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] contains bonuses for knights and
128 // bishops outposts, bigger if outpost piece is supported by a pawn.
129 const Score Outpost[][2] = {
130 { S(28, 7), S(42,11) }, // Knights
131 { S(12, 3), S(18, 5) } // Bishops
134 // Threat[defended/weak][minor/major attacking][attacked PieceType] contains
135 // bonuses according to which piece type attacks which one.
136 const Score Threat[][2][PIECE_TYPE_NB] = {
137 { { S(0, 0), S( 0, 0), S(19, 37), S(24, 37), S(44, 97), S(35,106) }, // Defended Minor
138 { S(0, 0), S( 0, 0), S( 9, 14), S( 9, 14), S( 7, 14), S(24, 48) } }, // Defended Major
139 { { S(0, 0), S( 0,32), S(33, 41), S(31, 50), S(41,100), S(35,104) }, // Weak Minor
140 { S(0, 0), S( 0,27), S(26, 57), S(26, 57), S(0 , 43), S(23, 51) } } // Weak Major
143 // ThreatenedByPawn[PieceType] contains a penalty according to which piece
144 // type is attacked by an enemy pawn.
145 const Score ThreatenedByPawn[PIECE_TYPE_NB] = {
146 S(0, 0), S(0, 0), S(107, 138), S(84, 122), S(114, 203), S(121, 217)
149 // Passed[mg/eg][rank] contains midgame and endgame bonuses for passed pawns.
150 // We don't use a Score because we process the two components independently.
151 const Value Passed[][RANK_NB] = {
152 { V(0), V( 1), V(34), V(90), V(214), V(328) },
153 { V(7), V(14), V(37), V(63), V(134), V(189) }
156 const Score ThreatenedByHangingPawn = S(40, 60);
158 // Assorted bonuses and penalties used by evaluation
159 const Score KingOnOne = S( 2, 58);
160 const Score KingOnMany = S( 6,125);
161 const Score RookOnPawn = S( 7, 27);
162 const Score RookOnOpenFile = S(43, 21);
163 const Score RookOnSemiOpenFile = S(19, 10);
164 const Score BishopPawns = S( 8, 12);
165 const Score MinorBehindPawn = S(16, 0);
166 const Score TrappedRook = S(92, 0);
167 const Score Unstoppable = S( 0, 20);
168 const Score Hanging = S(31, 26);
169 const Score PawnAttackThreat = S(20, 20);
170 const Score PawnSafePush = S( 5, 5);
172 // Penalty for a bishop on a1/h1 (a8/h8 for black) which is trapped by
173 // a friendly pawn on b2/g2 (b7/g7 for black). This can obviously only
174 // happen in Chess960 games.
175 const Score TrappedBishopA1H1 = S(50, 50);
180 // SpaceMask[Color] contains the area of the board which is considered
181 // by the space evaluation. In the middlegame, each side is given a bonus
182 // based on how many squares inside this area are safe and available for
183 // friendly minor pieces.
184 const Bitboard SpaceMask[COLOR_NB] = {
185 (FileCBB | FileDBB | FileEBB | FileFBB) & (Rank2BB | Rank3BB | Rank4BB),
186 (FileCBB | FileDBB | FileEBB | FileFBB) & (Rank7BB | Rank6BB | Rank5BB)
189 // King danger constants and variables. The king danger scores are looked-up
190 // in KingDanger[]. Various little "meta-bonuses" measuring the strength
191 // of the enemy attack are added up into an integer, which is used as an
192 // index to KingDanger[].
