2 Stockfish, a UCI chess playing engine derived from Glaurung 2.1
3 Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
4 Copyright (C) 2008-2010 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/>.
33 #include "ucioption.h"
37 //// Local definitions
42 const int Sign[2] = { 1, -1 };
44 // Evaluation grain size, must be a power of 2
45 const int GrainSize = 8;
47 // Evaluation weights, initialized from UCI options
48 enum { Mobility, PawnStructure, PassedPawns, Space, KingDangerUs, KingDangerThem };
52 #define S(mg, eg) make_score(mg, eg)
54 // Internal evaluation weights. These are applied on top of the evaluation
55 // weights read from UCI parameters. The purpose is to be able to change
56 // the evaluation weights while keeping the default values of the UCI
57 // parameters at 100, which looks prettier.
59 // Values modified by Joona Kiiski
60 const Score WeightsInternal[] = {
61 S(248, 271), S(233, 201), S(252, 259), S(46, 0), S(247, 0), S(259, 0)
64 // Knight mobility bonus in middle game and endgame, indexed by the number
65 // of attacked squares not occupied by friendly piecess.
66 const Score KnightMobilityBonus[16] = {
67 S(-38,-33), S(-25,-23), S(-12,-13), S( 0,-3),
68 S( 12, 7), S( 25, 17), S( 31, 22), S(38, 27), S(38, 27)
71 // Bishop mobility bonus in middle game and endgame, indexed by the number
72 // of attacked squares not occupied by friendly pieces. X-ray attacks through
73 // queens are also included.
74 const Score BishopMobilityBonus[16] = {
75 S(-25,-30), S(-11,-16), S( 3, -2), S(17, 12),
76 S( 31, 26), S( 45, 40), S(57, 52), S(65, 60),
77 S( 71, 65), S( 74, 69), S(76, 71), S(78, 73),
78 S( 79, 74), S( 80, 75), S(81, 76), S(81, 76)
81 // Rook mobility bonus in middle game and endgame, indexed by the number
82 // of attacked squares not occupied by friendly pieces. X-ray attacks through
83 // queens and rooks are also included.
84 const Score RookMobilityBonus[16] = {
85 S(-20,-36), S(-14,-19), S(-8, -3), S(-2, 13),
86 S( 4, 29), S( 10, 46), S(14, 62), S(19, 79),
87 S( 23, 95), S( 26,106), S(27,111), S(28,114),
88 S( 29,116), S( 30,117), S(31,118), S(32,118)
91 // Queen mobility bonus in middle game and endgame, indexed by the number
92 // of attacked squares not occupied by friendly pieces.
93 const Score QueenMobilityBonus[32] = {
94 S(-10,-18), S(-8,-13), S(-6, -7), S(-3, -2), S(-1, 3), S( 1, 8),
95 S( 3, 13), S( 5, 19), S( 8, 23), S(10, 27), S(12, 32), S(15, 34),
96 S( 16, 35), S(17, 35), S(18, 35), S(20, 35), S(20, 35), S(20, 35),
97 S( 20, 35), S(20, 35), S(20, 35), S(20, 35), S(20, 35), S(20, 35),
98 S( 20, 35), S(20, 35), S(20, 35), S(20, 35), S(20, 35), S(20, 35),
102 // Pointers table to access mobility tables through piece type
103 const Score* MobilityBonus[8] = { 0, 0, KnightMobilityBonus, BishopMobilityBonus,
104 RookMobilityBonus, QueenMobilityBonus, 0, 0 };
106 // Outpost bonuses for knights and bishops, indexed by square (from white's
108 const Value KnightOutpostBonus[64] = {
110 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 1
111 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 2
112 V(0), V(0), V(4), V(8), V(8), V(4), V(0), V(0), // 3
113 V(0), V(4),V(17),V(26),V(26),V(17), V(4), V(0), // 4
114 V(0), V(8),V(26),V(35),V(35),V(26), V(8), V(0), // 5
115 V(0), V(4),V(17),V(17),V(17),V(17), V(4), V(0), // 6
116 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 7
117 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0) // 8
120 const Value BishopOutpostBonus[64] = {
122 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 1
123 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 2
124 V(0), V(0), V(5), V(5), V(5), V(5), V(0), V(0), // 3
125 V(0), V(5),V(10),V(10),V(10),V(10), V(5), V(0), // 4
126 V(0),V(10),V(21),V(21),V(21),V(21),V(10), V(0), // 5
127 V(0), V(5), V(8), V(8), V(8), V(8), V(5), V(0), // 6
128 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 7
129 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0) // 8
132 // ThreatBonus[attacking][attacked] contains bonus according to which
133 // piece type attacks which one.
134 const Score ThreatBonus[8][8] = {
136 { S(0, 0), S( 7, 39), S( 0, 0), S(24, 49), S(41,100), S(41,100) }, // KNIGHT
137 { S(0, 0), S( 7, 39), S(24, 49), S( 0, 0), S(41,100), S(41,100) }, // BISHOP
138 { S(0, 0), S(-1, 29), S(15, 49), S(15, 49), S( 0, 0), S(24, 49) }, // ROOK
139 { S(0, 0), S(15, 39), S(15, 39), S(15, 39), S(15, 39), S( 0, 0) } // QUEEN
142 // ThreatedByPawnPenalty[] contains a penalty according to which piece
143 // type is attacked by an enemy pawn.
