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 // updateKingTables[color] is set to true if we have enough material
49 // to trigger the opponent's king safety calculation. When is false we
50 // skip the time consuming update of the king attackers tables.
51 bool updateKingTables[2];
53 // attackedBy[color][piece type] is a bitboard representing all squares
54 // attacked by a given color and piece type, attackedBy[color][0] contains
55 // all squares attacked by the given color.
56 Bitboard attackedBy[2][8];
58 // kingZone[color] is the zone around the enemy king which is considered
59 // by the king safety evaluation. This consists of the squares directly
60 // adjacent to the king, and the three (or two, for a king on an edge file)
61 // squares two ranks in front of the king. For instance, if black's king
62 // is on g8, kingZone[WHITE] is a bitboard containing the squares f8, h8,
63 // f7, g7, h7, f6, g6 and h6.
66 // kingAttackersCount[color] is the number of pieces of the given color
67 // which attack a square in the kingZone of the enemy king.
68 int kingAttackersCount[2];
70 // kingAttackersWeight[color] is the sum of the "weight" of the pieces of the
71 // given color which attack a square in the kingZone of the enemy king. The
72 // weights of the individual piece types are given by the variables
73 // QueenAttackWeight, RookAttackWeight, BishopAttackWeight and
74 // KnightAttackWeight in evaluate.cpp
75 int kingAttackersWeight[2];
77 // kingAdjacentZoneAttacksCount[color] is the number of attacks to squares
78 // directly adjacent to the king of the given color. Pieces which attack
79 // more than one square are counted multiple times. For instance, if black's
80 // king is on g8 and there's a white knight on g5, this knight adds
81 // 2 to kingAdjacentZoneAttacksCount[BLACK].
82 int kingAdjacentZoneAttacksCount[2];
85 // Evaluation grain size, must be a power of 2
86 const int GrainSize = 8;
88 // Evaluation weights, initialized from UCI options
89 enum { Mobility, PawnStructure, PassedPawns, Space, KingDangerUs, KingDangerThem };
93 #define S(mg, eg) make_score(mg, eg)
95 // Internal evaluation weights. These are applied on top of the evaluation
96 // weights read from UCI parameters. The purpose is to be able to change
97 // the evaluation weights while keeping the default values of the UCI
98 // parameters at 100, which looks prettier.
100 // Values modified by Joona Kiiski
101 const Score WeightsInternal[] = {
102 S(248, 271), S(233, 201), S(252, 259), S(46, 0), S(247, 0), S(259, 0)
105 // MobilityBonus[PieceType][attacked] contains mobility bonuses for middle and
106 // end game, indexed by piece type and number of attacked squares not occupied
107 // by friendly pieces.
108 const Score MobilityBonus[][32] = {
110 { S(-38,-33), S(-25,-23), S(-12,-13), S( 0, -3), S(12, 7), S(25, 17), // Knights
111 S( 31, 22), S( 38, 27), S( 38, 27) },
112 { S(-25,-30), S(-11,-16), S( 3, -2), S(17, 12), S(31, 26), S(45, 40), // Bishops
113 S( 57, 52), S( 65, 60), S( 71, 65), S(74, 69), S(76, 71), S(78, 73),
114 S( 79, 74), S( 80, 75), S( 81, 76), S(81, 76) },
115 { S(-20,-36), S(-14,-19), S( -8, -3), S(-2, 13), S( 4, 29), S(10, 46), // Rooks
116 S( 14, 62), S( 19, 79), S( 23, 95), S(26,106), S(27,111), S(28,114),
117 S( 29,116), S( 30,117), S( 31,118), S(32,118) },
118 { S(-10,-18), S( -8,-13), S( -6, -7), S(-3, -2), S(-1, 3), S( 1, 8), // Queens
119 S( 3, 13), S( 5, 19), S( 8, 23), S(10, 27), S(12, 32), S(15, 34),
120 S( 16, 35), S( 17, 35), S( 18, 35), S(20, 35), S(20, 35), S(20, 35),
121 S( 20, 35), S( 20, 35), S( 20, 35), S(20, 35), S(20, 35), S(20, 35),
122 S( 20, 35), S( 20, 35), S( 20, 35), S(20, 35), S(20, 35), S(20, 35),
123 S( 20, 35), S( 20, 35) }
126 // OutpostBonus[PieceType][Square] contains outpost bonuses of knights and
127 // bishops, indexed by piece type and square (from white's point of view).
