2 Stockfish, a UCI chess playing engine derived from Glaurung 2.1
3 Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
4 Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad
6 Stockfish is free software: you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation, either version 3 of the License, or
9 (at your option) any later version.
11 Stockfish is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
16 You should have received a copy of the GNU General Public License
17 along with this program. If not, see <http://www.gnu.org/licenses/>.
22 #include <cstring> // For std::memset
35 enum Term { // First 8 entries are for PieceType
36 MATERIAL = 8, IMBALANCE, MOBILITY, THREAT, PASSED, SPACE, TOTAL, TERM_NB
39 Score scores[COLOR_NB][TERM_NB];
41 std::ostream& operator<<(std::ostream& os, Term idx);
43 double to_cp(Value v);
44 void write(int idx, Color c, Score s);
45 void write(int idx, Score w, Score b = SCORE_ZERO);
46 std::string do_trace(const Position& pos);
50 // Struct EvalInfo contains various information computed and collected
51 // by the evaluation functions.
54 // Pointers to material and pawn hash table entries
58 // attackedBy[color][piece type] is a bitboard representing all squares
59 // attacked by a given color and piece type, attackedBy[color][ALL_PIECES]
60 // contains all squares attacked by the given color.
61 Bitboard attackedBy[COLOR_NB][PIECE_TYPE_NB];
63 // kingRing[color] is the zone around the king which is considered
64 // by the king safety evaluation. This consists of the squares directly
65 // adjacent to the king, and the three (or two, for a king on an edge file)
66 // squares two ranks in front of the king. For instance, if black's king
67 // is on g8, kingRing[BLACK] is a bitboard containing the squares f8, h8,
68 // f7, g7, h7, f6, g6 and h6.
69 Bitboard kingRing[COLOR_NB];
71 // kingAttackersCount[color] is the number of pieces of the given color
72 // which attack a square in the kingRing of the enemy king.
73 int kingAttackersCount[COLOR_NB];
75 // kingAttackersWeight[color] is the sum of the "weight" of the pieces of the
76 // given color which attack a square in the kingRing of the enemy king. The
77 // weights of the individual piece types are given by the elements in the
78 // KingAttackWeights array.
79 int kingAttackersWeight[COLOR_NB];
81 // kingAdjacentZoneAttacksCount[color] is the number of attacks by the given
82 // color to squares directly adjacent to the enemy king. Pieces which attack
83 // more than one square are counted multiple times. For instance, if there is
84 // a white knight on g5 and black's king is on g8, this white knight adds 2
85 // to kingAdjacentZoneAttacksCount[WHITE].
86 int kingAdjacentZoneAttacksCount[COLOR_NB];
88 Bitboard pinnedPieces[COLOR_NB];
92 // Evaluation weights, indexed by the corresponding evaluation term
93 enum { Mobility, PawnStructure, PassedPawns, Space, KingSafety };
95 const struct Weight { int mg, eg; } Weights[] = {
96 {289, 344}, {233, 201}, {221, 273}, {46, 0}, {322, 0}
99 Score operator*(Score s, const Weight& w) {
100 return make_score(mg_value(s) * w.mg / 256, eg_value(s) * w.eg / 256);
104 #define V(v) Value(v)
105 #define S(mg, eg) make_score(mg, eg)
107 // MobilityBonus[PieceType][attacked] contains bonuses for middle and end
108 // game, indexed by piece type and number of attacked squares not occupied by
110 const Score MobilityBonus[][32] = {
112 { S(-68,-49), S(-46,-33), S(-3,-12), S( 5, -4), S( 9, 11), S(15, 16), // Knights
113 S( 23, 27), S( 33, 28), S(37, 29) },
114 { S(-49,-44), S(-23,-16), S(16, 1), S(29, 16), S(40, 25), S(51, 34), // Bishops
115 S( 55, 43), S( 61, 49), S(64, 51), S(68, 52), S(73, 55), S(75, 60),
116 S( 80, 65), S( 86, 66) },
117 { S(-50,-57), S(-28,-22), S(-11, 7), S(-1, 29), S( 0, 39), S( 1, 46), // Rooks
118 S( 10, 66), S( 16, 79), S(22, 86), S(23,103), S(30,109), S(33,111),
119 S( 37,115), S( 38,119), S(48,124) },
120 { S(-43,-30), S(-27,-15), S( 1, -5), S( 2, -3), S(14, 10), S(18, 24), // Queens
121 S( 20, 27), S( 33, 37), S(33, 38), S(34, 43), S(40, 46), S(43, 56),
122 S( 46, 61), S( 52, 63), S(52, 63), S(57, 65), S(60, 70), S(61, 74),
123 S( 67, 80), S( 76, 82), S(77, 88), S(82, 94), S(86, 95), S(90, 96),
124 S( 94, 99), S( 96,100), S(99,111), S(99,112) }
127 // Outpost[knight/bishop][supported by pawn]
128 const Score Outpost[][2] = {
129 { S(28, 7), S(42,11) }, // Knights
130 { S(12, 3), S(18, 5) } // Bishops
133 // Threat[defended/weak][minor/major attacking][attacked PieceType] contains
134 // bonuses according to which piece type attacks which one.
