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);
171 // Penalty for a bishop on a1/h1 (a8/h8 for black) which is trapped by
172 // a friendly pawn on b2/g2 (b7/g7 for black). This can obviously only
173 // happen in Chess960 games.
174 const Score TrappedBishopA1H1 = S(50, 50);
179 // SpaceMask[Color] contains the area of the board which is considered
180 // by the space evaluation. In the middlegame, each side is given a bonus
181 // based on how many squares inside this area are safe and available for
182 // friendly minor pieces.
183 const Bitboard SpaceMask[COLOR_NB] = {
184 (FileCBB | FileDBB | FileEBB | FileFBB) & (Rank2BB | Rank3BB | Rank4BB),
185 (FileCBB | FileDBB | FileEBB | FileFBB) & (Rank7BB | Rank6BB | Rank5BB)
188 // King danger constants and variables. The king danger scores are looked-up
189 // in KingDanger[]. Various little "meta-bonuses" measuring the strength
190 // of the enemy attack are added up into an integer, which is used as an
191 // index to KingDanger[].
192 Score KingDanger[512];
194 // KingAttackWeights[PieceType] contains king attack weights by piece type
195 const int KingAttackWeights[PIECE_TYPE_NB] = { 0, 0, 7, 5, 4, 1 };
197 // Penalties for enemy's safe checks
198 const int QueenContactCheck = 89;
199 const int RookContactCheck = 71;
200 const int QueenCheck = 50;
201 const int RookCheck = 37;
202 const int BishopCheck = 6;
203 const int KnightCheck = 14;
206 // init_eval_info() initializes king bitboards for given color adding
207 // pawn attacks. To be done at the beginning of the evaluation.
210 void init_eval_info(const Position& pos, EvalInfo& ei) {
212 const Color Them = (Us == WHITE ? BLACK : WHITE);
213 const Square Down = (Us == WHITE ? DELTA_S : DELTA_N);
215 ei.pinnedPieces[Us] = pos.pinned_pieces(Us);
216 ei.attackedBy[Us][ALL_PIECES] = ei.attackedBy[Us][PAWN] = ei.pi->pawn_attacks(Us);
217 Bitboard b = ei.attackedBy[Them][KING] = pos.attacks_from<KING>(pos.square<KING>(Them));
219 // Init king safety tables only if we are going to use them
220 if (pos.non_pawn_material(Us) >= QueenValueMg)
222 ei.kingRing[Them] = b | shift_bb<Down>(b);
223 b &= ei.attackedBy[Us][PAWN];
224 ei.kingAttackersCount[Us] = b ? popcount<Max15>(b) : 0;
225 ei.kingAdjacentZoneAttacksCount[Us] = ei.kingAttackersWeight[Us] = 0;
228 ei.kingRing[Them] = ei.kingAttackersCount[Us] = 0;
232 // evaluate_pieces() assigns bonuses and penalties to the pieces of a given color
234 template<PieceType Pt, Color Us, bool Trace>
235 Score evaluate_pieces(const Position& pos, EvalInfo& ei, Score* mobility, Bitboard* mobilityArea) {
239 Score score = SCORE_ZERO;
241 const PieceType NextPt = (Us == WHITE ? Pt : PieceType(Pt + 1));
242 const Color Them = (Us == WHITE ? BLACK : WHITE);
243 const Square* pl = pos.squares<Pt>(Us);
245 ei.attackedBy[Us][Pt] = 0;
247 while ((s = *pl++) != SQ_NONE)
249 // Find attacked squares, including x-ray attacks for bishops and rooks
250 b = Pt == BISHOP ? attacks_bb<BISHOP>(s, pos.pieces() ^ pos.pieces(Us, QUEEN))
251 : Pt == ROOK ? attacks_bb< ROOK>(s, pos.pieces() ^ pos.pieces(Us, ROOK, QUEEN))
252 : pos.attacks_from<Pt>(s);
254 if (ei.pinnedPieces[Us] & s)
255 b &= LineBB[pos.square<KING>(Us)][s];
257 ei.attackedBy[Us][ALL_PIECES] |= ei.attackedBy[Us][Pt] |= b;
259 if (b & ei.kingRing[Them])
261 ei.kingAttackersCount[Us]++;
262 ei.kingAttackersWeight[Us] += KingAttackWeights[Pt];
263 Bitboard bb = b & ei.attackedBy[Them][KING];
265 ei.kingAdjacentZoneAttacksCount[Us] += popcount<Max15>(bb);
269 b &= ~( ei.attackedBy[Them][KNIGHT]
270 | ei.attackedBy[Them][BISHOP]
271 | ei.attackedBy[Them][ROOK]);
