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
5 Copyright (C) 2015-2016 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
7 Stockfish is free software: you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation, either version 3 of the License, or
10 (at your option) any later version.
12 Stockfish is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
17 You should have received a copy of the GNU General Public License
18 along with this program. If not, see <http://www.gnu.org/licenses/>.
23 #include <cstring> // For std::memset
36 enum Term { // The first 8 entries are for PieceType
37 MATERIAL = 8, IMBALANCE, MOBILITY, THREAT, PASSED, SPACE, TOTAL, TERM_NB
40 double scores[TERM_NB][COLOR_NB][PHASE_NB];
42 double to_cp(Value v) { return double(v) / PawnValueEg; }
44 void add(int idx, Color c, Score s) {
45 scores[idx][c][MG] = to_cp(mg_value(s));
46 scores[idx][c][EG] = to_cp(eg_value(s));
49 void add(int idx, Score w, Score b = SCORE_ZERO) {
50 add(idx, WHITE, w); add(idx, BLACK, b);
53 std::ostream& operator<<(std::ostream& os, Term t) {
55 if (t == MATERIAL || t == IMBALANCE || t == Term(PAWN) || t == TOTAL)
56 os << " --- --- | --- --- | ";
58 os << std::setw(5) << scores[t][WHITE][MG] << " "
59 << std::setw(5) << scores[t][WHITE][EG] << " | "
60 << std::setw(5) << scores[t][BLACK][MG] << " "
61 << std::setw(5) << scores[t][BLACK][EG] << " | ";
63 os << std::setw(5) << scores[t][WHITE][MG] - scores[t][BLACK][MG] << " "
64 << std::setw(5) << scores[t][WHITE][EG] - scores[t][BLACK][EG] << " \n";
70 using namespace Trace;
72 // Struct EvalInfo contains various information computed and collected
73 // by the evaluation functions.
76 // attackedBy[color][piece type] is a bitboard representing all squares
77 // attacked by a given color and piece type (can be also ALL_PIECES).
78 Bitboard attackedBy[COLOR_NB][PIECE_TYPE_NB];
80 // kingRing[color] is the zone around the king which is considered
81 // by the king safety evaluation. This consists of the squares directly
82 // adjacent to the king, and the three (or two, for a king on an edge file)
83 // squares two ranks in front of the king. For instance, if black's king
84 // is on g8, kingRing[BLACK] is a bitboard containing the squares f8, h8,
85 // f7, g7, h7, f6, g6 and h6.
86 Bitboard kingRing[COLOR_NB];
88 // kingAttackersCount[color] is the number of pieces of the given color
89 // which attack a square in the kingRing of the enemy king.
90 int kingAttackersCount[COLOR_NB];
92 // kingAttackersWeight[color] is the sum of the "weights" of the pieces of the
93 // given color which attack a square in the kingRing of the enemy king. The
94 // weights of the individual piece types are given by the elements in the
95 // KingAttackWeights array.
96 int kingAttackersWeight[COLOR_NB];
98 // kingAdjacentZoneAttacksCount[color] is the number of attacks by the given
99 // color to squares directly adjacent to the enemy king. Pieces which attack
100 // more than one square are counted multiple times. For instance, if there is
101 // a white knight on g5 and black's king is on g8, this white knight adds 2
102 // to kingAdjacentZoneAttacksCount[WHITE].
103 int kingAdjacentZoneAttacksCount[COLOR_NB];
105 Bitboard pinnedPieces[COLOR_NB];
110 #define V(v) Value(v)
111 #define S(mg, eg) make_score(mg, eg)
113 // MobilityBonus[PieceType][attacked] contains bonuses for middle and end
114 // game, indexed by piece type and number of attacked squares in the MobilityArea.
115 const Score MobilityBonus[][32] = {
117 { S(-75,-76), S(-56,-54), S(- 9,-26), S( -2,-10), S( 6, 5), S( 15, 11), // Knights
118 S( 22, 26), S( 30, 28), S( 36, 29) },
119 { S(-48,-58), S(-21,-19), S( 16, -2), S( 26, 12), S( 37, 22), S( 51, 42), // Bishops
120 S( 54, 54), S( 63, 58), S( 65, 63), S( 71, 70), S( 79, 74), S( 81, 86),
121 S( 92, 90), S( 97, 94) },
122 { S(-56,-78), S(-25,-18), S(-11, 26), S( -5, 55), S( -4, 70), S( -1, 81), // Rooks
123 S( 8,109), S( 14,120), S( 21,128), S( 23,143), S( 31,154), S( 32,160),
124 S( 43,165), S( 49,168), S( 59,169) },
125 { S(-40,-35), S(-25,-12), S( 2, 7), S( 4, 19), S( 14, 37), S( 24, 55), // Queens
126 S( 25, 62), S( 40, 76), S( 43, 79), S( 47, 87), S( 54, 94), S( 56,102),
127 S( 60,111), S( 70,116), S( 72,118), S( 73,122), S( 75,128), S( 77,130),
128 S( 85,133), S( 94,136), S( 99,140), S(108,157), S(112,158), S(113,161),
129 S(118,174), S(119,177), S(123,191), S(128,199) }
132 // Outpost[knight/bishop][supported by pawn] contains bonuses for knights and
133 // bishops outposts, bigger if outpost piece is supported by a pawn.