128 const Value OutpostBonus[][64] = {
131 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // Knights
132 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0),
133 V(0), V(0), V(4), V(8), V(8), V(4), V(0), V(0),
134 V(0), V(4),V(17),V(26),V(26),V(17), V(4), V(0),
135 V(0), V(8),V(26),V(35),V(35),V(26), V(8), V(0),
136 V(0), V(4),V(17),V(17),V(17),V(17), V(4), V(0) },
138 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // Bishops
139 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0),
140 V(0), V(0), V(5), V(5), V(5), V(5), V(0), V(0),
141 V(0), V(5),V(10),V(10),V(10),V(10), V(5), V(0),
142 V(0),V(10),V(21),V(21),V(21),V(21),V(10), V(0),
143 V(0), V(5), V(8), V(8), V(8), V(8), V(5), V(0) }
146 // ThreatBonus[attacking][attacked] contains threat bonuses according to
147 // which piece type attacks which one.
148 const Score ThreatBonus[][8] = {
150 { S(0, 0), S( 7, 39), S( 0, 0), S(24, 49), S(41,100), S(41,100) }, // KNIGHT
151 { S(0, 0), S( 7, 39), S(24, 49), S( 0, 0), S(41,100), S(41,100) }, // BISHOP
152 { S(0, 0), S(-1, 29), S(15, 49), S(15, 49), S( 0, 0), S(24, 49) }, // ROOK
153 { S(0, 0), S(15, 39), S(15, 39), S(15, 39), S(15, 39), S( 0, 0) } // QUEEN
156 // ThreatedByPawnPenalty[PieceType] contains a penalty according to which
157 // piece type is attacked by an enemy pawn.
158 const Score ThreatedByPawnPenalty[] = {
159 S(0, 0), S(0, 0), S(56, 70), S(56, 70), S(76, 99), S(86, 118)
164 // Rooks and queens on the 7th rank (modified by Joona Kiiski)
165 const Score RookOn7thBonus = make_score(47, 98);
166 const Score QueenOn7thBonus = make_score(27, 54);
168 // Rooks on open files (modified by Joona Kiiski)
169 const Score RookOpenFileBonus = make_score(43, 43);
170 const Score RookHalfOpenFileBonus = make_score(19, 19);
172 // Penalty for rooks trapped inside a friendly king which has lost the
174 const Value TrappedRookPenalty = Value(180);
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& margin);
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 Score apply_weight(Score v, Score weight);
250 Value scale_by_game_phase(const Score& v, Phase ph, ScaleFactor sf);
251 Score weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight);
261 /// Prefetches in pawn hash tables
263 void prefetchPawn(Key key, int threadID) {
265 PawnTable[threadID]->prefetch(key);
269 /// evaluate() is the main evaluation function. It always computes two
270 /// values, an endgame score and a middle game score, and interpolates
271 /// between them based on the remaining material.
272 Value evaluate(const Position& pos, Value& margin) {
274 return CpuHasPOPCNT ? do_evaluate<true>(pos, margin)
275 : do_evaluate<false>(pos, margin);
280 template<bool HasPopCnt>
281 Value do_evaluate(const Position& pos, Value& margin) {
284 Score mobilityWhite, mobilityBlack;
287 assert(pos.thread() >= 0 && pos.thread() < MAX_THREADS);
288 assert(!pos.is_check());
290 // Initialize value by reading the incrementally updated scores included
291 // in the position object (material + piece square tables).
292 Score bonus = pos.value();
294 // margin is the uncertainty estimation of position's evaluation
295 // and typically is used by the search for pruning decisions.
298 // Probe the material hash table
299 MaterialInfo* mi = MaterialTable[pos.thread()]->get_material_info(pos);
300 bonus += mi->material_value();
302 // If we have a specialized evaluation function for the current material
303 // configuration, call it and return.
304 if (mi->specialized_eval_exists())
305 return mi->evaluate(pos);
307 // Probe the pawn hash table
308 ei.pi = PawnTable[pos.thread()]->get_pawn_info(pos);
309 bonus += apply_weight(ei.pi->pawns_value(), Weights[PawnStructure]);
311 // Initialize attack and king safety bitboards
312 init_eval_info<WHITE, HasPopCnt>(pos, ei);
313 init_eval_info<BLACK, HasPopCnt>(pos, ei);
315 // Evaluate pieces and mobility
316 bonus += evaluate_pieces_of_color<WHITE, HasPopCnt>(pos, ei, mobilityWhite)
317 - evaluate_pieces_of_color<BLACK, HasPopCnt>(pos, ei, mobilityBlack);
319 bonus += apply_weight(mobilityWhite - mobilityBlack, Weights[Mobility]);
321 // Evaluate kings after all other pieces because we need complete attack
322 // information when computing the king safety evaluation.
