2 Stockfish, a UCI chess playing engine derived from Glaurung 2.1
3 Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
4 Copyright (C) 2008-2015 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/>.
22 #include <cstring> // For std::memset
35 enum Term { // First 8 entries are for PieceType
36 MATERIAL = 8, IMBALANCE, MOBILITY, THREAT, PASSED, SPACE, TOTAL, TERM_NB
39 Score scores[COLOR_NB][TERM_NB];
41 std::ostream& operator<<(std::ostream& os, Term idx);
43 double to_cp(Value v);
44 void write(int idx, Color c, Score s);
45 void write(int idx, Score w, Score b = SCORE_ZERO);
46 std::string do_trace(const Position& pos);
50 // Struct EvalInfo contains various information computed and collected
51 // by the evaluation functions.
54 // Pointers to material and pawn hash table entries
58 // attackedBy[color][piece type] is a bitboard representing all squares
59 // attacked by a given color and piece type, attackedBy[color][ALL_PIECES]
60 // contains all squares attacked by the given color.
61 Bitboard attackedBy[COLOR_NB][PIECE_TYPE_NB];
63 // kingRing[color] is the zone around the king which is considered
64 // by the king safety evaluation. This consists of the squares directly
65 // adjacent to the king, and the three (or two, for a king on an edge file)
66 // squares two ranks in front of the king. For instance, if black's king
67 // is on g8, kingRing[BLACK] is a bitboard containing the squares f8, h8,
68 // f7, g7, h7, f6, g6 and h6.
69 Bitboard kingRing[COLOR_NB];
71 // kingAttackersCount[color] is the number of pieces of the given color
72 // which attack a square in the kingRing of the enemy king.
73 int kingAttackersCount[COLOR_NB];
75 // kingAttackersWeight[color] is the sum of the "weight" of the pieces of the
76 // given color which attack a square in the kingRing of the enemy king. The
77 // weights of the individual piece types are given by the elements in the
78 // KingAttackWeights array.
79 int kingAttackersWeight[COLOR_NB];
81 // kingAdjacentZoneAttacksCount[color] is the number of attacks by the given
82 // color to squares directly adjacent to the enemy king. Pieces which attack
83 // more than one square are counted multiple times. For instance, if there is
84 // a white knight on g5 and black's king is on g8, this white knight adds 2
85 // to kingAdjacentZoneAttacksCount[WHITE].
86 int kingAdjacentZoneAttacksCount[COLOR_NB];
88 Bitboard pinnedPieces[COLOR_NB];
92 // Evaluation weights, indexed by the corresponding evaluation term
93 enum { Mobility, PawnStructure, PassedPawns, Space, KingSafety };
95 const struct Weight { int mg, eg; } Weights[] = {
96 {289, 344}, {233, 201}, {221, 273}, {46, 0}, {322, 0}
99 Score operator*(Score s, const Weight& w) {
100 return make_score(mg_value(s) * w.mg / 256, eg_value(s) * w.eg / 256);
104 #define V(v) Value(v)
105 #define S(mg, eg) make_score(mg, eg)
107 // MobilityBonus[PieceType][attacked] contains bonuses for middle and end
108 // game, indexed by piece type and number of attacked squares not occupied by
110 const Score MobilityBonus[][32] = {
112 { S(-68,-49), S(-46,-33), S(-3,-12), S( 5, -4), S( 9, 11), S(15, 16), // Knights
113 S( 23, 27), S( 33, 28), S(37, 29) },
114 { S(-49,-44), S(-23,-16), S(16, 1), S(29, 16), S(40, 25), S(51, 34), // Bishops
115 S( 55, 43), S( 61, 49), S(64, 51), S(68, 52), S(73, 55), S(75, 60),
116 S( 80, 65), S( 86, 66) },
117 { S(-50,-57), S(-28,-22), S(-11, 7), S(-1, 29), S( 0, 39), S( 1, 46), // Rooks
118 S( 10, 66), S( 16, 79), S(22, 86), S(23,103), S(30,109), S(33,111),
119 S( 37,115), S( 38,119), S(48,124) },
120 { S(-43,-30), S(-27,-15), S( 1, -5), S( 2, -3), S(14, 10), S(18, 24), // Queens
121 S( 20, 27), S( 33, 37), S(33, 38), S(34, 43), S(40, 46), S(43, 56),
122 S( 46, 61), S( 52, 63), S(52, 63), S(57, 65), S(60, 70), S(61, 74),
123 S( 67, 80), S( 76, 82), S(77, 88), S(82, 94), S(86, 95), S(90, 96),
124 S( 94, 99), S( 96,100), S(99,111), S(99,112) }
127 // Outpost[Bishop/Knight][Square] contains bonuses for knights and bishops
128 // outposts, indexed by piece type and square (from white's point of view).
