2 Glaurung, a UCI chess playing engine.
3 Copyright (C) 2004-2008 Tord Romstad
5 Glaurung is free software: you can redistribute it and/or modify
6 it under the terms of the GNU General Public License as published by
7 the Free Software Foundation, either version 3 of the License, or
8 (at your option) any later version.
10 Glaurung is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 GNU General Public License for more details.
15 You should have received a copy of the GNU General Public License
16 along with this program. If not, see <http://www.gnu.org/licenses/>.
32 #include "ucioption.h"
36 //// Local definitions
41 const int Sign[2] = {1, -1};
43 // Evaluation grain size, must be a power of 2.
44 const int GrainSize = 4;
47 int WeightMobilityMidgame = 0x100;
48 int WeightMobilityEndgame = 0x100;
49 int WeightPawnStructureMidgame = 0x100;
50 int WeightPawnStructureEndgame = 0x100;
51 int WeightPassedPawnsMidgame = 0x100;
52 int WeightPassedPawnsEndgame = 0x100;
53 int WeightKingSafety[2] = { 0x100, 0x100 };
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.
59 const int WeightMobilityMidgameInternal = 0x100;
60 const int WeightMobilityEndgameInternal = 0x100;
61 const int WeightPawnStructureMidgameInternal = 0x100;
62 const int WeightPawnStructureEndgameInternal = 0x100;
63 const int WeightPassedPawnsMidgameInternal = 0x100;
64 const int WeightPassedPawnsEndgameInternal = 0x100;
65 const int WeightKingSafetyInternal = 0x100;
66 const int WeightKingOppSafetyInternal = 0x100;
68 // Visually better to define tables constants
71 // Knight mobility bonus in middle game and endgame, indexed by the number
72 // of attacked squares not occupied by friendly piecess.
73 const Value MidgameKnightMobilityBonus[] = {
75 V(-30), V(-20),V(-10), V(0), V(10), V(20), V(25), V(30), V(30)
78 const Value EndgameKnightMobilityBonus[] = {
80 V(-30), V(-20),V(-10), V(0), V(10), V(20), V(25), V(30), V(30)
83 // Bishop mobility bonus in middle game and endgame, indexed by the number
84 // of attacked squares not occupied by friendly pieces. X-ray attacks through
85 // queens are also included.
86 const Value MidgameBishopMobilityBonus[] = {
88 V(-30), V(-15), V(0), V(15), V(30), V(45), V(58), V(66),
89 // 8 9 10 11 12 13 14 15
90 V( 72), V( 76), V(78), V(80), V(81), V(82), V(83), V(83)
93 const Value EndgameBishopMobilityBonus[] = {
95 V(-30), V(-15), V(0), V(15), V(30), V(45), V(58), V(66),
96 // 8 9 10 11 12 13 14 15
97 V( 72), V( 76), V(78), V(80), V(81), V(82), V(83), V(83)
100 // Rook mobility bonus in middle game and endgame, indexed by the number
101 // of attacked squares not occupied by friendly pieces. X-ray attacks through
102 // queens and rooks are also included.
103 const Value MidgameRookMobilityBonus[] = {
105 V(-18), V(-12), V(-6), V(0), V(6), V(12), V(16), V(21),
106 // 8 9 10 11 12 13 14 15
107 V( 24), V( 27), V(28), V(29), V(30), V(31), V(32), V(33)
110 const Value EndgameRookMobilityBonus[] = {
112 V(-30), V(-18), V(-6), V(6), V(18), V(30), V(42), V(54),
113 // 8 9 10 11 12 13 14 15
114 V( 66), V( 74), V(78), V(80), V(81), V(82), V(83), V(83)
117 // Queen mobility bonus in middle game and endgame, indexed by the number
118 // of attacked squares not occupied by friendly pieces.
119 const Value MidgameQueenMobilityBonus[] = {
121 V(-10), V(-8), V(-6), V(-4), V(-2), V( 0), V( 2), V( 4),
122 // 8 9 10 11 12 13 14 15
123 V( 6), V( 8), V(10), V(12), V(13), V(14), V(15), V(16),
124 // 16 17 18 19 20 21 22 23
125 V( 16), V(16), V(16), V(16), V(16), V(16), V(16), V(16),
126 // 24 25 26 27 28 29 30 31
127 V( 16), V(16), V(16), V(16), V(16), V(16), V(16), V(16)
130 const Value EndgameQueenMobilityBonus[] = {
132 V(-20),V(-15),V(-10), V(-5), V( 0), V( 5), V(10), V(15),
133 // 8 9 10 11 12 13 14 15
134 V( 19), V(23), V(27), V(29), V(30), V(30), V(30), V(30),
135 // 16 17 18 19 20 21 22 23
136 V( 30), V(30), V(30), V(30), V(30), V(30), V(30), V(30),
137 // 24 25 26 27 28 29 30 31
138 V( 30), V(30), V(30), V(30), V(30), V(30), V(30), V(30)
141 // Outpost bonuses for knights and bishops, indexed by square (from white's
143 const Value KnightOutpostBonus[64] = {
145 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 1
146 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 2
147 V(0), V(0), V(5),V(10),V(10), V(5), V(0), V(0), // 3
148 V(0), V(5),V(20),V(30),V(30),V(20), V(5), V(0), // 4
149 V(0),V(10),V(30),V(40),V(40),V(30),V(10), V(0), // 5
150 V(0), V(5),V(20),V(20),V(20),V(20), V(5), V(0), // 6
151 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 7
152 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0) // 8
155 const Value BishopOutpostBonus[64] = {
157 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 1
158 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 2
159 V(0), V(0), V(5), V(5), V(5), V(5), V(0), V(0), // 3
160 V(0), V(5),V(10),V(10),V(10),V(10), V(5), V(0), // 4
161 V(0),V(10),V(20),V(20),V(20),V(20),V(10), V(0), // 5
162 V(0), V(5), V(8), V(8), V(8), V(8), V(5), V(0), // 6
163 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 7
164 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0) // 8
167 // Bonus for unstoppable passed pawns:
168 const Value UnstoppablePawnValue = Value(0x500);
170 // Rooks and queens on the 7th rank:
171 const Value MidgameRookOn7thBonus = Value(50);
172 const Value EndgameRookOn7thBonus = Value(100);
173 const Value MidgameQueenOn7thBonus = Value(25);
174 const Value EndgameQueenOn7thBonus = Value(50);
176 // Rooks on open files:
177 const Value RookOpenFileBonus = Value(40);
178 const Value RookHalfOpenFileBonus = Value(20);
180 // Penalty for rooks trapped inside a friendly king which has lost the
182 const Value TrappedRookPenalty = Value(180);
184 // Penalty for a bishop on a7/h7 (a2/h2 for black) which is trapped by
186 const Value TrappedBishopA7H7Penalty = Value(300);
188 // Bitboard masks for detecting trapped bishops on a7/h7 (a2/h2 for black):
189 const Bitboard MaskA7H7[2] = {
190 ((1ULL << SQ_A7) | (1ULL << SQ_H7)),
191 ((1ULL << SQ_A2) | (1ULL << SQ_H2))
194 // Penalty for a bishop on a1/h1 (a8/h8 for black) which is trapped by
195 // a friendly pawn on b2/g2 (b7/g7 for black). This can obviously only
196 // happen in Chess960 games.