134 const Score Outpost[][2] = {
135 { S(43,11), S(65,20) }, // Knights
136 { S(20, 3), S(29, 8) } // Bishops
139 // ReachableOutpost[knight/bishop][supported by pawn] contains bonuses for
140 // knights and bishops which can reach an outpost square in one move, bigger
141 // if outpost square is supported by a pawn.
142 const Score ReachableOutpost[][2] = {
143 { S(21, 5), S(35, 8) }, // Knights
144 { S( 8, 0), S(14, 4) } // Bishops
147 // RookOnFile[semiopen/open] contains bonuses for each rook when there is no
148 // friendly pawn on the rook file.
149 const Score RookOnFile[2] = { S(20, 7), S(45, 20) };
151 // ThreatBySafePawn[PieceType] contains bonuses according to which piece
152 // type is attacked by a pawn which is protected or is not attacked.
153 const Score ThreatBySafePawn[PIECE_TYPE_NB] = {
154 S(0, 0), S(0, 0), S(176, 139), S(131, 127), S(217, 218), S(203, 215) };
156 // Threat[by minor/by rook][attacked PieceType] contains
157 // bonuses according to which piece type attacks which one.
158 // Attacks on lesser pieces which are pawn-defended are not considered.
159 const Score Threat[][PIECE_TYPE_NB] = {
160 { S(0, 0), S(0, 33), S(45, 43), S(46, 47), S(72,107), S(48,118) }, // by Minor
161 { S(0, 0), S(0, 25), S(40, 62), S(40, 59), S( 0, 34), S(35, 48) } // by Rook
164 // ThreatByKing[on one/on many] contains bonuses for King attacks on
165 // pawns or pieces which are not pawn-defended.
166 const Score ThreatByKing[2] = { S(3, 62), S(9, 138) };
168 // Passed[mg/eg][Rank] contains midgame and endgame bonuses for passed pawns.
169 // We don't use a Score because we process the two components independently.
170 const Value Passed[][RANK_NB] = {
171 { V(5), V( 5), V(31), V(73), V(166), V(252) },
172 { V(7), V(14), V(38), V(73), V(166), V(252) }
175 // PassedFile[File] contains a bonus according to the file of a passed pawn
176 const Score PassedFile[FILE_NB] = {
177 S( 9, 10), S( 2, 10), S( 1, -8), S(-20,-12),
178 S(-20,-12), S( 1, -8), S( 2, 10), S( 9, 10)
181 // Assorted bonuses and penalties used by evaluation
182 const Score MinorBehindPawn = S(16, 0);
183 const Score BishopPawns = S( 8, 12);
184 const Score RookOnPawn = S( 8, 24);
185 const Score TrappedRook = S(92, 0);
186 const Score SafeCheck = S(20, 20);
187 const Score OtherCheck = S(10, 10);
188 const Score ThreatByHangingPawn = S(71, 61);
189 const Score LooseEnemies = S( 0, 25);
190 const Score Hanging = S(48, 27);
191 const Score ThreatByPawnPush = S(38, 22);
192 const Score Unstoppable = S( 0, 20);
194 // Penalty for a bishop on a1/h1 (a8/h8 for black) which is trapped by
195 // a friendly pawn on b2/g2 (b7/g7 for black). This can obviously only
196 // happen in Chess960 games.
197 const Score TrappedBishopA1H1 = S(50, 50);
202 // King danger constants and variables. The king danger scores are looked-up
203 // in KingDanger[]. Various little "meta-bonuses" measuring the strength
204 // of the enemy attack are added up into an integer, which is used as an
205 // index to KingDanger[].
206 Score KingDanger[512];
208 // KingAttackWeights[PieceType] contains king attack weights by piece type
209 const int KingAttackWeights[PIECE_TYPE_NB] = { 0, 0, 7, 5, 4, 1 };
211 // Penalties for enemy's safe checks
212 const int QueenContactCheck = 89;
213 const int QueenCheck = 52;
214 const int RookCheck = 45;
215 const int BishopCheck = 5;
216 const int KnightCheck = 17;
219 // eval_init() initializes king and attack bitboards for a given color
220 // adding pawn attacks. To be done at the beginning of the evaluation.