129 const Value Outpost[][SQUARE_NB] = {
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(3), V(9), V(9), V(3), V(0), V(0),
134 V(0), V(4),V(18),V(25),V(25),V(18), V(4), V(0),
135 V(4), V(9),V(29),V(38),V(38),V(29), V(9), V(4),
136 V(2), V(9),V(19),V(15),V(15),V(19), V(9), V(2) },
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(2), V(4), V(3), V(8), V(8), V(3), V(4), V(2),
141 V(1), V(9), V(9),V(13),V(13), V(9), V(9), V(1),
142 V(2), V(8),V(21),V(24),V(24),V(21), V(8), V(2),
143 V(0), V(4), V(6), V(6), V(6), V(6), V(4), V(0) }
146 // Threat[defended/weak][minor/major attacking][attacked PieceType] contains
147 // bonuses according to which piece type attacks which one.
148 const Score Threat[][2][PIECE_TYPE_NB] = {
149 { { S(0, 0), S( 0, 0), S(19, 37), S(24, 37), S(44, 97), S(35,106) }, // Defended Minor
150 { S(0, 0), S( 0, 0), S( 9, 14), S( 9, 14), S( 7, 14), S(24, 48) } }, // Defended Major
151 { { S(0, 0), S( 0,32), S(33, 41), S(31, 50), S(41,100), S(35,104) }, // Weak Minor
152 { S(0, 0), S( 0,27), S(26, 57), S(26, 57), S(0 , 43), S(23, 51) } } // Weak Major
155 // ThreatenedByPawn[PieceType] contains a penalty according to which piece
156 // type is attacked by an enemy pawn.
157 const Score ThreatenedByPawn[PIECE_TYPE_NB] = {
158 S(0, 0), S(0, 0), S(107, 138), S(84, 122), S(114, 203), S(121, 217)
161 const Score ThreatenedByHangingPawn = S(40, 60);
163 // Assorted bonuses and penalties used by evaluation
164 const Score KingOnOne = S( 2, 58);
165 const Score KingOnMany = S( 6,125);
166 const Score RookOnPawn = S( 7, 27);
167 const Score RookOnOpenFile = S(43, 21);
168 const Score RookOnSemiOpenFile = S(19, 10);
169 const Score BishopPawns = S( 8, 12);
170 const Score MinorBehindPawn = S(16, 0);
171 const Score TrappedRook = S(92, 0);
172 const Score Unstoppable = S( 0, 20);
173 const Score Hanging = S(31, 26);
174 const Score PawnAttackThreat = S(20, 20);
175 const Score PawnSafePush = S( 5, 5);
177 // Penalty for a bishop on a1/h1 (a8/h8 for black) which is trapped by
178 // a friendly pawn on b2/g2 (b7/g7 for black). This can obviously only
179 // happen in Chess960 games.
180 const Score TrappedBishopA1H1 = S(50, 50);
185 // SpaceMask[Color] contains the area of the board which is considered
186 // by the space evaluation. In the middlegame, each side is given a bonus
187 // based on how many squares inside this area are safe and available for
188 // friendly minor pieces.
189 const Bitboard SpaceMask[COLOR_NB] = {
190 (FileCBB | FileDBB | FileEBB | FileFBB) & (Rank2BB | Rank3BB | Rank4BB),
191 (FileCBB | FileDBB | FileEBB | FileFBB) & (Rank7BB | Rank6BB | Rank5BB)
194 // King danger constants and variables. The king danger scores are looked-up
195 // in KingDanger[]. Various little "meta-bonuses" measuring the strength
196 // of the enemy attack are added up into an integer, which is used as an
197 // index to KingDanger[].
198 Score KingDanger[512];
200 // KingAttackWeights[PieceType] contains king attack weights by piece type
201 const int KingAttackWeights[PIECE_TYPE_NB] = { 0, 0, 7, 5, 4, 1 };
203 // Penalties for enemy's safe checks
204 const int QueenContactCheck = 89;
205 const int RookContactCheck = 71;
206 const int QueenCheck = 50;
207 const int RookCheck = 37;
208 const int BishopCheck = 6;
209 const int KnightCheck = 14;
212 // init_eval_info() initializes king bitboards for given color adding
213 // pawn attacks. To be done at the beginning of the evaluation.