193 Score KingDanger[512];
195 // KingAttackWeights[PieceType] contains king attack weights by piece type
196 const int KingAttackWeights[PIECE_TYPE_NB] = { 0, 0, 7, 5, 4, 1 };
198 // Penalties for enemy's safe checks
199 const int QueenContactCheck = 89;
200 const int RookContactCheck = 71;
201 const int QueenCheck = 50;
202 const int RookCheck = 37;
203 const int BishopCheck = 6;
204 const int KnightCheck = 14;
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);
217 ei.attackedBy[Us][ALL_PIECES] = ei.attackedBy[Us][PAWN] = ei.pi->pawn_attacks(Us);
218 Bitboard b = ei.attackedBy[Them][KING] = pos.attacks_from<KING>(pos.square<KING>(Them));
220 // Init king safety tables only if we are going to use them
221 if (pos.non_pawn_material(Us) >= QueenValueMg)
223 ei.kingRing[Them] = b | shift_bb<Down>(b);
224 b &= ei.attackedBy[Us][PAWN];
225 ei.kingAttackersCount[Us] = b ? popcount<Max15>(b) : 0;
226 ei.kingAdjacentZoneAttacksCount[Us] = ei.kingAttackersWeight[Us] = 0;
229 ei.kingRing[Them] = ei.kingAttackersCount[Us] = 0;
233 // evaluate_pieces() assigns bonuses and penalties to the pieces of a given color
235 template<PieceType Pt, Color Us, bool Trace>
236 Score evaluate_pieces(const Position& pos, EvalInfo& ei, Score* mobility, Bitboard* mobilityArea) {
240 Score score = SCORE_ZERO;
242 const PieceType NextPt = (Us == WHITE ? Pt : PieceType(Pt + 1));
243 const Color Them = (Us == WHITE ? BLACK : WHITE);
244 const Square* pl = pos.squares<Pt>(Us);
246 ei.attackedBy[Us][Pt] = 0;
248 while ((s = *pl++) != SQ_NONE)
250 // Find attacked squares, including x-ray attacks for bishops and rooks
251 b = Pt == BISHOP ? attacks_bb<BISHOP>(s, pos.pieces() ^ pos.pieces(Us, QUEEN))
252 : Pt == ROOK ? attacks_bb< ROOK>(s, pos.pieces() ^ pos.pieces(Us, ROOK, QUEEN))
253 : pos.attacks_from<Pt>(s);
255 if (ei.pinnedPieces[Us] & s)
256 b &= LineBB[pos.square<KING>(Us)][s];
258 ei.attackedBy[Us][ALL_PIECES] |= ei.attackedBy[Us][Pt] |= b;
260 if (b & ei.kingRing[Them])
262 ei.kingAttackersCount[Us]++;
263 ei.kingAttackersWeight[Us] += KingAttackWeights[Pt];
264 Bitboard bb = b & ei.attackedBy[Them][KING];
266 ei.kingAdjacentZoneAttacksCount[Us] += popcount<Max15>(bb);
270 b &= ~( ei.attackedBy[Them][KNIGHT]
271 | ei.attackedBy[Them][BISHOP]
272 | ei.attackedBy[Them][ROOK]);
274 int mob = popcount<Pt == QUEEN ? Full : Max15>(b & mobilityArea[Us]);
276 mobility[Us] += MobilityBonus[Pt][mob];
278 if (Pt == BISHOP || Pt == KNIGHT)
280 // Bonus for outpost square
281 if ( relative_rank(Us, s) >= RANK_4
282 && !(pos.pieces(Them, PAWN) & pawn_attack_span(Us, s)))
283 score += Outpost[Pt == BISHOP][!!(ei.attackedBy[Us][PAWN] & s)];
285 // Bonus when behind a pawn
286 if ( relative_rank(Us, s) < RANK_5
287 && (pos.pieces(PAWN) & (s + pawn_push(Us))))
288 score += MinorBehindPawn;
290 // Penalty for pawns on same color square of bishop
292 score -= BishopPawns * ei.pi->pawns_on_same_color_squares(Us, s);
294 // An important Chess960 pattern: A cornered bishop blocked by a friendly
295 // pawn diagonally in front of it is a very serious problem, especially
296 // when that pawn is also blocked.
