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/>.
34 #include "ucioption.h"
38 //// Local definitions
43 const int Sign[2] = { 1, -1 };
45 // Evaluation grain size, must be a power of 2
46 const int GrainSize = 8;
48 // Evaluation weights, initialized from UCI options
49 Score WeightMobility, WeightPawnStructure;
50 Score WeightPassedPawns, WeightSpace;
51 Score WeightKingSafety[2];
53 // Internal evaluation weights. These are applied on top of the evaluation
54 // weights read from UCI parameters. The purpose is to be able to change
55 // the evaluation weights while keeping the default values of the UCI
56 // parameters at 100, which looks prettier.
58 // Values modified by Joona Kiiski
59 const Score WeightMobilityInternal = make_score(248, 271);
60 const Score WeightPawnStructureInternal = make_score(233, 201);
61 const Score WeightPassedPawnsInternal = make_score(252, 259);
62 const Score WeightSpaceInternal = make_score( 46, 0);
63 const Score WeightKingSafetyInternal = make_score(247, 0);
64 const Score WeightKingOppSafetyInternal = make_score(259, 0);
66 // Mobility and outposts bonus modified by Joona Kiiski
69 #define S(mg, eg) make_score(mg, eg)
73 // Knight mobility bonus in middle game and endgame, indexed by the number
74 // of attacked squares not occupied by friendly piecess.
75 const Score KnightMobilityBonus[16] = {
76 S(-38,-33), S(-25,-23), S(-12,-13), S( 0,-3),
77 S( 12, 7), S( 25, 17), S( 31, 22), S(38, 27), S(38, 27)
80 // Bishop mobility bonus in middle game and endgame, indexed by the number
81 // of attacked squares not occupied by friendly pieces. X-ray attacks through
82 // queens are also included.
83 const Score BishopMobilityBonus[16] = {
84 S(-25,-30), S(-11,-16), S( 3, -2), S(17, 12),
85 S( 31, 26), S( 45, 40), S(57, 52), S(65, 60),
86 S( 71, 65), S( 74, 69), S(76, 71), S(78, 73),
87 S( 79, 74), S( 80, 75), S(81, 76), S(81, 76)
90 // Rook mobility bonus in middle game and endgame, indexed by the number
91 // of attacked squares not occupied by friendly pieces. X-ray attacks through
92 // queens and rooks are also included.
93 const Score RookMobilityBonus[16] = {
94 S(-20,-36), S(-14,-19), S(-8, -3), S(-2, 13),
95 S( 4, 29), S( 10, 46), S(14, 62), S(19, 79),
96 S( 23, 95), S( 26,106), S(27,111), S(28,114),
97 S( 29,116), S( 30,117), S(31,118), S(32,118)
100 // Queen mobility bonus in middle game and endgame, indexed by the number
101 // of attacked squares not occupied by friendly pieces.
102 const Score QueenMobilityBonus[32] = {
103 S(-10,-18), S(-8,-13), S(-6, -7), S(-3, -2), S(-1, 3), S( 1, 8),
104 S( 3, 13), S( 5, 19), S( 8, 23), S(10, 27), S(12, 32), S(15, 34),
105 S( 16, 35), S(17, 35), S(18, 35), S(20, 35), S(20, 35), S(20, 35),
106 S( 20, 35), S(20, 35), S(20, 35), S(20, 35), S(20, 35), S(20, 35),
107 S( 20, 35), S(20, 35), S(20, 35), S(20, 35), S(20, 35), S(20, 35),
108 S( 20, 35), S(20, 35)
111 // Pointers table to access mobility tables through piece type
112 const Score* MobilityBonus[8] = { 0, 0, KnightMobilityBonus, BishopMobilityBonus,
113 RookMobilityBonus, QueenMobilityBonus, 0, 0 };
115 // Outpost bonuses for knights and bishops, indexed by square (from white's
117 const Value KnightOutpostBonus[64] = {
119 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 1
120 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 2
121 V(0), V(0), V(4), V(8), V(8), V(4), V(0), V(0), // 3
122 V(0), V(4),V(17),V(26),V(26),V(17), V(4), V(0), // 4
123 V(0), V(8),V(26),V(35),V(35),V(26), V(8), V(0), // 5
124 V(0), V(4),V(17),V(17),V(17),V(17), V(4), V(0), // 6
125 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 7
126 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0) // 8
129 const Value BishopOutpostBonus[64] = {
131 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 1
132 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 2
133 V(0), V(0), V(5), V(5), V(5), V(5), V(0), V(0), // 3
134 V(0), V(5),V(10),V(10),V(10),V(10), V(5), V(0), // 4
135 V(0),V(10),V(21),V(21),V(21),V(21),V(10), V(0), // 5
136 V(0), V(5), V(8), V(8), V(8), V(8), V(5), V(0), // 6
137 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 7
138 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0) // 8
141 // ThreatBonus[][] contains bonus according to which piece type
142 // attacks which one.
145 const Score ThreatBonus[8][8] = {
146 { Z, Z, Z, Z, Z, Z, Z, Z }, // not used
147 { Z, S(18,37), Z, S(37,47), S(55,97), S(55,97), Z, Z }, // KNIGHT attacks
148 { Z, S(18,37), S(37,47), Z, S(55,97), S(55,97), Z, Z }, // BISHOP attacks
149 { Z, S( 9,27), S(27,47), S(27,47), Z, S(37,47), Z, Z }, // ROOK attacks
150 { Z, S(27,37), S(27,37), S(27,37), S(27,37), Z, Z, Z }, // QUEEN attacks
151 { Z, Z, Z, Z, Z, Z, Z, Z }, // not used
152 { Z, Z, Z, Z, Z, Z, Z, Z }, // not used
153 { Z, Z, Z, Z, Z, Z, Z, Z } // not used
156 // ThreatedByPawnPenalty[] contains a penalty according to which piece
157 // type is attacked by an enemy pawn.
