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/>.
30 #include "ucioption.h"
34 // Struct EvalInfo contains various information computed and collected
35 // by the evaluation functions.
38 // Pointers to material and pawn hash table entries
42 // attackedBy[color][piece type] is a bitboard representing all squares
43 // attacked by a given color and piece type, attackedBy[color][ALL_PIECES]
44 // contains all squares attacked by the given color.
45 Bitboard attackedBy[COLOR_NB][PIECE_TYPE_NB];
47 // kingRing[color] is the zone around the king which is considered
48 // by the king safety evaluation. This consists of the squares directly
49 // adjacent to the king, and the three (or two, for a king on an edge file)
50 // squares two ranks in front of the king. For instance, if black's king
51 // is on g8, kingRing[BLACK] is a bitboard containing the squares f8, h8,
52 // f7, g7, h7, f6, g6 and h6.
53 Bitboard kingRing[COLOR_NB];
55 // kingAttackersCount[color] is the number of pieces of the given color
56 // which attack a square in the kingRing of the enemy king.
57 int kingAttackersCount[COLOR_NB];
59 // kingAttackersWeight[color] is the sum of the "weight" of the pieces of the
60 // given color which attack a square in the kingRing of the enemy king. The
61 // weights of the individual piece types are given by the variables
62 // QueenAttackWeight, RookAttackWeight, BishopAttackWeight and
63 // KnightAttackWeight in evaluate.cpp
64 int kingAttackersWeight[COLOR_NB];
66 // kingAdjacentZoneAttacksCount[color] is the number of attacks to squares
67 // directly adjacent to the king of the given color. Pieces which attack
68 // more than one square are counted multiple times. For instance, if black's
69 // king is on g8 and there's a white knight on g5, this knight adds
70 // 2 to kingAdjacentZoneAttacksCount[BLACK].
71 int kingAdjacentZoneAttacksCount[COLOR_NB];
73 Bitboard pinnedPieces[COLOR_NB];
78 enum Terms { // First 8 entries are for PieceType
79 PST = 8, IMBALANCE, MOBILITY, THREAT, PASSED, SPACE, TOTAL, TERMS_NB
82 Score terms[COLOR_NB][TERMS_NB];
86 double to_cp(Value v);
87 void add_term(int idx, Score term_w, Score term_b = SCORE_ZERO);
88 void format_row(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( 7, 39), S(24, 49), S(24, 49), S(41,100), S(41,100) }, // Minor
144 { S(0, 0), S(15, 39), S(15, 45), S(15, 45), S(15, 45), S(24, 49) } // 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(56, 70), S(56, 70), S(76, 99), S(86, 118)
153 // Hanging contains a bonus for each enemy hanging piece
154 const Score Hanging = S(23, 20);
158 const Score RookOnPawn = make_score(10, 28);
159 const Score RookOpenFile = make_score(43, 21);
160 const Score RookSemiopenFile = make_score(19, 10);
161 const Score BishopPawns = make_score( 8, 12);
162 const Score MinorBehindPawn = make_score(16, 0);
163 const Score TrappedRook = make_score(90, 0);
164 const Score Unstoppable = make_score( 0, 20);
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 = make_score(50, 50);
171 // SpaceMask[Color] contains the area of the board which is considered
172 // by the space evaluation. In the middlegame, each side is given a bonus
173 // based on how many squares inside this area are safe and available for
174 // friendly minor pieces.
175 const Bitboard SpaceMask[] = {
176 (FileCBB | FileDBB | FileEBB | FileFBB) & (Rank2BB | Rank3BB | Rank4BB),
177 (FileCBB | FileDBB | FileEBB | FileFBB) & (Rank7BB | Rank6BB | Rank5BB)
180 // King danger constants and variables. The king danger scores are taken
181 // from KingDanger[]. Various little "meta-bonuses" measuring the strength
182 // of the enemy attack are added up into an integer, which is used as an
183 // index to KingDanger[].