273 int mob = popcount<Pt == QUEEN ? Full : Max15>(b & mobilityArea[Us]);
275 mobility[Us] += MobilityBonus[Pt][mob];
277 if (Pt == BISHOP || Pt == KNIGHT)
279 // Bonus for outpost square
280 if ( relative_rank(Us, s) >= RANK_4
281 && !(pos.pieces(Them, PAWN) & pawn_attack_span(Us, s)))
282 score += Outpost[Pt == BISHOP][!!(ei.attackedBy[Us][PAWN] & s)];
284 // Bonus when behind a pawn
285 if ( relative_rank(Us, s) < RANK_5
286 && (pos.pieces(PAWN) & (s + pawn_push(Us))))
287 score += MinorBehindPawn;
289 // Penalty for pawns on same color square of bishop
291 score -= BishopPawns * ei.pi->pawns_on_same_color_squares(Us, s);
293 // An important Chess960 pattern: A cornered bishop blocked by a friendly
294 // pawn diagonally in front of it is a very serious problem, especially
295 // when that pawn is also blocked.
298 && (s == relative_square(Us, SQ_A1) || s == relative_square(Us, SQ_H1)))
300 Square d = pawn_push(Us) + (file_of(s) == FILE_A ? DELTA_E : DELTA_W);
301 if (pos.piece_on(s + d) == make_piece(Us, PAWN))
302 score -= !pos.empty(s + d + pawn_push(Us)) ? TrappedBishopA1H1 * 4
303 : pos.piece_on(s + d + d) == make_piece(Us, PAWN) ? TrappedBishopA1H1 * 2
310 // Bonus for aligning with enemy pawns on the same rank/file
311 if (relative_rank(Us, s) >= RANK_5)
313 Bitboard alignedPawns = pos.pieces(Them, PAWN) & PseudoAttacks[ROOK][s];
315 score += popcount<Max15>(alignedPawns) * RookOnPawn;
318 // Bonus when on an open or semi-open file
319 if (ei.pi->semiopen_file(Us, file_of(s)))
320 score += ei.pi->semiopen_file(Them, file_of(s)) ? RookOnOpenFile : RookOnSemiOpenFile;
322 // Penalize when trapped by the king, even more if king cannot castle
323 if (mob <= 3 && !ei.pi->semiopen_file(Us, file_of(s)))
325 Square ksq = pos.square<KING>(Us);
327 if ( ((file_of(ksq) < FILE_E) == (file_of(s) < file_of(ksq)))
328 && (rank_of(ksq) == rank_of(s) || relative_rank(Us, ksq) == RANK_1)
329 && !ei.pi->semiopen_side(Us, file_of(ksq), file_of(s) < file_of(ksq)))
330 score -= (TrappedRook - make_score(mob * 22, 0)) * (1 + !pos.can_castle(Us));
336 Tracing::write(Pt, Us, score);
338 // Recursively call evaluate_pieces() of next piece type until KING excluded
339 return score - evaluate_pieces<NextPt, Them, Trace>(pos, ei, mobility, mobilityArea);
343 Score evaluate_pieces<KING, WHITE, false>(const Position&, EvalInfo&, Score*, Bitboard*) { return SCORE_ZERO; }
345 Score evaluate_pieces<KING, WHITE, true>(const Position&, EvalInfo&, Score*, Bitboard*) { return SCORE_ZERO; }
348 // evaluate_king() assigns bonuses and penalties to a king of a given color
350 template<Color Us, bool Trace>
351 Score evaluate_king(const Position& pos, const EvalInfo& ei) {
353 const Color Them = (Us == WHITE ? BLACK : WHITE);
355 Bitboard undefended, b, b1, b2, safe;
357 const Square ksq = pos.square<KING>(Us);
359 // King shelter and enemy pawns storm
360 Score score = ei.pi->king_safety<Us>(pos, ksq);
362 // Main king safety evaluation
363 if (ei.kingAttackersCount[Them])
365 // Find the attacked squares around the king which have no defenders
366 // apart from the king itself
367 undefended = ei.attackedBy[Them][ALL_PIECES]
368 & ei.attackedBy[Us][KING]
369 & ~( ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
370 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
371 | ei.attackedBy[Us][QUEEN]);
373 // Initialize the 'attackUnits' variable, which is used later on as an
374 // index into the KingDanger[] array. The initial value is based on the
375 // number and types of the enemy's attacking pieces, the number of
376 // attacked and undefended squares around our king and the quality of
377 // the pawn shelter (current 'score' value).
