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 // The SpaceMask[Color] contains the area of the board which is considered
172 // by the space evaluation. In the middle game, each side is given a bonus
173 // based on how many squares inside this area are safe and available for
174 // friendly minor pieces.
175 const Bitboard SpaceMask[] = {
176 (1ULL << SQ_C2) | (1ULL << SQ_D2) | (1ULL << SQ_E2) | (1ULL << SQ_F2) |
177 (1ULL << SQ_C3) | (1ULL << SQ_D3) | (1ULL << SQ_E3) | (1ULL << SQ_F3) |
178 (1ULL << SQ_C4) | (1ULL << SQ_D4) | (1ULL << SQ_E4) | (1ULL << SQ_F4),
179 (1ULL << SQ_C7) | (1ULL << SQ_D7) | (1ULL << SQ_E7) | (1ULL << SQ_F7) |
180 (1ULL << SQ_C6) | (1ULL << SQ_D6) | (1ULL << SQ_E6) | (1ULL << SQ_F6) |
181 (1ULL << SQ_C5) | (1ULL << SQ_D5) | (1ULL << SQ_E5) | (1ULL << SQ_F5)
184 // King danger constants and variables. The king danger scores are taken
185 // from the KingDangerTable[]. Various little "meta-bonuses" measuring
186 // the strength of the enemy attack are added up into an integer, which
187 // is used as an index to KingDangerTable[].
189 // KingAttackWeights[PieceType] contains king attack weights by piece type
190 const int KingAttackWeights[] = { 0, 0, 2, 2, 3, 5 };
192 // Bonuses for enemy's safe checks
193 const int QueenContactCheckBonus = 6;
194 const int RookContactCheckBonus = 4;
195 const int QueenCheckBonus = 3;
196 const int RookCheckBonus = 2;
197 const int BishopCheckBonus = 1;
198 const int KnightCheckBonus = 1;
200 // InitKingDanger[Square] contains penalties based on the position of the
201 // defending king, indexed by king's square (from white's point of view).
202 const int InitKingDanger[] = {
203 2, 0, 2, 5, 5, 2, 0, 2,
204 2, 2, 4, 8, 8, 4, 2, 2,
205 7, 10, 12, 12, 12, 12, 10, 7,
206 15, 15, 15, 15, 15, 15, 15, 15,
207 15, 15, 15, 15, 15, 15, 15, 15,
208 15, 15, 15, 15, 15, 15, 15, 15,
209 15, 15, 15, 15, 15, 15, 15, 15,
210 15, 15, 15, 15, 15, 15, 15, 15
213 // KingDangerTable[Color][attackUnits] contains the actual king danger
214 // weighted scores, indexed by color and by a calculated integer number.
215 Score KingDangerTable[2][128];
217 // Pawn and material hash tables, indexed by the current thread id.
218 // Note that they will be initialized at 0 being global variables.
219 MaterialInfoTable* MaterialTable[MAX_THREADS];
220 PawnInfoTable* PawnTable[MAX_THREADS];
222 // Function prototypes
223 template<bool HasPopCnt>
224 Value do_evaluate(const Position& pos, Value& margin);
226 template<Color Us, bool HasPopCnt>
227 void init_eval_info(const Position& pos, EvalInfo& ei);
229 template<Color Us, bool HasPopCnt>
230 Score evaluate_pieces_of_color(const Position& pos, EvalInfo& ei, Score& mobility);
232 template<Color Us, bool HasPopCnt>
233 Score evaluate_king(const Position& pos, EvalInfo& ei, Value margins[]);
236 Score evaluate_threats(const Position& pos, EvalInfo& ei);
238 template<Color Us, bool HasPopCnt>
239 int evaluate_space(const Position& pos, EvalInfo& ei);
242 Score evaluate_passed_pawns(const Position& pos, EvalInfo& ei);
244 template<bool HasPopCnt>
245 Score evaluate_unstoppable_pawns(const Position& pos, EvalInfo& ei);
247 inline Score apply_weight(Score v, Score weight);
248 Value scale_by_game_phase(const Score& v, Phase ph, ScaleFactor sf);
249 Score weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight);
259 /// Prefetches in pawn hash tables
261 void prefetchPawn(Key key, int threadID) {
263 PawnTable[threadID]->prefetch(key);
267 /// evaluate() is the main evaluation function. It always computes two
268 /// values, an endgame score and a middle game score, and interpolates
269 /// between them based on the remaining material.
270 Value evaluate(const Position& pos, Value& margin) {
272 return CpuHasPOPCNT ? do_evaluate<true>(pos, margin)
273 : do_evaluate<false>(pos, margin);
278 template<bool HasPopCnt>
279 Value do_evaluate(const Position& pos, Value& margin) {
283 Score mobilityWhite, mobilityBlack;
286 assert(pos.thread() >= 0 && pos.thread() < MAX_THREADS);
287 assert(!pos.is_check());
289 // Initialize value by reading the incrementally updated scores included
290 // in the position object (material + piece square tables).
