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]);
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, safeThreats;
502 Score score = SCORE_ZERO;
504 // Non-pawn enemies attacked by a pawn
505 weak = (pos.pieces(Them) ^ pos.pieces(Them, PAWN)) & ei.attackedBy[Us][PAWN];
509 b = pos.pieces(Us, PAWN) & ( ~ei.attackedBy[Them][ALL_PIECES]
510 | ei.attackedBy[Us][ALL_PIECES]);
512 safeThreats = (shift_bb<Right>(b) | shift_bb<Left>(b)) & weak;
514 if (weak ^ safeThreats)
515 score += ThreatenedByHangingPawn;
518 score += ThreatenedByPawn[type_of(pos.piece_on(pop_lsb(&safeThreats)))];
521 // Non-pawn enemies defended by a pawn
522 defended = (pos.pieces(Them) ^ pos.pieces(Them, PAWN)) & ei.attackedBy[Them][PAWN];
524 // Add a bonus according to the kind of attacking pieces
527 b = defended & (ei.attackedBy[Us][KNIGHT] | ei.attackedBy[Us][BISHOP]);
529 score += Threat[Defended][Minor][type_of(pos.piece_on(pop_lsb(&b)))];
531 b = defended & (ei.attackedBy[Us][ROOK]);
533 score += Threat[Defended][Major][type_of(pos.piece_on(pop_lsb(&b)))];
536 // Enemies not defended by a pawn and under our attack
537 weak = pos.pieces(Them)
538 & ~ei.attackedBy[Them][PAWN]
539 & ei.attackedBy[Us][ALL_PIECES];
541 // Add a bonus according to the kind of attacking pieces
544 b = weak & (ei.attackedBy[Us][KNIGHT] | ei.attackedBy[Us][BISHOP]);
546 score += Threat[Weak][Minor][type_of(pos.piece_on(pop_lsb(&b)))];
548 b = weak & (ei.attackedBy[Us][ROOK] | ei.attackedBy[Us][QUEEN]);
550 score += Threat[Weak][Major][type_of(pos.piece_on(pop_lsb(&b)))];
552 b = weak & ~ei.attackedBy[Them][ALL_PIECES];
554 score += Hanging * popcount<Max15>(b);
556 b = weak & ei.attackedBy[Us][KING];
558 score += more_than_one(b) ? KingOnMany : KingOnOne;
561 // Add a small bonus for safe pawn pushes
562 b = pos.pieces(Us, PAWN) & ~TRank7BB;
563 b = shift_bb<Up>(b | (shift_bb<Up>(b & TRank2BB) & ~pos.pieces()));
566 & ~ei.attackedBy[Them][PAWN]
567 & (ei.attackedBy[Us][ALL_PIECES] | ~ei.attackedBy[Them][ALL_PIECES]);
570 score += popcount<Full>(b) * PawnSafePush;
572 // Add another bonus if the pawn push attacks an enemy piece
573 b = (shift_bb<Left>(b) | shift_bb<Right>(b))
575 & ~ei.attackedBy[Us][PAWN];
578 score += popcount<Max15>(b) * PawnAttackThreat;
581 Tracing::write(Tracing::THREAT, Us, score);
587 // evaluate_passed_pawns() evaluates the passed pawns of the given color
589 template<Color Us, bool Trace>
590 Score evaluate_passed_pawns(const Position& pos, const EvalInfo& ei) {
592 const Color Them = (Us == WHITE ? BLACK : WHITE);
594 Bitboard b, squaresToQueen, defendedSquares, unsafeSquares;
595 Score score = SCORE_ZERO;
597 b = ei.pi->passed_pawns(Us);
601 Square s = pop_lsb(&b);
603 assert(pos.pawn_passed(Us, s));
605 int r = relative_rank(Us, s) - RANK_2;
606 int rr = r * (r - 1);
608 // Base bonus based on rank
609 Value mbonus = Value(17 * rr), ebonus = Value(7 * (rr + r + 1));
613 Square blockSq = s + pawn_push(Us);
615 // Adjust bonus based on the king's proximity
616 ebonus += distance(pos.king_square(Them), blockSq) * 5 * rr
617 - distance(pos.king_square(Us ), blockSq) * 2 * rr;
619 // If blockSq is not the queening square then consider also a second push
620 if (relative_rank(Us, blockSq) != RANK_8)
621 ebonus -= distance(pos.king_square(Us), blockSq + pawn_push(Us)) * rr;
623 // If the pawn is free to advance, then increase the bonus
624 if (pos.empty(blockSq))
626 // If there is a rook or queen attacking/defending the pawn from behind,
627 // consider all the squaresToQueen. Otherwise consider only the squares
628 // in the pawn's path attacked or occupied by the enemy.