197 const Value TrappedBishopA1H1Penalty = Value(100);
199 // Bitboard masks for detecting trapped bishops on a1/h1 (a8/h8 for black):
200 const Bitboard MaskA1H1[2] = {
201 ((1ULL << SQ_A1) | (1ULL << SQ_H1)),
202 ((1ULL << SQ_A8) | (1ULL << SQ_H8))
205 /// King safety constants and variables. The king safety scores are taken
206 /// from the array SafetyTable[]. Various little "meta-bonuses" measuring
207 /// the strength of the attack are added up into an integer, which is used
208 /// as an index to SafetyTable[].
210 // Attack weights for each piece type.
211 const int QueenAttackWeight = 5;
212 const int RookAttackWeight = 3;
213 const int BishopAttackWeight = 2;
214 const int KnightAttackWeight = 2;
216 // Bonuses for safe checks for each piece type.
217 int QueenContactCheckBonus = 4;
218 int RookContactCheckBonus = 2;
219 int QueenCheckBonus = 2;
220 int RookCheckBonus = 1;
221 int BishopCheckBonus = 1;
222 int KnightCheckBonus = 1;
223 int DiscoveredCheckBonus = 3;
225 // Scan for queen contact mates?
226 const bool QueenContactMates = true;
228 // Bonus for having a mate threat.
229 int MateThreatBonus = 3;
231 // InitKingDanger[] contains bonuses based on the position of the defending
233 const int InitKingDanger[64] = {
234 2, 0, 2, 5, 5, 2, 0, 2,
235 2, 2, 4, 8, 8, 4, 2, 2,
236 7, 10, 12, 12, 12, 12, 10, 7,
237 15, 15, 15, 15, 15, 15, 15, 15,
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
244 // SafetyTable[] contains the actual king safety scores. It is initialized
246 Value SafetyTable[100];
248 // Pawn and material hash tables, indexed by the current thread id:
249 PawnInfoTable *PawnTable[8] = {0, 0, 0, 0, 0, 0, 0, 0};
250 MaterialInfoTable *MaterialTable[8] = {0, 0, 0, 0, 0, 0, 0, 0};
252 // Sizes of pawn and material hash tables:
253 const int PawnTableSize = 16384;
254 const int MaterialTableSize = 1024;
256 // Array which gives the number of nonzero bits in an 8-bit integer:
257 uint8_t BitCount8Bit[256];
259 // Function prototypes:
260 void evaluate_knight(const Position &p, Square s, Color us, EvalInfo &ei);
261 void evaluate_bishop(const Position &p, Square s, Color us, EvalInfo &ei);
262 void evaluate_rook(const Position &p, Square s, Color us, EvalInfo &ei);
263 void evaluate_queen(const Position &p, Square s, Color us, EvalInfo &ei);
264 void evaluate_king(const Position &p, Square s, Color us, EvalInfo &ei);
266 void evaluate_passed_pawns(const Position &pos, EvalInfo &ei);
267 void evaluate_trapped_bishop_a7h7(const Position &pos, Square s, Color us,
269 void evaluate_trapped_bishop_a1h1(const Position &pos, Square s, Color us,
272 inline Value apply_weight(Value v, int w);
273 Value scale_by_game_phase(Value mv, Value ev, Phase ph, ScaleFactor sf[]);
275 int count_1s_8bit(Bitboard b);
277 int compute_weight(int uciWeight, int internalWeight);
287 /// evaluate() is the main evaluation function. It always computes two
288 /// values, an endgame score and a middle game score, and interpolates
289 /// between them based on the remaining material.