144 const Score ThreatedByPawnPenalty[8] = {
145 S(0, 0), S(0, 0), S(56, 70), S(56, 70), S(76, 99), S(86, 118)
150 // Bonus for unstoppable passed pawns
151 const Value UnstoppablePawnValue = Value(0x500);
153 // Rooks and queens on the 7th rank (modified by Joona Kiiski)
154 const Score RookOn7thBonus = make_score(47, 98);
155 const Score QueenOn7thBonus = make_score(27, 54);
157 // Rooks on open files (modified by Joona Kiiski)
158 const Score RookOpenFileBonus = make_score(43, 43);
159 const Score RookHalfOpenFileBonus = make_score(19, 19);
161 // Penalty for rooks trapped inside a friendly king which has lost the
163 const Value TrappedRookPenalty = Value(180);
165 // Penalty for a bishop on a7/h7 (a2/h2 for black) which is trapped by
167 const Score TrappedBishopA7H7Penalty = make_score(300, 300);
169 // Bitboard masks for detecting trapped bishops on a7/h7 (a2/h2 for black)
170 const Bitboard MaskA7H7[2] = {
171 ((1ULL << SQ_A7) | (1ULL << SQ_H7)),
172 ((1ULL << SQ_A2) | (1ULL << SQ_H2))
175 // Penalty for a bishop on a1/h1 (a8/h8 for black) which is trapped by
176 // a friendly pawn on b2/g2 (b7/g7 for black). This can obviously only
177 // happen in Chess960 games.
178 const Score TrappedBishopA1H1Penalty = make_score(100, 100);
180 // Bitboard masks for detecting trapped bishops on a1/h1 (a8/h8 for black)
181 const Bitboard MaskA1H1[2] = {
182 ((1ULL << SQ_A1) | (1ULL << SQ_H1)),
183 ((1ULL << SQ_A8) | (1ULL << SQ_H8))
186 // The SpaceMask[color] contains the area of the board which is considered
187 // by the space evaluation. In the middle game, each side is given a bonus
188 // based on how many squares inside this area are safe and available for
189 // friendly minor pieces.
190 const Bitboard SpaceMask[2] = {
191 (1ULL<<SQ_C2) | (1ULL<<SQ_D2) | (1ULL<<SQ_E2) | (1ULL<<SQ_F2) |
192 (1ULL<<SQ_C3) | (1ULL<<SQ_D3) | (1ULL<<SQ_E3) | (1ULL<<SQ_F3) |
193 (1ULL<<SQ_C4) | (1ULL<<SQ_D4) | (1ULL<<SQ_E4) | (1ULL<<SQ_F4),
194 (1ULL<<SQ_C7) | (1ULL<<SQ_D7) | (1ULL<<SQ_E7) | (1ULL<<SQ_F7) |
195 (1ULL<<SQ_C6) | (1ULL<<SQ_D6) | (1ULL<<SQ_E6) | (1ULL<<SQ_F6) |
196 (1ULL<<SQ_C5) | (1ULL<<SQ_D5) | (1ULL<<SQ_E5) | (1ULL<<SQ_F5)
199 /// King danger constants and variables. The king danger scores are taken
200 /// from the KingDangerTable[]. Various little "meta-bonuses" measuring
201 /// the strength of the enemy attack are added up into an integer, which
202 /// is used as an index to KingDangerTable[].
204 // KingAttackWeights[] contains king attack weights by piece type
205 const int KingAttackWeights[8] = { 0, 0, 2, 2, 3, 5 };
207 // Bonuses for enemy's safe checks
208 const int QueenContactCheckBonus = 3;
209 const int QueenCheckBonus = 2;
210 const int RookCheckBonus = 1;
211 const int BishopCheckBonus = 1;
212 const int KnightCheckBonus = 1;
214 // InitKingDanger[] contains bonuses based on the position of the defending
216 const int InitKingDanger[64] = {
217 2, 0, 2, 5, 5, 2, 0, 2,
218 2, 2, 4, 8, 8, 4, 2, 2,
219 7, 10, 12, 12, 12, 12, 10, 7,
220 15, 15, 15, 15, 15, 15, 15, 15,
221 15, 15, 15, 15, 15, 15, 15, 15,
222 15, 15, 15, 15, 15, 15, 15, 15,
223 15, 15, 15, 15, 15, 15, 15, 15,
224 15, 15, 15, 15, 15, 15, 15, 15
227 // KingDangerTable[color][] contains the actual king danger weighted scores
228 Score KingDangerTable[2][128];
230 // Pawn and material hash tables, indexed by the current thread id.
231 // Note that they will be initialized at 0 being global variables.
232 MaterialInfoTable* MaterialTable[MAX_THREADS];
233 PawnInfoTable* PawnTable[MAX_THREADS];
235 // Sizes of pawn and material hash tables
236 const int PawnTableSize = 16384;
237 const int MaterialTableSize = 1024;
239 // Function prototypes
240 template<bool HasPopCnt>
241 Value do_evaluate(const Position& pos, EvalInfo& ei);
243 template<Color Us, bool HasPopCnt>
244 void init_attack_tables(const Position& pos, EvalInfo& ei);
246 template<Color Us, bool HasPopCnt>
247 void evaluate_pieces_of_color(const Position& pos, EvalInfo& ei);
249 template<Color Us, bool HasPopCnt>
250 void evaluate_king(const Position& pos, EvalInfo& ei);
253 void evaluate_threats(const Position& pos, EvalInfo& ei);
255 template<Color Us, bool HasPopCnt>
256 int evaluate_space(const Position& pos, EvalInfo& ei);
259 void evaluate_passed_pawns(const Position& pos, EvalInfo& ei);
261 void evaluate_unstoppable_pawns(const Position& pos, EvalInfo& ei);
262 void evaluate_trapped_bishop_a7h7(const Position& pos, Square s, Color us, EvalInfo& ei);
263 void evaluate_trapped_bishop_a1h1(const Position& pos, Square s, Color us, EvalInfo& ei);
264 inline Score apply_weight(Score v, Score weight);
265 Value scale_by_game_phase(const Score& v, Phase ph, const ScaleFactor sf[]);
266 Score weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight);
275 /// evaluate() is the main evaluation function. It always computes two
276 /// values, an endgame score and a middle game score, and interpolates
277 /// between them based on the remaining material.
