8 for black) which is trapped by
172 // a friendly pawn on b2/g2 (b7/g7 for black). This can obviously only
173 // happen in Chess960 games.
174 const Score TrappedBishopA1H1Penalty = make_score(100, 100);
176 // The SpaceMask[Color] contains the area of the board which is considered
177 // by the space evaluation. In the middle game, each side is given a bonus
178 // based on how many squares inside this area are safe and available for
179 // friendly minor pieces.
180 const Bitboard SpaceMask[] = {
181 (1ULL << SQ_C2) | (1ULL << SQ_D2) | (1ULL << SQ_E2) | (1ULL << SQ_F2) |
182 (1ULL << SQ_C3) | (1ULL << SQ_D3) | (1ULL << SQ_E3) | (1ULL << SQ_F3) |
183 (1ULL << SQ_C4) | (1ULL << SQ_D4) | (1ULL << SQ_E4) | (1ULL << SQ_F4),
184 (1ULL << SQ_C7) | (1ULL << SQ_D7) | (1ULL << SQ_E7) | (1ULL << SQ_F7) |
185 (1ULL << SQ_C6) | (1ULL << SQ_D6) | (1ULL << SQ_E6) | (1ULL << SQ_F6) |
186 (1ULL << SQ_C5) | (1ULL << SQ_D5) | (1ULL << SQ_E5) | (1ULL << SQ_F5)
189 // King danger constants and variables. The king danger scores are taken
190 // from the KingDangerTable[]. Various little "meta-bonuses" measuring
191 // the strength of the enemy attack are added up into an integer, which
192 // is used as an index to KingDangerTable[].
194 // KingAttackWeights[PieceType] contains king attack weights by piece type
195 const int KingAttackWeights[] = { 0, 0, 2, 2, 3, 5 };
197 // Bonuses for enemy's safe checks
198 const int QueenContactCheckBonus = 6;
199 const int RookContactCheckBonus = 4;
200 const int QueenCheckBonus = 3;
201 const int RookCheckBonus = 2;
202 const int BishopCheckBonus = 1;
203 const int KnightCheckBonus = 1;
205 // InitKingDanger[Square] contains penalties based on the position of the
206 // defending king, indexed by king's square (from white's point of view).
207 const int InitKingDanger[] = {
208 2, 0, 2, 5, 5, 2, 0, 2,
209 2, 2, 4, 8, 8, 4, 2, 2,
210 7, 10, 12, 12, 12, 12, 10, 7,
211 15, 15, 15, 15, 15, 15, 15, 15,
212 15, 15, 15, 15, 15, 15, 15, 15,
213 15, 15, 15, 15, 15, 15, 15, 15,
214 15, 15, 15, 15, 15, 15, 15, 15,
215 15, 15, 15, 15, 15, 15, 15, 15
218 // KingDangerTable[Color][attackUnits] contains the actual king danger
219 // weighted scores, indexed by color and by a calculated integer number.
220 Score KingDangerTable[2][128];
222 // Pawn and material hash tables, indexed by the current thread id.
223 // Note that they will be initialized at 0 being global variables.
224 MaterialInfoTable* MaterialTable[MAX_THREADS];
225 PawnInfoTable* PawnTable[MAX_THREADS];
227 // Function prototypes
228 template<bool HasPopCnt>
229 Value do_evaluate(const Position& pos, Value& margin);
231 template<Color Us, bool HasPopCnt>
232 void init_eval_info(const Position& pos, EvalInfo& ei);
234 template<Color Us, bool HasPopCnt>
235 Score evaluate_pieces_of_color(const Position& pos, EvalInfo& ei, Score& mobility);
237 template<Color Us, bool HasPopCnt>
238 Score evaluate_king(const Position& pos, EvalInfo& ei, Value margins[]);
241 Score evaluate_threats(const Position& pos, EvalInfo& ei);
243 template<Color Us, bool HasPopCnt>
244 int evaluate_space(const Position& pos, EvalInfo& ei);
247 Score evaluate_passed_pawns(const Position& pos, EvalInfo& ei);
249 template<bool HasPopCnt>
250 Score evaluate_unstoppable_pawns(const Position& pos, EvalInfo& ei);
252 inline Score apply_weight(Score v, Score weight);
253 Value scale_by_game_phase(const Score& v, Phase ph, ScaleFactor sf);
254 Score weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight);
264 /// Prefetches in pawn hash tables
266 void prefetchPawn(Key key, int threadID) {
268 PawnTable[threadID]->prefetch(key);
272 /// evaluate() is the main evaluation function. It always computes two
273 /// values, an endgame score and a middle game score, and interpolates
274 /// between them based on the remaining material.
