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 bishops
128 // 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 const Score ThreatenedByHangingPawn = S(40, 60);
151 // Assorted bonuses and penalties used by evaluation
152 const Score KingOnOne = S( 2, 58);
153 const Score KingOnMany = S( 6,125);
154 const Score RookOnPawn = S( 7, 27);
155 const Score RookOnOpenFile = S(43, 21);
156 const Score RookOnSemiOpenFile = S(19, 10);
157 const Score BishopPawns = S( 8, 12);
158 const Score MinorBehindPawn = S(16, 0);
159 const Score TrappedRook = S(92, 0);
160 const Score Unstoppable = S( 0, 20);
161 const Score Hanging = S(31, 26);
162 const Score PawnAttackThreat = S(20, 20);
163 const Score PawnSafePush = S( 5, 5);
165 // Penalty for a bishop on a1/h1 (a8/h8 for black) which is trapped by
166 // a friendly pawn on b2/g2 (b7/g7 for black). This can obviously only
167 // happen in Chess960 games.
168 const Score TrappedBishopA1H1 = S(50, 50);
173 // SpaceMask[Color] contains the area of the board which is considered
174 // by the space evaluation. In the middlegame, each side is given a bonus
175 // based on how many squares inside this area are safe and available for
176 // friendly minor pieces.
177 const Bitboard SpaceMask[COLOR_NB] = {
178 (FileCBB | FileDBB | FileEBB | FileFBB) & (Rank2BB | Rank3BB | Rank4BB),
179 (FileCBB | FileDBB | FileEBB | FileFBB) & (Rank7BB | Rank6BB | Rank5BB)
182 // King danger constants and variables. The king danger scores are looked-up
183 // in KingDanger[]. Various little "meta-bonuses" measuring the strength
184 // of the enemy attack are added up into an integer, which is used as an
185 // index to KingDanger[].
186 Score KingDanger[512];
188 // KingAttackWeights[PieceType] contains king attack weights by piece type
189 const int KingAttackWeights[PIECE_TYPE_NB] = { 0, 0, 7, 5, 4, 1 };
191 // Penalties for enemy's safe checks
192 const int QueenContactCheck = 89;
193 const int RookContactCheck = 71;
194 const int QueenCheck = 50;
195 const int RookCheck = 37;
196 const int BishopCheck = 6;
197 const int KnightCheck = 14;
200 // init_eval_info() initializes king bitboards for given color adding
201 // pawn attacks. To be done at the beginning of the evaluation.
204 void init_eval_info(const Position& pos, EvalInfo& ei) {
206 const Color Them = (Us == WHITE ? BLACK : WHITE);
207 const Square Down = (Us == WHITE ? DELTA_S : DELTA_N);
209 ei.pinnedPieces[Us] = pos.pinned_pieces(Us);
210 ei.attackedBy[Us][ALL_PIECES] = ei.attackedBy[Us][PAWN] = ei.pi->pawn_attacks(Us);
211 Bitboard b = ei.attackedBy[Them][KING] = pos.attacks_from<KING>(pos.king_square(Them));
213 // Init king safety tables only if we are going to use them
214 if (pos.non_pawn_material(Us) >= QueenValueMg)
216 ei.kingRing[Them] = b | shift_bb<Down>(b);
217 b &= ei.attackedBy[Us][PAWN];
218 ei.kingAttackersCount[Us] = b ? popcount<Max15>(b) : 0;
219 ei.kingAdjacentZoneAttacksCount[Us] = ei.kingAttackersWeight[Us] = 0;
