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 Phase phase = mi->game_phase();
336 // Evaluate space for both sides, only in middle-game.
337 if (phase > PHASE_ENDGAME && mi->space_weight() > 0)
339 int s = evaluate_space<WHITE, HasPopCnt>(pos, ei) - evaluate_space<BLACK, HasPopCnt>(pos, ei);
340 bonus += apply_weight(make_score(s * mi->space_weight(), 0), Weights[Space]);
343 // Scale winning side if position is more drawish that what it appears
344 ScaleFactor sf = eg_value(bonus) > VALUE_ZERO ? mi->scale_factor(pos, WHITE)
345 : mi->scale_factor(pos, BLACK);
347 // If we don't already have an unusual scale factor, check for opposite
348 // colored bishop endgames, and use a lower scale for those.
349 if ( phase < PHASE_MIDGAME
350 && pos.opposite_colored_bishops()
351 && sf == SCALE_FACTOR_NORMAL)
353 // Only the two bishops ?
354 if ( pos.non_pawn_material(WHITE) == BishopValueMidgame
355 && pos.non_pawn_material(BLACK) == BishopValueMidgame)
357 // Check for KBP vs KB with only a single pawn that is almost
358 // certainly a draw or at least two pawns.
359 bool one_pawn = (pos.piece_count(WHITE, PAWN) + pos.piece_count(BLACK, PAWN) == 1);
360 sf = one_pawn ? ScaleFactor(8) : ScaleFactor(32);
363 // Endgame with opposite-colored bishops, but also other pieces. Still
364 // a bit drawish, but not as drawish as with only the two bishops.
365 sf = ScaleFactor(50);
368 // Interpolate between the middle game and the endgame score
369 Value v = scale_by_game_phase(bonus, phase, sf);
370 return pos.side_to_move() == WHITE ? v : -v;
376 /// init_eval() initializes various tables used by the evaluation function
378 void init_eval(int threads) {
380 assert(threads <= MAX_THREADS);
382 for (int i = 0; i < MAX_THREADS; i++)
387 delete MaterialTable[i];
389 MaterialTable[i] = NULL;
393 PawnTable[i] = new PawnInfoTable();
395 if (!MaterialTable[i])
396 MaterialTable[i] = new MaterialInfoTable();
401 /// quit_eval() releases heap-allocated memory at program termination
409 /// read_weights() reads evaluation weights from the corresponding UCI parameters
411 void read_weights(Color us) {
413 // King safety is asymmetrical. Our king danger level is weighted by
414 // "Cowardice" UCI parameter, instead the opponent one by "Aggressiveness".
415 const int kingDangerUs = (us == WHITE ? KingDangerUs : KingDangerThem);
416 const int kingDangerThem = (us == WHITE ? KingDangerThem : KingDangerUs);
418 Weights[Mobility] = weight_option("Mobility (Middle Game)", "Mobility (Endgame)", WeightsInternal[Mobility]);
419 Weights[PawnStructure] = weight_option("Pawn Structure (Middle Game)", "Pawn Structure (Endgame)", WeightsInternal[PawnStructure]);
420 Weights[PassedPawns] = weight_option("Passed Pawns (Middle Game)", "Passed Pawns (Endgame)", WeightsInternal[PassedPawns]);
421 Weights[Space] = weight_option("Space", "Space", WeightsInternal[Space]);
422 Weights[kingDangerUs] = weight_option("Cowardice", "Cowardice", WeightsInternal[KingDangerUs]);
423 Weights[kingDangerThem] = weight_option("Aggressiveness", "Aggressiveness", WeightsInternal[KingDangerThem]);
425 // If running in analysis mode, make sure we use symmetrical king safety. We do this
426 // by replacing both Weights[kingDangerUs] and Weights[kingDangerThem] by their average.
427 if (get_option_value_bool("UCI_AnalyseMode"))
428 Weights[kingDangerUs] = Weights[kingDangerThem] = (Weights[kingDangerUs] + Weights[kingDangerThem]) / 2;
436 // init_eval_info() initializes king bitboards for given color adding
437 // pawn attacks. To be done at the beginning of the evaluation.