275 Value evaluate(const Position& pos, Value& margin) {
277 return CpuHasPOPCNT ? do_evaluate<true>(pos, margin)
278 : do_evaluate<false>(pos, margin);
283 template<bool HasPopCnt>
284 Value do_evaluate(const Position& pos, Value& margin) {
288 Score mobilityWhite, mobilityBlack;
291 assert(pos.thread() >= 0 && pos.thread() < MAX_THREADS);
292 assert(!pos.is_check());
294 // Initialize value by reading the incrementally updated scores included
295 // in the position object (material + piece square tables).
296 Score bonus = pos.value();
298 // margins[] store the uncertainty estimation of position's evaluation
299 // that typically is used by the search for pruning decisions.
300 margins[WHITE] = margins[BLACK] = VALUE_ZERO;
302 // Probe the material hash table
303 MaterialInfo* mi = MaterialTable[pos.thread()]->get_material_info(pos);
304 bonus += mi->material_value();
306 // If we have a specialized evaluation function for the current material
307 // configuration, call it and return.
308 if (mi->specialized_eval_exists())
311 return mi->evaluate(pos);
314 // Probe the pawn hash table
315 ei.pi = PawnTable[pos.thread()]->get_pawn_info(pos);
316 bonus += apply_weight(ei.pi->pawns_value(), Weights[PawnStructure]);
318 // Initialize attack and king safety bitboards
319 init_eval_info<WHITE, HasPopCnt>(pos, ei);
320 init_eval_info<BLACK, HasPopCnt>(pos, ei);
322 // Evaluate pieces and mobility
323 bonus += evaluate_pieces_of_color<WHITE, HasPopCnt>(pos, ei, mobilityWhite)
324 - evaluate_pieces_of_color<BLACK, HasPopCnt>(pos, ei, mobilityBlack);
326 bonus += apply_weight(mobilityWhite - mobilityBlack, Weights[Mobility]);
328 // Evaluate kings after all other pieces because we need complete attack
329 // information when computing the king safety evaluation.
330 bonus += evaluate_king<WHITE, HasPopCnt>(pos, ei, margins)
331 - evaluate_king<BLACK, HasPopCnt>(pos, ei, margins);
333 // Evaluate tactical threats, we need full attack information including king
334 bonus += evaluate_threats<WHITE>(pos, ei)
335 - evaluate_threats<BLACK>(pos, ei);
337 // Evaluate passed pawns, we need full attack information including king
338 bonus += evaluate_passed_pawns<WHITE>(pos, ei)
339 - evaluate_passed_pawns<BLACK>(pos, ei);
341 // If one side has only a king, check whether exists any unstoppable passed pawn
342 if (!pos.non_pawn_material(WHITE) || !pos.non_pawn_material(BLACK))
343 bonus += evaluate_unstoppable_pawns<HasPopCnt>(pos, ei);
345 // Evaluate space for both sides, only in middle-game.
346 if (mi->space_weight())
348 int s = evaluate_space<WHITE, HasPopCnt>(pos, ei) - evaluate_space<BLACK, HasPopCnt>(pos, ei);
349 bonus += apply_weight(make_score(s * mi->space_weight(), 0), Weights[Space]);
352 // Scale winning side if position is more drawish that what it appears
353 ScaleFactor sf = eg_value(bonus) > VALUE_DRAW ? mi->scale_factor(pos, WHITE)
354 : mi->scale_factor(pos, BLACK);
355 Phase phase = mi->game_phase();
357 // If we don't already have an unusual scale factor, check for opposite
358 // colored bishop endgames, and use a lower scale for those.
359 if ( phase < PHASE_MIDGAME
360 && pos.opposite_colored_bishops()
361 && sf == SCALE_FACTOR_NORMAL)
363 // Only the two bishops ?
364 if ( pos.non_pawn_material(WHITE) == BishopValueMidgame
365 && pos.non_pawn_material(BLACK) == BishopValueMidgame)
367 // Check for KBP vs KB with only a single pawn that is almost
368 // certainly a draw or at least two pawns.
369 bool one_pawn = (pos.piece_count(WHITE, PAWN) + pos.piece_count(BLACK, PAWN) == 1);
370 sf = one_pawn ? ScaleFactor(8) : ScaleFactor(32);
373 // Endgame with opposite-colored bishops, but also other pieces. Still
374 // a bit drawish, but not as drawish as with only the two bishops.
375 sf = ScaleFactor(50);
378 // Interpolate between the middle game and the endgame score
379 margin = margins[pos.side_to_move()];
380 Value v = scale_by_game_phase(bonus, phase, sf);
381 return pos.side_to_move() == WHITE ? v : -v;
387 /// init_eval() initializes various tables used by the evaluation function
389 void init_eval(int threads) {
391 assert(threads <= MAX_THREADS);
393 for (int i = 0; i < MAX_THREADS; i++)
398 delete MaterialTable[i];
400 MaterialTable[i] = NULL;
404 PawnTable[i] = new PawnInfoTable();
406 if (!MaterialTable[i])
407 MaterialTable[i] = new MaterialInfoTable();
412 /// quit_eval() releases heap-allocated memory at program termination
420 /// read_weights() reads evaluation weights from the corresponding UCI parameters
422 void read_evaluation_uci_options(Color us) {
424 // King safety is asymmetrical. Our king danger level is weighted by
425 // "Cowardice" UCI parameter, instead the opponent one by "Aggressiveness".
