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 // apply_weight() weighs score 'v' by weight 'w' trying to prevent overflow
202 Score apply_weight(Score v, const Weight& w) {
203 return make_score(mg_value(v) * w.mg / 256, eg_value(v) * w.eg / 256);
207 // init_eval_info() initializes king bitboards for given color adding
208 // pawn attacks. To be done at the beginning of the evaluation.
211 void init_eval_info(const Position& pos, EvalInfo& ei) {
213 const Color Them = (Us == WHITE ? BLACK : WHITE);
214 const Square Down = (Us == WHITE ? DELTA_S : DELTA_N);
216 ei.pinnedPieces[Us] = pos.pinned_pieces(Us);
218 Bitboard b = ei.attackedBy[Them][KING] = pos.attacks_from<KING>(pos.king_square(Them));
219 ei.attackedBy[Us][ALL_PIECES] = ei.attackedBy[Us][PAWN] = ei.pi->pawn_attacks(Us);
221 // Init king safety tables only if we are going to use them
222 if (pos.non_pawn_material(Us) > QueenValueMg + PawnValueMg)
224 ei.kingRing[Them] = b | shift_bb<Down>(b);
225 b &= ei.attackedBy[Us][PAWN];
226 ei.kingAttackersCount[Us] = b ? popcount<Max15>(b) : 0;
227 ei.kingAdjacentZoneAttacksCount[Us] = ei.kingAttackersWeight[Us] = 0;
230 ei.kingRing[Them] = ei.kingAttackersCount[Us] = 0;
234 // evaluate_outpost() evaluates bishop and knight outpost squares
236 template<PieceType Pt, Color Us>
237 Score evaluate_outpost(const Position& pos, const EvalInfo& ei, Square s) {
239 const Color Them = (Us == WHITE ? BLACK : WHITE);
241 assert (Pt == BISHOP || Pt == KNIGHT);
243 // Initial bonus based on square
244 Value bonus = Outpost[Pt == BISHOP][relative_square(Us, s)];
246 // Increase bonus if supported by pawn, especially if the opponent has
247 // no minor piece which can trade with the outpost piece.
248 if (bonus && (ei.attackedBy[Us][PAWN] & s))
250 if ( !pos.pieces(Them, KNIGHT)
251 && !(squares_of_color(s) & pos.pieces(Them, BISHOP)))
252 bonus += bonus + bonus / 2;
257 return make_score(bonus * 2, bonus / 2);
261 // evaluate_pieces() assigns bonuses and penalties to the pieces of a given color
263 template<PieceType Pt, Color Us, bool Trace>
264 Score evaluate_pieces(const Position& pos, EvalInfo& ei, Score* mobility, Bitboard* mobilityArea) {
268 Score score = SCORE_ZERO;
270 const PieceType NextPt = (Us == WHITE ? Pt : PieceType(Pt + 1));
271 const Color Them = (Us == WHITE ? BLACK : WHITE);
272 const Square* pl = pos.list<Pt>(Us);
274 ei.attackedBy[Us][Pt] = 0;
276 while ((s = *pl++) != SQ_NONE)
278 // Find attacked squares, including x-ray attacks for bishops and rooks
279 b = Pt == BISHOP ? attacks_bb<BISHOP>(s, pos.pieces() ^ pos.pieces(Us, QUEEN))
280 : Pt == ROOK ? attacks_bb< ROOK>(s, pos.pieces() ^ pos.pieces(Us, ROOK, QUEEN))
281 : pos.attacks_from<Pt>(s);
283 if (ei.pinnedPieces[Us] & s)
284 b &= LineBB[pos.king_square(Us)][s];
286 ei.attackedBy[Us][ALL_PIECES] |= ei.attackedBy[Us][Pt] |= b;
288 if (b & ei.kingRing[Them])
290 ei.kingAttackersCount[Us]++;
291 ei.kingAttackersWeight[Us] += KingAttackWeights[Pt];
292 Bitboard bb = b & ei.attackedBy[Them][KING];
294 ei.kingAdjacentZoneAttacksCount[Us] += popcount<Max15>(bb);
298 b &= ~( ei.attackedBy[Them][KNIGHT]
299 | ei.attackedBy[Them][BISHOP]
300 | ei.attackedBy[Them][ROOK]);
302 int mob = Pt != QUEEN ? popcount<Max15>(b & mobilityArea[Us])
303 : popcount<Full >(b & mobilityArea[Us]);
305 mobility[Us] += MobilityBonus[Pt][mob];
307 // Decrease score if we are attacked by an enemy pawn. The remaining part
308 // of threat evaluation must be done later when we have full attack info.