629 defendedSquares = unsafeSquares = squaresToQueen = forward_bb(Us, s);
631 Bitboard bb = forward_bb(Them, s) & pos.pieces(ROOK, QUEEN) & pos.attacks_from<ROOK>(s);
633 if (!(pos.pieces(Us) & bb))
634 defendedSquares &= ei.attackedBy[Us][ALL_PIECES];
636 if (!(pos.pieces(Them) & bb))
637 unsafeSquares &= ei.attackedBy[Them][ALL_PIECES] | pos.pieces(Them);
639 // If there aren't any enemy attacks, assign a big bonus. Otherwise
640 // assign a smaller bonus if the block square isn't attacked.
641 int k = !unsafeSquares ? 15 : !(unsafeSquares & blockSq) ? 9 : 0;
643 // If the path to queen is fully defended, assign a big bonus.
644 // Otherwise assign a smaller bonus if the block square is defended.
645 if (defendedSquares == squaresToQueen)
648 else if (defendedSquares & blockSq)
651 mbonus += k * rr, ebonus += k * rr;
653 else if (pos.pieces(Us) & blockSq)
654 mbonus += rr * 3 + r * 2 + 3, ebonus += rr + r * 2;
657 if (pos.count<PAWN>(Us) < pos.count<PAWN>(Them))
658 ebonus += ebonus / 4;
660 score += make_score(mbonus, ebonus);
664 Tracing::write(Tracing::PASSED, Us, score * Weights[PassedPawns]);
666 // Add the scores to the middlegame and endgame eval
667 return score * Weights[PassedPawns];
671 // evaluate_space() computes the space evaluation for a given side. The
672 // space evaluation is a simple bonus based on the number of safe squares
673 // available for minor pieces on the central four files on ranks 2--4. Safe
674 // squares one, two or three squares behind a friendly pawn are counted
675 // twice. Finally, the space bonus is multiplied by a weight. The aim is to
676 // improve play on game opening.
678 Score evaluate_space(const Position& pos, const EvalInfo& ei) {
680 const Color Them = (Us == WHITE ? BLACK : WHITE);
682 // Find the safe squares for our pieces inside the area defined by
683 // SpaceMask[]. A square is unsafe if it is attacked by an enemy
684 // pawn, or if it is undefended and attacked by an enemy piece.
685 Bitboard safe = SpaceMask[Us]
686 & ~pos.pieces(Us, PAWN)
687 & ~ei.attackedBy[Them][PAWN]
688 & (ei.attackedBy[Us][ALL_PIECES] | ~ei.attackedBy[Them][ALL_PIECES]);
690 // Find all squares which are at most three squares behind some friendly pawn
691 Bitboard behind = pos.pieces(Us, PAWN);
692 behind |= (Us == WHITE ? behind >> 8 : behind << 8);
693 behind |= (Us == WHITE ? behind >> 16 : behind << 16);
695 // Since SpaceMask[Us] is fully on our half of the board
696 assert(unsigned(safe >> (Us == WHITE ? 32 : 0)) == 0);
698 // Count safe + (behind & safe) with a single popcount
699 int bonus = popcount<Full>((Us == WHITE ? safe << 32 : safe >> 32) | (behind & safe));
700 int weight = pos.count<KNIGHT>(Us) + pos.count<BISHOP>(Us)
701 + pos.count<KNIGHT>(Them) + pos.count<BISHOP>(Them);
703 return make_score(bonus * weight * weight, 0);
707 // do_evaluate() is the evaluation entry point, called directly from evaluate()
710 Value do_evaluate(const Position& pos) {
712 assert(!pos.checkers());
715 Score score, mobility[2] = { SCORE_ZERO, SCORE_ZERO };
717 // Initialize score by reading the incrementally updated scores included
718 // in the position object (material + piece square tables).
719 // Score is computed from the point of view of white.
720 score = pos.psq_score();
722 // Probe the material hash table
723 ei.mi = Material::probe(pos);
724 score += ei.mi->imbalance();
726 // If we have a specialized evaluation function for the current material
727 // configuration, call it and return.
