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 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/>.
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 = 4;
48 int WeightMobilityMidgame = 0x100;
49 int WeightMobilityEndgame = 0x100;
50 int WeightPawnStructureMidgame = 0x100;
51 int WeightPawnStructureEndgame = 0x100;
52 int WeightPassedPawnsMidgame = 0x100;
53 int WeightPassedPawnsEndgame = 0x100;
54 int WeightKingSafety[2] = { 0x100, 0x100 };
56 // Internal evaluation weights. These are applied on top of the evaluation
57 // weights read from UCI parameters. The purpose is to be able to change
58 // the evaluation weights while keeping the default values of the UCI
59 // parameters at 100, which looks prettier.
60 const int WeightMobilityMidgameInternal = 0x100;
61 const int WeightMobilityEndgameInternal = 0x100;
62 const int WeightPawnStructureMidgameInternal = 0x100;
63 const int WeightPawnStructureEndgameInternal = 0x100;
64 const int WeightPassedPawnsMidgameInternal = 0x100;
65 const int WeightPassedPawnsEndgameInternal = 0x100;
66 const int WeightKingSafetyInternal = 0x100;
67 const int WeightKingOppSafetyInternal = 0x100;
69 // Visually better to define tables constants
72 // Knight mobility bonus in middle game and endgame, indexed by the number
73 // of attacked squares not occupied by friendly piecess.
74 const Value MidgameKnightMobilityBonus[] = {
76 V(-30), V(-20),V(-10), V(0), V(10), V(20), V(25), V(30), V(30)
79 const Value EndgameKnightMobilityBonus[] = {
81 V(-30), V(-20),V(-10), V(0), V(10), V(20), V(25), V(30), V(30)
84 // Bishop mobility bonus in middle game and endgame, indexed by the number
85 // of attacked squares not occupied by friendly pieces. X-ray attacks through
86 // queens are also included.
87 const Value MidgameBishopMobilityBonus[] = {
89 V(-30), V(-15), V(0), V(15), V(30), V(45), V(58), V(66),
90 // 8 9 10 11 12 13 14 15
91 V( 72), V( 76), V(78), V(80), V(81), V(82), V(83), V(83)
94 const Value EndgameBishopMobilityBonus[] = {
96 V(-30), V(-15), V(0), V(15), V(30), V(45), V(58), V(66),
97 // 8 9 10 11 12 13 14 15
98 V( 72), V( 76), V(78), V(80), V(81), V(82), V(83), V(83)
101 // Rook mobility bonus in middle game and endgame, indexed by the number
102 // of attacked squares not occupied by friendly pieces. X-ray attacks through
103 // queens and rooks are also included.
104 const Value MidgameRookMobilityBonus[] = {
106 V(-18), V(-12), V(-6), V(0), V(6), V(12), V(16), V(21),
107 // 8 9 10 11 12 13 14 15
108 V( 24), V( 27), V(28), V(29), V(30), V(31), V(32), V(33)
111 const Value EndgameRookMobilityBonus[] = {
113 V(-30), V(-18), V(-6), V(6), V(18), V(30), V(42), V(54),
114 // 8 9 10 11 12 13 14 15
115 V( 66), V( 74), V(78), V(80), V(81), V(82), V(83), V(83)
118 // Queen mobility bonus in middle game and endgame, indexed by the number
119 // of attacked squares not occupied by friendly pieces.
120 const Value MidgameQueenMobilityBonus[] = {
122 V(-10), V(-8), V(-6), V(-4), V(-2), V( 0), V( 2), V( 4),
123 // 8 9 10 11 12 13 14 15
124 V( 6), V( 8), V(10), V(12), V(13), V(14), V(15), V(16),
125 // 16 17 18 19 20 21 22 23
126 V( 16), V(16), V(16), V(16), V(16), V(16), V(16), V(16),
127 // 24 25 26 27 28 29 30 31
128 V( 16), V(16), V(16), V(16), V(16), V(16), V(16), V(16)
131 const Value EndgameQueenMobilityBonus[] = {
133 V(-20),V(-15),V(-10), V(-5), V( 0), V( 5), V(10), V(15),
134 // 8 9 10 11 12 13 14 15
135 V( 19), V(23), V(27), V(29), V(30), V(30), V(30), V(30),
136 // 16 17 18 19 20 21 22 23
137 V( 30), V(30), V(30), V(30), V(30), V(30), V(30), V(30),
138 // 24 25 26 27 28 29 30 31
139 V( 30), V(30), V(30), V(30), V(30), V(30), V(30), V(30)
142 // Outpost bonuses for knights and bishops, indexed by square (from white's
144 const Value KnightOutpostBonus[64] = {
146 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 1
147 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 2
148 V(0), V(0), V(5),V(10),V(10), V(5), V(0), V(0), // 3
149 V(0), V(5),V(20),V(30),V(30),V(20), V(5), V(0), // 4
150 V(0),V(10),V(30),V(40),V(40),V(30),V(10), V(0), // 5
151 V(0), V(5),V(20),V(20),V(20),V(20), V(5), V(0), // 6
152 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 7
153 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0) // 8
156 const Value BishopOutpostBonus[64] = {
158 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 1
159 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 2
160 V(0), V(0), V(5), V(5), V(5), V(5), V(0), V(0), // 3
161 V(0), V(5),V(10),V(10),V(10),V(10), V(5), V(0), // 4
162 V(0),V(10),V(20),V(20),V(20),V(20),V(10), V(0), // 5
163 V(0), V(5), V(8), V(8), V(8), V(8), V(5), V(0), // 6
164 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 7
165 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0) // 8
168 // Bonus for unstoppable passed pawns:
169 const Value UnstoppablePawnValue = Value(0x500);
171 // Rooks and queens on the 7th rank:
172 const Value MidgameRookOn7thBonus = Value(50);
173 const Value EndgameRookOn7thBonus = Value(100);
174 const Value MidgameQueenOn7thBonus = Value(25);
175 const Value EndgameQueenOn7thBonus = Value(50);
177 // Rooks on open files:
178 const Value RookOpenFileBonus = Value(40);
179 const Value RookHalfOpenFileBonus = Value(20);
181 // Penalty for rooks trapped inside a friendly king which has lost the
183 const Value TrappedRookPenalty = Value(180);
185 // Penalty for a bishop on a7/h7 (a2/h2 for black) which is trapped by
187 const Value TrappedBishopA7H7Penalty = Value(300);
189 // Bitboard masks for detecting trapped bishops on a7/h7 (a2/h2 for black):
190 const Bitboard MaskA7H7[2] = {
191 ((1ULL << SQ_A7) | (1ULL << SQ_H7)),
192 ((1ULL << SQ_A2) | (1ULL << SQ_H2))
195 // Penalty for a bishop on a1/h1 (a8/h8 for black) which is trapped by
196 // a friendly pawn on b2/g2 (b7/g7 for black). This can obviously only
197 // happen in Chess960 games.