309 if (ei.attackedBy[Them][PAWN] & s)
310 score -= ThreatenedByPawn[Pt];
312 if (Pt == BISHOP || Pt == KNIGHT)
314 // Penalty for bishop with same colored pawns
316 score -= BishopPawns * ei.pi->pawns_on_same_color_squares(Us, s);
318 // Bishop and knight outpost square
319 if (!(pos.pieces(Them, PAWN) & pawn_attack_span(Us, s)))
320 score += evaluate_outpost<Pt, Us>(pos, ei, s);
322 // Bishop or knight behind a pawn
323 if ( relative_rank(Us, s) < RANK_5
324 && (pos.pieces(PAWN) & (s + pawn_push(Us))))
325 score += MinorBehindPawn;
330 // Rook piece attacking enemy pawns on the same rank/file
331 if (relative_rank(Us, s) >= RANK_5)
333 Bitboard pawns = pos.pieces(Them, PAWN) & PseudoAttacks[ROOK][s];
335 score += popcount<Max15>(pawns) * RookOnPawn;
338 // Give a bonus for a rook on a open or semi-open file
339 if (ei.pi->semiopen_file(Us, file_of(s)))
340 score += ei.pi->semiopen_file(Them, file_of(s)) ? RookOpenFile : RookSemiOpenFile;
342 if (mob > 3 || ei.pi->semiopen_file(Us, file_of(s)))
345 Square ksq = pos.king_square(Us);
347 // Penalize rooks which are trapped by a king. Penalize more if the
348 // king has lost its castling capability.
349 if ( ((file_of(ksq) < FILE_E) == (file_of(s) < file_of(ksq)))
350 && (rank_of(ksq) == rank_of(s) || relative_rank(Us, ksq) == RANK_1)
351 && !ei.pi->semiopen_side(Us, file_of(ksq), file_of(s) < file_of(ksq)))
352 score -= (TrappedRook - make_score(mob * 22, 0)) * (1 + !pos.can_castle(Us));
355 // An important Chess960 pattern: A cornered bishop blocked by a friendly
356 // pawn diagonally in front of it is a very serious problem, especially
357 // when that pawn is also blocked.
360 && (s == relative_square(Us, SQ_A1) || s == relative_square(Us, SQ_H1)))
362 Square d = pawn_push(Us) + (file_of(s) == FILE_A ? DELTA_E : DELTA_W);
363 if (pos.piece_on(s + d) == make_piece(Us, PAWN))
364 score -= !pos.empty(s + d + pawn_push(Us)) ? TrappedBishopA1H1 * 4
365 : pos.piece_on(s + d + d) == make_piece(Us, PAWN) ? TrappedBishopA1H1 * 2
371 Tracing::write(Pt, Us, score);
373 return score - evaluate_pieces<NextPt, Them, Trace>(pos, ei, mobility, mobilityArea);
377 Score evaluate_pieces<KING, WHITE, false>(const Position&, EvalInfo&, Score*, Bitboard*) { return SCORE_ZERO; }
379 Score evaluate_pieces<KING, WHITE, true>(const Position&, EvalInfo&, Score*, Bitboard*) { return SCORE_ZERO; }
382 // evaluate_king() assigns bonuses and penalties to a king of a given color
384 template<Color Us, bool Trace>
385 Score evaluate_king(const Position& pos, const EvalInfo& ei) {
387 const Color Them = (Us == WHITE ? BLACK : WHITE);
389 Bitboard undefended, b, b1, b2, safe;
391 const Square ksq = pos.king_square(Us);
393 // King shelter and enemy pawns storm
394 Score score = ei.pi->king_safety<Us>(pos, ksq);
396 // Main king safety evaluation
397 if (ei.kingAttackersCount[Them])
399 // Find the attacked squares around the king which have no defenders
400 // apart from the king itself
401 undefended = ei.attackedBy[Them][ALL_PIECES]
402 & ei.attackedBy[Us][KING]
403 & ~( ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
404 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
405 | ei.attackedBy[Us][QUEEN]);
407 // Initialize the 'attackUnits' variable, which is used later on as an
408 // index to the KingDanger[] array. The initial value is based on the
409 // number and types of the enemy's attacking pieces, the number of
410 // attacked and undefended squares around our king and the quality of
411 // the pawn shelter (current 'score' value).