426 const int kingDangerUs = (us == WHITE ? KingDangerUs : KingDangerThem);
427 const int kingDangerThem = (us == WHITE ? KingDangerThem : KingDangerUs);
429 Weights[Mobility] = weight_option("Mobility (Middle Game)", "Mobility (Endgame)", WeightsInternal[Mobility]);
430 Weights[PawnStructure] = weight_option("Pawn Structure (Middle Game)", "Pawn Structure (Endgame)", WeightsInternal[PawnStructure]);
431 Weights[PassedPawns] = weight_option("Passed Pawns (Middle Game)", "Passed Pawns (Endgame)", WeightsInternal[PassedPawns]);
432 Weights[Space] = weight_option("Space", "Space", WeightsInternal[Space]);
433 Weights[kingDangerUs] = weight_option("Cowardice", "Cowardice", WeightsInternal[KingDangerUs]);
434 Weights[kingDangerThem] = weight_option("Aggressiveness", "Aggressiveness", WeightsInternal[KingDangerThem]);
436 // If running in analysis mode, make sure we use symmetrical king safety. We do this
437 // by replacing both Weights[kingDangerUs] and Weights[kingDangerThem] by their average.
438 if (Options["UCI_AnalyseMode"].value<bool>())
439 Weights[kingDangerUs] = Weights[kingDangerThem] = (Weights[kingDangerUs] + Weights[kingDangerThem]) / 2;
447 // init_eval_info() initializes king bitboards for given color adding
448 // pawn attacks. To be done at the beginning of the evaluation.
450 template<Color Us, bool HasPopCnt>
451 void init_eval_info(const Position& pos, EvalInfo& ei) {
453 const BitCountType Max15 = HasPopCnt ? CNT_POPCNT : CpuIs64Bit ? CNT64_MAX15 : CNT32_MAX15;
454 const Color Them = (Us == WHITE ? BLACK : WHITE);
456 Bitboard b = ei.attackedBy[Them][KING] = pos.attacks_from<KING>(pos.king_square(Them));
457 ei.attackedBy[Us][PAWN] = ei.pi->pawn_attacks(Us);
459 // Init king safety tables only if we are going to use them
460 if ( pos.piece_count(Us, QUEEN)
461 && pos.non_pawn_material(Us) >= QueenValueMidgame + RookValueMidgame)
463 ei.kingZone[Us] = (b | (Us == WHITE ? b >> 8 : b << 8));
464 b &= ei.attackedBy[Us][PAWN];
465 ei.kingAttackersCount[Us] = b ? count_1s<Max15>(b) / 2 : 0;
466 ei.kingAdjacentZoneAttacksCount[Us] = ei.kingAttackersWeight[Us] = 0;
468 ei.kingZone[Us] = ei.kingAttackersCount[Us] = 0;
472 // evaluate_outposts() evaluates bishop and knight outposts squares
474 template<PieceType Piece, Color Us>
475 Score evaluate_outposts(const Position& pos, EvalInfo& ei, Square s) {
477 const Color Them = (Us == WHITE ? BLACK : WHITE);
479 assert (Piece == BISHOP || Piece == KNIGHT);
481 // Initial bonus based on square
482 Value bonus = OutpostBonus[Piece == BISHOP][relative_square(Us, s)];
484 // Increase bonus if supported by pawn, especially if the opponent has
485 // no minor piece which can exchange the outpost piece.