158 const Score ThreatedByPawnPenalty[8] = {
159 Z, Z, S(56, 70), S(56, 70), S(76, 99), S(86, 118), Z, Z
165 // Bonus for unstoppable passed pawns
166 const Value UnstoppablePawnValue = Value(0x500);
168 // Rooks and queens on the 7th rank (modified by Joona Kiiski)
169 const Score RookOn7thBonus = make_score(47, 98);
170 const Score QueenOn7thBonus = make_score(27, 54);
172 // Rooks on open files (modified by Joona Kiiski)
173 const Score RookOpenFileBonus = make_score(43, 43);
174 const Score RookHalfOpenFileBonus = make_score(19, 19);
176 // Penalty for rooks trapped inside a friendly king which has lost the
178 const Value TrappedRookPenalty = Value(180);
180 // Penalty for a bishop on a7/h7 (a2/h2 for black) which is trapped by
182 const Score TrappedBishopA7H7Penalty = make_score(300, 300);
184 // Bitboard masks for detecting trapped bishops on a7/h7 (a2/h2 for black)
185 const Bitboard MaskA7H7[2] = {
186 ((1ULL << SQ_A7) | (1ULL << SQ_H7)),
187 ((1ULL << SQ_A2) | (1ULL << SQ_H2))
190 // Penalty for a bishop on a1/h1 (a8/h8 for black) which is trapped by
191 // a friendly pawn on b2/g2 (b7/g7 for black). This can obviously only
192 // happen in Chess960 games.
193 const Score TrappedBishopA1H1Penalty = make_score(100, 100);
195 // Bitboard masks for detecting trapped bishops on a1/h1 (a8/h8 for black)
196 const Bitboard MaskA1H1[2] = {
197 ((1ULL << SQ_A1) | (1ULL << SQ_H1)),
198 ((1ULL << SQ_A8) | (1ULL << SQ_H8))
201 // The SpaceMask[color] contains the area of the board which is considered
202 // by the space evaluation. In the middle game, each side is given a bonus
203 // based on how many squares inside this area are safe and available for
204 // friendly minor pieces.
205 const Bitboard SpaceMask[2] = {
206 (1ULL<<SQ_C2) | (1ULL<<SQ_D2) | (1ULL<<SQ_E2) | (1ULL<<SQ_F2) |
207 (1ULL<<SQ_C3) | (1ULL<<SQ_D3) | (1ULL<<SQ_E3) | (1ULL<<SQ_F3) |
208 (1ULL<<SQ_C4) | (1ULL<<SQ_D4) | (1ULL<<SQ_E4) | (1ULL<<SQ_F4),
209 (1ULL<<SQ_C7) | (1ULL<<SQ_D7) | (1ULL<<SQ_E7) | (1ULL<<SQ_F7) |
210 (1ULL<<SQ_C6) | (1ULL<<SQ_D6) | (1ULL<<SQ_E6) | (1ULL<<SQ_F6) |
211 (1ULL<<SQ_C5) | (1ULL<<SQ_D5) | (1ULL<<SQ_E5) | (1ULL<<SQ_F5)
214 /// King safety constants and variables. The king safety scores are taken
215 /// from the array SafetyTable[]. Various little "meta-bonuses" measuring
216 /// the strength of the attack are added up into an integer, which is used
217 /// as an index to SafetyTable[].
219 // Attack weights for each piece type and table indexed on piece type
220 const int QueenAttackWeight = 5;
221 const int RookAttackWeight = 3;
222 const int BishopAttackWeight = 2;
223 const int KnightAttackWeight = 2;
225 const int AttackWeight[] = { 0, 0, KnightAttackWeight, BishopAttackWeight, RookAttackWeight, QueenAttackWeight };
227 // Bonuses for safe checks
228 const int QueenContactCheckBonus = 3;
229 const int DiscoveredCheckBonus = 3;
230 const int QueenCheckBonus = 2;
231 const int RookCheckBonus = 1;
232 const int BishopCheckBonus = 1;
233 const int KnightCheckBonus = 1;
235 // Scan for queen contact mates?
236 const bool QueenContactMates = true;
238 // Bonus for having a mate threat
239 const int MateThreatBonus = 3;
241 // InitKingDanger[] contains bonuses based on the position of the defending
243 const int InitKingDanger[64] = {
244 2, 0, 2, 5, 5, 2, 0, 2,
245 2, 2, 4, 8, 8, 4, 2, 2,
246 7, 10, 12, 12, 12, 12, 10, 7,
247 15, 15, 15, 15, 15, 15, 15, 15,
248 15, 15, 15, 15, 15, 15, 15, 15,
249 15, 15, 15, 15, 15, 15, 15, 15,
250 15, 15, 15, 15, 15, 15, 15, 15,
251 15, 15, 15, 15, 15, 15, 15, 15
254 // SafetyTable[] contains the actual king safety scores. It is initialized
256 Value SafetyTable[100];
258 // Pawn and material hash tables, indexed by the current thread id.
259 // Note that they will be initialized at 0 being global variables.
260 MaterialInfoTable* MaterialTable[MAX_THREADS];
261 PawnInfoTable* PawnTable[MAX_THREADS];
263 // Sizes of pawn and material hash tables
264 const int PawnTableSize = 16384;
265 const int MaterialTableSize = 1024;
267 // Function prototypes
268 template<bool HasPopCnt>
269 Value do_evaluate(const Position& pos, EvalInfo& ei, int threadID);
271 template<Color Us, bool HasPopCnt>
272 void evaluate_pieces_of_color(const Position& pos, EvalInfo& ei);
274 template<Color Us, bool HasPopCnt>
275 void evaluate_king(const Position& pos, EvalInfo& ei);
278 void evaluate_threats(const Position& pos, EvalInfo& ei);
280 template<Color Us, bool HasPopCnt>
281 void evaluate_space(const Position& pos, EvalInfo& ei);
283 void evaluate_passed_pawns(const Position& pos, EvalInfo& ei);
284 void evaluate_trapped_bishop_a7h7(const Position& pos, Square s, Color us, EvalInfo& ei);
285 void evaluate_trapped_bishop_a1h1(const Position& pos, Square s, Color us, EvalInfo& ei);
286 inline Score apply_weight(Score v, Score weight);
287 Value scale_by_game_phase(const Score& v, Phase ph, const ScaleFactor sf[]);
288 Score weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight);
297 /// evaluate() is the main evaluation function. It always computes two
298 /// values, an endgame score and a middle game score, and interpolates
299 /// between them based on the remaining material.
