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;
67 // Visually better to define tables constants
70 // Knight mobility bonus in middle game and endgame, indexed by the number
71 // of attacked squares not occupied by friendly piecess.
72 const Value MidgameKnightMobilityBonus[] = {
74 V(-30), V(-20),V(-10), V(0), V(10), V(20), V(25), V(30), V(30)
77 const Value EndgameKnightMobilityBonus[] = {
79 V(-30), V(-20),V(-10), V(0), V(10), V(20), V(25), V(30), V(30)
82 // Bishop mobility bonus in middle game and endgame, indexed by the number
83 // of attacked squares not occupied by friendly pieces. X-ray attacks through
84 // queens are also included.
85 const Value MidgameBishopMobilityBonus[] = {
87 V(-30), V(-15), V(0), V(15), V(30), V(45), V(58), V(66),
88 // 8 9 10 11 12 13 14 15
89 V( 72), V( 76), V(78), V(80), V(81), V(82), V(83), V(83)
92 const Value EndgameBishopMobilityBonus[] = {
94 V(-30), V(-15), V(0), V(15), V(30), V(45), V(58), V(66),
95 // 8 9 10 11 12 13 14 15
96 V( 72), V( 76), V(78), V(80), V(81), V(82), V(83), V(83)
99 // Rook mobility bonus in middle game and endgame, indexed by the number
100 // of attacked squares not occupied by friendly pieces. X-ray attacks through
101 // queens and rooks are also included.
102 const Value MidgameRookMobilityBonus[] = {
104 V(-18), V(-12), V(-6), V(0), V(6), V(12), V(16), V(21),
105 // 8 9 10 11 12 13 14 15
106 V( 24), V( 27), V(28), V(29), V(30), V(31), V(32), V(33)
109 const Value EndgameRookMobilityBonus[] = {
111 V(-30), V(-18), V(-6), V(6), V(18), V(30), V(42), V(54),
112 // 8 9 10 11 12 13 14 15
113 V( 66), V( 74), V(78), V(80), V(81), V(82), V(83), V(83)
116 // Queen mobility bonus in middle game and endgame, indexed by the number
117 // of attacked squares not occupied by friendly pieces.
118 const Value MidgameQueenMobilityBonus[] = {
120 V(-10), V(-8), V(-6), V(-4), V(-2), V( 0), V( 2), V( 4),
121 // 8 9 10 11 12 13 14 15
122 V( 6), V( 8), V(10), V(12), V(13), V(14), V(15), V(16),
123 // 16 17 18 19 20 21 22 23
124 V( 16), V(16), V(16), V(16), V(16), V(16), V(16), V(16),
125 // 24 25 26 27 28 29 30 31
126 V( 16), V(16), V(16), V(16), V(16), V(16), V(16), V(16)
129 const Value EndgameQueenMobilityBonus[] = {
131 V(-20),V(-15),V(-10), V(-5), V( 0), V( 5), V(10), V(15),
132 // 8 9 10 11 12 13 14 15
133 V( 19), V(23), V(27), V(29), V(30), V(30), V(30), V(30),
134 // 16 17 18 19 20 21 22 23
135 V( 30), V(30), V(30), V(30), V(30), V(30), V(30), V(30),
136 // 24 25 26 27 28 29 30 31
137 V( 30), V(30), V(30), V(30), V(30), V(30), V(30), V(30)
140 // Outpost bonuses for knights and bishops, indexed by square (from white's
142 const Value KnightOutpostBonus[64] = {
144 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 1
145 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 2
146 V(0), V(0), V(5),V(10),V(10), V(5), V(0), V(0), // 3
147 V(0), V(5),V(20),V(30),V(30),V(20), V(5), V(0), // 4
148 V(0),V(10),V(30),V(40),V(40),V(30),V(10), V(0), // 5
149 V(0), V(5),V(20),V(20),V(20),V(20), V(5), V(0), // 6
150 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 7
151 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0) // 8
154 const Value BishopOutpostBonus[64] = {
156 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 1
157 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 2
158 V(0), V(0), V(5), V(5), V(5), V(5), V(0), V(0), // 3
159 V(0), V(5),V(10),V(10),V(10),V(10), V(5), V(0), // 4
160 V(0),V(10),V(20),V(20),V(20),V(20),V(10), V(0), // 5
161 V(0), V(5), V(8), V(8), V(8), V(8), V(5), V(0), // 6
162 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 7
163 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0) // 8
166 // Bonus for unstoppable passed pawns:
167 const Value UnstoppablePawnValue = Value(0x500);
169 // Rooks and queens on the 7th rank:
170 const Value MidgameRookOn7thBonus = Value(50);
171 const Value EndgameRookOn7thBonus = Value(100);