291 Score bonus = pos.value();
293 // margins[] store the uncertainty estimation of position's evaluation
294 // that typically is used by the search for pruning decisions.
295 margins[WHITE] = margins[BLACK] = VALUE_ZERO;
297 // Probe the material hash table
298 MaterialInfo* mi = MaterialTable[pos.thread()]->get_material_info(pos);
299 bonus += mi->material_value();
301 // If we have a specialized evaluation function for the current material
302 // configuration, call it and return.
303 if (mi->specialized_eval_exists())
306 return mi->evaluate(pos);
309 // Probe the pawn hash table
310 ei.pi = PawnTable[pos.thread()]->get_pawn_info(pos);
311 bonus += apply_weight(ei.pi->pawns_value(), Weights[PawnStructure]);
313 // Initialize attack and king safety bitboards
314 init_eval_info<WHITE, HasPopCnt>(pos, ei);
315 init_eval_info<BLACK, HasPopCnt>(pos, ei);
317 // Evaluate pieces and mobility
318 bonus += evaluate_pieces_of_color<WHITE, HasPopCnt>(pos, ei, mobilityWhite)
319 - evaluate_pieces_of_color<BLACK, HasPopCnt>(pos, ei, mobilityBlack);
321 bonus += apply_weight(mobilityWhite - mobilityBlack, Weights[Mobility]);
323 // Evaluate kings after all other pieces because we need complete attack
324 // information when computing the king safety evaluation.
325 bonus += evaluate_king<WHITE, HasPopCnt>(pos, ei, margins)
326 - evaluate_king<BLACK, HasPopCnt>(pos, ei, margins);
328 // Evaluate tactical threats, we need full attack information including king
329 bonus += evaluate_threats<WHITE>(pos, ei)
330 - evaluate_threats<BLACK>(pos, ei);
332 // Evaluate passed pawns, we need full attack information including king
333 bonus += evaluate_passed_pawns<WHITE>(pos, ei)
334 - evaluate_passed_pawns<BLACK>(pos, ei);
336 // If one side has only a king, check whether exists any unstoppable passed pawn
337 if (!pos.non_pawn_material(WHITE) || !pos.non_pawn_material(BLACK))
338 bonus += evaluate_unstoppable_pawns<HasPopCnt>(pos, ei);
340 // Evaluate space for both sides, only in middle-game.
341 if (mi->space_weight())
343 int s = evaluate_space<WHITE, HasPopCnt>(pos, ei) - evaluate_space<BLACK, HasPopCnt>(pos, ei);
344 bonus += apply_weight(make_score(s * mi->space_weight(), 0), Weights[Space]);
347 // Scale winning side if position is more drawish that what it appears
348 ScaleFactor sf = eg_value(bonus) > VALUE_DRAW ? mi->scale_factor(pos, WHITE)
349 : mi->scale_factor(pos, BLACK);
350 Phase phase = mi->game_phase();
352 // If we don't already have an unusual scale factor, check for opposite
353 // colored bishop endgames, and use a lower scale for those.
354 if ( phase < PHASE_MIDGAME
355 && pos.opposite_colored_bishops()
356 && sf == SCALE_FACTOR_NORMAL)
358 // Only the two bishops ?
359 if ( pos.non_pawn_material(WHITE) == BishopValueMidgame
360 && pos.non_pawn_material(BLACK) == BishopValueMidgame)
362 // Check for KBP vs KB with only a single pawn that is almost
363 // certainly a draw or at least two pawns.
364 bool one_pawn = (pos.piece_count(WHITE, PAWN) + pos.piece_count(BLACK, PAWN) == 1);
365 sf = one_pawn ? ScaleFactor(8) : ScaleFactor(32);
368 // Endgame with opposite-colored bishops, but also other pieces. Still
369 // a bit drawish, but not as drawish as with only the two bishops.
370 sf = ScaleFactor(50);
373 // Interpolate between the middle game and the endgame score
374 margin = margins[pos.side_to_move()];
375 Value v = scale_by_game_phase(bonus, phase, sf);
376 return pos.side_to_move() == WHITE ? v : -v;
382 /// init_eval() initializes various tables used by the evaluation function
384 void init_eval(int threads) {
386 assert(threads <= MAX_THREADS);
388 for (int i = 0; i < MAX_THREADS; i++)
393 delete MaterialTable[i];
395 MaterialTable[i] = NULL;
399 PawnTable[i] = new PawnInfoTable();
401 if (!MaterialTable[i])
402 MaterialTable[i] = new MaterialInfoTable();
407 /// quit_eval() releases heap-allocated memory at program termination
415 /// read_weights() reads evaluation weights from the corresponding UCI parameters
417 void read_evaluation_uci_options(Color us) {
419 // King safety is asymmetrical. Our king danger level is weighted by
420 // "Cowardice" UCI parameter, instead the opponent one by "Aggressiveness".