198 const Value TrappedBishopA1H1Penalty = Value(100);
200 // Bitboard masks for detecting trapped bishops on a1/h1 (a8/h8 for black):
201 const Bitboard MaskA1H1[2] = {
202 ((1ULL << SQ_A1) | (1ULL << SQ_H1)),
203 ((1ULL << SQ_A8) | (1ULL << SQ_H8))
206 /// King safety constants and variables. The king safety scores are taken
207 /// from the array SafetyTable[]. Various little "meta-bonuses" measuring
208 /// the strength of the attack are added up into an integer, which is used
209 /// as an index to SafetyTable[].
211 // Attack weights for each piece type.
212 const int QueenAttackWeight = 5;
213 const int RookAttackWeight = 3;
214 const int BishopAttackWeight = 2;
215 const int KnightAttackWeight = 2;
217 // Bonuses for safe checks for each piece type.
218 int QueenContactCheckBonus = 4;
219 int RookContactCheckBonus = 2;
220 int QueenCheckBonus = 2;
221 int RookCheckBonus = 1;
222 int BishopCheckBonus = 1;
223 int KnightCheckBonus = 1;
224 int DiscoveredCheckBonus = 3;
226 // Scan for queen contact mates?
227 const bool QueenContactMates = true;
229 // Bonus for having a mate threat.
230 int MateThreatBonus = 3;
232 // InitKingDanger[] contains bonuses based on the position of the defending
234 const int InitKingDanger[64] = {
235 2, 0, 2, 5, 5, 2, 0, 2,
236 2, 2, 4, 8, 8, 4, 2, 2,
237 7, 10, 12, 12, 12, 12, 10, 7,
238 15, 15, 15, 15, 15, 15, 15, 15,
239 15, 15, 15, 15, 15, 15, 15, 15,
240 15, 15, 15, 15, 15, 15, 15, 15,
241 15, 15, 15, 15, 15, 15, 15, 15,
242 15, 15, 15, 15, 15, 15, 15, 15
245 // SafetyTable[] contains the actual king safety scores. It is initialized
247 Value SafetyTable[100];
249 // Pawn and material hash tables, indexed by the current thread id:
250 PawnInfoTable *PawnTable[8] = {0, 0, 0, 0, 0, 0, 0, 0};
251 MaterialInfoTable *MaterialTable[8] = {0, 0, 0, 0, 0, 0, 0, 0};
253 // Sizes of pawn and material hash tables:
254 const int PawnTableSize = 16384;
255 const int MaterialTableSize = 1024;
257 // Array which gives the number of nonzero bits in an 8-bit integer:
258 uint8_t BitCount8Bit[256];
260 // Function prototypes:
261 void evaluate_knight(const Position &p, Square s, Color us, EvalInfo &ei);
262 void evaluate_bishop(const Position &p, Square s, Color us, EvalInfo &ei);
263 void evaluate_rook(const Position &p, Square s, Color us, EvalInfo &ei);
264 void evaluate_queen(const Position &p, Square s, Color us, EvalInfo &ei);
265 void evaluate_king(const Position &p, Square s, Color us, EvalInfo &ei);
267 void evaluate_passed_pawns(const Position &pos, EvalInfo &ei);
268 void evaluate_trapped_bishop_a7h7(const Position &pos, Square s, Color us,
270 void evaluate_trapped_bishop_a1h1(const Position &pos, Square s, Color us,
273 inline Value apply_weight(Value v, int w);
274 Value scale_by_game_phase(Value mv, Value ev, Phase ph, const ScaleFactor sf[]);
276 int count_1s_8bit(Bitboard b);
278 int compute_weight(int uciWeight, int internalWeight);
279 int weight_option(const std::string& opt, int weight);
289 /// evaluate() is the main evaluation function. It always computes two
290 /// values, an endgame score and a middle game score, and interpolates
291 /// between them based on the remaining material.
