2 Stockfish, a UCI chess playing engine derived from Glaurung 2.1
3 Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
4 Copyright (C) 2008-2009 Marco Costalba
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 = 4;
48 // Evaluation weights, initialized from UCI options
49 int WeightMobilityMidgame, WeightMobilityEndgame;
50 int WeightPawnStructureMidgame, WeightPawnStructureEndgame;
51 int WeightPassedPawnsMidgame, WeightPassedPawnsEndgame;
52 int WeightKingSafety[2];
55 // Internal evaluation weights. These are applied on top of the evaluation
56 // weights read from UCI parameters. The purpose is to be able to change
57 // the evaluation weights while keeping the default values of the UCI
58 // parameters at 100, which looks prettier.
60 // Values modified by Joona Kiiski
61 const int WeightMobilityMidgameInternal = 248;
62 const int WeightMobilityEndgameInternal = 271;
63 const int WeightPawnStructureMidgameInternal = 233;
64 const int WeightPawnStructureEndgameInternal = 201;
65 const int WeightPassedPawnsMidgameInternal = 252;
66 const int WeightPassedPawnsEndgameInternal = 259;
67 const int WeightKingSafetyInternal = 247;
68 const int WeightKingOppSafetyInternal = 259;
69 const int WeightSpaceInternal = 46;
71 // Mobility and outposts bonus modified by Joona Kiiski
73 // Visually better to define tables constants
76 // Knight mobility bonus in middle game and endgame, indexed by the number
77 // of attacked squares not occupied by friendly piecess.
78 const Value MidgameKnightMobilityBonus[] = {
80 V(-38), V(-25),V(-12), V(0), V(12), V(25), V(31), V(38), V(38)
83 const Value EndgameKnightMobilityBonus[] = {
85 V(-33), V(-23),V(-13), V(-3), V(7), V(17), V(22), V(27), V(27)
88 // Bishop mobility bonus in middle game and endgame, indexed by the number
89 // of attacked squares not occupied by friendly pieces. X-ray attacks through
90 // queens are also included.
91 const Value MidgameBishopMobilityBonus[] = {
93 V(-25), V(-11), V(3), V(17), V(31), V(45), V(57), V(65),
94 // 8 9 10 11 12 13 14 15
95 V( 71), V( 74), V(76), V(78), V(79), V(80), V(81), V(81)
98 const Value EndgameBishopMobilityBonus[] = {
100 V(-30), V(-16), V(-2), V(12), V(26), V(40), V(52), V(60),
101 // 8 9 10 11 12 13 14 15
102 V( 65), V( 69), V(71), V(73), V(74), V(75), V(76), V(76)
105 // Rook mobility bonus in middle game and endgame, indexed by the number
106 // of attacked squares not occupied by friendly pieces. X-ray attacks through
107 // queens and rooks are also included.
108 const Value MidgameRookMobilityBonus[] = {
110 V(-20), V(-14), V(-8), V(-2), V(4), V(10), V(14), V(19),
111 // 8 9 10 11 12 13 14 15
112 V( 23), V( 26), V(27), V(28), V(29), V(30), V(31), V(32)
115 const Value EndgameRookMobilityBonus[] = {
117 V(-36), V(-19), V(-3), V(13), V(29), V(46), V(62), V(79),
118 // 8 9 10 11 12 13 14 15
119 V( 95), V(106),V(111),V(114),V(116),V(117),V(118),V(118)
122 // Queen mobility bonus in middle game and endgame, indexed by the number
123 // of attacked squares not occupied by friendly pieces.
124 const Value MidgameQueenMobilityBonus[] = {
126 V(-10), V(-8), V(-6), V(-3), V(-1), V( 1), V( 3), V( 5),
127 // 8 9 10 11 12 13 14 15
128 V( 8), V(10), V(12), V(15), V(16), V(17), V(18), V(20),
129 // 16 17 18 19 20 21 22 23
130 V( 20), V(20), V(20), V(20), V(20), V(20), V(20), V(20),
131 // 24 25 26 27 28 29 30 31
132 V( 20), V(20), V(20), V(20), V(20), V(20), V(20), V(20)
135 const Value EndgameQueenMobilityBonus[] = {
137 V(-18),V(-13), V(-7), V(-2), V( 3), V (8), V(13), V(19),
138 // 8 9 10 11 12 13 14 15
139 V( 23), V(27), V(32), V(34), V(35), V(35), V(35), V(35),
140 // 16 17 18 19 20 21 22 23
141 V( 35), V(35), V(35), V(35), V(35), V(35), V(35), V(35),
142 // 24 25 26 27 28 29 30 31
143 V( 35), V(35), V(35), V(35), V(35), V(35), V(35), V(35)
146 // Outpost bonuses for knights and bishops, indexed by square (from white's
148 const Value KnightOutpostBonus[64] = {
150 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 1
151 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 2
152 V(0), V(0), V(4), V(8), V(8), V(4), V(0), V(0), // 3
153 V(0), V(4),V(17),V(26),V(26),V(17), V(4), V(0), // 4
154 V(0), V(8),V(26),V(35),V(35),V(26), V(8), V(0), // 5
155 V(0), V(4),V(17),V(17),V(17),V(17), V(4), V(0), // 6
156 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 7
157 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0) // 8
160 const Value BishopOutpostBonus[64] = {
162 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 1
163 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 2
164 V(0), V(0), V(5), V(5), V(5), V(5), V(0), V(0), // 3
165 V(0), V(5),V(10),V(10),V(10),V(10), V(5), V(0), // 4
166 V(0),V(10),V(21),V(21),V(21),V(21),V(10), V(0), // 5
167 V(0), V(5), V(8), V(8), V(8), V(8), V(5), V(0), // 6
168 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 7
169 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0) // 8
172 // Bonus for unstoppable passed pawns
173 const Value UnstoppablePawnValue = Value(0x500);
175 // Rooks and queens on the 7th rank (modified by Joona Kiiski)
176 const Value MidgameRookOn7thBonus = Value(47);
177 const Value EndgameRookOn7thBonus = Value(98);
178 const Value MidgameQueenOn7thBonus = Value(27);
179 const Value EndgameQueenOn7thBonus = Value(54);
181 // Rooks on open files (modified by Joona Kiiski)
182 const Value RookOpenFileBonus = Value(43);
183 const Value RookHalfOpenFileBonus = Value(19);
185 // Penalty for rooks trapped inside a friendly king which has lost the
187 const Value TrappedRookPenalty = Value(180);
189 // Penalty for a bishop on a7/h7 (a2/h2 for black) which is trapped by
191 const Value TrappedBishopA7H7Penalty = Value(300);
193 // Bitboard masks for detecting trapped bishops on a7/h7 (a2/h2 for black)
194 const Bitboard MaskA7H7[2] = {
195 ((1ULL << SQ_A7) | (1ULL << SQ_H7)),
196 ((1ULL << SQ_A2) | (1ULL << SQ_H2))
199 // Penalty for a bishop on a1/h1 (a8/h8 for black) which is trapped by
200 // a friendly pawn on b2/g2 (b7/g7 for black). This can obviously only
201 // happen in Chess960 games.