135 const Score Threat[][2][PIECE_TYPE_NB] = {
136 { { S(0, 0), S( 0, 0), S(19, 37), S(24, 37), S(44, 97), S(35,106) }, // Defended Minor
137 { S(0, 0), S( 0, 0), S( 9, 14), S( 9, 14), S( 7, 14), S(24, 48) } }, // Defended Major
138 { { S(0, 0), S( 0,32), S(33, 41), S(31, 50), S(41,100), S(35,104) }, // Weak Minor
139 { S(0, 0), S( 0,27), S(26, 57), S(26, 57), S(0 , 43), S(23, 51) } } // Weak Major
142 // ThreatenedByPawn[PieceType] contains a penalty according to which piece
143 // type is attacked by an enemy pawn.
144 const Score ThreatenedByPawn[PIECE_TYPE_NB] = {
145 S(0, 0), S(0, 0), S(107, 138), S(84, 122), S(114, 203), S(121, 217)
148 const Score ThreatenedByHangingPawn = S(40, 60);
150 // Assorted bonuses and penalties used by evaluation
151 const Score KingOnOne = S( 2, 58);
152 const Score KingOnMany = S( 6,125);
153 const Score RookOnPawn = S( 7, 27);
154 const Score RookOnOpenFile = S(43, 21);
155 const Score RookOnSemiOpenFile = S(19, 10);
156 const Score BishopPawns = S( 8, 12);
157 const Score MinorBehindPawn = S(16, 0);
158 const Score TrappedRook = S(92, 0);
159 const Score Unstoppable = S( 0, 20);
160 const Score Hanging = S(31, 26);
161 const Score PawnAttackThreat = S(20, 20);
162 const Score PawnSafePush = S( 5, 5);
164 // Penalty for a bishop on a1/h1 (a8/h8 for black) which is trapped by
165 // a friendly pawn on b2/g2 (b7/g7 for black). This can obviously only
166 // happen in Chess960 games.
167 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[COLOR_NB] = {
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 looked-up
182 // in 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[].
185 Score KingDanger[512];
187 // KingAttackWeights[PieceType] contains king attack weights by piece type
188 const int KingAttackWeights[PIECE_TYPE_NB] = { 0, 0, 7, 5, 4, 1 };
190 // Penalties for enemy's safe checks
191 const int QueenContactCheck = 89;
192 const int RookContactCheck = 71;
193 const int QueenCheck = 50;
194 const int RookCheck = 37;
195 const int BishopCheck = 6;
196 const int KnightCheck = 14;
199 // init_eval_info() initializes king bitboards for given color adding
200 // pawn attacks. To be done at the beginning of the evaluation.