278 Value evaluate(const Position& pos, EvalInfo& ei) {
280 return CpuHasPOPCNT ? do_evaluate<true>(pos, ei)
281 : do_evaluate<false>(pos, ei);
286 template<bool HasPopCnt>
287 Value do_evaluate(const Position& pos, EvalInfo& ei) {
289 ScaleFactor factor[2];
292 assert(pos.thread() >= 0 && pos.thread() < MAX_THREADS);
293 assert(!pos.is_check());
295 memset(&ei, 0, sizeof(EvalInfo));
297 // Initialize by reading the incrementally updated scores included in the
298 // position object (material + piece square tables)
299 ei.value = pos.value();
301 // Probe the material hash table
302 ei.mi = MaterialTable[pos.thread()]->get_material_info(pos);
303 ei.value += ei.mi->material_value();
305 // If we have a specialized evaluation function for the current material
306 // configuration, call it and return
307 if (ei.mi->specialized_eval_exists())
308 return ei.mi->evaluate(pos);
310 // After get_material_info() call that modifies them
311 factor[WHITE] = ei.mi->scale_factor(pos, WHITE);
312 factor[BLACK] = ei.mi->scale_factor(pos, BLACK);
314 // Probe the pawn hash table
315 ei.pi = PawnTable[pos.thread()]->get_pawn_info(pos);
316 ei.value += apply_weight(ei.pi->pawns_value(), Weights[PawnStructure]);
318 // Initialize attack bitboards with pawns evaluation
319 init_attack_tables<WHITE, HasPopCnt>(pos, ei);
320 init_attack_tables<BLACK, HasPopCnt>(pos, ei);
323 evaluate_pieces_of_color<WHITE, HasPopCnt>(pos, ei);
324 evaluate_pieces_of_color<BLACK, HasPopCnt>(pos, ei);
326 // Kings. Kings are evaluated after all other pieces for both sides,
327 // because we need complete attack information for all pieces when computing
328 // the king safety evaluation.
329 evaluate_king<WHITE, HasPopCnt>(pos, ei);
330 evaluate_king<BLACK, HasPopCnt>(pos, ei);
332 // Evaluate tactical threats, we need full attack info including king
333 evaluate_threats<WHITE>(pos, ei);
334 evaluate_threats<BLACK>(pos, ei);
336 // Evaluate passed pawns, we need full attack info including king
337 evaluate_passed_pawns<WHITE>(pos, ei);
338 evaluate_passed_pawns<BLACK>(pos, ei);
340 // If one side has only a king, check whether exsists any unstoppable passed pawn
341 if (!pos.non_pawn_material(WHITE) || !pos.non_pawn_material(BLACK))
342 evaluate_unstoppable_pawns(pos, ei);
344 Phase phase = ei.mi->game_phase();
346 // Middle-game specific evaluation terms
347 if (phase > PHASE_ENDGAME)
349 // Pawn storms in positions with opposite castling
350 if ( square_file(pos.king_square(WHITE)) >= FILE_E
351 && square_file(pos.king_square(BLACK)) <= FILE_D)
353 ei.value += make_score(ei.pi->queenside_storm_value(WHITE) - ei.pi->kingside_storm_value(BLACK), 0);
355 else if ( square_file(pos.king_square(WHITE)) <= FILE_D
356 && square_file(pos.king_square(BLACK)) >= FILE_E)
358 ei.value += make_score(ei.pi->kingside_storm_value(WHITE) - ei.pi->queenside_storm_value(BLACK), 0);
360 // Evaluate space for both sides
361 if (ei.mi->space_weight() > 0)
363 int s = evaluate_space<WHITE, HasPopCnt>(pos, ei) - evaluate_space<BLACK, HasPopCnt>(pos, ei);
364 ei.value += apply_weight(make_score(s * ei.mi->space_weight(), 0), Weights[Space]);
369 ei.value += apply_weight(ei.mobility, Weights[Mobility]);
371 // If we don't already have an unusual scale factor, check for opposite
372 // colored bishop endgames, and use a lower scale for those
373 if ( phase < PHASE_MIDGAME
374 && pos.opposite_colored_bishops()
375 && ( (factor[WHITE] == SCALE_FACTOR_NORMAL && eg_value(ei.value) > Value(0))
376 || (factor[BLACK] == SCALE_FACTOR_NORMAL && eg_value(ei.value) < Value(0))))
380 // Only the two bishops ?
381 if ( pos.non_pawn_material(WHITE) == BishopValueMidgame
382 && pos.non_pawn_material(BLACK) == BishopValueMidgame)
384 // Check for KBP vs KB with only a single pawn that is almost
385 // certainly a draw or at least two pawns.
386 bool one_pawn = (pos.piece_count(WHITE, PAWN) + pos.piece_count(BLACK, PAWN) == 1);
387 sf = one_pawn ? ScaleFactor(8) : ScaleFactor(32);
390 // Endgame with opposite-colored bishops, but also other pieces. Still
391 // a bit drawish, but not as drawish as with only the two bishops.
392 sf = ScaleFactor(50);
394 if (factor[WHITE] == SCALE_FACTOR_NORMAL)
396 if (factor[BLACK] == SCALE_FACTOR_NORMAL)
400 // Interpolate between the middle game and the endgame score
401 return Sign[pos.side_to_move()] * scale_by_game_phase(ei.value, phase, factor);
406 /// init_eval() initializes various tables used by the evaluation function
408 void init_eval(int threads) {
410 assert(threads <= MAX_THREADS);
412 for (int i = 0; i < MAX_THREADS; i++)
417 delete MaterialTable[i];
419 MaterialTable[i] = NULL;
423 PawnTable[i] = new PawnInfoTable(PawnTableSize);
424 if (!MaterialTable[i])
425 MaterialTable[i] = new MaterialInfoTable(MaterialTableSize);
430 /// quit_eval() releases heap-allocated memory at program termination
434 for (int i = 0; i < MAX_THREADS; i++)
437 delete MaterialTable[i];
439 MaterialTable[i] = NULL;
444 /// read_weights() reads evaluation weights from the corresponding UCI parameters
446 void read_weights(Color us) {
448 // King safety is asymmetrical. Our king danger level is weighted by
449 // "Cowardice" UCI parameter, instead the opponent one by "Aggressiveness".
