2 Stockfish, a UCI chess playing engine derived from Glaurung 2.1
3 Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
4 Copyright (C) 2008-2014 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/>.
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 variables
61 // QueenAttackWeight, RookAttackWeight, BishopAttackWeight and
62 // KnightAttackWeight in evaluate.cpp
63 int kingAttackersWeight[COLOR_NB];
65 // kingAdjacentZoneAttacksCount[color] is the number of attacks to squares
66 // directly adjacent to the king of the given color. Pieces which attack
67 // more than one square are counted multiple times. For instance, if black's
68 // king is on g8 and there's a white knight on g5, this knight adds
69 // 2 to kingAdjacentZoneAttacksCount[BLACK].
70 int kingAdjacentZoneAttacksCount[COLOR_NB];
72 Bitboard pinnedPieces[COLOR_NB];
77 enum Terms { // First 8 entries are for PieceType
78 MATERIAL = 8, IMBALANCE, MOBILITY, THREAT, PASSED, SPACE, TOTAL, TERMS_NB
81 Score scores[COLOR_NB][TERMS_NB];
85 double to_cp(Value v);
86 void write(int idx, Color c, Score s);
87 void write(int idx, Score w, Score b = SCORE_ZERO);
88 void print(std::stringstream& ss, const char* name, int idx);
89 std::string do_trace(const Position& pos);
92 // Evaluation weights, indexed by evaluation term
93 enum { Mobility, PawnStructure, PassedPawns, Space, KingSafety };
94 const struct Weight { int mg, eg; } Weights[] = {
95 {289, 344}, {233, 201}, {221, 273}, {46, 0}, {318, 0}
99 #define S(mg, eg) make_score(mg, eg)
101 // MobilityBonus[PieceType][attacked] contains bonuses for middle and end
102 // game, indexed by piece type and number of attacked squares not occupied by
104 const Score MobilityBonus[][32] = {
106 { S(-65,-50), S(-42,-30), S(-9,-10), S( 3, 0), S(15, 10), S(27, 20), // Knights
107 S( 37, 28), S( 42, 31), S(44, 33) },
108 { S(-52,-47), S(-28,-23), S( 6, 1), S(20, 15), S(34, 29), S(48, 43), // Bishops
109 S( 60, 55), S( 68, 63), S(74, 68), S(77, 72), S(80, 75), S(82, 77),
110 S( 84, 79), S( 86, 81) },
111 { S(-47,-53), S(-31,-26), S(-5, 0), S( 1, 16), S( 7, 32), S(13, 48), // Rooks
112 S( 18, 64), S( 22, 80), S(26, 96), S(29,109), S(31,115), S(33,119),
113 S( 35,122), S( 36,123), S(37,124) },
114 { S(-42,-40), S(-28,-23), S(-5, -7), S( 0, 0), S( 6, 10), S(11, 19), // Queens
115 S( 13, 29), S( 18, 38), S(20, 40), S(21, 41), S(22, 41), S(22, 41),
116 S( 22, 41), S( 23, 41), S(24, 41), S(25, 41), S(25, 41), S(25, 41),
117 S( 25, 41), S( 25, 41), S(25, 41), S(25, 41), S(25, 41), S(25, 41),
118 S( 25, 41), S( 25, 41), S(25, 41), S(25, 41) }
121 // Outpost[PieceType][Square] contains bonuses for knights and bishops outposts,
122 // indexed by piece type and square (from white's point of view).
123 const Value Outpost[][SQUARE_NB] = {
125 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // Knights
126 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0),
127 V(0), V(0), V(4), V(8), V(8), V(4), V(0), V(0),
128 V(0), V(4),V(17),V(26),V(26),V(17), V(4), V(0),
129 V(0), V(8),V(26),V(35),V(35),V(26), V(8), V(0),
130 V(0), V(4),V(17),V(17),V(17),V(17), V(4), V(0) },
132 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // Bishops
133 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0),
134 V(0), V(0), V(5), V(5), V(5), V(5), V(0), V(0),
135 V(0), V(5),V(10),V(10),V(10),V(10), V(5), V(0),
136 V(0),V(10),V(21),V(21),V(21),V(21),V(10), V(0),
137 V(0), V(5), V(8), V(8), V(8), V(8), V(5), V(0) }
140 // Threat[attacking][attacked] contains bonuses according to which piece
141 // type attacks which one.