300 Value evaluate(const Position& pos, EvalInfo& ei, int threadID) {
302 return CpuHasPOPCNT ? do_evaluate<true>(pos, ei, threadID)
303 : do_evaluate<false>(pos, ei, threadID);
308 template<bool HasPopCnt>
309 Value do_evaluate(const Position& pos, EvalInfo& ei, int threadID) {
312 assert(threadID >= 0 && threadID < MAX_THREADS);
313 assert(!pos.is_check());
315 memset(&ei, 0, sizeof(EvalInfo));
317 // Initialize by reading the incrementally updated scores included in the
318 // position object (material + piece square tables)
319 ei.value = pos.value();
321 // Probe the material hash table
322 ei.mi = MaterialTable[threadID]->get_material_info(pos);
323 ei.value += ei.mi->material_value();
325 // If we have a specialized evaluation function for the current material
326 // configuration, call it and return
327 if (ei.mi->specialized_eval_exists())
328 return ei.mi->evaluate(pos);
330 // After get_material_info() call that modifies them
331 ScaleFactor factor[2];
332 factor[WHITE] = ei.mi->scale_factor(pos, WHITE);
333 factor[BLACK] = ei.mi->scale_factor(pos, BLACK);
335 // Probe the pawn hash table
336 ei.pi = PawnTable[threadID]->get_pawn_info(pos);
337 ei.value += apply_weight(ei.pi->pawns_value(), WeightPawnStructure);
339 // Initialize king attack bitboards and king attack zones for both sides
340 ei.attackedBy[WHITE][KING] = pos.attacks_from<KING>(pos.king_square(WHITE));
341 ei.attackedBy[BLACK][KING] = pos.attacks_from<KING>(pos.king_square(BLACK));
342 ei.kingZone[WHITE] = ei.attackedBy[BLACK][KING] | (ei.attackedBy[BLACK][KING] >> 8);
343 ei.kingZone[BLACK] = ei.attackedBy[WHITE][KING] | (ei.attackedBy[WHITE][KING] << 8);
345 // Initialize pawn attack bitboards for both sides
346 ei.attackedBy[WHITE][PAWN] = ei.pi->pawn_attacks(WHITE);
347 ei.attackedBy[BLACK][PAWN] = ei.pi->pawn_attacks(BLACK);
348 Bitboard b1 = ei.attackedBy[WHITE][PAWN] & ei.attackedBy[BLACK][KING];
349 Bitboard b2 = ei.attackedBy[BLACK][PAWN] & ei.attackedBy[WHITE][KING];
351 ei.kingAttackersCount[WHITE] = count_1s_max_15<HasPopCnt>(b1)/2;
354 ei.kingAttackersCount[BLACK] = count_1s_max_15<HasPopCnt>(b2)/2;
357 evaluate_pieces_of_color<WHITE, HasPopCnt>(pos, ei);
358 evaluate_pieces_of_color<BLACK, HasPopCnt>(pos, ei);
360 // Kings. Kings are evaluated after all other pieces for both sides,
361 // because we need complete attack information for all pieces when computing
362 // the king safety evaluation.
363 evaluate_king<WHITE, HasPopCnt>(pos, ei);
364 evaluate_king<BLACK, HasPopCnt>(pos, ei);
366 // Evaluate tactical threats, we need full attack info
367 evaluate_threats<WHITE>(pos, ei);
368 evaluate_threats<BLACK>(pos, ei);
370 // Evaluate passed pawns. We evaluate passed pawns for both sides at once,
371 // because we need to know which side promotes first in positions where
372 // both sides have an unstoppable passed pawn. To be called after all attacks
373 // are computed, included king.
374 if (ei.pi->passed_pawns())
375 evaluate_passed_pawns(pos, ei);
377 Phase phase = ei.mi->game_phase();
379 // Middle-game specific evaluation terms
380 if (phase > PHASE_ENDGAME)
382 // Pawn storms in positions with opposite castling.
383 if ( square_file(pos.king_square(WHITE)) >= FILE_E
384 && square_file(pos.king_square(BLACK)) <= FILE_D)
386 ei.value += make_score(ei.pi->queenside_storm_value(WHITE) - ei.pi->kingside_storm_value(BLACK), 0);
388 else if ( square_file(pos.king_square(WHITE)) <= FILE_D
389 && square_file(pos.king_square(BLACK)) >= FILE_E)
391 ei.value += make_score(ei.pi->kingside_storm_value(WHITE) - ei.pi->queenside_storm_value(BLACK), 0);
393 // Evaluate space for both sides
394 if (ei.mi->space_weight() > 0)
396 evaluate_space<WHITE, HasPopCnt>(pos, ei);
397 evaluate_space<BLACK, HasPopCnt>(pos, ei);
402 ei.value += apply_weight(ei.mobility, WeightMobility);
404 // If we don't already have an unusual scale factor, check for opposite
405 // colored bishop endgames, and use a lower scale for those
406 if ( phase < PHASE_MIDGAME
407 && pos.opposite_colored_bishops()
408 && ( (factor[WHITE] == SCALE_FACTOR_NORMAL && eg_value(ei.value) > Value(0))
409 || (factor[BLACK] == SCALE_FACTOR_NORMAL && eg_value(ei.value) < Value(0))))
413 // Only the two bishops ?
414 if ( pos.non_pawn_material(WHITE) == BishopValueMidgame
415 && pos.non_pawn_material(BLACK) == BishopValueMidgame)
417 // Check for KBP vs KB with only a single pawn that is almost
418 // certainly a draw or at least two pawns.
419 bool one_pawn = (pos.piece_count(WHITE, PAWN) + pos.piece_count(BLACK, PAWN) == 1);
420 sf = one_pawn ? ScaleFactor(8) : ScaleFactor(32);
423 // Endgame with opposite-colored bishops, but also other pieces. Still
424 // a bit drawish, but not as drawish as with only the two bishops.
