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 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}, {318, 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 RookOpenFile = S(43, 21);
159 const Score RookSemiOpenFile = 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);
173 // SpaceMask[Color] contains the area of the board which is considered
174 // by the space evaluation. In the middlegame, each side is given a bonus
175 // based on how many squares inside this area are safe and available for
176 // friendly minor pieces.
177 const Bitboard SpaceMask[] = {
178 (FileCBB | FileDBB | FileEBB | FileFBB) & (Rank2BB | Rank3BB | Rank4BB),
179 (FileCBB | FileDBB | FileEBB | FileFBB) & (Rank7BB | Rank6BB | Rank5BB)
182 // King danger constants and variables. The king danger scores are taken
183 // from KingDanger[]. Various little "meta-bonuses" measuring the strength
184 // of the enemy attack are added up into an integer, which is used as an
185 // index to KingDanger[].
187 // KingAttackWeights[PieceType] contains king attack weights by piece type
188 const int KingAttackWeights[] = { 0, 0, 2, 2, 3, 5 };
190 // Bonuses for enemy's safe checks
191 const int QueenContactCheck = 24;
192 const int RookContactCheck = 16;
193 const int QueenCheck = 12;
194 const int RookCheck = 8;
195 const int BishopCheck = 2;
196 const int KnightCheck = 3;
198 // KingDanger[attackUnits] contains the actual king danger weighted
199 // scores, indexed by a calculated integer number.
200 Score KingDanger[128];
202 // apply_weight() weighs score 'v' by weight 'w' trying to prevent overflow
203 Score apply_weight(Score v, const Weight& w) {
204 return make_score(mg_value(v) * w.mg / 256, eg_value(v) * w.eg / 256);
208 // init_eval_info() initializes king bitboards for given color adding
209 // pawn attacks. To be done at the beginning of the evaluation.
212 void init_eval_info(const Position& pos, EvalInfo& ei) {
214 const Color Them = (Us == WHITE ? BLACK : WHITE);
215 const Square Down = (Us == WHITE ? DELTA_S : DELTA_N);
217 ei.pinnedPieces[Us] = pos.pinned_pieces(Us);
219 Bitboard b = ei.attackedBy[Them][KING] = pos.attacks_from<KING>(pos.king_square(Them));
220 ei.attackedBy[Us][ALL_PIECES] = ei.attackedBy[Us][PAWN] = ei.pi->pawn_attacks(Us);
222 // Init king safety tables only if we are going to use them
223 if (pos.non_pawn_material(Us) >= QueenValueMg)
225 ei.kingRing[Them] = b | shift_bb<Down>(b);
226 b &= ei.attackedBy[Us][PAWN];
227 ei.kingAttackersCount[Us] = b ? popcount<Max15>(b) : 0;
228 ei.kingAdjacentZoneAttacksCount[Us] = ei.kingAttackersWeight[Us] = 0;
231 ei.kingRing[Them] = ei.kingAttackersCount[Us] = 0;
235 // evaluate_outpost() evaluates bishop and knight outpost squares
237 template<PieceType Pt, Color Us>
238 Score evaluate_outpost(const Position& pos, const EvalInfo& ei, Square s) {
240 const Color Them = (Us == WHITE ? BLACK : WHITE);
242 assert (Pt == BISHOP || Pt == KNIGHT);
244 // Initial bonus based on square
245 Value bonus = Outpost[Pt == BISHOP][relative_square(Us, s)];
247 // Increase bonus if supported by pawn, especially if the opponent has
248 // no minor piece which can trade with the outpost piece.