421 const int kingDangerUs = (us == WHITE ? KingDangerUs : KingDangerThem);
422 const int kingDangerThem = (us == WHITE ? KingDangerThem : KingDangerUs);
424 Weights[Mobility] = weight_option("Mobility (Middle Game)", "Mobility (Endgame)", WeightsInternal[Mobility]);
425 Weights[PawnStructure] = weight_option("Pawn Structure (Middle Game)", "Pawn Structure (Endgame)", WeightsInternal[PawnStructure]);
426 Weights[PassedPawns] = weight_option("Passed Pawns (Middle Game)", "Passed Pawns (Endgame)", WeightsInternal[PassedPawns]);
427 Weights[Space] = weight_option("Space", "Space", WeightsInternal[Space]);
428 Weights[kingDangerUs] = weight_option("Cowardice", "Cowardice", WeightsInternal[KingDangerUs]);
429 Weights[kingDangerThem] = weight_option("Aggressiveness", "Aggressiveness", WeightsInternal[KingDangerThem]);
431 // If running in analysis mode, make sure we use symmetrical king safety. We do this
432 // by replacing both Weights[kingDangerUs] and Weights[kingDangerThem] by their average.
433 if (Options["UCI_AnalyseMode"].value<bool>())
434 Weights[kingDangerUs] = Weights[kingDangerThem] = (Weights[kingDangerUs] + Weights[kingDangerThem]) / 2;
442 // init_eval_info() initializes king bitboards for given color adding
443 // pawn attacks. To be done at the beginning of the evaluation.
445 template<Color Us, bool HasPopCnt>
446 void init_eval_info(const Position& pos, EvalInfo& ei) {
448 const BitCountType Max15 = HasPopCnt ? CNT_POPCNT : CpuIs64Bit ? CNT64_MAX15 : CNT32_MAX15;
449 const Color Them = (Us == WHITE ? BLACK : WHITE);
451 Bitboard b = ei.attackedBy[Them][KING] = pos.attacks_from<KING>(pos.king_square(Them));
452 ei.attackedBy[Us][PAWN] = ei.pi->pawn_attacks(Us);
454 // Init king safety tables only if we are going to use them
455 if ( pos.piece_count(Us, QUEEN)
456 && pos.non_pawn_material(Us) >= QueenValueMidgame + RookValueMidgame)
458 ei.kingZone[Us] = (b | (Us == WHITE ? b >> 8 : b << 8));
459 b &= ei.attackedBy[Us][PAWN];
460 ei.kingAttackersCount[Us] = b ? count_1s<Max15>(b) / 2 : 0;
461 ei.kingAdjacentZoneAttacksCount[Us] = ei.kingAttackersWeight[Us] = 0;
463 ei.kingZone[Us] = ei.kingAttackersCount[Us] = 0;
467 // evaluate_outposts() evaluates bishop and knight outposts squares
469 template<PieceType Piece, Color Us>
470 Score evaluate_outposts(const Position& pos, EvalInfo& ei, Square s) {
472 const Color Them = (Us == WHITE ? BLACK : WHITE);
474 assert (Piece == BISHOP || Piece == KNIGHT);
476 // Initial bonus based on square
477 Value bonus = OutpostBonus[Piece == BISHOP][relative_square(Us, s)];
479 // Increase bonus if supported by pawn, especially if the opponent has
480 // no minor piece which can exchange the outpost piece.
481 if (bonus && bit_is_set(ei.attackedBy[Us][PAWN], s))
483 if ( pos.pieces(KNIGHT, Them) == EmptyBoardBB
484 && (SquaresByColorBB[square_color(s)] & pos.pieces(BISHOP, Them)) == EmptyBoardBB)
485 bonus += bonus + bonus / 2;
489 return make_score(bonus, bonus);
493 // evaluate_pieces<>() assigns bonuses and penalties to the pieces of a given color
495 template<PieceType Piece, Color Us, bool HasPopCnt>
496 Score evaluate_pieces(const Position& pos, EvalInfo& ei, Score& mobility, Bitboard mobilityArea) {
502 Score bonus = SCORE_ZERO;
504 const BitCountType Full = HasPopCnt ? CNT_POPCNT : CpuIs64Bit ? CNT64 : CNT32;
505 const BitCountType Max15 = HasPopCnt ? CNT_POPCNT : CpuIs64Bit ? CNT64_MAX15 : CNT32_MAX15;
506 const Color Them = (Us == WHITE ? BLACK : WHITE);
507 const Square* ptr = pos.piece_list_begin(Us, Piece);
509 ei.attackedBy[Us][Piece] = EmptyBoardBB;
511 while ((s = *ptr++) != SQ_NONE)
513 // Find attacked squares, including x-ray attacks for bishops and rooks
514 if (Piece == KNIGHT || Piece == QUEEN)
515 b = pos.attacks_from<Piece>(s);
516 else if (Piece == BISHOP)
517 b = bishop_attacks_bb(s, pos.occupied_squares() & ~pos.pieces(QUEEN, Us));
518 else if (Piece == ROOK)
519 b = rook_attacks_bb(s, pos.occupied_squares() & ~pos.pieces(ROOK, QUEEN, Us));
523 // Update attack info
524 ei.attackedBy[Us][Piece] |= b;
527 if (b & ei.kingZone[Us])
529 ei.kingAttackersCount[Us]++;
530 ei.kingAttackersWeight[Us] += KingAttackWeights[Piece];
531 Bitboard bb = (b & ei.attackedBy[Them][KING]);
533 ei.kingAdjacentZoneAttacksCount[Us] += count_1s<Max15>(bb);
537 mob = (Piece != QUEEN ? count_1s<Max15>(b & mobilityArea)
538 : count_1s<Full >(b & mobilityArea));
540 mobility += MobilityBonus[Piece][mob];
542 // Decrease score if we are attacked by an enemy pawn. Remaining part
543 // of threat evaluation must be done later when we have full attack info.