425 sf = ScaleFactor(50);
427 if (factor[WHITE] == SCALE_FACTOR_NORMAL)
429 if (factor[BLACK] == SCALE_FACTOR_NORMAL)
433 // If we don't already have an unusual scale factor, use pawn
435 if (factor[WHITE] == SCALE_FACTOR_NORMAL)
436 factor[WHITE] = ei.pi->scale_factor(WHITE);
437 if (factor[BLACK] == SCALE_FACTOR_NORMAL)
438 factor[BLACK] = ei.pi->scale_factor(BLACK);
440 // Interpolate between the middle game and the endgame score
441 Color stm = pos.side_to_move();
443 Value v = Sign[stm] * scale_by_game_phase(ei.value, phase, factor);
445 return (ei.mateThreat[stm] == MOVE_NONE ? v : 8 * QueenValueMidgame - v);
450 /// init_eval() initializes various tables used by the evaluation function
452 void init_eval(int threads) {
454 assert(threads <= MAX_THREADS);
456 for (int i = 0; i < MAX_THREADS; i++)
461 delete MaterialTable[i];
463 MaterialTable[i] = NULL;
467 PawnTable[i] = new PawnInfoTable(PawnTableSize);
468 if (!MaterialTable[i])
469 MaterialTable[i] = new MaterialInfoTable(MaterialTableSize);
474 /// quit_eval() releases heap-allocated memory at program termination
478 for (int i = 0; i < MAX_THREADS; i++)
481 delete MaterialTable[i];
483 MaterialTable[i] = NULL;
488 /// read_weights() reads evaluation weights from the corresponding UCI parameters
490 void read_weights(Color us) {
492 Color them = opposite_color(us);
494 WeightMobility = weight_option("Mobility (Middle Game)", "Mobility (Endgame)", WeightMobilityInternal);
495 WeightPawnStructure = weight_option("Pawn Structure (Middle Game)", "Pawn Structure (Endgame)", WeightPawnStructureInternal);
496 WeightPassedPawns = weight_option("Passed Pawns (Middle Game)", "Passed Pawns (Endgame)", WeightPassedPawnsInternal);
497 WeightSpace = weight_option("Space", "Space", WeightSpaceInternal);
498 WeightKingSafety[us] = weight_option("Cowardice", "Cowardice", WeightKingSafetyInternal);
499 WeightKingSafety[them] = weight_option("Aggressiveness", "Aggressiveness", WeightKingOppSafetyInternal);
501 // If running in analysis mode, make sure we use symmetrical king safety. We do this
502 // by replacing both WeightKingSafety[us] and WeightKingSafety[them] by their average.
503 if (get_option_value_bool("UCI_AnalyseMode"))
505 WeightKingSafety[us] = (WeightKingSafety[us] + WeightKingSafety[them]) / 2;
506 WeightKingSafety[them] = WeightKingSafety[us];
514 // evaluate_outposts() evaluates bishop and knight outposts squares
516 template<PieceType Piece, Color Us>
517 void evaluate_outposts(const Position& pos, EvalInfo& ei, Square s) {
519 const Color Them = (Us == WHITE ? BLACK : WHITE);
521 // Initial bonus based on square
522 Value bonus = (Piece == BISHOP ? BishopOutpostBonus[relative_square(Us, s)]
523 : KnightOutpostBonus[relative_square(Us, s)]);
525 // Increase bonus if supported by pawn, especially if the opponent has
526 // no minor piece which can exchange the outpost piece
527 if (bonus && bit_is_set(ei.attackedBy[Us][PAWN], s))
529 if ( pos.pieces(KNIGHT, Them) == EmptyBoardBB
530 && (SquaresByColorBB[square_color(s)] & pos.pieces(BISHOP, Them)) == EmptyBoardBB)
531 bonus += bonus + bonus / 2;
535 ei.value += Sign[Us] * make_score(bonus, bonus);
539 // evaluate_pieces<>() assigns bonuses and penalties to the pieces of a given color
541 template<PieceType Piece, Color Us, bool HasPopCnt>
542 void evaluate_pieces(const Position& pos, EvalInfo& ei, Bitboard no_mob_area) {
549 const Color Them = (Us == WHITE ? BLACK : WHITE);
550 const Square* ptr = pos.piece_list_begin(Us, Piece);
552 while ((s = *ptr++) != SQ_NONE)
554 // Find attacked squares, including x-ray attacks for bishops and rooks
555 if (Piece == KNIGHT || Piece == QUEEN)
556 b = pos.attacks_from<Piece>(s);
557 else if (Piece == BISHOP)
558 b = bishop_attacks_bb(s, pos.occupied_squares() & ~pos.pieces(QUEEN, Us));
559 else if (Piece == ROOK)
560 b = rook_attacks_bb(s, pos.occupied_squares() & ~pos.pieces(ROOK, QUEEN, Us));
564 // Update attack info
565 ei.attackedBy[Us][Piece] |= b;
568 if (b & ei.kingZone[Us])
570 ei.kingAttackersCount[Us]++;
571 ei.kingAttackersWeight[Us] += AttackWeight[Piece];
572 Bitboard bb = (b & ei.attackedBy[Them][KING]);
574 ei.kingAdjacentZoneAttacksCount[Us] += count_1s_max_15<HasPopCnt>(bb);
578 mob = (Piece != QUEEN ? count_1s_max_15<HasPopCnt>(b & no_mob_area)
579 : count_1s<HasPopCnt>(b & no_mob_area));
581 ei.mobility += Sign[Us] * MobilityBonus[Piece][mob];
583 // Decrease score if we are attacked by an enemy pawn. Remaining part
584 // of threat evaluation must be done later when we have full attack info.
585 if (bit_is_set(ei.attackedBy[Them][PAWN], s))
586 ei.value -= Sign[Us] * ThreatedByPawnPenalty[Piece];
588 // Bishop and knight outposts squares
589 if ((Piece == BISHOP || Piece == KNIGHT) && pos.square_is_weak(s, Them))
590 evaluate_outposts<Piece, Us>(pos, ei, s);
592 // Special patterns: trapped bishops on a7/h7/a2/h2
593 // and trapped bishops on a1/h1/a8/h8 in Chess960.
596 if (bit_is_set(MaskA7H7[Us], s))
597 evaluate_trapped_bishop_a7h7(pos, s, Us, ei);
599 if (Chess960 && bit_is_set(MaskA1H1[Us], s))
600 evaluate_trapped_bishop_a1h1(pos, s, Us, ei);
603 // Queen or rook on 7th rank
604 if ( (Piece == ROOK || Piece == QUEEN)
605 && relative_rank(Us, s) == RANK_7
606 && relative_rank(Us, pos.king_square(Them)) == RANK_8)
608 ei.value += Sign[Us] * (Piece == ROOK ? RookOn7thBonus : QueenOn7thBonus);
611 // Special extra evaluation for rooks
614 // Open and half-open files
616 if (ei.pi->file_is_half_open(Us, f))
618 if (ei.pi->file_is_half_open(Them, f))
619 ei.value += Sign[Us] * RookOpenFileBonus;
621 ei.value += Sign[Us] * RookHalfOpenFileBonus;
624 // Penalize rooks which are trapped inside a king. Penalize more if
625 // king has lost right to castle.