203 void init_eval_info(const Position& pos, EvalInfo& ei) {
205 const Color Them = (Us == WHITE ? BLACK : WHITE);
206 const Square Down = (Us == WHITE ? DELTA_S : DELTA_N);
208 ei.pinnedPieces[Us] = pos.pinned_pieces(Us);
209 ei.attackedBy[Us][ALL_PIECES] = ei.attackedBy[Us][PAWN] = ei.pi->pawn_attacks(Us);
210 Bitboard b = ei.attackedBy[Them][KING] = pos.attacks_from<KING>(pos.king_square(Them));
212 // Init king safety tables only if we are going to use them
213 if (pos.non_pawn_material(Us) >= QueenValueMg)
215 ei.kingRing[Them] = b | shift_bb<Down>(b);
216 b &= ei.attackedBy[Us][PAWN];
217 ei.kingAttackersCount[Us] = b ? popcount<Max15>(b) : 0;
218 ei.kingAdjacentZoneAttacksCount[Us] = ei.kingAttackersWeight[Us] = 0;
221 ei.kingRing[Them] = ei.kingAttackersCount[Us] = 0;
225 // evaluate_pieces() assigns bonuses and penalties to the pieces of a given color
227 template<PieceType Pt, Color Us, bool Trace>
228 Score evaluate_pieces(const Position& pos, EvalInfo& ei, Score* mobility, Bitboard* mobilityArea) {
232 Score score = SCORE_ZERO;
234 const PieceType NextPt = (Us == WHITE ? Pt : PieceType(Pt + 1));
235 const Color Them = (Us == WHITE ? BLACK : WHITE);
236 const Square* pl = pos.list<Pt>(Us);
238 ei.attackedBy[Us][Pt] = 0;
240 while ((s = *pl++) != SQ_NONE)
242 // Find attacked squares, including x-ray attacks for bishops and rooks
243 b = Pt == BISHOP ? attacks_bb<BISHOP>(s, pos.pieces() ^ pos.pieces(Us, QUEEN))
244 : Pt == ROOK ? attacks_bb< ROOK>(s, pos.pieces() ^ pos.pieces(Us, ROOK, QUEEN))
245 : pos.attacks_from<Pt>(s);
247 if (ei.pinnedPieces[Us] & s)
248 b &= LineBB[pos.king_square(Us)][s];
250 ei.attackedBy[Us][ALL_PIECES] |= ei.attackedBy[Us][Pt] |= b;
252 if (b & ei.kingRing[Them])
254 ei.kingAttackersCount[Us]++;
255 ei.kingAttackersWeight[Us] += KingAttackWeights[Pt];
256 Bitboard bb = b & ei.attackedBy[Them][KING];
258 ei.kingAdjacentZoneAttacksCount[Us] += popcount<Max15>(bb);
262 b &= ~( ei.attackedBy[Them][KNIGHT]
263 | ei.attackedBy[Them][BISHOP]
264 | ei.attackedBy[Them][ROOK]);
266 int mob = popcount<Pt == QUEEN ? Full : Max15>(b & mobilityArea[Us]);
268 mobility[Us] += MobilityBonus[Pt][mob];
270 if (Pt == BISHOP || Pt == KNIGHT)
272 // Bonus for outpost square
273 if ( relative_rank(Us, s) >= RANK_4
274 && !(pos.pieces(Them, PAWN) & pawn_attack_span(Us, s)))
275 score += Outpost[Pt == BISHOP][!!(ei.attackedBy[Us][PAWN] & s)];
277 // Bonus when behind a pawn
278 if ( relative_rank(Us, s) < RANK_5
279 && (pos.pieces(PAWN) & (s + pawn_push(Us))))
280 score += MinorBehindPawn;
282 // Penalty for pawns on same color square of bishop
284 score -= BishopPawns * ei.pi->pawns_on_same_color_squares(Us, s);
286 // An important Chess960 pattern: A cornered bishop blocked by a friendly
287 // pawn diagonally in front of it is a very serious problem, especially
288 // when that pawn is also blocked.
291 && (s == relative_square(Us, SQ_A1) || s == relative_square(Us, SQ_H1)))
293 Square d = pawn_push(Us) + (file_of(s) == FILE_A ? DELTA_E : DELTA_W);
294 if (pos.piece_on(s + d) == make_piece(Us, PAWN))
295 score -= !pos.empty(s + d + pawn_push(Us)) ? TrappedBishopA1H1 * 4
296 : pos.piece_on(s + d + d) == make_piece(Us, PAWN) ? TrappedBishopA1H1 * 2
303 // Bonus for aligning with enemy pawns on the same rank/file
304 if (relative_rank(Us, s) >= RANK_5)
306 Bitboard alignedPawns = pos.pieces(Them, PAWN) & PseudoAttacks[ROOK][s];
308 score += popcount<Max15>(alignedPawns) * RookOnPawn;
311 // Bonus when on an open or semi-open file
312 if (ei.pi->semiopen_file(Us, file_of(s)))
313 score += ei.pi->semiopen_file(Them, file_of(s)) ? RookOnOpenFile : RookOnSemiOpenFile;
315 // Penalize when trapped by the king, even more if king cannot castle
316 if (mob <= 3 && !ei.pi->semiopen_file(Us, file_of(s)))
318 Square ksq = pos.king_square(Us);
320 if ( ((file_of(ksq) < FILE_E) == (file_of(s) < file_of(ksq)))
321 && (rank_of(ksq) == rank_of(s) || relative_rank(Us, ksq) == RANK_1)
322 && !ei.pi->semiopen_side(Us, file_of(ksq), file_of(s) < file_of(ksq)))