439 template<Color Us, bool HasPopCnt>
440 void init_eval_info(const Position& pos, EvalInfo& ei) {
442 const BitCountType Max15 = HasPopCnt ? CNT_POPCNT : CpuIs64Bit ? CNT64_MAX15 : CNT32_MAX15;
443 const Color Them = (Us == WHITE ? BLACK : WHITE);
445 Bitboard b = ei.attackedBy[Them][KING] = pos.attacks_from<KING>(pos.king_square(Them));
446 ei.kingZone[Us] = (b | (Us == WHITE ? b >> 8 : b << 8));
447 ei.attackedBy[Us][PAWN] = ei.pi->pawn_attacks(Us);
448 ei.updateKingTables[Us] = pos.piece_count(Us, QUEEN) && pos.non_pawn_material(Us) >= QueenValueMidgame + RookValueMidgame;
449 if (ei.updateKingTables[Us])
451 b &= ei.attackedBy[Us][PAWN];
452 ei.kingAttackersCount[Us] = b ? count_1s<Max15>(b) / 2 : EmptyBoardBB;
453 ei.kingAdjacentZoneAttacksCount[Us] = ei.kingAttackersWeight[Us] = EmptyBoardBB;
458 // evaluate_outposts() evaluates bishop and knight outposts squares
460 template<PieceType Piece, Color Us>
461 Score evaluate_outposts(const Position& pos, EvalInfo& ei, Square s) {
463 const Color Them = (Us == WHITE ? BLACK : WHITE);
465 assert (Piece == BISHOP || Piece == KNIGHT);
467 // Initial bonus based on square
468 Value bonus = OutpostBonus[Piece == BISHOP][relative_square(Us, s)];
470 // Increase bonus if supported by pawn, especially if the opponent has
471 // no minor piece which can exchange the outpost piece.
472 if (bonus && bit_is_set(ei.attackedBy[Us][PAWN], s))
474 if ( pos.pieces(KNIGHT, Them) == EmptyBoardBB
475 && (SquaresByColorBB[square_color(s)] & pos.pieces(BISHOP, Them)) == EmptyBoardBB)
476 bonus += bonus + bonus / 2;
480 return make_score(bonus, bonus);
484 // evaluate_pieces<>() assigns bonuses and penalties to the pieces of a given color
486 template<PieceType Piece, Color Us, bool HasPopCnt>
487 Score evaluate_pieces(const Position& pos, EvalInfo& ei, Score& mobility, Bitboard mobilityArea) {
493 Score bonus = SCORE_ZERO;
495 const BitCountType Full = HasPopCnt ? CNT_POPCNT : CpuIs64Bit ? CNT64 : CNT32;
496 const BitCountType Max15 = HasPopCnt ? CNT_POPCNT : CpuIs64Bit ? CNT64_MAX15 : CNT32_MAX15;
497 const Color Them = (Us == WHITE ? BLACK : WHITE);
498 const Square* ptr = pos.piece_list_begin(Us, Piece);
500 ei.attackedBy[Us][Piece] = EmptyBoardBB;
502 while ((s = *ptr++) != SQ_NONE)
504 // Find attacked squares, including x-ray attacks for bishops and rooks
505 if (Piece == KNIGHT || Piece == QUEEN)
506 b = pos.attacks_from<Piece>(s);
507 else if (Piece == BISHOP)
508 b = bishop_attacks_bb(s, pos.occupied_squares() & ~pos.pieces(QUEEN, Us));
509 else if (Piece == ROOK)
510 b = rook_attacks_bb(s, pos.occupied_squares() & ~pos.pieces(ROOK, QUEEN, Us));
514 // Update attack info
515 ei.attackedBy[Us][Piece] |= b;
518 if (ei.updateKingTables[Us] && (b & ei.kingZone[Us]))
520 ei.kingAttackersCount[Us]++;
521 ei.kingAttackersWeight[Us] += KingAttackWeights[Piece];
522 Bitboard bb = (b & ei.attackedBy[Them][KING]);
524 ei.kingAdjacentZoneAttacksCount[Us] += count_1s<Max15>(bb);
528 mob = (Piece != QUEEN ? count_1s<Max15>(b & mobilityArea)
529 : count_1s<Full >(b & mobilityArea));
531 mobility += MobilityBonus[Piece][mob];
533 // Decrease score if we are attacked by an enemy pawn. Remaining part
534 // of threat evaluation must be done later when we have full attack info.