222 ei.kingRing[Them] = ei.kingAttackersCount[Us] = 0;
226 // evaluate_pieces() assigns bonuses and penalties to the pieces of a given color
228 template<PieceType Pt, Color Us, bool Trace>
229 Score evaluate_pieces(const Position& pos, EvalInfo& ei, Score* mobility, Bitboard* mobilityArea) {
233 Score score = SCORE_ZERO;
235 const PieceType NextPt = (Us == WHITE ? Pt : PieceType(Pt + 1));
236 const Color Them = (Us == WHITE ? BLACK : WHITE);
237 const Square* pl = pos.list<Pt>(Us);
239 ei.attackedBy[Us][Pt] = 0;
241 while ((s = *pl++) != SQ_NONE)
243 // Find attacked squares, including x-ray attacks for bishops and rooks
244 b = Pt == BISHOP ? attacks_bb<BISHOP>(s, pos.pieces() ^ pos.pieces(Us, QUEEN))
245 : Pt == ROOK ? attacks_bb< ROOK>(s, pos.pieces() ^ pos.pieces(Us, ROOK, QUEEN))
246 : pos.attacks_from<Pt>(s);
248 if (ei.pinnedPieces[Us] & s)
249 b &= LineBB[pos.king_square(Us)][s];
251 ei.attackedBy[Us][ALL_PIECES] |= ei.attackedBy[Us][Pt] |= b;
253 if (b & ei.kingRing[Them])
255 ei.kingAttackersCount[Us]++;
256 ei.kingAttackersWeight[Us] += KingAttackWeights[Pt];
257 Bitboard bb = b & ei.attackedBy[Them][KING];
259 ei.kingAdjacentZoneAttacksCount[Us] += popcount<Max15>(bb);
263 b &= ~( ei.attackedBy[Them][KNIGHT]
264 | ei.attackedBy[Them][BISHOP]
265 | ei.attackedBy[Them][ROOK]);
267 int mob = popcount<Pt == QUEEN ? Full : Max15>(b & mobilityArea[Us]);
269 mobility[Us] += MobilityBonus[Pt][mob];
271 if (Pt == BISHOP || Pt == KNIGHT)
273 // Bonus for outpost square
274 if ( relative_rank(Us, s) >= RANK_4
275 && !(pos.pieces(Them, PAWN) & pawn_attack_span(Us, s)))
276 score += Outpost[Pt == BISHOP][!!(ei.attackedBy[Us][PAWN] & s)];
278 // Bonus when behind a pawn
279 if ( relative_rank(Us, s) < RANK_5
280 && (pos.pieces(PAWN) & (s + pawn_push(Us))))
281 score += MinorBehindPawn;
283 // Penalty for pawns on same color square of bishop
285 score -= BishopPawns * ei.pi->pawns_on_same_color_squares(Us, s);
287 // An important Chess960 pattern: A cornered bishop blocked by a friendly
288 // pawn diagonally in front of it is a very serious problem, especially
289 // when that pawn is also blocked.
292 && (s == relative_square(Us, SQ_A1) || s == relative_square(Us, SQ_H1)))
294 Square d = pawn_push(Us) + (file_of(s) == FILE_A ? DELTA_E : DELTA_W);
295 if (pos.piece_on(s + d) == make_piece(Us, PAWN))
296 score -= !pos.empty(s + d + pawn_push(Us)) ? TrappedBishopA1H1 * 4
297 : pos.piece_on(s + d + d) == make_piece(Us, PAWN) ? TrappedBishopA1H1 * 2
304 // Bonus for aligning with enemy pawns on the same rank/file
305 if (relative_rank(Us, s) >= RANK_5)
307 Bitboard alignedPawns = pos.pieces(Them, PAWN) & PseudoAttacks[ROOK][s];
309 score += popcount<Max15>(alignedPawns) * RookOnPawn;
312 // Bonus when on an open or semi-open file
313 if (ei.pi->semiopen_file(Us, file_of(s)))
314 score += ei.pi->semiopen_file(Them, file_of(s)) ? RookOnOpenFile : RookOnSemiOpenFile;