412 attackUnits = std::min(20, (ei.kingAttackersCount[Them] * ei.kingAttackersWeight[Them]) / 2)
413 + 3 * (ei.kingAdjacentZoneAttacksCount[Them] + popcount<Max15>(undefended))
414 + 2 * (ei.pinnedPieces[Us] != 0)
415 - mg_value(score) / 32
416 - !pos.count<QUEEN>(Them) * 15;
418 // Analyse the enemy's safe queen contact checks. Firstly, find the
419 // undefended squares around the king that are attacked by the enemy's
421 b = undefended & ei.attackedBy[Them][QUEEN] & ~pos.pieces(Them);
424 // ...and then remove squares not supported by another enemy piece
425 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
426 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][ROOK]);
429 attackUnits += QueenContactCheck * popcount<Max15>(b);
432 // Analyse the enemy's safe rook contact checks. Firstly, find the
433 // undefended squares around the king that are attacked by the enemy's
435 b = undefended & ei.attackedBy[Them][ROOK] & ~pos.pieces(Them);
437 // Consider only squares where the enemy's rook gives check
438 b &= PseudoAttacks[ROOK][ksq];
442 // ...and then remove squares not supported by another enemy piece
443 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
444 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][QUEEN]);
447 attackUnits += RookContactCheck * popcount<Max15>(b);
450 // Analyse the enemy's safe distance checks for sliders and knights
451 safe = ~(pos.pieces(Them) | ei.attackedBy[Us][ALL_PIECES]);
453 b1 = pos.attacks_from<ROOK>(ksq) & safe;
454 b2 = pos.attacks_from<BISHOP>(ksq) & safe;
456 // Enemy queen safe checks
457 b = (b1 | b2) & ei.attackedBy[Them][QUEEN];
459 attackUnits += QueenCheck * popcount<Max15>(b);
461 // Enemy rooks safe checks
462 b = b1 & ei.attackedBy[Them][ROOK];
464 attackUnits += RookCheck * popcount<Max15>(b);
466 // Enemy bishops safe checks
467 b = b2 & ei.attackedBy[Them][BISHOP];
469 attackUnits += BishopCheck * popcount<Max15>(b);
471 // Enemy knights safe checks
472 b = pos.attacks_from<KNIGHT>(ksq) & ei.attackedBy[Them][KNIGHT] & safe;
474 attackUnits += KnightCheck * popcount<Max15>(b);
476 // To index KingDanger[] attackUnits must be in [0, 99] range
477 attackUnits = std::min(99, std::max(0, attackUnits));
479 // Finally, extract the king danger score from the KingDanger[]
480 // array and subtract the score from evaluation.
481 score -= KingDanger[attackUnits];
485 Tracing::write(KING, Us, score);
491 // max_piece_type() is a helper function used by evaluate_threats() to get
492 // the value of the biggest PieceType of color C in 'target' bitboard.
495 inline PieceType max_piece_type(const Position& pos, const Bitboard target) {
497 assert(target & (pos.pieces(C) ^ pos.pieces(C, KING)));
499 for (PieceType pt = QUEEN; pt > PAWN; --pt)
500 if (target & pos.pieces(C, pt))
507 // evaluate_threats() assigns bonuses according to the type of attacking piece
508 // and the type of attacked one.