185 // KingAttackWeights[PieceType] contains king attack weights by piece type
186 const int KingAttackWeights[] = { 0, 0, 2, 2, 3, 5 };
188 // Bonuses for enemy's safe checks
189 const int QueenContactCheck = 24;
190 const int RookContactCheck = 16;
191 const int QueenCheck = 12;
192 const int RookCheck = 8;
193 const int BishopCheck = 2;
194 const int KnightCheck = 3;
196 // KingDanger[attackUnits] contains the actual king danger weighted
197 // scores, indexed by a calculated integer number.
198 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.count<QUEEN>(Us) && 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_outposts() evaluates bishop and knight outpost squares
236 template<PieceType Pt, Color Us>
237 Score evaluate_outposts(const Position& pos, 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, bonus);
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 outposts squares
319 if (!(pos.pieces(Them, PAWN) & pawn_attack_span(Us, s)))
320 score += evaluate_outposts<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 * 8, 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::terms[Us][Pt] = 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;
417 // Analyse the enemy's safe queen contact checks. Firstly, find the
418 // undefended squares around the king that are attacked by the enemy's
420 b = undefended & ei.attackedBy[Them][QUEEN] & ~pos.pieces(Them);
423 // ...and then remove squares not supported by another enemy piece
424 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
425 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][ROOK]);
428 attackUnits += QueenContactCheck * popcount<Max15>(b);
431 // Analyse the enemy's safe rook contact checks. Firstly, find the
432 // undefended squares around the king that are attacked by the enemy's
434 b = undefended & ei.attackedBy[Them][ROOK] & ~pos.pieces(Them);
436 // Consider only squares where the enemy's rook gives check
437 b &= PseudoAttacks[ROOK][ksq];
441 // ...and then remove squares not supported by another enemy piece
442 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
443 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][QUEEN]);
446 attackUnits += RookContactCheck * popcount<Max15>(b);
449 // Analyse the enemy's safe distance checks for sliders and knights
450 safe = ~(pos.pieces(Them) | ei.attackedBy[Us][ALL_PIECES]);
452 b1 = pos.attacks_from<ROOK>(ksq) & safe;
453 b2 = pos.attacks_from<BISHOP>(ksq) & safe;
455 // Enemy queen safe checks
456 b = (b1 | b2) & ei.attackedBy[Them][QUEEN];
458 attackUnits += QueenCheck * popcount<Max15>(b);
460 // Enemy rooks safe checks
461 b = b1 & ei.attackedBy[Them][ROOK];
463 attackUnits += RookCheck * popcount<Max15>(b);
465 // Enemy bishops safe checks
466 b = b2 & ei.attackedBy[Them][BISHOP];
468 attackUnits += BishopCheck * popcount<Max15>(b);
470 // Enemy knights safe checks
471 b = pos.attacks_from<KNIGHT>(ksq) & ei.attackedBy[Them][KNIGHT] & safe;
473 attackUnits += KnightCheck * popcount<Max15>(b);
475 // To index KingDanger[] attackUnits must be in [0, 99] range
476 attackUnits = std::min(99, std::max(0, attackUnits));
478 // Finally, extract the king danger score from the KingDanger[]
479 // array and subtract the score from evaluation.
480 score -= KingDanger[attackUnits];
484 Tracing::terms[Us][KING] = score;
490 // evaluate_threats() assigns bonuses according to the type of attacking piece
491 // and the type of attacked one.