535 if (bit_is_set(ei.attackedBy[Them][PAWN], s))
536 bonus -= ThreatedByPawnPenalty[Piece];
538 // Bishop and knight outposts squares
539 if ((Piece == BISHOP || Piece == KNIGHT) && pos.square_is_weak(s, Us))
540 bonus += evaluate_outposts<Piece, Us>(pos, ei, s);
542 // Queen or rook on 7th rank
543 if ( (Piece == ROOK || Piece == QUEEN)
544 && relative_rank(Us, s) == RANK_7
545 && relative_rank(Us, pos.king_square(Them)) == RANK_8)
547 bonus += (Piece == ROOK ? RookOn7thBonus : QueenOn7thBonus);
550 // Special extra evaluation for rooks
553 // Open and half-open files
555 if (ei.pi->file_is_half_open(Us, f))
557 if (ei.pi->file_is_half_open(Them, f))
558 bonus += RookOpenFileBonus;
560 bonus += RookHalfOpenFileBonus;
563 // Penalize rooks which are trapped inside a king. Penalize more if
564 // king has lost right to castle.
565 if (mob > 6 || ei.pi->file_is_half_open(Us, f))
568 ksq = pos.king_square(Us);
570 if ( square_file(ksq) >= FILE_E
571 && square_file(s) > square_file(ksq)
572 && (relative_rank(Us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
574 // Is there a half-open file between the king and the edge of the board?
575 if (!ei.pi->has_open_file_to_right(Us, square_file(ksq)))
576 bonus -= make_score(pos.can_castle(Us) ? (TrappedRookPenalty - mob * 16) / 2
577 : (TrappedRookPenalty - mob * 16), 0);
579 else if ( square_file(ksq) <= FILE_D
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_left(Us, square_file(ksq)))
585 bonus -= make_score(pos.can_castle(Us) ? (TrappedRookPenalty - mob * 16) / 2
586 : (TrappedRookPenalty - mob * 16), 0);
594 // evaluate_threats<>() assigns bonuses according to the type of attacking piece
595 // and the type of attacked one.
598 Score evaluate_threats(const Position& pos, EvalInfo& ei) {
600 const Color Them = (Us == WHITE ? BLACK : WHITE);
603 Score bonus = SCORE_ZERO;
605 // Enemy pieces not defended by a pawn and under our attack
606 Bitboard weakEnemies = pos.pieces_of_color(Them)
607 & ~ei.attackedBy[Them][PAWN]
608 & ei.attackedBy[Us][0];
612 // Add bonus according to type of attacked enemy piece and to the
613 // type of attacking piece, from knights to queens. Kings are not
614 // considered because are already handled in king evaluation.
615 for (PieceType pt1 = KNIGHT; pt1 < KING; pt1++)
617 b = ei.attackedBy[Us][pt1] & weakEnemies;
619 for (PieceType pt2 = PAWN; pt2 < KING; pt2++)
620 if (b & pos.pieces(pt2))
621 bonus += ThreatBonus[pt1][pt2];
627 // evaluate_pieces_of_color<>() assigns bonuses and penalties to all the
628 // pieces of a given color.
630 template<Color Us, bool HasPopCnt>
631 Score evaluate_pieces_of_color(const Position& pos, EvalInfo& ei, Score& mobility) {
633 const Color Them = (Us == WHITE ? BLACK : WHITE);
635 Score bonus = mobility = SCORE_ZERO;
637 // Do not include in mobility squares protected by enemy pawns or occupied by our pieces
638 const Bitboard mobilityArea = ~(ei.attackedBy[Them][PAWN] | pos.pieces_of_color(Us));
640 bonus += evaluate_pieces<KNIGHT, Us, HasPopCnt>(pos, ei, mobility, mobilityArea);
641 bonus += evaluate_pieces<BISHOP, Us, HasPopCnt>(pos, ei, mobility, mobilityArea);
642 bonus += evaluate_pieces<ROOK, Us, HasPopCnt>(pos, ei, mobility, mobilityArea);
643 bonus += evaluate_pieces<QUEEN, Us, HasPopCnt>(pos, ei, mobility, mobilityArea);
645 // Sum up all attacked squares
646 ei.attackedBy[Us][0] = ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
647 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
648 | ei.attackedBy[Us][QUEEN] | ei.attackedBy[Us][KING];
653 // evaluate_king<>() assigns bonuses and penalties to a king of a given color
655 template<Color Us, bool HasPopCnt>
656 Score evaluate_king(const Position& pos, EvalInfo& ei, Value& margin) {
658 const BitCountType Max15 = HasPopCnt ? CNT_POPCNT : CpuIs64Bit ? CNT64_MAX15 : CNT32_MAX15;
659 const Color Them = (Us == WHITE ? BLACK : WHITE);
661 Bitboard undefended, b, b1, b2, safe;
663 const Square ksq = pos.king_square(Us);
666 Score bonus = ei.pi->king_shelter<Us>(pos, ksq);
668 // King safety. This is quite complicated, and is almost certainly far
669 // from optimally tuned.