293 Value evaluate(const Position &pos, EvalInfo &ei, int threadID) {
296 assert(threadID >= 0 && threadID < THREAD_MAX);
298 memset(&ei, 0, sizeof(EvalInfo));
300 // Initialize by reading the incrementally updated scores included in the
301 // position object (material + piece square tables)
302 ei.mgValue = pos.mg_value();
303 ei.egValue = pos.eg_value();
305 // Probe the material hash table
306 ei.mi = MaterialTable[threadID]->get_material_info(pos);
307 ei.mgValue += ei.mi->mg_value();
308 ei.egValue += ei.mi->eg_value();
310 // If we have a specialized evaluation function for the current material
311 // configuration, call it and return
312 if (ei.mi->specialized_eval_exists())
313 return ei.mi->evaluate(pos);
315 // After get_material_info() call that modifies them
316 ScaleFactor factor[2];
317 factor[WHITE] = ei.mi->scale_factor(pos, WHITE);
318 factor[BLACK] = ei.mi->scale_factor(pos, BLACK);
320 // Probe the pawn hash table
321 ei.pi = PawnTable[threadID]->get_pawn_info(pos);
322 ei.mgValue += apply_weight(ei.pi->mg_value(), WeightPawnStructureMidgame);
323 ei.egValue += apply_weight(ei.pi->eg_value(), WeightPawnStructureEndgame);
325 // Initialize king attack bitboards and king attack zones for both sides
326 ei.attackedBy[WHITE][KING] = pos.piece_attacks<KING>(pos.king_square(WHITE));
327 ei.attackedBy[BLACK][KING] = pos.piece_attacks<KING>(pos.king_square(BLACK));
328 ei.kingZone[WHITE] = ei.attackedBy[BLACK][KING] | (ei.attackedBy[BLACK][KING] >> 8);
329 ei.kingZone[BLACK] = ei.attackedBy[WHITE][KING] | (ei.attackedBy[WHITE][KING] << 8);
331 // Initialize pawn attack bitboards for both sides
332 ei.attackedBy[WHITE][PAWN] = ((pos.pawns(WHITE) << 9) & ~FileABB) | ((pos.pawns(WHITE) << 7) & ~FileHBB);
333 ei.attackedBy[BLACK][PAWN] = ((pos.pawns(BLACK) >> 7) & ~FileABB) | ((pos.pawns(BLACK) >> 9) & ~FileHBB);
334 ei.kingAttackersCount[WHITE] = count_1s_max_15(ei.attackedBy[WHITE][PAWN] & ei.attackedBy[BLACK][KING])/2;
335 ei.kingAttackersCount[BLACK] = count_1s_max_15(ei.attackedBy[BLACK][PAWN] & ei.attackedBy[WHITE][KING])/2;
338 for (Color c = WHITE; c <= BLACK; c++)
341 for (int i = 0; i < pos.piece_count(c, KNIGHT); i++)
342 evaluate_knight(pos, pos.piece_list(c, KNIGHT, i), c, ei);
345 for (int i = 0; i < pos.piece_count(c, BISHOP); i++)
346 evaluate_bishop(pos, pos.piece_list(c, BISHOP, i), c, ei);
349 for (int i = 0; i < pos.piece_count(c, ROOK); i++)
350 evaluate_rook(pos, pos.piece_list(c, ROOK, i), c, ei);
353 for(int i = 0; i < pos.piece_count(c, QUEEN); i++)
354 evaluate_queen(pos, pos.piece_list(c, QUEEN, i), c, ei);
356 // Special pattern: trapped bishops on a7/h7/a2/h2
357 Bitboard b = pos.bishops(c) & MaskA7H7[c];
360 Square s = pop_1st_bit(&b);
361 evaluate_trapped_bishop_a7h7(pos, s, c, ei);
364 // Special pattern: trapped bishops on a1/h1/a8/h8 in Chess960:
367 b = pos.bishops(c) & MaskA1H1[c];
370 Square s = pop_1st_bit(&b);
371 evaluate_trapped_bishop_a1h1(pos, s, c, ei);
375 // Sum up all attacked squares
376 ei.attackedBy[c][0] = ei.attackedBy[c][PAWN] | ei.attackedBy[c][KNIGHT]
377 | ei.attackedBy[c][BISHOP] | ei.attackedBy[c][ROOK]
378 | ei.attackedBy[c][QUEEN] | ei.attackedBy[c][KING];
381 // Kings. Kings are evaluated after all other pieces for both sides,
382 // because we need complete attack information for all pieces when computing
383 // the king safety evaluation.
384 for (Color c = WHITE; c <= BLACK; c++)
385 evaluate_king(pos, pos.king_square(c), c, ei);
387 // Evaluate passed pawns. We evaluate passed pawns for both sides at once,
388 // because we need to know which side promotes first in positions where
389 // both sides have an unstoppable passed pawn.
390 if (ei.pi->passed_pawns())
391 evaluate_passed_pawns(pos, ei);
393 Phase phase = pos.game_phase();
395 // Middle-game specific evaluation terms
396 if (phase > PHASE_ENDGAME)
398 // Pawn storms in positions with opposite castling.