510 template<Color Us, bool Trace>
511 Score evaluate_threats(const Position& pos, const EvalInfo& ei) {
513 const Color Them = (Us == WHITE ? BLACK : WHITE);
515 enum { Minor, Major };
517 Bitboard b, weakEnemies, protectedEnemies;
518 Score score = SCORE_ZERO;
520 // Enemies defended by a pawn and under our attack by a minor piece
521 protectedEnemies = (pos.pieces(Them) ^ pos.pieces(Them, PAWN))
522 & ei.attackedBy[Them][PAWN]
523 & (ei.attackedBy[Us][KNIGHT] | ei.attackedBy[Us][BISHOP]);
525 if (protectedEnemies)
526 score += Threat[Minor][max_piece_type<Them>(pos, protectedEnemies)];
528 // Enemies not defended by a pawn and under our attack
529 weakEnemies = pos.pieces(Them)
530 & ~ei.attackedBy[Them][PAWN]
531 & ei.attackedBy[Us][ALL_PIECES];
533 // Add a bonus according if the attacking pieces are minor or major
536 b = weakEnemies & (ei.attackedBy[Us][KNIGHT] | ei.attackedBy[Us][BISHOP]);
538 score += Threat[Minor][max_piece_type<Them>(pos, b)];
540 b = weakEnemies & (ei.attackedBy[Us][ROOK] | ei.attackedBy[Us][QUEEN]);
542 score += Threat[Major][max_piece_type<Them>(pos, b)];
544 b = weakEnemies & ~ei.attackedBy[Them][ALL_PIECES];
546 score += more_than_one(b) ? Hanging * popcount<Max15>(b) : Hanging;
548 b = weakEnemies & ei.attackedBy[Us][KING];
550 score += more_than_one(b) ? KingOnMany : KingOnOne;
554 Tracing::write(Tracing::THREAT, Us, score);
560 // evaluate_passed_pawns() evaluates the passed pawns of the given color
562 template<Color Us, bool Trace>
563 Score evaluate_passed_pawns(const Position& pos, const EvalInfo& ei) {
565 const Color Them = (Us == WHITE ? BLACK : WHITE);
567 Bitboard b, squaresToQueen, defendedSquares, unsafeSquares;
568 Score score = SCORE_ZERO;
570 b = ei.pi->passed_pawns(Us);
574 Square s = pop_lsb(&b);
576 assert(pos.pawn_passed(Us, s));
578 int r = relative_rank(Us, s) - RANK_2;
579 int rr = r * (r - 1);
581 // Base bonus based on rank
582 Value mbonus = Value(17 * rr), ebonus = Value(7 * (rr + r + 1));
586 Square blockSq = s + pawn_push(Us);
588 // Adjust bonus based on the king's proximity
589 ebonus += square_distance(pos.king_square(Them), blockSq) * 5 * rr
590 - square_distance(pos.king_square(Us ), blockSq) * 2 * rr;
592 // If blockSq is not the queening square then consider also a second push
593 if (relative_rank(Us, blockSq) != RANK_8)
594 ebonus -= square_distance(pos.king_square(Us), blockSq + pawn_push(Us)) * rr;
596 // If the pawn is free to advance, then increase the bonus
597 if (pos.empty(blockSq))
599 // If there is a rook or queen attacking/defending the pawn from behind,
600 // consider all the squaresToQueen. Otherwise consider only the squares
601 // in the pawn's path attacked or occupied by the enemy.
602 defendedSquares = unsafeSquares = squaresToQueen = forward_bb(Us, s);
604 Bitboard bb = forward_bb(Them, s) & pos.pieces(ROOK, QUEEN) & pos.attacks_from<ROOK>(s);
606 if (!(pos.pieces(Us) & bb))
607 defendedSquares &= ei.attackedBy[Us][ALL_PIECES];
609 if (!(pos.pieces(Them) & bb))
610 unsafeSquares &= ei.attackedBy[Them][ALL_PIECES] | pos.pieces(Them);
612 // If there aren't any enemy attacks, assign a big bonus. Otherwise
613 // assign a smaller bonus if the block square isn't attacked.
614 int k = !unsafeSquares ? 15 : !(unsafeSquares & blockSq) ? 9 : 0;
616 // If the path to queen is fully defended, assign a big bonus.
617 // Otherwise assign a smaller bonus if the block square is defended.