378 attackUnits = std::min(74, ei.kingAttackersCount[Them] * ei.kingAttackersWeight[Them])
379 + 8 * ei.kingAdjacentZoneAttacksCount[Them]
380 + 25 * popcount<Max15>(undefended)
381 + 11 * (ei.pinnedPieces[Us] != 0)
382 - mg_value(score) / 8
383 - !pos.count<QUEEN>(Them) * 60;
385 // Analyse the enemy's safe queen contact checks. Firstly, find the
386 // undefended squares around the king reachable by the enemy queen...
387 b = undefended & ei.attackedBy[Them][QUEEN] & ~pos.pieces(Them);
390 // ...and then remove squares not supported by another enemy piece
391 b &= ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
392 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][ROOK];
395 attackUnits += QueenContactCheck * popcount<Max15>(b);
398 // Analyse the enemy's safe rook contact checks. Firstly, find the
399 // undefended squares around the king reachable by the enemy rooks...
400 b = undefended & ei.attackedBy[Them][ROOK] & ~pos.pieces(Them);
402 // Consider only squares where the enemy's rook gives check
403 b &= PseudoAttacks[ROOK][ksq];
407 // ...and then remove squares not supported by another enemy piece
408 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
409 | ei.attackedBy[Them][BISHOP]);
412 attackUnits += RookContactCheck * popcount<Max15>(b);
415 // Analyse the enemy's safe distance checks for sliders and knights
416 safe = ~(ei.attackedBy[Us][ALL_PIECES] | pos.pieces(Them));
418 b1 = pos.attacks_from<ROOK >(ksq) & safe;
419 b2 = pos.attacks_from<BISHOP>(ksq) & safe;
421 // Enemy queen safe checks
422 b = (b1 | b2) & ei.attackedBy[Them][QUEEN];
424 attackUnits += QueenCheck * popcount<Max15>(b);
426 // Enemy rooks safe checks
427 b = b1 & ei.attackedBy[Them][ROOK];
429 attackUnits += RookCheck * popcount<Max15>(b);
431 // Enemy bishops safe checks
432 b = b2 & ei.attackedBy[Them][BISHOP];
434 attackUnits += BishopCheck * popcount<Max15>(b);
436 // Enemy knights safe checks
437 b = pos.attacks_from<KNIGHT>(ksq) & ei.attackedBy[Them][KNIGHT] & safe;
439 attackUnits += KnightCheck * popcount<Max15>(b);
441 // Finally, extract the king danger score from the KingDanger[]
442 // array and subtract the score from evaluation.
443 score -= KingDanger[std::max(std::min(attackUnits, 399), 0)];
447 Tracing::write(KING, Us, score);
453 // evaluate_threats() assigns bonuses according to the type of attacking piece
454 // and the type of attacked one.