544 if (bit_is_set(ei.attackedBy[Them][PAWN], s))
545 bonus -= ThreatedByPawnPenalty[Piece];
547 // Bishop and knight outposts squares
548 if ((Piece == BISHOP || Piece == KNIGHT) && pos.square_is_weak(s, Us))
549 bonus += evaluate_outposts<Piece, Us>(pos, ei, s);
551 // Queen or rook on 7th rank
552 if ( (Piece == ROOK || Piece == QUEEN)
553 && relative_rank(Us, s) == RANK_7
554 && relative_rank(Us, pos.king_square(Them)) == RANK_8)
556 bonus += (Piece == ROOK ? RookOn7thBonus : QueenOn7thBonus);
559 // Special extra evaluation for rooks
562 // Open and half-open files
564 if (ei.pi->file_is_half_open(Us, f))
566 if (ei.pi->file_is_half_open(Them, f))
567 bonus += RookOpenFileBonus;
569 bonus += RookHalfOpenFileBonus;
572 // Penalize rooks which are trapped inside a king. Penalize more if
573 // king has lost right to castle.
574 if (mob > 6 || ei.pi->file_is_half_open(Us, f))
577 ksq = pos.king_square(Us);
579 if ( square_file(ksq) >= FILE_E
580 && square_file(s) > square_file(ksq)
581 && (relative_rank(Us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
583 // Is there a half-open file between the king and the edge of the board?
584 if (!ei.pi->has_open_file_to_right(Us, square_file(ksq)))
585 bonus -= make_score(pos.can_castle(Us) ? (TrappedRookPenalty - mob * 16) / 2
586 : (TrappedRookPenalty - mob * 16), 0);
588 else if ( square_file(ksq) <= FILE_D
589 && square_file(s) < square_file(ksq)
590 && (relative_rank(Us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
592 // Is there a half-open file between the king and the edge of the board?
593 if (!ei.pi->has_open_file_to_left(Us, square_file(ksq)))
594 bonus -= make_score(pos.can_castle(Us) ? (TrappedRookPenalty - mob * 16) / 2
595 : (TrappedRookPenalty - mob * 16), 0);
603 // evaluate_threats<>() assigns bonuses according to the type of attacking piece
604 // and the type of attacked one.
607 Score evaluate_threats(const Position& pos, EvalInfo& ei) {
609 const Color Them = (Us == WHITE ? BLACK : WHITE);
612 Score bonus = SCORE_ZERO;
614 // Enemy pieces not defended by a pawn and under our attack
615 Bitboard weakEnemies = pos.pieces_of_color(Them)
616 & ~ei.attackedBy[Them][PAWN]
617 & ei.attackedBy[Us][0];
621 // Add bonus according to type of attacked enemy piece and to the
622 // type of attacking piece, from knights to queens. Kings are not
623 // considered because are already handled in king evaluation.
624 for (PieceType pt1 = KNIGHT; pt1 < KING; pt1++)
626 b = ei.attackedBy[Us][pt1] & weakEnemies;
628 for (PieceType pt2 = PAWN; pt2 < KING; pt2++)
629 if (b & pos.pieces(pt2))
630 bonus += ThreatBonus[pt1][pt2];
636 // evaluate_pieces_of_color<>() assigns bonuses and penalties to all the
637 // pieces of a given color.