323 score -= (TrappedRook - make_score(mob * 22, 0)) * (1 + !pos.can_castle(Us));
329 Tracing::write(Pt, Us, score);
331 // Recursively call evaluate_pieces() of next piece type until KING excluded
332 return score - evaluate_pieces<NextPt, Them, Trace>(pos, ei, mobility, mobilityArea);
336 Score evaluate_pieces<KING, WHITE, false>(const Position&, EvalInfo&, Score*, Bitboard*) { return SCORE_ZERO; }
338 Score evaluate_pieces<KING, WHITE, true>(const Position&, EvalInfo&, Score*, Bitboard*) { return SCORE_ZERO; }
341 // evaluate_king() assigns bonuses and penalties to a king of a given color
343 template<Color Us, bool Trace>
344 Score evaluate_king(const Position& pos, const EvalInfo& ei) {
346 const Color Them = (Us == WHITE ? BLACK : WHITE);
348 Bitboard undefended, b, b1, b2, safe;
350 const Square ksq = pos.king_square(Us);
352 // King shelter and enemy pawns storm
353 Score score = ei.pi->king_safety<Us>(pos, ksq);
355 // Main king safety evaluation
356 if (ei.kingAttackersCount[Them])
358 // Find the attacked squares around the king which have no defenders
359 // apart from the king itself
360 undefended = ei.attackedBy[Them][ALL_PIECES]
361 & ei.attackedBy[Us][KING]
362 & ~( ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
363 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
364 | ei.attackedBy[Us][QUEEN]);
366 // Initialize the 'attackUnits' variable, which is used later on as an
367 // index into the KingDanger[] array. The initial value is based on the
368 // number and types of the enemy's attacking pieces, the number of
369 // attacked and undefended squares around our king and the quality of
370 // the pawn shelter (current 'score' value).
371 attackUnits = std::min(74, ei.kingAttackersCount[Them] * ei.kingAttackersWeight[Them])
372 + 8 * ei.kingAdjacentZoneAttacksCount[Them]
373 + 25 * popcount<Max15>(undefended)
374 + 11 * (ei.pinnedPieces[Us] != 0)
375 - mg_value(score) / 8
376 - !pos.count<QUEEN>(Them) * 60;
378 // Analyse the enemy's safe queen contact checks. Firstly, find the
379 // undefended squares around the king reachable by the enemy queen...
380 b = undefended & ei.attackedBy[Them][QUEEN] & ~pos.pieces(Them);
383 // ...and then remove squares not supported by another enemy piece
384 b &= ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
385 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][ROOK];
388 attackUnits += QueenContactCheck * popcount<Max15>(b);
391 // Analyse the enemy's safe rook contact checks. Firstly, find the
392 // undefended squares around the king reachable by the enemy rooks...
393 b = undefended & ei.attackedBy[Them][ROOK] & ~pos.pieces(Them);
395 // Consider only squares where the enemy's rook gives check
396 b &= PseudoAttacks[ROOK][ksq];
400 // ...and then remove squares not supported by another enemy piece
401 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
402 | ei.attackedBy[Them][BISHOP]);
405 attackUnits += RookContactCheck * popcount<Max15>(b);
408 // Analyse the enemy's safe distance checks for sliders and knights
409 safe = ~(ei.attackedBy[Us][ALL_PIECES] | pos.pieces(Them));
411 b1 = pos.attacks_from<ROOK >(ksq) & safe;
412 b2 = pos.attacks_from<BISHOP>(ksq) & safe;
414 // Enemy queen safe checks
415 b = (b1 | b2) & ei.attackedBy[Them][QUEEN];
417 attackUnits += QueenCheck * popcount<Max15>(b);
419 // Enemy rooks safe checks
420 b = b1 & ei.attackedBy[Them][ROOK];
422 attackUnits += RookCheck * popcount<Max15>(b);
424 // Enemy bishops safe checks
425 b = b2 & ei.attackedBy[Them][BISHOP];
427 attackUnits += BishopCheck * popcount<Max15>(b);
429 // Enemy knights safe checks
430 b = pos.attacks_from<KNIGHT>(ksq) & ei.attackedBy[Them][KNIGHT] & safe;
432 attackUnits += KnightCheck * popcount<Max15>(b);
434 // Finally, extract the king danger score from the KingDanger[]
435 // array and subtract the score from evaluation.
436 score -= KingDanger[std::max(std::min(attackUnits, 399), 0)];
440 Tracing::write(KING, Us, score);
446 // evaluate_threats() assigns bonuses according to the type of attacking piece
447 // and the type of attacked one.