299 && (s == relative_square(Us, SQ_A1) || s == relative_square(Us, SQ_H1)))
301 Square d = pawn_push(Us) + (file_of(s) == FILE_A ? DELTA_E : DELTA_W);
302 if (pos.piece_on(s + d) == make_piece(Us, PAWN))
303 score -= !pos.empty(s + d + pawn_push(Us)) ? TrappedBishopA1H1 * 4
304 : pos.piece_on(s + d + d) == make_piece(Us, PAWN) ? TrappedBishopA1H1 * 2
311 // Bonus for aligning with enemy pawns on the same rank/file
312 if (relative_rank(Us, s) >= RANK_5)
314 Bitboard alignedPawns = pos.pieces(Them, PAWN) & PseudoAttacks[ROOK][s];
316 score += popcount<Max15>(alignedPawns) * RookOnPawn;
319 // Bonus when on an open or semi-open file
320 if (ei.pi->semiopen_file(Us, file_of(s)))
321 score += ei.pi->semiopen_file(Them, file_of(s)) ? RookOnOpenFile : RookOnSemiOpenFile;
323 // Penalize when trapped by the king, even more if king cannot castle
324 if (mob <= 3 && !ei.pi->semiopen_file(Us, file_of(s)))
326 Square ksq = pos.square<KING>(Us);
328 if ( ((file_of(ksq) < FILE_E) == (file_of(s) < file_of(ksq)))
329 && (rank_of(ksq) == rank_of(s) || relative_rank(Us, ksq) == RANK_1)
330 && !ei.pi->semiopen_side(Us, file_of(ksq), file_of(s) < file_of(ksq)))
331 score -= (TrappedRook - make_score(mob * 22, 0)) * (1 + !pos.can_castle(Us));
337 Tracing::write(Pt, Us, score);
339 // Recursively call evaluate_pieces() of next piece type until KING excluded
340 return score - evaluate_pieces<NextPt, Them, Trace>(pos, ei, mobility, mobilityArea);
344 Score evaluate_pieces<KING, WHITE, false>(const Position&, EvalInfo&, Score*, Bitboard*) { return SCORE_ZERO; }
346 Score evaluate_pieces<KING, WHITE, true>(const Position&, EvalInfo&, Score*, Bitboard*) { return SCORE_ZERO; }
349 // evaluate_king() assigns bonuses and penalties to a king of a given color
351 template<Color Us, bool Trace>
352 Score evaluate_king(const Position& pos, const EvalInfo& ei) {
354 const Color Them = (Us == WHITE ? BLACK : WHITE);
356 Bitboard undefended, b, b1, b2, safe;
358 const Square ksq = pos.square<KING>(Us);
360 // King shelter and enemy pawns storm
361 Score score = ei.pi->king_safety<Us>(pos, ksq);
363 // Main king safety evaluation
364 if (ei.kingAttackersCount[Them])
366 // Find the attacked squares around the king which have no defenders
367 // apart from the king itself
368 undefended = ei.attackedBy[Them][ALL_PIECES]
369 & ei.attackedBy[Us][KING]
370 & ~( ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
371 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
372 | ei.attackedBy[Us][QUEEN]);
374 // Initialize the 'attackUnits' variable, which is used later on as an
375 // index into the KingDanger[] array. The initial value is based on the
376 // number and types of the enemy's attacking pieces, the number of
377 // attacked and undefended squares around our king and the quality of
378 // the pawn shelter (current 'score' value).
379 attackUnits = std::min(74, ei.kingAttackersCount[Them] * ei.kingAttackersWeight[Them])
380 + 8 * ei.kingAdjacentZoneAttacksCount[Them]
381 + 25 * popcount<Max15>(undefended)
382 + 11 * (ei.pinnedPieces[Us] != 0)
383 - mg_value(score) / 8
384 - !pos.count<QUEEN>(Them) * 60;
386 // Analyse the enemy's safe queen contact checks. Firstly, find the
387 // undefended squares around the king reachable by the enemy queen...
388 b = undefended & ei.attackedBy[Them][QUEEN] & ~pos.pieces(Them);
391 // ...and then remove squares not supported by another enemy piece
392 b &= ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
393 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][ROOK];
396 attackUnits += QueenContactCheck * popcount<Max15>(b);
399 // Analyse the enemy's safe rook contact checks. Firstly, find the
400 // undefended squares around the king reachable by the enemy rooks...