223 void eval_init(const Position& pos, EvalInfo& ei) {
225 const Color Them = (Us == WHITE ? BLACK : WHITE);
226 const Square Down = (Us == WHITE ? DELTA_S : DELTA_N);
228 ei.pinnedPieces[Us] = pos.pinned_pieces(Us);
229 Bitboard b = ei.attackedBy[Them][KING] = pos.attacks_from<KING>(pos.square<KING>(Them));
230 ei.attackedBy[Them][ALL_PIECES] |= b;
231 ei.attackedBy[Us][ALL_PIECES] |= ei.attackedBy[Us][PAWN] = ei.pi->pawn_attacks(Us);
233 // Init king safety tables only if we are going to use them
234 if (pos.non_pawn_material(Us) >= QueenValueMg)
236 ei.kingRing[Them] = b | shift_bb<Down>(b);
237 b &= ei.attackedBy[Us][PAWN];
238 ei.kingAttackersCount[Us] = popcount(b);
239 ei.kingAdjacentZoneAttacksCount[Us] = ei.kingAttackersWeight[Us] = 0;
242 ei.kingRing[Them] = ei.kingAttackersCount[Us] = 0;
246 // evaluate_pieces() assigns bonuses and penalties to the pieces of a given
249 template<bool DoTrace, Color Us = WHITE, PieceType Pt = KNIGHT>
250 Score evaluate_pieces(const Position& pos, EvalInfo& ei, Score* mobility,
251 const Bitboard* mobilityArea) {
254 Score score = SCORE_ZERO;
256 const PieceType NextPt = (Us == WHITE ? Pt : PieceType(Pt + 1));
257 const Color Them = (Us == WHITE ? BLACK : WHITE);
258 const Bitboard OutpostRanks = (Us == WHITE ? Rank4BB | Rank5BB | Rank6BB
259 : Rank5BB | Rank4BB | Rank3BB);
260 const Square* pl = pos.squares<Pt>(Us);
262 ei.attackedBy[Us][Pt] = 0;
264 while ((s = *pl++) != SQ_NONE)
266 // Find attacked squares, including x-ray attacks for bishops and rooks
267 b = Pt == BISHOP ? attacks_bb<BISHOP>(s, pos.pieces() ^ pos.pieces(Us, QUEEN))
268 : Pt == ROOK ? attacks_bb< ROOK>(s, pos.pieces() ^ pos.pieces(Us, ROOK, QUEEN))
269 : pos.attacks_from<Pt>(s);
271 if (ei.pinnedPieces[Us] & s)
272 b &= LineBB[pos.square<KING>(Us)][s];
274 ei.attackedBy[Us][ALL_PIECES] |= ei.attackedBy[Us][Pt] |= b;
276 if (b & ei.kingRing[Them])
278 ei.kingAttackersCount[Us]++;
279 ei.kingAttackersWeight[Us] += KingAttackWeights[Pt];
280 ei.kingAdjacentZoneAttacksCount[Us] += popcount(b & ei.attackedBy[Them][KING]);
284 b &= ~( ei.attackedBy[Them][KNIGHT]
285 | ei.attackedBy[Them][BISHOP]
286 | ei.attackedBy[Them][ROOK]);
288 int mob = popcount(b & mobilityArea[Us]);
290 mobility[Us] += MobilityBonus[Pt][mob];
292 if (Pt == BISHOP || Pt == KNIGHT)
294 // Bonus for outpost squares
295 bb = OutpostRanks & ~ei.pi->pawn_attacks_span(Them);
297 score += Outpost[Pt == BISHOP][!!(ei.attackedBy[Us][PAWN] & s)];
300 bb &= b & ~pos.pieces(Us);
302 score += ReachableOutpost[Pt == BISHOP][!!(ei.attackedBy[Us][PAWN] & bb)];
305 // Bonus when behind a pawn
306 if ( relative_rank(Us, s) < RANK_5
307 && (pos.pieces(PAWN) & (s + pawn_push(Us))))
308 score += MinorBehindPawn;
310 // Penalty for pawns on the same color square as the bishop
312 score -= BishopPawns * ei.pi->pawns_on_same_color_squares(Us, s);
314 // An important Chess960 pattern: A cornered bishop blocked by a friendly
315 // pawn diagonally in front of it is a very serious problem, especially
316 // when that pawn is also blocked.