449 template<Color Us, bool Trace>
450 Score evaluate_threats(const Position& pos, const EvalInfo& ei) {
452 const Color Them = (Us == WHITE ? BLACK : WHITE);
453 const Square Up = (Us == WHITE ? DELTA_N : DELTA_S);
454 const Square Left = (Us == WHITE ? DELTA_NW : DELTA_SE);
455 const Square Right = (Us == WHITE ? DELTA_NE : DELTA_SW);
456 const Bitboard TRank2BB = (Us == WHITE ? Rank2BB : Rank7BB);
457 const Bitboard TRank7BB = (Us == WHITE ? Rank7BB : Rank2BB);
459 enum { Defended, Weak };
460 enum { Minor, Major };
462 Bitboard b, weak, defended, safeThreats;
463 Score score = SCORE_ZERO;
465 // Non-pawn enemies attacked by a pawn
466 weak = (pos.pieces(Them) ^ pos.pieces(Them, PAWN)) & ei.attackedBy[Us][PAWN];
470 b = pos.pieces(Us, PAWN) & ( ~ei.attackedBy[Them][ALL_PIECES]
471 | ei.attackedBy[Us][ALL_PIECES]);
473 safeThreats = (shift_bb<Right>(b) | shift_bb<Left>(b)) & weak;
475 if (weak ^ safeThreats)
476 score += ThreatenedByHangingPawn;
479 score += ThreatenedByPawn[type_of(pos.piece_on(pop_lsb(&safeThreats)))];
482 // Non-pawn enemies defended by a pawn
483 defended = (pos.pieces(Them) ^ pos.pieces(Them, PAWN)) & ei.attackedBy[Them][PAWN];
485 // Add a bonus according to the kind of attacking pieces
488 b = defended & (ei.attackedBy[Us][KNIGHT] | ei.attackedBy[Us][BISHOP]);
490 score += Threat[Defended][Minor][type_of(pos.piece_on(pop_lsb(&b)))];
492 b = defended & (ei.attackedBy[Us][ROOK]);
494 score += Threat[Defended][Major][type_of(pos.piece_on(pop_lsb(&b)))];
497 // Enemies not defended by a pawn and under our attack
498 weak = pos.pieces(Them)
499 & ~ei.attackedBy[Them][PAWN]
500 & ei.attackedBy[Us][ALL_PIECES];
502 // Add a bonus according to the kind of attacking pieces
505 b = weak & (ei.attackedBy[Us][KNIGHT] | ei.attackedBy[Us][BISHOP]);
507 score += Threat[Weak][Minor][type_of(pos.piece_on(pop_lsb(&b)))];
509 b = weak & (ei.attackedBy[Us][ROOK] | ei.attackedBy[Us][QUEEN]);
511 score += Threat[Weak][Major][type_of(pos.piece_on(pop_lsb(&b)))];
513 b = weak & ~ei.attackedBy[Them][ALL_PIECES];
515 score += Hanging * popcount<Max15>(b);
517 b = weak & ei.attackedBy[Us][KING];
519 score += more_than_one(b) ? KingOnMany : KingOnOne;
522 // Add a small bonus for safe pawn pushes
523 b = pos.pieces(Us, PAWN) & ~TRank7BB;
524 b = shift_bb<Up>(b | (shift_bb<Up>(b & TRank2BB) & ~pos.pieces()));
527 & ~ei.attackedBy[Them][PAWN]
528 & (ei.attackedBy[Us][ALL_PIECES] | ~ei.attackedBy[Them][ALL_PIECES]);
531 score += popcount<Full>(b) * PawnSafePush;
533 // Add another bonus if the pawn push attacks an enemy piece
534 b = (shift_bb<Left>(b) | shift_bb<Right>(b))
536 & ~ei.attackedBy[Us][PAWN];
539 score += popcount<Max15>(b) * PawnAttackThreat;
542 Tracing::write(Tracing::THREAT, Us, score);
548 // evaluate_passed_pawns() evaluates the passed pawns of the given color
550 template<Color Us, bool Trace>
551 Score evaluate_passed_pawns(const Position& pos, const EvalInfo& ei) {
553 const Color Them = (Us == WHITE ? BLACK : WHITE);
555 Bitboard b, squaresToQueen, defendedSquares, unsafeSquares;
556 Score score = SCORE_ZERO;
558 b = ei.pi->passed_pawns(Us);
562 Square s = pop_lsb(&b);
564 assert(pos.pawn_passed(Us, s));
566 int r = relative_rank(Us, s) - RANK_2;
567 int rr = r * (r - 1);
569 // Base bonus based on rank
570 Value mbonus = Value(17 * rr), ebonus = Value(7 * (rr + r + 1));
574 Square blockSq = s + pawn_push(Us);
576 // Adjust bonus based on the king's proximity
577 ebonus += distance(pos.king_square(Them), blockSq) * 5 * rr
578 - distance(pos.king_square(Us ), blockSq) * 2 * rr;
580 // If blockSq is not the queening square then consider also a second push
581 if (relative_rank(Us, blockSq) != RANK_8)
582 ebonus -= distance(pos.king_square(Us), blockSq + pawn_push(Us)) * rr;
584 // If the pawn is free to advance, then increase the bonus
585 if (pos.empty(blockSq))
587 // If there is a rook or queen attacking/defending the pawn from behind,
588 // consider all the squaresToQueen. Otherwise consider only the squares
589 // in the pawn's path attacked or occupied by the enemy.