399 if ( square_file(pos.king_square(WHITE)) >= FILE_E
400 && square_file(pos.king_square(BLACK)) <= FILE_D)
402 ei.mgValue += ei.pi->queenside_storm_value(WHITE)
403 - ei.pi->kingside_storm_value(BLACK);
405 else if ( square_file(pos.king_square(WHITE)) <= FILE_D
406 && square_file(pos.king_square(BLACK)) >= FILE_E)
408 ei.mgValue += ei.pi->kingside_storm_value(WHITE)
409 - ei.pi->queenside_storm_value(BLACK);
413 ei.mgValue += apply_weight(ei.mgMobility, WeightMobilityMidgame);
414 ei.egValue += apply_weight(ei.egMobility, WeightMobilityEndgame);
416 // If we don't already have an unusual scale factor, check for opposite
417 // colored bishop endgames, and use a lower scale for those:
418 if ( phase < PHASE_MIDGAME
419 && pos.opposite_colored_bishops()
420 && ( (factor[WHITE] == SCALE_FACTOR_NORMAL && ei.egValue > Value(0))
421 || (factor[BLACK] == SCALE_FACTOR_NORMAL && ei.egValue < Value(0))))
425 // Only the two bishops ?
426 if ( pos.non_pawn_material(WHITE) == BishopValueMidgame
427 && pos.non_pawn_material(BLACK) == BishopValueMidgame)
429 // Check for KBP vs KB with only a single pawn that is almost
430 // certainly a draw or at least two pawns.
431 bool one_pawn = (pos.piece_count(WHITE, PAWN) + pos.piece_count(BLACK, PAWN) == 1);
432 sf = one_pawn ? ScaleFactor(8) : ScaleFactor(32);
435 // Endgame with opposite-colored bishops, but also other pieces. Still
436 // a bit drawish, but not as drawish as with only the two bishops.
437 sf = ScaleFactor(50);
439 if (factor[WHITE] == SCALE_FACTOR_NORMAL)
441 if (factor[BLACK] == SCALE_FACTOR_NORMAL)
445 // Interpolate between the middle game and the endgame score, and
447 Color stm = pos.side_to_move();
449 Value v = Sign[stm] * scale_by_game_phase(ei.mgValue, ei.egValue, phase, factor);
451 return (ei.mateThreat[stm] == MOVE_NONE ? v : 8 * QueenValueMidgame - v);
455 /// quick_evaluate() does a very approximate evaluation of the current position.
456 /// It currently considers only material and piece square table scores. Perhaps
457 /// we should add scores from the pawn and material hash tables?
459 Value quick_evaluate(const Position &pos) {
464 ScaleFactor sf[2] = {SCALE_FACTOR_NORMAL, SCALE_FACTOR_NORMAL};
466 Value mgv = pos.mg_value();
467 Value egv = pos.eg_value();
468 Phase ph = pos.game_phase();
469 Color stm = pos.side_to_move();
471 return Sign[stm] * scale_by_game_phase(mgv, egv, ph, sf);
475 /// init_eval() initializes various tables used by the evaluation function.
477 void init_eval(int threads) {
479 assert(threads <= THREAD_MAX);
481 for (int i = 0; i < THREAD_MAX; i++)
486 delete MaterialTable[i];
488 MaterialTable[i] = NULL;
492 PawnTable[i] = new PawnInfoTable(PawnTableSize);
493 if (!MaterialTable[i])
494 MaterialTable[i] = new MaterialInfoTable(MaterialTableSize);
497 for (Bitboard b = 0ULL; b < 256ULL; b++)
498 BitCount8Bit[b] = count_1s(b);
502 /// quit_eval() releases heap-allocated memory at program termination.
506 for (int i = 0; i < THREAD_MAX; i++)
509 delete MaterialTable[i];
514 /// read_weights() reads evaluation weights from the corresponding UCI
517 void read_weights(Color us) {
519 WeightMobilityMidgame = weight_option("Mobility (Middle Game)", WeightMobilityMidgameInternal);
520 WeightMobilityEndgame = weight_option("Mobility (Endgame)", WeightMobilityEndgameInternal);
521 WeightPawnStructureMidgame = weight_option("Pawn Structure (Middle Game)", WeightPawnStructureMidgameInternal);
522 WeightPawnStructureEndgame = weight_option("Pawn Structure (Endgame)", WeightPawnStructureEndgameInternal);
523 WeightPassedPawnsMidgame = weight_option("Passed Pawns (Middle Game)", WeightPassedPawnsMidgameInternal);
524 WeightPassedPawnsEndgame = weight_option("Passed Pawns (Endgame)", WeightPassedPawnsEndgameInternal);
526 Color them = opposite_color(us);
528 WeightKingSafety[us] = weight_option("Cowardice", WeightKingSafetyInternal);
529 WeightKingSafety[them] = weight_option("Aggressiveness", WeightKingOppSafetyInternal);
537 // evaluate_common() computes terms common to all pieces attack
539 int evaluate_common(const Position&p, const Bitboard& b, Color us, EvalInfo& ei,
540 int AttackWeight, const Value* mgBonus, const Value* egBonus,
541 Square s = SQ_NONE, const Value* OutpostBonus = NULL) {
543 Color them = opposite_color(us);
546 if (b & ei.kingZone[us])
548 ei.kingAttackersCount[us]++;
549 ei.kingAttackersWeight[us] += AttackWeight;
550 Bitboard bb = (b & ei.attackedBy[them][KING]);
552 ei.kingAdjacentZoneAttacksCount[us] += count_1s_max_15(bb);
556 int mob = count_1s_max_15(b & ~p.pieces_of_color(us));
557 ei.mgMobility += Sign[us] * mgBonus[mob];
558 ei.egMobility += Sign[us] * egBonus[mob];
560 // Bishop and Knight outposts
561 if (!OutpostBonus || !p.square_is_weak(s, them))
564 // Initial bonus based on square
566 v = bonus = OutpostBonus[relative_square(us, s)];
568 // Increase bonus if supported by pawn, especially if the opponent has
569 // no minor piece which can exchange the outpost piece
570 if (v && (p.pawn_attacks(them, s) & p.pawns(us)))
573 if ( p.piece_count(them, KNIGHT) == 0
574 && (SquaresByColorBB[square_color(s)] & p.bishops(them)) == EmptyBoardBB)
577 ei.mgValue += Sign[us] * bonus;
578 ei.egValue += Sign[us] * bonus;
583 // evaluate_knight() assigns bonuses and penalties to a knight of a given
584 // color on a given square.