319 && (s == relative_square(Us, SQ_A1) || s == relative_square(Us, SQ_H1)))
321 Square d = pawn_push(Us) + (file_of(s) == FILE_A ? DELTA_E : DELTA_W);
322 if (pos.piece_on(s + d) == make_piece(Us, PAWN))
323 score -= !pos.empty(s + d + pawn_push(Us)) ? TrappedBishopA1H1 * 4
324 : pos.piece_on(s + d + d) == make_piece(Us, PAWN) ? TrappedBishopA1H1 * 2
331 // Bonus for aligning with enemy pawns on the same rank/file
332 if (relative_rank(Us, s) >= RANK_5)
333 score += RookOnPawn * popcount(pos.pieces(Them, PAWN) & PseudoAttacks[ROOK][s]);
335 // Bonus when on an open or semi-open file
336 if (ei.pi->semiopen_file(Us, file_of(s)))
337 score += RookOnFile[!!ei.pi->semiopen_file(Them, file_of(s))];
339 // Penalize when trapped by the king, even more if the king cannot castle
342 Square ksq = pos.square<KING>(Us);
344 if ( ((file_of(ksq) < FILE_E) == (file_of(s) < file_of(ksq)))
345 && (rank_of(ksq) == rank_of(s) || relative_rank(Us, ksq) == RANK_1)
346 && !ei.pi->semiopen_side(Us, file_of(ksq), file_of(s) < file_of(ksq)))
347 score -= (TrappedRook - make_score(mob * 22, 0)) * (1 + !pos.can_castle(Us));
353 Trace::add(Pt, Us, score);
355 // Recursively call evaluate_pieces() of next piece type until KING is excluded
356 return score - evaluate_pieces<DoTrace, Them, NextPt>(pos, ei, mobility, mobilityArea);
360 Score evaluate_pieces<false, WHITE, KING>(const Position&, EvalInfo&, Score*, const Bitboard*) { return SCORE_ZERO; }
362 Score evaluate_pieces< true, WHITE, KING>(const Position&, EvalInfo&, Score*, const Bitboard*) { return SCORE_ZERO; }
365 // evaluate_king() assigns bonuses and penalties to a king of a given color
367 template<Color Us, bool DoTrace>
368 Score evaluate_king(const Position& pos, const EvalInfo& ei) {
370 const Color Them = (Us == WHITE ? BLACK : WHITE);
371 const Square Up = (Us == WHITE ? DELTA_N : DELTA_S);
373 Bitboard undefended, b, b1, b2, safe, other;
375 const Square ksq = pos.square<KING>(Us);
377 // King shelter and enemy pawns storm
378 Score score = ei.pi->king_safety<Us>(pos, ksq);
380 // Main king safety evaluation
381 if (ei.kingAttackersCount[Them])
383 // Find the attacked squares which are defended only by the king...
384 undefended = ei.attackedBy[Them][ALL_PIECES]
385 & ei.attackedBy[Us][KING]
386 & ~( ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
387 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
388 | ei.attackedBy[Us][QUEEN]);
390 // ... and those which are not defended at all in the larger king ring
391 b = ei.attackedBy[Them][ALL_PIECES] & ~ei.attackedBy[Us][ALL_PIECES]
392 & ei.kingRing[Us] & ~pos.pieces(Them);
394 // Initialize the 'attackUnits' variable, which is used later on as an
395 // index into the KingDanger[] array. The initial value is based on the
396 // number and types of the enemy's attacking pieces, the number of
397 // attacked and undefended squares around our king and the quality of
398 // the pawn shelter (current 'score' value).
399 attackUnits = std::min(72, ei.kingAttackersCount[Them] * ei.kingAttackersWeight[Them])
400 + 9 * ei.kingAdjacentZoneAttacksCount[Them]
401 + 27 * popcount(undefended)
402 + 11 * (popcount(b) + !!ei.pinnedPieces[Us])
403 - 64 * !pos.count<QUEEN>(Them)
404 - mg_value(score) / 8;
406 // Analyse the enemy's safe queen contact checks. Firstly, find the
407 // undefended squares around the king reachable by the enemy queen...
408 b = undefended & ei.attackedBy[Them][QUEEN] & ~pos.pieces(Them);
411 // ...and then remove squares not supported by another enemy piece
412 b &= ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
413 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][ROOK]
414 | ei.attackedBy[Them][KING];
416 attackUnits += QueenContactCheck * popcount(b);
419 // Analyse the safe enemy's checks which are possible on next move...
420 safe = ~(ei.attackedBy[Us][ALL_PIECES] | pos.pieces(Them));
422 // ... and some other potential checks, only requiring the square to be
423 // safe from pawn-attacks, and not being occupied by a blocked pawn.
424 other = ~( ei.attackedBy[Us][PAWN]
425 | (pos.pieces(Them, PAWN) & shift_bb<Up>(pos.pieces(PAWN))));
427 b1 = pos.attacks_from<ROOK >(ksq);
428 b2 = pos.attacks_from<BISHOP>(ksq);
430 // Enemy queen safe checks
431 if ((b1 | b2) & ei.attackedBy[Them][QUEEN] & safe)
432 attackUnits += QueenCheck, score -= SafeCheck;
434 // Enemy rooks safe and other checks
435 if (b1 & ei.attackedBy[Them][ROOK] & safe)
436 attackUnits += RookCheck, score -= SafeCheck;
438 else if (b1 & ei.attackedBy[Them][ROOK] & other)
441 // Enemy bishops safe and other checks
442 if (b2 & ei.attackedBy[Them][BISHOP] & safe)
443 attackUnits += BishopCheck, score -= SafeCheck;
445 else if (b2 & ei.attackedBy[Them][BISHOP] & other)
448 // Enemy knights safe and other checks
449 b = pos.attacks_from<KNIGHT>(ksq) & ei.attackedBy[Them][KNIGHT];
451 attackUnits += KnightCheck, score -= SafeCheck;
456 // Finally, extract the king danger score from the KingDanger[]
457 // array and subtract the score from the evaluation.