202 const Value TrappedBishopA1H1Penalty = Value(100);
204 // Bitboard masks for detecting trapped bishops on a1/h1 (a8/h8 for black)
205 const Bitboard MaskA1H1[2] = {
206 ((1ULL << SQ_A1) | (1ULL << SQ_H1)),
207 ((1ULL << SQ_A8) | (1ULL << SQ_H8))
210 // The SpaceMask[color] contains area of the board which is consdered by
211 // the space evaluation. In the middle game, each side is given a bonus
212 // based on how many squares inside this area are safe and available for
213 // friendly minor pieces.
214 const Bitboard SpaceMask[2] = {
215 (1ULL<<SQ_C2) | (1ULL<<SQ_D2) | (1ULL<<SQ_E2) | (1ULL<<SQ_F2) |
216 (1ULL<<SQ_C3) | (1ULL<<SQ_D3) | (1ULL<<SQ_E3) | (1ULL<<SQ_F3) |
217 (1ULL<<SQ_C4) | (1ULL<<SQ_D4) | (1ULL<<SQ_E4) | (1ULL<<SQ_F4),
218 (1ULL<<SQ_C7) | (1ULL<<SQ_D7) | (1ULL<<SQ_E7) | (1ULL<<SQ_F7) |
219 (1ULL<<SQ_C6) | (1ULL<<SQ_D6) | (1ULL<<SQ_E6) | (1ULL<<SQ_F6) |
220 (1ULL<<SQ_C5) | (1ULL<<SQ_D5) | (1ULL<<SQ_E5) | (1ULL<<SQ_F5)
223 /// King safety constants and variables. The king safety scores are taken
224 /// from the array SafetyTable[]. Various little "meta-bonuses" measuring
225 /// the strength of the attack are added up into an integer, which is used
226 /// as an index to SafetyTable[].
228 // Attack weights for each piece type
229 const int QueenAttackWeight = 5;
230 const int RookAttackWeight = 3;
231 const int BishopAttackWeight = 2;
232 const int KnightAttackWeight = 2;
234 // Bonuses for safe checks, initialized from UCI options
235 int QueenContactCheckBonus, DiscoveredCheckBonus;
236 int QueenCheckBonus, RookCheckBonus, BishopCheckBonus, KnightCheckBonus;
238 // Scan for queen contact mates?
239 const bool QueenContactMates = true;
241 // Bonus for having a mate threat, initialized from UCI options
244 // InitKingDanger[] contains bonuses based on the position of the defending
246 const int InitKingDanger[64] = {
247 2, 0, 2, 5, 5, 2, 0, 2,
248 2, 2, 4, 8, 8, 4, 2, 2,
249 7, 10, 12, 12, 12, 12, 10, 7,
250 15, 15, 15, 15, 15, 15, 15, 15,
251 15, 15, 15, 15, 15, 15, 15, 15,
252 15, 15, 15, 15, 15, 15, 15, 15,
253 15, 15, 15, 15, 15, 15, 15, 15,
254 15, 15, 15, 15, 15, 15, 15, 15
257 // SafetyTable[] contains the actual king safety scores. It is initialized
259 Value SafetyTable[100];
261 // Pawn and material hash tables, indexed by the current thread id
262 PawnInfoTable* PawnTable[8] = {0, 0, 0, 0, 0, 0, 0, 0};
263 MaterialInfoTable* MaterialTable[8] = {0, 0, 0, 0, 0, 0, 0, 0};
265 // Sizes of pawn and material hash tables
266 const int PawnTableSize = 16384;
267 const int MaterialTableSize = 1024;
269 // Function prototypes
270 template<bool HasPopCnt>
271 Value do_evaluate(const Position& pos, EvalInfo& ei, int threadID);
273 template<PieceType Piece, bool HasPopCnt>
274 void evaluate_pieces(const Position& p, Color us, EvalInfo& ei);
276 template<bool HasPopCnt>
277 void evaluate_king(const Position& p, Color us, EvalInfo &ei);
279 void evaluate_passed_pawns(const Position &pos, EvalInfo &ei);
280 void evaluate_trapped_bishop_a7h7(const Position &pos, Square s, Color us,
282 void evaluate_trapped_bishop_a1h1(const Position &pos, Square s, Color us,
284 template<bool HasPopCnt>
285 void evaluate_space(const Position &p, Color us, EvalInfo &ei);
286 inline Value apply_weight(Value v, int w);
287 Value scale_by_game_phase(Value mv, Value ev, Phase ph, const ScaleFactor sf[]);
289 int compute_weight(int uciWeight, int internalWeight);
290 int weight_option(const std::string& opt, int weight);
300 /// evaluate() is the main evaluation function. It always computes two
301 /// values, an endgame score and a middle game score, and interpolates
302 /// between them based on the remaining material.