323 bonus += evaluate_king<WHITE, HasPopCnt>(pos, ei, margin)
324 - evaluate_king<BLACK, HasPopCnt>(pos, ei, margin);
326 // Evaluate tactical threats, we need full attack information including king
327 bonus += evaluate_threats<WHITE>(pos, ei)
328 - evaluate_threats<BLACK>(pos, ei);
330 // Evaluate passed pawns, we need full attack information including king
331 bonus += evaluate_passed_pawns<WHITE>(pos, ei)
332 - evaluate_passed_pawns<BLACK>(pos, ei);
334 // Evaluate space for both sides, only in middle-game.
335 if (mi->space_weight())
337 int s = evaluate_space<WHITE, HasPopCnt>(pos, ei) - evaluate_space<BLACK, HasPopCnt>(pos, ei);
338 bonus += apply_weight(make_score(s * mi->space_weight(), 0), Weights[Space]);
341 // Scale winning side if position is more drawish that what it appears
342 ScaleFactor sf = eg_value(bonus) > VALUE_ZERO ? mi->scale_factor(pos, WHITE)
343 : mi->scale_factor(pos, BLACK);
344 Phase phase = mi->game_phase();
346 // If we don't already have an unusual scale factor, check for opposite
347 // colored bishop endgames, and use a lower scale for those.
348 if ( phase < PHASE_MIDGAME
349 && pos.opposite_colored_bishops()
350 && sf == SCALE_FACTOR_NORMAL)
352 // Only the two bishops ?
353 if ( pos.non_pawn_material(WHITE) == BishopValueMidgame
354 && pos.non_pawn_material(BLACK) == BishopValueMidgame)
356 // Check for KBP vs KB with only a single pawn that is almost
357 // certainly a draw or at least two pawns.
358 bool one_pawn = (pos.piece_count(WHITE, PAWN) + pos.piece_count(BLACK, PAWN) == 1);
359 sf = one_pawn ? ScaleFactor(8) : ScaleFactor(32);
362 // Endgame with opposite-colored bishops, but also other pieces. Still
363 // a bit drawish, but not as drawish as with only the two bishops.
364 sf = ScaleFactor(50);
367 // Interpolate between the middle game and the endgame score
368 Value v = scale_by_game_phase(bonus, phase, sf);
369 return pos.side_to_move() == WHITE ? v : -v;
375 /// init_eval() initializes various tables used by the evaluation function
377 void init_eval(int threads) {
379 assert(threads <= MAX_THREADS);
381 for (int i = 0; i < MAX_THREADS; i++)
386 delete MaterialTable[i];
388 MaterialTable[i] = NULL;
392 PawnTable[i] = new PawnInfoTable();
394 if (!MaterialTable[i])
395 MaterialTable[i] = new MaterialInfoTable();
400 /// quit_eval() releases heap-allocated memory at program termination
408 /// read_weights() reads evaluation weights from the corresponding UCI parameters
410 void read_weights(Color us) {
412 // King safety is asymmetrical. Our king danger level is weighted by
413 // "Cowardice" UCI parameter, instead the opponent one by "Aggressiveness".
414 const int kingDangerUs = (us == WHITE ? KingDangerUs : KingDangerThem);
415 const int kingDangerThem = (us == WHITE ? KingDangerThem : KingDangerUs);
417 Weights[Mobility] = weight_option("Mobility (Middle Game)", "Mobility (Endgame)", WeightsInternal[Mobility]);
418 Weights[PawnStructure] = weight_option("Pawn Structure (Middle Game)", "Pawn Structure (Endgame)", WeightsInternal[PawnStructure]);
419 Weights[PassedPawns] = weight_option("Passed Pawns (Middle Game)", "Passed Pawns (Endgame)", WeightsInternal[PassedPawns]);
420 Weights[Space] = weight_option("Space", "Space", WeightsInternal[Space]);
421 Weights[kingDangerUs] = weight_option("Cowardice", "Cowardice", WeightsInternal[KingDangerUs]);
422 Weights[kingDangerThem] = weight_option("Aggressiveness", "Aggressiveness", WeightsInternal[KingDangerThem]);
424 // If running in analysis mode, make sure we use symmetrical king safety. We do this
425 // by replacing both Weights[kingDangerUs] and Weights[kingDangerThem] by their average.