590 defendedSquares = unsafeSquares = squaresToQueen = forward_bb(Us, s);
592 Bitboard bb = forward_bb(Them, s) & pos.pieces(ROOK, QUEEN) & pos.attacks_from<ROOK>(s);
594 if (!(pos.pieces(Us) & bb))
595 defendedSquares &= ei.attackedBy[Us][ALL_PIECES];
597 if (!(pos.pieces(Them) & bb))
598 unsafeSquares &= ei.attackedBy[Them][ALL_PIECES] | pos.pieces(Them);
600 // If there aren't any enemy attacks, assign a big bonus. Otherwise
601 // assign a smaller bonus if the block square isn't attacked.
602 int k = !unsafeSquares ? 15 : !(unsafeSquares & blockSq) ? 9 : 0;
604 // If the path to queen is fully defended, assign a big bonus.
605 // Otherwise assign a smaller bonus if the block square is defended.
606 if (defendedSquares == squaresToQueen)
609 else if (defendedSquares & blockSq)
612 mbonus += k * rr, ebonus += k * rr;
614 else if (pos.pieces(Us) & blockSq)
615 mbonus += rr * 3 + r * 2 + 3, ebonus += rr + r * 2;
618 if (pos.count<PAWN>(Us) < pos.count<PAWN>(Them))
619 ebonus += ebonus / 4;
621 score += make_score(mbonus, ebonus);
625 Tracing::write(Tracing::PASSED, Us, score * Weights[PassedPawns]);
627 // Add the scores to the middlegame and endgame eval
628 return score * Weights[PassedPawns];
632 // evaluate_space() computes the space evaluation for a given side. The
633 // space evaluation is a simple bonus based on the number of safe squares
634 // available for minor pieces on the central four files on ranks 2--4. Safe
635 // squares one, two or three squares behind a friendly pawn are counted
636 // twice. Finally, the space bonus is multiplied by a weight. The aim is to
637 // improve play on game opening.
639 Score evaluate_space(const Position& pos, const EvalInfo& ei) {
641 const Color Them = (Us == WHITE ? BLACK : WHITE);
643 // Find the safe squares for our pieces inside the area defined by
644 // SpaceMask[]. A square is unsafe if it is attacked by an enemy
645 // pawn, or if it is undefended and attacked by an enemy piece.
646 Bitboard safe = SpaceMask[Us]
647 & ~pos.pieces(Us, PAWN)
648 & ~ei.attackedBy[Them][PAWN]
649 & (ei.attackedBy[Us][ALL_PIECES] | ~ei.attackedBy[Them][ALL_PIECES]);
651 // Find all squares which are at most three squares behind some friendly pawn
652 Bitboard behind = pos.pieces(Us, PAWN);
653 behind |= (Us == WHITE ? behind >> 8 : behind << 8);
654 behind |= (Us == WHITE ? behind >> 16 : behind << 16);
656 // Since SpaceMask[Us] is fully on our half of the board
657 assert(unsigned(safe >> (Us == WHITE ? 32 : 0)) == 0);
659 // Count safe + (behind & safe) with a single popcount
660 int bonus = popcount<Full>((Us == WHITE ? safe << 32 : safe >> 32) | (behind & safe));
661 int weight = pos.count<KNIGHT>(Us) + pos.count<BISHOP>(Us)
662 + pos.count<KNIGHT>(Them) + pos.count<BISHOP>(Them);
664 return make_score(bonus * weight * weight, 0);
668 // do_evaluate() is the evaluation entry point, called directly from evaluate()
671 Value do_evaluate(const Position& pos) {
673 assert(!pos.checkers());
676 Score score, mobility[2] = { SCORE_ZERO, SCORE_ZERO };
678 // Initialize score by reading the incrementally updated scores included
679 // in the position object (material + piece square tables).
680 // Score is computed from the point of view of white.