303 Value evaluate(const Position& pos, EvalInfo& ei, int threadID) {
305 return CpuHasPOPCNT ? do_evaluate<true>(pos, ei, threadID)
306 : do_evaluate<false>(pos, ei, threadID);
311 template<bool HasPopCnt>
312 Value do_evaluate(const Position& pos, EvalInfo& ei, int threadID) {
315 assert(threadID >= 0 && threadID < THREAD_MAX);
317 memset(&ei, 0, sizeof(EvalInfo));
319 // Initialize by reading the incrementally updated scores included in the
320 // position object (material + piece square tables)
321 ei.mgValue = pos.mg_value();
322 ei.egValue = pos.eg_value();
324 // Probe the material hash table
325 ei.mi = MaterialTable[threadID]->get_material_info(pos);
326 ei.mgValue += ei.mi->material_value();
327 ei.egValue += ei.mi->material_value();
329 // If we have a specialized evaluation function for the current material
330 // configuration, call it and return
331 if (ei.mi->specialized_eval_exists())
332 return ei.mi->evaluate(pos);
334 // After get_material_info() call that modifies them
335 ScaleFactor factor[2];
336 factor[WHITE] = ei.mi->scale_factor(pos, WHITE);
337 factor[BLACK] = ei.mi->scale_factor(pos, BLACK);
339 // Probe the pawn hash table
340 ei.pi = PawnTable[threadID]->get_pawn_info(pos);
341 ei.mgValue += apply_weight(ei.pi->mg_value(), WeightPawnStructureMidgame);
342 ei.egValue += apply_weight(ei.pi->eg_value(), WeightPawnStructureEndgame);
344 // Initialize king attack bitboards and king attack zones for both sides
345 ei.attackedBy[WHITE][KING] = pos.piece_attacks<KING>(pos.king_square(WHITE));
346 ei.attackedBy[BLACK][KING] = pos.piece_attacks<KING>(pos.king_square(BLACK));
347 ei.kingZone[WHITE] = ei.attackedBy[BLACK][KING] | (ei.attackedBy[BLACK][KING] >> 8);
348 ei.kingZone[BLACK] = ei.attackedBy[WHITE][KING] | (ei.attackedBy[WHITE][KING] << 8);
350 // Initialize pawn attack bitboards for both sides
351 ei.attackedBy[WHITE][PAWN] = ((pos.pawns(WHITE) << 9) & ~FileABB) | ((pos.pawns(WHITE) << 7) & ~FileHBB);
352 ei.attackedBy[BLACK][PAWN] = ((pos.pawns(BLACK) >> 7) & ~FileABB) | ((pos.pawns(BLACK) >> 9) & ~FileHBB);
353 Bitboard b1 = ei.attackedBy[WHITE][PAWN] & ei.attackedBy[BLACK][KING];
354 Bitboard b2 = ei.attackedBy[BLACK][PAWN] & ei.attackedBy[WHITE][KING];
356 ei.kingAttackersCount[WHITE] = count_1s_max_15<HasPopCnt>(b1)/2;
359 ei.kingAttackersCount[BLACK] = count_1s_max_15<HasPopCnt>(b2)/2;
362 for (Color c = WHITE; c <= BLACK; c++)
364 evaluate_pieces<KNIGHT, HasPopCnt>(pos, c, ei);
365 evaluate_pieces<BISHOP, HasPopCnt>(pos, c, ei);
366 evaluate_pieces<ROOK, HasPopCnt>(pos, c, ei);
367 evaluate_pieces<QUEEN, HasPopCnt>(pos, c, ei);
369 // Sum up all attacked squares
370 ei.attackedBy[c][0] = ei.attackedBy[c][PAWN] | ei.attackedBy[c][KNIGHT]
371 | ei.attackedBy[c][BISHOP] | ei.attackedBy[c][ROOK]
372 | ei.attackedBy[c][QUEEN] | ei.attackedBy[c][KING];
375 // Kings. Kings are evaluated after all other pieces for both sides,
376 // because we need complete attack information for all pieces when computing
377 // the king safety evaluation.
378 for (Color c = WHITE; c <= BLACK; c++)
379 evaluate_king<HasPopCnt>(pos, c, ei);
381 // Evaluate passed pawns. We evaluate passed pawns for both sides at once,
382 // because we need to know which side promotes first in positions where
383 // both sides have an unstoppable passed pawn.
384 if (ei.pi->passed_pawns())
385 evaluate_passed_pawns(pos, ei);
387 Phase phase = pos.game_phase();
389 // Middle-game specific evaluation terms
390 if (phase > PHASE_ENDGAME)
392 // Pawn storms in positions with opposite castling.
393 if ( square_file(pos.king_square(WHITE)) >= FILE_E
394 && square_file(pos.king_square(BLACK)) <= FILE_D)
396 ei.mgValue += ei.pi->queenside_storm_value(WHITE)
397 - ei.pi->kingside_storm_value(BLACK);
399 else if ( square_file(pos.king_square(WHITE)) <= FILE_D
400 && square_file(pos.king_square(BLACK)) >= FILE_E)
402 ei.mgValue += ei.pi->kingside_storm_value(WHITE)
403 - ei.pi->queenside_storm_value(BLACK);
405 // Evaluate space for both sides
406 if (ei.mi->space_weight() > 0)
408 evaluate_space<HasPopCnt>(pos, WHITE, ei);
409 evaluate_space<HasPopCnt>(pos, BLACK, ei);
414 ei.mgValue += apply_weight(ei.mgMobility, WeightMobilityMidgame);
415 ei.egValue += apply_weight(ei.egMobility, WeightMobilityEndgame);
417 // If we don't already have an unusual scale factor, check for opposite
418 // colored bishop endgames, and use a lower scale for those
419 if ( phase < PHASE_MIDGAME
420 && pos.opposite_colored_bishops()
421 && ( (factor[WHITE] == SCALE_FACTOR_NORMAL && ei.egValue > Value(0))
422 || (factor[BLACK] == SCALE_FACTOR_NORMAL && ei.egValue < Value(0))))
426 // Only the two bishops ?
427 if ( pos.non_pawn_material(WHITE) == BishopValueMidgame
428 && pos.non_pawn_material(BLACK) == BishopValueMidgame)
430 // Check for KBP vs KB with only a single pawn that is almost
431 // certainly a draw or at least two pawns.