728 if (ei.mi->specialized_eval_exists())
729 return ei.mi->evaluate(pos);
731 // Probe the pawn hash table
732 ei.pi = Pawns::probe(pos);
733 score += ei.pi->pawns_score() * Weights[PawnStructure];
735 // Initialize attack and king safety bitboards
736 init_eval_info<WHITE>(pos, ei);
737 init_eval_info<BLACK>(pos, ei);
739 ei.attackedBy[WHITE][ALL_PIECES] |= ei.attackedBy[WHITE][KING];
740 ei.attackedBy[BLACK][ALL_PIECES] |= ei.attackedBy[BLACK][KING];
742 // Do not include in mobility squares protected by enemy pawns or occupied by our pawns or king
743 Bitboard mobilityArea[] = { ~(ei.attackedBy[BLACK][PAWN] | pos.pieces(WHITE, PAWN, KING)),
744 ~(ei.attackedBy[WHITE][PAWN] | pos.pieces(BLACK, PAWN, KING)) };
746 // Evaluate pieces and mobility
747 score += evaluate_pieces<KNIGHT, WHITE, Trace>(pos, ei, mobility, mobilityArea);
748 score += (mobility[WHITE] - mobility[BLACK]) * Weights[Mobility];
750 // Evaluate kings after all other pieces because we need complete attack
751 // information when computing the king safety evaluation.
752 score += evaluate_king<WHITE, Trace>(pos, ei)
753 - evaluate_king<BLACK, Trace>(pos, ei);
755 // Evaluate tactical threats, we need full attack information including king
756 score += evaluate_threats<WHITE, Trace>(pos, ei)
757 - evaluate_threats<BLACK, Trace>(pos, ei);
759 // Evaluate passed pawns, we need full attack information including king
760 score += evaluate_passed_pawns<WHITE, Trace>(pos, ei)
761 - evaluate_passed_pawns<BLACK, Trace>(pos, ei);
763 // If both sides have only pawns, score for potential unstoppable pawns
764 if (!pos.non_pawn_material(WHITE) && !pos.non_pawn_material(BLACK))
767 if ((b = ei.pi->passed_pawns(WHITE)) != 0)
768 score += int(relative_rank(WHITE, frontmost_sq(WHITE, b))) * Unstoppable;
770 if ((b = ei.pi->passed_pawns(BLACK)) != 0)
771 score -= int(relative_rank(BLACK, frontmost_sq(BLACK, b))) * Unstoppable;
774 // Evaluate space for both sides, only during opening
775 if (pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK) >= 11756)
776 score += (evaluate_space<WHITE>(pos, ei) - evaluate_space<BLACK>(pos, ei)) * Weights[Space];
778 // Scale winning side if position is more drawish than it appears
779 Color strongSide = eg_value(score) > VALUE_DRAW ? WHITE : BLACK;
780 ScaleFactor sf = ei.mi->scale_factor(pos, strongSide);
782 // If we don't already have an unusual scale factor, check for certain
783 // types of endgames, and use a lower scale for those.
784 if ( ei.mi->game_phase() < PHASE_MIDGAME
785 && (sf == SCALE_FACTOR_NORMAL || sf == SCALE_FACTOR_ONEPAWN))
787 if (pos.opposite_bishops())
789 // Endgame with opposite-colored bishops and no other pieces (ignoring pawns)
790 // is almost a draw, in case of KBP vs KB is even more a draw.
791 if ( pos.non_pawn_material(WHITE) == BishopValueMg
792 && pos.non_pawn_material(BLACK) == BishopValueMg)
793 sf = more_than_one(pos.pieces(PAWN)) ? ScaleFactor(32) : ScaleFactor(8);
795 // Endgame with opposite-colored bishops, but also other pieces. Still
796 // a bit drawish, but not as drawish as with only the two bishops.
798 sf = ScaleFactor(50 * sf / SCALE_FACTOR_NORMAL);
800 // Endings where weaker side can place his king in front of the opponent's
801 // pawns are drawish.