216 void init_eval_info(const Position& pos, EvalInfo& ei) {
218 const Color Them = (Us == WHITE ? BLACK : WHITE);
219 const Square Down = (Us == WHITE ? DELTA_S : DELTA_N);
221 ei.pinnedPieces[Us] = pos.pinned_pieces(Us);
222 ei.attackedBy[Us][ALL_PIECES] = ei.attackedBy[Us][PAWN] = ei.pi->pawn_attacks(Us);
223 Bitboard b = ei.attackedBy[Them][KING] = pos.attacks_from<KING>(pos.king_square(Them));
225 // Init king safety tables only if we are going to use them
226 if (pos.non_pawn_material(Us) >= QueenValueMg)
228 ei.kingRing[Them] = b | shift_bb<Down>(b);
229 b &= ei.attackedBy[Us][PAWN];
230 ei.kingAttackersCount[Us] = b ? popcount<Max15>(b) : 0;
231 ei.kingAdjacentZoneAttacksCount[Us] = ei.kingAttackersWeight[Us] = 0;
234 ei.kingRing[Them] = ei.kingAttackersCount[Us] = 0;
238 // evaluate_outpost() evaluates bishop and knight outpost squares
240 template<PieceType Pt, Color Us>
241 Score evaluate_outpost(const Position& pos, const EvalInfo& ei, Square s) {
243 const Color Them = (Us == WHITE ? BLACK : WHITE);
245 assert (Pt == BISHOP || Pt == KNIGHT);
247 // Initial bonus based on square
248 Value bonus = Outpost[Pt == BISHOP][relative_square(Us, s)];
250 // Increase bonus if supported by pawn, especially if the opponent has
251 // no minor piece which can trade with the outpost piece.
252 if (bonus && (ei.attackedBy[Us][PAWN] & s))
254 if ( !pos.pieces(Them, KNIGHT)
255 && !(squares_of_color(s) & pos.pieces(Them, BISHOP)))
256 bonus += bonus + bonus / 2;
261 return make_score(bonus * 2, bonus / 2);
265 // evaluate_pieces() assigns bonuses and penalties to the pieces of a given color
267 template<PieceType Pt, Color Us, bool Trace>
268 Score evaluate_pieces(const Position& pos, EvalInfo& ei, Score* mobility, Bitboard* mobilityArea) {
272 Score score = SCORE_ZERO;
274 const PieceType NextPt = (Us == WHITE ? Pt : PieceType(Pt + 1));
275 const Color Them = (Us == WHITE ? BLACK : WHITE);
276 const Square* pl = pos.list<Pt>(Us);
278 ei.attackedBy[Us][Pt] = 0;
280 while ((s = *pl++) != SQ_NONE)
282 // Find attacked squares, including x-ray attacks for bishops and rooks
283 b = Pt == BISHOP ? attacks_bb<BISHOP>(s, pos.pieces() ^ pos.pieces(Us, QUEEN))
284 : Pt == ROOK ? attacks_bb< ROOK>(s, pos.pieces() ^ pos.pieces(Us, ROOK, QUEEN))
285 : pos.attacks_from<Pt>(s);
287 if (ei.pinnedPieces[Us] & s)
288 b &= LineBB[pos.king_square(Us)][s];
290 ei.attackedBy[Us][ALL_PIECES] |= ei.attackedBy[Us][Pt] |= b;
292 if (b & ei.kingRing[Them])
294 ei.kingAttackersCount[Us]++;
295 ei.kingAttackersWeight[Us] += KingAttackWeights[Pt];
296 Bitboard bb = b & ei.attackedBy[Them][KING];
298 ei.kingAdjacentZoneAttacksCount[Us] += popcount<Max15>(bb);
302 b &= ~( ei.attackedBy[Them][KNIGHT]
303 | ei.attackedBy[Them][BISHOP]
304 | ei.attackedBy[Them][ROOK]);
306 int mob = popcount<Pt == QUEEN ? Full : Max15>(b & mobilityArea[Us]);
308 mobility[Us] += MobilityBonus[Pt][mob];
310 if (Pt == BISHOP || Pt == KNIGHT)
312 // Bonus for outpost square
313 if (!(pos.pieces(Them, PAWN) & pawn_attack_span(Us, s)))
314 score += evaluate_outpost<Pt, Us>(pos, ei, s);
316 // Bonus when behind a pawn
317 if ( relative_rank(Us, s) < RANK_5
318 && (pos.pieces(PAWN) & (s + pawn_push(Us))))
319 score += MinorBehindPawn;
321 // Penalty for pawns on same color square of bishop
323 score -= BishopPawns * ei.pi->pawns_on_same_color_squares(Us, s);
325 // An important Chess960 pattern: A cornered bishop blocked by a friendly
326 // pawn diagonally in front of it is a very serious problem, especially
327 // when that pawn is also blocked.