618 if (defendedSquares == squaresToQueen)
621 else if (defendedSquares & blockSq)
624 mbonus += k * rr, ebonus += k * rr;
626 else if (pos.pieces(Us) & blockSq)
627 mbonus += rr * 3 + r * 2 + 3, ebonus += rr + r * 2;
630 if (pos.count<PAWN>(Us) < pos.count<PAWN>(Them))
631 ebonus += ebonus / 4;
633 score += make_score(mbonus, ebonus);
637 Tracing::write(Tracing::PASSED, Us, apply_weight(score, Weights[PassedPawns]));
639 // Add the scores to the middlegame and endgame eval
640 return apply_weight(score, Weights[PassedPawns]);
644 // evaluate_unstoppable_pawns() scores the most advanced passed pawn. In case
645 // both players have no pieces but pawns, this is somewhat related to the
646 // possibility that pawns are unstoppable.
648 Score evaluate_unstoppable_pawns(Color us, const EvalInfo& ei) {
650 Bitboard b = ei.pi->passed_pawns(us);
652 return b ? Unstoppable * int(relative_rank(us, frontmost_sq(us, b))) : SCORE_ZERO;
656 // evaluate_space() computes the space evaluation for a given side. The
657 // space evaluation is a simple bonus based on the number of safe squares
658 // available for minor pieces on the central four files on ranks 2--4. Safe
659 // squares one, two or three squares behind a friendly pawn are counted
660 // twice. Finally, the space bonus is scaled by a weight taken from the
661 // material hash table. The aim is to improve play on game opening.
663 int evaluate_space(const Position& pos, const EvalInfo& ei) {
665 const Color Them = (Us == WHITE ? BLACK : WHITE);
667 // Find the safe squares for our pieces inside the area defined by
668 // SpaceMask[]. A square is unsafe if it is attacked by an enemy
669 // pawn, or if it is undefended and attacked by an enemy piece.
670 Bitboard safe = SpaceMask[Us]
671 & ~pos.pieces(Us, PAWN)
672 & ~ei.attackedBy[Them][PAWN]
673 & (ei.attackedBy[Us][ALL_PIECES] | ~ei.attackedBy[Them][ALL_PIECES]);
675 // Find all squares which are at most three squares behind some friendly pawn
676 Bitboard behind = pos.pieces(Us, PAWN);
677 behind |= (Us == WHITE ? behind >> 8 : behind << 8);
678 behind |= (Us == WHITE ? behind >> 16 : behind << 16);
680 // Since SpaceMask[Us] is fully on our half of the board
681 assert(unsigned(safe >> (Us == WHITE ? 32 : 0)) == 0);
683 // Count safe + (behind & safe) with a single popcount
684 return popcount<Full>((Us == WHITE ? safe << 32 : safe >> 32) | (behind & safe));
688 // do_evaluate() is the evaluation entry point, called directly from evaluate()
691 Value do_evaluate(const Position& pos) {
693 assert(!pos.checkers());
696 Score score, mobility[2] = { SCORE_ZERO, SCORE_ZERO };
697 Thread* thisThread = pos.this_thread();
699 // Initialize score by reading the incrementally updated scores included
700 // in the position object (material + piece square tables).
701 // Score is computed from the point of view of white.
702 score = pos.psq_score();
704 // Probe the material hash table
705 ei.mi = Material::probe(pos, thisThread->materialTable, thisThread->endgames);
706 score += ei.mi->material_value();
708 // If we have a specialized evaluation function for the current material
709 // configuration, call it and return.
710 if (ei.mi->specialized_eval_exists())
711 return ei.mi->evaluate(pos) + Eval::Tempo;
713 // Probe the pawn hash table
714 ei.pi = Pawns::probe(pos, thisThread->pawnsTable);
715 score += apply_weight(ei.pi->pawns_value(), Weights[PawnStructure]);
717 // Initialize attack and king safety bitboards
718 init_eval_info<WHITE>(pos, ei);
719 init_eval_info<BLACK>(pos, ei);
721 ei.attackedBy[WHITE][ALL_PIECES] |= ei.attackedBy[WHITE][KING];
722 ei.attackedBy[BLACK][ALL_PIECES] |= ei.attackedBy[BLACK][KING];
724 // Do not include in mobility squares protected by enemy pawns or occupied by our pawns or king
725 Bitboard mobilityArea[] = { ~(ei.attackedBy[BLACK][PAWN] | pos.pieces(WHITE, PAWN, KING)),
726 ~(ei.attackedBy[WHITE][PAWN] | pos.pieces(BLACK, PAWN, KING)) };
728 // Evaluate pieces and mobility
729 score += evaluate_pieces<KNIGHT, WHITE, Trace>(pos, ei, mobility, mobilityArea);
730 score += apply_weight(mobility[WHITE] - mobility[BLACK], Weights[Mobility]);
732 // Evaluate kings after all other pieces because we need complete attack
733 // information when computing the king safety evaluation.