456 template<Color Us, bool Trace>
457 Score evaluate_threats(const Position& pos, const EvalInfo& ei) {
459 const Color Them = (Us == WHITE ? BLACK : WHITE);
460 const Square Up = (Us == WHITE ? DELTA_N : DELTA_S);
461 const Square Left = (Us == WHITE ? DELTA_NW : DELTA_SE);
462 const Square Right = (Us == WHITE ? DELTA_NE : DELTA_SW);
463 const Bitboard TRank2BB = (Us == WHITE ? Rank2BB : Rank7BB);
464 const Bitboard TRank7BB = (Us == WHITE ? Rank7BB : Rank2BB);
466 enum { Defended, Weak };
467 enum { Minor, Major };
469 Bitboard b, weak, defended, safeThreats;
470 Score score = SCORE_ZERO;
472 // Non-pawn enemies attacked by a pawn
473 weak = (pos.pieces(Them) ^ pos.pieces(Them, PAWN)) & ei.attackedBy[Us][PAWN];
477 b = pos.pieces(Us, PAWN) & ( ~ei.attackedBy[Them][ALL_PIECES]
478 | ei.attackedBy[Us][ALL_PIECES]);
480 safeThreats = (shift_bb<Right>(b) | shift_bb<Left>(b)) & weak;
482 if (weak ^ safeThreats)
483 score += ThreatenedByHangingPawn;
486 score += ThreatenedByPawn[type_of(pos.piece_on(pop_lsb(&safeThreats)))];
489 // Non-pawn enemies defended by a pawn
490 defended = (pos.pieces(Them) ^ pos.pieces(Them, PAWN)) & ei.attackedBy[Them][PAWN];
492 // Add a bonus according to the kind of attacking pieces
495 b = defended & (ei.attackedBy[Us][KNIGHT] | ei.attackedBy[Us][BISHOP]);
497 score += Threat[Defended][Minor][type_of(pos.piece_on(pop_lsb(&b)))];
499 b = defended & (ei.attackedBy[Us][ROOK]);
501 score += Threat[Defended][Major][type_of(pos.piece_on(pop_lsb(&b)))];
504 // Enemies not defended by a pawn and under our attack
505 weak = pos.pieces(Them)
506 & ~ei.attackedBy[Them][PAWN]
507 & ei.attackedBy[Us][ALL_PIECES];
509 // Add a bonus according to the kind of attacking pieces
512 b = weak & (ei.attackedBy[Us][KNIGHT] | ei.attackedBy[Us][BISHOP]);
514 score += Threat[Weak][Minor][type_of(pos.piece_on(pop_lsb(&b)))];
516 b = weak & (ei.attackedBy[Us][ROOK] | ei.attackedBy[Us][QUEEN]);
518 score += Threat[Weak][Major][type_of(pos.piece_on(pop_lsb(&b)))];
520 b = weak & ~ei.attackedBy[Them][ALL_PIECES];
522 score += Hanging * popcount<Max15>(b);
524 b = weak & ei.attackedBy[Us][KING];
526 score += more_than_one(b) ? KingOnMany : KingOnOne;
529 // Bonus if some pawns can safely push and attack an enemy piece
530 b = pos.pieces(Us, PAWN) & ~TRank7BB;
531 b = shift_bb<Up>(b | (shift_bb<Up>(b & TRank2BB) & ~pos.pieces()));
534 & ~ei.attackedBy[Them][PAWN]
535 & (ei.attackedBy[Us][ALL_PIECES] | ~ei.attackedBy[Them][ALL_PIECES]);
537 b = (shift_bb<Left>(b) | shift_bb<Right>(b))
539 & ~ei.attackedBy[Us][PAWN];
542 score += popcount<Max15>(b) * PawnAttackThreat;
545 Tracing::write(Tracing::THREAT, Us, score);
551 // evaluate_passed_pawns() evaluates the passed pawns of the given color
553 template<Color Us, bool Trace>
554 Score evaluate_passed_pawns(const Position& pos, const EvalInfo& ei) {
556 const Color Them = (Us == WHITE ? BLACK : WHITE);
558 Bitboard b, squaresToQueen, defendedSquares, unsafeSquares;
559 Score score = SCORE_ZERO;
561 b = ei.pi->passed_pawns(Us);
565 Square s = pop_lsb(&b);
567 assert(pos.pawn_passed(Us, s));
569 int r = relative_rank(Us, s) - RANK_2;
570 int rr = r * (r - 1);
572 Value mbonus = Passed[MG][r], ebonus = Passed[EG][r];
576 Square blockSq = s + pawn_push(Us);
578 // Adjust bonus based on the king's proximity
579 ebonus += distance(pos.square<KING>(Them), blockSq) * 5 * rr
580 - distance(pos.square<KING>(Us ), blockSq) * 2 * rr;
582 // If blockSq is not the queening square then consider also a second push
583 if (relative_rank(Us, blockSq) != RANK_8)
584 ebonus -= distance(pos.square<KING>(Us), blockSq + pawn_push(Us)) * rr;
586 // If the pawn is free to advance, then increase the bonus
587 if (pos.empty(blockSq))
589 // If there is a rook or queen attacking/defending the pawn from behind,
590 // consider all the squaresToQueen. Otherwise consider only the squares
591 // in the pawn's path attacked or occupied by the enemy.