432 bool one_pawn = (pos.piece_count(WHITE, PAWN) + pos.piece_count(BLACK, PAWN) == 1);
433 sf = one_pawn ? ScaleFactor(8) : ScaleFactor(32);
436 // Endgame with opposite-colored bishops, but also other pieces. Still
437 // a bit drawish, but not as drawish as with only the two bishops.
438 sf = ScaleFactor(50);
440 if (factor[WHITE] == SCALE_FACTOR_NORMAL)
442 if (factor[BLACK] == SCALE_FACTOR_NORMAL)
446 // Interpolate between the middle game and the endgame score, and
448 Color stm = pos.side_to_move();
450 Value v = Sign[stm] * scale_by_game_phase(ei.mgValue, ei.egValue, phase, factor);
452 return (ei.mateThreat[stm] == MOVE_NONE ? v : 8 * QueenValueMidgame - v);
457 /// quick_evaluate() does a very approximate evaluation of the current position.
458 /// It currently considers only material and piece square table scores. Perhaps
459 /// we should add scores from the pawn and material hash tables?
461 Value quick_evaluate(const Position &pos) {
466 ScaleFactor sf[2] = {SCALE_FACTOR_NORMAL, SCALE_FACTOR_NORMAL};
468 Value mgv = pos.mg_value();
469 Value egv = pos.eg_value();
470 Phase ph = pos.game_phase();
471 Color stm = pos.side_to_move();
473 return Sign[stm] * scale_by_game_phase(mgv, egv, ph, sf);
477 /// init_eval() initializes various tables used by the evaluation function.
479 void init_eval(int threads) {
481 assert(threads <= THREAD_MAX);
483 for (int i = 0; i < THREAD_MAX; i++)
488 delete MaterialTable[i];
490 MaterialTable[i] = NULL;
494 PawnTable[i] = new PawnInfoTable(PawnTableSize);
495 if (!MaterialTable[i])
496 MaterialTable[i] = new MaterialInfoTable(MaterialTableSize);
501 /// quit_eval() releases heap-allocated memory at program termination.
505 for (int i = 0; i < THREAD_MAX; i++)
508 delete MaterialTable[i];
510 MaterialTable[i] = NULL;
515 /// read_weights() reads evaluation weights from the corresponding UCI
518 void read_weights(Color us) {
520 WeightMobilityMidgame = weight_option("Mobility (Middle Game)", WeightMobilityMidgameInternal);
521 WeightMobilityEndgame = weight_option("Mobility (Endgame)", WeightMobilityEndgameInternal);
522 WeightPawnStructureMidgame = weight_option("Pawn Structure (Middle Game)", WeightPawnStructureMidgameInternal);
523 WeightPawnStructureEndgame = weight_option("Pawn Structure (Endgame)", WeightPawnStructureEndgameInternal);
524 WeightPassedPawnsMidgame = weight_option("Passed Pawns (Middle Game)", WeightPassedPawnsMidgameInternal);
525 WeightPassedPawnsEndgame = weight_option("Passed Pawns (Endgame)", WeightPassedPawnsEndgameInternal);
527 Color them = opposite_color(us);
529 WeightKingSafety[us] = weight_option("Cowardice", WeightKingSafetyInternal);
530 WeightKingSafety[them] = weight_option("Aggressiveness", WeightKingOppSafetyInternal);
531 // If running in analysis mode, make sure we use symmetrical king safety.
532 // We do this by replacing both WeightKingSafety[us] and
533 // WeightKingSafety[them] by their average.
534 if (get_option_value_bool("UCI_AnalyseMode")) {
535 WeightKingSafety[us] = (WeightKingSafety[us] + WeightKingSafety[them]) / 2;
536 WeightKingSafety[them] = WeightKingSafety[us];
539 WeightSpace = weight_option("Space", WeightSpaceInternal);
547 // evaluate_mobility() computes mobility and attacks for every piece
549 template<PieceType Piece, bool HasPopCnt>
550 int evaluate_mobility(const Position& p, const Bitboard& b, Color us, Color them, EvalInfo& ei) {
552 static const int AttackWeight[] = { 0, 0, KnightAttackWeight, BishopAttackWeight, RookAttackWeight, QueenAttackWeight };
553 static const Value* MgBonus[] = { 0, 0, MidgameKnightMobilityBonus, MidgameBishopMobilityBonus, MidgameRookMobilityBonus, MidgameQueenMobilityBonus };
554 static const Value* EgBonus[] = { 0, 0, EndgameKnightMobilityBonus, EndgameBishopMobilityBonus, EndgameRookMobilityBonus, EndgameQueenMobilityBonus };
556 // Update attack info
557 ei.attackedBy[us][Piece] |= b;
560 if (b & ei.kingZone[us])
562 ei.kingAttackersCount[us]++;
563 ei.kingAttackersWeight[us] += AttackWeight[Piece];
564 Bitboard bb = (b & ei.attackedBy[them][KING]);
566 ei.kingAdjacentZoneAttacksCount[us] += count_1s_max_15<HasPopCnt>(bb);
569 // Remove squares protected by enemy pawns
570 Bitboard bb = (b & ~ei.attackedBy[them][PAWN]);
573 int mob = (Piece != QUEEN ? count_1s_max_15<HasPopCnt>(bb & ~p.pieces_of_color(us))
574 : count_1s<HasPopCnt>(bb & ~p.pieces_of_color(us)));
576 ei.mgMobility += Sign[us] * MgBonus[Piece][mob];
577 ei.egMobility += Sign[us] * EgBonus[Piece][mob];
582 // evaluate_outposts() evaluates bishop and knight outposts squares
584 template<PieceType Piece>
585 void evaluate_outposts(const Position& p, Color us, Color them, EvalInfo& ei, Square s) {
587 // Initial bonus based on square
588 Value bonus = (Piece == BISHOP ? BishopOutpostBonus[relative_square(us, s)]
589 : KnightOutpostBonus[relative_square(us, s)]);
591 // Increase bonus if supported by pawn, especially if the opponent has
592 // no minor piece which can exchange the outpost piece
593 if (bonus && (p.pawn_attacks(them, s) & p.pawns(us)))
595 if ( p.knights(them) == EmptyBoardBB
596 && (SquaresByColorBB[square_color(s)] & p.bishops(them)) == EmptyBoardBB)
597 bonus += bonus + bonus / 2;
601 ei.mgValue += Sign[us] * bonus;
602 ei.egValue += Sign[us] * bonus;
606 // evaluate_pieces<>() assigns bonuses and penalties to the pieces of a given
609 template<PieceType Piece, bool HasPopCnt>
610 void evaluate_pieces(const Position& pos, Color us, EvalInfo& ei) {
616 Color them = opposite_color(us);
618 for (int i = 0, e = pos.piece_count(us, Piece); i < e; i++)
620 s = pos.piece_list(us, Piece, i);
622 if (Piece == KNIGHT || Piece == QUEEN)
623 b = pos.piece_attacks<Piece>(s);
624 else if (Piece == BISHOP)
625 b = bishop_attacks_bb(s, pos.occupied_squares() & ~pos.queens(us));
626 else if (Piece == ROOK)
627 b = rook_attacks_bb(s, pos.occupied_squares() & ~pos.rooks_and_queens(us));
631 // Attacks and mobility
632 mob = evaluate_mobility<Piece, HasPopCnt>(pos, b, us, them, ei);
634 // Bishop and knight outposts squares
635 if ((Piece == BISHOP || Piece == KNIGHT) && pos.square_is_weak(s, them))
636 evaluate_outposts<Piece>(pos, us, them, ei, s);
638 // Special patterns: trapped bishops on a7/h7/a2/h2
639 // and trapped bishops on a1/h1/a8/h8 in Chess960.