586 void evaluate_knight(const Position &p, Square s, Color us, EvalInfo &ei) {
588 Bitboard b = p.piece_attacks<KNIGHT>(s);
589 ei.attackedBy[us][KNIGHT] |= b;
591 // King attack, mobility and outposts
592 evaluate_common(p, b, us, ei, KnightAttackWeight, MidgameKnightMobilityBonus,
593 EndgameKnightMobilityBonus, s, KnightOutpostBonus);
597 // evaluate_bishop() assigns bonuses and penalties to a bishop of a given
598 // color on a given square.
600 void evaluate_bishop(const Position &p, Square s, Color us, EvalInfo &ei) {
602 Bitboard b = bishop_attacks_bb(s, p.occupied_squares() & ~p.queens(us));
603 ei.attackedBy[us][BISHOP] |= b;
605 // King attack, mobility and outposts
606 evaluate_common(p, b, us, ei, BishopAttackWeight, MidgameBishopMobilityBonus,
607 EndgameBishopMobilityBonus, s, BishopOutpostBonus);
611 // evaluate_rook() assigns bonuses and penalties to a rook of a given
612 // color on a given square.
614 void evaluate_rook(const Position &p, Square s, Color us, EvalInfo &ei) {
616 //Bitboard b = p.rook_attacks(s);
617 Bitboard b = rook_attacks_bb(s, p.occupied_squares() & ~p.rooks_and_queens(us));
618 ei.attackedBy[us][ROOK] |= b;
620 // King attack and mobility
621 int mob = evaluate_common(p, b, us, ei, RookAttackWeight, MidgameRookMobilityBonus,
622 EndgameRookMobilityBonus);
625 Color them = opposite_color(us);
627 if ( relative_rank(us, s) == RANK_7
628 && relative_rank(us, p.king_square(them)) == RANK_8)
630 ei.mgValue += Sign[us] * MidgameRookOn7thBonus;
631 ei.egValue += Sign[us] * EndgameRookOn7thBonus;
634 // Open and half-open files
635 File f = square_file(s);
636 if (ei.pi->file_is_half_open(us, f))
638 if (ei.pi->file_is_half_open(them, f))
640 ei.mgValue += Sign[us] * RookOpenFileBonus;
641 ei.egValue += Sign[us] * RookOpenFileBonus;
645 ei.mgValue += Sign[us] * RookHalfOpenFileBonus;
646 ei.egValue += Sign[us] * RookHalfOpenFileBonus;
650 // Penalize rooks which are trapped inside a king. Penalize more if
651 // king has lost right to castle
652 if (mob > 6 || ei.pi->file_is_half_open(us, f))
655 Square ksq = p.king_square(us);
657 if ( square_file(ksq) >= FILE_E
658 && square_file(s) > square_file(ksq)
659 && (relative_rank(us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
661 // Is there a half-open file between the king and the edge of the board?
662 if (!ei.pi->has_open_file_to_right(us, square_file(ksq)))
663 ei.mgValue -= p.can_castle(us)? Sign[us] * ((TrappedRookPenalty - mob * 16) / 2)
664 : Sign[us] * (TrappedRookPenalty - mob * 16);
666 else if ( square_file(ksq) <= FILE_D
667 && square_file(s) < square_file(ksq)
668 && (relative_rank(us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
670 // Is there a half-open file between the king and the edge of the board?
671 if (!ei.pi->has_open_file_to_left(us, square_file(ksq)))
672 ei.mgValue -= p.can_castle(us)? Sign[us] * ((TrappedRookPenalty - mob * 16) / 2)
673 : Sign[us] * (TrappedRookPenalty - mob * 16);
678 // evaluate_queen() assigns bonuses and penalties to a queen of a given
679 // color on a given square.
681 void evaluate_queen(const Position &p, Square s, Color us, EvalInfo &ei) {
683 Bitboard b = p.piece_attacks<QUEEN>(s);
684 ei.attackedBy[us][QUEEN] |= b;
686 // King attack and mobility
687 evaluate_common(p, b, us, ei, QueenAttackWeight, MidgameQueenMobilityBonus,
688 EndgameQueenMobilityBonus);
691 Color them = opposite_color(us);
693 if ( relative_rank(us, s) == RANK_7
694 && relative_rank(us, p.king_square(them)) == RANK_8)
696 ei.mgValue += Sign[us] * MidgameQueenOn7thBonus;
697 ei.egValue += Sign[us] * EndgameQueenOn7thBonus;
701 inline Bitboard shiftRowsDown(const Bitboard& b, int num) {
703 return b >> (num << 3);
706 // evaluate_king() assigns bonuses and penalties to a king of a given
707 // color on a given square.