291 Value evaluate(const Position &pos, EvalInfo &ei, int threadID) {
294 ScaleFactor factor[2] = {SCALE_FACTOR_NORMAL, SCALE_FACTOR_NORMAL};
297 memset(&ei, 0, sizeof(EvalInfo));
300 assert(threadID >= 0 && threadID < THREAD_MAX);
302 stm = pos.side_to_move();
304 // Initialize by reading the incrementally updated scores included in the
305 // position object (material + piece square tables):
306 ei.mgValue = pos.mg_value();
307 ei.egValue = pos.eg_value();
309 // Probe the material hash table:
310 ei.mi = MaterialTable[threadID]->get_material_info(pos);
311 ei.mgValue += ei.mi->mg_value();
312 ei.egValue += ei.mi->eg_value();
314 factor[WHITE] = ei.mi->scale_factor(pos, WHITE);
315 factor[BLACK] = ei.mi->scale_factor(pos, BLACK);
317 // If we have a specialized evaluation function for the current material
318 // configuration, call it and return:
319 if(ei.mi->specialized_eval_exists())
320 return ei.mi->evaluate(pos);
322 phase = pos.game_phase();
324 // Probe the pawn hash table:
325 ei.pi = PawnTable[threadID]->get_pawn_info(pos);
326 ei.mgValue += apply_weight(ei.pi->mg_value(), WeightPawnStructureMidgame);
327 ei.egValue += apply_weight(ei.pi->eg_value(), WeightPawnStructureEndgame);
329 // Initialize king attack bitboards and king attack zones for both sides:
330 ei.attackedBy[WHITE][KING] = pos.king_attacks(pos.king_square(WHITE));
331 ei.attackedBy[BLACK][KING] = pos.king_attacks(pos.king_square(BLACK));
333 ei.attackedBy[BLACK][KING] | (ei.attackedBy[BLACK][KING] >> 8);
335 ei.attackedBy[WHITE][KING] | (ei.attackedBy[WHITE][KING] << 8);
337 // Initialize pawn attack bitboards for both sides:
338 ei.attackedBy[WHITE][PAWN] =
339 ((pos.pawns(WHITE) << 9) & ~FileABB) | ((pos.pawns(WHITE) << 7) & ~FileHBB);
340 ei.kingAttackersCount[WHITE] +=
341 count_1s_max_15(ei.attackedBy[WHITE][PAWN] & ei.attackedBy[BLACK][KING])/2;
342 ei.attackedBy[BLACK][PAWN] =
343 ((pos.pawns(BLACK) >> 7) & ~FileABB) | ((pos.pawns(BLACK) >> 9) & ~FileHBB);
344 ei.kingAttackersCount[BLACK] +=
345 count_1s_max_15(ei.attackedBy[BLACK][PAWN] & ei.attackedBy[WHITE][KING])/2;
348 for(Color c = WHITE; c <= BLACK; c++) {
352 for(int i = 0; i < pos.knight_count(c); i++) {
353 s = pos.knight_list(c, i);
354 evaluate_knight(pos, s, c, ei);
358 for(int i = 0; i < pos.bishop_count(c); i++) {
359 s = pos.bishop_list(c, i);
360 evaluate_bishop(pos, s, c, ei);
364 for(int i = 0; i < pos.rook_count(c); i++) {
365 s = pos.rook_list(c, i);
366 evaluate_rook(pos, s, c, ei);
370 for(int i = 0; i < pos.queen_count(c); i++) {
371 s = pos.queen_list(c, i);
372 evaluate_queen(pos, s, c, ei);
375 // Some special patterns:
377 // Trapped bishops on a7/h7/a2/h2
378 b = pos.bishops(c) & MaskA7H7[c];
381 evaluate_trapped_bishop_a7h7(pos, s, c, ei);
384 // Trapped bishops on a1/h1/a8/h8 in Chess960:
386 b = pos.bishops(c) & MaskA1H1[c];
389 evaluate_trapped_bishop_a1h1(pos, s, c, ei);
393 ei.attackedBy[c][0] =
394 ei.attackedBy[c][PAWN] | ei.attackedBy[c][KNIGHT]
395 | ei.attackedBy[c][BISHOP] | ei.attackedBy[c][ROOK]
396 | ei.attackedBy[c][QUEEN] | ei.attackedBy[c][KING];
399 // Kings. Kings are evaluated after all other pieces for both sides,
400 // because we need complete attack information for all pieces when computing
401 // the king safety evaluation.
402 for(Color c = WHITE; c <= BLACK; c++) {
403 s = pos.king_square(c);
404 evaluate_king(pos, s, c, ei);
407 // Evaluate passed pawns. We evaluate passed pawns for both sides at once,
408 // because we need to know which side promotes first in positions where
409 // both sides have an unstoppable passed pawn.
410 if(ei.pi->passed_pawns())
411 evaluate_passed_pawns(pos, ei);
413 // Middle-game specific evaluation terms
414 if(phase > PHASE_ENDGAME) {
416 // Pawn storms in positions with opposite castling.
417 if(square_file(pos.king_square(WHITE)) >= FILE_E &&
418 square_file(pos.king_square(BLACK)) <= FILE_D)
420 ei.pi->queenside_storm_value(WHITE) -
421 ei.pi->kingside_storm_value(BLACK);
422 else if(square_file(pos.king_square(WHITE)) <= FILE_D &&
423 square_file(pos.king_square(BLACK)) >= FILE_E)
425 ei.pi->kingside_storm_value(WHITE) -
426 ei.pi->queenside_storm_value(BLACK);
430 ei.mgValue += apply_weight(ei.mgMobility, WeightMobilityMidgame);
431 ei.egValue += apply_weight(ei.egMobility, WeightMobilityEndgame);
433 // If we don't already have an unusual scale factor, check for opposite
434 // colored bishop endgames, and use a lower scale for those:
435 if(phase < PHASE_MIDGAME && pos.opposite_colored_bishops()
436 && ((factor[WHITE] == SCALE_FACTOR_NORMAL && ei.egValue > Value(0)) ||
437 (factor[BLACK] == SCALE_FACTOR_NORMAL && ei.egValue < Value(0)))) {
438 if(pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK) ==
439 2*BishopValueMidgame) {
440 // Only the two bishops
441 if(pos.pawn_count(WHITE) + pos.pawn_count(BLACK) == 1) {
442 // KBP vs KB with only a single pawn; almost certainly a draw.