670 if ( ei.updateKingTables[Them]
671 && ei.kingAttackersCount[Them] >= 2
672 && ei.kingAdjacentZoneAttacksCount[Them])
674 // Find the attacked squares around the king which has no defenders
675 // apart from the king itself
676 undefended = ei.attackedBy[Them][0] & ei.attackedBy[Us][KING];
677 undefended &= ~( ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
678 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
679 | ei.attackedBy[Us][QUEEN]);
681 // Initialize the 'attackUnits' variable, which is used later on as an
682 // index to the KingDangerTable[] array. The initial value is based on
683 // the number and types of the enemy's attacking pieces, the number of
684 // attacked and undefended squares around our king, the square of the
685 // king, and the quality of the pawn shelter.
686 attackUnits = Min(25, (ei.kingAttackersCount[Them] * ei.kingAttackersWeight[Them]) / 2)
687 + 3 * (ei.kingAdjacentZoneAttacksCount[Them] + count_1s<Max15>(undefended))
688 + InitKingDanger[relative_square(Us, ksq)]
689 - mg_value(ei.pi->king_shelter<Us>(pos, ksq)) / 32;
691 // Analyse enemy's safe queen contact checks. First find undefended
692 // squares around the king attacked by enemy queen...
693 b = undefended & ei.attackedBy[Them][QUEEN] & ~pos.pieces_of_color(Them);
696 // ...then remove squares not supported by another enemy piece
697 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
698 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][ROOK]);
700 attackUnits += QueenContactCheckBonus
702 * (Them == pos.side_to_move() ? 2 : 1);
705 // Analyse enemy's safe rook contact checks. First find undefended
706 // squares around the king attacked by enemy rooks...
707 b = undefended & ei.attackedBy[Them][ROOK] & ~pos.pieces_of_color(Them);
709 // Consider only squares where the enemy rook gives check
710 b &= RookPseudoAttacks[ksq];
714 // ...then remove squares not supported by another enemy piece
715 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
716 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][QUEEN]);
718 attackUnits += RookContactCheckBonus
720 * (Them == pos.side_to_move() ? 2 : 1);
723 // Analyse enemy's safe distance checks for sliders and knights
724 safe = ~(pos.pieces_of_color(Them) | ei.attackedBy[Us][0]);
726 b1 = pos.attacks_from<ROOK>(ksq) & safe;
727 b2 = pos.attacks_from<BISHOP>(ksq) & safe;
729 // Enemy queen safe checks
730 b = (b1 | b2) & ei.attackedBy[Them][QUEEN];
732 attackUnits += QueenCheckBonus * count_1s<Max15>(b);
734 // Enemy rooks safe checks
735 b = b1 & ei.attackedBy[Them][ROOK];
737 attackUnits += RookCheckBonus * count_1s<Max15>(b);
739 // Enemy bishops safe checks
740 b = b2 & ei.attackedBy[Them][BISHOP];
742 attackUnits += BishopCheckBonus * count_1s<Max15>(b);
744 // Enemy knights safe checks
745 b = pos.attacks_from<KNIGHT>(ksq) & ei.attackedBy[Them][KNIGHT] & safe;
747 attackUnits += KnightCheckBonus * count_1s<Max15>(b);
749 // To index KingDangerTable[] attackUnits must be in [0, 99] range
750 attackUnits = Min(99, Max(0, attackUnits));
752 // Finally, extract the king danger score from the KingDangerTable[]
753 // array and subtract the score from evaluation. Set also margins[]
754 // value that will be used for pruning because this value can sometimes
755 // be very big, and so capturing a single attacking piece can therefore
756 // result in a score change far bigger than the value of the captured piece.