249 if (bonus && (ei.attackedBy[Us][PAWN] & s))
251 if ( !pos.pieces(Them, KNIGHT)
252 && !(squares_of_color(s) & pos.pieces(Them, BISHOP)))
253 bonus += bonus + bonus / 2;
258 return make_score(bonus * 2, bonus / 2);
262 // evaluate_pieces() assigns bonuses and penalties to the pieces of a given color
264 template<PieceType Pt, Color Us, bool Trace>
265 Score evaluate_pieces(const Position& pos, EvalInfo& ei, Score* mobility, Bitboard* mobilityArea) {
269 Score score = SCORE_ZERO;
271 const PieceType NextPt = (Us == WHITE ? Pt : PieceType(Pt + 1));
272 const Color Them = (Us == WHITE ? BLACK : WHITE);
273 const Square* pl = pos.list<Pt>(Us);
275 ei.attackedBy[Us][Pt] = 0;
277 while ((s = *pl++) != SQ_NONE)
279 // Find attacked squares, including x-ray attacks for bishops and rooks
280 b = Pt == BISHOP ? attacks_bb<BISHOP>(s, pos.pieces() ^ pos.pieces(Us, QUEEN))
281 : Pt == ROOK ? attacks_bb< ROOK>(s, pos.pieces() ^ pos.pieces(Us, ROOK, QUEEN))
282 : pos.attacks_from<Pt>(s);
284 if (ei.pinnedPieces[Us] & s)
285 b &= LineBB[pos.king_square(Us)][s];
287 ei.attackedBy[Us][ALL_PIECES] |= ei.attackedBy[Us][Pt] |= b;
289 if (b & ei.kingRing[Them])
291 ei.kingAttackersCount[Us]++;
292 ei.kingAttackersWeight[Us] += KingAttackWeights[Pt];
293 Bitboard bb = b & ei.attackedBy[Them][KING];
295 ei.kingAdjacentZoneAttacksCount[Us] += popcount<Max15>(bb);
299 b &= ~( ei.attackedBy[Them][KNIGHT]
300 | ei.attackedBy[Them][BISHOP]
301 | ei.attackedBy[Them][ROOK]);
303 int mob = Pt != QUEEN ? popcount<Max15>(b & mobilityArea[Us])
304 : popcount<Full >(b & mobilityArea[Us]);
306 mobility[Us] += MobilityBonus[Pt][mob];
308 // Decrease score if we are attacked by an enemy pawn. The remaining part
309 // of threat evaluation must be done later when we have full attack info.
310 if (ei.attackedBy[Them][PAWN] & s)
311 score -= ThreatenedByPawn[Pt];
313 if (Pt == BISHOP || Pt == KNIGHT)
315 // Penalty for bishop with same colored pawns
317 score -= BishopPawns * ei.pi->pawns_on_same_color_squares(Us, s);
319 // Bishop and knight outpost square
320 if (!(pos.pieces(Them, PAWN) & pawn_attack_span(Us, s)))
321 score += evaluate_outpost<Pt, Us>(pos, ei, s);
323 // Bishop or knight behind a pawn
324 if ( relative_rank(Us, s) < RANK_5
325 && (pos.pieces(PAWN) & (s + pawn_push(Us))))
326 score += MinorBehindPawn;
331 // Rook piece attacking enemy pawns on the same rank/file
332 if (relative_rank(Us, s) >= RANK_5)
334 Bitboard pawns = pos.pieces(Them, PAWN) & PseudoAttacks[ROOK][s];
336 score += popcount<Max15>(pawns) * RookOnPawn;
339 // Give a bonus for a rook on a open or semi-open file
340 if (ei.pi->semiopen_file(Us, file_of(s)))
341 score += ei.pi->semiopen_file(Them, file_of(s)) ? RookOpenFile : RookSemiOpenFile;
343 if (mob > 3 || ei.pi->semiopen_file(Us, file_of(s)))
346 Square ksq = pos.king_square(Us);
348 // Penalize rooks which are trapped by a king. Penalize more if the
349 // king has lost its castling capability.
350 if ( ((file_of(ksq) < FILE_E) == (file_of(s) < file_of(ksq)))
351 && (rank_of(ksq) == rank_of(s) || relative_rank(Us, ksq) == RANK_1)
352 && !ei.pi->semiopen_side(Us, file_of(ksq), file_of(s) < file_of(ksq)))
353 score -= (TrappedRook - make_score(mob * 22, 0)) * (1 + !pos.can_castle(Us));
356 // An important Chess960 pattern: A cornered bishop blocked by a friendly
357 // pawn diagonally in front of it is a very serious problem, especially
358 // when that pawn is also blocked.