486 if (bonus && bit_is_set(ei.attackedBy[Us][PAWN], s))
488 if ( pos.pieces(KNIGHT, Them) == EmptyBoardBB
489 && (SquaresByColorBB[square_color(s)] & pos.pieces(BISHOP, Them)) == EmptyBoardBB)
490 bonus += bonus + bonus / 2;
494 return make_score(bonus, bonus);
498 // evaluate_pieces<>() assigns bonuses and penalties to the pieces of a given color
500 template<PieceType Piece, Color Us, bool HasPopCnt>
501 Score evaluate_pieces(const Position& pos, EvalInfo& ei, Score& mobility, Bitboard mobilityArea) {
507 Score bonus = SCORE_ZERO;
509 const BitCountType Full = HasPopCnt ? CNT_POPCNT : CpuIs64Bit ? CNT64 : CNT32;
510 const BitCountType Max15 = HasPopCnt ? CNT_POPCNT : CpuIs64Bit ? CNT64_MAX15 : CNT32_MAX15;
511 const Color Them = (Us == WHITE ? BLACK : WHITE);
512 const Square* ptr = pos.piece_list_begin(Us, Piece);
514 ei.attackedBy[Us][Piece] = EmptyBoardBB;
516 while ((s = *ptr++) != SQ_NONE)
518 // Find attacked squares, including x-ray attacks for bishops and rooks
519 if (Piece == KNIGHT || Piece == QUEEN)
520 b = pos.attacks_from<Piece>(s);
521 else if (Piece == BISHOP)
522 b = bishop_attacks_bb(s, pos.occupied_squares() & ~pos.pieces(QUEEN, Us));
523 else if (Piece == ROOK)
524 b = rook_attacks_bb(s, pos.occupied_squares() & ~pos.pieces(ROOK, QUEEN, Us));
528 // Update attack info
529 ei.attackedBy[Us][Piece] |= b;
532 if (b & ei.kingZone[Us])
534 ei.kingAttackersCount[Us]++;
535 ei.kingAttackersWeight[Us] += KingAttackWeights[Piece];
536 Bitboard bb = (b & ei.attackedBy[Them][KING]);
538 ei.kingAdjacentZoneAttacksCount[Us] += count_1s<Max15>(bb);
542 mob = (Piece != QUEEN ? count_1s<Max15>(b & mobilityArea)
543 : count_1s<Full >(b & mobilityArea));
545 mobility += MobilityBonus[Piece][mob];
547 // Decrease score if we are attacked by an enemy pawn. Remaining part
548 // of threat evaluation must be done later when we have full attack info.
549 if (bit_is_set(ei.attackedBy[Them][PAWN], s))
550 bonus -= ThreatedByPawnPenalty[Piece];
552 // Bishop and knight outposts squares
553 if ((Piece == BISHOP || Piece == KNIGHT) && pos.square_is_weak(s, Us))
554 bonus += evaluate_outposts<Piece, Us>(pos, ei, s);
556 // Queen or rook on 7th rank
557 if ( (Piece == ROOK || Piece == QUEEN)
558 && relative_rank(Us, s) == RANK_7
559 && relative_rank(Us, pos.king_square(Them)) == RANK_8)
561 bonus += (Piece == ROOK ? RookOn7thBonus : QueenOn7thBonus);
564 // Special extra evaluation for bishops
565 if (Piece == BISHOP && pos.is_chess960())
567 // An important Chess960 pattern: A cornered bishop blocked by
568 // a friendly pawn diagonally in front of it is a very serious
569 // problem, especially when that pawn is also blocked.
570 if (s == relative_square(Us, SQ_A1) || s == relative_square(Us, SQ_H1))
572 SquareDelta d = pawn_push(Us)
573 + (square_file(s) == FILE_A ? DELTA_E : DELTA_W);
574 if (pos.piece_on(s + d) == piece_of_color_and_type(Us, PAWN))
576 if (!pos.square_is_empty(s + d + pawn_push(Us)))
577 bonus -= 2*TrappedBishopA1H1Penalty;
578 else if (pos.piece_on(s + 2*d) == piece_of_color_and_type(Us, PAWN))
579 bonus -= TrappedBishopA1H1Penalty;
581 bonus -= TrappedBishopA1H1Penalty / 2;
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 bonus += RookOpenFileBonus;
596 bonus += 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 bonus -= 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 bonus -= make_score(pos.can_castle(Us) ? (TrappedRookPenalty - mob * 16) / 2
622 : (TrappedRookPenalty - mob * 16), 0);
630 // evaluate_threats<>() assigns bonuses according to the type of attacking piece
631 // and the type of attacked one.
634 Score evaluate_threats(const Position& pos, EvalInfo& ei) {
636 const Color Them = (Us == WHITE ? BLACK : WHITE);
639 Score bonus = SCORE_ZERO;
641 // Enemy pieces not defended by a pawn and under our attack
642 Bitboard weakEnemies = pos.pieces_of_color(Them)
643 & ~ei.attackedBy[Them][PAWN]
644 & ei.attackedBy[Us][0];
648 // Add bonus according to type of attacked enemy piece and to the
649 // type of attacking piece, from knights to queens. Kings are not
650 // considered because are already handled in king evaluation.
651 for (PieceType pt1 = KNIGHT; pt1 < KING; pt1++)
653 b = ei.attackedBy[Us][pt1] & weakEnemies;
655 for (PieceType pt2 = PAWN; pt2 < KING; pt2++)
656 if (b & pos.pieces(pt2))
657 bonus += ThreatBonus[pt1][pt2];
663 // evaluate_pieces_of_color<>() assigns bonuses and penalties to all the
664 // pieces of a given color.