316 // Penalize when trapped by the king, even more if king cannot castle
317 if (mob <= 3 && !ei.pi->semiopen_file(Us, file_of(s)))
319 Square ksq = pos.king_square(Us);
321 if ( ((file_of(ksq) < FILE_E) == (file_of(s) < file_of(ksq)))
322 && (rank_of(ksq) == rank_of(s) || relative_rank(Us, ksq) == RANK_1)
323 && !ei.pi->semiopen_side(Us, file_of(ksq), file_of(s) < file_of(ksq)))
324 score -= (TrappedRook - make_score(mob * 22, 0)) * (1 + !pos.can_castle(Us));
330 Tracing::write(Pt, Us, score);
332 // Recursively call evaluate_pieces() of next piece type until KING excluded
333 return score - evaluate_pieces<NextPt, Them, Trace>(pos, ei, mobility, mobilityArea);
337 Score evaluate_pieces<KING, WHITE, false>(const Position&, EvalInfo&, Score*, Bitboard*) { return SCORE_ZERO; }
339 Score evaluate_pieces<KING, WHITE, true>(const Position&, EvalInfo&, Score*, Bitboard*) { return SCORE_ZERO; }
342 // evaluate_king() assigns bonuses and penalties to a king of a given color
344 template<Color Us, bool Trace>
345 Score evaluate_king(const Position& pos, const EvalInfo& ei) {
347 const Color Them = (Us == WHITE ? BLACK : WHITE);
349 Bitboard undefended, b, b1, b2, safe;
351 const Square ksq = pos.king_square(Us);
353 // King shelter and enemy pawns storm
354 Score score = ei.pi->king_safety<Us>(pos, ksq);
356 // Main king safety evaluation
357 if (ei.kingAttackersCount[Them])
359 // Find the attacked squares around the king which have no defenders
360 // apart from the king itself
361 undefended = ei.attackedBy[Them][ALL_PIECES]
362 & ei.attackedBy[Us][KING]
363 & ~( ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
364 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
365 | ei.attackedBy[Us][QUEEN]);
367 // Initialize the 'attackUnits' variable, which is used later on as an
368 // index into the KingDanger[] array. The initial value is based on the
369 // number and types of the enemy's attacking pieces, the number of
370 // attacked and undefended squares around our king and the quality of
371 // the pawn shelter (current 'score' value).
372 attackUnits = std::min(74, ei.kingAttackersCount[Them] * ei.kingAttackersWeight[Them])
373 + 8 * ei.kingAdjacentZoneAttacksCount[Them]
374 + 25 * popcount<Max15>(undefended)
375 + 11 * (ei.pinnedPieces[Us] != 0)
376 - mg_value(score) / 8
377 - !pos.count<QUEEN>(Them) * 60;
379 // Analyse the enemy's safe queen contact checks. Firstly, find the
380 // undefended squares around the king reachable by the enemy queen...
381 b = undefended & ei.attackedBy[Them][QUEEN] & ~pos.pieces(Them);
384 // ...and then remove squares not supported by another enemy piece
385 b &= ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
386 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][ROOK];
389 attackUnits += QueenContactCheck * popcount<Max15>(b);
392 // Analyse the enemy's safe rook contact checks. Firstly, find the
393 // undefended squares around the king reachable by the enemy rooks...