330 && (s == relative_square(Us, SQ_A1) || s == relative_square(Us, SQ_H1)))
332 Square d = pawn_push(Us) + (file_of(s) == FILE_A ? DELTA_E : DELTA_W);
333 if (pos.piece_on(s + d) == make_piece(Us, PAWN))
334 score -= !pos.empty(s + d + pawn_push(Us)) ? TrappedBishopA1H1 * 4
335 : pos.piece_on(s + d + d) == make_piece(Us, PAWN) ? TrappedBishopA1H1 * 2
342 // Bonus for aligning with enemy pawns on the same rank/file
343 if (relative_rank(Us, s) >= RANK_5)
345 Bitboard alignedPawns = pos.pieces(Them, PAWN) & PseudoAttacks[ROOK][s];
347 score += popcount<Max15>(alignedPawns) * RookOnPawn;
350 // Bonus when on an open or semi-open file
351 if (ei.pi->semiopen_file(Us, file_of(s)))
352 score += ei.pi->semiopen_file(Them, file_of(s)) ? RookOnOpenFile : RookOnSemiOpenFile;
354 // Penalize when trapped by the king, even more if king cannot castle
355 if (mob <= 3 && !ei.pi->semiopen_file(Us, file_of(s)))
357 Square ksq = pos.king_square(Us);
359 if ( ((file_of(ksq) < FILE_E) == (file_of(s) < file_of(ksq)))
360 && (rank_of(ksq) == rank_of(s) || relative_rank(Us, ksq) == RANK_1)
361 && !ei.pi->semiopen_side(Us, file_of(ksq), file_of(s) < file_of(ksq)))
362 score -= (TrappedRook - make_score(mob * 22, 0)) * (1 + !pos.can_castle(Us));
368 Tracing::write(Pt, Us, score);
370 // Recursively call evaluate_pieces() of next piece type until KING excluded
371 return score - evaluate_pieces<NextPt, Them, Trace>(pos, ei, mobility, mobilityArea);
375 Score evaluate_pieces<KING, WHITE, false>(const Position&, EvalInfo&, Score*, Bitboard*) { return SCORE_ZERO; }
377 Score evaluate_pieces<KING, WHITE, true>(const Position&, EvalInfo&, Score*, Bitboard*) { return SCORE_ZERO; }
380 // evaluate_king() assigns bonuses and penalties to a king of a given color
382 template<Color Us, bool Trace>
383 Score evaluate_king(const Position& pos, const EvalInfo& ei) {
385 const Color Them = (Us == WHITE ? BLACK : WHITE);
387 Bitboard undefended, b, b1, b2, safe;
389 const Square ksq = pos.king_square(Us);
391 // King shelter and enemy pawns storm
392 Score score = ei.pi->king_safety<Us>(pos, ksq);
394 // Main king safety evaluation
395 if (ei.kingAttackersCount[Them])
397 // Find the attacked squares around the king which have no defenders
398 // apart from the king itself
399 undefended = ei.attackedBy[Them][ALL_PIECES]
400 & ei.attackedBy[Us][KING]
401 & ~( ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
402 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
403 | ei.attackedBy[Us][QUEEN]);
405 // Initialize the 'attackUnits' variable, which is used later on as an
406 // index into the KingDanger[] array. The initial value is based on the
407 // number and types of the enemy's attacking pieces, the number of
408 // attacked and undefended squares around our king and the quality of
409 // the pawn shelter (current 'score' value).
410 attackUnits = std::min(74, ei.kingAttackersCount[Them] * ei.kingAttackersWeight[Them])
411 + 8 * ei.kingAdjacentZoneAttacksCount[Them]
412 + 25 * popcount<Max15>(undefended)
413 + 11 * (ei.pinnedPieces[Us] != 0)
414 - mg_value(score) / 8
415 - !pos.count<QUEEN>(Them) * 60;
417 // Analyse the enemy's safe queen contact checks. Firstly, find the
418 // undefended squares around the king reachable by the enemy queen...
419 b = undefended & ei.attackedBy[Them][QUEEN] & ~pos.pieces(Them);
422 // ...and then remove squares not supported by another enemy piece
423 b &= ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
424 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][ROOK];
427 attackUnits += QueenContactCheck * popcount<Max15>(b);
430 // Analyse the enemy's safe rook contact checks. Firstly, find the
431 // undefended squares around the king reachable by the enemy rooks...
432 b = undefended & ei.attackedBy[Them][ROOK] & ~pos.pieces(Them);
434 // Consider only squares where the enemy's rook gives check
435 b &= PseudoAttacks[ROOK][ksq];
439 // ...and then remove squares not supported by another enemy piece
440 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
441 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][QUEEN]);
444 attackUnits += RookContactCheck * popcount<Max15>(b);
447 // Analyse the enemy's safe distance checks for sliders and knights
448 safe = ~(ei.attackedBy[Us][ALL_PIECES] | pos.pieces(Them));
450 b1 = pos.attacks_from<ROOK >(ksq) & safe;
451 b2 = pos.attacks_from<BISHOP>(ksq) & safe;
453 // Enemy queen safe checks
454 b = (b1 | b2) & ei.attackedBy[Them][QUEEN];
456 attackUnits += QueenCheck * popcount<Max15>(b);
458 // Enemy rooks safe checks
459 b = b1 & ei.attackedBy[Them][ROOK];
461 attackUnits += RookCheck * popcount<Max15>(b);
463 // Enemy bishops safe checks
464 b = b2 & ei.attackedBy[Them][BISHOP];
466 attackUnits += BishopCheck * popcount<Max15>(b);
468 // Enemy knights safe checks
469 b = pos.attacks_from<KNIGHT>(ksq) & ei.attackedBy[Them][KNIGHT] & safe;
471 attackUnits += KnightCheck * popcount<Max15>(b);
473 // Finally, extract the king danger score from the KingDanger[]
474 // array and subtract the score from evaluation.