142 const Score Threat[][PIECE_TYPE_NB] = {
143 { S(0, 0), S(0, 38), S(32, 45), S(32, 45), S(41,100), S(35,104) }, // Minor
144 { S(0, 0), S(7, 28), S(20, 49), S(20, 49), S(8 , 42), S(23, 44) } // Major
147 // ThreatenedByPawn[PieceType] contains a penalty according to which piece
148 // type is attacked by an enemy pawn.
149 const Score ThreatenedByPawn[] = {
150 S(0, 0), S(0, 0), S(80, 119), S(80, 119), S(117, 199), S(127, 218)
153 // Assorted bonuses and penalties used by evaluation
154 const Score KingOnOne = S(2 , 58);
155 const Score KingOnMany = S(6 ,125);
156 const Score RookOnPawn = S(10, 28);
157 const Score RookOpenFile = S(43, 21);
158 const Score RookSemiOpenFile = S(19, 10);
159 const Score BishopPawns = S( 8, 12);
160 const Score MinorBehindPawn = S(16, 0);
161 const Score TrappedRook = S(92, 0);
162 const Score Unstoppable = S( 0, 20);
163 const Score Hanging = S(23, 20);
165 // Penalty for a bishop on a1/h1 (a8/h8 for black) which is trapped by
166 // a friendly pawn on b2/g2 (b7/g7 for black). This can obviously only
167 // happen in Chess960 games.
168 const Score TrappedBishopA1H1 = S(50, 50);
172 // SpaceMask[Color] contains the area of the board which is considered
173 // by the space evaluation. In the middlegame, each side is given a bonus
174 // based on how many squares inside this area are safe and available for
175 // friendly minor pieces.
176 const Bitboard SpaceMask[] = {
177 (FileCBB | FileDBB | FileEBB | FileFBB) & (Rank2BB | Rank3BB | Rank4BB),
178 (FileCBB | FileDBB | FileEBB | FileFBB) & (Rank7BB | Rank6BB | Rank5BB)
181 // King danger constants and variables. The king danger scores are taken
182 // from KingDanger[]. Various little "meta-bonuses" measuring the strength
183 // of the enemy attack are added up into an integer, which is used as an
184 // index to KingDanger[].
186 // KingAttackWeights[PieceType] contains king attack weights by piece type
187 const int KingAttackWeights[] = { 0, 0, 2, 2, 3, 5 };
189 // Bonuses for enemy's safe checks
190 const int QueenContactCheck = 24;
191 const int RookContactCheck = 16;
192 const int QueenCheck = 12;
193 const int RookCheck = 8;
194 const int BishopCheck = 2;
195 const int KnightCheck = 3;
197 // KingDanger[attackUnits] contains the actual king danger weighted
198 // scores, indexed by a calculated integer number.
199 Score KingDanger[128];
201 const int ScalePawnSpan[2] = { 38, 56 };
203 // apply_weight() weighs score 'v' by weight 'w' trying to prevent overflow
204 Score apply_weight(Score v, const Weight& w) {
205 return make_score(mg_value(v) * w.mg / 256, eg_value(v) * 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 + PawnValueMg)
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 // Penalty for bishop with same colored pawns
318 score -= BishopPawns * ei.pi->pawns_on_same_color_squares(Us, s);
320 // Bishop and knight outpost square
321 if (!(pos.pieces(Them, PAWN) & pawn_attack_span(Us, s)))
322 score += evaluate_outpost<Pt, Us>(pos, ei, s);
324 // Bishop or knight behind a pawn
325 if ( relative_rank(Us, s) < RANK_5
326 && (pos.pieces(PAWN) & (s + pawn_push(Us))))
327 score += MinorBehindPawn;
332 // Rook piece attacking enemy pawns on the same rank/file
333 if (relative_rank(Us, s) >= RANK_5)
335 Bitboard pawns = pos.pieces(Them, PAWN) & PseudoAttacks[ROOK][s];
337 score += popcount<Max15>(pawns) * RookOnPawn;
340 // Give a bonus for a rook on a open or semi-open file
341 if (ei.pi->semiopen_file(Us, file_of(s)))
342 score += ei.pi->semiopen_file(Them, file_of(s)) ? RookOpenFile : RookSemiOpenFile;
344 if (mob > 3 || ei.pi->semiopen_file(Us, file_of(s)))
347 Square ksq = pos.king_square(Us);
349 // Penalize rooks which are trapped by a king. Penalize more if the
350 // king has lost its castling capability.