172 const Value MidgameQueenOn7thBonus = Value(25);
173 const Value EndgameQueenOn7thBonus = Value(50);
175 // Rooks on open files:
176 const Value RookOpenFileBonus = Value(40);
177 const Value RookHalfOpenFileBonus = Value(20);
179 // Penalty for rooks trapped inside a friendly king which has lost the
181 const Value TrappedRookPenalty = Value(180);
183 // Penalty for a bishop on a7/h7 (a2/h2 for black) which is trapped by
185 const Value TrappedBishopA7H7Penalty = Value(300);
187 // Bitboard masks for detecting trapped bishops on a7/h7 (a2/h2 for black):
188 const Bitboard MaskA7H7[2] = {
189 ((1ULL << SQ_A7) | (1ULL << SQ_H7)),
190 ((1ULL << SQ_A2) | (1ULL << SQ_H2))
193 // Penalty for a bishop on a1/h1 (a8/h8 for black) which is trapped by
194 // a friendly pawn on b2/g2 (b7/g7 for black). This can obviously only
195 // happen in Chess960 games.
196 const Value TrappedBishopA1H1Penalty = Value(100);
198 // Bitboard masks for detecting trapped bishops on a1/h1 (a8/h8 for black):
199 const Bitboard MaskA1H1[2] = {
200 ((1ULL << SQ_A1) | (1ULL << SQ_H1)),
201 ((1ULL << SQ_A8) | (1ULL << SQ_H8))
204 /// King safety constants and variables. The king safety scores are taken
205 /// from the array SafetyTable[]. Various little "meta-bonuses" measuring
206 /// the strength of the attack are added up into an integer, which is used
207 /// as an index to SafetyTable[].
209 // Attack weights for each piece type.
210 const int QueenAttackWeight = 5;
211 const int RookAttackWeight = 3;
212 const int BishopAttackWeight = 2;
213 const int KnightAttackWeight = 2;
215 // Bonuses for safe checks for each piece type.
216 int QueenContactCheckBonus = 4;
217 int RookContactCheckBonus = 2;
218 int QueenCheckBonus = 2;
219 int RookCheckBonus = 1;
220 int BishopCheckBonus = 1;
221 int KnightCheckBonus = 1;
222 int DiscoveredCheckBonus = 3;
224 // Scan for queen contact mates?
225 const bool QueenContactMates = true;
227 // Bonus for having a mate threat.
228 int MateThreatBonus = 3;
230 // InitKingDanger[] contains bonuses based on the position of the defending
232 const int InitKingDanger[64] = {
233 2, 0, 2, 5, 5, 2, 0, 2,
234 2, 2, 4, 8, 8, 4, 2, 2,
235 7, 10, 12, 12, 12, 12, 10, 7,
236 15, 15, 15, 15, 15, 15, 15, 15,
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
243 // SafetyTable[] contains the actual king safety scores. It is initialized
245 Value SafetyTable[100];
247 // Pawn and material hash tables, indexed by the current thread id:
248 PawnInfoTable *PawnTable[8] = {0, 0, 0, 0, 0, 0, 0, 0};
249 MaterialInfoTable *MaterialTable[8] = {0, 0, 0, 0, 0, 0, 0, 0};
251 // Sizes of pawn and material hash tables:
252 const int PawnTableSize = 16384;
253 const int MaterialTableSize = 1024;
255 // Array which gives the number of nonzero bits in an 8-bit integer:
256 uint8_t BitCount8Bit[256];
258 // Function prototypes:
259 void evaluate_knight(const Position &p, Square s, Color us, EvalInfo &ei);
260 void evaluate_bishop(const Position &p, Square s, Color us, EvalInfo &ei);
261 void evaluate_rook(const Position &p, Square s, Color us, EvalInfo &ei);
262 void evaluate_queen(const Position &p, Square s, Color us, EvalInfo &ei);
263 void evaluate_king(const Position &p, Square s, Color us, EvalInfo &ei);
265 void evaluate_passed_pawns(const Position &pos, EvalInfo &ei);
266 void evaluate_trapped_bishop_a7h7(const Position &pos, Square s, Color us,
268 void evaluate_trapped_bishop_a1h1(const Position &pos, Square s, Color us,
271 inline Value apply_weight(Value v, int w);
272 Value scale_by_game_phase(Value mv, Value ev, Phase ph, ScaleFactor sf[]);
274 int count_1s_8bit(Bitboard b);
276 int compute_weight(int uciWeight, int internalWeight);
286 /// evaluate() is the main evaluation function. It always computes two
287 /// values, an endgame score and a middle game score, and interpolates
288 /// between them based on the remaining material.