626 if (mob > 6 || ei.pi->file_is_half_open(Us, f))
629 ksq = pos.king_square(Us);
631 if ( square_file(ksq) >= FILE_E
632 && square_file(s) > square_file(ksq)
633 && (relative_rank(Us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
635 // Is there a half-open file between the king and the edge of the board?
636 if (!ei.pi->has_open_file_to_right(Us, square_file(ksq)))
637 ei.value -= Sign[Us] * make_score(pos.can_castle(Us) ? (TrappedRookPenalty - mob * 16) / 2
638 : (TrappedRookPenalty - mob * 16), 0);
640 else if ( square_file(ksq) <= FILE_D
641 && square_file(s) < square_file(ksq)
642 && (relative_rank(Us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
644 // Is there a half-open file between the king and the edge of the board?
645 if (!ei.pi->has_open_file_to_left(Us, square_file(ksq)))
646 ei.value -= Sign[Us] * make_score(pos.can_castle(Us) ? (TrappedRookPenalty - mob * 16) / 2
647 : (TrappedRookPenalty - mob * 16), 0);
654 // evaluate_threats<>() assigns bonuses according to the type of attacking piece
655 // and the type of attacked one.
658 void evaluate_threats(const Position& pos, EvalInfo& ei) {
660 const Color Them = (Us == WHITE ? BLACK : WHITE);
663 Score bonus = make_score(0, 0);
665 // Enemy pieces not defended by a pawn and under our attack
666 Bitboard weakEnemies = pos.pieces_of_color(Them)
667 & ~ei.attackedBy[Them][PAWN]
668 & ei.attackedBy[Us][0];
672 // Add bonus according to type of attacked enemy pieces and to the
673 // type of attacking piece, from knights to queens. Kings are not
674 // considered because are already special handled in king evaluation.
675 for (PieceType pt1 = KNIGHT; pt1 < KING; pt1++)
677 b = ei.attackedBy[Us][pt1] & weakEnemies;
679 for (PieceType pt2 = PAWN; pt2 < KING; pt2++)
680 if (b & pos.pieces(pt2))
681 bonus += ThreatBonus[pt1][pt2];
683 ei.value += Sign[Us] * bonus;
687 // evaluate_pieces_of_color<>() assigns bonuses and penalties to all the
688 // pieces of a given color.
690 template<Color Us, bool HasPopCnt>
691 void evaluate_pieces_of_color(const Position& pos, EvalInfo& ei) {
693 const Color Them = (Us == WHITE ? BLACK : WHITE);
695 // Do not include in mobility squares protected by enemy pawns or occupied by our pieces
696 const Bitboard no_mob_area = ~(ei.attackedBy[Them][PAWN] | pos.pieces_of_color(Us));
698 evaluate_pieces<KNIGHT, Us, HasPopCnt>(pos, ei, no_mob_area);
699 evaluate_pieces<BISHOP, Us, HasPopCnt>(pos, ei, no_mob_area);
700 evaluate_pieces<ROOK, Us, HasPopCnt>(pos, ei, no_mob_area);
701 evaluate_pieces<QUEEN, Us, HasPopCnt>(pos, ei, no_mob_area);
703 // Sum up all attacked squares
704 ei.attackedBy[Us][0] = ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
705 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
706 | ei.attackedBy[Us][QUEEN] | ei.attackedBy[Us][KING];
710 // evaluate_king<>() assigns bonuses and penalties to a king of a given color
712 template<Color Us, bool HasPopCnt>
713 void evaluate_king(const Position& pos, EvalInfo& ei) {
715 const Color Them = (Us == WHITE ? BLACK : WHITE);
717 Bitboard undefended, attackedByOthers, escapeSquares, occ, b, b2, safe;
720 int attackUnits, count, shelter = 0;
721 const Square s = pos.king_square(Us);
724 if (relative_rank(Us, s) <= RANK_4)
726 shelter = ei.pi->get_king_shelter(pos, Us, s);
727 ei.value += Sign[Us] * make_score(shelter, 0);
730 // King safety. This is quite complicated, and is almost certainly far
731 // from optimally tuned.
732 if ( pos.piece_count(Them, QUEEN) >= 1
733 && ei.kingAttackersCount[Them] >= 2
734 && pos.non_pawn_material(Them) >= QueenValueMidgame + RookValueMidgame
735 && ei.kingAdjacentZoneAttacksCount[Them])
737 // Is it the attackers turn to move?
738 sente = (Them == pos.side_to_move());
740 // Find the attacked squares around the king which has no defenders
741 // apart from the king itself
742 undefended = ei.attacked_by(Them) & ei.attacked_by(Us, KING);
743 undefended &= ~( ei.attacked_by(Us, PAWN) | ei.attacked_by(Us, KNIGHT)
744 | ei.attacked_by(Us, BISHOP) | ei.attacked_by(Us, ROOK)
745 | ei.attacked_by(Us, QUEEN));
747 // Initialize the 'attackUnits' variable, which is used later on as an
748 // index to the SafetyTable[] array. The initial value is based on the
749 // number and types of the attacking pieces, the number of attacked and
750 // undefended squares around the king, the square of the king, and the
751 // quality of the pawn shelter.
752 attackUnits = Min(25, (ei.kingAttackersCount[Them] * ei.kingAttackersWeight[Them]) / 2)
753 + 3 * (ei.kingAdjacentZoneAttacksCount[Them] + count_1s_max_15<HasPopCnt>(undefended))
754 + InitKingDanger[relative_square(Us, s)]
757 // Analyse safe queen contact checks
758 b = undefended & ei.attacked_by(Them, QUEEN) & ~pos.pieces_of_color(Them);
761 attackedByOthers = ei.attacked_by(Them, PAWN) | ei.attacked_by(Them, KNIGHT)
762 | ei.attacked_by(Them, BISHOP) | ei.attacked_by(Them, ROOK);
764 b &= attackedByOthers;
766 // Squares attacked by the queen and supported by another enemy piece and
767 // not defended by other pieces but our king.