475 score -= KingDanger[std::max(std::min(attackUnits, 399), 0)];
479 Tracing::write(KING, Us, score);
485 // evaluate_threats() assigns bonuses according to the type of attacking piece
486 // and the type of attacked one.
488 template<Color Us, bool Trace>
489 Score evaluate_threats(const Position& pos, const EvalInfo& ei) {
491 const Color Them = (Us == WHITE ? BLACK : WHITE);
492 const Square Up = (Us == WHITE ? DELTA_N : DELTA_S);
493 const Square Left = (Us == WHITE ? DELTA_NW : DELTA_SE);
494 const Square Right = (Us == WHITE ? DELTA_NE : DELTA_SW);
495 const Bitboard TRank2BB = (Us == WHITE ? Rank2BB : Rank7BB);
496 const Bitboard TRank7BB = (Us == WHITE ? Rank7BB : Rank2BB);
498 enum { Defended, Weak };
499 enum { Minor, Major };
501 Bitboard b, weak, defended, safe_pawns, safe_pawn_threats, unsafe_pawn_threats;
502 Score score = SCORE_ZERO;
505 b = ei.attackedBy[Us][PAWN] & (pos.pieces(Them) ^ pos.pieces(Them, PAWN));
509 safe_pawns = pos.pieces(Us, PAWN) & (~ei.attackedBy[Them][ALL_PIECES] | ei.attackedBy[Us][ALL_PIECES]);
510 safe_pawn_threats = (shift_bb<Right>(safe_pawns) | shift_bb<Left>(safe_pawns)) & (pos.pieces(Them) ^ pos.pieces(Them, PAWN));
511 unsafe_pawn_threats = b ^ safe_pawn_threats;
513 // Unsafe pawn threats
514 if (unsafe_pawn_threats)
515 score += ThreatenedByHangingPawn;
517 // Evaluate safe pawn threats
518 while (safe_pawn_threats)
519 score += ThreatenedByPawn[type_of(pos.piece_on(pop_lsb(&safe_pawn_threats)))];
522 // Non-pawn enemies defended by a pawn
523 defended = (pos.pieces(Them) ^ pos.pieces(Them, PAWN)) & ei.attackedBy[Them][PAWN];
525 // Add a bonus according to the kind of attacking pieces
528 b = defended & (ei.attackedBy[Us][KNIGHT] | ei.attackedBy[Us][BISHOP]);
530 score += Threat[Defended][Minor][type_of(pos.piece_on(pop_lsb(&b)))];
532 b = defended & (ei.attackedBy[Us][ROOK]);
534 score += Threat[Defended][Major][type_of(pos.piece_on(pop_lsb(&b)))];
537 // Enemies not defended by a pawn and under our attack
538 weak = pos.pieces(Them)
539 & ~ei.attackedBy[Them][PAWN]
540 & ei.attackedBy[Us][ALL_PIECES];
542 // Add a bonus according to the kind of attacking pieces
545 b = weak & (ei.attackedBy[Us][KNIGHT] | ei.attackedBy[Us][BISHOP]);
547 score += Threat[Weak][Minor][type_of(pos.piece_on(pop_lsb(&b)))];
549 b = weak & (ei.attackedBy[Us][ROOK] | ei.attackedBy[Us][QUEEN]);
551 score += Threat[Weak][Major][type_of(pos.piece_on(pop_lsb(&b)))];
553 b = weak & ~ei.attackedBy[Them][ALL_PIECES];
555 score += Hanging * popcount<Max15>(b);
557 b = weak & ei.attackedBy[Us][KING];
559 score += more_than_one(b) ? KingOnMany : KingOnOne;
562 // Add a small bonus for safe pawn pushes
563 b = pos.pieces(Us, PAWN) & ~TRank7BB;
564 b = shift_bb<Up>(b | (shift_bb<Up>(b & TRank2BB) & ~pos.pieces()));
567 & ~ei.attackedBy[Them][PAWN]
568 & (ei.attackedBy[Us][ALL_PIECES] | ~ei.attackedBy[Them][ALL_PIECES]);
571 score += popcount<Full>(b) * PawnSafePush;
573 // Add another bonus if the pawn push attacks an enemy piece
574 b = (shift_bb<Left>(b) | shift_bb<Right>(b))
576 & ~ei.attackedBy[Us][PAWN];
579 score += popcount<Max15>(b) * PawnAttackThreat;
582 Tracing::write(Tracing::THREAT, Us, score);
588 // evaluate_passed_pawns() evaluates the passed pawns of the given color
590 template<Color Us, bool Trace>
591 Score evaluate_passed_pawns(const Position& pos, const EvalInfo& ei) {
593 const Color Them = (Us == WHITE ? BLACK : WHITE);
595 Bitboard b, squaresToQueen, defendedSquares, unsafeSquares;
596 Score score = SCORE_ZERO;
598 b = ei.pi->passed_pawns(Us);
602 Square s = pop_lsb(&b);
604 assert(pos.pawn_passed(Us, s));
606 int r = relative_rank(Us, s) - RANK_2;
607 int rr = r * (r - 1);
609 // Base bonus based on rank
610 Value mbonus = Value(17 * rr), ebonus = Value(7 * (rr + r + 1));
614 Square blockSq = s + pawn_push(Us);