426 if (get_option_value_bool("UCI_AnalyseMode"))
427 Weights[kingDangerUs] = Weights[kingDangerThem] = (Weights[kingDangerUs] + Weights[kingDangerThem]) / 2;
435 // init_eval_info() initializes king bitboards for given color adding
436 // pawn attacks. To be done at the beginning of the evaluation.
438 template<Color Us, bool HasPopCnt>
439 void init_eval_info(const Position& pos, EvalInfo& ei) {
441 const BitCountType Max15 = HasPopCnt ? CNT_POPCNT : CpuIs64Bit ? CNT64_MAX15 : CNT32_MAX15;
442 const Color Them = (Us == WHITE ? BLACK : WHITE);
444 Bitboard b = ei.attackedBy[Them][KING] = pos.attacks_from<KING>(pos.king_square(Them));
445 ei.attackedBy[Us][PAWN] = ei.pi->pawn_attacks(Us);
446 ei.updateKingTables[Us] = pos.piece_count(Us, QUEEN) && pos.non_pawn_material(Us) >= QueenValueMidgame + RookValueMidgame;
447 if (ei.updateKingTables[Us])
449 ei.kingZone[Us] = (b | (Us == WHITE ? b >> 8 : b << 8));
450 b &= ei.attackedBy[Us][PAWN];
451 ei.kingAttackersCount[Us] = b ? count_1s<Max15>(b) / 2 : EmptyBoardBB;
452 ei.kingAdjacentZoneAttacksCount[Us] = ei.kingAttackersWeight[Us] = EmptyBoardBB;
457 // evaluate_outposts() evaluates bishop and knight outposts squares
459 template<PieceType Piece, Color Us>
460 Score evaluate_outposts(const Position& pos, EvalInfo& ei, Square s) {
462 const Color Them = (Us == WHITE ? BLACK : WHITE);
464 assert (Piece == BISHOP || Piece == KNIGHT);
466 // Initial bonus based on square
467 Value bonus = OutpostBonus[Piece == BISHOP][relative_square(Us, s)];
469 // Increase bonus if supported by pawn, especially if the opponent has
470 // no minor piece which can exchange the outpost piece.
471 if (bonus && bit_is_set(ei.attackedBy[Us][PAWN], s))
473 if ( pos.pieces(KNIGHT, Them) == EmptyBoardBB
474 && (SquaresByColorBB[square_color(s)] & pos.pieces(BISHOP, Them)) == EmptyBoardBB)
475 bonus += bonus + bonus / 2;
479 return make_score(bonus, bonus);
483 // evaluate_pieces<>() assigns bonuses and penalties to the pieces of a given color
485 template<PieceType Piece, Color Us, bool HasPopCnt>
486 Score evaluate_pieces(const Position& pos, EvalInfo& ei, Score& mobility, Bitboard mobilityArea) {
492 Score bonus = SCORE_ZERO;
494 const BitCountType Full = HasPopCnt ? CNT_POPCNT : CpuIs64Bit ? CNT64 : CNT32;
495 const BitCountType Max15 = HasPopCnt ? CNT_POPCNT : CpuIs64Bit ? CNT64_MAX15 : CNT32_MAX15;
496 const Color Them = (Us == WHITE ? BLACK : WHITE);
497 const Square* ptr = pos.piece_list_begin(Us, Piece);
499 ei.attackedBy[Us][Piece] = EmptyBoardBB;
501 while ((s = *ptr++) != SQ_NONE)
503 // Find attacked squares, including x-ray attacks for bishops and rooks
504 if (Piece == KNIGHT || Piece == QUEEN)
505 b = pos.attacks_from<Piece>(s);
506 else if (Piece == BISHOP)
507 b = bishop_attacks_bb(s, pos.occupied_squares() & ~pos.pieces(QUEEN, Us));
508 else if (Piece == ROOK)
509 b = rook_attacks_bb(s, pos.occupied_squares() & ~pos.pieces(ROOK, QUEEN, Us));
513 // Update attack info
514 ei.attackedBy[Us][Piece] |= b;
517 if (ei.updateKingTables[Us] && (b & ei.kingZone[Us]))
519 ei.kingAttackersCount[Us]++;
520 ei.kingAttackersWeight[Us] += KingAttackWeights[Piece];
521 Bitboard bb = (b & ei.attackedBy[Them][KING]);
523 ei.kingAdjacentZoneAttacksCount[Us] += count_1s<Max15>(bb);
527 mob = (Piece != QUEEN ? count_1s<Max15>(b & mobilityArea)
528 : count_1s<Full >(b & mobilityArea));
530 mobility += MobilityBonus[Piece][mob];
532 // Decrease score if we are attacked by an enemy pawn. Remaining part
533 // of threat evaluation must be done later when we have full attack info.