681 score = pos.psq_score();
683 // Probe the material hash table
684 ei.mi = Material::probe(pos);
685 score += ei.mi->imbalance();
687 // If we have a specialized evaluation function for the current material
688 // configuration, call it and return.
689 if (ei.mi->specialized_eval_exists())
690 return ei.mi->evaluate(pos);
692 // Probe the pawn hash table
693 ei.pi = Pawns::probe(pos);
694 score += ei.pi->pawns_score() * Weights[PawnStructure];
696 // Initialize attack and king safety bitboards
697 init_eval_info<WHITE>(pos, ei);
698 init_eval_info<BLACK>(pos, ei);
700 ei.attackedBy[WHITE][ALL_PIECES] |= ei.attackedBy[WHITE][KING];
701 ei.attackedBy[BLACK][ALL_PIECES] |= ei.attackedBy[BLACK][KING];
703 // Do not include in mobility squares protected by enemy pawns or occupied by our pawns or king
704 Bitboard mobilityArea[] = { ~(ei.attackedBy[BLACK][PAWN] | pos.pieces(WHITE, PAWN, KING)),
705 ~(ei.attackedBy[WHITE][PAWN] | pos.pieces(BLACK, PAWN, KING)) };
707 // Evaluate pieces and mobility
708 score += evaluate_pieces<KNIGHT, WHITE, Trace>(pos, ei, mobility, mobilityArea);
709 score += (mobility[WHITE] - mobility[BLACK]) * Weights[Mobility];
711 // Evaluate kings after all other pieces because we need complete attack
712 // information when computing the king safety evaluation.
713 score += evaluate_king<WHITE, Trace>(pos, ei)
714 - evaluate_king<BLACK, Trace>(pos, ei);
716 // Evaluate tactical threats, we need full attack information including king
717 score += evaluate_threats<WHITE, Trace>(pos, ei)
718 - evaluate_threats<BLACK, Trace>(pos, ei);
720 // Evaluate passed pawns, we need full attack information including king
721 score += evaluate_passed_pawns<WHITE, Trace>(pos, ei)
722 - evaluate_passed_pawns<BLACK, Trace>(pos, ei);
724 // If both sides have only pawns, score for potential unstoppable pawns
725 if (!pos.non_pawn_material(WHITE) && !pos.non_pawn_material(BLACK))
728 if ((b = ei.pi->passed_pawns(WHITE)) != 0)
729 score += int(relative_rank(WHITE, frontmost_sq(WHITE, b))) * Unstoppable;
731 if ((b = ei.pi->passed_pawns(BLACK)) != 0)
732 score -= int(relative_rank(BLACK, frontmost_sq(BLACK, b))) * Unstoppable;
735 // Evaluate space for both sides, only during opening
736 if (pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK) >= 11756)
737 score += (evaluate_space<WHITE>(pos, ei) - evaluate_space<BLACK>(pos, ei)) * Weights[Space];
739 // Scale winning side if position is more drawish than it appears
740 Color strongSide = eg_value(score) > VALUE_DRAW ? WHITE : BLACK;
741 ScaleFactor sf = ei.mi->scale_factor(pos, strongSide);
743 // If we don't already have an unusual scale factor, check for certain
744 // types of endgames, and use a lower scale for those.
745 if ( ei.mi->game_phase() < PHASE_MIDGAME
746 && (sf == SCALE_FACTOR_NORMAL || sf == SCALE_FACTOR_ONEPAWN))
748 if (pos.opposite_bishops())
750 // Endgame with opposite-colored bishops and no other pieces (ignoring pawns)
751 // is almost a draw, in case of KBP vs KB is even more a draw.
752 if ( pos.non_pawn_material(WHITE) == BishopValueMg
753 && pos.non_pawn_material(BLACK) == BishopValueMg)
754 sf = more_than_one(pos.pieces(PAWN)) ? ScaleFactor(32) : ScaleFactor(8);
756 // Endgame with opposite-colored bishops, but also other pieces. Still
757 // a bit drawish, but not as drawish as with only the two bishops.
759 sf = ScaleFactor(50 * sf / SCALE_FACTOR_NORMAL);
761 // Endings where weaker side can place his king in front of the opponent's
762 // pawns are drawish.