401 b = undefended & ei.attackedBy[Them][ROOK] & ~pos.pieces(Them);
403 // Consider only squares where the enemy's rook gives check
404 b &= PseudoAttacks[ROOK][ksq];
408 // ...and then remove squares not supported by another enemy piece
409 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
410 | ei.attackedBy[Them][BISHOP]);
413 attackUnits += RookContactCheck * popcount<Max15>(b);
416 // Analyse the enemy's safe distance checks for sliders and knights
417 safe = ~(ei.attackedBy[Us][ALL_PIECES] | pos.pieces(Them));
419 b1 = pos.attacks_from<ROOK >(ksq) & safe;
420 b2 = pos.attacks_from<BISHOP>(ksq) & safe;
422 // Enemy queen safe checks
423 b = (b1 | b2) & ei.attackedBy[Them][QUEEN];
425 attackUnits += QueenCheck * popcount<Max15>(b);
427 // Enemy rooks safe checks
428 b = b1 & ei.attackedBy[Them][ROOK];
430 attackUnits += RookCheck * popcount<Max15>(b);
432 // Enemy bishops safe checks
433 b = b2 & ei.attackedBy[Them][BISHOP];
435 attackUnits += BishopCheck * popcount<Max15>(b);
437 // Enemy knights safe checks
438 b = pos.attacks_from<KNIGHT>(ksq) & ei.attackedBy[Them][KNIGHT] & safe;
440 attackUnits += KnightCheck * popcount<Max15>(b);
442 // Finally, extract the king danger score from the KingDanger[]
443 // array and subtract the score from evaluation.
444 score -= KingDanger[std::max(std::min(attackUnits, 399), 0)];
448 Tracing::write(KING, Us, score);
454 // evaluate_threats() assigns bonuses according to the type of attacking piece
455 // and the type of attacked one.
457 template<Color Us, bool Trace>
458 Score evaluate_threats(const Position& pos, const EvalInfo& ei) {
460 const Color Them = (Us == WHITE ? BLACK : WHITE);
461 const Square Up = (Us == WHITE ? DELTA_N : DELTA_S);
462 const Square Left = (Us == WHITE ? DELTA_NW : DELTA_SE);
463 const Square Right = (Us == WHITE ? DELTA_NE : DELTA_SW);
464 const Bitboard TRank2BB = (Us == WHITE ? Rank2BB : Rank7BB);
465 const Bitboard TRank7BB = (Us == WHITE ? Rank7BB : Rank2BB);
467 enum { Defended, Weak };
468 enum { Minor, Major };
470 Bitboard b, weak, defended, safeThreats;
471 Score score = SCORE_ZERO;
473 // Non-pawn enemies attacked by a pawn
474 weak = (pos.pieces(Them) ^ pos.pieces(Them, PAWN)) & ei.attackedBy[Us][PAWN];
478 b = pos.pieces(Us, PAWN) & ( ~ei.attackedBy[Them][ALL_PIECES]
479 | ei.attackedBy[Us][ALL_PIECES]);
481 safeThreats = (shift_bb<Right>(b) | shift_bb<Left>(b)) & weak;
483 if (weak ^ safeThreats)
484 score += ThreatenedByHangingPawn;
487 score += ThreatenedByPawn[type_of(pos.piece_on(pop_lsb(&safeThreats)))];
490 // Non-pawn enemies defended by a pawn
491 defended = (pos.pieces(Them) ^ pos.pieces(Them, PAWN)) & ei.attackedBy[Them][PAWN];
493 // Add a bonus according to the kind of attacking pieces
496 b = defended & (ei.attackedBy[Us][KNIGHT] | ei.attackedBy[Us][BISHOP]);
498 score += Threat[Defended][Minor][type_of(pos.piece_on(pop_lsb(&b)))];
500 b = defended & (ei.attackedBy[Us][ROOK]);
502 score += Threat[Defended][Major][type_of(pos.piece_on(pop_lsb(&b)))];
505 // Enemies not defended by a pawn and under our attack
506 weak = pos.pieces(Them)
507 & ~ei.attackedBy[Them][PAWN]
508 & ei.attackedBy[Us][ALL_PIECES];
510 // Add a bonus according to the kind of attacking pieces
513 b = weak & (ei.attackedBy[Us][KNIGHT] | ei.attackedBy[Us][BISHOP]);
515 score += Threat[Weak][Minor][type_of(pos.piece_on(pop_lsb(&b)))];
517 b = weak & (ei.attackedBy[Us][ROOK] | ei.attackedBy[Us][QUEEN]);
519 score += Threat[Weak][Major][type_of(pos.piece_on(pop_lsb(&b)))];
521 b = weak & ~ei.attackedBy[Them][ALL_PIECES];
523 score += Hanging * popcount<Max15>(b);
525 b = weak & ei.attackedBy[Us][KING];