709 void evaluate_king(const Position &p, Square s, Color us, EvalInfo &ei) {
711 int shelter = 0, sign = Sign[us];
714 if (relative_rank(us, s) <= RANK_4)
716 Bitboard pawns = p.pawns(us) & this_and_neighboring_files_bb(s);
717 Rank r = square_rank(s);
718 for (int i = 1; i < 4; i++)
719 shelter += count_1s_8bit(shiftRowsDown(pawns, r+i*sign)) * (128>>i);
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 is based on the number
748 // 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(undefended)) * 3
754 + InitKingDanger[relative_square(us, s)] - shelter / 32;
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(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 && !(rook_attacks_bb(to, occ & ClearMaskBB[from]) & p.rooks_and_queens(us)))
793 ei.mateThreat[them] = make_move(from, to);
800 // Analyse safe rook contact checks:
801 if (RookContactCheckBonus)
803 b = undefended & ei.attacked_by(them, ROOK) & ~p.pieces_of_color(them);
806 Bitboard attackedByOthers =
807 ei.attacked_by(them, PAWN) | ei.attacked_by(them, KNIGHT)
808 | ei.attacked_by(them, BISHOP) | ei.attacked_by(them, QUEEN);
810 b &= attackedByOthers;
813 int count = count_1s_max_15(b);
814 attackUnits += (RookContactCheckBonus * count * (sente? 2 : 1));
818 // Analyse safe distance checks:
819 if (QueenCheckBonus > 0 || RookCheckBonus > 0)
821 b = p.piece_attacks<ROOK>(s) & ~p.pieces_of_color(them) & ~ei.attacked_by(us);
824 b2 = b & ei.attacked_by(them, QUEEN);
826 attackUnits += QueenCheckBonus * count_1s_max_15(b2);
829 b2 = b & ei.attacked_by(them, ROOK);
831 attackUnits += RookCheckBonus * count_1s_max_15(b2);
833 if (QueenCheckBonus > 0 || BishopCheckBonus > 0)
835 b = p.piece_attacks<BISHOP>(s) & ~p.pieces_of_color(them) & ~ei.attacked_by(us);
838 b2 = b & ei.attacked_by(them, QUEEN);
840 attackUnits += QueenCheckBonus * count_1s_max_15(b2);
843 b2 = b & ei.attacked_by(them, BISHOP);
845 attackUnits += BishopCheckBonus * count_1s_max_15(b2);
847 if (KnightCheckBonus > 0)
849 b = p.piece_attacks<KNIGHT>(s) & ~p.pieces_of_color(them) & ~ei.attacked_by(us);
852 b2 = b & ei.attacked_by(them, KNIGHT);
854 attackUnits += KnightCheckBonus * count_1s_max_15(b2);
857 // Analyse discovered checks (only for non-pawns right now, consider
858 // adding pawns later).
859 if (DiscoveredCheckBonus)
861 b = p.discovered_check_candidates(them) & ~p.pawns();
863 attackUnits += DiscoveredCheckBonus * count_1s_max_15(b) * (sente? 2 : 1);
866 // Has a mate threat been found? We don't do anything here if the
867 // side with the mating move is the side to move, because in that
868 // case the mating side will get a huge bonus at the end of the main
869 // evaluation function instead.
870 if (ei.mateThreat[them] != MOVE_NONE)
871 attackUnits += MateThreatBonus;
873 // Ensure that attackUnits is between 0 and 99, in order to avoid array
874 // out of bounds errors:
878 if (attackUnits >= 100)
881 // Finally, extract the king safety score from the SafetyTable[] array.
882 // Add the score to the evaluation, and also to ei.futilityMargin. The
883 // reason for adding the king safety score to the futility margin is
884 // that the king safety scores can sometimes be very big, and that
885 // capturing a single attacking piece can therefore result in a score
886 // change far bigger than the value of the captured piece.
887 Value v = apply_weight(SafetyTable[attackUnits], WeightKingSafety[us]);
889 ei.mgValue -= sign * v;
891 if (us == p.side_to_move())
892 ei.futilityMargin += v;
897 // evaluate_passed_pawns() evaluates the passed pawns for both sides.
899 void evaluate_passed_pawns(const Position &pos, EvalInfo &ei) {
900 bool hasUnstoppable[2] = {false, false};
901 int movesToGo[2] = {100, 100};
903 for(Color us = WHITE; us <= BLACK; us++) {
904 Color them = opposite_color(us);
905 Square ourKingSq = pos.king_square(us);
906 Square theirKingSq = pos.king_square(them);
907 Bitboard b = ei.pi->passed_pawns() & pos.pawns(us), b2, b3, b4;
910 Square s = pop_1st_bit(&b);
911 assert(pos.piece_on(s) == pawn_of_color(us));
912 assert(pos.pawn_is_passed(us, s));
914 int r = int(relative_rank(us, s) - RANK_2);
915 int tr = Max(0, r * (r-1));
916 Square blockSq = s + pawn_push(us);
918 // Base bonus based on rank:
919 Value mbonus = Value(20 * tr);
920 Value ebonus = Value(10 + r * r * 10);
922 // Adjust bonus based on king proximity:
923 ebonus -= Value(square_distance(ourKingSq, blockSq) * 3 * tr);
925 Value(square_distance(ourKingSq, blockSq + pawn_push(us)) * 1 * tr);
926 ebonus += Value(square_distance(theirKingSq, blockSq) * 6 * tr);
928 // If the pawn is free to advance, increase bonus:
929 if(pos.square_is_empty(blockSq)) {
931 b2 = squares_in_front_of(us, s);
932 b3 = b2 & ei.attacked_by(them);
933 b4 = b2 & ei.attacked_by(us);
934 if((b2 & pos.pieces_of_color(them)) == EmptyBoardBB) {
935 // There are no enemy pieces in the pawn's path! Are any of the
936 // squares in the pawn's path attacked by the enemy?