450 const int kingDangerUs = (us == WHITE ? KingDangerUs : KingDangerThem);
451 const int kingDangerThem = (us == WHITE ? KingDangerThem : KingDangerUs);
453 Weights[Mobility] = weight_option("Mobility (Middle Game)", "Mobility (Endgame)", WeightsInternal[Mobility]);
454 Weights[PawnStructure] = weight_option("Pawn Structure (Middle Game)", "Pawn Structure (Endgame)", WeightsInternal[PawnStructure]);
455 Weights[PassedPawns] = weight_option("Passed Pawns (Middle Game)", "Passed Pawns (Endgame)", WeightsInternal[PassedPawns]);
456 Weights[Space] = weight_option("Space", "Space", WeightsInternal[Space]);
457 Weights[kingDangerUs] = weight_option("Cowardice", "Cowardice", WeightsInternal[KingDangerUs]);
458 Weights[kingDangerThem] = weight_option("Aggressiveness", "Aggressiveness", WeightsInternal[KingDangerThem]);
460 // If running in analysis mode, make sure we use symmetrical king safety. We do this
461 // by replacing both Weights[kingDangerUs] and Weights[kingDangerThem] by their average.
462 if (get_option_value_bool("UCI_AnalyseMode"))
463 Weights[kingDangerUs] = Weights[kingDangerThem] = (Weights[kingDangerUs] + Weights[kingDangerThem]) / 2;
471 // init_attack_tables() initializes king bitboards for both sides adding
472 // pawn attacks. To be done before other evaluations.
474 template<Color Us, bool HasPopCnt>
475 void init_attack_tables(const Position& pos, EvalInfo& ei) {
477 const Color Them = (Us == WHITE ? BLACK : WHITE);
479 Bitboard b = ei.attackedBy[Them][KING] = pos.attacks_from<KING>(pos.king_square(Them));
480 ei.kingZone[Us] = (b | (Us == WHITE ? b >> 8 : b << 8));
481 ei.attackedBy[Us][PAWN] = ei.pi->pawn_attacks(Us);
482 b &= ei.attackedBy[Us][PAWN];
484 ei.kingAttackersCount[Us] = count_1s_max_15<HasPopCnt>(b) / 2;
488 // evaluate_outposts() evaluates bishop and knight outposts squares
490 template<PieceType Piece, Color Us>
491 void evaluate_outposts(const Position& pos, EvalInfo& ei, Square s) {
493 const Color Them = (Us == WHITE ? BLACK : WHITE);
495 // Initial bonus based on square
496 Value bonus = (Piece == BISHOP ? BishopOutpostBonus[relative_square(Us, s)]
497 : KnightOutpostBonus[relative_square(Us, s)]);
499 // Increase bonus if supported by pawn, especially if the opponent has
500 // no minor piece which can exchange the outpost piece
501 if (bonus && bit_is_set(ei.attackedBy[Us][PAWN], s))
503 if ( pos.pieces(KNIGHT, Them) == EmptyBoardBB
504 && (SquaresByColorBB[square_color(s)] & pos.pieces(BISHOP, Them)) == EmptyBoardBB)
505 bonus += bonus + bonus / 2;
509 ei.value += Sign[Us] * make_score(bonus, bonus);
513 // evaluate_pieces<>() assigns bonuses and penalties to the pieces of a given color
515 template<PieceType Piece, Color Us, bool HasPopCnt>
516 void evaluate_pieces(const Position& pos, EvalInfo& ei, Bitboard no_mob_area) {
523 const Color Them = (Us == WHITE ? BLACK : WHITE);
524 const Square* ptr = pos.piece_list_begin(Us, Piece);
526 while ((s = *ptr++) != SQ_NONE)
528 // Find attacked squares, including x-ray attacks for bishops and rooks
529 if (Piece == KNIGHT || Piece == QUEEN)
530 b = pos.attacks_from<Piece>(s);
531 else if (Piece == BISHOP)
532 b = bishop_attacks_bb(s, pos.occupied_squares() & ~pos.pieces(QUEEN, Us));
533 else if (Piece == ROOK)
534 b = rook_attacks_bb(s, pos.occupied_squares() & ~pos.pieces(ROOK, QUEEN, Us));
538 // Update attack info
539 ei.attackedBy[Us][Piece] |= b;
542 if (b & ei.kingZone[Us])
544 ei.kingAttackersCount[Us]++;
545 ei.kingAttackersWeight[Us] += KingAttackWeights[Piece];
546 Bitboard bb = (b & ei.attackedBy[Them][KING]);
548 ei.kingAdjacentZoneAttacksCount[Us] += count_1s_max_15<HasPopCnt>(bb);
552 mob = (Piece != QUEEN ? count_1s_max_15<HasPopCnt>(b & no_mob_area)
553 : count_1s<HasPopCnt>(b & no_mob_area));
555 ei.mobility += Sign[Us] * MobilityBonus[Piece][mob];
557 // Decrease score if we are attacked by an enemy pawn. Remaining part
558 // of threat evaluation must be done later when we have full attack info.
559 if (bit_is_set(ei.attackedBy[Them][PAWN], s))
560 ei.value -= Sign[Us] * ThreatedByPawnPenalty[Piece];
562 // Bishop and knight outposts squares
563 if ((Piece == BISHOP || Piece == KNIGHT) && pos.square_is_weak(s, Us))
564 evaluate_outposts<Piece, Us>(pos, ei, s);
566 // Special patterns: trapped bishops on a7/h7/a2/h2
567 // and trapped bishops on a1/h1/a8/h8 in Chess960.