394 b = undefended & ei.attackedBy[Them][ROOK] & ~pos.pieces(Them);
396 // Consider only squares where the enemy's rook gives check
397 b &= PseudoAttacks[ROOK][ksq];
401 // ...and then remove squares not supported by another enemy piece
402 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
403 | ei.attackedBy[Them][BISHOP]);
406 attackUnits += RookContactCheck * popcount<Max15>(b);
409 // Analyse the enemy's safe distance checks for sliders and knights
410 safe = ~(ei.attackedBy[Us][ALL_PIECES] | pos.pieces(Them));
412 b1 = pos.attacks_from<ROOK >(ksq) & safe;
413 b2 = pos.attacks_from<BISHOP>(ksq) & safe;
415 // Enemy queen safe checks
416 b = (b1 | b2) & ei.attackedBy[Them][QUEEN];
418 attackUnits += QueenCheck * popcount<Max15>(b);
420 // Enemy rooks safe checks
421 b = b1 & ei.attackedBy[Them][ROOK];
423 attackUnits += RookCheck * popcount<Max15>(b);
425 // Enemy bishops safe checks
426 b = b2 & ei.attackedBy[Them][BISHOP];
428 attackUnits += BishopCheck * popcount<Max15>(b);
430 // Enemy knights safe checks
431 b = pos.attacks_from<KNIGHT>(ksq) & ei.attackedBy[Them][KNIGHT] & safe;
433 attackUnits += KnightCheck * popcount<Max15>(b);
435 // Finally, extract the king danger score from the KingDanger[]
436 // array and subtract the score from evaluation.
437 score -= KingDanger[std::max(std::min(attackUnits, 399), 0)];
441 Tracing::write(KING, Us, score);
447 // evaluate_threats() assigns bonuses according to the type of attacking piece
448 // and the type of attacked one.
450 template<Color Us, bool Trace>
451 Score evaluate_threats(const Position& pos, const EvalInfo& ei) {
453 const Color Them = (Us == WHITE ? BLACK : WHITE);
454 const Square Up = (Us == WHITE ? DELTA_N : DELTA_S);
455 const Square Left = (Us == WHITE ? DELTA_NW : DELTA_SE);
456 const Square Right = (Us == WHITE ? DELTA_NE : DELTA_SW);
457 const Bitboard TRank2BB = (Us == WHITE ? Rank2BB : Rank7BB);
458 const Bitboard TRank7BB = (Us == WHITE ? Rank7BB : Rank2BB);
460 enum { Defended, Weak };
461 enum { Minor, Major };
463 Bitboard b, weak, defended, safeThreats;
464 Score score = SCORE_ZERO;
466 // Non-pawn enemies attacked by a pawn
467 weak = (pos.pieces(Them) ^ pos.pieces(Them, PAWN)) & ei.attackedBy[Us][PAWN];
471 b = pos.pieces(Us, PAWN) & ( ~ei.attackedBy[Them][ALL_PIECES]
472 | ei.attackedBy[Us][ALL_PIECES]);
474 safeThreats = (shift_bb<Right>(b) | shift_bb<Left>(b)) & weak;
476 if (weak ^ safeThreats)
477 score += ThreatenedByHangingPawn;
480 score += ThreatenedByPawn[type_of(pos.piece_on(pop_lsb(&safeThreats)))];
483 // Non-pawn enemies defended by a pawn
484 defended = (pos.pieces(Them) ^ pos.pieces(Them, PAWN)) & ei.attackedBy[Them][PAWN];
486 // Add a bonus according to the kind of attacking pieces
489 b = defended & (ei.attackedBy[Us][KNIGHT] | ei.attackedBy[Us][BISHOP]);
491 score += Threat[Defended][Minor][type_of(pos.piece_on(pop_lsb(&b)))];
493 b = defended & (ei.attackedBy[Us][ROOK]);
495 score += Threat[Defended][Major][type_of(pos.piece_on(pop_lsb(&b)))];
498 // Enemies not defended by a pawn and under our attack
499 weak = pos.pieces(Them)
500 & ~ei.attackedBy[Them][PAWN]