616 // Adjust bonus based on the king's proximity
617 ebonus += distance(pos.king_square(Them), blockSq) * 5 * rr
618 - distance(pos.king_square(Us ), blockSq) * 2 * rr;
620 // If blockSq is not the queening square then consider also a second push
621 if (relative_rank(Us, blockSq) != RANK_8)
622 ebonus -= distance(pos.king_square(Us), blockSq + pawn_push(Us)) * rr;
624 // If the pawn is free to advance, then increase the bonus
625 if (pos.empty(blockSq))
627 // If there is a rook or queen attacking/defending the pawn from behind,
628 // consider all the squaresToQueen. Otherwise consider only the squares
629 // in the pawn's path attacked or occupied by the enemy.
630 defendedSquares = unsafeSquares = squaresToQueen = forward_bb(Us, s);
632 Bitboard bb = forward_bb(Them, s) & pos.pieces(ROOK, QUEEN) & pos.attacks_from<ROOK>(s);
634 if (!(pos.pieces(Us) & bb))
635 defendedSquares &= ei.attackedBy[Us][ALL_PIECES];
637 if (!(pos.pieces(Them) & bb))
638 unsafeSquares &= ei.attackedBy[Them][ALL_PIECES] | pos.pieces(Them);
640 // If there aren't any enemy attacks, assign a big bonus. Otherwise
641 // assign a smaller bonus if the block square isn't attacked.
642 int k = !unsafeSquares ? 15 : !(unsafeSquares & blockSq) ? 9 : 0;
644 // If the path to queen is fully defended, assign a big bonus.
645 // Otherwise assign a smaller bonus if the block square is defended.
646 if (defendedSquares == squaresToQueen)
649 else if (defendedSquares & blockSq)
652 mbonus += k * rr, ebonus += k * rr;
654 else if (pos.pieces(Us) & blockSq)
655 mbonus += rr * 3 + r * 2 + 3, ebonus += rr + r * 2;
658 if (pos.count<PAWN>(Us) < pos.count<PAWN>(Them))
659 ebonus += ebonus / 4;
661 score += make_score(mbonus, ebonus);
665 Tracing::write(Tracing::PASSED, Us, score * Weights[PassedPawns]);
667 // Add the scores to the middlegame and endgame eval
668 return score * Weights[PassedPawns];
672 // evaluate_space() computes the space evaluation for a given side. The
673 // space evaluation is a simple bonus based on the number of safe squares
674 // available for minor pieces on the central four files on ranks 2--4. Safe
675 // squares one, two or three squares behind a friendly pawn are counted
676 // twice. Finally, the space bonus is multiplied by a weight. The aim is to
677 // improve play on game opening.
679 Score evaluate_space(const Position& pos, const EvalInfo& ei) {
681 const Color Them = (Us == WHITE ? BLACK : WHITE);
683 // Find the safe squares for our pieces inside the area defined by
684 // SpaceMask[]. A square is unsafe if it is attacked by an enemy
685 // pawn, or if it is undefended and attacked by an enemy piece.
686 Bitboard safe = SpaceMask[Us]
687 & ~pos.pieces(Us, PAWN)
688 & ~ei.attackedBy[Them][PAWN]
689 & (ei.attackedBy[Us][ALL_PIECES] | ~ei.attackedBy[Them][ALL_PIECES]);
691 // Find all squares which are at most three squares behind some friendly pawn
692 Bitboard behind = pos.pieces(Us, PAWN);
693 behind |= (Us == WHITE ? behind >> 8 : behind << 8);
694 behind |= (Us == WHITE ? behind >> 16 : behind << 16);
696 // Since SpaceMask[Us] is fully on our half of the board
697 assert(unsigned(safe >> (Us == WHITE ? 32 : 0)) == 0);
699 // Count safe + (behind & safe) with a single popcount
700 int bonus = popcount<Full>((Us == WHITE ? safe << 32 : safe >> 32) | (behind & safe));
701 int weight = pos.count<KNIGHT>(Us) + pos.count<BISHOP>(Us)
702 + pos.count<KNIGHT>(Them) + pos.count<BISHOP>(Them);
704 return make_score(bonus * weight * weight, 0);
708 // do_evaluate() is the evaluation entry point, called directly from evaluate()
711 Value do_evaluate(const Position& pos) {
713 assert(!pos.checkers());
716 Score score, mobility[2] = { SCORE_ZERO, SCORE_ZERO };
718 // Initialize score by reading the incrementally updated scores included
719 // in the position object (material + piece square tables).