642 if (bit_is_set(MaskA7H7[us], s))
643 evaluate_trapped_bishop_a7h7(pos, s, us, ei);
645 if (Chess960 && bit_is_set(MaskA1H1[us], s))
646 evaluate_trapped_bishop_a1h1(pos, s, us, ei);
649 if (Piece == ROOK || Piece == QUEEN)
651 // Queen or rook on 7th rank
652 if ( relative_rank(us, s) == RANK_7
653 && relative_rank(us, pos.king_square(them)) == RANK_8)
655 ei.mgValue += Sign[us] * (Piece == ROOK ? MidgameRookOn7thBonus : MidgameQueenOn7thBonus);
656 ei.egValue += Sign[us] * (Piece == ROOK ? EndgameRookOn7thBonus : EndgameQueenOn7thBonus);
660 // Special extra evaluation for rooks
663 // Open and half-open files
665 if (ei.pi->file_is_half_open(us, f))
667 if (ei.pi->file_is_half_open(them, f))
669 ei.mgValue += Sign[us] * RookOpenFileBonus;
670 ei.egValue += Sign[us] * RookOpenFileBonus;
674 ei.mgValue += Sign[us] * RookHalfOpenFileBonus;
675 ei.egValue += Sign[us] * RookHalfOpenFileBonus;
679 // Penalize rooks which are trapped inside a king. Penalize more if
680 // king has lost right to castle.
681 if (mob > 6 || ei.pi->file_is_half_open(us, f))
684 ksq = pos.king_square(us);
686 if ( square_file(ksq) >= FILE_E
687 && square_file(s) > square_file(ksq)
688 && (relative_rank(us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
690 // Is there a half-open file between the king and the edge of the board?
691 if (!ei.pi->has_open_file_to_right(us, square_file(ksq)))
692 ei.mgValue -= pos.can_castle(us)? Sign[us] * ((TrappedRookPenalty - mob * 16) / 2)
693 : Sign[us] * (TrappedRookPenalty - mob * 16);
695 else if ( square_file(ksq) <= FILE_D
696 && square_file(s) < square_file(ksq)
697 && (relative_rank(us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
699 // Is there a half-open file between the king and the edge of the board?
700 if (!ei.pi->has_open_file_to_left(us, square_file(ksq)))
701 ei.mgValue -= pos.can_castle(us)? Sign[us] * ((TrappedRookPenalty - mob * 16) / 2)
702 : Sign[us] * (TrappedRookPenalty - mob * 16);
709 // evaluate_king<>() assigns bonuses and penalties to a king of a given color.
711 template<bool HasPopCnt>
712 void evaluate_king(const Position& p, Color us, EvalInfo& ei) {
714 int shelter = 0, sign = Sign[us];
715 Square s = p.king_square(us);
718 if (relative_rank(us, s) <= RANK_4)
720 shelter = ei.pi->get_king_shelter(p, us, s);
721 ei.mgValue += sign * Value(shelter);
724 // King safety. This is quite complicated, and is almost certainly far
725 // from optimally tuned.
726 Color them = opposite_color(us);
728 if ( p.piece_count(them, QUEEN) >= 1
729 && ei.kingAttackersCount[them] >= 2
730 && p.non_pawn_material(them) >= QueenValueMidgame + RookValueMidgame
731 && ei.kingAdjacentZoneAttacksCount[them])
733 // Is it the attackers turn to move?
734 bool sente = (them == p.side_to_move());
736 // Find the attacked squares around the king which has no defenders
737 // apart from the king itself
738 Bitboard undefended =
739 ei.attacked_by(them) & ~ei.attacked_by(us, PAWN)
740 & ~ei.attacked_by(us, KNIGHT) & ~ei.attacked_by(us, BISHOP)
741 & ~ei.attacked_by(us, ROOK) & ~ei.attacked_by(us, QUEEN)
742 & ei.attacked_by(us, KING);
744 Bitboard occ = p.occupied_squares(), b, b2;
746 // Initialize the 'attackUnits' variable, which is used later on as an
747 // index to the SafetyTable[] array. The initial value is based on the
748 // number and types of the attacking pieces, the number of attacked and
749 // undefended squares around the king, the square of the king, and the
750 // quality of the pawn shelter.