802 else if ( abs(eg_value(score)) <= BishopValueEg
803 && ei.pi->pawn_span(strongSide) <= 1
804 && !pos.pawn_passed(~strongSide, pos.king_square(~strongSide)))
805 sf = ei.pi->pawn_span(strongSide) ? ScaleFactor(56) : ScaleFactor(38);
808 // Interpolate between a middlegame and a (scaled by 'sf') endgame score
809 Value v = mg_value(score) * int(ei.mi->game_phase())
810 + eg_value(score) * int(PHASE_MIDGAME - ei.mi->game_phase()) * sf / SCALE_FACTOR_NORMAL;
812 v /= int(PHASE_MIDGAME);
814 // In case of tracing add all single evaluation terms for both white and black
817 Tracing::write(Tracing::MATERIAL, pos.psq_score());
818 Tracing::write(Tracing::IMBALANCE, ei.mi->imbalance());
819 Tracing::write(PAWN, ei.pi->pawns_score());
820 Tracing::write(Tracing::MOBILITY, mobility[WHITE] * Weights[Mobility]
821 , mobility[BLACK] * Weights[Mobility]);
822 Tracing::write(Tracing::SPACE, evaluate_space<WHITE>(pos, ei) * Weights[Space]
823 , evaluate_space<BLACK>(pos, ei) * Weights[Space]);
824 Tracing::write(Tracing::TOTAL, score);
827 return (pos.side_to_move() == WHITE ? v : -v) + Eval::Tempo; // Side to move point of view
833 double Tracing::to_cp(Value v) { return double(v) / PawnValueEg; }
835 void Tracing::write(int idx, Color c, Score s) { scores[c][idx] = s; }
837 void Tracing::write(int idx, Score w, Score b) {
838 scores[WHITE][idx] = w, scores[BLACK][idx] = b;
841 std::ostream& Tracing::operator<<(std::ostream& os, Term t) {
843 double wScore[] = { to_cp(mg_value(scores[WHITE][t])), to_cp(eg_value(scores[WHITE][t])) };
844 double bScore[] = { to_cp(mg_value(scores[BLACK][t])), to_cp(eg_value(scores[BLACK][t])) };
846 if (t == MATERIAL || t == IMBALANCE || t == Term(PAWN) || t == TOTAL)
847 os << " --- --- | --- --- | ";
849 os << std::setw(5) << wScore[MG] << " " << std::setw(5) << wScore[EG] << " | "
850 << std::setw(5) << bScore[MG] << " " << std::setw(5) << bScore[EG] << " | ";
852 os << std::setw(5) << wScore[MG] - bScore[MG] << " "
853 << std::setw(5) << wScore[EG] - bScore[EG] << " \n";
858 std::string Tracing::do_trace(const Position& pos) {
860 std::memset(scores, 0, sizeof(scores));
862 Value v = do_evaluate<true>(pos);
863 v = pos.side_to_move() == WHITE ? v : -v; // White's point of view
865 std::stringstream ss;
866 ss << std::showpoint << std::noshowpos << std::fixed << std::setprecision(2)
867 << " Eval term | White | Black | Total \n"
868 << " | MG EG | MG EG | MG EG \n"
869 << "----------------+-------------+-------------+-------------\n"
870 << " Material | " << Term(MATERIAL)
871 << " Imbalance | " << Term(IMBALANCE)
872 << " Pawns | " << Term(PAWN)
873 << " Knights | " << Term(KNIGHT)
874 << " Bishop | " << Term(BISHOP)
875 << " Rooks | " << Term(ROOK)
876 << " Queens | " << Term(QUEEN)
877 << " Mobility | " << Term(MOBILITY)
878 << " King safety | " << Term(KING)
879 << " Threats | " << Term(THREAT)
880 << " Passed pawns | " << Term(PASSED)
881 << " Space | " << Term(SPACE)
882 << "----------------+-------------+-------------+-------------\n"
883 << " Total | " << Term(TOTAL);
885 ss << "\nTotal Evaluation: " << to_cp(v) << " (white side)\n";
895 /// evaluate() is the main evaluation function. It returns a static evaluation
896 /// of the position always from the point of view of the side to move.
898 Value evaluate(const Position& pos) {
899 return do_evaluate<false>(pos);
903 /// trace() is like evaluate(), but instead of returning a value, it returns
904 /// a string (suitable for outputting to stdout) that contains the detailed
905 /// descriptions and values of each evaluation term. It's mainly used for
907 std::string trace(const Position& pos) {
908 return Tracing::do_trace(pos);
912 /// init() computes evaluation weights, usually at startup
916 const int MaxSlope = 8700;
917 const int Peak = 1280000;
920 for (int i = 0; i < 400; ++i)
922 t = std::min(Peak, std::min(i * i * 27, t + MaxSlope));
923 KingDanger[i] = make_score(t / 1000, 0) * Weights[KingSafety];