720 // Score is computed from the point of view of white.
721 score = pos.psq_score();
723 // Probe the material hash table
724 ei.mi = Material::probe(pos);
725 score += ei.mi->imbalance();
727 // If we have a specialized evaluation function for the current material
728 // configuration, call it and return.
729 if (ei.mi->specialized_eval_exists())
730 return ei.mi->evaluate(pos);
732 // Probe the pawn hash table
733 ei.pi = Pawns::probe(pos);
734 score += ei.pi->pawns_score() * Weights[PawnStructure];
736 // Initialize attack and king safety bitboards
737 init_eval_info<WHITE>(pos, ei);
738 init_eval_info<BLACK>(pos, ei);
740 ei.attackedBy[WHITE][ALL_PIECES] |= ei.attackedBy[WHITE][KING];
741 ei.attackedBy[BLACK][ALL_PIECES] |= ei.attackedBy[BLACK][KING];
743 // Do not include in mobility squares protected by enemy pawns or occupied by our pawns or king
744 Bitboard mobilityArea[] = { ~(ei.attackedBy[BLACK][PAWN] | pos.pieces(WHITE, PAWN, KING)),
745 ~(ei.attackedBy[WHITE][PAWN] | pos.pieces(BLACK, PAWN, KING)) };
747 // Evaluate pieces and mobility
748 score += evaluate_pieces<KNIGHT, WHITE, Trace>(pos, ei, mobility, mobilityArea);
749 score += (mobility[WHITE] - mobility[BLACK]) * Weights[Mobility];
751 // Evaluate kings after all other pieces because we need complete attack
752 // information when computing the king safety evaluation.
753 score += evaluate_king<WHITE, Trace>(pos, ei)
754 - evaluate_king<BLACK, Trace>(pos, ei);
756 // Evaluate tactical threats, we need full attack information including king
757 score += evaluate_threats<WHITE, Trace>(pos, ei)
758 - evaluate_threats<BLACK, Trace>(pos, ei);
760 // Evaluate passed pawns, we need full attack information including king
761 score += evaluate_passed_pawns<WHITE, Trace>(pos, ei)
762 - evaluate_passed_pawns<BLACK, Trace>(pos, ei);
764 // If both sides have only pawns, score for potential unstoppable pawns
765 if (!pos.non_pawn_material(WHITE) && !pos.non_pawn_material(BLACK))
768 if ((b = ei.pi->passed_pawns(WHITE)) != 0)
769 score += int(relative_rank(WHITE, frontmost_sq(WHITE, b))) * Unstoppable;
771 if ((b = ei.pi->passed_pawns(BLACK)) != 0)
772 score -= int(relative_rank(BLACK, frontmost_sq(BLACK, b))) * Unstoppable;
775 // Evaluate space for both sides, only during opening
776 if (pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK) >= 11756)
777 score += (evaluate_space<WHITE>(pos, ei) - evaluate_space<BLACK>(pos, ei)) * Weights[Space];
779 // Scale winning side if position is more drawish than it appears
780 Color strongSide = eg_value(score) > VALUE_DRAW ? WHITE : BLACK;
781 ScaleFactor sf = ei.mi->scale_factor(pos, strongSide);
783 // If we don't already have an unusual scale factor, check for certain
784 // types of endgames, and use a lower scale for those.
785 if ( ei.mi->game_phase() < PHASE_MIDGAME
786 && (sf == SCALE_FACTOR_NORMAL || sf == SCALE_FACTOR_ONEPAWN))
788 if (pos.opposite_bishops())
790 // Endgame with opposite-colored bishops and no other pieces (ignoring pawns)
791 // is almost a draw, in case of KBP vs KB is even more a draw.
792 if ( pos.non_pawn_material(WHITE) == BishopValueMg
793 && pos.non_pawn_material(BLACK) == BishopValueMg)
794 sf = more_than_one(pos.pieces(PAWN)) ? ScaleFactor(32) : ScaleFactor(8);
796 // Endgame with opposite-colored bishops, but also other pieces. Still
797 // a bit drawish, but not as drawish as with only the two bishops.
799 sf = ScaleFactor(50 * sf / SCALE_FACTOR_NORMAL);
801 // Endings where weaker side can place his king in front of the opponent's
802 // pawns are drawish.