527 score += more_than_one(b) ? KingOnMany : KingOnOne;
530 // Add a small bonus for safe pawn pushes
531 b = pos.pieces(Us, PAWN) & ~TRank7BB;
532 b = shift_bb<Up>(b | (shift_bb<Up>(b & TRank2BB) & ~pos.pieces()));
535 & ~ei.attackedBy[Them][PAWN]
536 & (ei.attackedBy[Us][ALL_PIECES] | ~ei.attackedBy[Them][ALL_PIECES]);
539 score += popcount<Full>(b) * PawnSafePush;
541 // Add another bonus if the pawn push attacks an enemy piece
542 b = (shift_bb<Left>(b) | shift_bb<Right>(b))
544 & ~ei.attackedBy[Us][PAWN];
547 score += popcount<Max15>(b) * PawnAttackThreat;
550 Tracing::write(Tracing::THREAT, Us, score);
556 // evaluate_passed_pawns() evaluates the passed pawns of the given color
558 template<Color Us, bool Trace>
559 Score evaluate_passed_pawns(const Position& pos, const EvalInfo& ei) {
561 const Color Them = (Us == WHITE ? BLACK : WHITE);
563 Bitboard b, squaresToQueen, defendedSquares, unsafeSquares;
564 Score score = SCORE_ZERO;
566 b = ei.pi->passed_pawns(Us);
570 Square s = pop_lsb(&b);
572 assert(pos.pawn_passed(Us, s));
574 int r = relative_rank(Us, s) - RANK_2;
575 int rr = r * (r - 1);
577 Value mbonus = Passed[MG][r], ebonus = Passed[EG][r];
581 Square blockSq = s + pawn_push(Us);
583 // Adjust bonus based on the king's proximity
584 ebonus += distance(pos.square<KING>(Them), blockSq) * 5 * rr
585 - distance(pos.square<KING>(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.square<KING>(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, score * Weights[PassedPawns]);
634 // Add the scores to the middlegame and endgame eval
635 return score * Weights[PassedPawns];
639 // evaluate_space() computes the space evaluation for a given side. The
640 // space evaluation is a simple bonus based on the number of safe squares
641 // available for minor pieces on the central four files on ranks 2--4. Safe
642 // squares one, two or three squares behind a friendly pawn are counted
643 // twice. Finally, the space bonus is multiplied by a weight. The aim is to
644 // improve play on game opening.
646 Score evaluate_space(const Position& pos, const EvalInfo& ei) {
648 const Color Them = (Us == WHITE ? BLACK : WHITE);
650 // Find the safe squares for our pieces inside the area defined by
651 // SpaceMask[]. A square is unsafe if it is attacked by an enemy
652 // pawn, or if it is undefended and attacked by an enemy piece.
653 Bitboard safe = SpaceMask[Us]
654 & ~pos.pieces(Us, PAWN)
655 & ~ei.attackedBy[Them][PAWN]
656 & (ei.attackedBy[Us][ALL_PIECES] | ~ei.attackedBy[Them][ALL_PIECES]);
658 // Find all squares which are at most three squares behind some friendly pawn
659 Bitboard behind = pos.pieces(Us, PAWN);
660 behind |= (Us == WHITE ? behind >> 8 : behind << 8);
661 behind |= (Us == WHITE ? behind >> 16 : behind << 16);
663 // Since SpaceMask[Us] is fully on our half of the board
664 assert(unsigned(safe >> (Us == WHITE ? 32 : 0)) == 0);
666 // Count safe + (behind & safe) with a single popcount
667 int bonus = popcount<Full>((Us == WHITE ? safe << 32 : safe >> 32) | (behind & safe));
668 int weight = pos.count<KNIGHT>(Us) + pos.count<BISHOP>(Us)
669 + pos.count<KNIGHT>(Them) + pos.count<BISHOP>(Them);
671 return make_score(bonus * weight * weight, 0);
675 // do_evaluate() is the evaluation entry point, called directly from evaluate()
678 Value do_evaluate(const Position& pos) {
680 assert(!pos.checkers());
683 Score score, mobility[2] = { SCORE_ZERO, SCORE_ZERO };
685 // Initialize score by reading the incrementally updated scores included
686 // in the position object (material + piece square tables).
687 // Score is computed from the point of view of white.