443 if(factor[WHITE] == SCALE_FACTOR_NORMAL)
444 factor[WHITE] = ScaleFactor(8);
445 if(factor[BLACK] == SCALE_FACTOR_NORMAL)
446 factor[BLACK] = ScaleFactor(8);
449 // At least two pawns
450 if(factor[WHITE] == SCALE_FACTOR_NORMAL)
451 factor[WHITE] = ScaleFactor(32);
452 if(factor[BLACK] == SCALE_FACTOR_NORMAL)
453 factor[BLACK] = ScaleFactor(32);
457 // Endgame with opposite-colored bishops, but also other pieces.
458 // Still a bit drawish, but not as drawish as with only the two
460 if(factor[WHITE] == SCALE_FACTOR_NORMAL)
461 factor[WHITE] = ScaleFactor(50);
462 if(factor[BLACK] == SCALE_FACTOR_NORMAL)
463 factor[BLACK] = ScaleFactor(50);
467 // Interpolate between the middle game and the endgame score, and
469 Value value = scale_by_game_phase(ei.mgValue, ei.egValue, phase, factor);
471 if(ei.mateThreat[stm] != MOVE_NONE)
472 return 8 * QueenValueMidgame - Sign[stm] * value;
474 return Sign[stm] * value;
478 /// quick_evaluate() does a very approximate evaluation of the current position.
479 /// It currently considers only material and piece square table scores. Perhaps
480 /// we should add scores from the pawn and material hash tables?
482 Value quick_evaluate(const Position &pos) {
484 Value mgValue, egValue;
485 ScaleFactor factor[2] = {SCALE_FACTOR_NORMAL, SCALE_FACTOR_NORMAL};
490 stm = pos.side_to_move();
492 mgValue = pos.mg_value();
493 egValue = pos.eg_value();
494 phase = pos.game_phase();
496 Value value = scale_by_game_phase(mgValue, egValue, phase, factor);
498 return Sign[stm] * value;
502 /// init_eval() initializes various tables used by the evaluation function.
504 void init_eval(int threads) {
506 assert(threads <= THREAD_MAX);
508 for (int i = 0; i < THREAD_MAX; i++)
513 delete MaterialTable[i];
515 MaterialTable[i] = NULL;
519 PawnTable[i] = new PawnInfoTable(PawnTableSize);
520 if (!MaterialTable[i])
521 MaterialTable[i] = new MaterialInfoTable(MaterialTableSize);
524 for (Bitboard b = 0ULL; b < 256ULL; b++)
525 BitCount8Bit[b] = count_1s(b);
529 /// quit_eval() releases heap-allocated memory at program termination.
532 for(int i = 0; i < THREAD_MAX; i++) {
534 delete MaterialTable[i];
539 /// read_weights() reads evaluation weights from the corresponding UCI
542 int weight_option(const std::string& opt, int weight) {
544 return compute_weight(get_option_value_int(opt), weight);
547 void read_weights(Color us) {
549 WeightMobilityMidgame = weight_option("Mobility (Middle Game)", WeightMobilityMidgameInternal);
550 WeightMobilityEndgame = weight_option("Mobility (Endgame)", WeightMobilityEndgameInternal);
551 WeightPawnStructureMidgame = weight_option("Pawn Structure (Middle Game)", WeightPawnStructureMidgameInternal);
552 WeightPawnStructureEndgame = weight_option("Pawn Structure (Endgame)", WeightPawnStructureEndgameInternal);
553 WeightPassedPawnsMidgame = weight_option("Passed Pawns (Middle Game)", WeightPassedPawnsMidgameInternal);
554 WeightPassedPawnsEndgame = weight_option("Passed Pawns (Endgame)", WeightPassedPawnsEndgameInternal);
556 Color them = opposite_color(us);
558 WeightKingSafety[us] = weight_option("Cowardice", WeightKingSafetyInternal);
559 WeightKingSafety[them] = weight_option("Aggressiveness", WeightKingOppSafetyInternal);
567 // evaluate_common() computes terms common to all pieces attack
569 int evaluate_common(const Position&p, const Bitboard& b, Color us, EvalInfo& ei,
570 int AttackWeight, const Value* mgBonus, const Value* egBonus,
571 Square s = SQ_NONE, const Value* OutpostBonus = NULL) {
573 Color them = opposite_color(us);
576 if (b & ei.kingZone[us])
578 ei.kingAttackersCount[us]++;
579 ei.kingAttackersWeight[us] += AttackWeight;
580 Bitboard bb = (b & ei.attackedBy[them][KING]);
582 ei.kingZoneAttacksCount[us] += count_1s_max_15(bb);
586 int mob = count_1s_max_15(b & ~p.pieces_of_color(us));
587 ei.mgMobility += Sign[us] * mgBonus[mob];
588 ei.egMobility += Sign[us] * egBonus[mob];
590 // Bishop and Knight outposts
591 if (!OutpostBonus || !p.square_is_weak(s, them))
594 // Initial bonus based on square
596 v = bonus = OutpostBonus[relative_square(us, s)];
598 // Increase bonus if supported by pawn, especially if the opponent has
599 // no minor piece which can exchange the outpost piece
600 if (v && (p.pawn_attacks(them, s) & p.pawns(us)))
603 if ( p.knight_count(them) == 0
604 && (SquaresByColorBB[square_color(s)] & p.bishops(them)) == EmptyBoardBB)
607 ei.mgValue += Sign[us] * bonus;
608 ei.egValue += Sign[us] * bonus;
613 // evaluate_knight() assigns bonuses and penalties to a knight of a given
614 // color on a given square.