361 && (s == relative_square(Us, SQ_A1) || s == relative_square(Us, SQ_H1)))
363 Square d = pawn_push(Us) + (file_of(s) == FILE_A ? DELTA_E : DELTA_W);
364 if (pos.piece_on(s + d) == make_piece(Us, PAWN))
365 score -= !pos.empty(s + d + pawn_push(Us)) ? TrappedBishopA1H1 * 4
366 : pos.piece_on(s + d + d) == make_piece(Us, PAWN) ? TrappedBishopA1H1 * 2
372 Tracing::write(Pt, Us, score);
374 return score - evaluate_pieces<NextPt, Them, Trace>(pos, ei, mobility, mobilityArea);
378 Score evaluate_pieces<KING, WHITE, false>(const Position&, EvalInfo&, Score*, Bitboard*) { return SCORE_ZERO; }
380 Score evaluate_pieces<KING, WHITE, true>(const Position&, EvalInfo&, Score*, Bitboard*) { return SCORE_ZERO; }
383 // evaluate_king() assigns bonuses and penalties to a king of a given color
385 template<Color Us, bool Trace>
386 Score evaluate_king(const Position& pos, const EvalInfo& ei) {
388 const Color Them = (Us == WHITE ? BLACK : WHITE);
390 Bitboard undefended, b, b1, b2, safe;
392 const Square ksq = pos.king_square(Us);
394 // King shelter and enemy pawns storm
395 Score score = ei.pi->king_safety<Us>(pos, ksq);
397 // Main king safety evaluation
398 if (ei.kingAttackersCount[Them])
400 // Find the attacked squares around the king which have no defenders
401 // apart from the king itself
402 undefended = ei.attackedBy[Them][ALL_PIECES]
403 & ei.attackedBy[Us][KING]
404 & ~( ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
405 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
406 | ei.attackedBy[Us][QUEEN]);
408 // Initialize the 'attackUnits' variable, which is used later on as an
409 // index to the KingDanger[] array. The initial value is based on the
410 // number and types of the enemy's attacking pieces, the number of
411 // attacked and undefended squares around our king and the quality of
412 // the pawn shelter (current 'score' value).
413 attackUnits = std::min(20, (ei.kingAttackersCount[Them] * ei.kingAttackersWeight[Them]) / 2)
414 + 3 * (ei.kingAdjacentZoneAttacksCount[Them] + popcount<Max15>(undefended))
415 + 2 * (ei.pinnedPieces[Us] != 0)
416 - mg_value(score) / 32
417 - !pos.count<QUEEN>(Them) * 15;
419 // Analyse the enemy's safe queen contact checks. Firstly, find the
420 // undefended squares around the king that are attacked by the enemy's
422 b = undefended & ei.attackedBy[Them][QUEEN] & ~pos.pieces(Them);
425 // ...and then remove squares not supported by another enemy piece
426 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
427 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][ROOK]);
430 attackUnits += QueenContactCheck * popcount<Max15>(b);
433 // Analyse the enemy's safe rook contact checks. Firstly, find the
434 // undefended squares around the king that are attacked by the enemy's
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 = ~(pos.pieces(Them) | ei.attackedBy[Us][ALL_PIECES]);
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 // To index KingDanger[] attackUnits must be in [0, 99] range
478 attackUnits = std::min(99, std::max(0, attackUnits));
480 // Finally, extract the king danger score from the KingDanger[]
481 // array and subtract the score from evaluation.
482 score -= KingDanger[attackUnits];
486 Tracing::write(KING, Us, score);
492 // evaluate_threats() assigns bonuses according to the type of attacking piece
493 // and the type of attacked one.