752 Min((ei.kingAttackersCount[them] * ei.kingAttackersWeight[them]) / 2, 25)
753 + (ei.kingAdjacentZoneAttacksCount[them] + count_1s_max_15<HasPopCnt>(undefended)) * 3
754 + InitKingDanger[relative_square(us, s)] - (shelter >> 5);
756 // Analyse safe queen contact checks
757 b = undefended & ei.attacked_by(them, QUEEN) & ~p.pieces_of_color(them);
760 Bitboard attackedByOthers =
761 ei.attacked_by(them, PAWN) | ei.attacked_by(them, KNIGHT)
762 | ei.attacked_by(them, BISHOP) | ei.attacked_by(them, ROOK);
764 b &= attackedByOthers;
767 // The bitboard b now contains the squares available for safe queen
769 int count = count_1s_max_15<HasPopCnt>(b);
770 attackUnits += QueenContactCheckBonus * count * (sente ? 2 : 1);
772 // Is there a mate threat?
773 if (QueenContactMates && !p.is_check())
775 Bitboard escapeSquares =
776 p.piece_attacks<KING>(s) & ~p.pieces_of_color(us) & ~attackedByOthers;
780 Square from, to = pop_1st_bit(&b);
781 if (!(escapeSquares & ~queen_attacks_bb(to, occ & ClearMaskBB[s])))
783 // We have a mate, unless the queen is pinned or there
784 // is an X-ray attack through the queen.
785 for (int i = 0; i < p.piece_count(them, QUEEN); i++)
787 from = p.piece_list(them, QUEEN, i);
788 if ( bit_is_set(p.piece_attacks<QUEEN>(from), to)
789 && !bit_is_set(p.pinned_pieces(them), from)
790 && !(rook_attacks_bb(to, occ & ClearMaskBB[from]) & p.rooks_and_queens(us))
791 && !(bishop_attacks_bb(to, occ & ClearMaskBB[from]) & p.bishops_and_queens(us)))
793 ei.mateThreat[them] = make_move(from, to);
801 // Analyse safe distance checks
802 if (QueenCheckBonus > 0 || RookCheckBonus > 0)
804 b = p.piece_attacks<ROOK>(s) & ~p.pieces_of_color(them) & ~ei.attacked_by(us);
807 b2 = b & ei.attacked_by(them, QUEEN);
809 attackUnits += QueenCheckBonus * count_1s_max_15<HasPopCnt>(b2);
812 b2 = b & ei.attacked_by(them, ROOK);
814 attackUnits += RookCheckBonus * count_1s_max_15<HasPopCnt>(b2);
816 if (QueenCheckBonus > 0 || BishopCheckBonus > 0)
818 b = p.piece_attacks<BISHOP>(s) & ~p.pieces_of_color(them) & ~ei.attacked_by(us);
821 b2 = b & ei.attacked_by(them, QUEEN);
823 attackUnits += QueenCheckBonus * count_1s_max_15<HasPopCnt>(b2);
826 b2 = b & ei.attacked_by(them, BISHOP);
828 attackUnits += BishopCheckBonus * count_1s_max_15<HasPopCnt>(b2);
830 if (KnightCheckBonus > 0)
832 b = p.piece_attacks<KNIGHT>(s) & ~p.pieces_of_color(them) & ~ei.attacked_by(us);
835 b2 = b & ei.attacked_by(them, KNIGHT);
837 attackUnits += KnightCheckBonus * count_1s_max_15<HasPopCnt>(b2);
840 // Analyse discovered checks (only for non-pawns right now, consider
841 // adding pawns later).
842 if (DiscoveredCheckBonus)
844 b = p.discovered_check_candidates(them) & ~p.pawns();
846 attackUnits += DiscoveredCheckBonus * count_1s_max_15<HasPopCnt>(b) * (sente? 2 : 1);
849 // Has a mate threat been found? We don't do anything here if the
850 // side with the mating move is the side to move, because in that
851 // case the mating side will get a huge bonus at the end of the main
852 // evaluation function instead.
853 if (ei.mateThreat[them] != MOVE_NONE)
854 attackUnits += MateThreatBonus;
856 // Ensure that attackUnits is between 0 and 99, in order to avoid array
857 // out of bounds errors:
861 if (attackUnits >= 100)
864 // Finally, extract the king safety score from the SafetyTable[] array.
865 // Add the score to the evaluation, and also to ei.futilityMargin. The
866 // reason for adding the king safety score to the futility margin is
867 // that the king safety scores can sometimes be very big, and that
868 // capturing a single attacking piece can therefore result in a score
869 // change far bigger than the value of the captured piece.
870 Value v = apply_weight(SafetyTable[attackUnits], WeightKingSafety[us]);
872 ei.mgValue -= sign * v;
874 if (us == p.side_to_move())
875 ei.futilityMargin += v;
880 // evaluate_passed_pawns() evaluates the passed pawns for both sides.
882 void evaluate_passed_pawns(const Position &pos, EvalInfo &ei) {
884 bool hasUnstoppable[2] = {false, false};
885 int movesToGo[2] = {100, 100};
887 for (Color us = WHITE; us <= BLACK; us++)
889 Color them = opposite_color(us);
890 Square ourKingSq = pos.king_square(us);
891 Square theirKingSq = pos.king_square(them);
892 Bitboard b = ei.pi->passed_pawns() & pos.pawns(us), b2, b3, b4;
896 Square s = pop_1st_bit(&b);
898 assert(pos.piece_on(s) == piece_of_color_and_type(us, PAWN));
899 assert(pos.pawn_is_passed(us, s));
901 int r = int(relative_rank(us, s) - RANK_2);
902 int tr = Max(0, r * (r - 1));
903 Square blockSq = s + pawn_push(us);
905 // Base bonus based on rank
906 Value mbonus = Value(20 * tr);
907 Value ebonus = Value(10 + r * r * 10);
909 // Adjust bonus based on king proximity
912 ebonus -= Value(square_distance(ourKingSq, blockSq) * 3 * tr);
913 ebonus -= Value(square_distance(ourKingSq, blockSq + pawn_push(us)) * 1 * tr);
914 ebonus += Value(square_distance(theirKingSq, blockSq) * 6 * tr);
916 // If the pawn is free to advance, increase bonus
917 if (pos.square_is_empty(blockSq))
919 b2 = squares_in_front_of(us, s);
920 b3 = b2 & ei.attacked_by(them);
921 b4 = b2 & ei.attacked_by(us);
923 // If there is an enemy rook or queen attacking the pawn from behind,
924 // add all X-ray attacks by the rook or queen.