351 if ( ((file_of(ksq) < FILE_E) == (file_of(s) < file_of(ksq)))
352 && (rank_of(ksq) == rank_of(s) || relative_rank(Us, ksq) == RANK_1)
353 && !ei.pi->semiopen_side(Us, file_of(ksq), file_of(s) < file_of(ksq)))
354 score -= (TrappedRook - make_score(mob * 22, 0)) * (1 + !pos.can_castle(Us));
357 // An important Chess960 pattern: A cornered bishop blocked by a friendly
358 // pawn diagonally in front of it is a very serious problem, especially
359 // when that pawn is also blocked.
362 && (s == relative_square(Us, SQ_A1) || s == relative_square(Us, SQ_H1)))
364 Square d = pawn_push(Us) + (file_of(s) == FILE_A ? DELTA_E : DELTA_W);
365 if (pos.piece_on(s + d) == make_piece(Us, PAWN))
366 score -= !pos.empty(s + d + pawn_push(Us)) ? TrappedBishopA1H1 * 4
367 : pos.piece_on(s + d + d) == make_piece(Us, PAWN) ? TrappedBishopA1H1 * 2
373 Tracing::write(Pt, Us, score);
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 to 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(20, (ei.kingAttackersCount[Them] * ei.kingAttackersWeight[Them]) / 2)
415 + 3 * (ei.kingAdjacentZoneAttacksCount[Them] + popcount<Max15>(undefended))
416 + 2 * (ei.pinnedPieces[Us] != 0)
417 - mg_value(score) / 32
418 - !pos.count<QUEEN>(Them) * 15;
420 // Analyse the enemy's safe queen contact checks. Firstly, find the
421 // undefended squares around the king that are attacked by the enemy's
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 that are attacked by the enemy's
437 b = undefended & ei.attackedBy[Them][ROOK] & ~pos.pieces(Them);
439 // Consider only squares where the enemy's rook gives check
440 b &= PseudoAttacks[ROOK][ksq];
444 // ...and then remove squares not supported by another enemy piece
445 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
446 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][QUEEN]);
449 attackUnits += RookContactCheck * popcount<Max15>(b);
452 // Analyse the enemy's safe distance checks for sliders and knights
453 safe = ~(pos.pieces(Them) | ei.attackedBy[Us][ALL_PIECES]);
455 b1 = pos.attacks_from<ROOK>(ksq) & safe;
456 b2 = pos.attacks_from<BISHOP>(ksq) & safe;
458 // Enemy queen safe checks
459 b = (b1 | b2) & ei.attackedBy[Them][QUEEN];
461 attackUnits += QueenCheck * popcount<Max15>(b);
463 // Enemy rooks safe checks
464 b = b1 & ei.attackedBy[Them][ROOK];
466 attackUnits += RookCheck * popcount<Max15>(b);
468 // Enemy bishops safe checks
469 b = b2 & ei.attackedBy[Them][BISHOP];
471 attackUnits += BishopCheck * popcount<Max15>(b);
473 // Enemy knights safe checks
474 b = pos.attacks_from<KNIGHT>(ksq) & ei.attackedBy[Them][KNIGHT] & safe;
476 attackUnits += KnightCheck * popcount<Max15>(b);
478 // To index KingDanger[] attackUnits must be in [0, 99] range
479 attackUnits = std::min(99, std::max(0, attackUnits));
481 // Finally, extract the king danger score from the KingDanger[]
482 // array and subtract the score from evaluation.
483 score -= KingDanger[attackUnits];
487 Tracing::write(KING, Us, score);
493 // max_piece_type() is a helper function used by evaluate_threats() to get
494 // the value of the biggest PieceType of color C in 'target' bitboard.
497 inline PieceType max_piece_type(const Position& pos, const Bitboard target) {
499 assert(target & (pos.pieces(C) ^ pos.pieces(C, KING)));
501 for (PieceType pt = QUEEN; pt > PAWN; --pt)
502 if (target & pos.pieces(C, pt))
509 // evaluate_threats() assigns bonuses according to the type of attacking piece
510 // and the type of attacked one.