495 template<Color Us, bool Trace>
496 Score evaluate_threats(const Position& pos, const EvalInfo& ei) {
498 const Color Them = (Us == WHITE ? BLACK : WHITE);
500 enum { Defended, Weak };
501 enum { Minor, Major };
503 Bitboard b, weak, defended;
504 Score score = SCORE_ZERO;
506 // Non-pawn enemies defended by a pawn and under our attack
507 defended = (pos.pieces(Them) ^ pos.pieces(Them, PAWN))
508 & ei.attackedBy[Them][PAWN]
509 & (ei.attackedBy[Us][KNIGHT] | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]);
511 // Add a bonus according to the kind of attacking pieces
514 b = defended & (ei.attackedBy[Us][KNIGHT] | ei.attackedBy[Us][BISHOP]);
516 score += Threat[Defended][Minor][type_of(pos.piece_on(pop_lsb(&b)))];
518 b = defended & (ei.attackedBy[Us][ROOK]);
520 score += Threat[Defended][Major][type_of(pos.piece_on(pop_lsb(&b)))];
523 // Enemies not defended by a pawn and under our attack
524 weak = pos.pieces(Them)
525 & ~ei.attackedBy[Them][PAWN]
526 & ei.attackedBy[Us][ALL_PIECES];
528 // Add a bonus according to the kind of attacking pieces
531 b = weak & (ei.attackedBy[Us][KNIGHT] | ei.attackedBy[Us][BISHOP]);
533 score += Threat[Weak][Minor][type_of(pos.piece_on(pop_lsb(&b)))];
535 b = weak & (ei.attackedBy[Us][ROOK] | ei.attackedBy[Us][QUEEN]);
537 score += Threat[Weak][Major][type_of(pos.piece_on(pop_lsb(&b)))];
539 b = weak & ~ei.attackedBy[Them][ALL_PIECES];
541 score += more_than_one(b) ? Hanging * popcount<Max15>(b) : Hanging;
543 b = weak & ei.attackedBy[Us][KING];
545 score += more_than_one(b) ? KingOnMany : KingOnOne;
549 Tracing::write(Tracing::THREAT, Us, score);
555 // evaluate_passed_pawns() evaluates the passed pawns of the given color
557 template<Color Us, bool Trace>
558 Score evaluate_passed_pawns(const Position& pos, const EvalInfo& ei) {
560 const Color Them = (Us == WHITE ? BLACK : WHITE);
562 Bitboard b, squaresToQueen, defendedSquares, unsafeSquares;
563 Score score = SCORE_ZERO;
565 b = ei.pi->passed_pawns(Us);
569 Square s = pop_lsb(&b);
571 assert(pos.pawn_passed(Us, s));
573 int r = relative_rank(Us, s) - RANK_2;
574 int rr = r * (r - 1);
576 // Base bonus based on rank
577 Value mbonus = Value(17 * rr), ebonus = Value(7 * (rr + r + 1));
581 Square blockSq = s + pawn_push(Us);
583 // Adjust bonus based on the king's proximity
584 ebonus += distance(pos.king_square(Them), blockSq) * 5 * rr
585 - distance(pos.king_square(Us ), blockSq) * 2 * rr;
587 // If blockSq is not the queening square then consider also a second push
588 if (relative_rank(Us, blockSq) != RANK_8)
589 ebonus -= distance(pos.king_square(Us), blockSq + pawn_push(Us)) * rr;
591 // If the pawn is free to advance, then increase the bonus
592 if (pos.empty(blockSq))
594 // If there is a rook or queen attacking/defending the pawn from behind,
595 // consider all the squaresToQueen. Otherwise consider only the squares
596 // in the pawn's path attacked or occupied by the enemy.
597 defendedSquares = unsafeSquares = squaresToQueen = forward_bb(Us, s);
599 Bitboard bb = forward_bb(Them, s) & pos.pieces(ROOK, QUEEN) & pos.attacks_from<ROOK>(s);
601 if (!(pos.pieces(Us) & bb))
602 defendedSquares &= ei.attackedBy[Us][ALL_PIECES];
604 if (!(pos.pieces(Them) & bb))
605 unsafeSquares &= ei.attackedBy[Them][ALL_PIECES] | pos.pieces(Them);
607 // If there aren't any enemy attacks, assign a big bonus. Otherwise
608 // assign a smaller bonus if the block square isn't attacked.
609 int k = !unsafeSquares ? 15 : !(unsafeSquares & blockSq) ? 9 : 0;
611 // If the path to queen is fully defended, assign a big bonus.
612 // Otherwise assign a smaller bonus if the block square is defended.