458 score -= KingDanger[std::max(std::min(attackUnits, 399), 0)];
462 Trace::add(KING, Us, score);
468 // evaluate_threats() assigns bonuses according to the types of the attacking
469 // and the attacked pieces.
471 template<Color Us, bool DoTrace>
472 Score evaluate_threats(const Position& pos, const EvalInfo& ei) {
474 const Color Them = (Us == WHITE ? BLACK : WHITE);
475 const Square Up = (Us == WHITE ? DELTA_N : DELTA_S);
476 const Square Left = (Us == WHITE ? DELTA_NW : DELTA_SE);
477 const Square Right = (Us == WHITE ? DELTA_NE : DELTA_SW);
478 const Bitboard TRank2BB = (Us == WHITE ? Rank2BB : Rank7BB);
479 const Bitboard TRank7BB = (Us == WHITE ? Rank7BB : Rank2BB);
481 enum { Minor, Rook };
483 Bitboard b, weak, defended, safeThreats;
484 Score score = SCORE_ZERO;
486 // Small bonus if the opponent has loose pawns or pieces
487 if ( (pos.pieces(Them) ^ pos.pieces(Them, QUEEN, KING))
488 & ~(ei.attackedBy[Us][ALL_PIECES] | ei.attackedBy[Them][ALL_PIECES]))
489 score += LooseEnemies;
491 // Non-pawn enemies attacked by a pawn
492 weak = (pos.pieces(Them) ^ pos.pieces(Them, PAWN)) & ei.attackedBy[Us][PAWN];
496 b = pos.pieces(Us, PAWN) & ( ~ei.attackedBy[Them][ALL_PIECES]
497 | ei.attackedBy[Us][ALL_PIECES]);
499 safeThreats = (shift_bb<Right>(b) | shift_bb<Left>(b)) & weak;
501 if (weak ^ safeThreats)
502 score += ThreatByHangingPawn;
505 score += ThreatBySafePawn[type_of(pos.piece_on(pop_lsb(&safeThreats)))];
508 // Non-pawn enemies defended by a pawn
509 defended = (pos.pieces(Them) ^ pos.pieces(Them, PAWN)) & ei.attackedBy[Them][PAWN];
511 // Enemies not defended by a pawn and under our attack
512 weak = pos.pieces(Them)
513 & ~ei.attackedBy[Them][PAWN]
514 & ei.attackedBy[Us][ALL_PIECES];
516 // Add a bonus according to the kind of attacking pieces
519 b = (defended | weak) & (ei.attackedBy[Us][KNIGHT] | ei.attackedBy[Us][BISHOP]);
521 score += Threat[Minor][type_of(pos.piece_on(pop_lsb(&b)))];
523 b = (pos.pieces(Them, QUEEN) | weak) & ei.attackedBy[Us][ROOK];
525 score += Threat[Rook ][type_of(pos.piece_on(pop_lsb(&b)))];
527 score += Hanging * popcount(weak & ~ei.attackedBy[Them][ALL_PIECES]);
529 b = weak & ei.attackedBy[Us][KING];
531 score += ThreatByKing[more_than_one(b)];
534 // Bonus if some pawns can safely push and attack an enemy piece
535 b = pos.pieces(Us, PAWN) & ~TRank7BB;
536 b = shift_bb<Up>(b | (shift_bb<Up>(b & TRank2BB) & ~pos.pieces()));
539 & ~ei.attackedBy[Them][PAWN]
540 & (ei.attackedBy[Us][ALL_PIECES] | ~ei.attackedBy[Them][ALL_PIECES]);
542 b = (shift_bb<Left>(b) | shift_bb<Right>(b))
544 & ~ei.attackedBy[Us][PAWN];
546 score += ThreatByPawnPush * popcount(b);
549 Trace::add(THREAT, Us, score);
555 // evaluate_passed_pawns() evaluates the passed pawns of the given color
557 template<Color Us, bool DoTrace>
558 Score evaluate_passed_pawns(const Position& pos, const EvalInfo& ei) {
560 const Color Them = (Us == WHITE ? BLACK : WHITE);
562 Bitboard b, squaresToQueen, defendedSquares, unsafeSquares;
563 Score score = SCORE_ZERO;
565 b = ei.pi->passed_pawns(Us);
569 Square s = pop_lsb(&b);
571 assert(pos.pawn_passed(Us, s));
573 int r = relative_rank(Us, s) - RANK_2;
574 int rr = r * (r - 1);
576 Value mbonus = Passed[MG][r], ebonus = Passed[EG][r];
580 Square blockSq = s + pawn_push(Us);
582 // Adjust bonus based on the king's proximity
583 ebonus += distance(pos.square<KING>(Them), blockSq) * 5 * rr
584 - distance(pos.square<KING>(Us ), blockSq) * 2 * rr;
586 // If blockSq is not the queening square then consider also a second push
587 if (relative_rank(Us, blockSq) != RANK_8)
588 ebonus -= distance(pos.square<KING>(Us), blockSq + pawn_push(Us)) * rr;
590 // If the pawn is free to advance, then increase the bonus
591 if (pos.empty(blockSq))
593 // If there is a rook or queen attacking/defending the pawn from behind,
594 // consider all the squaresToQueen. Otherwise consider only the squares
595 // in the pawn's path attacked or occupied by the enemy.