616 void evaluate_knight(const Position &p, Square s, Color us, EvalInfo &ei) {
618 Bitboard b = p.knight_attacks(s);
619 ei.attackedBy[us][KNIGHT] |= b;
621 // King attack, mobility and outposts
622 evaluate_common(p, b, us, ei, KnightAttackWeight, MidgameKnightMobilityBonus,
623 EndgameKnightMobilityBonus, s, KnightOutpostBonus);
627 // evaluate_bishop() assigns bonuses and penalties to a bishop of a given
628 // color on a given square.
630 void evaluate_bishop(const Position &p, Square s, Color us, EvalInfo &ei) {
632 Bitboard b = bishop_attacks_bb(s, p.occupied_squares() & ~p.queens(us));
633 ei.attackedBy[us][BISHOP] |= b;
635 // King attack, mobility and outposts
636 evaluate_common(p, b, us, ei, BishopAttackWeight, MidgameBishopMobilityBonus,
637 EndgameBishopMobilityBonus, s, BishopOutpostBonus);
641 // evaluate_rook() assigns bonuses and penalties to a rook of a given
642 // color on a given square.
644 void evaluate_rook(const Position &p, Square s, Color us, EvalInfo &ei) {
646 //Bitboard b = p.rook_attacks(s);
647 Bitboard b = rook_attacks_bb(s, p.occupied_squares() & ~p.rooks_and_queens(us));
648 ei.attackedBy[us][ROOK] |= b;
650 // King attack and mobility
651 int mob = evaluate_common(p, b, us, ei, RookAttackWeight, MidgameRookMobilityBonus,
652 EndgameRookMobilityBonus);
655 Color them = opposite_color(us);
657 if ( relative_rank(us, s) == RANK_7
658 && relative_rank(us, p.king_square(them)) == RANK_8)
660 ei.mgValue += Sign[us] * MidgameRookOn7thBonus;
661 ei.egValue += Sign[us] * EndgameRookOn7thBonus;
664 // Open and half-open files
665 File f = square_file(s);
666 if (ei.pi->file_is_half_open(us, f))
668 if (ei.pi->file_is_half_open(them, f))
670 ei.mgValue += Sign[us] * RookOpenFileBonus;
671 ei.egValue += Sign[us] * RookOpenFileBonus;
675 ei.mgValue += Sign[us] * RookHalfOpenFileBonus;
676 ei.egValue += Sign[us] * RookHalfOpenFileBonus;
680 // Penalize rooks which are trapped inside a king. Penalize more if
681 // king has lost right to castle
682 if (mob > 6 || ei.pi->file_is_half_open(us, f))
685 Square ksq = p.king_square(us);
687 if ( square_file(ksq) >= FILE_E
688 && square_file(s) > square_file(ksq)
689 && (relative_rank(us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
691 // Is there a half-open file between the king and the edge of the board?
692 if (!ei.pi->has_open_file_to_right(us, square_file(ksq)))
693 ei.mgValue -= p.can_castle(us)? Sign[us] * ((TrappedRookPenalty - mob * 16) / 2)
694 : Sign[us] * (TrappedRookPenalty - mob * 16);
696 else if ( square_file(ksq) <= FILE_D
697 && square_file(s) < square_file(ksq)
698 && (relative_rank(us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
700 // Is there a half-open file between the king and the edge of the board?
701 if (!ei.pi->has_open_file_to_left(us, square_file(ksq)))
702 ei.mgValue -= p.can_castle(us)? Sign[us] * ((TrappedRookPenalty - mob * 16) / 2)
703 : Sign[us] * (TrappedRookPenalty - mob * 16);
708 // evaluate_queen() assigns bonuses and penalties to a queen of a given
709 // color on a given square.
711 void evaluate_queen(const Position &p, Square s, Color us, EvalInfo &ei) {
713 Bitboard b = p.queen_attacks(s);
714 ei.attackedBy[us][QUEEN] |= b;
716 // King attack and mobility
717 evaluate_common(p, b, us, ei, QueenAttackWeight, MidgameQueenMobilityBonus,
718 EndgameQueenMobilityBonus);
721 Color them = opposite_color(us);
723 if ( relative_rank(us, s) == RANK_7
724 && relative_rank(us, p.king_square(them)) == RANK_8)
726 ei.mgValue += Sign[us] * MidgameQueenOn7thBonus;
727 ei.egValue += Sign[us] * EndgameQueenOn7thBonus;
732 // evaluate_king() assigns bonuses and penalties to a king of a given
733 // color on a given square.
735 void evaluate_king(const Position &p, Square s, Color us, EvalInfo &ei) {
737 int shelter = 0, sign = Sign[us];
740 if(relative_rank(us, s) <= RANK_4) {
741 Bitboard pawns = p.pawns(us) & this_and_neighboring_files_bb(s);
742 Rank r = square_rank(s);
743 for(int i = 0; i < 3; i++)
744 shelter += count_1s_8bit(pawns >> ((r+(i+1)*sign) * 8)) * (64>>i);
745 ei.mgValue += sign * Value(shelter);
748 // King safety. This is quite complicated, and is almost certainly far
749 // from optimally tuned.
750 Color them = opposite_color(us);
751 if(p.queen_count(them) >= 1 && ei.kingAttackersCount[them] >= 2
752 && p.non_pawn_material(them) >= QueenValueMidgame + RookValueMidgame
753 && ei.kingZoneAttacksCount[them]) {
755 // Is it the attackers turn to move?
756 bool sente = (them == p.side_to_move());
758 // Find the attacked squares around the king which has no defenders
759 // apart from the king itself:
760 Bitboard undefended =
761 ei.attacked_by(them) & ~ei.attacked_by(us, PAWN)
762 & ~ei.attacked_by(us, KNIGHT) & ~ei.attacked_by(us, BISHOP)
763 & ~ei.attacked_by(us, ROOK) & ~ei.attacked_by(us, QUEEN)
764 & ei.attacked_by(us, KING);
765 Bitboard occ = p.occupied_squares(), b, b2;
767 // Initialize the 'attackUnits' variable, which is used later on as an
768 // index to the SafetyTable[] array. The initial is based on the number
769 // and types of the attacking pieces, the number of attacked and
770 // undefended squares around the king, the square of the king, and the
771 // quality of the pawn shelter.