592 defendedSquares = unsafeSquares = squaresToQueen = forward_bb(Us, s);
594 Bitboard bb = forward_bb(Them, s) & pos.pieces(ROOK, QUEEN) & pos.attacks_from<ROOK>(s);
596 if (!(pos.pieces(Us) & bb))
597 defendedSquares &= ei.attackedBy[Us][ALL_PIECES];
599 if (!(pos.pieces(Them) & bb))
600 unsafeSquares &= ei.attackedBy[Them][ALL_PIECES] | pos.pieces(Them);
602 // If there aren't any enemy attacks, assign a big bonus. Otherwise
603 // assign a smaller bonus if the block square isn't attacked.
604 int k = !unsafeSquares ? 15 : !(unsafeSquares & blockSq) ? 9 : 0;
606 // If the path to queen is fully defended, assign a big bonus.
607 // Otherwise assign a smaller bonus if the block square is defended.
608 if (defendedSquares == squaresToQueen)
611 else if (defendedSquares & blockSq)
614 mbonus += k * rr, ebonus += k * rr;
616 else if (pos.pieces(Us) & blockSq)
617 mbonus += rr * 3 + r * 2 + 3, ebonus += rr + r * 2;
620 if (pos.count<PAWN>(Us) < pos.count<PAWN>(Them))
621 ebonus += ebonus / 4;
623 score += make_score(mbonus, ebonus);
627 Tracing::write(Tracing::PASSED, Us, score * Weights[PassedPawns]);
629 // Add the scores to the middlegame and endgame eval
630 return score * Weights[PassedPawns];
634 // evaluate_space() computes the space evaluation for a given side. The
635 // space evaluation is a simple bonus based on the number of safe squares
636 // available for minor pieces on the central four files on ranks 2--4. Safe
637 // squares one, two or three squares behind a friendly pawn are counted
638 // twice. Finally, the space bonus is multiplied by a weight. The aim is to
639 // improve play on game opening.
641 Score evaluate_space(const Position& pos, const EvalInfo& ei) {
643 const Color Them = (Us == WHITE ? BLACK : WHITE);
645 // Find the safe squares for our pieces inside the area defined by
646 // SpaceMask[]. A square is unsafe if it is attacked by an enemy
647 // pawn, or if it is undefended and attacked by an enemy piece.
648 Bitboard safe = SpaceMask[Us]
649 & ~pos.pieces(Us, PAWN)
650 & ~ei.attackedBy[Them][PAWN]
651 & (ei.attackedBy[Us][ALL_PIECES] | ~ei.attackedBy[Them][ALL_PIECES]);
653 // Find all squares which are at most three squares behind some friendly pawn
654 Bitboard behind = pos.pieces(Us, PAWN);
655 behind |= (Us == WHITE ? behind >> 8 : behind << 8);
656 behind |= (Us == WHITE ? behind >> 16 : behind << 16);
658 // Since SpaceMask[Us] is fully on our half of the board
659 assert(unsigned(safe >> (Us == WHITE ? 32 : 0)) == 0);
661 // Count safe + (behind & safe) with a single popcount
662 int bonus = popcount<Full>((Us == WHITE ? safe << 32 : safe >> 32) | (behind & safe));
663 int weight = pos.count<KNIGHT>(Us) + pos.count<BISHOP>(Us)
664 + pos.count<KNIGHT>(Them) + pos.count<BISHOP>(Them);
666 return make_score(bonus * weight * weight, 0);
670 // do_evaluate() is the evaluation entry point, called directly from evaluate()
673 Value do_evaluate(const Position& pos) {
675 assert(!pos.checkers());
678 Score score, mobility[2] = { SCORE_ZERO, SCORE_ZERO };
680 // Initialize score by reading the incrementally updated scores included
681 // in the position object (material + piece square tables).
682 // Score is computed from the point of view of white.
683 score = pos.psq_score();
685 // Probe the material hash table
686 ei.mi = Material::probe(pos);
687 score += ei.mi->imbalance();
689 // If we have a specialized evaluation function for the current material
690 // configuration, call it and return.
691 if (ei.mi->specialized_eval_exists())
692 return ei.mi->evaluate(pos);
694 // Probe the pawn hash table
695 ei.pi = Pawns::probe(pos);
696 score += ei.pi->pawns_score() * Weights[PawnStructure];
698 // Initialize attack and king safety bitboards
699 init_eval_info<WHITE>(pos, ei);
700 init_eval_info<BLACK>(pos, ei);
702 ei.attackedBy[WHITE][ALL_PIECES] |= ei.attackedBy[WHITE][KING];
703 ei.attackedBy[BLACK][ALL_PIECES] |= ei.attackedBy[BLACK][KING];
705 // Pawns blocked or on ranks 2 and 3. Will be excluded from the mobility area
706 Bitboard blockedPawns[] = {
707 pos.pieces(WHITE, PAWN) & (shift_bb<DELTA_S>(pos.pieces()) | Rank2BB | Rank3BB),
708 pos.pieces(BLACK, PAWN) & (shift_bb<DELTA_N>(pos.pieces()) | Rank7BB | Rank6BB)
711 // Do not include in mobility squares protected by enemy pawns, or occupied
712 // by our blocked pawns or king.