493 template<Color Us, bool Trace>
494 Score evaluate_threats(const Position& pos, const EvalInfo& ei) {
496 const Color Them = (Us == WHITE ? BLACK : WHITE);
498 Bitboard b, weakEnemies;
499 Score score = SCORE_ZERO;
501 // Enemies not defended by a pawn and under our attack
502 weakEnemies = pos.pieces(Them)
503 & ~ei.attackedBy[Them][PAWN]
504 & ei.attackedBy[Us][ALL_PIECES];
506 // Add a bonus according if the attacking pieces are minor or major
509 b = weakEnemies & (ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT] | ei.attackedBy[Us][BISHOP]);
511 score += Threat[0][type_of(pos.piece_on(lsb(b)))];
513 b = weakEnemies & (ei.attackedBy[Us][ROOK] | ei.attackedBy[Us][QUEEN]);
515 score += Threat[1][type_of(pos.piece_on(lsb(b)))];
517 b = weakEnemies & ~ei.attackedBy[Them][ALL_PIECES];
519 score += more_than_one(b) ? Hanging * popcount<Max15>(b) : Hanging;
523 Tracing::terms[Us][Tracing::THREAT] = score;
529 // evaluate_passed_pawns() evaluates the passed pawns of the given color
531 template<Color Us, bool Trace>
532 Score evaluate_passed_pawns(const Position& pos, const EvalInfo& ei) {
534 const Color Them = (Us == WHITE ? BLACK : WHITE);
536 Bitboard b, squaresToQueen, defendedSquares, unsafeSquares;
537 Score score = SCORE_ZERO;
539 b = ei.pi->passed_pawns(Us);
543 Square s = pop_lsb(&b);
545 assert(pos.pawn_passed(Us, s));
547 int r = relative_rank(Us, s) - RANK_2;
548 int rr = r * (r - 1);
550 // Base bonus based on rank
551 Value mbonus = Value(17 * rr), ebonus = Value(7 * (rr + r + 1));
555 Square blockSq = s + pawn_push(Us);
557 // Adjust bonus based on the king's proximity
558 ebonus += square_distance(pos.king_square(Them), blockSq) * 5 * rr
559 - square_distance(pos.king_square(Us ), blockSq) * 2 * rr;
561 // If blockSq is not the queening square then consider also a second push
562 if (relative_rank(Us, blockSq) != RANK_8)
563 ebonus -= square_distance(pos.king_square(Us), blockSq + pawn_push(Us)) * rr;
565 // If the pawn is free to advance, then increase the bonus
566 if (pos.empty(blockSq))
568 squaresToQueen = forward_bb(Us, s);
570 // If there is an enemy rook or queen attacking the pawn from behind,
571 // add all X-ray attacks by the rook or queen. Otherwise consider only
572 // the squares in the pawn's path attacked or occupied by the enemy.
573 if ( unlikely(forward_bb(Them, s) & pos.pieces(Them, ROOK, QUEEN))
574 && (forward_bb(Them, s) & pos.pieces(Them, ROOK, QUEEN) & pos.attacks_from<ROOK>(s)))
575 unsafeSquares = squaresToQueen;
577 unsafeSquares = squaresToQueen & (ei.attackedBy[Them][ALL_PIECES] | pos.pieces(Them));
579 if ( unlikely(forward_bb(Them, s) & pos.pieces(Us, ROOK, QUEEN))
580 && (forward_bb(Them, s) & pos.pieces(Us, ROOK, QUEEN) & pos.attacks_from<ROOK>(s)))
581 defendedSquares = squaresToQueen;
583 defendedSquares = squaresToQueen & ei.attackedBy[Us][ALL_PIECES];
585 // If there aren't any enemy attacks, assign a big bonus. Otherwise
586 // assign a smaller bonus if the block square isn't attacked.
587 int k = !unsafeSquares ? 15 : !(unsafeSquares & blockSq) ? 9 : 0;
589 // If the path to queen is fully defended, assign a big bonus.
590 // Otherwise assign a smaller bonus if the block square is defended.
591 if (defendedSquares == squaresToQueen)
594 else if (defendedSquares & blockSq)
597 mbonus += k * rr, ebonus += k * rr;
601 if (pos.count<PAWN>(Us) < pos.count<PAWN>(Them))
602 ebonus += ebonus / 4;
604 score += make_score(mbonus, ebonus);
608 Tracing::terms[Us][Tracing::PASSED] = apply_weight(score, Weights[PassedPawns]);
610 // Add the scores to the middlegame and endgame eval
611 return apply_weight(score, Weights[PassedPawns]);
615 // evaluate_unstoppable_pawns() scores the most advanced among the passed and
616 // candidate pawns. In case opponent has no pieces but pawns, this is somewhat
617 // related to the possibility that pawns are unstoppable.