773 Min((ei.kingAttackersCount[them] * ei.kingAttackersWeight[them]) / 2, 25)
774 + (ei.kingZoneAttacksCount[them] + count_1s_max_15(undefended)) * 3
775 + InitKingDanger[relative_square(us, s)] - shelter / 32;
777 // Analyse safe queen contact checks:
778 b = undefended & ei.attacked_by(them, QUEEN) & ~p.pieces_of_color(them);
780 Bitboard attackedByOthers =
781 ei.attacked_by(them, PAWN) | ei.attacked_by(them, KNIGHT)
782 | ei.attacked_by(them, BISHOP) | ei.attacked_by(them, ROOK);
783 b &= attackedByOthers;
785 // The bitboard b now contains the squares available for safe queen
787 int count = count_1s_max_15(b);
788 attackUnits += QueenContactCheckBonus * count * (sente? 2 : 1);
790 // Is there a mate threat?
791 if(QueenContactMates && !p.is_check()) {
792 Bitboard escapeSquares =
793 p.king_attacks(s) & ~p.pieces_of_color(us) & ~attackedByOthers;
795 Square from, to = pop_1st_bit(&b);
797 & ~queen_attacks_bb(to, occ & clear_mask_bb(s)))) {
798 // We have a mate, unless the queen is pinned or there
799 // is an X-ray attack through the queen.
800 for(int i = 0; i < p.queen_count(them); i++) {
801 from = p.queen_list(them, i);
802 if(bit_is_set(p.queen_attacks(from), to)
803 && !bit_is_set(p.pinned_pieces(them), from)
804 && !(rook_attacks_bb(to, occ & clear_mask_bb(from))
805 & p.rooks_and_queens(us))
806 && !(rook_attacks_bb(to, occ & clear_mask_bb(from))
807 & p.rooks_and_queens(us)))
808 ei.mateThreat[them] = make_move(from, to);
816 // Analyse safe rook contact checks:
817 if(RookContactCheckBonus) {
818 b = undefended & ei.attacked_by(them, ROOK) & ~p.pieces_of_color(them);
820 Bitboard attackedByOthers =
821 ei.attacked_by(them, PAWN) | ei.attacked_by(them, KNIGHT)
822 | ei.attacked_by(them, BISHOP) | ei.attacked_by(them, QUEEN);
823 b &= attackedByOthers;
825 int count = count_1s_max_15(b);
826 attackUnits += (RookContactCheckBonus * count * (sente? 2 : 1));
831 // Analyse safe distance checks:
832 if(QueenCheckBonus > 0 || RookCheckBonus > 0) {
833 b = p.rook_attacks(s) & ~p.pieces_of_color(them) & ~ei.attacked_by(us);
836 b2 = b & ei.attacked_by(them, QUEEN);
837 if(b2) attackUnits += QueenCheckBonus * count_1s_max_15(b2);
840 b2 = b & ei.attacked_by(them, ROOK);
841 if(b2) attackUnits += RookCheckBonus * count_1s_max_15(b2);
843 if(QueenCheckBonus > 0 || BishopCheckBonus > 0) {
844 b = p.bishop_attacks(s) & ~p.pieces_of_color(them) & ~ei.attacked_by(us);
846 b2 = b & ei.attacked_by(them, QUEEN);
847 if(b2) attackUnits += QueenCheckBonus * count_1s_max_15(b2);
850 b2 = b & ei.attacked_by(them, BISHOP);
851 if(b2) attackUnits += BishopCheckBonus * count_1s_max_15(b2);
853 if(KnightCheckBonus > 0) {
854 b = p.knight_attacks(s) & ~p.pieces_of_color(them) & ~ei.attacked_by(us);
856 b2 = b & ei.attacked_by(them, KNIGHT);
857 if(b2) attackUnits += KnightCheckBonus * count_1s_max_15(b2);
860 // Analyse discovered checks (only for non-pawns right now, consider
861 // adding pawns later).
862 if(DiscoveredCheckBonus) {
863 b = p.discovered_check_candidates(them) & ~p.pawns();
866 DiscoveredCheckBonus * count_1s_max_15(b) * (sente? 2 : 1);
869 // Has a mate threat been found? We don't do anything here if the
870 // side with the mating move is the side to move, because in that
871 // case the mating side will get a huge bonus at the end of the main
872 // evaluation function instead.
873 if(ei.mateThreat[them] != MOVE_NONE)
874 attackUnits += MateThreatBonus;
876 // Ensure that attackUnits is between 0 and 99, in order to avoid array
877 // out of bounds errors:
878 if(attackUnits < 0) attackUnits = 0;
879 if(attackUnits >= 100) attackUnits = 99;
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]);
888 ei.mgValue -= sign * v;
889 if(us == p.side_to_move())
890 ei.futilityMargin += v;
895 // evaluate_passed_pawns() evaluates the passed pawns for both sides.