770 // The bitboard b now contains the squares available for safe queen
772 count = count_1s_max_15<HasPopCnt>(b);
773 attackUnits += QueenContactCheckBonus * count * (sente ? 2 : 1);
775 // Is there a mate threat?
776 if (QueenContactMates && !pos.is_check())
778 escapeSquares = pos.attacks_from<KING>(s) & ~pos.pieces_of_color(Us) & ~attackedByOthers;
779 occ = pos.occupied_squares();
782 to = pop_1st_bit(&b);
784 // Do we have escape squares from queen contact check attack ?
785 if (!(escapeSquares & ~queen_attacks_bb(to, occ & ClearMaskBB[s])))
787 // We have a mate, unless the queen is pinned or there
788 // is an X-ray attack through the queen.
789 for (int i = 0; i < pos.piece_count(Them, QUEEN); i++)
791 from = pos.piece_list(Them, QUEEN, i);
792 if ( bit_is_set(pos.attacks_from<QUEEN>(from), to)
793 && !bit_is_set(pos.pinned_pieces(Them), from)
794 && !(rook_attacks_bb(to, occ & ClearMaskBB[from]) & pos.pieces(ROOK, QUEEN, Us))
795 && !(bishop_attacks_bb(to, occ & ClearMaskBB[from]) & pos.pieces(BISHOP, QUEEN, Us)))
797 // Set the mate threat move
798 ei.mateThreat[Them] = make_move(from, to);
806 // Analyse safe distance checks
807 safe = ~(pos.pieces_of_color(Them) | ei.attacked_by(Us));
809 if (QueenCheckBonus > 0 || RookCheckBonus > 0)
811 b = pos.attacks_from<ROOK>(s) & safe;
814 b2 = b & ei.attacked_by(Them, QUEEN);
816 attackUnits += QueenCheckBonus * count_1s_max_15<HasPopCnt>(b2);
819 b2 = b & ei.attacked_by(Them, ROOK);
821 attackUnits += RookCheckBonus * count_1s_max_15<HasPopCnt>(b2);
823 if (QueenCheckBonus > 0 || BishopCheckBonus > 0)
825 b = pos.attacks_from<BISHOP>(s) & safe;
828 b2 = b & ei.attacked_by(Them, QUEEN);
830 attackUnits += QueenCheckBonus * count_1s_max_15<HasPopCnt>(b2);
833 b2 = b & ei.attacked_by(Them, BISHOP);
835 attackUnits += BishopCheckBonus * count_1s_max_15<HasPopCnt>(b2);
837 if (KnightCheckBonus > 0)
839 b = pos.attacks_from<KNIGHT>(s) & safe;
842 b2 = b & ei.attacked_by(Them, KNIGHT);
844 attackUnits += KnightCheckBonus * count_1s_max_15<HasPopCnt>(b2);
847 // Analyse discovered checks (only for non-pawns right now, consider
848 // adding pawns later).
849 if (DiscoveredCheckBonus)
851 b = pos.discovered_check_candidates(Them) & ~pos.pieces(PAWN);
853 attackUnits += DiscoveredCheckBonus * count_1s_max_15<HasPopCnt>(b) * (sente ? 2 : 1);
856 // Has a mate threat been found? We don't do anything here if the
857 // side with the mating move is the side to move, because in that
858 // case the mating side will get a huge bonus at the end of the main
859 // evaluation function instead.
860 if (ei.mateThreat[Them] != MOVE_NONE)
861 attackUnits += MateThreatBonus;
863 // Ensure that attackUnits is between 0 and 99, in order to avoid array
864 // out of bounds errors.
865 attackUnits = Min(99, Max(0, attackUnits));
867 // Finally, extract the king safety score from the SafetyTable[] array.
868 // Add the score to the evaluation, and also to ei.futilityMargin. The
869 // reason for adding the king safety score to the futility margin is
870 // that the king safety scores can sometimes be very big, and that
871 // capturing a single attacking piece can therefore result in a score
872 // change far bigger than the value of the captured piece.
873 Score v = apply_weight(make_score(SafetyTable[attackUnits], 0), WeightKingSafety[Us]);
874 ei.value -= Sign[Us] * v;
875 ei.futilityMargin[Us] += mg_value(v);
880 // evaluate_passed_pawns_of_color() evaluates the passed pawns of the given color
883 void evaluate_passed_pawns_of_color(const Position& pos, int movesToGo[], Square pawnToGo[], EvalInfo& ei) {
885 const Color Them = (Us == WHITE ? BLACK : WHITE);
888 Square ourKingSq = pos.king_square(Us);
889 Square theirKingSq = pos.king_square(Them);
890 Bitboard b = ei.pi->passed_pawns() & pos.pieces(PAWN, Us);
894 Square s = pop_1st_bit(&b);
896 assert(pos.piece_on(s) == piece_of_color_and_type(Us, PAWN));
897 assert(pos.pawn_is_passed(Us, s));
899 int r = int(relative_rank(Us, s) - RANK_2);
900 int tr = Max(0, r * (r - 1));
902 // Base bonus based on rank
903 Value mbonus = Value(20 * tr);
904 Value ebonus = Value(10 + r * r * 10);
906 // Adjust bonus based on king proximity
909 Square blockSq = s + pawn_push(Us);
911 ebonus -= Value(square_distance(ourKingSq, blockSq) * 3 * tr);
912 ebonus -= Value(square_distance(ourKingSq, blockSq + pawn_push(Us)) * 1 * tr);
913 ebonus += Value(square_distance(theirKingSq, blockSq) * 6 * tr);
915 // If the pawn is free to advance, increase bonus
916 if (pos.square_is_empty(blockSq))
918 // There are no enemy pawns in the pawn's path
919 b2 = squares_in_front_of(Us, s);
921 assert((b2 & pos.pieces(PAWN, Them)) == EmptyBoardBB);
923 // Squares attacked by us
924 b4 = b2 & ei.attacked_by(Us);
926 // Squares attacked or occupied by enemy pieces
927 b3 = b2 & (ei.attacked_by(Them) | pos.pieces_of_color(Them));
929 // If there is an enemy rook or queen attacking the pawn from behind,
930 // add all X-ray attacks by the rook or queen.
931 if ( (squares_behind(Us, s) & pos.pieces(ROOK, QUEEN, Them))
932 && (squares_behind(Us, s) & pos.pieces(ROOK, QUEEN, Them) & pos.attacks_from<QUEEN>(s)))
935 // Are any of the squares in the pawn's path attacked or occupied by the enemy?