925 if ( bit_is_set(ei.attacked_by(them,ROOK) | ei.attacked_by(them,QUEEN),s)
926 && (squares_behind(us, s) & pos.rooks_and_queens(them)))
929 // Squares attacked or occupied by enemy pieces
930 b3 |= (b2 & pos.pieces_of_color(them));
932 // There are no enemy pawns in the pawn's path
933 assert((b2 & pos.pieces_of_color_and_type(them, PAWN)) == EmptyBoardBB);
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 ebonus += Value(tr * (b2 == b4 ? 17 : 15));
940 // OK, there are enemy attacks or pieces (but not pawns). Are those
941 // squares which are attacked by the enemy also attacked by us?
942 // If yes, big bonus (but smaller than when there are no enemy attacks),
943 // if no, somewhat smaller bonus.
944 ebonus += Value(tr * ((b3 & b4) == b3 ? 13 : 8));
946 // At last, add a small bonus when there are no *friendly* pieces
947 // in the pawn's path.
948 if ((b2 & pos.pieces_of_color(us)) == EmptyBoardBB)
953 // If the pawn is supported by a friendly pawn, increase bonus
954 b2 = pos.pawns(us) & neighboring_files_bb(s);
956 ebonus += Value(r * 20);
957 else if (pos.pawn_attacks(them, s) & b2)
958 ebonus += Value(r * 12);
960 // If the other side has only a king, check whether the pawn is
962 if (pos.non_pawn_material(them) == Value(0))
967 qsq = relative_square(us, make_square(square_file(s), RANK_8));
968 d = square_distance(s, qsq)
969 - square_distance(theirKingSq, qsq)
970 + (us != pos.side_to_move());
974 int mtg = RANK_8 - relative_rank(us, s);
975 int blockerCount = count_1s_max_15(squares_in_front_of(us,s) & pos.occupied_squares());
980 hasUnstoppable[us] = true;
981 movesToGo[us] = Min(movesToGo[us], mtg);
985 // Rook pawns are a special case: They are sometimes worse, and
986 // sometimes better than other passed pawns. It is difficult to find
987 // good rules for determining whether they are good or bad. For now,
988 // we try the following: Increase the value for rook pawns if the
989 // other side has no pieces apart from a knight, and decrease the
990 // value if the other side has a rook or queen.
991 if (square_file(s) == FILE_A || square_file(s) == FILE_H)
993 if ( pos.non_pawn_material(them) <= KnightValueMidgame
994 && pos.piece_count(them, KNIGHT) <= 1)
995 ebonus += ebonus / 4;
996 else if (pos.rooks_and_queens(them))
997 ebonus -= ebonus / 4;
1000 // Add the scores for this pawn to the middle game and endgame eval.
1001 ei.mgValue += apply_weight(Sign[us] * mbonus, WeightPassedPawnsMidgame);
1002 ei.egValue += apply_weight(Sign[us] * ebonus, WeightPassedPawnsEndgame);
1006 // Does either side have an unstoppable passed pawn?
1007 if (hasUnstoppable[WHITE] && !hasUnstoppable[BLACK])
1008 ei.egValue += UnstoppablePawnValue - Value(0x40 * movesToGo[WHITE]);
1009 else if (hasUnstoppable[BLACK] && !hasUnstoppable[WHITE])
1010 ei.egValue -= UnstoppablePawnValue - Value(0x40 * movesToGo[BLACK]);
1011 else if (hasUnstoppable[BLACK] && hasUnstoppable[WHITE])
1013 // Both sides have unstoppable pawns! Try to find out who queens
1014 // first. We begin by transforming 'movesToGo' to the number of
1015 // plies until the pawn queens for both sides.
1016 movesToGo[WHITE] *= 2;
1017 movesToGo[BLACK] *= 2;
1018 movesToGo[pos.side_to_move()]--;
1020 // If one side queens at least three plies before the other, that
1022 if (movesToGo[WHITE] <= movesToGo[BLACK] - 3)
1023 ei.egValue += UnstoppablePawnValue - Value(0x40 * (movesToGo[WHITE]/2));
1024 else if(movesToGo[BLACK] <= movesToGo[WHITE] - 3)
1025 ei.egValue -= UnstoppablePawnValue - Value(0x40 * (movesToGo[BLACK]/2));
1027 // We could also add some rules about the situation when one side
1028 // queens exactly one ply before the other: Does the first queen
1029 // check the opponent's king, or attack the opponent's queening square?
1030 // This is slightly tricky to get right, because it is possible that
1031 // the opponent's king has moved somewhere before the first pawn queens.
1036 // evaluate_trapped_bishop_a7h7() determines whether a bishop on a7/h7
1037 // (a2/h2 for black) is trapped by enemy pawns, and assigns a penalty
1040 void evaluate_trapped_bishop_a7h7(const Position &pos, Square s, Color us,
1042 assert(square_is_ok(s));
1043 assert(pos.piece_on(s) == piece_of_color_and_type(us, BISHOP));
1045 Square b6 = relative_square(us, (square_file(s) == FILE_A) ? SQ_B6 : SQ_G6);
1046 Square b8 = relative_square(us, (square_file(s) == FILE_A) ? SQ_B8 : SQ_G8);
1048 if ( pos.piece_on(b6) == piece_of_color_and_type(opposite_color(us), PAWN)
1049 && pos.see(s, b6) < 0
1050 && pos.see(s, b8) < 0)
1052 ei.mgValue -= Sign[us] * TrappedBishopA7H7Penalty;
1053 ei.egValue -= Sign[us] * TrappedBishopA7H7Penalty;
1058 // evaluate_trapped_bishop_a1h1() determines whether a bishop on a1/h1
1059 // (a8/h8 for black) is trapped by a friendly pawn on b2/g2 (b7/g7 for
1060 // black), and assigns a penalty if it is. This pattern can obviously
1061 // only occur in Chess960 games.