570 if (bit_is_set(MaskA7H7[Us], s))
571 evaluate_trapped_bishop_a7h7(pos, s, Us, ei);
573 if (Chess960 && bit_is_set(MaskA1H1[Us], s))
574 evaluate_trapped_bishop_a1h1(pos, s, Us, ei);
577 // Queen or rook on 7th rank
578 if ( (Piece == ROOK || Piece == QUEEN)
579 && relative_rank(Us, s) == RANK_7
580 && relative_rank(Us, pos.king_square(Them)) == RANK_8)
582 ei.value += Sign[Us] * (Piece == ROOK ? RookOn7thBonus : QueenOn7thBonus);
585 // Special extra evaluation for rooks
588 // Open and half-open files
590 if (ei.pi->file_is_half_open(Us, f))
592 if (ei.pi->file_is_half_open(Them, f))
593 ei.value += Sign[Us] * RookOpenFileBonus;
595 ei.value += Sign[Us] * RookHalfOpenFileBonus;
598 // Penalize rooks which are trapped inside a king. Penalize more if
599 // king has lost right to castle.
600 if (mob > 6 || ei.pi->file_is_half_open(Us, f))
603 ksq = pos.king_square(Us);
605 if ( square_file(ksq) >= FILE_E
606 && square_file(s) > square_file(ksq)
607 && (relative_rank(Us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
609 // Is there a half-open file between the king and the edge of the board?
610 if (!ei.pi->has_open_file_to_right(Us, square_file(ksq)))
611 ei.value -= Sign[Us] * make_score(pos.can_castle(Us) ? (TrappedRookPenalty - mob * 16) / 2
612 : (TrappedRookPenalty - mob * 16), 0);
614 else if ( square_file(ksq) <= FILE_D
615 && square_file(s) < square_file(ksq)
616 && (relative_rank(Us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
618 // Is there a half-open file between the king and the edge of the board?
619 if (!ei.pi->has_open_file_to_left(Us, square_file(ksq)))
620 ei.value -= Sign[Us] * make_score(pos.can_castle(Us) ? (TrappedRookPenalty - mob * 16) / 2
621 : (TrappedRookPenalty - mob * 16), 0);
628 // evaluate_threats<>() assigns bonuses according to the type of attacking piece
629 // and the type of attacked one.
632 void evaluate_threats(const Position& pos, EvalInfo& ei) {
634 const Color Them = (Us == WHITE ? BLACK : WHITE);
637 Score bonus = make_score(0, 0);
639 // Enemy pieces not defended by a pawn and under our attack
640 Bitboard weakEnemies = pos.pieces_of_color(Them)
641 & ~ei.attackedBy[Them][PAWN]
642 & ei.attackedBy[Us][0];
646 // Add bonus according to type of attacked enemy pieces and to the
647 // type of attacking piece, from knights to queens. Kings are not
648 // considered because are already special handled in king evaluation.
649 for (PieceType pt1 = KNIGHT; pt1 < KING; pt1++)
651 b = ei.attackedBy[Us][pt1] & weakEnemies;
653 for (PieceType pt2 = PAWN; pt2 < KING; pt2++)
654 if (b & pos.pieces(pt2))
655 bonus += ThreatBonus[pt1][pt2];
657 ei.value += Sign[Us] * bonus;
661 // evaluate_pieces_of_color<>() assigns bonuses and penalties to all the
662 // pieces of a given color.
664 template<Color Us, bool HasPopCnt>
665 void evaluate_pieces_of_color(const Position& pos, EvalInfo& ei) {
667 const Color Them = (Us == WHITE ? BLACK : WHITE);
669 // Do not include in mobility squares protected by enemy pawns or occupied by our pieces
670 const Bitboard no_mob_area = ~(ei.attackedBy[Them][PAWN] | pos.pieces_of_color(Us));
672 evaluate_pieces<KNIGHT, Us, HasPopCnt>(pos, ei, no_mob_area);
673 evaluate_pieces<BISHOP, Us, HasPopCnt>(pos, ei, no_mob_area);
674 evaluate_pieces<ROOK, Us, HasPopCnt>(pos, ei, no_mob_area);
675 evaluate_pieces<QUEEN, Us, HasPopCnt>(pos, ei, no_mob_area);
677 // Sum up all attacked squares
678 ei.attackedBy[Us][0] = ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
679 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
680 | ei.attackedBy[Us][QUEEN] | ei.attackedBy[Us][KING];
684 // evaluate_king<>() assigns bonuses and penalties to a king of a given color
686 template<Color Us, bool HasPopCnt>
687 void evaluate_king(const Position& pos, EvalInfo& ei) {
689 const Color Them = (Us == WHITE ? BLACK : WHITE);
691 Bitboard undefended, b, b1, b2, safe;
693 int attackUnits, shelter = 0;
694 const Square ksq = pos.king_square(Us);
697 if (relative_rank(Us, ksq) <= RANK_4)
699 shelter = ei.pi->get_king_shelter(pos, Us, ksq);
700 ei.value += Sign[Us] * make_score(shelter, 0);
703 // King safety. This is quite complicated, and is almost certainly far
704 // from optimally tuned.
705 if ( pos.piece_count(Them, QUEEN) >= 1
706 && ei.kingAttackersCount[Them] >= 2
707 && pos.non_pawn_material(Them) >= QueenValueMidgame + RookValueMidgame
708 && ei.kingAdjacentZoneAttacksCount[Them])
710 // Is it the attackers turn to move?
711 sente = (Them == pos.side_to_move());
713 // Find the attacked squares around the king which has no defenders
714 // apart from the king itself
715 undefended = ei.attacked_by(Them) & ei.attacked_by(Us, KING);
716 undefended &= ~( ei.attacked_by(Us, PAWN) | ei.attacked_by(Us, KNIGHT)
717 | ei.attacked_by(Us, BISHOP) | ei.attacked_by(Us, ROOK)
718 | ei.attacked_by(Us, QUEEN));
720 // Initialize the 'attackUnits' variable, which is used later on as an
721 // index to the KingDangerTable[] array. The initial value is based on
722 // the number and types of the enemy's attacking pieces, the number of
723 // attacked and undefended squares around our king, the square of the
724 // king, and the quality of the pawn shelter.