290 Value evaluate(const Position &pos, EvalInfo &ei, int threadID) {
293 ScaleFactor factor[2] = {SCALE_FACTOR_NORMAL, SCALE_FACTOR_NORMAL};
296 memset(&ei, 0, sizeof(EvalInfo));
299 assert(threadID >= 0 && threadID < THREAD_MAX);
301 stm = pos.side_to_move();
303 // Initialize by reading the incrementally updated scores included in the
304 // position object (material + piece square tables):
305 ei.mgValue = pos.mg_value();
306 ei.egValue = pos.eg_value();
308 // Probe the material hash table:
309 ei.mi = MaterialTable[threadID]->get_material_info(pos);
310 ei.mgValue += ei.mi->mg_value();
311 ei.egValue += ei.mi->eg_value();
313 factor[WHITE] = ei.mi->scale_factor(pos, WHITE);
314 factor[BLACK] = ei.mi->scale_factor(pos, BLACK);
316 // If we have a specialized evaluation function for the current material
317 // configuration, call it and return:
318 if(ei.mi->specialized_eval_exists())
319 return ei.mi->evaluate(pos);
321 phase = pos.game_phase();
323 // Probe the pawn hash table:
324 ei.pi = PawnTable[threadID]->get_pawn_info(pos);
325 ei.mgValue += apply_weight(ei.pi->mg_value(), WeightPawnStructureMidgame);
326 ei.egValue += apply_weight(ei.pi->eg_value(), WeightPawnStructureEndgame);
328 // Initialize king attack bitboards and king attack zones for both sides:
329 ei.attackedBy[WHITE][KING] = pos.king_attacks(pos.king_square(WHITE));
330 ei.attackedBy[BLACK][KING] = pos.king_attacks(pos.king_square(BLACK));
331 ei.attackZone[WHITE] =
332 ei.attackedBy[BLACK][KING] | (ei.attackedBy[BLACK][KING] >> 8);
333 ei.attackZone[BLACK] =
334 ei.attackedBy[WHITE][KING] | (ei.attackedBy[WHITE][KING] << 8);
336 // Initialize pawn attack bitboards for both sides:
337 ei.attackedBy[WHITE][PAWN] =
338 ((pos.pawns(WHITE) << 9) & ~FileABB) | ((pos.pawns(WHITE) << 7) & ~FileHBB);
339 ei.attackCount[WHITE] +=
340 count_1s_max_15(ei.attackedBy[WHITE][PAWN] & ei.attackedBy[BLACK][KING])/2;
341 ei.attackedBy[BLACK][PAWN] =
342 ((pos.pawns(BLACK) >> 7) & ~FileABB) | ((pos.pawns(BLACK) >> 9) & ~FileHBB);
343 ei.attackCount[BLACK] +=
344 count_1s_max_15(ei.attackedBy[BLACK][PAWN] & ei.attackedBy[WHITE][KING])/2;
347 for(Color c = WHITE; c <= BLACK; c++) {
351 for(int i = 0; i < pos.knight_count(c); i++) {
352 s = pos.knight_list(c, i);
353 evaluate_knight(pos, s, c, ei);
357 for(int i = 0; i < pos.bishop_count(c); i++) {
358 s = pos.bishop_list(c, i);
359 evaluate_bishop(pos, s, c, ei);
363 for(int i = 0; i < pos.rook_count(c); i++) {
364 s = pos.rook_list(c, i);
365 evaluate_rook(pos, s, c, ei);
369 for(int i = 0; i < pos.queen_count(c); i++) {
370 s = pos.queen_list(c, i);
371 evaluate_queen(pos, s, c, ei);
374 // Some special patterns:
376 // Trapped bishops on a7/h7/a2/h2
377 b = pos.bishops(c) & MaskA7H7[c];
380 evaluate_trapped_bishop_a7h7(pos, s, c, ei);
383 // Trapped bishops on a1/h1/a8/h8 in Chess960:
385 b = pos.bishops(c) & MaskA1H1[c];
388 evaluate_trapped_bishop_a1h1(pos, s, c, ei);
392 ei.attackedBy[c][0] =
393 ei.attackedBy[c][PAWN] | ei.attackedBy[c][KNIGHT]
394 | ei.attackedBy[c][BISHOP] | ei.attackedBy[c][ROOK]
395 | ei.attackedBy[c][QUEEN] | ei.attackedBy[c][KING];
398 // Kings. Kings are evaluated after all other pieces for both sides,
399 // because we need complete attack information for all pieces when computing
400 // the king safety evaluation.