613 if (defendedSquares == squaresToQueen)
616 else if (defendedSquares & blockSq)
619 mbonus += k * rr, ebonus += k * rr;
621 else if (pos.pieces(Us) & blockSq)
622 mbonus += rr * 3 + r * 2 + 3, ebonus += rr + r * 2;
625 if (pos.count<PAWN>(Us) < pos.count<PAWN>(Them))
626 ebonus += ebonus / 4;
628 score += make_score(mbonus, ebonus);
632 Tracing::write(Tracing::PASSED, Us, apply_weight(score, Weights[PassedPawns]));
634 // Add the scores to the middlegame and endgame eval
635 return apply_weight(score, Weights[PassedPawns]);
639 // evaluate_unstoppable_pawns() scores the most advanced passed pawn. In case
640 // both players have no pieces but pawns, this is somewhat related to the
641 // possibility that pawns are unstoppable.
643 Score evaluate_unstoppable_pawns(Color us, const EvalInfo& ei) {
645 Bitboard b = ei.pi->passed_pawns(us);
647 return b ? Unstoppable * int(relative_rank(us, frontmost_sq(us, b))) : SCORE_ZERO;
651 // evaluate_space() computes the space evaluation for a given side. The
652 // space evaluation is a simple bonus based on the number of safe squares
653 // available for minor pieces on the central four files on ranks 2--4. Safe
654 // squares one, two or three squares behind a friendly pawn are counted
655 // twice. Finally, the space bonus is scaled by a weight taken from the
656 // material hash table. The aim is to improve play on game opening.
658 int evaluate_space(const Position& pos, const EvalInfo& ei) {
660 const Color Them = (Us == WHITE ? BLACK : WHITE);
662 // Find the safe squares for our pieces inside the area defined by
663 // SpaceMask[]. A square is unsafe if it is attacked by an enemy
664 // pawn, or if it is undefended and attacked by an enemy piece.
665 Bitboard safe = SpaceMask[Us]
666 & ~pos.pieces(Us, PAWN)
667 & ~ei.attackedBy[Them][PAWN]
668 & (ei.attackedBy[Us][ALL_PIECES] | ~ei.attackedBy[Them][ALL_PIECES]);
670 // Find all squares which are at most three squares behind some friendly pawn
671 Bitboard behind = pos.pieces(Us, PAWN);
672 behind |= (Us == WHITE ? behind >> 8 : behind << 8);
673 behind |= (Us == WHITE ? behind >> 16 : behind << 16);
675 // Since SpaceMask[Us] is fully on our half of the board
676 assert(unsigned(safe >> (Us == WHITE ? 32 : 0)) == 0);
678 // Count safe + (behind & safe) with a single popcount
679 return popcount<Full>((Us == WHITE ? safe << 32 : safe >> 32) | (behind & safe));
683 // do_evaluate() is the evaluation entry point, called directly from evaluate()
686 Value do_evaluate(const Position& pos) {
688 assert(!pos.checkers());
691 Score score, mobility[2] = { SCORE_ZERO, SCORE_ZERO };
692 Thread* thisThread = pos.this_thread();
694 // Initialize score by reading the incrementally updated scores included
695 // in the position object (material + piece square tables).
696 // Score is computed from the point of view of white.
697 score = pos.psq_score();
699 // Probe the material hash table
700 ei.mi = Material::probe(pos, thisThread->materialTable, thisThread->endgames);
701 score += ei.mi->material_value();
703 // If we have a specialized evaluation function for the current material
704 // configuration, call it and return.
705 if (ei.mi->specialized_eval_exists())
706 return ei.mi->evaluate(pos) + Eval::Tempo;
708 // Probe the pawn hash table
709 ei.pi = Pawns::probe(pos, thisThread->pawnsTable);
710 score += apply_weight(ei.pi->pawns_value(), Weights[PawnStructure]);
712 // Initialize attack and king safety bitboards
713 init_eval_info<WHITE>(pos, ei);
714 init_eval_info<BLACK>(pos, ei);
716 ei.attackedBy[WHITE][ALL_PIECES] |= ei.attackedBy[WHITE][KING];
717 ei.attackedBy[BLACK][ALL_PIECES] |= ei.attackedBy[BLACK][KING];
719 // Do not include in mobility squares protected by enemy pawns or occupied by our pawns or king
720 Bitboard mobilityArea[] = { ~(ei.attackedBy[BLACK][PAWN] | pos.pieces(WHITE, PAWN, KING)),
721 ~(ei.attackedBy[WHITE][PAWN] | pos.pieces(BLACK, PAWN, KING)) };
723 // Evaluate pieces and mobility
724 score += evaluate_pieces<KNIGHT, WHITE, Trace>(pos, ei, mobility, mobilityArea);
725 score += apply_weight(mobility[WHITE] - mobility[BLACK], Weights[Mobility]);
727 // Evaluate kings after all other pieces because we need complete attack
728 // information when computing the king safety evaluation.
