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
33 // Struct EvalInfo contains various information computed and collected
34 // by the evaluation functions.
37 // Pointers to material and pawn hash table entries
41 // attackedBy[color][piece type] is a bitboard representing all squares
42 // attacked by a given color and piece type, attackedBy[color][ALL_PIECES]
43 // contains all squares attacked by the given color.
44 Bitboard attackedBy[COLOR_NB][PIECE_TYPE_NB];
46 // kingRing[color] is the zone around the king which is considered
47 // by the king safety evaluation. This consists of the squares directly
48 // adjacent to the king, and the three (or two, for a king on an edge file)
49 // squares two ranks in front of the king. For instance, if black's king
50 // is on g8, kingRing[BLACK] is a bitboard containing the squares f8, h8,
51 // f7, g7, h7, f6, g6 and h6.
52 Bitboard kingRing[COLOR_NB];
54 // kingAttackersCount[color] is the number of pieces of the given color
55 // which attack a square in the kingRing of the enemy king.
56 int kingAttackersCount[COLOR_NB];
58 // kingAttackersWeight[color] is the sum of the "weight" of the pieces of the
59 // given color which attack a square in the kingRing of the enemy king. The
60 // weights of the individual piece types are given by the elements in the
61 // KingAttackWeights array.
62 int kingAttackersWeight[COLOR_NB];
64 // kingAdjacentZoneAttacksCount[color] is the number of attacks to squares
65 // directly adjacent to the king of the given color. Pieces which attack
66 // more than one square are counted multiple times. For instance, if black's
67 // king is on g8 and there's a white knight on g5, this knight adds
68 // 2 to kingAdjacentZoneAttacksCount[BLACK].
69 int kingAdjacentZoneAttacksCount[COLOR_NB];
71 Bitboard pinnedPieces[COLOR_NB];
76 enum Terms { // First 8 entries are for PieceType
77 MATERIAL = 8, IMBALANCE, MOBILITY, THREAT, PASSED, SPACE, TOTAL, TERMS_NB
80 Score scores[COLOR_NB][TERMS_NB];
84 double to_cp(Value v);
85 void write(int idx, Color c, Score s);
86 void write(int idx, Score w, Score b = SCORE_ZERO);
87 void print(std::stringstream& ss, const char* name, int idx);
88 std::string do_trace(const Position& pos);
91 // Evaluation weights, indexed by evaluation term
92 enum { Mobility, PawnStructure, PassedPawns, Space, KingSafety };
93 const struct Weight { int mg, eg; } Weights[] = {
94 {289, 344}, {233, 201}, {221, 273}, {46, 0}, {321, 0}
98 #define S(mg, eg) make_score(mg, eg)
100 // MobilityBonus[PieceType][attacked] contains bonuses for middle and end
101 // game, indexed by piece type and number of attacked squares not occupied by
103 const Score MobilityBonus[][32] = {
105 { S(-65,-50), S(-42,-30), S(-9,-10), S( 3, 0), S(15, 10), S(27, 20), // Knights
106 S( 37, 28), S( 42, 31), S(44, 33) },
107 { S(-52,-47), S(-28,-23), S( 6, 1), S(20, 15), S(34, 29), S(48, 43), // Bishops
108 S( 60, 55), S( 68, 63), S(74, 68), S(77, 72), S(80, 75), S(82, 77),
109 S( 84, 79), S( 86, 81) },
110 { S(-47,-53), S(-31,-26), S(-5, 0), S( 1, 16), S( 7, 32), S(13, 48), // Rooks
111 S( 18, 64), S( 22, 80), S(26, 96), S(29,109), S(31,115), S(33,119),
112 S( 35,122), S( 36,123), S(37,124) },
113 { S(-42,-40), S(-28,-23), S(-5, -7), S( 0, 0), S( 6, 10), S(11, 19), // Queens
114 S( 13, 29), S( 18, 38), S(20, 40), S(21, 41), S(22, 41), S(22, 41),
115 S( 22, 41), S( 23, 41), S(24, 41), S(25, 41), S(25, 41), S(25, 41),
116 S( 25, 41), S( 25, 41), S(25, 41), S(25, 41), S(25, 41), S(25, 41),
117 S( 25, 41), S( 25, 41), S(25, 41), S(25, 41) }
120 // Outpost[PieceType][Square] contains bonuses for knights and bishops outposts,
121 // indexed by piece type and square (from white's point of view).