401 for(Color c = WHITE; c <= BLACK; c++) {
402 s = pos.king_square(c);
403 evaluate_king(pos, s, c, ei);
406 // Evaluate passed pawns. We evaluate passed pawns for both sides at once,
407 // because we need to know which side promotes first in positions where
408 // both sides have an unstoppable passed pawn.
409 if(ei.pi->passed_pawns())
410 evaluate_passed_pawns(pos, ei);
412 // Middle-game specific evaluation terms
413 if(phase > PHASE_ENDGAME) {
415 // Pawn storms in positions with opposite castling.
416 if(square_file(pos.king_square(WHITE)) >= FILE_E &&
417 square_file(pos.king_square(BLACK)) <= FILE_D)
419 ei.pi->queenside_storm_value(WHITE) -
420 ei.pi->kingside_storm_value(BLACK);
421 else if(square_file(pos.king_square(WHITE)) <= FILE_D &&
422 square_file(pos.king_square(BLACK)) >= FILE_E)
424 ei.pi->kingside_storm_value(WHITE) -
425 ei.pi->queenside_storm_value(BLACK);
429 ei.mgValue += apply_weight(ei.mgMobility, WeightMobilityMidgame);
430 ei.egValue += apply_weight(ei.egMobility, WeightMobilityEndgame);
432 // If we don't already have an unusual scale factor, check for opposite
433 // colored bishop endgames, and use a lower scale for those:
434 if(phase < PHASE_MIDGAME && pos.opposite_colored_bishops()
435 && ((factor[WHITE] == SCALE_FACTOR_NORMAL && ei.egValue > Value(0)) ||
436 (factor[BLACK] == SCALE_FACTOR_NORMAL && ei.egValue < Value(0)))) {
437 if(pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK) ==
438 2*BishopValueMidgame) {
439 // Only the two bishops
440 if(pos.pawn_count(WHITE) + pos.pawn_count(BLACK) == 1) {
441 // KBP vs KB with only a single pawn; almost certainly a draw.
442 if(factor[WHITE] == SCALE_FACTOR_NORMAL)
443 factor[WHITE] = ScaleFactor(8);
444 if(factor[BLACK] == SCALE_FACTOR_NORMAL)
445 factor[BLACK] = ScaleFactor(8);
448 // At least two pawns
449 if(factor[WHITE] == SCALE_FACTOR_NORMAL)
450 factor[WHITE] = ScaleFactor(32);
451 if(factor[BLACK] == SCALE_FACTOR_NORMAL)
452 factor[BLACK] = ScaleFactor(32);
456 // Endgame with opposite-colored bishops, but also other pieces.
457 // Still a bit drawish, but not as drawish as with only the two
459 if(factor[WHITE] == SCALE_FACTOR_NORMAL)
460 factor[WHITE] = ScaleFactor(50);
461 if(factor[BLACK] == SCALE_FACTOR_NORMAL)
462 factor[BLACK] = ScaleFactor(50);
466 // Interpolate between the middle game and the endgame score, and
468 Value value = scale_by_game_phase(ei.mgValue, ei.egValue, phase, factor);
470 if(ei.mateThreat[stm] != MOVE_NONE)
471 return 8 * QueenValueMidgame - Sign[stm] * value;
473 return Sign[stm] * value;
477 /// quick_evaluate() does a very approximate evaluation of the current position.
478 /// It currently considers only material and piece square table scores. Perhaps
479 /// we should add scores from the pawn and material hash tables?
481 Value quick_evaluate(const Position &pos) {
483 Value mgValue, egValue;
484 ScaleFactor factor[2] = {SCALE_FACTOR_NORMAL, SCALE_FACTOR_NORMAL};
489 stm = pos.side_to_move();
491 mgValue = pos.mg_value();
492 egValue = pos.eg_value();
493 phase = pos.game_phase();
495 Value value = scale_by_game_phase(mgValue, egValue, phase, factor);
497 return Sign[stm] * value;
501 /// init_eval() initializes various tables used by the evaluation function.