512 template<Color Us, bool Trace>
513 Score evaluate_threats(const Position& pos, const EvalInfo& ei) {
515 const Color Them = (Us == WHITE ? BLACK : WHITE);
517 enum { Minor, Major };
519 Bitboard b, weakEnemies, protectedEnemies;
520 Score score = SCORE_ZERO;
522 // Enemies defended by a pawn and under our attack by a minor piece
523 protectedEnemies = (pos.pieces(Them) ^ pos.pieces(Them, PAWN))
524 & ei.attackedBy[Them][PAWN]
525 & (ei.attackedBy[Us][KNIGHT] | ei.attackedBy[Us][BISHOP]);
527 if (protectedEnemies)
528 score += Threat[Minor][max_piece_type<Them>(pos, protectedEnemies)];
530 // Enemies not defended by a pawn and under our attack
531 weakEnemies = pos.pieces(Them)
532 & ~ei.attackedBy[Them][PAWN]
533 & ei.attackedBy[Us][ALL_PIECES];
535 // Add a bonus according if the attacking pieces are minor or major
538 b = weakEnemies & (ei.attackedBy[Us][KNIGHT] | ei.attackedBy[Us][BISHOP]);
540 score += Threat[Minor][max_piece_type<Them>(pos, b)];
542 b = weakEnemies & (ei.attackedBy[Us][ROOK] | ei.attackedBy[Us][QUEEN]);
544 score += Threat[Major][max_piece_type<Them>(pos, b)];
546 b = weakEnemies & ~ei.attackedBy[Them][ALL_PIECES];
548 score += more_than_one(b) ? Hanging * popcount<Max15>(b) : Hanging;
550 b = weakEnemies & ei.attackedBy[Us][KING];
552 score += more_than_one(b) ? KingOnMany : KingOnOne;
556 Tracing::write(Tracing::THREAT, Us, score);
562 // evaluate_passed_pawns() evaluates the passed pawns of the given color
564 template<Color Us, bool Trace>
565 Score evaluate_passed_pawns(const Position& pos, const EvalInfo& ei) {
567 const Color Them = (Us == WHITE ? BLACK : WHITE);
569 Bitboard b, squaresToQueen, defendedSquares, unsafeSquares;
570 Score score = SCORE_ZERO;
572 b = ei.pi->passed_pawns(Us);
576 Square s = pop_lsb(&b);
578 assert(pos.pawn_passed(Us, s));
580 int r = relative_rank(Us, s) - RANK_2;
581 int rr = r * (r - 1);
583 // Base bonus based on rank
584 Value mbonus = Value(17 * rr), ebonus = Value(7 * (rr + r + 1));
588 Square blockSq = s + pawn_push(Us);
590 // Adjust bonus based on the king's proximity
591 ebonus += square_distance(pos.king_square(Them), blockSq) * 5 * rr
592 - square_distance(pos.king_square(Us ), blockSq) * 2 * rr;
594 // If blockSq is not the queening square then consider also a second push
595 if (relative_rank(Us, blockSq) != RANK_8)
596 ebonus -= square_distance(pos.king_square(Us), blockSq + pawn_push(Us)) * rr;
598 // If the pawn is free to advance, then increase the bonus
599 if (pos.empty(blockSq))
601 // If there is a rook or queen attacking/defending the pawn from behind,
602 // consider all the squaresToQueen. Otherwise consider only the squares
603 // in the pawn's path attacked or occupied by the enemy.
604 defendedSquares = unsafeSquares = squaresToQueen = forward_bb(Us, s);
606 Bitboard bb = forward_bb(Them, s) & pos.pieces(ROOK, QUEEN) & pos.attacks_from<ROOK>(s);
608 if (!(pos.pieces(Us) & bb))
609 defendedSquares &= ei.attackedBy[Us][ALL_PIECES];
611 if (!(pos.pieces(Them) & bb))
612 unsafeSquares &= ei.attackedBy[Them][ALL_PIECES] | pos.pieces(Them);
614 // If there aren't any enemy attacks, assign a big bonus. Otherwise
615 // assign a smaller bonus if the block square isn't attacked.