729 score += evaluate_king<WHITE, Trace>(pos, ei)
730 - evaluate_king<BLACK, Trace>(pos, ei);
732 // Evaluate tactical threats, we need full attack information including king
733 score += evaluate_threats<WHITE, Trace>(pos, ei)
734 - evaluate_threats<BLACK, Trace>(pos, ei);
736 // Evaluate passed pawns, we need full attack information including king
737 score += evaluate_passed_pawns<WHITE, Trace>(pos, ei)
738 - evaluate_passed_pawns<BLACK, Trace>(pos, ei);
740 // If both sides have only pawns, score for potential unstoppable pawns
741 if (!pos.non_pawn_material(WHITE) && !pos.non_pawn_material(BLACK))
742 score += evaluate_unstoppable_pawns(WHITE, ei)
743 - evaluate_unstoppable_pawns(BLACK, ei);
745 // Evaluate space for both sides, only in middlegame
746 if (ei.mi->space_weight())
748 int s = evaluate_space<WHITE>(pos, ei) - evaluate_space<BLACK>(pos, ei);
749 score += apply_weight(s * ei.mi->space_weight(), Weights[Space]);
752 // Scale winning side if position is more drawish than it appears
753 Color strongSide = eg_value(score) > VALUE_DRAW ? WHITE : BLACK;
754 ScaleFactor sf = ei.mi->scale_factor(pos, strongSide);
756 // If we don't already have an unusual scale factor, check for certain
757 // types of endgames, and use a lower scale for those.
758 if ( ei.mi->game_phase() < PHASE_MIDGAME
759 && (sf == SCALE_FACTOR_NORMAL || sf == SCALE_FACTOR_ONEPAWN))
761 if (pos.opposite_bishops())
763 // Endgame with opposite-colored bishops and no other pieces (ignoring pawns)
764 // is almost a draw, in case of KBP vs KB is even more a draw.
765 if ( pos.non_pawn_material(WHITE) == BishopValueMg
766 && pos.non_pawn_material(BLACK) == BishopValueMg)
767 sf = more_than_one(pos.pieces(PAWN)) ? ScaleFactor(32) : ScaleFactor(8);
769 // Endgame with opposite-colored bishops, but also other pieces. Still
770 // a bit drawish, but not as drawish as with only the two bishops.
772 sf = ScaleFactor(50 * sf / SCALE_FACTOR_NORMAL);
774 // Endings where weaker side can place his king in front of the opponent's
775 // pawns are drawish.