666 template<Color Us, bool HasPopCnt>
667 Score evaluate_pieces_of_color(const Position& pos, EvalInfo& ei, Score& mobility) {
669 const Color Them = (Us == WHITE ? BLACK : WHITE);
671 Score bonus = mobility = SCORE_ZERO;
673 // Do not include in mobility squares protected by enemy pawns or occupied by our pieces
674 const Bitboard mobilityArea = ~(ei.attackedBy[Them][PAWN] | pos.pieces_of_color(Us));
676 bonus += evaluate_pieces<KNIGHT, Us, HasPopCnt>(pos, ei, mobility, mobilityArea);
677 bonus += evaluate_pieces<BISHOP, Us, HasPopCnt>(pos, ei, mobility, mobilityArea);
678 bonus += evaluate_pieces<ROOK, Us, HasPopCnt>(pos, ei, mobility, mobilityArea);
679 bonus += evaluate_pieces<QUEEN, Us, HasPopCnt>(pos, ei, mobility, mobilityArea);
681 // Sum up all attacked squares
682 ei.attackedBy[Us][0] = ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
683 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
684 | ei.attackedBy[Us][QUEEN] | ei.attackedBy[Us][KING];
689 // evaluate_king<>() assigns bonuses and penalties to a king of a given color
691 template<Color Us, bool HasPopCnt>
692 Score evaluate_king(const Position& pos, EvalInfo& ei, Value margins[]) {
694 const BitCountType Max15 = HasPopCnt ? CNT_POPCNT : CpuIs64Bit ? CNT64_MAX15 : CNT32_MAX15;
695 const Color Them = (Us == WHITE ? BLACK : WHITE);
697 Bitboard undefended, b, b1, b2, safe;
699 const Square ksq = pos.king_square(Us);
702 Score bonus = ei.pi->king_shelter<Us>(pos, ksq);
704 // King safety. This is quite complicated, and is almost certainly far
705 // from optimally tuned.
706 if ( ei.kingAttackersCount[Them] >= 2
707 && ei.kingAdjacentZoneAttacksCount[Them])
709 // Find the attacked squares around the king which has no defenders
710 // apart from the king itself
711 undefended = ei.attackedBy[Them][0] & ei.attackedBy[Us][KING];
712 undefended &= ~( ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
713 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
714 | ei.attackedBy[Us][QUEEN]);
716 // Initialize the 'attackUnits' variable, which is used later on as an
717 // index to the KingDangerTable[] array. The initial value is based on
718 // the number and types of the enemy's attacking pieces, the number of
719 // attacked and undefended squares around our king, the square of the
720 // king, and the quality of the pawn shelter.
721 attackUnits = Min(25, (ei.kingAttackersCount[Them] * ei.kingAttackersWeight[Them]) / 2)
722 + 3 * (ei.kingAdjacentZoneAttacksCount[Them] + count_1s<Max15>(undefended))
723 + InitKingDanger[relative_square(Us, ksq)]
724 - mg_value(ei.pi->king_shelter<Us>(pos, ksq)) / 32;
726 // Analyse enemy's safe queen contact checks. First find undefended
727 // squares around the king attacked by enemy queen...
728 b = undefended & ei.attackedBy[Them][QUEEN] & ~pos.pieces_of_color(Them);
731 // ...then remove squares not supported by another enemy piece
732 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
733 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][ROOK]);
735 attackUnits += QueenContactCheckBonus
737 * (Them == pos.side_to_move() ? 2 : 1);
740 // Analyse enemy's safe rook contact checks. First find undefended
741 // squares around the king attacked by enemy rooks...
742 b = undefended & ei.attackedBy[Them][ROOK] & ~pos.pieces_of_color(Them);
744 // Consider only squares where the enemy rook gives check
745 b &= RookPseudoAttacks[ksq];
749 // ...then remove squares not supported by another enemy piece
750 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
751 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][QUEEN]);
753 attackUnits += RookContactCheckBonus
755 * (Them == pos.side_to_move() ? 2 : 1);
758 // Analyse enemy's safe distance checks for sliders and knights
759 safe = ~(pos.pieces_of_color(Them) | ei.attackedBy[Us][0]);
761 b1 = pos.attacks_from<ROOK>(ksq) & safe;
762 b2 = pos.attacks_from<BISHOP>(ksq) & safe;
764 // Enemy queen safe checks
765 b = (b1 | b2) & ei.attackedBy[Them][QUEEN];
767 attackUnits += QueenCheckBonus * count_1s<Max15>(b);
769 // Enemy rooks safe checks
770 b = b1 & ei.attackedBy[Them][ROOK];
772 attackUnits += RookCheckBonus * count_1s<Max15>(b);
774 // Enemy bishops safe checks
775 b = b2 & ei.attackedBy[Them][BISHOP];
777 attackUnits += BishopCheckBonus * count_1s<Max15>(b);
779 // Enemy knights safe checks
780 b = pos.attacks_from<KNIGHT>(ksq) & ei.attackedBy[Them][KNIGHT] & safe;
782 attackUnits += KnightCheckBonus * count_1s<Max15>(b);
784 // To index KingDangerTable[] attackUnits must be in [0, 99] range
785 attackUnits = Min(99, Max(0, attackUnits));
787 // Finally, extract the king danger score from the KingDangerTable[]
788 // array and subtract the score from evaluation. Set also margins[]
789 // value that will be used for pruning because this value can sometimes
790 // be very big, and so capturing a single attacking piece can therefore
791 // result in a score change far bigger than the value of the captured piece.