534 if (bit_is_set(ei.attackedBy[Them][PAWN], s))
535 bonus -= ThreatedByPawnPenalty[Piece];
537 // Bishop and knight outposts squares
538 if ((Piece == BISHOP || Piece == KNIGHT) && pos.square_is_weak(s, Us))
539 bonus += evaluate_outposts<Piece, Us>(pos, ei, s);
541 // Queen or rook on 7th rank
542 if ( (Piece == ROOK || Piece == QUEEN)
543 && relative_rank(Us, s) == RANK_7
544 && relative_rank(Us, pos.king_square(Them)) == RANK_8)
546 bonus += (Piece == ROOK ? RookOn7thBonus : QueenOn7thBonus);
549 // Special extra evaluation for rooks
552 // Open and half-open files
554 if (ei.pi->file_is_half_open(Us, f))
556 if (ei.pi->file_is_half_open(Them, f))
557 bonus += RookOpenFileBonus;
559 bonus += RookHalfOpenFileBonus;
562 // Penalize rooks which are trapped inside a king. Penalize more if
563 // king has lost right to castle.
564 if (mob > 6 || ei.pi->file_is_half_open(Us, f))
567 ksq = pos.king_square(Us);
569 if ( square_file(ksq) >= FILE_E
570 && square_file(s) > square_file(ksq)
571 && (relative_rank(Us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
573 // Is there a half-open file between the king and the edge of the board?
574 if (!ei.pi->has_open_file_to_right(Us, square_file(ksq)))
575 bonus -= make_score(pos.can_castle(Us) ? (TrappedRookPenalty - mob * 16) / 2
576 : (TrappedRookPenalty - mob * 16), 0);
578 else if ( square_file(ksq) <= FILE_D
579 && square_file(s) < square_file(ksq)
580 && (relative_rank(Us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
582 // Is there a half-open file between the king and the edge of the board?
583 if (!ei.pi->has_open_file_to_left(Us, square_file(ksq)))
584 bonus -= make_score(pos.can_castle(Us) ? (TrappedRookPenalty - mob * 16) / 2
585 : (TrappedRookPenalty - mob * 16), 0);
593 // evaluate_threats<>() assigns bonuses according to the type of attacking piece
594 // and the type of attacked one.
597 Score evaluate_threats(const Position& pos, EvalInfo& ei) {
599 const Color Them = (Us == WHITE ? BLACK : WHITE);
602 Score bonus = SCORE_ZERO;
604 // Enemy pieces not defended by a pawn and under our attack
605 Bitboard weakEnemies = pos.pieces_of_color(Them)
606 & ~ei.attackedBy[Them][PAWN]
607 & ei.attackedBy[Us][0];
611 // Add bonus according to type of attacked enemy piece and to the
612 // type of attacking piece, from knights to queens. Kings are not
613 // considered because are already handled in king evaluation.
614 for (PieceType pt1 = KNIGHT; pt1 < KING; pt1++)
616 b = ei.attackedBy[Us][pt1] & weakEnemies;
618 for (PieceType pt2 = PAWN; pt2 < KING; pt2++)
619 if (b & pos.pieces(pt2))
620 bonus += ThreatBonus[pt1][pt2];
626 // evaluate_pieces_of_color<>() assigns bonuses and penalties to all the
627 // pieces of a given color.