803 else if ( abs(eg_value(score)) <= BishopValueEg
804 && ei.pi->pawn_span(strongSide) <= 1
805 && !pos.pawn_passed(~strongSide, pos.king_square(~strongSide)))
806 sf = ei.pi->pawn_span(strongSide) ? ScaleFactor(56) : ScaleFactor(38);
809 // Interpolate between a middlegame and a (scaled by 'sf') endgame score
810 Value v = mg_value(score) * int(ei.mi->game_phase())
811 + eg_value(score) * int(PHASE_MIDGAME - ei.mi->game_phase()) * sf / SCALE_FACTOR_NORMAL;
813 v /= int(PHASE_MIDGAME);
815 // In case of tracing add all single evaluation terms for both white and black
818 Tracing::write(Tracing::MATERIAL, pos.psq_score());
819 Tracing::write(Tracing::IMBALANCE, ei.mi->imbalance());
820 Tracing::write(PAWN, ei.pi->pawns_score());
821 Tracing::write(Tracing::MOBILITY, mobility[WHITE] * Weights[Mobility]
822 , mobility[BLACK] * Weights[Mobility]);
823 Tracing::write(Tracing::SPACE, evaluate_space<WHITE>(pos, ei) * Weights[Space]
824 , evaluate_space<BLACK>(pos, ei) * Weights[Space]);
825 Tracing::write(Tracing::TOTAL, score);
828 return (pos.side_to_move() == WHITE ? v : -v) + Eval::Tempo; // Side to move point of view
834 double Tracing::to_cp(Value v) { return double(v) / PawnValueEg; }
836 void Tracing::write(int idx, Color c, Score s) { scores[c][idx] = s; }
838 void Tracing::write(int idx, Score w, Score b) {
839 scores[WHITE][idx] = w, scores[BLACK][idx] = b;
842 std::ostream& Tracing::operator<<(std::ostream& os, Term t) {
844 double wScore[] = { to_cp(mg_value(scores[WHITE][t])), to_cp(eg_value(scores[WHITE][t])) };
845 double bScore[] = { to_cp(mg_value(scores[BLACK][t])), to_cp(eg_value(scores[BLACK][t])) };
847 if (t == MATERIAL || t == IMBALANCE || t == Term(PAWN) || t == TOTAL)
848 os << " --- --- | --- --- | ";
850 os << std::setw(5) << wScore[MG] << " " << std::setw(5) << wScore[EG] << " | "
851 << std::setw(5) << bScore[MG] << " " << std::setw(5) << bScore[EG] << " | ";
853 os << std::setw(5) << wScore[MG] - bScore[MG] << " "
854 << std::setw(5) << wScore[EG] - bScore[EG] << " \n";
859 std::string Tracing::do_trace(const Position& pos) {
861 std::memset(scores, 0, sizeof(scores));
863 Value v = do_evaluate<true>(pos);
864 v = pos.side_to_move() == WHITE ? v : -v; // White's point of view
866 std::stringstream ss;
867 ss << std::showpoint << std::noshowpos << std::fixed << std::setprecision(2)
868 << " Eval term | White | Black | Total \n"
869 << " | MG EG | MG EG | MG EG \n"
870 << "----------------+-------------+-------------+-------------\n"
871 << " Material | " << Term(MATERIAL)
872 << " Imbalance | " << Term(IMBALANCE)
873 << " Pawns | " << Term(PAWN)
874 << " Knights | " << Term(KNIGHT)
875 << " Bishop | " << Term(BISHOP)
876 << " Rooks | " << Term(ROOK)
877 << " Queens | " << Term(QUEEN)
878 << " Mobility | " << Term(MOBILITY)
879 << " King safety | " << Term(KING)
880 << " Threats | " << Term(THREAT)
881 << " Passed pawns | " << Term(PASSED)
882 << " Space | " << Term(SPACE)
883 << "----------------+-------------+-------------+-------------\n"
884 << " Total | " << Term(TOTAL);
886 ss << "\nTotal Evaluation: " << to_cp(v) << " (white side)\n";
896 /// evaluate() is the main evaluation function. It returns a static evaluation
897 /// of the position always from the point of view of the side to move.
899 Value evaluate(const Position& pos) {
900 return do_evaluate<false>(pos);
904 /// trace() is like evaluate(), but instead of returning a value, it returns
905 /// a string (suitable for outputting to stdout) that contains the detailed
906 /// descriptions and values of each evaluation term. It's mainly used for
908 std::string trace(const Position& pos) {
909 return Tracing::do_trace(pos);
913 /// init() computes evaluation weights, usually at startup
917 const int MaxSlope = 8700;
918 const int Peak = 1280000;
921 for (int i = 0; i < 400; ++i)
923 t = std::min(Peak, std::min(i * i * 27, t + MaxSlope));
924 KingDanger[i] = make_score(t / 1000, 0) * Weights[KingSafety];