688 score = pos.psq_score();
690 // Probe the material hash table
691 ei.mi = Material::probe(pos);
692 score += ei.mi->imbalance();
694 // If we have a specialized evaluation function for the current material
695 // configuration, call it and return.
696 if (ei.mi->specialized_eval_exists())
697 return ei.mi->evaluate(pos);
699 // Probe the pawn hash table
700 ei.pi = Pawns::probe(pos);
701 score += ei.pi->pawns_score() * Weights[PawnStructure];
703 // Initialize attack and king safety bitboards
704 init_eval_info<WHITE>(pos, ei);
705 init_eval_info<BLACK>(pos, ei);
707 ei.attackedBy[WHITE][ALL_PIECES] |= ei.attackedBy[WHITE][KING];
708 ei.attackedBy[BLACK][ALL_PIECES] |= ei.attackedBy[BLACK][KING];
710 // Pawns blocked or on ranks 2 and 3. Will be excluded from the mobility area
711 Bitboard blockedPawns[] = {
712 pos.pieces(WHITE, PAWN) & (shift_bb<DELTA_S>(pos.pieces()) | Rank2BB | Rank3BB),
713 pos.pieces(BLACK, PAWN) & (shift_bb<DELTA_N>(pos.pieces()) | Rank7BB | Rank6BB)
716 // Do not include in mobility squares protected by enemy pawns, or occupied
717 // by our blocked pawns or king.
718 Bitboard mobilityArea[] = {
719 ~(ei.attackedBy[BLACK][PAWN] | blockedPawns[WHITE] | pos.square<KING>(WHITE)),
720 ~(ei.attackedBy[WHITE][PAWN] | blockedPawns[BLACK] | pos.square<KING>(BLACK))
723 // Evaluate pieces and mobility
724 score += evaluate_pieces<KNIGHT, WHITE, Trace>(pos, ei, mobility, mobilityArea);
725 score += (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))
744 if ((b = ei.pi->passed_pawns(WHITE)) != 0)
745 score += int(relative_rank(WHITE, frontmost_sq(WHITE, b))) * Unstoppable;
747 if ((b = ei.pi->passed_pawns(BLACK)) != 0)
748 score -= int(relative_rank(BLACK, frontmost_sq(BLACK, b))) * Unstoppable;
751 // Evaluate space for both sides, only during opening
752 if (pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK) >= 11756)
753 score += (evaluate_space<WHITE>(pos, ei) - evaluate_space<BLACK>(pos, ei)) * Weights[Space];
755 // Scale winning side if position is more drawish than it appears
756 Color strongSide = eg_value(score) > VALUE_DRAW ? WHITE : BLACK;
757 ScaleFactor sf = ei.mi->scale_factor(pos, strongSide);
759 // If we don't already have an unusual scale factor, check for certain
760 // types of endgames, and use a lower scale for those.
761 if ( ei.mi->game_phase() < PHASE_MIDGAME
762 && (sf == SCALE_FACTOR_NORMAL || sf == SCALE_FACTOR_ONEPAWN))
764 if (pos.opposite_bishops())
766 // Endgame with opposite-colored bishops and no other pieces (ignoring pawns)
767 // is almost a draw, in case of KBP vs KB is even more a draw.
768 if ( pos.non_pawn_material(WHITE) == BishopValueMg
769 && pos.non_pawn_material(BLACK) == BishopValueMg)
770 sf = more_than_one(pos.pieces(PAWN)) ? ScaleFactor(32) : ScaleFactor(8);
772 // Endgame with opposite-colored bishops, but also other pieces. Still
773 // a bit drawish, but not as drawish as with only the two bishops.
775 sf = ScaleFactor(50 * sf / SCALE_FACTOR_NORMAL);
777 // Endings where weaker side can place his king in front of the opponent's
778 // pawns are drawish.