734 score += evaluate_king<WHITE, Trace>(pos, ei)
735 - evaluate_king<BLACK, Trace>(pos, ei);
737 // Evaluate tactical threats, we need full attack information including king
738 score += evaluate_threats<WHITE, Trace>(pos, ei)
739 - evaluate_threats<BLACK, Trace>(pos, ei);
741 // Evaluate passed pawns, we need full attack information including king
742 score += evaluate_passed_pawns<WHITE, Trace>(pos, ei)
743 - evaluate_passed_pawns<BLACK, Trace>(pos, ei);
745 // If both sides have only pawns, score for potential unstoppable pawns
746 if (!pos.non_pawn_material(WHITE) && !pos.non_pawn_material(BLACK))
747 score += evaluate_unstoppable_pawns(WHITE, ei)
748 - evaluate_unstoppable_pawns(BLACK, ei);
750 // Evaluate space for both sides, only in middlegame
751 if (ei.mi->space_weight())
753 int s = evaluate_space<WHITE>(pos, ei) - evaluate_space<BLACK>(pos, ei);
754 score += apply_weight(s * ei.mi->space_weight(), Weights[Space]);
757 // Scale winning side if position is more drawish than it appears
758 Color strongSide = eg_value(score) > VALUE_DRAW ? WHITE : BLACK;
759 ScaleFactor sf = ei.mi->scale_factor(pos, strongSide);
761 // If we don't already have an unusual scale factor, check for certain
762 // types of endgames, and use a lower scale for those.
763 if ( ei.mi->game_phase() < PHASE_MIDGAME
764 && (sf == SCALE_FACTOR_NORMAL || sf == SCALE_FACTOR_ONEPAWN))
766 if (pos.opposite_bishops())
768 // Endgame with opposite-colored bishops and no other pieces (ignoring pawns)
769 // is almost a draw, in case of KBP vs KB is even more a draw.
770 if ( pos.non_pawn_material(WHITE) == BishopValueMg
771 && pos.non_pawn_material(BLACK) == BishopValueMg)
772 sf = more_than_one(pos.pieces(PAWN)) ? ScaleFactor(32) : ScaleFactor(8);
774 // Endgame with opposite-colored bishops, but also other pieces. Still
775 // a bit drawish, but not as drawish as with only the two bishops.
777 sf = ScaleFactor(50 * sf / SCALE_FACTOR_NORMAL);
779 // Endings where weaker side can place his king in front of the opponent's
780 // pawns are drawish.