757 bonus -= KingDangerTable[Us][attackUnits];
758 if (pos.side_to_move() == Us)
759 margin += mg_value(KingDangerTable[Us][attackUnits]);
765 // evaluate_passed_pawns<>() evaluates the passed pawns of the given color
768 Score evaluate_passed_pawns(const Position& pos, EvalInfo& ei) {
770 const Color Them = (Us == WHITE ? BLACK : WHITE);
772 Score bonus = SCORE_ZERO;
773 Bitboard squaresToQueen, defendedSquares, unsafeSquares, supportingPawns;
774 Bitboard b = ei.pi->passed_pawns(Us);
780 Square s = pop_1st_bit(&b);
782 assert(pos.pawn_is_passed(Us, s));
784 int r = int(relative_rank(Us, s) - RANK_2);
785 int rr = r * (r - 1);
787 // Base bonus based on rank
788 Value mbonus = Value(20 * rr);
789 Value ebonus = Value(10 * (rr + r + 1));
793 Square blockSq = s + pawn_push(Us);
795 // Adjust bonus based on kings proximity
796 ebonus -= Value(square_distance(pos.king_square(Us), blockSq) * 3 * rr);
797 ebonus -= Value(square_distance(pos.king_square(Us), blockSq + pawn_push(Us)) * rr);
798 ebonus += Value(square_distance(pos.king_square(Them), blockSq) * 6 * rr);
800 // If the pawn is free to advance, increase bonus
801 if (pos.square_is_empty(blockSq))
803 squaresToQueen = squares_in_front_of(Us, s);
804 defendedSquares = squaresToQueen & ei.attackedBy[Us][0];
806 // If there is an enemy rook or queen attacking the pawn from behind,
807 // add all X-ray attacks by the rook or queen. Otherwise consider only
808 // the squares in the pawn's path attacked or occupied by the enemy.
809 if ( (squares_behind(Us, s) & pos.pieces(ROOK, QUEEN, Them))
810 && (squares_behind(Us, s) & pos.pieces(ROOK, QUEEN, Them) & pos.attacks_from<ROOK>(s)))
811 unsafeSquares = squaresToQueen;
813 unsafeSquares = squaresToQueen & (ei.attackedBy[Them][0] | pos.pieces_of_color(Them));
815 // If there aren't enemy attacks or pieces along the path to queen give
816 // huge bonus. Even bigger if we protect the pawn's path.
818 ebonus += Value(rr * (squaresToQueen == defendedSquares ? 17 : 15));
820 // OK, there are enemy attacks or pieces (but not pawns). Are those
821 // squares which are attacked by the enemy also attacked by us ?
822 // If yes, big bonus (but smaller than when there are no enemy attacks),
823 // if no, somewhat smaller bonus.
824 ebonus += Value(rr * ((unsafeSquares & defendedSquares) == unsafeSquares ? 13 : 8));
826 // At last, add a small bonus when there are no *friendly* pieces
827 // in the pawn's path.
828 if (!(squaresToQueen & pos.pieces_of_color(Us)))
833 // Increase the bonus if the passed pawn is supported by a friendly pawn
834 // on the same rank and a bit smaller if it's on the previous rank.
835 supportingPawns = pos.pieces(PAWN, Us) & neighboring_files_bb(s);
836 if (supportingPawns & rank_bb(s))
837 ebonus += Value(r * 20);
838 else if (supportingPawns & rank_bb(s - pawn_push(Us)))
839 ebonus += Value(r * 12);
841 // Rook pawns are a special case: They are sometimes worse, and
842 // sometimes better than other passed pawns. It is difficult to find
843 // good rules for determining whether they are good or bad. For now,
844 // we try the following: Increase the value for rook pawns if the
845 // other side has no pieces apart from a knight, and decrease the
846 // value if the other side has a rook or queen.