779 else if ( abs(eg_value(score)) <= BishopValueEg
780 && ei.pi->pawn_span(strongSide) <= 1
781 && !pos.pawn_passed(~strongSide, pos.square<KING>(~strongSide)))
782 sf = ei.pi->pawn_span(strongSide) ? ScaleFactor(56) : ScaleFactor(38);
785 // Interpolate between a middlegame and a (scaled by 'sf') endgame score
786 Value v = mg_value(score) * int(ei.mi->game_phase())
787 + eg_value(score) * int(PHASE_MIDGAME - ei.mi->game_phase()) * sf / SCALE_FACTOR_NORMAL;
789 v /= int(PHASE_MIDGAME);
791 // In case of tracing add all single evaluation terms for both white and black
794 Tracing::write(Tracing::MATERIAL, pos.psq_score());
795 Tracing::write(Tracing::IMBALANCE, ei.mi->imbalance());
796 Tracing::write(PAWN, ei.pi->pawns_score());
797 Tracing::write(Tracing::MOBILITY, mobility[WHITE] * Weights[Mobility]
798 , mobility[BLACK] * Weights[Mobility]);
799 Tracing::write(Tracing::SPACE, evaluate_space<WHITE>(pos, ei) * Weights[Space]
800 , evaluate_space<BLACK>(pos, ei) * Weights[Space]);
801 Tracing::write(Tracing::TOTAL, score);
804 return (pos.side_to_move() == WHITE ? v : -v) + Eval::Tempo; // Side to move point of view
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) {
815 scores[WHITE][idx] = w, scores[BLACK][idx] = b;
818 std::ostream& Tracing::operator<<(std::ostream& os, Term t) {
820 double wScore[] = { to_cp(mg_value(scores[WHITE][t])), to_cp(eg_value(scores[WHITE][t])) };
821 double bScore[] = { to_cp(mg_value(scores[BLACK][t])), to_cp(eg_value(scores[BLACK][t])) };
823 if (t == MATERIAL || t == IMBALANCE || t == Term(PAWN) || t == TOTAL)
824 os << " --- --- | --- --- | ";
826 os << std::setw(5) << wScore[MG] << " " << std::setw(5) << wScore[EG] << " | "
827 << std::setw(5) << bScore[MG] << " " << std::setw(5) << bScore[EG] << " | ";
829 os << std::setw(5) << wScore[MG] - bScore[MG] << " "
830 << std::setw(5) << wScore[EG] - bScore[EG] << " \n";
835 std::string Tracing::do_trace(const Position& pos) {
837 std::memset(scores, 0, sizeof(scores));
839 Value v = do_evaluate<true>(pos);
840 v = pos.side_to_move() == WHITE ? v : -v; // White's point of view
842 std::stringstream ss;
843 ss << std::showpoint << std::noshowpos << std::fixed << std::setprecision(2)
844 << " Eval term | White | Black | Total \n"
845 << " | MG EG | MG EG | MG EG \n"
846 << "----------------+-------------+-------------+-------------\n"
847 << " Material | " << Term(MATERIAL)
848 << " Imbalance | " << Term(IMBALANCE)
849 << " Pawns | " << Term(PAWN)
850 << " Knights | " << Term(KNIGHT)
851 << " Bishop | " << Term(BISHOP)
852 << " Rooks | " << Term(ROOK)
853 << " Queens | " << Term(QUEEN)
854 << " Mobility | " << Term(MOBILITY)
855 << " King safety | " << Term(KING)
856 << " Threats | " << Term(THREAT)
857 << " Passed pawns | " << Term(PASSED)
858 << " Space | " << Term(SPACE)
859 << "----------------+-------------+-------------+-------------\n"
860 << " Total | " << Term(TOTAL);
862 ss << "\nTotal Evaluation: " << to_cp(v) << " (white side)\n";
872 /// evaluate() is the main evaluation function. It returns a static evaluation
873 /// of the position always from the point of view of the side to move.
875 Value evaluate(const Position& pos) {
876 return do_evaluate<false>(pos);
880 /// trace() is like evaluate(), but instead of returning a value, it returns
881 /// a string (suitable for outputting to stdout) that contains the detailed
882 /// descriptions and values of each evaluation term. It's mainly used for
884 std::string trace(const Position& pos) {
885 return Tracing::do_trace(pos);
889 /// init() computes evaluation weights, usually at startup
893 const int MaxSlope = 8700;
894 const int Peak = 1280000;
897 for (int i = 0; i < 400; ++i)
899 t = std::min(Peak, std::min(i * i * 27, t + MaxSlope));
900 KingDanger[i] = make_score(t / 1000, 0) * Weights[KingSafety];