937 if(b3 == EmptyBoardBB)
938 // No enemy attacks, huge bonus!
939 ebonus += Value(tr * ((b2 == b4)? 17 : 15));
941 // OK, there are enemy attacks. Are those squares which are
942 // attacked by the enemy also attacked by us? If yes, big bonus
943 // (but smaller than when there are no enemy attacks), if no,
944 // somewhat smaller bonus.
945 ebonus += Value(tr * (((b3 & b4) == b3)? 13 : 8));
948 // There are some enemy pieces in the pawn's path. While this is
949 // sad, we still assign a moderate bonus if all squares in the path
950 // which are either occupied by or attacked by enemy pieces are
951 // also attacked by us.
952 if(((b3 | (b2 & pos.pieces_of_color(them))) & ~b4) == EmptyBoardBB)
953 ebonus += Value(tr * 6);
955 // At last, add a small bonus when there are no *friendly* pieces
956 // in the pawn's path:
957 if((b2 & pos.pieces_of_color(us)) == EmptyBoardBB)
961 // If the pawn is supported by a friendly pawn, increase bonus.
962 b2 = pos.pawns(us) & neighboring_files_bb(s);
964 ebonus += Value(r * 20);
965 else if(pos.pawn_attacks(them, s) & b2)
966 ebonus += Value(r * 12);
968 // If the other side has only a king, check whether the pawn is
970 if(pos.non_pawn_material(them) == Value(0)) {
974 qsq = relative_square(us, make_square(square_file(s), RANK_8));
975 d = square_distance(s, qsq) - square_distance(theirKingSq, qsq)
976 + ((us == pos.side_to_move())? 0 : 1);
979 int mtg = RANK_8 - relative_rank(us, s);
981 count_1s_max_15(squares_in_front_of(us,s)&pos.occupied_squares());
985 hasUnstoppable[us] = true;
986 movesToGo[us] = Min(movesToGo[us], mtg);
990 // Rook pawns are a special case: They are sometimes worse, and
991 // sometimes better than other passed pawns. It is difficult to find
992 // good rules for determining whether they are good or bad. For now,
993 // we try the following: Increase the value for rook pawns if the
994 // other side has no pieces apart from a knight, and decrease the
995 // value if the other side has a rook or queen.
996 if(square_file(s) == FILE_A || square_file(s) == FILE_H) {
997 if(pos.non_pawn_material(them) == KnightValueMidgame
998 && pos.piece_count(them, KNIGHT) == 1)
999 ebonus += ebonus / 4;
1000 else if(pos.rooks_and_queens(them))
1001 ebonus -= ebonus / 4;
1004 // Add the scores for this pawn to the middle game and endgame eval.
1005 ei.mgValue += apply_weight(Sign[us] * mbonus, WeightPassedPawnsMidgame);
1006 ei.egValue += apply_weight(Sign[us] * ebonus, WeightPassedPawnsEndgame);
1010 // Does either side have an unstoppable passed pawn?
1011 if(hasUnstoppable[WHITE] && !hasUnstoppable[BLACK])
1012 ei.egValue += UnstoppablePawnValue - Value(0x40 * movesToGo[WHITE]);
1013 else if(hasUnstoppable[BLACK] && !hasUnstoppable[WHITE])
1014 ei.egValue -= UnstoppablePawnValue - Value(0x40 * movesToGo[BLACK]);
1015 else if(hasUnstoppable[BLACK] && hasUnstoppable[WHITE]) {
1016 // Both sides have unstoppable pawns! Try to find out who queens
1017 // first. We begin by transforming 'movesToGo' to the number of
1018 // plies until the pawn queens for both sides:
1019 movesToGo[WHITE] *= 2;
1020 movesToGo[BLACK] *= 2;
1021 movesToGo[pos.side_to_move()]--;
1023 // If one side queens at least three plies before the other, that
1025 if(movesToGo[WHITE] <= movesToGo[BLACK] - 3)
1026 ei.egValue += UnstoppablePawnValue - Value(0x40 * (movesToGo[WHITE]/2));
1027 else if(movesToGo[BLACK] <= movesToGo[WHITE] - 3)
1028 ei.egValue -= UnstoppablePawnValue - Value(0x40 * (movesToGo[BLACK]/2));
1030 // We could also add some rules about the situation when one side
1031 // queens exactly one ply before the other: Does the first queen
1032 // check the opponent's king, or attack the opponent's queening square?
1033 // This is slightly tricky to get right, because it is possible that
1034 // the opponent's king has moved somewhere before the first pawn queens.
1039 // evaluate_trapped_bishop_a7h7() determines whether a bishop on a7/h7
1040 // (a2/h2 for black) is trapped by enemy pawns, and assigns a penalty
1043 void evaluate_trapped_bishop_a7h7(const Position &pos, Square s, Color us,
1046 assert(square_is_ok(s));
1047 assert(pos.piece_on(s) == bishop_of_color(us));
1049 Square b6 = relative_square(us, (square_file(s) == FILE_A) ? SQ_B6 : SQ_G6);
1050 Square b8 = relative_square(us, (square_file(s) == FILE_A) ? SQ_B8 : SQ_G8);
1052 if ( pos.piece_on(b6) == pawn_of_color(opposite_color(us))
1053 && pos.see(s, b6) < 0
1054 && pos.see(s, b8) < 0)
1056 ei.mgValue -= Sign[us] * TrappedBishopA7H7Penalty;
1057 ei.egValue -= Sign[us] * TrappedBishopA7H7Penalty;
1062 // evaluate_trapped_bishop_a1h1() determines whether a bishop on a1/h1
1063 // (a8/h8 for black) is trapped by a friendly pawn on b2/g2 (b7/g7 for
1064 // black), and assigns a penalty if it is. This pattern can obviously
1065 // only occur in Chess960 games.