792 bonus -= KingDangerTable[Us][attackUnits];
793 margins[Us] += mg_value(KingDangerTable[Us][attackUnits]);
799 // evaluate_passed_pawns<>() evaluates the passed pawns of the given color
802 Score evaluate_passed_pawns(const Position& pos, EvalInfo& ei) {
804 const Color Them = (Us == WHITE ? BLACK : WHITE);
806 Score bonus = SCORE_ZERO;
807 Bitboard squaresToQueen, defendedSquares, unsafeSquares, supportingPawns;
808 Bitboard b = ei.pi->passed_pawns(Us);
814 Square s = pop_1st_bit(&b);
816 assert(pos.pawn_is_passed(Us, s));
818 int r = int(relative_rank(Us, s) - RANK_2);
819 int rr = r * (r - 1);
821 // Base bonus based on rank
822 Value mbonus = Value(20 * rr);
823 Value ebonus = Value(10 * (rr + r + 1));
827 Square blockSq = s + pawn_push(Us);
829 // Adjust bonus based on kings proximity
830 ebonus -= Value(square_distance(pos.king_square(Us), blockSq) * 3 * rr);
831 ebonus -= Value(square_distance(pos.king_square(Us), blockSq + pawn_push(Us)) * rr);
832 ebonus += Value(square_distance(pos.king_square(Them), blockSq) * 6 * rr);
834 // If the pawn is free to advance, increase bonus
835 if (pos.square_is_empty(blockSq))
837 squaresToQueen = squares_in_front_of(Us, s);
838 defendedSquares = squaresToQueen & ei.attackedBy[Us][0];
840 // If there is an enemy rook or queen attacking the pawn from behind,
841 // add all X-ray attacks by the rook or queen. Otherwise consider only
842 // the squares in the pawn's path attacked or occupied by the enemy.
843 if ( (squares_behind(Us, s) & pos.pieces(ROOK, QUEEN, Them))
844 && (squares_behind(Us, s) & pos.pieces(ROOK, QUEEN, Them) & pos.attacks_from<ROOK>(s)))
845 unsafeSquares = squaresToQueen;
847 unsafeSquares = squaresToQueen & (ei.attackedBy[Them][0] | pos.pieces_of_color(Them));
849 // If there aren't enemy attacks or pieces along the path to queen give
850 // huge bonus. Even bigger if we protect the pawn's path.
852 ebonus += Value(rr * (squaresToQueen == defendedSquares ? 17 : 15));
854 // OK, there are enemy attacks or pieces (but not pawns). Are those
855 // squares which are attacked by the enemy also attacked by us ?
856 // If yes, big bonus (but smaller than when there are no enemy attacks),
857 // if no, somewhat smaller bonus.
858 ebonus += Value(rr * ((unsafeSquares & defendedSquares) == unsafeSquares ? 13 : 8));
860 // At last, add a small bonus when there are no *friendly* pieces
861 // in the pawn's path.
862 if (!(squaresToQueen & pos.pieces_of_color(Us)))
867 // Increase the bonus if the passed pawn is supported by a friendly pawn
868 // on the same rank and a bit smaller if it's on the previous rank.
869 supportingPawns = pos.pieces(PAWN, Us) & neighboring_files_bb(s);
870 if (supportingPawns & rank_bb(s))
871 ebonus += Value(r * 20);
872 else if (supportingPawns & rank_bb(s - pawn_push(Us)))
873 ebonus += Value(r * 12);
875 // Rook pawns are a special case: They are sometimes worse, and
876 // sometimes better than other passed pawns. It is difficult to find
877 // good rules for determining whether they are good or bad. For now,
878 // we try the following: Increase the value for rook pawns if the
879 // other side has no pieces apart from a knight, and decrease the
880 // value if the other side has a rook or queen.