596 defendedSquares = unsafeSquares = squaresToQueen = forward_bb(Us, s);
598 Bitboard bb = forward_bb(Them, s) & pos.pieces(ROOK, QUEEN) & pos.attacks_from<ROOK>(s);
600 if (!(pos.pieces(Us) & bb))
601 defendedSquares &= ei.attackedBy[Us][ALL_PIECES];
603 if (!(pos.pieces(Them) & bb))
604 unsafeSquares &= ei.attackedBy[Them][ALL_PIECES] | pos.pieces(Them);
606 // If there aren't any enemy attacks, assign a big bonus. Otherwise
607 // assign a smaller bonus if the block square isn't attacked.
608 int k = !unsafeSquares ? 18 : !(unsafeSquares & blockSq) ? 8 : 0;
610 // If the path to the queen is fully defended, assign a big bonus.
611 // Otherwise assign a smaller bonus if the block square is defended.
612 if (defendedSquares == squaresToQueen)
615 else if (defendedSquares & blockSq)
618 mbonus += k * rr, ebonus += k * rr;
620 else if (pos.pieces(Us) & blockSq)
621 mbonus += rr + r * 2, ebonus += rr + r * 2;
624 score += make_score(mbonus, ebonus) + PassedFile[file_of(s)];
628 Trace::add(PASSED, Us, score);
630 // Add the scores to the middlegame and endgame eval
635 // evaluate_space() computes the space evaluation for a given side. The
636 // space evaluation is a simple bonus based on the number of safe squares
637 // available for minor pieces on the central four files on ranks 2--4. Safe
638 // squares one, two or three squares behind a friendly pawn are counted
639 // twice. Finally, the space bonus is multiplied by a weight. The aim is to
640 // improve play on game opening.
642 Score evaluate_space(const Position& pos, const EvalInfo& ei) {
644 const Color Them = (Us == WHITE ? BLACK : WHITE);
645 const Bitboard SpaceMask =
646 Us == WHITE ? (FileCBB | FileDBB | FileEBB | FileFBB) & (Rank2BB | Rank3BB | Rank4BB)
647 : (FileCBB | FileDBB | FileEBB | FileFBB) & (Rank7BB | Rank6BB | Rank5BB);
649 // Find the safe squares for our pieces inside the area defined by
650 // SpaceMask. A square is unsafe if it is attacked by an enemy
651 // pawn, or if it is undefended and attacked by an enemy piece.
652 Bitboard safe = SpaceMask
653 & ~pos.pieces(Us, PAWN)
654 & ~ei.attackedBy[Them][PAWN]
655 & (ei.attackedBy[Us][ALL_PIECES] | ~ei.attackedBy[Them][ALL_PIECES]);
657 // Find all squares which are at most three squares behind some friendly pawn
658 Bitboard behind = pos.pieces(Us, PAWN);
659 behind |= (Us == WHITE ? behind >> 8 : behind << 8);
660 behind |= (Us == WHITE ? behind >> 16 : behind << 16);
662 // Since SpaceMask[Us] is fully on our half of the board...
663 assert(unsigned(safe >> (Us == WHITE ? 32 : 0)) == 0);
665 // ...count safe + (behind & safe) with a single popcount
666 int bonus = popcount((Us == WHITE ? safe << 32 : safe >> 32) | (behind & safe));
667 int weight = pos.count<KNIGHT>(Us) + pos.count<BISHOP>(Us)
668 + pos.count<KNIGHT>(Them) + pos.count<BISHOP>(Them);
670 return make_score(bonus * weight * weight * 2 / 11, 0);
674 // evaluate_initiative() computes the initiative correction value for the
675 // position, i.e., second order bonus/malus based on the known attacking/defending
676 // status of the players.