713 Bitboard mobilityArea[] = {
714 ~(ei.attackedBy[BLACK][PAWN] | blockedPawns[WHITE] | pos.square<KING>(WHITE)),
715 ~(ei.attackedBy[WHITE][PAWN] | blockedPawns[BLACK] | pos.square<KING>(BLACK))
718 // Evaluate pieces and mobility
719 score += evaluate_pieces<KNIGHT, WHITE, Trace>(pos, ei, mobility, mobilityArea);
720 score += (mobility[WHITE] - mobility[BLACK]) * Weights[Mobility];
722 // Evaluate kings after all other pieces because we need complete attack
723 // information when computing the king safety evaluation.
724 score += evaluate_king<WHITE, Trace>(pos, ei)
725 - evaluate_king<BLACK, Trace>(pos, ei);
727 // Evaluate tactical threats, we need full attack information including king
728 score += evaluate_threats<WHITE, Trace>(pos, ei)
729 - evaluate_threats<BLACK, Trace>(pos, ei);
731 // Evaluate passed pawns, we need full attack information including king
732 score += evaluate_passed_pawns<WHITE, Trace>(pos, ei)
733 - evaluate_passed_pawns<BLACK, Trace>(pos, ei);
735 // If both sides have only pawns, score for potential unstoppable pawns
736 if (!pos.non_pawn_material(WHITE) && !pos.non_pawn_material(BLACK))
739 if ((b = ei.pi->passed_pawns(WHITE)) != 0)
740 score += int(relative_rank(WHITE, frontmost_sq(WHITE, b))) * Unstoppable;
742 if ((b = ei.pi->passed_pawns(BLACK)) != 0)
743 score -= int(relative_rank(BLACK, frontmost_sq(BLACK, b))) * Unstoppable;
746 // Evaluate space for both sides, only during opening
747 if (pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK) >= 11756)
748 score += (evaluate_space<WHITE>(pos, ei) - evaluate_space<BLACK>(pos, ei)) * Weights[Space];
750 // Scale winning side if position is more drawish than it appears
751 Color strongSide = eg_value(score) > VALUE_DRAW ? WHITE : BLACK;
752 ScaleFactor sf = ei.mi->scale_factor(pos, strongSide);
754 // If we don't already have an unusual scale factor, check for certain
755 // types of endgames, and use a lower scale for those.
756 if ( ei.mi->game_phase() < PHASE_MIDGAME
757 && (sf == SCALE_FACTOR_NORMAL || sf == SCALE_FACTOR_ONEPAWN))
759 if (pos.opposite_bishops())
761 // Endgame with opposite-colored bishops and no other pieces (ignoring pawns)
762 // is almost a draw, in case of KBP vs KB is even more a draw.
763 if ( pos.non_pawn_material(WHITE) == BishopValueMg
764 && pos.non_pawn_material(BLACK) == BishopValueMg)
765 sf = more_than_one(pos.pieces(PAWN)) ? ScaleFactor(32) : ScaleFactor(8);
767 // Endgame with opposite-colored bishops, but also other pieces. Still
768 // a bit drawish, but not as drawish as with only the two bishops.
770 sf = ScaleFactor(50 * sf / SCALE_FACTOR_NORMAL);
772 // Endings where weaker side can place his king in front of the opponent's
773 // pawns are drawish.