881 if (square_file(s) == FILE_A || square_file(s) == FILE_H)
883 if (pos.non_pawn_material(Them) <= KnightValueMidgame)
884 ebonus += ebonus / 4;
885 else if (pos.pieces(ROOK, QUEEN, Them))
886 ebonus -= ebonus / 4;
888 bonus += make_score(mbonus, ebonus);
892 // Add the scores to the middle game and endgame eval
893 return apply_weight(bonus, Weights[PassedPawns]);
896 // evaluate_unstoppable_pawns() evaluates the unstoppable passed pawns for both sides
897 template<bool HasPopCnt>
898 Score evaluate_unstoppable_pawns(const Position& pos, EvalInfo& ei) {
900 const BitCountType Max15 = HasPopCnt ? CNT_POPCNT : CpuIs64Bit ? CNT64_MAX15 : CNT32_MAX15;
902 // Step 1. Hunt for unstoppable pawns. If we find at least one, record how many plies
903 // are required for promotion
904 int pliesToGo[2] = {256, 256};
906 for (Color c = WHITE; c <= BLACK; c++)
908 // Skip if other side has non-pawn pieces
909 if (pos.non_pawn_material(opposite_color(c)))
912 Bitboard b = ei.pi->passed_pawns(c);
916 Square s = pop_1st_bit(&b);
917 Square queeningSquare = relative_square(c, make_square(square_file(s), RANK_8));
919 int mtg = RANK_8 - relative_rank(c, s) - int(relative_rank(c, s) == RANK_2);
920 int oppmtg = square_distance(pos.king_square(opposite_color(c)), queeningSquare) - int(c != pos.side_to_move());
921 bool pathDefended = ((ei.attackedBy[c][0] & squares_in_front_of(c, s)) == squares_in_front_of(c, s));
923 if (mtg >= oppmtg && !pathDefended)
926 int blockerCount = count_1s<Max15>(squares_in_front_of(c, s) & pos.occupied_squares());
929 if (mtg >= oppmtg && !pathDefended)
932 int ptg = 2 * mtg - int(c == pos.side_to_move());
934 if (ptg < pliesToGo[c])
939 // Step 2. If either side cannot promote at least three plies before the other side then
940 // situation becomes too complex and we give up. Otherwise we determine the possibly "winning side"
941 if (abs(pliesToGo[WHITE] - pliesToGo[BLACK]) < 3)
942 return make_score(0, 0);
944 Color winnerSide = (pliesToGo[WHITE] < pliesToGo[BLACK] ? WHITE : BLACK);
945 Color loserSide = opposite_color(winnerSide);
947 // Step 3. Can the losing side possibly create a new passed pawn and thus prevent the loss?
948 // We collect the potential candidates in potentialBB.
949 Bitboard pawnBB = pos.pieces(PAWN, loserSide);
950 Bitboard potentialBB = pawnBB;
951 const Bitboard passedBB = ei.pi->passed_pawns(loserSide);
955 Square psq = pop_1st_bit(&pawnBB);
957 // Check direct advancement
958 int mtg = RANK_8 - relative_rank(loserSide, psq) - int(relative_rank(loserSide, psq) == RANK_2);
959 int ptg = 2 * mtg - int(loserSide == pos.side_to_move());
961 // Check if (without even considering any obstacles) we're too far away
962 if (pliesToGo[winnerSide] + 3 <= ptg)
964 clear_bit(&potentialBB, psq);
968 // If this is passed pawn, then it _may_ promote in time. We give up.
969 if (bit_is_set(passedBB, psq))
970 return make_score(0, 0);
972 // Doubled pawn is worthless
973 if (squares_in_front_of(loserSide, psq) & (pos.pieces(PAWN, loserSide)))
975 clear_bit(&potentialBB, psq);
980 // Step 4. Check new passed pawn creation through king capturing and sacrifises
981 pawnBB = potentialBB;
985 Square psq = pop_1st_bit(&pawnBB);
987 int mtg = RANK_8 - relative_rank(loserSide, psq) - int(relative_rank(loserSide, psq) == RANK_2);
988 int ptg = 2 * mtg - int(loserSide == pos.side_to_move());
990 // Generate list of obstacles
991 Bitboard obsBB = passed_pawn_mask(loserSide, psq) & pos.pieces(PAWN, winnerSide);
992 const bool pawnIsOpposed = squares_in_front_of(loserSide, psq) & obsBB;
995 // How many plies does it take to remove all the obstacles?
997 int realObsCount = 0;
998 int minKingDist = 256;
1002 Square obSq = pop_1st_bit(&obsBB);
1005 // Check pawns that can give support to overcome obstacle (Eg. wp: a4,b4 bp: b2. b4 is giving support)
1006 if (!pawnIsOpposed && square_file(psq) != square_file(obSq))
1008 Bitboard supBB = in_front_bb(winnerSide, Square(obSq + (winnerSide == WHITE ? 8 : -8)))
1009 & neighboring_files_bb(psq) & potentialBB;
1011 while(supBB) // This while-loop could be replaced with supSq = LSB/MSB(supBB) (depending on color)
1013 Square supSq = pop_1st_bit(&supBB);
1014 int dist = square_distance(obSq, supSq);
1015 minMoves = Min(minMoves, dist - 2);
1020 // Check pawns that can be sacrifised
1021 Bitboard sacBB = passed_pawn_mask(winnerSide, obSq) & neighboring_files_bb(obSq) & potentialBB & ~(1ULL << psq);
1023 while(sacBB) // This while-loop could be replaced with sacSq = LSB/MSB(sacBB) (depending on color)
1025 Square sacSq = pop_1st_bit(&sacBB);
1026 int dist = square_distance(obSq, sacSq);
1027 minMoves = Min(minMoves, dist - 2);
1030 // If obstacle can be destroyed with immediate pawn sacrifise, it's not real obstacle
1034 // Pawn sac calculations
1035 sacptg += minMoves * 2;
1037 // King capture calc
1039 int kingDist = square_distance(pos.king_square(loserSide), obSq);
1040 minKingDist = Min(minKingDist, kingDist);
1043 // Check if pawn sac plan _may_ save the day
1044 if (pliesToGo[winnerSide] + 3 > ptg + sacptg)
1045 return make_score(0, 0);
1047 // Check if king capture plan _may_ save the day (contains some false positives)
1048 int kingptg = (minKingDist + realObsCount) * 2;
1049 if (pliesToGo[winnerSide] + 3 > ptg + kingptg)
1050 return make_score(0, 0);
1053 // Step 5. Assign bonus
1054 const int Sign[2] = {1, -1};
1055 return Sign[winnerSide] * make_score(0, (Value) 0x500 - 0x20 * pliesToGo[winnerSide]);
1059 // evaluate_space() computes the space evaluation for a given side. The
1060 // space evaluation is a simple bonus based on the number of safe squares
1061 // available for minor pieces on the central four files on ranks 2--4. Safe
1062 // squares one, two or three squares behind a friendly pawn are counted
1063 // twice. Finally, the space bonus is scaled by a weight taken from the
1064 // material hash table. The aim is to improve play on game opening.