677 Score evaluate_initiative(const Position& pos, int asymmetry, Value eg) {
679 int kingDistance = distance<File>(pos.square<KING>(WHITE), pos.square<KING>(BLACK))
680 - distance<Rank>(pos.square<KING>(WHITE), pos.square<KING>(BLACK));
681 int pawns = pos.count<PAWN>(WHITE) + pos.count<PAWN>(BLACK);
683 // Compute the initiative bonus for the attacking side
684 int initiative = 8 * (asymmetry + kingDistance - 15) + 12 * pawns;
686 // Now apply the bonus: note that we find the attacking side by extracting
687 // the sign of the endgame value, and that we carefully cap the bonus so
688 // that the endgame score will never be divided by more than two.
689 int value = ((eg > 0) - (eg < 0)) * std::max(initiative, -abs(eg / 2));
691 return make_score(0, value);
695 // evaluate_scale_factor() computes the scale factor for the winning side
696 ScaleFactor evaluate_scale_factor(const Position& pos, const EvalInfo& ei, Value eg) {
698 Color strongSide = eg > VALUE_DRAW ? WHITE : BLACK;
699 ScaleFactor sf = ei.me->scale_factor(pos, strongSide);
701 // If we don't already have an unusual scale factor, check for certain
702 // types of endgames, and use a lower scale for those.
703 if ( ei.me->game_phase() < PHASE_MIDGAME
704 && (sf == SCALE_FACTOR_NORMAL || sf == SCALE_FACTOR_ONEPAWN))
706 if (pos.opposite_bishops())
708 // Endgame with opposite-colored bishops and no other pieces (ignoring pawns)
709 // is almost a draw, in case of KBP vs KB, it is even more a draw.
710 if ( pos.non_pawn_material(WHITE) == BishopValueMg
711 && pos.non_pawn_material(BLACK) == BishopValueMg)
712 sf = more_than_one(pos.pieces(PAWN)) ? ScaleFactor(31) : ScaleFactor(9);
714 // Endgame with opposite-colored bishops, but also other pieces. Still
715 // a bit drawish, but not as drawish as with only the two bishops.
717 sf = ScaleFactor(46 * sf / SCALE_FACTOR_NORMAL);
719 // Endings where weaker side can place his king in front of the opponent's
720 // pawns are drawish.
721 else if ( abs(eg) <= BishopValueEg
722 && ei.pi->pawn_span(strongSide) <= 1
723 && !pos.pawn_passed(~strongSide, pos.square<KING>(~strongSide)))
724 sf = ei.pi->pawn_span(strongSide) ? ScaleFactor(51) : ScaleFactor(37);
733 /// evaluate() is the main evaluation function. It returns a static evaluation
734 /// of the position from the point of view of the side to move.
736 template<bool DoTrace>
737 Value Eval::evaluate(const Position& pos) {
739 assert(!pos.checkers());
742 Score score, mobility[COLOR_NB] = { SCORE_ZERO, SCORE_ZERO };
744 // Initialize score by reading the incrementally updated scores included in
745 // the position object (material + piece square tables). Score is computed
746 // internally from the white point of view.
747 score = pos.psq_score();
749 // Probe the material hash table
750 ei.me = Material::probe(pos);
751 score += ei.me->imbalance();
753 // If we have a specialized evaluation function for the current material
754 // configuration, call it and return.
755 if (ei.me->specialized_eval_exists())
756 return ei.me->evaluate(pos);
758 // Probe the pawn hash table
759 ei.pi = Pawns::probe(pos);
760 score += ei.pi->pawns_score();
762 // Initialize attack and king safety bitboards
763 ei.attackedBy[WHITE][ALL_PIECES] = ei.attackedBy[BLACK][ALL_PIECES] = 0;
764 eval_init<WHITE>(pos, ei);
765 eval_init<BLACK>(pos, ei);
767 // Pawns blocked or on ranks 2 and 3 will be excluded from the mobility area
768 Bitboard blockedPawns[] = {
769 pos.pieces(WHITE, PAWN) & (shift_bb<DELTA_S>(pos.pieces()) | Rank2BB | Rank3BB),
770 pos.pieces(BLACK, PAWN) & (shift_bb<DELTA_N>(pos.pieces()) | Rank7BB | Rank6BB)
773 // Do not include in mobility area squares protected by enemy pawns, or occupied
774 // by our blocked pawns or king.
775 Bitboard mobilityArea[] = {
776 ~(ei.attackedBy[BLACK][PAWN] | blockedPawns[WHITE] | pos.square<KING>(WHITE)),
777 ~(ei.attackedBy[WHITE][PAWN] | blockedPawns[BLACK] | pos.square<KING>(BLACK))
780 // Evaluate all pieces but king and pawns
781 score += evaluate_pieces<DoTrace>(pos, ei, mobility, mobilityArea);
782 score += mobility[WHITE] - mobility[BLACK];
784 // Evaluate kings after all other pieces because we need full attack
785 // information when computing the king safety evaluation.