122 const Value Outpost[][SQUARE_NB] = {
124 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // Knights
125 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0),
126 V(0), V(0), V(4), V(8), V(8), V(4), V(0), V(0),
127 V(0), V(4),V(17),V(26),V(26),V(17), V(4), V(0),
128 V(0), V(8),V(26),V(35),V(35),V(26), V(8), V(0),
129 V(0), V(4),V(17),V(17),V(17),V(17), V(4), V(0) },
131 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // Bishops
132 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0),
133 V(0), V(0), V(5), V(5), V(5), V(5), V(0), V(0),
134 V(0), V(5),V(10),V(10),V(10),V(10), V(5), V(0),
135 V(0),V(10),V(21),V(21),V(21),V(21),V(10), V(0),
136 V(0), V(5), V(8), V(8), V(8), V(8), V(5), V(0) }
139 // Threat[defended/weak][minor/major attacking][attacked PieceType] contains
140 // bonuses according to which piece type attacks which one.
141 const Score Threat[][2][PIECE_TYPE_NB] = {
142 { { S(0, 0), S( 0, 0), S(19, 37), S(24, 37), S(44, 97), S(35,106) }, // Defended Minor
143 { S(0, 0), S( 0, 0), S( 9, 14), S( 9, 14), S( 7, 14), S(24, 48) } }, // Defended Major
144 { { S(0, 0), S( 0,32), S(33, 41), S(31, 50), S(41,100), S(35,104) }, // Weak Minor
145 { S(0, 0), S( 0,27), S(26, 57), S(26, 57), S(0 , 43), S(23, 51) } } // Weak Major
148 // ThreatenedByPawn[PieceType] contains a penalty according to which piece
149 // type is attacked by an enemy pawn.
150 const Score ThreatenedByPawn[] = {
151 S(0, 0), S(0, 0), S(87, 118), S(84, 122), S(114, 203), S(121, 217)
154 // Assorted bonuses and penalties used by evaluation
155 const Score KingOnOne = S( 2, 58);
156 const Score KingOnMany = S( 6,125);
157 const Score RookOnPawn = S( 7, 27);
158 const Score RookOnOpenFile = S(43, 21);
159 const Score RookOnSemiOpenFile = S(19, 10);
160 const Score BishopPawns = S( 8, 12);
161 const Score MinorBehindPawn = S(16, 0);
162 const Score TrappedRook = S(92, 0);
163 const Score Unstoppable = S( 0, 20);
164 const Score Hanging = S(31, 26);
166 // Penalty for a bishop on a1/h1 (a8/h8 for black) which is trapped by
167 // a friendly pawn on b2/g2 (b7/g7 for black). This can obviously only
168 // happen in Chess960 games.
169 const Score TrappedBishopA1H1 = S(50, 50);
174 // SpaceMask[Color] contains the area of the board which is considered
175 // by the space evaluation. In the middlegame, each side is given a bonus
176 // based on how many squares inside this area are safe and available for
177 // friendly minor pieces.
178 const Bitboard SpaceMask[] = {
179 (FileCBB | FileDBB | FileEBB | FileFBB) & (Rank2BB | Rank3BB | Rank4BB),
180 (FileCBB | FileDBB | FileEBB | FileFBB) & (Rank7BB | Rank6BB | Rank5BB)
183 // King danger constants and variables. The king danger scores are looked-up
184 // in KingDanger[]. Various little "meta-bonuses" measuring the strength
185 // of the enemy attack are added up into an integer, which is used as an
186 // index to KingDanger[].
188 // KingAttackWeights[PieceType] contains king attack weights by piece type
189 const int KingAttackWeights[] = { 0, 0, 6, 2, 5, 5 };
191 // Bonuses for enemy's safe checks
192 const int QueenContactCheck = 92;
193 const int RookContactCheck = 68;
194 const int QueenCheck = 50;
195 const int RookCheck = 36;
196 const int BishopCheck = 7;
197 const int KnightCheck = 14;
199 // KingDanger[attackUnits] contains the actual king danger weighted
200 // scores, indexed by a calculated integer number.
201 Score KingDanger[512];
203 // apply_weight() weighs score 's' by weight 'w' trying to prevent overflow
204 Score apply_weight(Score s, const Weight& w) {
205 return make_score(mg_value(s) * w.mg / 256, eg_value(s) * w.eg / 256);
209 // init_eval_info() initializes king bitboards for given color adding
210 // pawn attacks. To be done at the beginning of the evaluation.