619 Score evaluate_unstoppable_pawns(const Position& pos, Color us, const EvalInfo& ei) {
621 Bitboard b = ei.pi->passed_pawns(us) | ei.pi->candidate_pawns(us);
623 if (!b || pos.non_pawn_material(~us))
626 return Unstoppable * int(relative_rank(us, frontmost_sq(us, b)));
630 // evaluate_space() computes the space evaluation for a given side. The
631 // space evaluation is a simple bonus based on the number of safe squares
632 // available for minor pieces on the central four files on ranks 2--4. Safe
633 // squares one, two or three squares behind a friendly pawn are counted
634 // twice. Finally, the space bonus is scaled by a weight taken from the
635 // material hash table. The aim is to improve play on game opening.
637 int evaluate_space(const Position& pos, const EvalInfo& ei) {
639 const Color Them = (Us == WHITE ? BLACK : WHITE);
641 // Find the safe squares for our pieces inside the area defined by
642 // SpaceMask[]. A square is unsafe if it is attacked by an enemy
643 // pawn, or if it is undefended and attacked by an enemy piece.
644 Bitboard safe = SpaceMask[Us]
645 & ~pos.pieces(Us, PAWN)
646 & ~ei.attackedBy[Them][PAWN]
647 & (ei.attackedBy[Us][ALL_PIECES] | ~ei.attackedBy[Them][ALL_PIECES]);
649 // Find all squares which are at most three squares behind some friendly pawn
650 Bitboard behind = pos.pieces(Us, PAWN);
651 behind |= (Us == WHITE ? behind >> 8 : behind << 8);
652 behind |= (Us == WHITE ? behind >> 16 : behind << 16);
654 // Since SpaceMask[Us] is fully on our half of the board
655 assert(unsigned(safe >> (Us == WHITE ? 32 : 0)) == 0);
657 // Count safe + (behind & safe) with a single popcount
658 return popcount<Full>((Us == WHITE ? safe << 32 : safe >> 32) | (behind & safe));
662 // do_evaluate() is the evaluation entry point, called directly from evaluate()
665 Value do_evaluate(const Position& pos) {
667 assert(!pos.checkers());
670 Score score, mobility[2] = { SCORE_ZERO, SCORE_ZERO };
671 Thread* thisThread = pos.this_thread();
673 // Initialize score by reading the incrementally updated scores included
674 // in the position object (material + piece square tables).
675 // Score is computed from the point of view of white.
676 score = pos.psq_score();
678 // Probe the material hash table
679 ei.mi = Material::probe(pos, thisThread->materialTable, thisThread->endgames);
680 score += ei.mi->material_value();
682 // If we have a specialized evaluation function for the current material
683 // configuration, call it and return.
684 if (ei.mi->specialized_eval_exists())
685 return ei.mi->evaluate(pos);
687 // Probe the pawn hash table
688 ei.pi = Pawns::probe(pos, thisThread->pawnsTable);
689 score += apply_weight(ei.pi->pawns_value(), Weights[PawnStructure]);
691 // Initialize attack and king safety bitboards
692 init_eval_info<WHITE>(pos, ei);
693 init_eval_info<BLACK>(pos, ei);
695 ei.attackedBy[WHITE][ALL_PIECES] |= ei.attackedBy[WHITE][KING];
696 ei.attackedBy[BLACK][ALL_PIECES] |= ei.attackedBy[BLACK][KING];
698 // Do not include in mobility squares protected by enemy pawns or occupied by our pawns or king
699 Bitboard mobilityArea[] = { ~(ei.attackedBy[BLACK][PAWN] | pos.pieces(WHITE, PAWN, KING)),
700 ~(ei.attackedBy[WHITE][PAWN] | pos.pieces(BLACK, PAWN, KING)) };
702 // Evaluate pieces and mobility
703 score += evaluate_pieces<KNIGHT, WHITE, Trace>(pos, ei, mobility, mobilityArea);
704 score += apply_weight(mobility[WHITE] - mobility[BLACK], Weights[Mobility]);
706 // Evaluate kings after all other pieces because we need complete attack
707 // information when computing the king safety evaluation.