503 void init_eval(int threads) {
505 assert(threads <= THREAD_MAX);
507 for (int i = 0; i < THREAD_MAX; i++)
512 delete MaterialTable[i];
514 MaterialTable[i] = NULL;
518 PawnTable[i] = new PawnInfoTable(PawnTableSize);
519 if (!MaterialTable[i])
520 MaterialTable[i] = new MaterialInfoTable(MaterialTableSize);
523 for (Bitboard b = 0ULL; b < 256ULL; b++)
524 BitCount8Bit[b] = count_1s(b);
528 /// quit_eval() releases heap-allocated memory at program termination.
531 for(int i = 0; i < THREAD_MAX; i++) {
533 delete MaterialTable[i];
538 /// read_weights() reads evaluation weights from the corresponding UCI
541 void read_weights(Color sideToMove) {
542 WeightMobilityMidgame =
543 compute_weight(get_option_value_int("Mobility (Middle Game)"),
544 WeightMobilityMidgameInternal);
545 WeightMobilityEndgame =
546 compute_weight(get_option_value_int("Mobility (Endgame)"),
547 WeightMobilityEndgameInternal);
548 WeightPawnStructureMidgame =
549 compute_weight(get_option_value_int("Pawn Structure (Middle Game)"),
550 WeightPawnStructureMidgameInternal);
551 WeightPawnStructureEndgame =
552 compute_weight(get_option_value_int("Pawn Structure (Endgame)"),
553 WeightPawnStructureEndgameInternal);
554 WeightPassedPawnsMidgame =
555 compute_weight(get_option_value_int("Passed Pawns (Middle Game)"),
556 WeightPassedPawnsMidgameInternal);
557 WeightPassedPawnsEndgame =
558 compute_weight(get_option_value_int("Passed Pawns (Endgame)"),
559 WeightPassedPawnsEndgameInternal);
560 WeightKingSafety[sideToMove] =
561 compute_weight(get_option_value_int("Cowardice"), WeightKingSafetyInternal);
562 WeightKingSafety[opposite_color(sideToMove)] =
563 compute_weight(get_option_value_int("Aggressiveness"),
564 WeightKingSafetyInternal);
565 WeightKingSafety[opposite_color(sideToMove)] =
566 (get_option_value_int("Aggressiveness") * 0x100) / 100;
574 // evaluate_knight() assigns bonuses and penalties to a knight of a given
575 // color on a given square.
577 void evaluate_knight(const Position &p, Square s, Color us, EvalInfo &ei) {
579 Color them = opposite_color(us);
580 Bitboard b = p.knight_attacks(s);
581 ei.attackedBy[us][KNIGHT] |= b;
584 if(b & ei.attackZone[us]) {
585 ei.attackCount[us]++;
586 ei.attackWeight[us] += KnightAttackWeight;
587 Bitboard bb = (b & ei.attackedBy[them][KING]);
588 if(bb) ei.attacked[us] += count_1s_max_15(bb);
592 int mob = count_1s_max_15(b & ~p.pieces_of_color(us));
593 ei.mgMobility += Sign[us] * MidgameKnightMobilityBonus[mob];
594 ei.egMobility += Sign[us] * EndgameKnightMobilityBonus[mob];
597 if(p.square_is_weak(s, them)) {
600 // Initial bonus based on square:
601 v = bonus = KnightOutpostBonus[relative_square(us, s)];
603 // Increase bonus if supported by pawn, especially if the opponent has
604 // no minor piece which can exchange the outpost piece:
605 if(v && p.pawn_attacks(them, s) & p.pawns(us)) {
607 if(p.knight_count(them) == 0 &&
608 (SquaresByColorBB[square_color(s)] &
609 p.bishops(them)) == EmptyBoardBB) {
614 ei.mgValue += Sign[us] * bonus;
615 ei.egValue += Sign[us] * bonus;
620 // evaluate_bishop() assigns bonuses and penalties to a bishop of a given
621 // color on a given square.