725 attackUnits = Min(25, (ei.kingAttackersCount[Them] * ei.kingAttackersWeight[Them]) / 2)
726 + 3 * (ei.kingAdjacentZoneAttacksCount[Them] + count_1s_max_15<HasPopCnt>(undefended))
727 + InitKingDanger[relative_square(Us, ksq)]
730 // Analyse enemy's safe queen contact checks. First find undefended
731 // squares around the king attacked by enemy queen...
732 b = undefended & ei.attacked_by(Them, QUEEN) & ~pos.pieces_of_color(Them);
735 // ...then remove squares not supported by another enemy piece
736 b &= ( ei.attacked_by(Them, PAWN) | ei.attacked_by(Them, KNIGHT)
737 | ei.attacked_by(Them, BISHOP) | ei.attacked_by(Them, ROOK));
739 attackUnits += QueenContactCheckBonus * count_1s_max_15<HasPopCnt>(b) * (sente ? 2 : 1);
742 // Analyse enemy's safe distance checks for sliders and knights
743 safe = ~(pos.pieces_of_color(Them) | ei.attacked_by(Us));
745 b1 = pos.attacks_from<ROOK>(ksq) & safe;
746 b2 = pos.attacks_from<BISHOP>(ksq) & safe;
748 // Enemy queen safe checks
749 b = (b1 | b2) & ei.attacked_by(Them, QUEEN);
751 attackUnits += QueenCheckBonus * count_1s_max_15<HasPopCnt>(b);
753 // Enemy rooks safe checks
754 b = b1 & ei.attacked_by(Them, ROOK);
756 attackUnits += RookCheckBonus * count_1s_max_15<HasPopCnt>(b);
758 // Enemy bishops safe checks
759 b = b2 & ei.attacked_by(Them, BISHOP);
761 attackUnits += BishopCheckBonus * count_1s_max_15<HasPopCnt>(b);
763 // Enemy knights safe checks
764 b = pos.attacks_from<KNIGHT>(ksq) & ei.attacked_by(Them, KNIGHT) & safe;
766 attackUnits += KnightCheckBonus * count_1s_max_15<HasPopCnt>(b);
768 // To index KingDangerTable[] attackUnits must be in [0, 99] range
769 attackUnits = Min(99, Max(0, attackUnits));
771 // Finally, extract the king danger score from the KingDangerTable[]
772 // array and subtract the score from evaluation. Set also ei.kingDanger[]
773 // value that will be used for pruning because this value can sometimes
774 // be very big, and so capturing a single attacking piece can therefore
775 // result in a score change far bigger than the value of the captured piece.
776 ei.value -= Sign[Us] * KingDangerTable[Us][attackUnits];
777 ei.kingDanger[Us] = mg_value(KingDangerTable[Us][attackUnits]);
782 // evaluate_passed_pawns<>() evaluates the passed pawns of the given color
785 void evaluate_passed_pawns(const Position& pos, EvalInfo& ei) {
787 const Color Them = (Us == WHITE ? BLACK : WHITE);
789 Bitboard squaresToQueen, defendedSquares, unsafeSquares, supportingPawns;
790 Bitboard b = ei.pi->passed_pawns() & pos.pieces_of_color(Us);
794 Square s = pop_1st_bit(&b);
796 assert(pos.pawn_is_passed(Us, s));
798 int r = int(relative_rank(Us, s) - RANK_2);
799 int tr = r * (r - 1);
801 // Base bonus based on rank
802 Value mbonus = Value(20 * tr);
803 Value ebonus = Value(10 + r * r * 10);
807 Square blockSq = s + pawn_push(Us);
809 // Adjust bonus based on kings proximity
810 ebonus -= Value(square_distance(pos.king_square(Us), blockSq) * 3 * tr);
811 ebonus -= Value(square_distance(pos.king_square(Us), blockSq + pawn_push(Us)) * 1 * tr);
812 ebonus += Value(square_distance(pos.king_square(Them), blockSq) * 6 * tr);
814 // If the pawn is free to advance, increase bonus
815 if (pos.square_is_empty(blockSq))
817 squaresToQueen = squares_in_front_of(Us, s);
818 defendedSquares = squaresToQueen & ei.attacked_by(Us);
820 // If there is an enemy rook or queen attacking the pawn from behind,
821 // add all X-ray attacks by the rook or queen. Otherwise consider only
822 // the squares in the pawn's path attacked or occupied by the enemy.
823 if ( (squares_behind(Us, s) & pos.pieces(ROOK, QUEEN, Them))
824 && (squares_behind(Us, s) & pos.pieces(ROOK, QUEEN, Them) & pos.attacks_from<ROOK>(s)))
825 unsafeSquares = squaresToQueen;
827 unsafeSquares = squaresToQueen & (ei.attacked_by(Them) | pos.pieces_of_color(Them));
829 // If there aren't enemy attacks or pieces along the path to queen give
830 // huge bonus. Even bigger if we protect the pawn's path.
832 ebonus += Value(tr * (squaresToQueen == defendedSquares ? 17 : 15));
834 // OK, there are enemy attacks or pieces (but not pawns). Are those
835 // squares which are attacked by the enemy also attacked by us ?
836 // If yes, big bonus (but smaller than when there are no enemy attacks),
837 // if no, somewhat smaller bonus.
838 ebonus += Value(tr * ((unsafeSquares & defendedSquares) == unsafeSquares ? 13 : 8));
840 // At last, add a small bonus when there are no *friendly* pieces
841 // in the pawn's path.