786 score += evaluate_king<WHITE, DoTrace>(pos, ei)
787 - evaluate_king<BLACK, DoTrace>(pos, ei);
789 // Evaluate tactical threats, we need full attack information including king
790 score += evaluate_threats<WHITE, DoTrace>(pos, ei)
791 - evaluate_threats<BLACK, DoTrace>(pos, ei);
793 // Evaluate passed pawns, we need full attack information including king
794 score += evaluate_passed_pawns<WHITE, DoTrace>(pos, ei)
795 - evaluate_passed_pawns<BLACK, DoTrace>(pos, ei);
797 // If both sides have only pawns, score for potential unstoppable pawns
798 if (!pos.non_pawn_material(WHITE) && !pos.non_pawn_material(BLACK))
801 if ((b = ei.pi->passed_pawns(WHITE)) != 0)
802 score += Unstoppable * int(relative_rank(WHITE, frontmost_sq(WHITE, b)));
804 if ((b = ei.pi->passed_pawns(BLACK)) != 0)
805 score -= Unstoppable * int(relative_rank(BLACK, frontmost_sq(BLACK, b)));
808 // Evaluate space for both sides, only during opening
809 if (pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK) >= 12222)
810 score += evaluate_space<WHITE>(pos, ei)
811 - evaluate_space<BLACK>(pos, ei);
813 // Evaluate position potential for the winning side
814 score += evaluate_initiative(pos, ei.pi->pawn_asymmetry(), eg_value(score));
816 // Evaluate scale factor for the winning side
817 ScaleFactor sf = evaluate_scale_factor(pos, ei, eg_value(score));
819 // Interpolate between a middlegame and a (scaled by 'sf') endgame score
820 Value v = mg_value(score) * int(ei.me->game_phase())
821 + eg_value(score) * int(PHASE_MIDGAME - ei.me->game_phase()) * sf / SCALE_FACTOR_NORMAL;
823 v /= int(PHASE_MIDGAME);
825 // In case of tracing add all remaining individual evaluation terms
828 Trace::add(MATERIAL, pos.psq_score());
829 Trace::add(IMBALANCE, ei.me->imbalance());
830 Trace::add(PAWN, ei.pi->pawns_score());
831 Trace::add(MOBILITY, mobility[WHITE], mobility[BLACK]);
832 Trace::add(SPACE, evaluate_space<WHITE>(pos, ei)
833 , evaluate_space<BLACK>(pos, ei));
834 Trace::add(TOTAL, score);
837 return (pos.side_to_move() == WHITE ? v : -v) + Eval::Tempo; // Side to move point of view
840 // Explicit template instantiations
841 template Value Eval::evaluate<true >(const Position&);
842 template Value Eval::evaluate<false>(const Position&);
845 /// trace() is like evaluate(), but instead of returning a value, it returns
846 /// a string (suitable for outputting to stdout) that contains the detailed
847 /// descriptions and values of each evaluation term. Useful for debugging.
849 std::string Eval::trace(const Position& pos) {
851 std::memset(scores, 0, sizeof(scores));
853 Value v = evaluate<true>(pos);
854 v = pos.side_to_move() == WHITE ? v : -v; // White's point of view
856 std::stringstream ss;
857 ss << std::showpoint << std::noshowpos << std::fixed << std::setprecision(2)
858 << " Eval term | White | Black | Total \n"
859 << " | MG EG | MG EG | MG EG \n"
860 << "----------------+-------------+-------------+-------------\n"
861 << " Material | " << Term(MATERIAL)
862 << " Imbalance | " << Term(IMBALANCE)
863 << " Pawns | " << Term(PAWN)
864 << " Knights | " << Term(KNIGHT)
865 << " Bishop | " << Term(BISHOP)
866 << " Rooks | " << Term(ROOK)
867 << " Queens | " << Term(QUEEN)
868 << " Mobility | " << Term(MOBILITY)
869 << " King safety | " << Term(KING)
870 << " Threats | " << Term(THREAT)
871 << " Passed pawns | " << Term(PASSED)
872 << " Space | " << Term(SPACE)
873 << "----------------+-------------+-------------+-------------\n"
874 << " Total | " << Term(TOTAL);
876 ss << "\nTotal Evaluation: " << to_cp(v) << " (white side)\n";
882 /// init() computes evaluation weights, usually at startup
886 const int MaxSlope = 322;
887 const int Peak = 47410;
890 for (int i = 0; i < 400; ++i)
892 t = std::min(Peak, std::min(i * i - 16, t + MaxSlope));
893 KingDanger[i] = make_score(t * 268 / 7700, 0);