213 void init_eval_info(const Position& pos, EvalInfo& ei) {
215 const Color Them = (Us == WHITE ? BLACK : WHITE);
216 const Square Down = (Us == WHITE ? DELTA_S : DELTA_N);
218 ei.pinnedPieces[Us] = pos.pinned_pieces(Us);
220 Bitboard b = ei.attackedBy[Them][KING] = pos.attacks_from<KING>(pos.king_square(Them));
221 ei.attackedBy[Us][ALL_PIECES] = ei.attackedBy[Us][PAWN] = ei.pi->pawn_attacks(Us);
223 // Init king safety tables only if we are going to use them
224 if (pos.non_pawn_material(Us) >= QueenValueMg)
226 ei.kingRing[Them] = b | shift_bb<Down>(b);
227 b &= ei.attackedBy[Us][PAWN];
228 ei.kingAttackersCount[Us] = b ? popcount<Max15>(b) : 0;
229 ei.kingAdjacentZoneAttacksCount[Us] = ei.kingAttackersWeight[Us] = 0;
232 ei.kingRing[Them] = ei.kingAttackersCount[Us] = 0;
236 // evaluate_outpost() evaluates bishop and knight outpost squares
238 template<PieceType Pt, Color Us>
239 Score evaluate_outpost(const Position& pos, const EvalInfo& ei, Square s) {
241 const Color Them = (Us == WHITE ? BLACK : WHITE);
243 assert (Pt == BISHOP || Pt == KNIGHT);
245 // Initial bonus based on square
246 Value bonus = Outpost[Pt == BISHOP][relative_square(Us, s)];
248 // Increase bonus if supported by pawn, especially if the opponent has
249 // no minor piece which can trade with the outpost piece.
250 if (bonus && (ei.attackedBy[Us][PAWN] & s))
252 if ( !pos.pieces(Them, KNIGHT)
253 && !(squares_of_color(s) & pos.pieces(Them, BISHOP)))
254 bonus += bonus + bonus / 2;
259 return make_score(bonus * 2, bonus / 2);
263 // evaluate_pieces() assigns bonuses and penalties to the pieces of a given color
265 template<PieceType Pt, Color Us, bool Trace>
266 Score evaluate_pieces(const Position& pos, EvalInfo& ei, Score* mobility, Bitboard* mobilityArea) {
270 Score score = SCORE_ZERO;
272 const PieceType NextPt = (Us == WHITE ? Pt : PieceType(Pt + 1));
273 const Color Them = (Us == WHITE ? BLACK : WHITE);
274 const Square* pl = pos.list<Pt>(Us);
276 ei.attackedBy[Us][Pt] = 0;
278 while ((s = *pl++) != SQ_NONE)
280 // Find attacked squares, including x-ray attacks for bishops and rooks
281 b = Pt == BISHOP ? attacks_bb<BISHOP>(s, pos.pieces() ^ pos.pieces(Us, QUEEN))
282 : Pt == ROOK ? attacks_bb< ROOK>(s, pos.pieces() ^ pos.pieces(Us, ROOK, QUEEN))
283 : pos.attacks_from<Pt>(s);
285 if (ei.pinnedPieces[Us] & s)
286 b &= LineBB[pos.king_square(Us)][s];
288 ei.attackedBy[Us][ALL_PIECES] |= ei.attackedBy[Us][Pt] |= b;
290 if (b & ei.kingRing[Them])
292 ei.kingAttackersCount[Us]++;
293 ei.kingAttackersWeight[Us] += KingAttackWeights[Pt];
294 Bitboard bb = b & ei.attackedBy[Them][KING];
296 ei.kingAdjacentZoneAttacksCount[Us] += popcount<Max15>(bb);
300 b &= ~( ei.attackedBy[Them][KNIGHT]
301 | ei.attackedBy[Them][BISHOP]
302 | ei.attackedBy[Them][ROOK]);
304 int mob = Pt != QUEEN ? popcount<Max15>(b & mobilityArea[Us])
305 : popcount<Full >(b & mobilityArea[Us]);
307 mobility[Us] += MobilityBonus[Pt][mob];
309 // Decrease score if we are attacked by an enemy pawn. The remaining part
310 // of threat evaluation must be done later when we have full attack info.
311 if (ei.attackedBy[Them][PAWN] & s)
312 score -= ThreatenedByPawn[Pt];
314 if (Pt == BISHOP || Pt == KNIGHT)
316 // Bonus for outpost square
317 if (!(pos.pieces(Them, PAWN) & pawn_attack_span(Us, s)))
318 score += evaluate_outpost<Pt, Us>(pos, ei, s);
320 // Bonus when behind a pawn
321 if ( relative_rank(Us, s) < RANK_5
322 && (pos.pieces(PAWN) & (s + pawn_push(Us))))
323 score += MinorBehindPawn;
325 // Penalty for pawns on same color square of bishop
327 score -= BishopPawns * ei.pi->pawns_on_same_color_squares(Us, s);
329 // An important Chess960 pattern: A cornered bishop blocked by a friendly
330 // pawn diagonally in front of it is a very serious problem, especially
331 // when that pawn is also blocked.