629 template<Color Us, bool HasPopCnt>
630 Score evaluate_pieces_of_color(const Position& pos, EvalInfo& ei, Score& mobility) {
632 const Color Them = (Us == WHITE ? BLACK : WHITE);
634 Score bonus = mobility = SCORE_ZERO;
636 // Do not include in mobility squares protected by enemy pawns or occupied by our pieces
637 const Bitboard mobilityArea = ~(ei.attackedBy[Them][PAWN] | pos.pieces_of_color(Us));
639 bonus += evaluate_pieces<KNIGHT, Us, HasPopCnt>(pos, ei, mobility, mobilityArea);
640 bonus += evaluate_pieces<BISHOP, Us, HasPopCnt>(pos, ei, mobility, mobilityArea);
641 bonus += evaluate_pieces<ROOK, Us, HasPopCnt>(pos, ei, mobility, mobilityArea);
642 bonus += evaluate_pieces<QUEEN, Us, HasPopCnt>(pos, ei, mobility, mobilityArea);
644 // Sum up all attacked squares
645 ei.attackedBy[Us][0] = ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
646 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
647 | ei.attackedBy[Us][QUEEN] | ei.attackedBy[Us][KING];
652 // evaluate_king<>() assigns bonuses and penalties to a king of a given color
654 template<Color Us, bool HasPopCnt>
655 Score evaluate_king(const Position& pos, EvalInfo& ei, Value& margin) {
657 const BitCountType Max15 = HasPopCnt ? CNT_POPCNT : CpuIs64Bit ? CNT64_MAX15 : CNT32_MAX15;
658 const Color Them = (Us == WHITE ? BLACK : WHITE);
660 Bitboard undefended, b, b1, b2, safe;
662 const Square ksq = pos.king_square(Us);
665 Score bonus = ei.pi->king_shelter<Us>(pos, ksq);
667 // King safety. This is quite complicated, and is almost certainly far
668 // from optimally tuned.
669 if ( ei.updateKingTables[Them]
670 && ei.kingAttackersCount[Them] >= 2
671 && ei.kingAdjacentZoneAttacksCount[Them])
673 // Find the attacked squares around the king which has no defenders
674 // apart from the king itself
675 undefended = ei.attackedBy[Them][0] & ei.attackedBy[Us][KING];
676 undefended &= ~( ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
677 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
678 | ei.attackedBy[Us][QUEEN]);
680 // Initialize the 'attackUnits' variable, which is used later on as an
681 // index to the KingDangerTable[] array. The initial value is based on
682 // the number and types of the enemy's attacking pieces, the number of
683 // attacked and undefended squares around our king, the square of the
684 // king, and the quality of the pawn shelter.
685 attackUnits = Min(25, (ei.kingAttackersCount[Them] * ei.kingAttackersWeight[Them]) / 2)
686 + 3 * (ei.kingAdjacentZoneAttacksCount[Them] + count_1s<Max15>(undefended))
687 + InitKingDanger[relative_square(Us, ksq)]
688 - mg_value(ei.pi->king_shelter<Us>(pos, ksq)) / 32;
690 // Analyse enemy's safe queen contact checks. First find undefended
691 // squares around the king attacked by enemy queen...
692 b = undefended & ei.attackedBy[Them][QUEEN] & ~pos.pieces_of_color(Them);
695 // ...then remove squares not supported by another enemy piece
696 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
697 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][ROOK]);
699 attackUnits += QueenContactCheckBonus
701 * (Them == pos.side_to_move() ? 2 : 1);
704 // Analyse enemy's safe rook contact checks. First find undefended
705 // squares around the king attacked by enemy rooks...
706 b = undefended & ei.attackedBy[Them][ROOK] & ~pos.pieces_of_color(Them);
708 // Consider only squares where the enemy rook gives check
709 b &= RookPseudoAttacks[ksq];
713 // ...then remove squares not supported by another enemy piece
714 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
715 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][QUEEN]);
717 attackUnits += RookContactCheckBonus
719 * (Them == pos.side_to_move() ? 2 : 1);
722 // Analyse enemy's safe distance checks for sliders and knights
723 safe = ~(pos.pieces_of_color(Them) | ei.attackedBy[Us][0]);
725 b1 = pos.attacks_from<ROOK>(ksq) & safe;
726 b2 = pos.attacks_from<BISHOP>(ksq) & safe;
728 // Enemy queen safe checks
729 b = (b1 | b2) & ei.attackedBy[Them][QUEEN];
731 attackUnits += QueenCheckBonus * count_1s<Max15>(b);
733 // Enemy rooks safe checks
734 b = b1 & ei.attackedBy[Them][ROOK];
736 attackUnits += RookCheckBonus * count_1s<Max15>(b);
738 // Enemy bishops safe checks
739 b = b2 & ei.attackedBy[Them][BISHOP];
741 attackUnits += BishopCheckBonus * count_1s<Max15>(b);
743 // Enemy knights safe checks
744 b = pos.attacks_from<KNIGHT>(ksq) & ei.attackedBy[Them][KNIGHT] & safe;
746 attackUnits += KnightCheckBonus * count_1s<Max15>(b);
748 // To index KingDangerTable[] attackUnits must be in [0, 99] range
749 attackUnits = Min(99, Max(0, attackUnits));
751 // Finally, extract the king danger score from the KingDangerTable[]
752 // array and subtract the score from evaluation. Set also margins[]
753 // value that will be used for pruning because this value can sometimes
754 // be very big, and so capturing a single attacking piece can therefore
755 // result in a score change far bigger than the value of the captured piece.