936 if (b3 == EmptyBoardBB)
937 // No enemy attacks or pieces, huge bonus!
938 // Even bigger if we protect the pawn's path
939 ebonus += Value(tr * (b2 == b4 ? 17 : 15));
941 // OK, there are enemy attacks or pieces (but not pawns). Are those
942 // squares which are attacked by the enemy also attacked by us ?
943 // If yes, big bonus (but smaller than when there are no enemy attacks),
944 // if no, somewhat smaller bonus.
945 ebonus += Value(tr * ((b3 & b4) == b3 ? 13 : 8));
947 // At last, add a small bonus when there are no *friendly* pieces
948 // in the pawn's path.
949 if ((b2 & pos.pieces_of_color(Us)) == EmptyBoardBB)
954 // If the pawn is supported by a friendly pawn, increase bonus
955 b2 = pos.pieces(PAWN, Us) & neighboring_files_bb(s);
957 ebonus += Value(r * 20);
958 else if (pos.attacks_from<PAWN>(s, Them) & b2)
959 ebonus += Value(r * 12);
961 // If the other side has only a king, check whether the pawn is
963 if (pos.non_pawn_material(Them) == Value(0))
968 qsq = relative_square(Us, make_square(square_file(s), RANK_8));
969 d = square_distance(s, qsq)
970 - square_distance(theirKingSq, qsq)
971 + int(Us != pos.side_to_move());
975 int mtg = RANK_8 - relative_rank(Us, s);
976 int blockerCount = count_1s_max_15(squares_in_front_of(Us,s) & pos.occupied_squares());
979 if (d < 0 && (!movesToGo[Us] || movesToGo[Us] > mtg))
987 // Rook pawns are a special case: They are sometimes worse, and
988 // sometimes better than other passed pawns. It is difficult to find
989 // good rules for determining whether they are good or bad. For now,
990 // we try the following: Increase the value for rook pawns if the
991 // other side has no pieces apart from a knight, and decrease the
992 // value if the other side has a rook or queen.
993 if (square_file(s) == FILE_A || square_file(s) == FILE_H)
995 if ( pos.non_pawn_material(Them) <= KnightValueMidgame
996 && pos.piece_count(Them, KNIGHT) <= 1)
997 ebonus += ebonus / 4;
998 else if (pos.pieces(ROOK, QUEEN, Them))
999 ebonus -= ebonus / 4;
1002 // Add the scores for this pawn to the middle game and endgame eval.
1003 ei.value += Sign[Us] * apply_weight(make_score(mbonus, ebonus), WeightPassedPawns);
1009 // evaluate_passed_pawns() evaluates the passed pawns for both sides
1011 void evaluate_passed_pawns(const Position& pos, EvalInfo& ei) {
1013 int movesToGo[2] = {0, 0};
1014 Square pawnToGo[2] = {SQ_NONE, SQ_NONE};
1016 // Evaluate pawns for each color
1017 evaluate_passed_pawns_of_color<WHITE>(pos, movesToGo, pawnToGo, ei);
1018 evaluate_passed_pawns_of_color<BLACK>(pos, movesToGo, pawnToGo, ei);
1020 // Neither side has an unstoppable passed pawn?
1021 if (!(movesToGo[WHITE] | movesToGo[BLACK]))
1024 // Does only one side have an unstoppable passed pawn?
1025 if (!movesToGo[WHITE] || !movesToGo[BLACK])
1027 Color winnerSide = movesToGo[WHITE] ? WHITE : BLACK;
1028 ei.value += make_score(0, Sign[winnerSide] * (UnstoppablePawnValue - Value(0x40 * movesToGo[winnerSide])));
1031 { // Both sides have unstoppable pawns! Try to find out who queens
1032 // first. We begin by transforming 'movesToGo' to the number of
1033 // plies until the pawn queens for both sides.
1034 movesToGo[WHITE] *= 2;
1035 movesToGo[BLACK] *= 2;
1036 movesToGo[pos.side_to_move()]--;
1038 Color winnerSide = movesToGo[WHITE] < movesToGo[BLACK] ? WHITE : BLACK;
1039 Color loserSide = opposite_color(winnerSide);
1041 // If one side queens at least three plies before the other, that side wins
1042 if (movesToGo[winnerSide] <= movesToGo[loserSide] - 3)
1043 ei.value += Sign[winnerSide] * make_score(0, UnstoppablePawnValue - Value(0x40 * (movesToGo[winnerSide]/2)));
1045 // If one side queens one ply before the other and checks the king or attacks
1046 // the undefended opponent's queening square, that side wins. To avoid cases
1047 // where the opponent's king could move somewhere before first pawn queens we
1048 // consider only free paths to queen for both pawns.
1049 else if ( !(squares_in_front_of(WHITE, pawnToGo[WHITE]) & pos.occupied_squares())
1050 && !(squares_in_front_of(BLACK, pawnToGo[BLACK]) & pos.occupied_squares()))
1052 assert(movesToGo[loserSide] - movesToGo[winnerSide] == 1);
1054 Square winnerQSq = relative_square(winnerSide, make_square(square_file(pawnToGo[winnerSide]), RANK_8));
1055 Square loserQSq = relative_square(loserSide, make_square(square_file(pawnToGo[loserSide]), RANK_8));
1057 Bitboard b = pos.occupied_squares();
1058 clear_bit(&b, pawnToGo[winnerSide]);
1059 clear_bit(&b, pawnToGo[loserSide]);
1060 b = queen_attacks_bb(winnerQSq, b);
1062 if ( (b & pos.pieces(KING, loserSide))
1063 ||(bit_is_set(b, loserQSq) && !bit_is_set(ei.attacked_by(loserSide), loserQSq)))
1064 ei.value += Sign[winnerSide] * make_score(0, UnstoppablePawnValue - Value(0x40 * (movesToGo[winnerSide]/2)));
1070 // evaluate_trapped_bishop_a7h7() determines whether a bishop on a7/h7
1071 // (a2/h2 for black) is trapped by enemy pawns, and assigns a penalty
1074 void evaluate_trapped_bishop_a7h7(const Position& pos, Square s, Color us, EvalInfo &ei) {
1076 assert(square_is_ok(s));
1077 assert(pos.piece_on(s) == piece_of_color_and_type(us, BISHOP));
1079 Square b6 = relative_square(us, (square_file(s) == FILE_A) ? SQ_B6 : SQ_G6);
1080 Square b8 = relative_square(us, (square_file(s) == FILE_A) ? SQ_B8 : SQ_G8);
1082 if ( pos.piece_on(b6) == piece_of_color_and_type(opposite_color(us), PAWN)
1083 && pos.see(s, b6) < 0
1084 && pos.see(s, b8) < 0)
1086 ei.value -= Sign[us] * TrappedBishopA7H7Penalty;
1091 // evaluate_trapped_bishop_a1h1() determines whether a bishop on a1/h1
1092 // (a8/h8 for black) is trapped by a friendly pawn on b2/g2 (b7/g7 for
1093 // black), and assigns a penalty if it is. This pattern can obviously
1094 // only occur in Chess960 games.