774 else if ( abs(eg_value(score)) <= BishopValueEg
775 && ei.pi->pawn_span(strongSide) <= 1
776 && !pos.pawn_passed(~strongSide, pos.square<KING>(~strongSide)))
777 sf = ei.pi->pawn_span(strongSide) ? ScaleFactor(56) : ScaleFactor(38);
780 // Interpolate between a middlegame and a (scaled by 'sf') endgame score
781 Value v = mg_value(score) * int(ei.mi->game_phase())
782 + eg_value(score) * int(PHASE_MIDGAME - ei.mi->game_phase()) * sf / SCALE_FACTOR_NORMAL;
784 v /= int(PHASE_MIDGAME);
786 // In case of tracing add all single evaluation terms for both white and black
789 Tracing::write(Tracing::MATERIAL, pos.psq_score());
790 Tracing::write(Tracing::IMBALANCE, ei.mi->imbalance());
791 Tracing::write(PAWN, ei.pi->pawns_score());
792 Tracing::write(Tracing::MOBILITY, mobility[WHITE] * Weights[Mobility]
793 , mobility[BLACK] * Weights[Mobility]);
794 Tracing::write(Tracing::SPACE, evaluate_space<WHITE>(pos, ei) * Weights[Space]
795 , evaluate_space<BLACK>(pos, ei) * Weights[Space]);
796 Tracing::write(Tracing::TOTAL, score);
799 return (pos.side_to_move() == WHITE ? v : -v) + Eval::Tempo; // Side to move point of view
805 double Tracing::to_cp(Value v) { return double(v) / PawnValueEg; }
807 void Tracing::write(int idx, Color c, Score s) { scores[c][idx] = s; }
809 void Tracing::write(int idx, Score w, Score b) {
810 scores[WHITE][idx] = w, scores[BLACK][idx] = b;
813 std::ostream& Tracing::operator<<(std::ostream& os, Term t) {
815 double wScore[] = { to_cp(mg_value(scores[WHITE][t])), to_cp(eg_value(scores[WHITE][t])) };
816 double bScore[] = { to_cp(mg_value(scores[BLACK][t])), to_cp(eg_value(scores[BLACK][t])) };
818 if (t == MATERIAL || t == IMBALANCE || t == Term(PAWN) || t == TOTAL)
819 os << " --- --- | --- --- | ";
821 os << std::setw(5) << wScore[MG] << " " << std::setw(5) << wScore[EG] << " | "
822 << std::setw(5) << bScore[MG] << " " << std::setw(5) << bScore[EG] << " | ";
824 os << std::setw(5) << wScore[MG] - bScore[MG] << " "
825 << std::setw(5) << wScore[EG] - bScore[EG] << " \n";
830 std::string Tracing::do_trace(const Position& pos) {
832 std::memset(scores, 0, sizeof(scores));
834 Value v = do_evaluate<true>(pos);
835 v = pos.side_to_move() == WHITE ? v : -v; // White's point of view
837 std::stringstream ss;
838 ss << std::showpoint << std::noshowpos << std::fixed << std::setprecision(2)
839 << " Eval term | White | Black | Total \n"
840 << " | MG EG | MG EG | MG EG \n"
841 << "----------------+-------------+-------------+-------------\n"
842 << " Material | " << Term(MATERIAL)
843 << " Imbalance | " << Term(IMBALANCE)
844 << " Pawns | " << Term(PAWN)
845 << " Knights | " << Term(KNIGHT)
846 << " Bishop | " << Term(BISHOP)
847 << " Rooks | " << Term(ROOK)
848 << " Queens | " << Term(QUEEN)
849 << " Mobility | " << Term(MOBILITY)
850 << " King safety | " << Term(KING)
851 << " Threats | " << Term(THREAT)
852 << " Passed pawns | " << Term(PASSED)
853 << " Space | " << Term(SPACE)
854 << "----------------+-------------+-------------+-------------\n"
855 << " Total | " << Term(TOTAL);
857 ss << "\nTotal Evaluation: " << to_cp(v) << " (white side)\n";
867 /// evaluate() is the main evaluation function. It returns a static evaluation
868 /// of the position always from the point of view of the side to move.
870 Value evaluate(const Position& pos) {
871 return do_evaluate<false>(pos);
875 /// trace() is like evaluate(), but instead of returning a value, it returns
876 /// a string (suitable for outputting to stdout) that contains the detailed
877 /// descriptions and values of each evaluation term. It's mainly used for
879 std::string trace(const Position& pos) {
880 return Tracing::do_trace(pos);
884 /// init() computes evaluation weights, usually at startup
888 const int MaxSlope = 8700;
889 const int Peak = 1280000;
892 for (int i = 0; i < 400; ++i)
894 t = std::min(Peak, std::min(i * i * 27, t + MaxSlope));
895 KingDanger[i] = make_score(t / 1000, 0) * Weights[KingSafety];