639 template<Color Us, bool HasPopCnt>
640 Score evaluate_pieces_of_color(const Position& pos, EvalInfo& ei, Score& mobility) {
642 const Color Them = (Us == WHITE ? BLACK : WHITE);
644 Score bonus = mobility = SCORE_ZERO;
646 // Do not include in mobility squares protected by enemy pawns or occupied by our pieces
647 const Bitboard mobilityArea = ~(ei.attackedBy[Them][PAWN] | pos.pieces_of_color(Us));
649 bonus += evaluate_pieces<KNIGHT, Us, HasPopCnt>(pos, ei, mobility, mobilityArea);
650 bonus += evaluate_pieces<BISHOP, Us, HasPopCnt>(pos, ei, mobility, mobilityArea);
651 bonus += evaluate_pieces<ROOK, Us, HasPopCnt>(pos, ei, mobility, mobilityArea);
652 bonus += evaluate_pieces<QUEEN, Us, HasPopCnt>(pos, ei, mobility, mobilityArea);
654 // Sum up all attacked squares
655 ei.attackedBy[Us][0] = ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
656 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
657 | ei.attackedBy[Us][QUEEN] | ei.attackedBy[Us][KING];
662 // evaluate_king<>() assigns bonuses and penalties to a king of a given color
664 template<Color Us, bool HasPopCnt>
665 Score evaluate_king(const Position& pos, EvalInfo& ei, Value margins[]) {
667 const BitCountType Max15 = HasPopCnt ? CNT_POPCNT : CpuIs64Bit ? CNT64_MAX15 : CNT32_MAX15;
668 const Color Them = (Us == WHITE ? BLACK : WHITE);
670 Bitboard undefended, b, b1, b2, safe;
672 const Square ksq = pos.king_square(Us);
675 Score bonus = ei.pi->king_shelter<Us>(pos, ksq);
677 // King safety. This is quite complicated, and is almost certainly far
678 // from optimally tuned.
679 if ( ei.kingAttackersCount[Them] >= 2
680 && ei.kingAdjacentZoneAttacksCount[Them])
682 // Find the attacked squares around the king which has no defenders
683 // apart from the king itself
684 undefended = ei.attackedBy[Them][0] & ei.attackedBy[Us][KING];
685 undefended &= ~( ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
686 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
687 | ei.attackedBy[Us][QUEEN]);
689 // Initialize the 'attackUnits' variable, which is used later on as an
690 // index to the KingDangerTable[] array. The initial value is based on
691 // the number and types of the enemy's attacking pieces, the number of
692 // attacked and undefended squares around our king, the square of the
693 // king, and the quality of the pawn shelter.
694 attackUnits = Min(25, (ei.kingAttackersCount[Them] * ei.kingAttackersWeight[Them]) / 2)
695 + 3 * (ei.kingAdjacentZoneAttacksCount[Them] + count_1s<Max15>(undefended))
696 + InitKingDanger[relative_square(Us, ksq)]
697 - mg_value(ei.pi->king_shelter<Us>(pos, ksq)) / 32;
699 // Analyse enemy's safe queen contact checks. First find undefended
700 // squares around the king attacked by enemy queen...
701 b = undefended & ei.attackedBy[Them][QUEEN] & ~pos.pieces_of_color(Them);
704 // ...then remove squares not supported by another enemy piece
705 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
706 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][ROOK]);
708 attackUnits += QueenContactCheckBonus
710 * (Them == pos.side_to_move() ? 2 : 1);
713 // Analyse enemy's safe rook contact checks. First find undefended
714 // squares around the king attacked by enemy rooks...
715 b = undefended & ei.attackedBy[Them][ROOK] & ~pos.pieces_of_color(Them);
717 // Consider only squares where the enemy rook gives check
718 b &= RookPseudoAttacks[ksq];
722 // ...then remove squares not supported by another enemy piece
723 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
724 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][QUEEN]);
726 attackUnits += RookContactCheckBonus
728 * (Them == pos.side_to_move() ? 2 : 1);
731 // Analyse enemy's safe distance checks for sliders and knights
732 safe = ~(pos.pieces_of_color(Them) | ei.attackedBy[Us][0]);
734 b1 = pos.attacks_from<ROOK>(ksq) & safe;
735 b2 = pos.attacks_from<BISHOP>(ksq) & safe;
737 // Enemy queen safe checks
738 b = (b1 | b2) & ei.attackedBy[Them][QUEEN];
740 attackUnits += QueenCheckBonus * count_1s<Max15>(b);
742 // Enemy rooks safe checks
743 b = b1 & ei.attackedBy[Them][ROOK];
745 attackUnits += RookCheckBonus * count_1s<Max15>(b);
747 // Enemy bishops safe checks
748 b = b2 & ei.attackedBy[Them][BISHOP];
750 attackUnits += BishopCheckBonus * count_1s<Max15>(b);
752 // Enemy knights safe checks
753 b = pos.attacks_from<KNIGHT>(ksq) & ei.attackedBy[Them][KNIGHT] & safe;
755 attackUnits += KnightCheckBonus * count_1s<Max15>(b);
757 // To index KingDangerTable[] attackUnits must be in [0, 99] range
758 attackUnits = Min(99, Max(0, attackUnits));
760 // Finally, extract the king danger score from the KingDangerTable[]
761 // array and subtract the score from evaluation. Set also margins[]
762 // value that will be used for pruning because this value can sometimes
763 // be very big, and so capturing a single attacking piece can therefore
764 // result in a score change far bigger than the value of the captured piece.