708 score += evaluate_king<WHITE, Trace>(pos, ei)
709 - evaluate_king<BLACK, Trace>(pos, ei);
711 // Evaluate tactical threats, we need full attack information including king
712 score += evaluate_threats<WHITE, Trace>(pos, ei)
713 - evaluate_threats<BLACK, Trace>(pos, ei);
715 // Evaluate passed pawns, we need full attack information including king
716 score += evaluate_passed_pawns<WHITE, Trace>(pos, ei)
717 - evaluate_passed_pawns<BLACK, Trace>(pos, ei);
719 // If one side has only a king, score for potential unstoppable pawns
720 if (!pos.non_pawn_material(WHITE) || !pos.non_pawn_material(BLACK))
721 score += evaluate_unstoppable_pawns(pos, WHITE, ei)
722 - evaluate_unstoppable_pawns(pos, BLACK, ei);
724 // Evaluate space for both sides, only in middlegame
725 if (ei.mi->space_weight())
727 int s = evaluate_space<WHITE>(pos, ei) - evaluate_space<BLACK>(pos, ei);
728 score += apply_weight(s * ei.mi->space_weight(), Weights[Space]);
731 // Scale winning side if position is more drawish than it appears
732 ScaleFactor sf = eg_value(score) > VALUE_DRAW ? ei.mi->scale_factor(pos, WHITE)
733 : ei.mi->scale_factor(pos, BLACK);
735 // If we don't already have an unusual scale factor, check for opposite
736 // colored bishop endgames, and use a lower scale for those.
737 if ( ei.mi->game_phase() < PHASE_MIDGAME
738 && pos.opposite_bishops()
739 && (sf == SCALE_FACTOR_NORMAL || sf == SCALE_FACTOR_ONEPAWN))
741 // Ignoring any pawns, do both sides only have a single bishop and no
743 if ( pos.non_pawn_material(WHITE) == BishopValueMg
744 && pos.non_pawn_material(BLACK) == BishopValueMg)
746 // Check for KBP vs KB with only a single pawn that is almost
747 // certainly a draw or at least two pawns.
748 bool one_pawn = (pos.count<PAWN>(WHITE) + pos.count<PAWN>(BLACK) == 1);
749 sf = one_pawn ? ScaleFactor(8) : ScaleFactor(32);
752 // Endgame with opposite-colored bishops, but also other pieces. Still
753 // a bit drawish, but not as drawish as with only the two bishops.