334 && (s == relative_square(Us, SQ_A1) || s == relative_square(Us, SQ_H1)))
336 Square d = pawn_push(Us) + (file_of(s) == FILE_A ? DELTA_E : DELTA_W);
337 if (pos.piece_on(s + d) == make_piece(Us, PAWN))
338 score -= !pos.empty(s + d + pawn_push(Us)) ? TrappedBishopA1H1 * 4
339 : pos.piece_on(s + d + d) == make_piece(Us, PAWN) ? TrappedBishopA1H1 * 2
346 // Bonus for aligning with enemy pawns on the same rank/file
347 if (relative_rank(Us, s) >= RANK_5)
349 Bitboard alignedPawns = pos.pieces(Them, PAWN) & PseudoAttacks[ROOK][s];
351 score += popcount<Max15>(alignedPawns) * RookOnPawn;
354 // Bonus when on an open or semi-open file
355 if (ei.pi->semiopen_file(Us, file_of(s)))
356 score += ei.pi->semiopen_file(Them, file_of(s)) ? RookOnOpenFile : RookOnSemiOpenFile;
358 // Penalize when trapped by the king, even more if king cannot castle
359 if (mob <= 3 && !ei.pi->semiopen_file(Us, file_of(s)))
361 Square ksq = pos.king_square(Us);
363 if ( ((file_of(ksq) < FILE_E) == (file_of(s) < file_of(ksq)))
364 && (rank_of(ksq) == rank_of(s) || relative_rank(Us, ksq) == RANK_1)
365 && !ei.pi->semiopen_side(Us, file_of(ksq), file_of(s) < file_of(ksq)))
366 score -= (TrappedRook - make_score(mob * 22, 0)) * (1 + !pos.can_castle(Us));
372 Tracing::write(Pt, Us, score);
374 // Recursively call evaluate_pieces() of next piece type until KING excluded
375 return score - evaluate_pieces<NextPt, Them, Trace>(pos, ei, mobility, mobilityArea);
379 Score evaluate_pieces<KING, WHITE, false>(const Position&, EvalInfo&, Score*, Bitboard*) { return SCORE_ZERO; }
381 Score evaluate_pieces<KING, WHITE, true>(const Position&, EvalInfo&, Score*, Bitboard*) { return SCORE_ZERO; }
384 // evaluate_king() assigns bonuses and penalties to a king of a given color
386 template<Color Us, bool Trace>
387 Score evaluate_king(const Position& pos, const EvalInfo& ei) {
389 const Color Them = (Us == WHITE ? BLACK : WHITE);
391 Bitboard undefended, b, b1, b2, safe;
393 const Square ksq = pos.king_square(Us);
395 // King shelter and enemy pawns storm
396 Score score = ei.pi->king_safety<Us>(pos, ksq);
398 // Main king safety evaluation
399 if (ei.kingAttackersCount[Them])
401 // Find the attacked squares around the king which have no defenders
402 // apart from the king itself
403 undefended = ei.attackedBy[Them][ALL_PIECES]
404 & ei.attackedBy[Us][KING]
405 & ~( ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
406 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
407 | ei.attackedBy[Us][QUEEN]);
409 // Initialize the 'attackUnits' variable, which is used later on as an
410 // index into the KingDanger[] array. The initial value is based on the
411 // number and types of the enemy's attacking pieces, the number of
412 // attacked and undefended squares around our king and the quality of
413 // the pawn shelter (current 'score' value).
414 attackUnits = std::min(77, ei.kingAttackersCount[Them] * ei.kingAttackersWeight[Them])
415 + 10 * ei.kingAdjacentZoneAttacksCount[Them]
416 + 19 * popcount<Max15>(undefended)
417 + 9 * (ei.pinnedPieces[Us] != 0)
418 - mg_value(score) * 63 / 512
419 - !pos.count<QUEEN>(Them) * 60;
421 // Analyse the enemy's safe queen contact checks. Firstly, find the
422 // undefended squares around the king reachable by the enemy queen...
423 b = undefended & ei.attackedBy[Them][QUEEN] & ~pos.pieces(Them);
426 // ...and then remove squares not supported by another enemy piece
427 b &= ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
428 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][ROOK];
431 attackUnits += QueenContactCheck * popcount<Max15>(b);
434 // Analyse the enemy's safe rook contact checks. Firstly, find the
435 // undefended squares around the king reachable by the enemy rooks...