763 else if ( abs(eg_value(score)) <= BishopValueEg
764 && ei.pi->pawn_span(strongSide) <= 1
765 && !pos.pawn_passed(~strongSide, pos.king_square(~strongSide)))
766 sf = ei.pi->pawn_span(strongSide) ? ScaleFactor(56) : ScaleFactor(38);
769 // Interpolate between a middlegame and a (scaled by 'sf') endgame score
770 Value v = mg_value(score) * int(ei.mi->game_phase())
771 + eg_value(score) * int(PHASE_MIDGAME - ei.mi->game_phase()) * sf / SCALE_FACTOR_NORMAL;
773 v /= int(PHASE_MIDGAME);
775 // In case of tracing add all single evaluation terms for both white and black
778 Tracing::write(Tracing::MATERIAL, pos.psq_score());
779 Tracing::write(Tracing::IMBALANCE, ei.mi->imbalance());
780 Tracing::write(PAWN, ei.pi->pawns_score());
781 Tracing::write(Tracing::MOBILITY, mobility[WHITE] * Weights[Mobility]
782 , mobility[BLACK] * Weights[Mobility]);
783 Tracing::write(Tracing::SPACE, evaluate_space<WHITE>(pos, ei) * Weights[Space]
784 , evaluate_space<BLACK>(pos, ei) * Weights[Space]);
785 Tracing::write(Tracing::TOTAL, score);
788 return (pos.side_to_move() == WHITE ? v : -v) + Eval::Tempo; // Side to move point of view
794 double Tracing::to_cp(Value v) { return double(v) / PawnValueEg; }
796 void Tracing::write(int idx, Color c, Score s) { scores[c][idx] = s; }
798 void Tracing::write(int idx, Score w, Score b) {
799 scores[WHITE][idx] = w, scores[BLACK][idx] = b;
802 std::ostream& Tracing::operator<<(std::ostream& os, Term t) {
804 double wScore[] = { to_cp(mg_value(scores[WHITE][t])), to_cp(eg_value(scores[WHITE][t])) };
805 double bScore[] = { to_cp(mg_value(scores[BLACK][t])), to_cp(eg_value(scores[BLACK][t])) };
807 if (t == MATERIAL || t == IMBALANCE || t == Term(PAWN) || t == TOTAL)
808 os << " --- --- | --- --- | ";
810 os << std::setw(5) << wScore[MG] << " " << std::setw(5) << wScore[EG] << " | "
811 << std::setw(5) << bScore[MG] << " " << std::setw(5) << bScore[EG] << " | ";
813 os << std::setw(5) << wScore[MG] - bScore[MG] << " "
814 << std::setw(5) << wScore[EG] - bScore[EG] << " \n";
819 std::string Tracing::do_trace(const Position& pos) {
821 std::memset(scores, 0, sizeof(scores));
823 Value v = do_evaluate<true>(pos);
824 v = pos.side_to_move() == WHITE ? v : -v; // White's point of view
826 std::stringstream ss;
827 ss << std::showpoint << std::noshowpos << std::fixed << std::setprecision(2)
828 << " Eval term | White | Black | Total \n"
829 << " | MG EG | MG EG | MG EG \n"
830 << "----------------+-------------+-------------+-------------\n"
831 << " Material | " << Term(MATERIAL)
832 << " Imbalance | " << Term(IMBALANCE)
833 << " Pawns | " << Term(PAWN)
834 << " Knights | " << Term(KNIGHT)
835 << " Bishop | " << Term(BISHOP)
836 << " Rooks | " << Term(ROOK)
837 << " Queens | " << Term(QUEEN)
838 << " Mobility | " << Term(MOBILITY)
839 << " King safety | " << Term(KING)
840 << " Threats | " << Term(THREAT)
841 << " Passed pawns | " << Term(PASSED)
842 << " Space | " << Term(SPACE)
843 << "----------------+-------------+-------------+-------------\n"
844 << " Total | " << Term(TOTAL);
846 ss << "\nTotal Evaluation: " << to_cp(v) << " (white side)\n";
856 /// evaluate() is the main evaluation function. It returns a static evaluation
857 /// of the position always from the point of view of the side to move.
859 Value evaluate(const Position& pos) {
860 return do_evaluate<false>(pos);
864 /// trace() is like evaluate(), but instead of returning a value, it returns
865 /// a string (suitable for outputting to stdout) that contains the detailed
866 /// descriptions and values of each evaluation term. It's mainly used for
868 std::string trace(const Position& pos) {
869 return Tracing::do_trace(pos);
873 /// init() computes evaluation weights, usually at startup
877 const int MaxSlope = 8700;
878 const int Peak = 1280000;
881 for (int i = 0; i < 400; ++i)
883 t = std::min(Peak, std::min(i * i * 27, t + MaxSlope));
884 KingDanger[i] = make_score(t / 1000, 0) * Weights[KingSafety];