501 & ei.attackedBy[Us][ALL_PIECES];
503 // Add a bonus according to the kind of attacking pieces
506 b = weak & (ei.attackedBy[Us][KNIGHT] | ei.attackedBy[Us][BISHOP]);
508 score += Threat[Weak][Minor][type_of(pos.piece_on(pop_lsb(&b)))];
510 b = weak & (ei.attackedBy[Us][ROOK] | ei.attackedBy[Us][QUEEN]);
512 score += Threat[Weak][Major][type_of(pos.piece_on(pop_lsb(&b)))];
514 b = weak & ~ei.attackedBy[Them][ALL_PIECES];
516 score += Hanging * popcount<Max15>(b);
518 b = weak & ei.attackedBy[Us][KING];
520 score += more_than_one(b) ? KingOnMany : KingOnOne;
523 // Add a small bonus for safe pawn pushes
524 b = pos.pieces(Us, PAWN) & ~TRank7BB;
525 b = shift_bb<Up>(b | (shift_bb<Up>(b & TRank2BB) & ~pos.pieces()));
528 & ~ei.attackedBy[Them][PAWN]
529 & (ei.attackedBy[Us][ALL_PIECES] | ~ei.attackedBy[Them][ALL_PIECES]);
532 score += popcount<Full>(b) * PawnSafePush;
534 // Add another bonus if the pawn push attacks an enemy piece
535 b = (shift_bb<Left>(b) | shift_bb<Right>(b))
537 & ~ei.attackedBy[Us][PAWN];
540 score += popcount<Max15>(b) * PawnAttackThreat;
543 Tracing::write(Tracing::THREAT, Us, score);
549 // evaluate_passed_pawns() evaluates the passed pawns of the given color
551 template<Color Us, bool Trace>
552 Score evaluate_passed_pawns(const Position& pos, const EvalInfo& ei) {
554 const Color Them = (Us == WHITE ? BLACK : WHITE);
556 Bitboard b, squaresToQueen, defendedSquares, unsafeSquares;
557 Score score = SCORE_ZERO;
559 b = ei.pi->passed_pawns(Us);
563 Square s = pop_lsb(&b);
565 assert(pos.pawn_passed(Us, s));
567 int r = relative_rank(Us, s) - RANK_2;
568 int rr = r * (r - 1);
570 // Base bonus based on rank
571 Value mbonus = Value(17 * rr), ebonus = Value(7 * (rr + r + 1));
575 Square blockSq = s + pawn_push(Us);
577 // Adjust bonus based on the king's proximity
578 ebonus += distance(pos.king_square(Them), blockSq) * 5 * rr
579 - distance(pos.king_square(Us ), blockSq) * 2 * rr;
581 // If blockSq is not the queening square then consider also a second push
582 if (relative_rank(Us, blockSq) != RANK_8)
583 ebonus -= distance(pos.king_square(Us), blockSq + pawn_push(Us)) * rr;
585 // If the pawn is free to advance, then increase the bonus
586 if (pos.empty(blockSq))
588 // If there is a rook or queen attacking/defending the pawn from behind,
589 // consider all the squaresToQueen. Otherwise consider only the squares
590 // in the pawn's path attacked or occupied by the enemy.
591 defendedSquares = unsafeSquares = squaresToQueen = forward_bb(Us, s);
593 Bitboard bb = forward_bb(Them, s) & pos.pieces(ROOK, QUEEN) & pos.attacks_from<ROOK>(s);
595 if (!(pos.pieces(Us) & bb))
596 defendedSquares &= ei.attackedBy[Us][ALL_PIECES];
598 if (!(pos.pieces(Them) & bb))
599 unsafeSquares &= ei.attackedBy[Them][ALL_PIECES] | pos.pieces(Them);
601 // If there aren't any enemy attacks, assign a big bonus. Otherwise
602 // assign a smaller bonus if the block square isn't attacked.
603 int k = !unsafeSquares ? 15 : !(unsafeSquares & blockSq) ? 9 : 0;
605 // If the path to queen is fully defended, assign a big bonus.
606 // Otherwise assign a smaller bonus if the block square is defended.