1067 void evaluate_trapped_bishop_a1h1(const Position &pos, Square s, Color us,
1069 Piece pawn = pawn_of_color(us);
1073 assert(square_is_ok(s));
1074 assert(pos.piece_on(s) == bishop_of_color(us));
1076 if(square_file(s) == FILE_A) {
1077 b2 = relative_square(us, SQ_B2);
1078 b3 = relative_square(us, SQ_B3);
1079 c3 = relative_square(us, SQ_C3);
1082 b2 = relative_square(us, SQ_G2);
1083 b3 = relative_square(us, SQ_G3);
1084 c3 = relative_square(us, SQ_F3);
1087 if(pos.piece_on(b2) == pawn) {
1090 if(!pos.square_is_empty(b3))
1091 penalty = 2*TrappedBishopA1H1Penalty;
1092 else if(pos.piece_on(c3) == pawn)
1093 penalty = TrappedBishopA1H1Penalty;
1095 penalty = TrappedBishopA1H1Penalty / 2;
1097 ei.mgValue -= Sign[us] * penalty;
1098 ei.egValue -= Sign[us] * penalty;
1104 // apply_weight applies an evaluation weight to a value.
1106 inline Value apply_weight(Value v, int w) {
1107 return (v*w) / 0x100;
1111 // scale_by_game_phase interpolates between a middle game and an endgame
1112 // score, based on game phase. It also scales the return value by a
1113 // ScaleFactor array.
1115 Value scale_by_game_phase(Value mv, Value ev, Phase ph, const ScaleFactor sf[]) {
1117 assert(mv > -VALUE_INFINITE && mv < VALUE_INFINITE);
1118 assert(ev > -VALUE_INFINITE && ev < VALUE_INFINITE);
1119 assert(ph >= PHASE_ENDGAME && ph <= PHASE_MIDGAME);
1121 ev = apply_scale_factor(ev, sf[(ev > Value(0) ? WHITE : BLACK)]);
1123 // Linearized sigmoid interpolator
1125 sph -= (64 - sph) / 4;
1126 sph = Min(PHASE_MIDGAME, Max(PHASE_ENDGAME, sph));
1128 Value result = Value(int((mv * sph + ev * (128 - sph)) / 128));
1130 return Value(int(result) & ~(GrainSize - 1));
1134 // count_1s_8bit() counts the number of nonzero bits in the 8 least
1135 // significant bits of a Bitboard. This function is used by the king
1136 // shield evaluation.
1138 int count_1s_8bit(Bitboard b) {
1139 return int(BitCount8Bit[b & 0xFF]);
1143 // compute_weight() computes the value of an evaluation weight, by combining
1144 // an UCI-configurable weight with an internal weight.
1146 int compute_weight(int uciWeight, int internalWeight) {
1147 uciWeight = (uciWeight * 0x100) / 100;
1148 return (uciWeight * internalWeight) / 0x100;
1152 // helper used in read_weights()
1153 int weight_option(const std::string& opt, int weight) {
1155 return compute_weight(get_option_value_int(opt), weight);
1159 // init_safety() initizes the king safety evaluation, based on UCI
1160 // parameters. It is called from read_weights().
1162 void init_safety() {
1164 QueenContactCheckBonus = get_option_value_int("Queen Contact Check Bonus");
1165 RookContactCheckBonus = get_option_value_int("Rook Contact Check Bonus");
1166 QueenCheckBonus = get_option_value_int("Queen Check Bonus");
1167 RookCheckBonus = get_option_value_int("Rook Check Bonus");
1168 BishopCheckBonus = get_option_value_int("Bishop Check Bonus");
1169 KnightCheckBonus = get_option_value_int("Knight Check Bonus");
1170 DiscoveredCheckBonus = get_option_value_int("Discovered Check Bonus");
1171 MateThreatBonus = get_option_value_int("Mate Threat Bonus");
1173 int maxSlope = get_option_value_int("King Safety Max Slope");
1174 int peak = get_option_value_int("King Safety Max Value") * 256 / 100;
1175 double a = get_option_value_int("King Safety Coefficient") / 100.0;
1176 double b = get_option_value_int("King Safety X Intercept");
1177 bool quad = (get_option_value_string("King Safety Curve") == "Quadratic");
1178 bool linear = (get_option_value_string("King Safety Curve") == "Linear");
1180 for (int i = 0; i < 100; i++)
1183 SafetyTable[i] = Value(0);
1185 SafetyTable[i] = Value((int)(a * (i - b) * (i - b)));
1187 SafetyTable[i] = Value((int)(100 * a * (i - b)));
1190 for (int i = 0; i < 100; i++)
1192 if (SafetyTable[i+1] - SafetyTable[i] > maxSlope)
1193 for (int j = i + 1; j < 100; j++)
1194 SafetyTable[j] = SafetyTable[j-1] + Value(maxSlope);
1196 if (SafetyTable[i] > Value(peak))
1197 SafetyTable[i] = Value(peak);