897 void evaluate_passed_pawns(const Position &pos, EvalInfo &ei) {
898 bool hasUnstoppable[2] = {false, false};
899 int movesToGo[2] = {100, 100};
901 for(Color us = WHITE; us <= BLACK; us++) {
902 Color them = opposite_color(us);
903 Square ourKingSq = pos.king_square(us);
904 Square theirKingSq = pos.king_square(them);
905 Bitboard b = ei.pi->passed_pawns() & pos.pawns(us), b2, b3, b4;
908 Square s = pop_1st_bit(&b);
909 assert(pos.piece_on(s) == pawn_of_color(us));
910 assert(pos.pawn_is_passed(us, s));
912 int r = int(relative_rank(us, s) - RANK_2);
913 int tr = Max(0, r * (r-1));
914 Square blockSq = s + pawn_push(us);
916 // Base bonus based on rank:
917 Value mbonus = Value(20 * tr);
918 Value ebonus = Value(10 + r * r * 10);
920 // Adjust bonus based on king proximity:
921 ebonus -= Value(square_distance(ourKingSq, blockSq) * 3 * tr);
923 Value(square_distance(ourKingSq, blockSq + pawn_push(us)) * 1 * tr);
924 ebonus += Value(square_distance(theirKingSq, blockSq) * 6 * tr);
926 // If the pawn is free to advance, increase bonus:
927 if(pos.square_is_empty(blockSq)) {
929 b2 = squares_in_front_of(us, s);
930 b3 = b2 & ei.attacked_by(them);
931 b4 = b2 & ei.attacked_by(us);
932 if((b2 & pos.pieces_of_color(them)) == EmptyBoardBB) {
933 // There are no enemy pieces in the pawn's path! Are any of the
934 // squares in the pawn's path attacked by the enemy?
935 if(b3 == EmptyBoardBB)
936 // No enemy attacks, huge bonus!
937 ebonus += Value(tr * ((b2 == b4)? 17 : 15));
939 // OK, there are enemy attacks. Are those squares which are
940 // attacked by the enemy also attacked by us? If yes, big bonus
941 // (but smaller than when there are no enemy attacks), if no,
942 // somewhat smaller bonus.
943 ebonus += Value(tr * (((b3 & b4) == b3)? 13 : 8));
946 // There are some enemy pieces in the pawn's path. While this is
947 // sad, we still assign a moderate bonus if all squares in the path
948 // which are either occupied by or attacked by enemy pieces are
949 // also attacked by us.
950 if(((b3 | (b2 & pos.pieces_of_color(them))) & ~b4) == EmptyBoardBB)
951 ebonus += Value(tr * 6);
953 // At last, add a small bonus when there are no *friendly* pieces
954 // in the pawn's path:
955 if((b2 & pos.pieces_of_color(us)) == EmptyBoardBB)
959 // If the pawn is supported by a friendly pawn, increase bonus.
960 b2 = pos.pawns(us) & neighboring_files_bb(s);
962 ebonus += Value(r * 20);
963 else if(pos.pawn_attacks(them, s) & b2)
964 ebonus += Value(r * 12);
966 // If the other side has only a king, check whether the pawn is
968 if(pos.non_pawn_material(them) == Value(0)) {
972 qsq = relative_square(us, make_square(square_file(s), RANK_8));
973 d = square_distance(s, qsq) - square_distance(theirKingSq, qsq)
974 + ((us == pos.side_to_move())? 0 : 1);
977 int mtg = RANK_8 - relative_rank(us, s);
979 count_1s_max_15(squares_in_front_of(us,s)&pos.occupied_squares());
983 hasUnstoppable[us] = true;
984 movesToGo[us] = Min(movesToGo[us], mtg);
988 // Rook pawns are a special case: They are sometimes worse, and
989 // sometimes better than other passed pawns. It is difficult to find
990 // good rules for determining whether they are good or bad. For now,
991 // we try the following: Increase the value for rook pawns if the
992 // other side has no pieces apart from a knight, and decrease the
993 // value if the other side has a rook or queen.
994 if(square_file(s) == FILE_A || square_file(s) == FILE_H) {
995 if(pos.non_pawn_material(them) == KnightValueMidgame
996 && pos.knight_count(them) == 1)
997 ebonus += ebonus / 4;
998 else if(pos.rooks_and_queens(them))
999 ebonus -= ebonus / 4;
1002 // Add the scores for this pawn to the middle game and endgame eval.
1003 ei.mgValue += apply_weight(Sign[us] * mbonus, WeightPassedPawnsMidgame);
1004 ei.egValue += apply_weight(Sign[us] * ebonus, WeightPassedPawnsEndgame);
1008 // Does either side have an unstoppable passed pawn?
1009 if(hasUnstoppable[WHITE] && !hasUnstoppable[BLACK])
1010 ei.egValue += UnstoppablePawnValue - Value(0x40 * movesToGo[WHITE]);
1011 else if(hasUnstoppable[BLACK] && !hasUnstoppable[WHITE])
1012 ei.egValue -= UnstoppablePawnValue - Value(0x40 * movesToGo[BLACK]);
1013 else if(hasUnstoppable[BLACK] && hasUnstoppable[WHITE]) {
1014 // Both sides have unstoppable pawns! Try to find out who queens
1015 // first. We begin by transforming 'movesToGo' to the number of
1016 // plies until the pawn queens for both sides:
1017 movesToGo[WHITE] *= 2;
1018 movesToGo[BLACK] *= 2;
1019 movesToGo[pos.side_to_move()]--;
1021 // If one side queens at least three plies before the other, that
1023 if(movesToGo[WHITE] <= movesToGo[BLACK] - 3)
1024 ei.egValue += UnstoppablePawnValue - Value(0x40 * (movesToGo[WHITE]/2));
1025 else if(movesToGo[BLACK] <= movesToGo[WHITE] - 3)
1026 ei.egValue -= UnstoppablePawnValue - Value(0x40 * (movesToGo[BLACK]/2));
1028 // We could also add some rules about the situation when one side
1029 // queens exactly one ply before the other: Does the first queen
1030 // check the opponent's king, or attack the opponent's queening square?
1031 // This is slightly tricky to get right, because it is possible that
1032 // the opponent's king has moved somewhere before the first pawn queens.