607 if (defendedSquares == squaresToQueen)
610 else if (defendedSquares & blockSq)
613 mbonus += k * rr, ebonus += k * rr;
615 else if (pos.pieces(Us) & blockSq)
616 mbonus += rr * 3 + r * 2 + 3, ebonus += rr + r * 2;
619 if (pos.count<PAWN>(Us) < pos.count<PAWN>(Them))
620 ebonus += ebonus / 4;
622 score += make_score(mbonus, ebonus);
626 Tracing::write(Tracing::PASSED, Us, score * Weights[PassedPawns]);
628 // Add the scores to the middlegame and endgame eval
629 return score * Weights[PassedPawns];
633 // evaluate_space() computes the space evaluation for a given side. The
634 // space evaluation is a simple bonus based on the number of safe squares
635 // available for minor pieces on the central four files on ranks 2--4. Safe
636 // squares one, two or three squares behind a friendly pawn are counted
637 // twice. Finally, the space bonus is multiplied by a weight. The aim is to
638 // improve play on game opening.
640 Score evaluate_space(const Position& pos, const EvalInfo& ei) {
642 const Color Them = (Us == WHITE ? BLACK : WHITE);
644 // Find the safe squares for our pieces inside the area defined by
645 // SpaceMask[]. A square is unsafe if it is attacked by an enemy
646 // pawn, or if it is undefended and attacked by an enemy piece.
647 Bitboard safe = SpaceMask[Us]
648 & ~pos.pieces(Us, PAWN)
649 & ~ei.attackedBy[Them][PAWN]
650 & (ei.attackedBy[Us][ALL_PIECES] | ~ei.attackedBy[Them][ALL_PIECES]);
652 // Find all squares which are at most three squares behind some friendly pawn
653 Bitboard behind = pos.pieces(Us, PAWN);
654 behind |= (Us == WHITE ? behind >> 8 : behind << 8);
655 behind |= (Us == WHITE ? behind >> 16 : behind << 16);
657 // Since SpaceMask[Us] is fully on our half of the board
658 assert(unsigned(safe >> (Us == WHITE ? 32 : 0)) == 0);
660 // Count safe + (behind & safe) with a single popcount
661 int bonus = popcount<Full>((Us == WHITE ? safe << 32 : safe >> 32) | (behind & safe));
662 int weight = pos.count<KNIGHT>(Us) + pos.count<BISHOP>(Us)
663 + pos.count<KNIGHT>(Them) + pos.count<BISHOP>(Them);
665 return make_score(bonus * weight * weight, 0);
669 // do_evaluate() is the evaluation entry point, called directly from evaluate()
672 Value do_evaluate(const Position& pos) {
674 assert(!pos.checkers());
677 Score score, mobility[2] = { SCORE_ZERO, SCORE_ZERO };
679 // Initialize score by reading the incrementally updated scores included
680 // in the position object (material + piece square tables).
681 // Score is computed from the point of view of white.
682 score = pos.psq_score();
684 // Probe the material hash table
685 ei.mi = Material::probe(pos);
686 score += ei.mi->imbalance();
688 // If we have a specialized evaluation function for the current material
689 // configuration, call it and return.
690 if (ei.mi->specialized_eval_exists())
691 return ei.mi->evaluate(pos);
693 // Probe the pawn hash table
694 ei.pi = Pawns::probe(pos);
695 score += ei.pi->pawns_score() * Weights[PawnStructure];
697 // Initialize attack and king safety bitboards
698 init_eval_info<WHITE>(pos, ei);
699 init_eval_info<BLACK>(pos, ei);
701 ei.attackedBy[WHITE][ALL_PIECES] |= ei.attackedBy[WHITE][KING];
702 ei.attackedBy[BLACK][ALL_PIECES] |= ei.attackedBy[BLACK][KING];
704 // Do not include in mobility squares protected by enemy pawns or occupied by our pawns or king
705 Bitboard mobilityArea[] = { ~(ei.attackedBy[BLACK][PAWN] | pos.pieces(WHITE, PAWN, KING)),
706 ~(ei.attackedBy[WHITE][PAWN] | pos.pieces(BLACK, PAWN, KING)) };
708 // Evaluate pieces and mobility
709 score += evaluate_pieces<KNIGHT, WHITE, Trace>(pos, ei, mobility, mobilityArea);
710 score += (mobility[WHITE] - mobility[BLACK]) * Weights[Mobility];
712 // Evaluate kings after all other pieces because we need complete attack
713 // information when computing the king safety evaluation.