765 bonus -= KingDangerTable[Us][attackUnits];
766 margins[Us] += mg_value(KingDangerTable[Us][attackUnits]);
772 // evaluate_passed_pawns<>() evaluates the passed pawns of the given color
775 Score evaluate_passed_pawns(const Position& pos, EvalInfo& ei) {
777 const Color Them = (Us == WHITE ? BLACK : WHITE);
779 Score bonus = SCORE_ZERO;
780 Bitboard squaresToQueen, defendedSquares, unsafeSquares, supportingPawns;
781 Bitboard b = ei.pi->passed_pawns(Us);
787 Square s = pop_1st_bit(&b);
789 assert(pos.pawn_is_passed(Us, s));
791 int r = int(relative_rank(Us, s) - RANK_2);
792 int rr = r * (r - 1);
794 // Base bonus based on rank
795 Value mbonus = Value(20 * rr);
796 Value ebonus = Value(10 * (rr + r + 1));
800 Square blockSq = s + pawn_push(Us);
802 // Adjust bonus based on kings proximity
803 ebonus -= Value(square_distance(pos.king_square(Us), blockSq) * 3 * rr);
804 ebonus -= Value(square_distance(pos.king_square(Us), blockSq + pawn_push(Us)) * rr);
805 ebonus += Value(square_distance(pos.king_square(Them), blockSq) * 6 * rr);
807 // If the pawn is free to advance, increase bonus
808 if (pos.square_is_empty(blockSq))
810 squaresToQueen = squares_in_front_of(Us, s);
811 defendedSquares = squaresToQueen & ei.attackedBy[Us][0];
813 // If there is an enemy rook or queen attacking the pawn from behind,
814 // add all X-ray attacks by the rook or queen. Otherwise consider only
815 // the squares in the pawn's path attacked or occupied by the enemy.
816 if ( (squares_behind(Us, s) & pos.pieces(ROOK, QUEEN, Them))
817 && (squares_behind(Us, s) & pos.pieces(ROOK, QUEEN, Them) & pos.attacks_from<ROOK>(s)))
818 unsafeSquares = squaresToQueen;
820 unsafeSquares = squaresToQueen & (ei.attackedBy[Them][0] | pos.pieces_of_color(Them));
822 // If there aren't enemy attacks or pieces along the path to queen give
823 // huge bonus. Even bigger if we protect the pawn's path.
825 ebonus += Value(rr * (squaresToQueen == defendedSquares ? 17 : 15));
827 // OK, there are enemy attacks or pieces (but not pawns). Are those
828 // squares which are attacked by the enemy also attacked by us ?
829 // If yes, big bonus (but smaller than when there are no enemy attacks),
830 // if no, somewhat smaller bonus.
831 ebonus += Value(rr * ((unsafeSquares & defendedSquares) == unsafeSquares ? 13 : 8));
833 // At last, add a small bonus when there are no *friendly* pieces
834 // in the pawn's path.
835 if (!(squaresToQueen & pos.pieces_of_color(Us)))
840 // Increase the bonus if the passed pawn is supported by a friendly pawn
841 // on the same rank and a bit smaller if it's on the previous rank.
842 supportingPawns = pos.pieces(PAWN, Us) & neighboring_files_bb(s);
843 if (supportingPawns & rank_bb(s))
844 ebonus += Value(r * 20);
845 else if (supportingPawns & rank_bb(s - pawn_push(Us)))
846 ebonus += Value(r * 12);
848 // Rook pawns are a special case: They are sometimes worse, and
849 // sometimes better than other passed pawns. It is difficult to find
850 // good rules for determining whether they are good or bad. For now,
851 // we try the following: Increase the value for rook pawns if the
852 // other side has no pieces apart from a knight, and decrease the
853 // value if the other side has a rook or queen.