436 b = undefended & ei.attackedBy[Them][ROOK] & ~pos.pieces(Them);
438 // Consider only squares where the enemy's rook gives check
439 b &= PseudoAttacks[ROOK][ksq];
443 // ...and then remove squares not supported by another enemy piece
444 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
445 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][QUEEN]);
448 attackUnits += RookContactCheck * popcount<Max15>(b);
451 // Analyse the enemy's safe distance checks for sliders and knights
452 safe = ~(ei.attackedBy[Us][ALL_PIECES] | pos.pieces(Them));
454 b1 = pos.attacks_from<ROOK >(ksq) & safe;
455 b2 = pos.attacks_from<BISHOP>(ksq) & safe;
457 // Enemy queen safe checks
458 b = (b1 | b2) & ei.attackedBy[Them][QUEEN];
460 attackUnits += QueenCheck * popcount<Max15>(b);
462 // Enemy rooks safe checks
463 b = b1 & ei.attackedBy[Them][ROOK];
465 attackUnits += RookCheck * popcount<Max15>(b);
467 // Enemy bishops safe checks
468 b = b2 & ei.attackedBy[Them][BISHOP];
470 attackUnits += BishopCheck * popcount<Max15>(b);
472 // Enemy knights safe checks
473 b = pos.attacks_from<KNIGHT>(ksq) & ei.attackedBy[Them][KNIGHT] & safe;
475 attackUnits += KnightCheck * popcount<Max15>(b);
477 // Finally, extract the king danger score from the KingDanger[]
478 // array and subtract the score from evaluation.
479 score -= KingDanger[std::max(std::min(attackUnits, 399), 0)];
483 Tracing::write(KING, Us, score);
489 // evaluate_threats() assigns bonuses according to the type of attacking piece
490 // and the type of attacked one.
492 template<Color Us, bool Trace>
493 Score evaluate_threats(const Position& pos, const EvalInfo& ei) {
495 const Color Them = (Us == WHITE ? BLACK : WHITE);
497 enum { Defended, Weak };
498 enum { Minor, Major };
500 Bitboard b, weak, defended;
501 Score score = SCORE_ZERO;
503 // Non-pawn enemies defended by a pawn
504 defended = (pos.pieces(Them) ^ pos.pieces(Them, PAWN))
505 & ei.attackedBy[Them][PAWN];
507 // Add a bonus according to the kind of attacking pieces
510 b = defended & (ei.attackedBy[Us][KNIGHT] | ei.attackedBy[Us][BISHOP]);
512 score += Threat[Defended][Minor][type_of(pos.piece_on(pop_lsb(&b)))];
514 b = defended & (ei.attackedBy[Us][ROOK]);
516 score += Threat[Defended][Major][type_of(pos.piece_on(pop_lsb(&b)))];
519 // Enemies not defended by a pawn and under our attack
520 weak = pos.pieces(Them)
521 & ~ei.attackedBy[Them][PAWN]
522 & ei.attackedBy[Us][ALL_PIECES];
524 // Add a bonus according to the kind of attacking pieces
527 b = weak & (ei.attackedBy[Us][KNIGHT] | ei.attackedBy[Us][BISHOP]);
529 score += Threat[Weak][Minor][type_of(pos.piece_on(pop_lsb(&b)))];
531 b = weak & (ei.attackedBy[Us][ROOK] | ei.attackedBy[Us][QUEEN]);
533 score += Threat[Weak][Major][type_of(pos.piece_on(pop_lsb(&b)))];
535 b = weak & ~ei.attackedBy[Them][ALL_PIECES];
537 score += Hanging * popcount<Max15>(b);
539 b = weak & ei.attackedBy[Us][KING];
541 score += more_than_one(b) ? KingOnMany : KingOnOne;
545 Tracing::write(Tracing::THREAT, Us, score);
551 // evaluate_passed_pawns() evaluates the passed pawns of the given color
553 template<Color Us, bool Trace>
554 Score evaluate_passed_pawns(const Position& pos, const EvalInfo& ei) {
556 const Color Them = (Us == WHITE ? BLACK : WHITE);
558 Bitboard b, squaresToQueen, defendedSquares, unsafeSquares;
559 Score score = SCORE_ZERO;
561 b = ei.pi->passed_pawns(Us);
565 Square s = pop_lsb(&b);
567 assert(pos.pawn_passed(Us, s));
569 int r = relative_rank(Us, s) - RANK_2;
570 int rr = r * (r - 1);
572 // Base bonus based on rank
573 Value mbonus = Value(17 * rr), ebonus = Value(7 * (rr + r + 1));
577 Square blockSq = s + pawn_push(Us);
579 // Adjust bonus based on the king's proximity
580 ebonus += distance(pos.king_square(Them), blockSq) * 5 * rr
581 - distance(pos.king_square(Us ), blockSq) * 2 * rr;
583 // If blockSq is not the queening square then consider also a second push
584 if (relative_rank(Us, blockSq) != RANK_8)
585 ebonus -= distance(pos.king_square(Us), blockSq + pawn_push(Us)) * rr;
587 // If the pawn is free to advance, then increase the bonus
588 if (pos.empty(blockSq))
590 // If there is a rook or queen attacking/defending the pawn from behind,
591 // consider all the squaresToQueen. Otherwise consider only the squares
592 // in the pawn's path attacked or occupied by the enemy.