1037 // evaluate_trapped_bishop_a7h7() determines whether a bishop on a7/h7
1038 // (a2/h2 for black) is trapped by enemy pawns, and assigns a penalty
1041 void evaluate_trapped_bishop_a7h7(const Position &pos, Square s, Color us,
1044 assert(square_is_ok(s));
1045 assert(pos.piece_on(s) == bishop_of_color(us));
1047 Square b6 = relative_square(us, (square_file(s) == FILE_A) ? SQ_B6 : SQ_G6);
1048 Square b8 = relative_square(us, (square_file(s) == FILE_A) ? SQ_B8 : SQ_G8);
1050 if ( pos.piece_on(b6) == pawn_of_color(opposite_color(us))
1051 && pos.see(s, b6) < 0
1052 && pos.see(s, b8) < 0)
1054 ei.mgValue -= Sign[us] * TrappedBishopA7H7Penalty;
1055 ei.egValue -= Sign[us] * TrappedBishopA7H7Penalty;
1060 // evaluate_trapped_bishop_a1h1() determines whether a bishop on a1/h1
1061 // (a8/h8 for black) is trapped by a friendly pawn on b2/g2 (b7/g7 for
1062 // black), and assigns a penalty if it is. This pattern can obviously
1063 // only occur in Chess960 games.
1065 void evaluate_trapped_bishop_a1h1(const Position &pos, Square s, Color us,
1067 Piece pawn = pawn_of_color(us);
1071 assert(square_is_ok(s));
1072 assert(pos.piece_on(s) == bishop_of_color(us));
1074 if(square_file(s) == FILE_A) {
1075 b2 = relative_square(us, SQ_B2);
1076 b3 = relative_square(us, SQ_B3);
1077 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) {
1088 if(!pos.square_is_empty(b3))
1089 penalty = 2*TrappedBishopA1H1Penalty;
1090 else if(pos.piece_on(c3) == pawn)
1091 penalty = TrappedBishopA1H1Penalty;
1093 penalty = TrappedBishopA1H1Penalty / 2;
1095 ei.mgValue -= Sign[us] * penalty;
1096 ei.egValue -= Sign[us] * penalty;
1102 // apply_weight applies an evaluation weight to a value.
1104 inline Value apply_weight(Value v, int w) {
1105 return (v*w) / 0x100;
1109 // scale_by_game_phase interpolates between a middle game and an endgame
1110 // score, based on game phase. It also scales the return value by a
1111 // ScaleFactor array.
1113 Value scale_by_game_phase(Value mv, Value ev, Phase ph, ScaleFactor sf[]) {
1115 assert(mv > -VALUE_INFINITE && mv < VALUE_INFINITE);
1116 assert(ev > -VALUE_INFINITE && ev < VALUE_INFINITE);
1117 assert(ph >= PHASE_ENDGAME && ph <= PHASE_MIDGAME);
1119 ev = apply_scale_factor(ev, sf[(ev > Value(0) ? WHITE : BLACK)]);
1121 // Linearized sigmoid interpolator
1123 sph -= (64 - sph) / 4;
1124 sph = Min(PHASE_MIDGAME, Max(PHASE_ENDGAME, sph));
1126 Value result = Value(int((mv * sph + ev * (128 - sph)) / 128));
1128 return Value(int(result) & ~(GrainSize - 1));
1132 // count_1s_8bit() counts the number of nonzero bits in the 8 least
1133 // significant bits of a Bitboard. This function is used by the king
1134 // shield evaluation.
1136 int count_1s_8bit(Bitboard b) {
1137 return int(BitCount8Bit[b & 0xFF]);
1141 // compute_weight() computes the value of an evaluation weight, by combining
1142 // an UCI-configurable weight with an internal weight.
1144 int compute_weight(int uciWeight, int internalWeight) {
1145 uciWeight = (uciWeight * 0x100) / 100;
1146 return (uciWeight * internalWeight) / 0x100;
1150 // init_safety() initizes the king safety evaluation, based on UCI
1151 // parameters. It is called from read_weights().
1153 void init_safety() {
1155 QueenContactCheckBonus = get_option_value_int("Queen Contact Check Bonus");
1156 RookContactCheckBonus = get_option_value_int("Rook Contact Check Bonus");
1157 QueenCheckBonus = get_option_value_int("Queen Check Bonus");
1158 RookCheckBonus = get_option_value_int("Rook Check Bonus");
1159 BishopCheckBonus = get_option_value_int("Bishop Check Bonus");
1160 KnightCheckBonus = get_option_value_int("Knight Check Bonus");
1161 DiscoveredCheckBonus = get_option_value_int("Discovered Check Bonus");
1162 MateThreatBonus = get_option_value_int("Mate Threat Bonus");
1164 int maxSlope = get_option_value_int("King Safety Max Slope");
1165 int peak = get_option_value_int("King Safety Max Value") * 256 / 100;
1166 double a = get_option_value_int("King Safety Coefficient") / 100.0;
1167 double b = get_option_value_int("King Safety X Intercept");
1168 bool quad = (get_option_value_string("King Safety Curve") == "Quadratic");
1169 bool linear = (get_option_value_string("King Safety Curve") == "Linear");
1171 for (int i = 0; i < 100; i++)
1174 SafetyTable[i] = Value(0);
1176 SafetyTable[i] = Value((int)(a * (i - b) * (i - b)));
1178 SafetyTable[i] = Value((int)(100 * a * (i - b)));
1181 for (int i = 0; i < 100; i++)
1183 if (SafetyTable[i+1] - SafetyTable[i] > maxSlope)
1184 for (int j = i + 1; j < 100; j++)
1185 SafetyTable[j] = SafetyTable[j-1] + Value(maxSlope);
1187 if (SafetyTable[i] > Value(peak))
1188 SafetyTable[i] = Value(peak);