842 if (!(squaresToQueen & pos.pieces_of_color(Us)))
847 // Increase the bonus if the passed pawn is supported by a friendly pawn
848 // on the same rank and a bit smaller if it's on the previous rank.
849 supportingPawns = pos.pieces(PAWN, Us) & neighboring_files_bb(s);
850 if (supportingPawns & rank_bb(s))
851 ebonus += Value(r * 20);
852 else if (supportingPawns & rank_bb(s - pawn_push(Us)))
853 ebonus += Value(r * 12);
855 // Rook pawns are a special case: They are sometimes worse, and
856 // sometimes better than other passed pawns. It is difficult to find
857 // good rules for determining whether they are good or bad. For now,
858 // we try the following: Increase the value for rook pawns if the
859 // other side has no pieces apart from a knight, and decrease the
860 // value if the other side has a rook or queen.
861 if (square_file(s) == FILE_A || square_file(s) == FILE_H)
863 if (pos.non_pawn_material(Them) <= KnightValueMidgame)
864 ebonus += ebonus / 4;
865 else if (pos.pieces(ROOK, QUEEN, Them))
866 ebonus -= ebonus / 4;
869 // Add the scores for this pawn to the middle game and endgame eval
870 ei.value += Sign[Us] * apply_weight(make_score(mbonus, ebonus), Weights[PassedPawns]);
876 // evaluate_unstoppable_pawns() evaluates the unstoppable passed pawns for both sides
878 void evaluate_unstoppable_pawns(const Position& pos, EvalInfo& ei) {
880 int movesToGo[2] = {0, 0};
881 Square pawnToGo[2] = {SQ_NONE, SQ_NONE};
883 for (Color c = WHITE; c <= BLACK; c++)
885 // Skip evaluation if other side has non-pawn pieces
886 if (pos.non_pawn_material(opposite_color(c)))
889 Bitboard b = ei.pi->passed_pawns() & pos.pieces_of_color(c);
893 Square s = pop_1st_bit(&b);
894 Square queeningSquare = relative_square(c, make_square(square_file(s), RANK_8));
895 int d = square_distance(s, queeningSquare)
896 - int(relative_rank(c, s) == RANK_2) // Double pawn push
897 - square_distance(pos.king_square(opposite_color(c)), queeningSquare)
898 + int(c != pos.side_to_move());
900 // Do we protect the path to queening ?
901 bool pathDefended = (ei.attacked_by(c) & squares_in_front_of(c, s)) == squares_in_front_of(c, s);
903 if (d < 0 || pathDefended)
905 int mtg = RANK_8 - relative_rank(c, s) - int(relative_rank(c, s) == RANK_2);
906 int blockerCount = count_1s_max_15(squares_in_front_of(c, s) & pos.occupied_squares());
909 if ((d < 0 || pathDefended) && (!movesToGo[c] || movesToGo[c] > mtg))
918 // Neither side has an unstoppable passed pawn?
919 if (!(movesToGo[WHITE] | movesToGo[BLACK]))
922 // Does only one side have an unstoppable passed pawn?
923 if (!movesToGo[WHITE] || !movesToGo[BLACK])
925 Color winnerSide = movesToGo[WHITE] ? WHITE : BLACK;
926 ei.value += make_score(0, Sign[winnerSide] * (UnstoppablePawnValue - Value(0x40 * movesToGo[winnerSide])));
929 { // Both sides have unstoppable pawns! Try to find out who queens
930 // first. We begin by transforming 'movesToGo' to the number of
931 // plies until the pawn queens for both sides.
932 movesToGo[WHITE] *= 2;
933 movesToGo[BLACK] *= 2;
934 movesToGo[pos.side_to_move()]--;
936 Color winnerSide = movesToGo[WHITE] < movesToGo[BLACK] ? WHITE : BLACK;
937 Color loserSide = opposite_color(winnerSide);
939 // If one side queens at least three plies before the other, that side wins
940 if (movesToGo[winnerSide] <= movesToGo[loserSide] - 3)
941 ei.value += Sign[winnerSide] * make_score(0, UnstoppablePawnValue - Value(0x40 * (movesToGo[winnerSide]/2)));
943 // If one side queens one ply before the other and checks the king or attacks
944 // the undefended opponent's queening square, that side wins. To avoid cases
945 // where the opponent's king could move somewhere before first pawn queens we
946 // consider only free paths to queen for both pawns.
947 else if ( !(squares_in_front_of(WHITE, pawnToGo[WHITE]) & pos.occupied_squares())
948 && !(squares_in_front_of(BLACK, pawnToGo[BLACK]) & pos.occupied_squares()))
950 assert(movesToGo[loserSide] - movesToGo[winnerSide] == 1);
952 Square winnerQSq = relative_square(winnerSide, make_square(square_file(pawnToGo[winnerSide]), RANK_8));
953 Square loserQSq = relative_square(loserSide, make_square(square_file(pawnToGo[loserSide]), RANK_8));
955 Bitboard b = pos.occupied_squares();
956 clear_bit(&b, pawnToGo[winnerSide]);
957 clear_bit(&b, pawnToGo[loserSide]);
958 b = queen_attacks_bb(winnerQSq, b);
960 if ( (b & pos.pieces(KING, loserSide))
961 ||(bit_is_set(b, loserQSq) && !bit_is_set(ei.attacked_by(loserSide), loserQSq)))
962 ei.value += Sign[winnerSide] * make_score(0, UnstoppablePawnValue - Value(0x40 * (movesToGo[winnerSide]/2)));
968 // evaluate_trapped_bishop_a7h7() determines whether a bishop on a7/h7
969 // (a2/h2 for black) is trapped by enemy pawns, and assigns a penalty
972 void evaluate_trapped_bishop_a7h7(const Position& pos, Square s, Color us, EvalInfo &ei) {
974 assert(square_is_ok(s));
975 assert(pos.piece_on(s) == piece_of_color_and_type(us, BISHOP));
977 Square b6 = relative_square(us, (square_file(s) == FILE_A) ? SQ_B6 : SQ_G6);
978 Square b8 = relative_square(us, (square_file(s) == FILE_A) ? SQ_B8 : SQ_G8);
980 if ( pos.piece_on(b6) == piece_of_color_and_type(opposite_color(us), PAWN)
981 && pos.see(s, b6) < 0
982 && pos.see(s, b8) < 0)
984 ei.value -= Sign[us] * TrappedBishopA7H7Penalty;
989 // evaluate_trapped_bishop_a1h1() determines whether a bishop on a1/h1
990 // (a8/h8 for black) is trapped by a friendly pawn on b2/g2 (b7/g7 for
991 // black), and assigns a penalty if it is. This pattern can obviously
992 // only occur in Chess960 games.