593 defendedSquares = unsafeSquares = squaresToQueen = forward_bb(Us, s);
595 Bitboard bb = forward_bb(Them, s) & pos.pieces(ROOK, QUEEN) & pos.attacks_from<ROOK>(s);
597 if (!(pos.pieces(Us) & bb))
598 defendedSquares &= ei.attackedBy[Us][ALL_PIECES];
600 if (!(pos.pieces(Them) & bb))
601 unsafeSquares &= ei.attackedBy[Them][ALL_PIECES] | pos.pieces(Them);
603 // If there aren't any enemy attacks, assign a big bonus. Otherwise
604 // assign a smaller bonus if the block square isn't attacked.
605 int k = !unsafeSquares ? 15 : !(unsafeSquares & blockSq) ? 9 : 0;
607 // If the path to queen is fully defended, assign a big bonus.
608 // Otherwise assign a smaller bonus if the block square is defended.
609 if (defendedSquares == squaresToQueen)
612 else if (defendedSquares & blockSq)
615 mbonus += k * rr, ebonus += k * rr;
617 else if (pos.pieces(Us) & blockSq)
618 mbonus += rr * 3 + r * 2 + 3, ebonus += rr + r * 2;
621 if (pos.count<PAWN>(Us) < pos.count<PAWN>(Them))
622 ebonus += ebonus / 4;
624 score += make_score(mbonus, ebonus);
628 Tracing::write(Tracing::PASSED, Us, apply_weight(score, Weights[PassedPawns]));
630 // Add the scores to the middlegame and endgame eval
631 return apply_weight(score, Weights[PassedPawns]);
635 // evaluate_space() computes the space evaluation for a given side. The
636 // space evaluation is a simple bonus based on the number of safe squares
637 // available for minor pieces on the central four files on ranks 2--4. Safe
638 // squares one, two or three squares behind a friendly pawn are counted
639 // twice. Finally, the space bonus is multiplied by a weight. The aim is to
640 // improve play on game opening.
642 Score evaluate_space(const Position& pos, const EvalInfo& ei) {
644 const Color Them = (Us == WHITE ? BLACK : WHITE);
646 // Find the safe squares for our pieces inside the area defined by
647 // SpaceMask[]. A square is unsafe if it is attacked by an enemy
648 // pawn, or if it is undefended and attacked by an enemy piece.
649 Bitboard safe = SpaceMask[Us]
650 & ~pos.pieces(Us, PAWN)
651 & ~ei.attackedBy[Them][PAWN]
652 & (ei.attackedBy[Us][ALL_PIECES] | ~ei.attackedBy[Them][ALL_PIECES]);
654 // Find all squares which are at most three squares behind some friendly pawn
655 Bitboard behind = pos.pieces(Us, PAWN);
656 behind |= (Us == WHITE ? behind >> 8 : behind << 8);
657 behind |= (Us == WHITE ? behind >> 16 : behind << 16);
659 // Since SpaceMask[Us] is fully on our half of the board
660 assert(unsigned(safe >> (Us == WHITE ? 32 : 0)) == 0);
662 // Count safe + (behind & safe) with a single popcount
663 int bonus = popcount<Full>((Us == WHITE ? safe << 32 : safe >> 32) | (behind & safe));
664 int weight = pos.count<KNIGHT>(Us) + pos.count<BISHOP>(Us)
665 + pos.count<KNIGHT>(Them) + pos.count<BISHOP>(Them);
667 return make_score(bonus * weight * weight, 0);
671 // do_evaluate() is the evaluation entry point, called directly from evaluate()
674 Value do_evaluate(const Position& pos) {
676 assert(!pos.checkers());
679 Score score, mobility[2] = { SCORE_ZERO, SCORE_ZERO };
681 // Initialize score by reading the incrementally updated scores included
682 // in the position object (material + piece square tables).
683 // Score is computed from the point of view of white.
684 score = pos.psq_score();
686 // Probe the material hash table
687 ei.mi = Material::probe(pos);
688 score += ei.mi->imbalance();
690 // If we have a specialized evaluation function for the current material
691 // configuration, call it and return.