1096 void evaluate_trapped_bishop_a1h1(const Position& pos, Square s, Color us, EvalInfo& ei) {
1098 Piece pawn = piece_of_color_and_type(us, PAWN);
1102 assert(square_is_ok(s));
1103 assert(pos.piece_on(s) == piece_of_color_and_type(us, BISHOP));
1105 if (square_file(s) == FILE_A)
1107 b2 = relative_square(us, SQ_B2);
1108 b3 = relative_square(us, SQ_B3);
1109 c3 = relative_square(us, SQ_C3);
1113 b2 = relative_square(us, SQ_G2);
1114 b3 = relative_square(us, SQ_G3);
1115 c3 = relative_square(us, SQ_F3);
1118 if (pos.piece_on(b2) == pawn)
1122 if (!pos.square_is_empty(b3))
1123 penalty = 2 * TrappedBishopA1H1Penalty;
1124 else if (pos.piece_on(c3) == pawn)
1125 penalty = TrappedBishopA1H1Penalty;
1127 penalty = TrappedBishopA1H1Penalty / 2;
1129 ei.value -= Sign[us] * penalty;
1134 // evaluate_space() computes the space evaluation for a given side. The
1135 // space evaluation is a simple bonus based on the number of safe squares
1136 // available for minor pieces on the central four files on ranks 2--4. Safe
1137 // squares one, two or three squares behind a friendly pawn are counted
1138 // twice. Finally, the space bonus is scaled by a weight taken from the
1139 // material hash table.
1140 template<Color Us, bool HasPopCnt>
1141 void evaluate_space(const Position& pos, EvalInfo& ei) {
1143 const Color Them = (Us == WHITE ? BLACK : WHITE);
1145 // Find the safe squares for our pieces inside the area defined by
1146 // SpaceMask[us]. A square is unsafe if it is attacked by an enemy
1147 // pawn, or if it is undefended and attacked by an enemy piece.
1149 Bitboard safeSquares = SpaceMask[Us]
1150 & ~pos.pieces(PAWN, Us)
1151 & ~ei.attacked_by(Them, PAWN)
1152 & ~(~ei.attacked_by(Us) & ei.attacked_by(Them));
1154 // Find all squares which are at most three squares behind some friendly
1156 Bitboard behindFriendlyPawns = pos.pieces(PAWN, Us);
1157 behindFriendlyPawns |= (Us == WHITE ? behindFriendlyPawns >> 8 : behindFriendlyPawns << 8);
1158 behindFriendlyPawns |= (Us == WHITE ? behindFriendlyPawns >> 16 : behindFriendlyPawns << 16);
1160 int space = count_1s_max_15<HasPopCnt>(safeSquares)
1161 + count_1s_max_15<HasPopCnt>(behindFriendlyPawns & safeSquares);
1163 ei.value += Sign[Us] * apply_weight(make_score(space * ei.mi->space_weight(), 0), WeightSpace);
1167 // apply_weight() applies an evaluation weight to a value trying to prevent overflow
1169 inline Score apply_weight(Score v, Score w) {
1170 return make_score((int(mg_value(v)) * mg_value(w)) / 0x100, (int(eg_value(v)) * eg_value(w)) / 0x100);
1174 // scale_by_game_phase() interpolates between a middle game and an endgame
1175 // score, based on game phase. It also scales the return value by a
1176 // ScaleFactor array.
1178 Value scale_by_game_phase(const Score& v, Phase ph, const ScaleFactor sf[]) {
1180 assert(mg_value(v) > -VALUE_INFINITE && mg_value(v) < VALUE_INFINITE);
1181 assert(eg_value(v) > -VALUE_INFINITE && eg_value(v) < VALUE_INFINITE);
1182 assert(ph >= PHASE_ENDGAME && ph <= PHASE_MIDGAME);
1184 Value ev = apply_scale_factor(eg_value(v), sf[(eg_value(v) > Value(0) ? WHITE : BLACK)]);
1186 int result = (mg_value(v) * ph + ev * (128 - ph)) / 128;
1187 return Value(result & ~(GrainSize - 1));
1191 // weight_option() computes the value of an evaluation weight, by combining
1192 // two UCI-configurable weights (midgame and endgame) with an internal weight.
1194 Score weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight) {
1196 Score uciWeight = make_score(get_option_value_int(mgOpt), get_option_value_int(egOpt));
1198 // Convert to integer to prevent overflow
1199 int mg = mg_value(uciWeight);
1200 int eg = eg_value(uciWeight);
1202 mg = (mg * 0x100) / 100;
1203 eg = (eg * 0x100) / 100;
1204 mg = (mg * mg_value(internalWeight)) / 0x100;
1205 eg = (eg * eg_value(internalWeight)) / 0x100;
1206 return make_score(mg, eg);
1209 // init_safety() initizes the king safety evaluation, based on UCI
1210 // parameters. It is called from read_weights().
1212 void init_safety() {
1219 for (int i = 0; i < 100; i++)
1222 SafetyTable[i] = Value(0);
1224 SafetyTable[i] = Value((int)(a * (i - b) * (i - b)));
1227 for (int i = 1; i < 100; i++)
1229 if (SafetyTable[i] - SafetyTable[i - 1] > maxSlope)
1230 SafetyTable[i] = SafetyTable[i - 1] + Value(maxSlope);
1232 if (SafetyTable[i] > Value(peak))
1233 SafetyTable[i] = Value(peak);