756 bonus -= KingDangerTable[Us][attackUnits];
757 if (pos.side_to_move() == Us)
758 margin += mg_value(KingDangerTable[Us][attackUnits]);
764 // evaluate_passed_pawns<>() evaluates the passed pawns of the given color
767 Score evaluate_passed_pawns(const Position& pos, EvalInfo& ei) {
769 const Color Them = (Us == WHITE ? BLACK : WHITE);
771 Score bonus = SCORE_ZERO;
772 Bitboard squaresToQueen, defendedSquares, unsafeSquares, supportingPawns;
773 Bitboard b = ei.pi->passed_pawns(Us);
779 Square s = pop_1st_bit(&b);
781 assert(pos.pawn_is_passed(Us, s));
783 int r = int(relative_rank(Us, s) - RANK_2);
784 int rr = r * (r - 1);
786 // Base bonus based on rank
787 Value mbonus = Value(20 * rr);
788 Value ebonus = Value(10 * (rr + r + 1));
792 Square blockSq = s + pawn_push(Us);
794 // Adjust bonus based on kings proximity
795 ebonus -= Value(square_distance(pos.king_square(Us), blockSq) * 3 * rr);
796 ebonus -= Value(square_distance(pos.king_square(Us), blockSq + pawn_push(Us)) * rr);
797 ebonus += Value(square_distance(pos.king_square(Them), blockSq) * 6 * rr);
799 // If the pawn is free to advance, increase bonus
800 if (pos.square_is_empty(blockSq))
802 squaresToQueen = squares_in_front_of(Us, s);
803 defendedSquares = squaresToQueen & ei.attackedBy[Us][0];
805 // If there is an enemy rook or queen attacking the pawn from behind,
806 // add all X-ray attacks by the rook or queen. Otherwise consider only
807 // the squares in the pawn's path attacked or occupied by the enemy.
808 if ( (squares_behind(Us, s) & pos.pieces(ROOK, QUEEN, Them))
809 && (squares_behind(Us, s) & pos.pieces(ROOK, QUEEN, Them) & pos.attacks_from<ROOK>(s)))
810 unsafeSquares = squaresToQueen;
812 unsafeSquares = squaresToQueen & (ei.attackedBy[Them][0] | pos.pieces_of_color(Them));
814 // If there aren't enemy attacks or pieces along the path to queen give
815 // huge bonus. Even bigger if we protect the pawn's path.
817 ebonus += Value(rr * (squaresToQueen == defendedSquares ? 17 : 15));
819 // OK, there are enemy attacks or pieces (but not pawns). Are those
820 // squares which are attacked by the enemy also attacked by us ?
821 // If yes, big bonus (but smaller than when there are no enemy attacks),
822 // if no, somewhat smaller bonus.
823 ebonus += Value(rr * ((unsafeSquares & defendedSquares) == unsafeSquares ? 13 : 8));
825 // At last, add a small bonus when there are no *friendly* pieces
826 // in the pawn's path.
827 if (!(squaresToQueen & pos.pieces_of_color(Us)))
832 // Increase the bonus if the passed pawn is supported by a friendly pawn
833 // on the same rank and a bit smaller if it's on the previous rank.
834 supportingPawns = pos.pieces(PAWN, Us) & neighboring_files_bb(s);
835 if (supportingPawns & rank_bb(s))
836 ebonus += Value(r * 20);
837 else if (supportingPawns & rank_bb(s - pawn_push(Us)))
838 ebonus += Value(r * 12);
840 // Rook pawns are a special case: They are sometimes worse, and
841 // sometimes better than other passed pawns. It is difficult to find
842 // good rules for determining whether they are good or bad. For now,
843 // we try the following: Increase the value for rook pawns if the
844 // other side has no pieces apart from a knight, and decrease the
845 // value if the other side has a rook or queen.