692 if (ei.mi->specialized_eval_exists())
693 return ei.mi->evaluate(pos);
695 // Probe the pawn hash table
696 ei.pi = Pawns::probe(pos);
697 score += apply_weight(ei.pi->pawns_score(), Weights[PawnStructure]);
699 // Initialize attack and king safety bitboards
700 init_eval_info<WHITE>(pos, ei);
701 init_eval_info<BLACK>(pos, ei);
703 ei.attackedBy[WHITE][ALL_PIECES] |= ei.attackedBy[WHITE][KING];
704 ei.attackedBy[BLACK][ALL_PIECES] |= ei.attackedBy[BLACK][KING];
706 // Do not include in mobility squares protected by enemy pawns or occupied by our pawns or king
707 Bitboard mobilityArea[] = { ~(ei.attackedBy[BLACK][PAWN] | pos.pieces(WHITE, PAWN, KING)),
708 ~(ei.attackedBy[WHITE][PAWN] | pos.pieces(BLACK, PAWN, KING)) };
710 // Evaluate pieces and mobility
711 score += evaluate_pieces<KNIGHT, WHITE, Trace>(pos, ei, mobility, mobilityArea);
712 score += apply_weight(mobility[WHITE] - mobility[BLACK], Weights[Mobility]);
714 // Evaluate kings after all other pieces because we need complete attack
715 // information when computing the king safety evaluation.
716 score += evaluate_king<WHITE, Trace>(pos, ei)
717 - evaluate_king<BLACK, Trace>(pos, ei);
719 // Evaluate tactical threats, we need full attack information including king
720 score += evaluate_threats<WHITE, Trace>(pos, ei)
721 - evaluate_threats<BLACK, Trace>(pos, ei);
723 // Evaluate passed pawns, we need full attack information including king
724 score += evaluate_passed_pawns<WHITE, Trace>(pos, ei)
725 - evaluate_passed_pawns<BLACK, Trace>(pos, ei);
727 // If both sides have only pawns, score for potential unstoppable pawns
728 if (!pos.non_pawn_material(WHITE) && !pos.non_pawn_material(BLACK))
731 if ((b = ei.pi->passed_pawns(WHITE)) != 0)
732 score += int(relative_rank(WHITE, frontmost_sq(WHITE, b))) * Unstoppable;
734 if ((b = ei.pi->passed_pawns(BLACK)) != 0)
735 score -= int(relative_rank(BLACK, frontmost_sq(BLACK, b))) * Unstoppable;
738 // Evaluate space for both sides, only during opening
739 if (pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK) >= 2 * QueenValueMg + 4 * RookValueMg + 2 * KnightValueMg)
741 Score s = evaluate_space<WHITE>(pos, ei) - evaluate_space<BLACK>(pos, ei);
742 score += apply_weight(s, Weights[Space]);
745 // Scale winning side if position is more drawish than it appears
746 Color strongSide = eg_value(score) > VALUE_DRAW ? WHITE : BLACK;
747 ScaleFactor sf = ei.mi->scale_factor(pos, strongSide);
749 // If we don't already have an unusual scale factor, check for certain
750 // types of endgames, and use a lower scale for those.
751 if ( ei.mi->game_phase() < PHASE_MIDGAME
752 && (sf == SCALE_FACTOR_NORMAL || sf == SCALE_FACTOR_ONEPAWN))
754 if (pos.opposite_bishops())
756 // Endgame with opposite-colored bishops and no other pieces (ignoring pawns)
757 // is almost a draw, in case of KBP vs KB is even more a draw.
758 if ( pos.non_pawn_material(WHITE) == BishopValueMg
759 && pos.non_pawn_material(BLACK) == BishopValueMg)
760 sf = more_than_one(pos.pieces(PAWN)) ? ScaleFactor(32) : ScaleFactor(8);
762 // Endgame with opposite-colored bishops, but also other pieces. Still
763 // a bit drawish, but not as drawish as with only the two bishops.
765 sf = ScaleFactor(50 * sf / SCALE_FACTOR_NORMAL);
767 // Endings where weaker side can place his king in front of the opponent's
768 // pawns are drawish.