714 score += evaluate_king<WHITE, Trace>(pos, ei)
715 - evaluate_king<BLACK, Trace>(pos, ei);
717 // Evaluate tactical threats, we need full attack information including king
718 score += evaluate_threats<WHITE, Trace>(pos, ei)
719 - evaluate_threats<BLACK, Trace>(pos, ei);
721 // Evaluate passed pawns, we need full attack information including king
722 score += evaluate_passed_pawns<WHITE, Trace>(pos, ei)
723 - evaluate_passed_pawns<BLACK, Trace>(pos, ei);
725 // If both sides have only pawns, score for potential unstoppable pawns
726 if (!pos.non_pawn_material(WHITE) && !pos.non_pawn_material(BLACK))
729 if ((b = ei.pi->passed_pawns(WHITE)) != 0)
730 score += int(relative_rank(WHITE, frontmost_sq(WHITE, b))) * Unstoppable;
732 if ((b = ei.pi->passed_pawns(BLACK)) != 0)
733 score -= int(relative_rank(BLACK, frontmost_sq(BLACK, b))) * Unstoppable;
736 // Evaluate space for both sides, only during opening
737 if (pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK) >= 11756)
738 score += (evaluate_space<WHITE>(pos, ei) - evaluate_space<BLACK>(pos, ei)) * Weights[Space];
740 // Scale winning side if position is more drawish than it appears
741 Color strongSide = eg_value(score) > VALUE_DRAW ? WHITE : BLACK;
742 ScaleFactor sf = ei.mi->scale_factor(pos, strongSide);
744 // If we don't already have an unusual scale factor, check for certain
745 // types of endgames, and use a lower scale for those.
746 if ( ei.mi->game_phase() < PHASE_MIDGAME
747 && (sf == SCALE_FACTOR_NORMAL || sf == SCALE_FACTOR_ONEPAWN))
749 if (pos.opposite_bishops())
751 // Endgame with opposite-colored bishops and no other pieces (ignoring pawns)
752 // is almost a draw, in case of KBP vs KB is even more a draw.
753 if ( pos.non_pawn_material(WHITE) == BishopValueMg
754 && pos.non_pawn_material(BLACK) == BishopValueMg)
755 sf = more_than_one(pos.pieces(PAWN)) ? ScaleFactor(32) : ScaleFactor(8);
757 // Endgame with opposite-colored bishops, but also other pieces. Still
758 // a bit drawish, but not as drawish as with only the two bishops.
760 sf = ScaleFactor(50 * sf / SCALE_FACTOR_NORMAL);
762 // Endings where weaker side can place his king in front of the opponent's
763 // pawns are drawish.