616 int k = !unsafeSquares ? 15 : !(unsafeSquares & blockSq) ? 9 : 0;
618 // If the path to queen is fully defended, assign a big bonus.
619 // Otherwise assign a smaller bonus if the block square is defended.
620 if (defendedSquares == squaresToQueen)
623 else if (defendedSquares & blockSq)
626 mbonus += k * rr, ebonus += k * rr;
628 else if (pos.pieces(Us) & blockSq)
629 mbonus += rr * 3 + r * 2 + 3, ebonus += rr + r * 2;
632 if (pos.count<PAWN>(Us) < pos.count<PAWN>(Them))
633 ebonus += ebonus / 4;
635 score += make_score(mbonus, ebonus);
639 Tracing::write(Tracing::PASSED, Us, apply_weight(score, Weights[PassedPawns]));
641 // Add the scores to the middlegame and endgame eval
642 return apply_weight(score, Weights[PassedPawns]);
646 // evaluate_unstoppable_pawns() scores the most advanced passed pawn. In case
647 // both players have no pieces but pawns, this is somewhat related to the
648 // possibility that pawns are unstoppable.
650 Score evaluate_unstoppable_pawns(Color us, const EvalInfo& ei) {
652 Bitboard b = ei.pi->passed_pawns(us);
654 return b ? Unstoppable * int(relative_rank(us, frontmost_sq(us, b))) : SCORE_ZERO;
658 // evaluate_space() computes the space evaluation for a given side. The
659 // space evaluation is a simple bonus based on the number of safe squares
660 // available for minor pieces on the central four files on ranks 2--4. Safe
661 // squares one, two or three squares behind a friendly pawn are counted
662 // twice. Finally, the space bonus is scaled by a weight taken from the
663 // material hash table. The aim is to improve play on game opening.
665 int evaluate_space(const Position& pos, const EvalInfo& ei) {
667 const Color Them = (Us == WHITE ? BLACK : WHITE);
669 // Find the safe squares for our pieces inside the area defined by
670 // SpaceMask[]. A square is unsafe if it is attacked by an enemy
671 // pawn, or if it is undefended and attacked by an enemy piece.
672 Bitboard safe = SpaceMask[Us]
673 & ~pos.pieces(Us, PAWN)
674 & ~ei.attackedBy[Them][PAWN]
675 & (ei.attackedBy[Us][ALL_PIECES] | ~ei.attackedBy[Them][ALL_PIECES]);
677 // Find all squares which are at most three squares behind some friendly pawn
678 Bitboard behind = pos.pieces(Us, PAWN);
679 behind |= (Us == WHITE ? behind >> 8 : behind << 8);
680 behind |= (Us == WHITE ? behind >> 16 : behind << 16);
682 // Since SpaceMask[Us] is fully on our half of the board
683 assert(unsigned(safe >> (Us == WHITE ? 32 : 0)) == 0);
685 // Count safe + (behind & safe) with a single popcount
686 return popcount<Full>((Us == WHITE ? safe << 32 : safe >> 32) | (behind & safe));
690 // do_evaluate() is the evaluation entry point, called directly from evaluate()
693 Value do_evaluate(const Position& pos) {
695 assert(!pos.checkers());
698 Score score, mobility[2] = { SCORE_ZERO, SCORE_ZERO };
699 Thread* thisThread = pos.this_thread();
701 // Initialize score by reading the incrementally updated scores included
702 // in the position object (material + piece square tables).
703 // Score is computed from the point of view of white.
704 score = pos.psq_score();
706 // Probe the material hash table
707 ei.mi = Material::probe(pos, thisThread->materialTable, thisThread->endgames);
708 score += ei.mi->material_value();
710 // If we have a specialized evaluation function for the current material
711 // configuration, call it and return.