1065 template<Color Us, bool HasPopCnt>
1066 int evaluate_space(const Position& pos, EvalInfo& ei) {
1068 const BitCountType Max15 = HasPopCnt ? CNT_POPCNT : CpuIs64Bit ? CNT64_MAX15 : CNT32_MAX15;
1069 const Color Them = (Us == WHITE ? BLACK : WHITE);
1071 // Find the safe squares for our pieces inside the area defined by
1072 // SpaceMask[]. A square is unsafe if it is attacked by an enemy
1073 // pawn, or if it is undefended and attacked by an enemy piece.
1074 Bitboard safe = SpaceMask[Us]
1075 & ~pos.pieces(PAWN, Us)
1076 & ~ei.attackedBy[Them][PAWN]
1077 & (ei.attackedBy[Us][0] | ~ei.attackedBy[Them][0]);
1079 // Find all squares which are at most three squares behind some friendly pawn
1080 Bitboard behind = pos.pieces(PAWN, Us);
1081 behind |= (Us == WHITE ? behind >> 8 : behind << 8);
1082 behind |= (Us == WHITE ? behind >> 16 : behind << 16);
1084 return count_1s<Max15>(safe) + count_1s<Max15>(behind & safe);
1088 // apply_weight() applies an evaluation weight to a value trying to prevent overflow
1090 inline Score apply_weight(Score v, Score w) {
1091 return make_score((int(mg_value(v)) * mg_value(w)) / 0x100,
1092 (int(eg_value(v)) * eg_value(w)) / 0x100);
1096 // scale_by_game_phase() interpolates between a middle game and an endgame score,
1097 // based on game phase. It also scales the return value by a ScaleFactor array.
1099 Value scale_by_game_phase(const Score& v, Phase ph, ScaleFactor sf) {
1101 assert(mg_value(v) > -VALUE_INFINITE && mg_value(v) < VALUE_INFINITE);
1102 assert(eg_value(v) > -VALUE_INFINITE && eg_value(v) < VALUE_INFINITE);
1103 assert(ph >= PHASE_ENDGAME && ph <= PHASE_MIDGAME);
1105 Value eg = eg_value(v);
1106 Value ev = Value((eg * int(sf)) / SCALE_FACTOR_NORMAL);
1108 int result = (mg_value(v) * int(ph) + ev * int(128 - ph)) / 128;
1109 return Value(result & ~(GrainSize - 1));
1113 // weight_option() computes the value of an evaluation weight, by combining
1114 // two UCI-configurable weights (midgame and endgame) with an internal weight.
1116 Score weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight) {
1118 // Scale option value from 100 to 256
1119 int mg = Options[mgOpt].value<int>() * 256 / 100;
1120 int eg = Options[egOpt].value<int>() * 256 / 100;
1122 return apply_weight(make_score(mg, eg), internalWeight);
1126 // init_safety() initizes the king safety evaluation, based on UCI
1127 // parameters. It is called from read_weights().
1129 void init_safety() {
1131 const Value MaxSlope = Value(30);
1132 const Value Peak = Value(1280);
1135 // First setup the base table
1136 for (int i = 0; i < 100; i++)
1138 t[i] = Value(int(0.4 * i * i));
1141 t[i] = Min(t[i], t[i - 1] + MaxSlope);
1143 t[i] = Min(t[i], Peak);
1146 // Then apply the weights and get the final KingDangerTable[] array
1147 for (Color c = WHITE; c <= BLACK; c++)
1148 for (int i = 0; i < 100; i++)
1149 KingDangerTable[c][i] = apply_weight(make_score(t[i], 0), Weights[KingDangerUs + c]);