846 if (square_file(s) == FILE_A || square_file(s) == FILE_H)
848 if (pos.non_pawn_material(Them) <= KnightValueMidgame)
849 ebonus += ebonus / 4;
850 else if (pos.pieces(ROOK, QUEEN, Them))
851 ebonus -= ebonus / 4;
853 bonus += make_score(mbonus, ebonus);
857 // Add the scores to the middle game and endgame eval
858 return apply_weight(bonus, Weights[PassedPawns]);
862 // evaluate_space() computes the space evaluation for a given side. The
863 // space evaluation is a simple bonus based on the number of safe squares
864 // available for minor pieces on the central four files on ranks 2--4. Safe
865 // squares one, two or three squares behind a friendly pawn are counted
866 // twice. Finally, the space bonus is scaled by a weight taken from the
867 // material hash table. The aim is to improve play on game opening.
868 template<Color Us, bool HasPopCnt>
869 int evaluate_space(const Position& pos, EvalInfo& ei) {
871 const BitCountType Max15 = HasPopCnt ? CNT_POPCNT : CpuIs64Bit ? CNT64_MAX15 : CNT32_MAX15;
872 const Color Them = (Us == WHITE ? BLACK : WHITE);
874 // Find the safe squares for our pieces inside the area defined by
875 // SpaceMask[]. A square is unsafe if it is attacked by an enemy
876 // pawn, or if it is undefended and attacked by an enemy piece.
877 Bitboard safe = SpaceMask[Us]
878 & ~pos.pieces(PAWN, Us)
879 & ~ei.attackedBy[Them][PAWN]
880 & (ei.attackedBy[Us][0] | ~ei.attackedBy[Them][0]);
882 // Find all squares which are at most three squares behind some friendly pawn
883 Bitboard behind = pos.pieces(PAWN, Us);
884 behind |= (Us == WHITE ? behind >> 8 : behind << 8);
885 behind |= (Us == WHITE ? behind >> 16 : behind << 16);
887 return count_1s<Max15>(safe) + count_1s<Max15>(behind & safe);
891 // apply_weight() applies an evaluation weight to a value trying to prevent overflow
893 inline Score apply_weight(Score v, Score w) {
894 return make_score((int(mg_value(v)) * mg_value(w)) / 0x100,
895 (int(eg_value(v)) * eg_value(w)) / 0x100);
899 // scale_by_game_phase() interpolates between a middle game and an endgame score,
900 // based on game phase. It also scales the return value by a ScaleFactor array.
902 Value scale_by_game_phase(const Score& v, Phase ph, ScaleFactor sf) {
904 assert(mg_value(v) > -VALUE_INFINITE && mg_value(v) < VALUE_INFINITE);
905 assert(eg_value(v) > -VALUE_INFINITE && eg_value(v) < VALUE_INFINITE);
906 assert(ph >= PHASE_ENDGAME && ph <= PHASE_MIDGAME);
908 Value eg = eg_value(v);
909 Value ev = Value((eg * int(sf)) / SCALE_FACTOR_NORMAL);
911 int result = (mg_value(v) * int(ph) + ev * int(128 - ph)) / 128;
912 return Value(result & ~(GrainSize - 1));
916 // weight_option() computes the value of an evaluation weight, by combining
917 // two UCI-configurable weights (midgame and endgame) with an internal weight.
919 Score weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight) {
921 // Scale option value from 100 to 256
922 int mg = get_option_value_int(mgOpt) * 256 / 100;
923 int eg = get_option_value_int(egOpt) * 256 / 100;
925 return apply_weight(make_score(mg, eg), internalWeight);
929 // init_safety() initizes the king safety evaluation, based on UCI
930 // parameters. It is called from read_weights().
934 const Value MaxSlope = Value(30);
935 const Value Peak = Value(1280);
938 // First setup the base table
939 for (int i = 0; i < 100; i++)
941 t[i] = Value(int(0.4 * i * i));
944 t[i] = Min(t[i], t[i - 1] + MaxSlope);
946 t[i] = Min(t[i], Peak);
949 // Then apply the weights and get the final KingDangerTable[] array
950 for (Color c = WHITE; c <= BLACK; c++)
951 for (int i = 0; i < 100; i++)
952 KingDangerTable[c][i] = apply_weight(make_score(t[i], 0), Weights[KingDangerUs + c]);