781 else if ( abs(eg_value(score)) <= BishopValueEg
782 && ei.pi->pawn_span(strongSide) <= 1
783 && !pos.pawn_passed(~strongSide, pos.king_square(~strongSide)))
784 sf = ei.pi->pawn_span(strongSide) ? ScaleFactor(56) : ScaleFactor(38);
787 // Interpolate between a middlegame and a (scaled by 'sf') endgame score
788 Value v = mg_value(score) * int(ei.mi->game_phase())
789 + eg_value(score) * int(PHASE_MIDGAME - ei.mi->game_phase()) * sf / SCALE_FACTOR_NORMAL;
791 v /= int(PHASE_MIDGAME);
793 // In case of tracing add all single evaluation contributions for both white and black
796 Tracing::write(Tracing::MATERIAL, pos.psq_score());
797 Tracing::write(Tracing::IMBALANCE, ei.mi->material_value());
798 Tracing::write(PAWN, ei.pi->pawns_value());
799 Tracing::write(Tracing::MOBILITY, apply_weight(mobility[WHITE], Weights[Mobility])
800 , apply_weight(mobility[BLACK], Weights[Mobility]));
801 Score w = ei.mi->space_weight() * evaluate_space<WHITE>(pos, ei);
802 Score b = ei.mi->space_weight() * evaluate_space<BLACK>(pos, ei);
803 Tracing::write(Tracing::SPACE, apply_weight(w, Weights[Space]), apply_weight(b, Weights[Space]));
804 Tracing::write(Tracing::TOTAL, score);
809 return (pos.side_to_move() == WHITE ? v : -v) + Eval::Tempo;
813 // Tracing function definitions
815 double Tracing::to_cp(Value v) { return double(v) / PawnValueEg; }
817 void Tracing::write(int idx, Color c, Score s) { scores[c][idx] = s; }
819 void Tracing::write(int idx, Score w, Score b) {
821 write(idx, WHITE, w);
822 write(idx, BLACK, b);
825 void Tracing::print(std::stringstream& ss, const char* name, int idx) {
827 Score wScore = scores[WHITE][idx];
828 Score bScore = scores[BLACK][idx];
831 case MATERIAL: case IMBALANCE: case PAWN: case TOTAL:
832 ss << std::setw(15) << name << " | --- --- | --- --- | "
833 << std::setw(5) << to_cp(mg_value(wScore - bScore)) << " "
834 << std::setw(5) << to_cp(eg_value(wScore - bScore)) << " \n";
837 ss << std::setw(15) << name << " | " << std::noshowpos
838 << std::setw(5) << to_cp(mg_value(wScore)) << " "
839 << std::setw(5) << to_cp(eg_value(wScore)) << " | "
840 << std::setw(5) << to_cp(mg_value(bScore)) << " "
841 << std::setw(5) << to_cp(eg_value(bScore)) << " | "
842 << std::setw(5) << to_cp(mg_value(wScore - bScore)) << " "
843 << std::setw(5) << to_cp(eg_value(wScore - bScore)) << " \n";
847 std::string Tracing::do_trace(const Position& pos) {
849 std::memset(scores, 0, sizeof(scores));
851 Value v = do_evaluate<true>(pos);
852 v = pos.side_to_move() == WHITE ? v : -v; // White's point of view
854 std::stringstream ss;
855 ss << std::showpoint << std::noshowpos << std::fixed << std::setprecision(2)
856 << " Eval term | White | Black | Total \n"
857 << " | MG EG | MG EG | MG EG \n"
858 << "----------------+-------------+-------------+-------------\n";
860 print(ss, "Material", MATERIAL);
861 print(ss, "Imbalance", IMBALANCE);
862 print(ss, "Pawns", PAWN);
863 print(ss, "Knights", KNIGHT);
864 print(ss, "Bishops", BISHOP);
865 print(ss, "Rooks", ROOK);
866 print(ss, "Queens", QUEEN);
867 print(ss, "Mobility", MOBILITY);
868 print(ss, "King safety", KING);
869 print(ss, "Threats", THREAT);
870 print(ss, "Passed pawns", PASSED);
871 print(ss, "Space", SPACE);
873 ss << "----------------+-------------+-------------+-------------\n";
874 print(ss, "Total", TOTAL);
876 ss << "\nTotal Evaluation: " << to_cp(v) << " (white side)\n";
886 /// evaluate() is the main evaluation function. It returns a static evaluation
887 /// of the position always from the point of view of the side to move.
889 Value evaluate(const Position& pos) {
890 return do_evaluate<false>(pos);
894 /// trace() is like evaluate(), but instead of returning a value, it returns
895 /// a string (suitable for outputting to stdout) that contains the detailed
896 /// descriptions and values of each evaluation term. It's mainly used for
898 std::string trace(const Position& pos) {
899 return Tracing::do_trace(pos);
903 /// init() computes evaluation weights.
907 const double MaxSlope = 30;
908 const double Peak = 1280;
910 for (int t = 0, i = 1; i < 100; ++i)
912 t = int(std::min(Peak, std::min(0.4 * i * i, t + MaxSlope)));
913 KingDanger[i] = apply_weight(make_score(t, 0), Weights[KingSafety]);