769 else if ( abs(eg_value(score)) <= BishopValueEg
770 && ei.pi->pawn_span(strongSide) <= 1
771 && !pos.pawn_passed(~strongSide, pos.king_square(~strongSide)))
772 sf = ei.pi->pawn_span(strongSide) ? ScaleFactor(56) : ScaleFactor(38);
775 // Interpolate between a middlegame and a (scaled by 'sf') endgame score
776 Value v = mg_value(score) * int(ei.mi->game_phase())
777 + eg_value(score) * int(PHASE_MIDGAME - ei.mi->game_phase()) * sf / SCALE_FACTOR_NORMAL;
779 v /= int(PHASE_MIDGAME);
781 // In case of tracing add all single evaluation contributions for both white and black
784 Tracing::write(Tracing::MATERIAL, pos.psq_score());
785 Tracing::write(Tracing::IMBALANCE, ei.mi->imbalance());
786 Tracing::write(PAWN, ei.pi->pawns_score());
787 Tracing::write(Tracing::MOBILITY, apply_weight(mobility[WHITE], Weights[Mobility])
788 , apply_weight(mobility[BLACK], Weights[Mobility]));
789 Tracing::write(Tracing::SPACE, apply_weight(evaluate_space<WHITE>(pos, ei), Weights[Space])
790 , apply_weight(evaluate_space<BLACK>(pos, ei), Weights[Space]));
791 Tracing::write(Tracing::TOTAL, score);
796 return (pos.side_to_move() == WHITE ? v : -v) + Eval::Tempo;
800 // Tracing function definitions
802 double Tracing::to_cp(Value v) { return double(v) / PawnValueEg; }
804 void Tracing::write(int idx, Color c, Score s) { scores[c][idx] = s; }
806 void Tracing::write(int idx, Score w, Score b) {
808 write(idx, WHITE, w);
809 write(idx, BLACK, b);
812 void Tracing::print(std::stringstream& ss, const char* name, int idx) {
814 Score wScore = scores[WHITE][idx];
815 Score bScore = scores[BLACK][idx];
818 case MATERIAL: case IMBALANCE: case PAWN: case TOTAL:
819 ss << std::setw(15) << name << " | --- --- | --- --- | "
820 << std::setw(5) << to_cp(mg_value(wScore - bScore)) << " "
821 << std::setw(5) << to_cp(eg_value(wScore - bScore)) << " \n";
824 ss << std::setw(15) << name << " | " << std::noshowpos
825 << std::setw(5) << to_cp(mg_value(wScore)) << " "
826 << std::setw(5) << to_cp(eg_value(wScore)) << " | "
827 << std::setw(5) << to_cp(mg_value(bScore)) << " "
828 << std::setw(5) << to_cp(eg_value(bScore)) << " | "
829 << std::setw(5) << to_cp(mg_value(wScore - bScore)) << " "
830 << std::setw(5) << to_cp(eg_value(wScore - bScore)) << " \n";
834 std::string Tracing::do_trace(const Position& pos) {
836 std::memset(scores, 0, sizeof(scores));
838 Value v = do_evaluate<true>(pos);
839 v = pos.side_to_move() == WHITE ? v : -v; // White's point of view
841 std::stringstream ss;
842 ss << std::showpoint << std::noshowpos << std::fixed << std::setprecision(2)
843 << " Eval term | White | Black | Total \n"
844 << " | MG EG | MG EG | MG EG \n"
845 << "----------------+-------------+-------------+-------------\n";
847 print(ss, "Material", MATERIAL);
848 print(ss, "Imbalance", IMBALANCE);
849 print(ss, "Pawns", PAWN);
850 print(ss, "Knights", KNIGHT);
851 print(ss, "Bishops", BISHOP);
852 print(ss, "Rooks", ROOK);
853 print(ss, "Queens", QUEEN);
854 print(ss, "Mobility", MOBILITY);
855 print(ss, "King safety", KING);
856 print(ss, "Threats", THREAT);
857 print(ss, "Passed pawns", PASSED);
858 print(ss, "Space", SPACE);
860 ss << "----------------+-------------+-------------+-------------\n";
861 print(ss, "Total", TOTAL);
863 ss << "\nTotal Evaluation: " << to_cp(v) << " (white side)\n";
873 /// evaluate() is the main evaluation function. It returns a static evaluation
874 /// of the position always from the point of view of the side to move.
876 Value evaluate(const Position& pos) {
877 return do_evaluate<false>(pos);
881 /// trace() is like evaluate(), but instead of returning a value, it returns
882 /// a string (suitable for outputting to stdout) that contains the detailed
883 /// descriptions and values of each evaluation term. It's mainly used for
885 std::string trace(const Position& pos) {
886 return Tracing::do_trace(pos);
890 /// init() computes evaluation weights, usually at startup
894 const double MaxSlope = 7.5;
895 const double Peak = 1280;
898 for (int i = 1; i < 400; ++i)
900 t = std::min(Peak, std::min(0.025 * i * i, t + MaxSlope));
901 KingDanger[i] = apply_weight(make_score(int(t), 0), Weights[KingSafety]);