712 if (ei.mi->specialized_eval_exists())
713 return ei.mi->evaluate(pos) + Eval::Tempo;
715 // Probe the pawn hash table
716 ei.pi = Pawns::probe(pos, thisThread->pawnsTable);
717 score += apply_weight(ei.pi->pawns_value(), Weights[PawnStructure]);
719 // Initialize attack and king safety bitboards
720 init_eval_info<WHITE>(pos, ei);
721 init_eval_info<BLACK>(pos, ei);
723 ei.attackedBy[WHITE][ALL_PIECES] |= ei.attackedBy[WHITE][KING];
724 ei.attackedBy[BLACK][ALL_PIECES] |= ei.attackedBy[BLACK][KING];
726 // Do not include in mobility squares protected by enemy pawns or occupied by our pawns or king
727 Bitboard mobilityArea[] = { ~(ei.attackedBy[BLACK][PAWN] | pos.pieces(WHITE, PAWN, KING)),
728 ~(ei.attackedBy[WHITE][PAWN] | pos.pieces(BLACK, PAWN, KING)) };
730 // Evaluate pieces and mobility
731 score += evaluate_pieces<KNIGHT, WHITE, Trace>(pos, ei, mobility, mobilityArea);
732 score += apply_weight(mobility[WHITE] - mobility[BLACK], Weights[Mobility]);
734 // Evaluate kings after all other pieces because we need complete attack
735 // information when computing the king safety evaluation.
736 score += evaluate_king<WHITE, Trace>(pos, ei)
737 - evaluate_king<BLACK, Trace>(pos, ei);
739 // Evaluate tactical threats, we need full attack information including king
740 score += evaluate_threats<WHITE, Trace>(pos, ei)
741 - evaluate_threats<BLACK, Trace>(pos, ei);
743 // Evaluate passed pawns, we need full attack information including king
744 score += evaluate_passed_pawns<WHITE, Trace>(pos, ei)
745 - evaluate_passed_pawns<BLACK, Trace>(pos, ei);
747 // If both sides have only pawns, score for potential unstoppable pawns
748 if (!pos.non_pawn_material(WHITE) && !pos.non_pawn_material(BLACK))
749 score += evaluate_unstoppable_pawns(WHITE, ei)
750 - evaluate_unstoppable_pawns(BLACK, ei);
752 // Evaluate space for both sides, only in middlegame
753 if (ei.mi->space_weight())
755 int s = evaluate_space<WHITE>(pos, ei) - evaluate_space<BLACK>(pos, ei);
756 score += apply_weight(s * ei.mi->space_weight(), Weights[Space]);
759 // Scale winning side if position is more drawish than it appears
760 Color strongSide = eg_value(score) > VALUE_DRAW ? WHITE : BLACK;
761 ScaleFactor sf = ei.mi->scale_factor(pos, strongSide);
763 // If we don't already have an unusual scale factor, check for certain
764 // types of endgames, and use a lower scale for those.
765 if ( ei.mi->game_phase() < PHASE_MIDGAME
766 && (sf == SCALE_FACTOR_NORMAL || sf == SCALE_FACTOR_ONEPAWN))
768 if (pos.opposite_bishops())
770 // Endgame with opposite-colored bishops and no other pieces (ignoring pawns)
771 // is almost a draw, in case of KBP vs KB is even more a draw.
772 if ( pos.non_pawn_material(WHITE) == BishopValueMg
773 && pos.non_pawn_material(BLACK) == BishopValueMg)
774 sf = more_than_one(pos.pieces(PAWN)) ? ScaleFactor(32) : ScaleFactor(8);
776 // Endgame with opposite-colored bishops, but also other pieces. Still
777 // a bit drawish, but not as drawish as with only the two bishops.
779 sf = ScaleFactor(50 * sf / SCALE_FACTOR_NORMAL);
781 // Endings where weaker side can place his king in front of the opponent's
782 // pawns are drawish.