754 sf = ScaleFactor(50 * sf / SCALE_FACTOR_NORMAL);
757 // Interpolate between a middlegame and a (scaled by 'sf') endgame score
758 Value v = mg_value(score) * int(ei.mi->game_phase())
759 + eg_value(score) * int(PHASE_MIDGAME - ei.mi->game_phase()) * sf / SCALE_FACTOR_NORMAL;
761 v /= int(PHASE_MIDGAME);
763 // In case of tracing add all single evaluation contributions for both white and black
766 Tracing::add_term(Tracing::PST, pos.psq_score());
767 Tracing::add_term(Tracing::IMBALANCE, ei.mi->material_value());
768 Tracing::add_term(PAWN, ei.pi->pawns_value());
769 Tracing::add_term(Tracing::MOBILITY, apply_weight(mobility[WHITE], Weights[Mobility])
770 , apply_weight(mobility[BLACK], Weights[Mobility]));
771 Score w = ei.mi->space_weight() * evaluate_space<WHITE>(pos, ei);
772 Score b = ei.mi->space_weight() * evaluate_space<BLACK>(pos, ei);
773 Tracing::add_term(Tracing::SPACE, apply_weight(w, Weights[Space]), apply_weight(b, Weights[Space]));
774 Tracing::add_term(Tracing::TOTAL, score);
779 return pos.side_to_move() == WHITE ? v : -v;
783 // Tracing function definitions
785 double Tracing::to_cp(Value v) { return double(v) / PawnValueEg; }
787 void Tracing::add_term(int idx, Score wScore, Score bScore) {
789 terms[WHITE][idx] = wScore;
790 terms[BLACK][idx] = bScore;
793 void Tracing::format_row(std::stringstream& ss, const char* name, int idx) {
795 Score wScore = terms[WHITE][idx];
796 Score bScore = terms[BLACK][idx];
799 case PST: case IMBALANCE: case PAWN: case TOTAL:
800 ss << std::setw(20) << name << " | --- --- | --- --- | "
801 << std::setw(5) << to_cp(mg_value(wScore - bScore)) << " "
802 << std::setw(5) << to_cp(eg_value(wScore - bScore)) << " \n";
805 ss << std::setw(20) << name << " | " << std::noshowpos
806 << std::setw(5) << to_cp(mg_value(wScore)) << " "
807 << std::setw(5) << to_cp(eg_value(wScore)) << " | "
808 << std::setw(5) << to_cp(mg_value(bScore)) << " "
809 << std::setw(5) << to_cp(eg_value(bScore)) << " | "
810 << std::setw(5) << to_cp(mg_value(wScore - bScore)) << " "
811 << std::setw(5) << to_cp(eg_value(wScore - bScore)) << " \n";
815 std::string Tracing::do_trace(const Position& pos) {
817 std::memset(terms, 0, sizeof(terms));
819 Value v = do_evaluate<true>(pos);
820 v = pos.side_to_move() == WHITE ? v : -v; // White's point of view
822 std::stringstream ss;
823 ss << std::showpoint << std::noshowpos << std::fixed << std::setprecision(2)
824 << " Eval term | White | Black | Total \n"
825 << " | MG EG | MG EG | MG EG \n"
826 << "---------------------+-------------+-------------+-------------\n";
828 format_row(ss, "Material, PST", PST);
829 format_row(ss, "Material imbalance", IMBALANCE);
830 format_row(ss, "Pawns", PAWN);
831 format_row(ss, "Knights", KNIGHT);
832 format_row(ss, "Bishops", BISHOP);
833 format_row(ss, "Rooks", ROOK);
834 format_row(ss, "Queens", QUEEN);
835 format_row(ss, "Mobility", MOBILITY);
836 format_row(ss, "King safety", KING);
837 format_row(ss, "Threats", THREAT);
838 format_row(ss, "Passed pawns", PASSED);
839 format_row(ss, "Space", SPACE);
841 ss << "---------------------+-------------+-------------+-------------\n";
842 format_row(ss, "Total", TOTAL);
844 ss << "\nTotal Evaluation: " << to_cp(v) << " (white side)\n";
854 /// evaluate() is the main evaluation function. It returns a static evaluation
855 /// of the position always from the point of view of the side to move.
857 Value evaluate(const Position& pos) {
858 return do_evaluate<false>(pos) + Tempo;
862 /// trace() is like evaluate(), but instead of returning a value, it returns
863 /// a string (suitable for outputting to stdout) that contains the detailed
864 /// descriptions and values of each evaluation term. It's mainly used for
866 std::string trace(const Position& pos) {
867 return Tracing::do_trace(pos);
871 /// init() computes evaluation weights from the corresponding UCI parameters
872 /// and setup king tables.
876 const double MaxSlope = 30;
877 const double Peak = 1280;
879 for (int t = 0, i = 1; i < 100; ++i)
881 t = int(std::min(Peak, std::min(0.4 * i * i, t + MaxSlope)));
882 KingDanger[i] = apply_weight(make_score(t, 0), Weights[KingSafety]);