854 if (square_file(s) == FILE_A || square_file(s) == FILE_H)
856 if (pos.non_pawn_material(Them) <= KnightValueMidgame)
857 ebonus += ebonus / 4;
858 else if (pos.pieces(ROOK, QUEEN, Them))
859 ebonus -= ebonus / 4;
861 bonus += make_score(mbonus, ebonus);
865 // Add the scores to the middle game and endgame eval
866 return apply_weight(bonus, Weights[PassedPawns]);
869 // evaluate_unstoppable_pawns() evaluates the unstoppable passed pawns for both sides
870 template<bool HasPopCnt>
871 Score evaluate_unstoppable_pawns(const Position& pos, EvalInfo& ei) {
873 const BitCountType Max15 = HasPopCnt ? CNT_POPCNT : CpuIs64Bit ? CNT64_MAX15 : CNT32_MAX15;
875 // Step 1. Hunt for unstoppable pawns. If we find at least one, record how many plies
876 // are required for promotion
877 int pliesToGo[2] = {256, 256};
879 for (Color c = WHITE; c <= BLACK; c++)
881 // Skip if other side has non-pawn pieces
882 if (pos.non_pawn_material(opposite_color(c)))
885 Bitboard b = ei.pi->passed_pawns(c);
889 Square s = pop_1st_bit(&b);
890 Square queeningSquare = relative_square(c, make_square(square_file(s), RANK_8));
892 int mtg = RANK_8 - relative_rank(c, s) - int(relative_rank(c, s) == RANK_2);
893 int oppmtg = square_distance(pos.king_square(opposite_color(c)), queeningSquare) - int(c != pos.side_to_move());
894 bool pathDefended = ((ei.attackedBy[c][0] & squares_in_front_of(c, s)) == squares_in_front_of(c, s));
896 if (mtg >= oppmtg && !pathDefended)
899 int blockerCount = count_1s<Max15>(squares_in_front_of(c, s) & pos.occupied_squares());
902 if (mtg >= oppmtg && !pathDefended)
905 int ptg = 2 * mtg - int(c == pos.side_to_move());
907 if (ptg < pliesToGo[c])
912 // Step 2. If either side cannot promote at least three plies before the other side then
913 // situation becomes too complex and we give up. Otherwise we determine the possibly "winning side"
914 if (abs(pliesToGo[WHITE] - pliesToGo[BLACK]) < 3)
915 return make_score(0, 0);
917 Color winnerSide = (pliesToGo[WHITE] < pliesToGo[BLACK] ? WHITE : BLACK);
918 Color loserSide = opposite_color(winnerSide);
920 // Step 3. Can the losing side possibly create a new passed pawn and thus prevent the loss?
921 // We collect the potential candidates in potentialBB.
922 Bitboard pawnBB = pos.pieces(PAWN, loserSide);
923 Bitboard potentialBB = pawnBB;
924 const Bitboard passedBB = ei.pi->passed_pawns(loserSide);
928 Square psq = pop_1st_bit(&pawnBB);
930 // Check direct advancement
931 int mtg = RANK_8 - relative_rank(loserSide, psq) - int(relative_rank(loserSide, psq) == RANK_2);
932 int ptg = 2 * mtg - int(loserSide == pos.side_to_move());
934 // Check if (without even considering any obstacles) we're too far away
935 if (pliesToGo[winnerSide] + 3 <= ptg)
937 clear_bit(&potentialBB, psq);
941 // If this is passed pawn, then it _may_ promote in time. We give up.
942 if (bit_is_set(passedBB, psq))
943 return make_score(0, 0);
945 // Doubled pawn is worthless
946 if (squares_in_front_of(loserSide, psq) & (pos.pieces(PAWN, loserSide)))
948 clear_bit(&potentialBB, psq);
953 // Step 4. Check new passed pawn creation through king capturing and sacrifises
954 pawnBB = potentialBB;
958 Square psq = pop_1st_bit(&pawnBB);
960 int mtg = RANK_8 - relative_rank(loserSide, psq) - int(relative_rank(loserSide, psq) == RANK_2);
961 int ptg = 2 * mtg - int(loserSide == pos.side_to_move());
963 // Generate list of obstacles
964 Bitboard obsBB = passed_pawn_mask(loserSide, psq) & pos.pieces(PAWN, winnerSide);
965 const bool pawnIsOpposed = squares_in_front_of(loserSide, psq) & obsBB;
968 // How many plies does it take to remove all the obstacles?
970 int realObsCount = 0;
971 int minKingDist = 256;
975 Square obSq = pop_1st_bit(&obsBB);
978 // Check pawns that can give support to overcome obstacle (Eg. wp: a4,b4 bp: b2. b4 is giving support)
979 if (!pawnIsOpposed && square_file(psq) != square_file(obSq))
981 Bitboard supBB = in_front_bb(winnerSide, Square(obSq + (winnerSide == WHITE ? 8 : -8)))
982 & neighboring_files_bb(psq) & potentialBB;
984 while(supBB) // This while-loop could be replaced with supSq = LSB/MSB(supBB) (depending on color)
986 Square supSq = pop_1st_bit(&supBB);
987 int dist = square_distance(obSq, supSq);
988 minMoves = Min(minMoves, dist - 2);
993 // Check pawns that can be sacrifised
994 Bitboard sacBB = passed_pawn_mask(winnerSide, obSq) & neighboring_files_bb(obSq) & potentialBB & ~(1ULL << psq);
996 while(sacBB) // This while-loop could be replaced with sacSq = LSB/MSB(sacBB) (depending on color)
998 Square sacSq = pop_1st_bit(&sacBB);
999 int dist = square_distance(obSq, sacSq);
1000 minMoves = Min(minMoves, dist - 2);
1003 // If obstacle can be destroyed with immediate pawn sacrifise, it's not real obstacle
1007 // Pawn sac calculations
1008 sacptg += minMoves * 2;
1010 // King capture calc
1012 int kingDist = square_distance(pos.king_square(loserSide), obSq);
1013 minKingDist = Min(minKingDist, kingDist);
1016 // Check if pawn sac plan _may_ save the day
1017 if (pliesToGo[winnerSide] + 3 > ptg + sacptg)
1018 return make_score(0, 0);
1020 // Check if king capture plan _may_ save the day (contains some false positives)
1021 int kingptg = (minKingDist + realObsCount) * 2;
1022 if (pliesToGo[winnerSide] + 3 > ptg + kingptg)
1023 return make_score(0, 0);
1026 // Step 5. Assign bonus
1027 const int Sign[2] = {1, -1};
1028 return Sign[winnerSide] * make_score(0, (Value) 0x500 - 0x20 * pliesToGo[winnerSide]);
1032 // evaluate_space() computes the space evaluation for a given side. The
1033 // space evaluation is a simple bonus based on the number of safe squares
1034 // available for minor pieces on the central four files on ranks 2--4. Safe
1035 // squares one, two or three squares behind a friendly pawn are counted
1036 // twice. Finally, the space bonus is scaled by a weight taken from the
1037 // material hash table. The aim is to improve play on game opening.