783 else if ( abs(eg_value(score)) <= BishopValueEg
784 && ei.pi->pawn_span(strongSide) <= 1
785 && !pos.pawn_passed(~strongSide, pos.king_square(~strongSide)))
786 sf = ScaleFactor(ScalePawnSpan[ei.pi->pawn_span(strongSide)]);
789 // Interpolate between a middlegame and a (scaled by 'sf') endgame score
790 Value v = mg_value(score) * int(ei.mi->game_phase())
791 + eg_value(score) * int(PHASE_MIDGAME - ei.mi->game_phase()) * sf / SCALE_FACTOR_NORMAL;
793 v /= int(PHASE_MIDGAME);
795 // In case of tracing add all single evaluation contributions for both white and black
798 Tracing::write(Tracing::MATERIAL, pos.psq_score());
799 Tracing::write(Tracing::IMBALANCE, ei.mi->material_value());
800 Tracing::write(PAWN, ei.pi->pawns_value());
801 Tracing::write(Tracing::MOBILITY, apply_weight(mobility[WHITE], Weights[Mobility])
802 , apply_weight(mobility[BLACK], Weights[Mobility]));
803 Score w = ei.mi->space_weight() * evaluate_space<WHITE>(pos, ei);
804 Score b = ei.mi->space_weight() * evaluate_space<BLACK>(pos, ei);
805 Tracing::write(Tracing::SPACE, apply_weight(w, Weights[Space]), apply_weight(b, Weights[Space]));
806 Tracing::write(Tracing::TOTAL, score);
811 return (pos.side_to_move() == WHITE ? v : -v) + Eval::Tempo;
815 // Tracing function definitions
817 double Tracing::to_cp(Value v) { return double(v) / PawnValueEg; }
819 void Tracing::write(int idx, Color c, Score s) { scores[c][idx] = s; }
821 void Tracing::write(int idx, Score w, Score b) {
823 write(idx, WHITE, w);
824 write(idx, BLACK, b);
827 void Tracing::print(std::stringstream& ss, const char* name, int idx) {
829 Score wScore = scores[WHITE][idx];
830 Score bScore = scores[BLACK][idx];
833 case MATERIAL: case IMBALANCE: case PAWN: case TOTAL:
834 ss << std::setw(15) << name << " | --- --- | --- --- | "
835 << std::setw(5) << to_cp(mg_value(wScore - bScore)) << " "
836 << std::setw(5) << to_cp(eg_value(wScore - bScore)) << " \n";
839 ss << std::setw(15) << name << " | " << std::noshowpos
840 << std::setw(5) << to_cp(mg_value(wScore)) << " "
841 << std::setw(5) << to_cp(eg_value(wScore)) << " | "
842 << std::setw(5) << to_cp(mg_value(bScore)) << " "
843 << std::setw(5) << to_cp(eg_value(bScore)) << " | "
844 << std::setw(5) << to_cp(mg_value(wScore - bScore)) << " "
845 << std::setw(5) << to_cp(eg_value(wScore - bScore)) << " \n";
849 std::string Tracing::do_trace(const Position& pos) {
851 std::memset(scores, 0, sizeof(scores));
853 Value v = do_evaluate<true>(pos);
854 v = pos.side_to_move() == WHITE ? v : -v; // White's point of view
856 std::stringstream ss;
857 ss << std::showpoint << std::noshowpos << std::fixed << std::setprecision(2)
858 << " Eval term | White | Black | Total \n"
859 << " | MG EG | MG EG | MG EG \n"
860 << "----------------+-------------+-------------+-------------\n";
862 print(ss, "Material", MATERIAL);
863 print(ss, "Imbalance", IMBALANCE);
864 print(ss, "Pawns", PAWN);
865 print(ss, "Knights", KNIGHT);
866 print(ss, "Bishops", BISHOP);
867 print(ss, "Rooks", ROOK);
868 print(ss, "Queens", QUEEN);
869 print(ss, "Mobility", MOBILITY);
870 print(ss, "King safety", KING);
871 print(ss, "Threats", THREAT);
872 print(ss, "Passed pawns", PASSED);
873 print(ss, "Space", SPACE);
875 ss << "----------------+-------------+-------------+-------------\n";
876 print(ss, "Total", TOTAL);
878 ss << "\nTotal Evaluation: " << to_cp(v) << " (white side)\n";
888 /// evaluate() is the main evaluation function. It returns a static evaluation
889 /// of the position always from the point of view of the side to move.
891 Value evaluate(const Position& pos) {
892 return do_evaluate<false>(pos);
896 /// trace() is like evaluate(), but instead of returning a value, it returns
897 /// a string (suitable for outputting to stdout) that contains the detailed
898 /// descriptions and values of each evaluation term. It's mainly used for
900 std::string trace(const Position& pos) {
901 return Tracing::do_trace(pos);
905 /// init() computes evaluation weights.
909 const double MaxSlope = 30;
910 const double Peak = 1280;
912 for (int t = 0, i = 1; i < 100; ++i)
914 t = int(std::min(Peak, std::min(0.4 * i * i, t + MaxSlope)));
915 KingDanger[i] = apply_weight(make_score(t, 0), Weights[KingSafety]);