994 void evaluate_trapped_bishop_a1h1(const Position& pos, Square s, Color us, EvalInfo& ei) {
996 Piece pawn = piece_of_color_and_type(us, PAWN);
1000 assert(square_is_ok(s));
1001 assert(pos.piece_on(s) == piece_of_color_and_type(us, BISHOP));
1003 if (square_file(s) == FILE_A)
1005 b2 = relative_square(us, SQ_B2);
1006 b3 = relative_square(us, SQ_B3);
1007 c3 = relative_square(us, SQ_C3);
1011 b2 = relative_square(us, SQ_G2);
1012 b3 = relative_square(us, SQ_G3);
1013 c3 = relative_square(us, SQ_F3);
1016 if (pos.piece_on(b2) == pawn)
1020 if (!pos.square_is_empty(b3))
1021 penalty = 2 * TrappedBishopA1H1Penalty;
1022 else if (pos.piece_on(c3) == pawn)
1023 penalty = TrappedBishopA1H1Penalty;
1025 penalty = TrappedBishopA1H1Penalty / 2;
1027 ei.value -= Sign[us] * penalty;
1032 // evaluate_space() computes the space evaluation for a given side. The
1033 // space evaluation is a simple bonus based on the number of safe squares
1034 // available for minor pieces on the central four files on ranks 2--4. Safe
1035 // squares one, two or three squares behind a friendly pawn are counted
1036 // twice. Finally, the space bonus is scaled by a weight taken from the
1037 // material hash table.
1038 template<Color Us, bool HasPopCnt>
1039 int evaluate_space(const Position& pos, EvalInfo& ei) {
1041 const Color Them = (Us == WHITE ? BLACK : WHITE);
1043 // Find the safe squares for our pieces inside the area defined by
1044 // SpaceMask[us]. A square is unsafe if it is attacked by an enemy
1045 // pawn, or if it is undefended and attacked by an enemy piece.
1046 Bitboard safe = SpaceMask[Us]
1047 & ~pos.pieces(PAWN, Us)
1048 & ~ei.attacked_by(Them, PAWN)
1049 & (ei.attacked_by(Us) | ~ei.attacked_by(Them));
1051 // Find all squares which are at most three squares behind some friendly pawn
1052 Bitboard behind = pos.pieces(PAWN, Us);
1053 behind |= (Us == WHITE ? behind >> 8 : behind << 8);
1054 behind |= (Us == WHITE ? behind >> 16 : behind << 16);
1056 return count_1s_max_15<HasPopCnt>(safe) + count_1s_max_15<HasPopCnt>(behind & safe);
1060 // apply_weight() applies an evaluation weight to a value trying to prevent overflow
1062 inline Score apply_weight(Score v, Score w) {
1063 return make_score((int(mg_value(v)) * mg_value(w)) / 0x100, (int(eg_value(v)) * eg_value(w)) / 0x100);
1067 // scale_by_game_phase() interpolates between a middle game and an endgame score,
1068 // based on game phase. It also scales the return value by a ScaleFactor array.
1070 Value scale_by_game_phase(const Score& v, Phase ph, const ScaleFactor sf[]) {
1072 assert(mg_value(v) > -VALUE_INFINITE && mg_value(v) < VALUE_INFINITE);
1073 assert(eg_value(v) > -VALUE_INFINITE && eg_value(v) < VALUE_INFINITE);
1074 assert(ph >= PHASE_ENDGAME && ph <= PHASE_MIDGAME);
1076 Value eg = eg_value(v);
1077 ScaleFactor f = sf[eg > Value(0) ? WHITE : BLACK];
1078 Value ev = Value((eg * int(f)) / SCALE_FACTOR_NORMAL);
1080 int result = (mg_value(v) * int(ph) + ev * int(128 - ph)) / 128;
1081 return Value(result & ~(GrainSize - 1));
1085 // weight_option() computes the value of an evaluation weight, by combining
1086 // two UCI-configurable weights (midgame and endgame) with an internal weight.
1088 Score weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight) {
1090 // Scale option value from 100 to 256
1091 int mg = get_option_value_int(mgOpt) * 256 / 100;
1092 int eg = get_option_value_int(egOpt) * 256 / 100;
1094 return apply_weight(make_score(mg, eg), internalWeight);
1097 // init_safety() initizes the king safety evaluation, based on UCI
1098 // parameters. It is called from read_weights().
1100 void init_safety() {
1102 const Value MaxSlope = Value(30);
1103 const Value Peak = Value(1280);
1106 // First setup the base table
1107 for (int i = 0; i < 100; i++)
1109 t[i] = Value(int(0.4 * i * i));
1112 t[i] = Min(t[i], t[i - 1] + MaxSlope);
1114 t[i] = Min(t[i], Peak);
1117 // Then apply the weights and get the final KingDangerTable[] array
1118 for (Color c = WHITE; c <= BLACK; c++)
1119 for (int i = 0; i < 100; i++)
1120 KingDangerTable[c][i] = apply_weight(make_score(t[i], 0), Weights[KingDangerUs + c]);