1038 template<Color Us, bool HasPopCnt>
1039 int evaluate_space(const Position& pos, EvalInfo& ei) {
1041 const BitCountType Max15 = HasPopCnt ? CNT_POPCNT : CpuIs64Bit ? CNT64_MAX15 : CNT32_MAX15;
1042 const Color Them = (Us == WHITE ? BLACK : WHITE);
1044 // Find the safe squares for our pieces inside the area defined by
1045 // SpaceMask[]. A square is unsafe if it is attacked by an enemy
1046 // pawn, or if it is undefended and attacked by an enemy piece.
1047 Bitboard safe = SpaceMask[Us]
1048 & ~pos.pieces(PAWN, Us)
1049 & ~ei.attackedBy[Them][PAWN]
1050 & (ei.attackedBy[Us][0] | ~ei.attackedBy[Them][0]);
1052 // Find all squares which are at most three squares behind some friendly pawn
1053 Bitboard behind = pos.pieces(PAWN, Us);
1054 behind |= (Us == WHITE ? behind >> 8 : behind << 8);
1055 behind |= (Us == WHITE ? behind >> 16 : behind << 16);
1057 return count_1s<Max15>(safe) + count_1s<Max15>(behind & safe);
1061 // apply_weight() applies an evaluation weight to a value trying to prevent overflow
1063 inline Score apply_weight(Score v, Score w) {
1064 return make_score((int(mg_value(v)) * mg_value(w)) / 0x100,
1065 (int(eg_value(v)) * eg_value(w)) / 0x100);
1069 // scale_by_game_phase() interpolates between a middle game and an endgame score,
1070 // based on game phase. It also scales the return value by a ScaleFactor array.
1072 Value scale_by_game_phase(const Score& v, Phase ph, ScaleFactor sf) {
1074 assert(mg_value(v) > -VALUE_INFINITE && mg_value(v) < VALUE_INFINITE);
1075 assert(eg_value(v) > -VALUE_INFINITE && eg_value(v) < VALUE_INFINITE);
1076 assert(ph >= PHASE_ENDGAME && ph <= PHASE_MIDGAME);
1078 Value eg = eg_value(v);
1079 Value ev = Value((eg * int(sf)) / SCALE_FACTOR_NORMAL);
1081 int result = (mg_value(v) * int(ph) + ev * int(128 - ph)) / 128;
1082 return Value(result & ~(GrainSize - 1));
1086 // weight_option() computes the value of an evaluation weight, by combining
1087 // two UCI-configurable weights (midgame and endgame) with an internal weight.
1089 Score weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight) {
1091 // Scale option value from 100 to 256
1092 int mg = Options[mgOpt].value<int>() * 256 / 100;
1093 int eg = Options[egOpt].value<int>() * 256 / 100;
1095 return apply_weight(make_score(mg, eg), internalWeight);
1099 // init_safety() initizes the king safety evaluation, based on UCI
1100 // parameters. It is called from read_weights().
1102 void init_safety() {
1104 const Value MaxSlope = Value(30);
1105 const Value Peak = Value(1280);
1108 // First setup the base table
1109 for (int i = 0; i < 100; i++)
1111 t[i] = Value(int(0.4 * i * i));
1114 t[i] = Min(t[i], t[i - 1] + MaxSlope);
1116 t[i] = Min(t[i], Peak);
1119 // Then apply the weights and get the final KingDangerTable[] array
1120 for (Color c = WHITE; c <= BLACK; c++)
1121 for (int i = 0; i < 100; i++)
1122 KingDangerTable[c][i] = apply_weight(make_score(t[i], 0), Weights[KingDangerUs + c]);