1063 void evaluate_trapped_bishop_a1h1(const Position &pos, Square s, Color us,
1065 Piece pawn = piece_of_color_and_type(us, PAWN);
1069 assert(square_is_ok(s));
1070 assert(pos.piece_on(s) == piece_of_color_and_type(us, BISHOP));
1072 if (square_file(s) == FILE_A)
1074 b2 = relative_square(us, SQ_B2);
1075 b3 = relative_square(us, SQ_B3);
1076 c3 = relative_square(us, SQ_C3);
1080 b2 = relative_square(us, SQ_G2);
1081 b3 = relative_square(us, SQ_G3);
1082 c3 = relative_square(us, SQ_F3);
1085 if (pos.piece_on(b2) == pawn)
1089 if (!pos.square_is_empty(b3))
1090 penalty = 2*TrappedBishopA1H1Penalty;
1091 else if (pos.piece_on(c3) == pawn)
1092 penalty = TrappedBishopA1H1Penalty;
1094 penalty = TrappedBishopA1H1Penalty / 2;
1096 ei.mgValue -= Sign[us] * penalty;
1097 ei.egValue -= Sign[us] * penalty;
1102 // evaluate_space() computes the space evaluation for a given side. The
1103 // space evaluation is a simple bonus based on the number of safe squares
1104 // available for minor pieces on the central four files on ranks 2--4. Safe
1105 // squares one, two or three squares behind a friendly pawn are counted
1106 // twice. Finally, the space bonus is scaled by a weight taken from the
1107 // material hash table.
1108 template<bool HasPopCnt>
1109 void evaluate_space(const Position &pos, Color us, EvalInfo &ei) {
1111 Color them = opposite_color(us);
1113 // Find the safe squares for our pieces inside the area defined by
1114 // SpaceMask[us]. A square is unsafe it is attacked by an enemy
1115 // pawn, or if it is undefended and attacked by an enemy piece.
1117 Bitboard safeSquares = SpaceMask[us]
1119 & ~ei.attacked_by(them, PAWN)
1120 & ~(~ei.attacked_by(us) & ei.attacked_by(them));
1122 // Find all squares which are at most three squares behind some friendly
1124 Bitboard behindFriendlyPawns = pos.pawns(us);
1127 behindFriendlyPawns |= (behindFriendlyPawns >> 8);
1128 behindFriendlyPawns |= (behindFriendlyPawns >> 16);
1132 behindFriendlyPawns |= (behindFriendlyPawns << 8);
1133 behindFriendlyPawns |= (behindFriendlyPawns << 16);
1136 int space = count_1s_max_15<HasPopCnt>(safeSquares)
1137 + count_1s_max_15<HasPopCnt>(behindFriendlyPawns & safeSquares);
1139 ei.mgValue += Sign[us] * apply_weight(Value(space * ei.mi->space_weight()), WeightSpace);
1143 // apply_weight() applies an evaluation weight to a value
1145 inline Value apply_weight(Value v, int w) {
1146 return (v*w) / 0x100;
1150 // scale_by_game_phase() interpolates between a middle game and an endgame
1151 // score, based on game phase. It also scales the return value by a
1152 // ScaleFactor array.
1154 Value scale_by_game_phase(Value mv, Value ev, Phase ph, const ScaleFactor sf[]) {
1156 assert(mv > -VALUE_INFINITE && mv < VALUE_INFINITE);
1157 assert(ev > -VALUE_INFINITE && ev < VALUE_INFINITE);
1158 assert(ph >= PHASE_ENDGAME && ph <= PHASE_MIDGAME);
1160 ev = apply_scale_factor(ev, sf[(ev > Value(0) ? WHITE : BLACK)]);
1162 Value result = Value(int((mv * ph + ev * (128 - ph)) / 128));
1163 return Value(int(result) & ~(GrainSize - 1));
1167 // compute_weight() computes the value of an evaluation weight, by combining
1168 // an UCI-configurable weight with an internal weight.
1170 int compute_weight(int uciWeight, int internalWeight) {
1172 uciWeight = (uciWeight * 0x100) / 100;
1173 return (uciWeight * internalWeight) / 0x100;
1177 // helper used in read_weights()
1178 int weight_option(const std::string& opt, int weight) {
1180 return compute_weight(get_option_value_int(opt), weight);
1184 // init_safety() initizes the king safety evaluation, based on UCI
1185 // parameters. It is called from read_weights().
1187 void init_safety() {
1189 QueenContactCheckBonus = get_option_value_int("Queen Contact Check Bonus");
1190 QueenCheckBonus = get_option_value_int("Queen Check Bonus");
1191 RookCheckBonus = get_option_value_int("Rook Check Bonus");
1192 BishopCheckBonus = get_option_value_int("Bishop Check Bonus");
1193 KnightCheckBonus = get_option_value_int("Knight Check Bonus");
1194 DiscoveredCheckBonus = get_option_value_int("Discovered Check Bonus");
1195 MateThreatBonus = get_option_value_int("Mate Threat Bonus");
1197 int maxSlope = get_option_value_int("King Safety Max Slope");
1198 int peak = get_option_value_int("King Safety Max Value") * 256 / 100;
1199 double a = get_option_value_int("King Safety Coefficient") / 100.0;
1200 double b = get_option_value_int("King Safety X Intercept");
1201 bool quad = (get_option_value_string("King Safety Curve") == "Quadratic");
1202 bool linear = (get_option_value_string("King Safety Curve") == "Linear");
1204 for (int i = 0; i < 100; i++)
1207 SafetyTable[i] = Value(0);
1209 SafetyTable[i] = Value((int)(a * (i - b) * (i - b)));
1211 SafetyTable[i] = Value((int)(100 * a * (i - b)));
1214 for (int i = 0; i < 100; i++)
1216 if (SafetyTable[i+1] - SafetyTable[i] > maxSlope)
1217 for (int j = i + 1; j < 100; j++)
1218 SafetyTable[j] = SafetyTable[j-1] + Value(maxSlope);
1220 if (SafetyTable[i] > Value(peak))
1221 SafetyTable[i] = Value(peak);