847 if (square_file(s) == FILE_A || square_file(s) == FILE_H)
849 if (pos.non_pawn_material(Them) <= KnightValueMidgame)
850 ebonus += ebonus / 4;
851 else if (pos.pieces(ROOK, QUEEN, Them))
852 ebonus -= ebonus / 4;
854 bonus += make_score(mbonus, ebonus);
858 // Add the scores to the middle game and endgame eval
859 return apply_weight(bonus, Weights[PassedPawns]);
863 // evaluate_space() computes the space evaluation for a given side. The
864 // space evaluation is a simple bonus based on the number of safe squares
865 // available for minor pieces on the central four files on ranks 2--4. Safe
866 // squares one, two or three squares behind a friendly pawn are counted
867 // twice. Finally, the space bonus is scaled by a weight taken from the
868 // material hash table. The aim is to improve play on game opening.
869 template<Color Us, bool HasPopCnt>
870 int evaluate_space(const Position& pos, EvalInfo& ei) {
872 const BitCountType Max15 = HasPopCnt ? CNT_POPCNT : CpuIs64Bit ? CNT64_MAX15 : CNT32_MAX15;
873 const Color Them = (Us == WHITE ? BLACK : WHITE);
875 // Find the safe squares for our pieces inside the area defined by
876 // SpaceMask[]. A square is unsafe if it is attacked by an enemy
877 // pawn, or if it is undefended and attacked by an enemy piece.
878 Bitboard safe = SpaceMask[Us]
879 & ~pos.pieces(PAWN, Us)
880 & ~ei.attackedBy[Them][PAWN]
881 & (ei.attackedBy[Us][0] | ~ei.attackedBy[Them][0]);
883 // Find all squares which are at most three squares behind some friendly pawn
884 Bitboard behind = pos.pieces(PAWN, Us);
885 behind |= (Us == WHITE ? behind >> 8 : behind << 8);
886 behind |= (Us == WHITE ? behind >> 16 : behind << 16);
888 return count_1s<Max15>(safe) + count_1s<Max15>(behind & safe);
892 // apply_weight() applies an evaluation weight to a value trying to prevent overflow
894 inline Score apply_weight(Score v, Score w) {
895 return make_score((int(mg_value(v)) * mg_value(w)) / 0x100,
896 (int(eg_value(v)) * eg_value(w)) / 0x100);
900 // scale_by_game_phase() interpolates between a middle game and an endgame score,
901 // based on game phase. It also scales the return value by a ScaleFactor array.
903 Value scale_by_game_phase(const Score& v, Phase ph, ScaleFactor sf) {
905 assert(mg_value(v) > -VALUE_INFINITE && mg_value(v) < VALUE_INFINITE);
906 assert(eg_value(v) > -VALUE_INFINITE && eg_value(v) < VALUE_INFINITE);
907 assert(ph >= PHASE_ENDGAME && ph <= PHASE_MIDGAME);
909 Value eg = eg_value(v);
910 Value ev = Value((eg * int(sf)) / SCALE_FACTOR_NORMAL);
912 int result = (mg_value(v) * int(ph) + ev * int(128 - ph)) / 128;
913 return Value(result & ~(GrainSize - 1));
917 // weight_option() computes the value of an evaluation weight, by combining
918 // two UCI-configurable weights (midgame and endgame) with an internal weight.
920 Score weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight) {
922 // Scale option value from 100 to 256
923 int mg = get_option_value_int(mgOpt) * 256 / 100;
924 int eg = get_option_value_int(egOpt) * 256 / 100;
926 return apply_weight(make_score(mg, eg), internalWeight);
930 // init_safety() initizes the king safety evaluation, based on UCI
931 // parameters. It is called from read_weights().
935 const Value MaxSlope = Value(30);
936 const Value Peak = Value(1280);
939 // First setup the base table
940 for (int i = 0; i < 100; i++)
942 t[i] = Value(int(0.4 * i * i));
945 t[i] = Min(t[i], t[i - 1] + MaxSlope);
947 t[i] = Min(t[i], Peak);
950 // Then apply the weights and get the final KingDangerTable[] array
951 for (Color c = WHITE; c <= BLACK; c++)
952 for (int i = 0; i < 100; i++)
953 KingDangerTable[c][i] = apply_weight(make_score(t[i], 0), Weights[KingDangerUs + c]);