776 else if ( abs(eg_value(score)) <= BishopValueEg
777 && ei.pi->pawn_span(strongSide) <= 1
778 && !pos.pawn_passed(~strongSide, pos.king_square(~strongSide)))
779 sf = ei.pi->pawn_span(strongSide) ? ScaleFactor(56) : ScaleFactor(38);
782 // Interpolate between a middlegame and a (scaled by 'sf') endgame score
783 Value v = mg_value(score) * int(ei.mi->game_phase())
784 + eg_value(score) * int(PHASE_MIDGAME - ei.mi->game_phase()) * sf / SCALE_FACTOR_NORMAL;
786 v /= int(PHASE_MIDGAME);
788 // In case of tracing add all single evaluation contributions for both white and black
791 Tracing::write(Tracing::MATERIAL, pos.psq_score());
792 Tracing::write(Tracing::IMBALANCE, ei.mi->material_value());
793 Tracing::write(PAWN, ei.pi->pawns_value());
794 Tracing::write(Tracing::MOBILITY, apply_weight(mobility[WHITE], Weights[Mobility])
795 , apply_weight(mobility[BLACK], Weights[Mobility]));
796 Score w = ei.mi->space_weight() * evaluate_space<WHITE>(pos, ei);
797 Score b = ei.mi->space_weight() * evaluate_space<BLACK>(pos, ei);
798 Tracing::write(Tracing::SPACE, apply_weight(w, Weights[Space]), apply_weight(b, Weights[Space]));
799 Tracing::write(Tracing::TOTAL, score);
804 return (pos.side_to_move() == WHITE ? v : -v) + Eval::Tempo;
808 // Tracing function definitions
810 double Tracing::to_cp(Value v) { return double(v) / PawnValueEg; }
812 void Tracing::write(int idx, Color c, Score s) { scores[c][idx] = s; }
814 void Tracing::write(int idx, Score w, Score b) {
816 write(idx, WHITE, w);
817 write(idx, BLACK, b);
820 void Tracing::print(std::stringstream& ss, const char* name, int idx) {
822 Score wScore = scores[WHITE][idx];
823 Score bScore = scores[BLACK][idx];
826 case MATERIAL: case IMBALANCE: case PAWN: case TOTAL:
827 ss << std::setw(15) << name << " | --- --- | --- --- | "
828 << std::setw(5) << to_cp(mg_value(wScore - bScore)) << " "
829 << std::setw(5) << to_cp(eg_value(wScore - bScore)) << " \n";
832 ss << std::setw(15) << name << " | " << std::noshowpos
833 << std::setw(5) << to_cp(mg_value(wScore)) << " "
834 << std::setw(5) << to_cp(eg_value(wScore)) << " | "
835 << std::setw(5) << to_cp(mg_value(bScore)) << " "
836 << std::setw(5) << to_cp(eg_value(bScore)) << " | "
837 << std::setw(5) << to_cp(mg_value(wScore - bScore)) << " "
838 << std::setw(5) << to_cp(eg_value(wScore - bScore)) << " \n";
842 std::string Tracing::do_trace(const Position& pos) {
844 std::memset(scores, 0, sizeof(scores));
846 Value v = do_evaluate<true>(pos);
847 v = pos.side_to_move() == WHITE ? v : -v; // White's point of view
849 std::stringstream ss;
850 ss << std::showpoint << std::noshowpos << std::fixed << std::setprecision(2)
851 << " Eval term | White | Black | Total \n"
852 << " | MG EG | MG EG | MG EG \n"
853 << "----------------+-------------+-------------+-------------\n";
855 print(ss, "Material", MATERIAL);
856 print(ss, "Imbalance", IMBALANCE);
857 print(ss, "Pawns", PAWN);
858 print(ss, "Knights", KNIGHT);
859 print(ss, "Bishops", BISHOP);
860 print(ss, "Rooks", ROOK);
861 print(ss, "Queens", QUEEN);
862 print(ss, "Mobility", MOBILITY);
863 print(ss, "King safety", KING);
864 print(ss, "Threats", THREAT);
865 print(ss, "Passed pawns", PASSED);
866 print(ss, "Space", SPACE);
868 ss << "----------------+-------------+-------------+-------------\n";
869 print(ss, "Total", TOTAL);
871 ss << "\nTotal Evaluation: " << to_cp(v) << " (white side)\n";
881 /// evaluate() is the main evaluation function. It returns a static evaluation
882 /// of the position always from the point of view of the side to move.
884 Value evaluate(const Position& pos) {
885 return do_evaluate<false>(pos);
889 /// trace() is like evaluate(), but instead of returning a value, it returns
890 /// a string (suitable for outputting to stdout) that contains the detailed
891 /// descriptions and values of each evaluation term. It's mainly used for
893 std::string trace(const Position& pos) {
894 return Tracing::do_trace(pos);
898 /// init() computes evaluation weights.
902 const double MaxSlope = 30;
903 const double Peak = 1280;
905 for (int t = 0, i = 1; i < 100; ++i)
907 t = int(std::min(Peak, std::min(0.4 * i * i, t + MaxSlope)));
908 KingDanger[i] = apply_weight(make_score(t, 0), Weights[KingSafety]);