764 else if ( abs(eg_value(score)) <= BishopValueEg
765 && ei.pi->pawn_span(strongSide) <= 1
766 && !pos.pawn_passed(~strongSide, pos.king_square(~strongSide)))
767 sf = ei.pi->pawn_span(strongSide) ? ScaleFactor(56) : ScaleFactor(38);
770 // Interpolate between a middlegame and a (scaled by 'sf') endgame score
771 Value v = mg_value(score) * int(ei.mi->game_phase())
772 + eg_value(score) * int(PHASE_MIDGAME - ei.mi->game_phase()) * sf / SCALE_FACTOR_NORMAL;
774 v /= int(PHASE_MIDGAME);
776 // In case of tracing add all single evaluation terms for both white and black
779 Tracing::write(Tracing::MATERIAL, pos.psq_score());
780 Tracing::write(Tracing::IMBALANCE, ei.mi->imbalance());
781 Tracing::write(PAWN, ei.pi->pawns_score());
782 Tracing::write(Tracing::MOBILITY, mobility[WHITE] * Weights[Mobility]
783 , mobility[BLACK] * Weights[Mobility]);
784 Tracing::write(Tracing::SPACE, evaluate_space<WHITE>(pos, ei) * Weights[Space]
785 , evaluate_space<BLACK>(pos, ei) * Weights[Space]);
786 Tracing::write(Tracing::TOTAL, score);
789 return (pos.side_to_move() == WHITE ? v : -v) + Eval::Tempo; // Side to move point of view
795 double Tracing::to_cp(Value v) { return double(v) / PawnValueEg; }
797 void Tracing::write(int idx, Color c, Score s) { scores[c][idx] = s; }
799 void Tracing::write(int idx, Score w, Score b) {
800 scores[WHITE][idx] = w, scores[BLACK][idx] = b;
803 std::ostream& Tracing::operator<<(std::ostream& os, Term t) {
805 double wScore[] = { to_cp(mg_value(scores[WHITE][t])), to_cp(eg_value(scores[WHITE][t])) };
806 double bScore[] = { to_cp(mg_value(scores[BLACK][t])), to_cp(eg_value(scores[BLACK][t])) };
808 if (t == MATERIAL || t == IMBALANCE || t == Term(PAWN) || t == TOTAL)
809 os << " --- --- | --- --- | ";
811 os << std::setw(5) << wScore[MG] << " " << std::setw(5) << wScore[EG] << " | "
812 << std::setw(5) << bScore[MG] << " " << std::setw(5) << bScore[EG] << " | ";
814 os << std::setw(5) << wScore[MG] - bScore[MG] << " "
815 << std::setw(5) << wScore[EG] - bScore[EG] << " \n";
820 std::string Tracing::do_trace(const Position& pos) {
822 std::memset(scores, 0, sizeof(scores));
824 Value v = do_evaluate<true>(pos);
825 v = pos.side_to_move() == WHITE ? v : -v; // White's point of view
827 std::stringstream ss;
828 ss << std::showpoint << std::noshowpos << std::fixed << std::setprecision(2)
829 << " Eval term | White | Black | Total \n"
830 << " | MG EG | MG EG | MG EG \n"
831 << "----------------+-------------+-------------+-------------\n"
832 << " Material | " << Term(MATERIAL)
833 << " Imbalance | " << Term(IMBALANCE)
834 << " Pawns | " << Term(PAWN)
835 << " Knights | " << Term(KNIGHT)
836 << " Bishop | " << Term(BISHOP)
837 << " Rooks | " << Term(ROOK)
838 << " Queens | " << Term(QUEEN)
839 << " Mobility | " << Term(MOBILITY)
840 << " King safety | " << Term(KING)
841 << " Threats | " << Term(THREAT)
842 << " Passed pawns | " << Term(PASSED)
843 << " Space | " << Term(SPACE)
844 << "----------------+-------------+-------------+-------------\n"
845 << " Total | " << Term(TOTAL);
847 ss << "\nTotal Evaluation: " << to_cp(v) << " (white side)\n";
857 /// evaluate() is the main evaluation function. It returns a static evaluation
858 /// of the position always from the point of view of the side to move.
860 Value evaluate(const Position& pos) {
861 return do_evaluate<false>(pos);
865 /// trace() is like evaluate(), but instead of returning a value, it returns
866 /// a string (suitable for outputting to stdout) that contains the detailed
867 /// descriptions and values of each evaluation term. It's mainly used for
869 std::string trace(const Position& pos) {
870 return Tracing::do_trace(pos);
874 /// init() computes evaluation weights, usually at startup
878 const int MaxSlope = 8700;
879 const int Peak = 1280000;
882 for (int i = 0; i < 400; ++i)
884 t = std::min(Peak, std::min(i * i * 27, t + MaxSlope));
885 KingDanger[i] = make_score(t / 1000, 0) * Weights[KingSafety];