623 void evaluate_bishop(const Position &p, Square s, Color us, EvalInfo &ei) {
625 Color them = opposite_color(us);
627 bishop_attacks_bb(s, p.occupied_squares() & ~p.queens(us));
629 ei.attackedBy[us][BISHOP] |= b;
632 if(b & ei.attackZone[us]) {
633 ei.attackCount[us]++;
634 ei.attackWeight[us] += BishopAttackWeight;
635 Bitboard bb = (b & ei.attackedBy[them][KING]);
636 if(bb) ei.attacked[us] += count_1s_max_15(bb);
640 int mob = count_1s_max_15(b & ~p.pieces_of_color(us));
641 ei.mgMobility += Sign[us] * MidgameBishopMobilityBonus[mob];
642 ei.egMobility += Sign[us] * EndgameBishopMobilityBonus[mob];
645 if(p.square_is_weak(s, them)) {
648 // Initial bonus based on square:
649 v = bonus = BishopOutpostBonus[relative_square(us, s)];
651 // Increase bonus if supported by pawn, especially if the opponent has
652 // no minor piece which can exchange the outpost piece:
653 if(v && p.pawn_attacks(them, s) & p.pawns(us)) {
655 if(p.knight_count(them) == 0 &&
656 (SquaresByColorBB[square_color(s)] &
657 p.bishops(them)) == EmptyBoardBB) {
662 ei.mgValue += Sign[us] * bonus;
663 ei.egValue += Sign[us] * bonus;
668 // evaluate_rook() assigns bonuses and penalties to a rook of a given
669 // color on a given square.
671 void evaluate_rook(const Position &p, Square s, Color us, EvalInfo &ei) {
673 Color them = opposite_color(us);
675 // Open and half-open files:
676 File f = square_file(s);
677 if(ei.pi->file_is_half_open(us, f)) {
678 if(ei.pi->file_is_half_open(them, f)) {
679 ei.mgValue += Sign[us] * RookOpenFileBonus;
680 ei.egValue += Sign[us] * RookOpenFileBonus;
683 ei.mgValue += Sign[us] * RookHalfOpenFileBonus;
684 ei.egValue += Sign[us] * RookHalfOpenFileBonus;
689 if(pawn_rank(us, s) == RANK_7 &&
690 pawn_rank(us, p.king_square(them)) == RANK_8) {
691 ei.mgValue += Sign[us] * MidgameRookOn7thBonus;
692 ei.egValue += Sign[us] * EndgameRookOn7thBonus;
695 //Bitboard b = p.rook_attacks(s);
697 rook_attacks_bb(s, p.occupied_squares() & ~p.rooks_and_queens(us));
698 ei.attackedBy[us][ROOK] |= b;
701 if(b & ei.attackZone[us]) {
702 ei.attackCount[us]++;
703 ei.attackWeight[us] += RookAttackWeight;
704 Bitboard bb = (b & ei.attackedBy[them][KING]);
705 if(bb) ei.attacked[us] += count_1s_max_15(bb);
709 int mob = count_1s_max_15(b & ~p.pieces_of_color(us));
710 ei.mgMobility += Sign[us] * MidgameRookMobilityBonus[mob];
711 ei.egMobility += Sign[us] * EndgameRookMobilityBonus[mob];
713 // Penalize rooks which are trapped inside a king which has lost the
715 if(mob <= 6 && !ei.pi->file_is_half_open(us, f)) {
716 Square ksq = p.king_square(us);
717 if(square_file(ksq) >= FILE_E && square_file(s) > square_file(ksq) &&
718 (pawn_rank(us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s))) {
719 // Is there a half-open file between the king and the edge of the
721 if(!(ei.pi->has_open_file_to_right(us, square_file(ksq)))) {
722 ei.mgValue -= p.can_castle(us)?
723 Sign[us] * ((TrappedRookPenalty - mob * 16) / 2) :
724 Sign[us] * (TrappedRookPenalty - mob * 16);
727 else if(square_file(ksq) <= FILE_D && square_file(s) < square_file(ksq)
728 && (pawn_rank(us, ksq) == RANK_1 ||
729 square_rank(ksq) == square_rank(s))) {
730 // Is there a half-open file between the king and the edge of the
732 if(!(ei.pi->has_open_file_to_left(us, square_file(ksq)))) {
733 ei.mgValue -= p.can_castle(us)?
734 Sign[us] * ((TrappedRookPenalty - mob * 16) / 2) :
735 Sign[us] * (TrappedRookPenalty - mob * 16);
742 // evaluate_queen() assigns bonuses and penalties to a queen of a given
743 // color on a given square.
745 void evaluate_queen(const Position &p, Square s, Color us, EvalInfo &ei) {
747 Color them = opposite_color(us);
749 // Queen on 7th rank:
750 if(pawn_rank(us, s) == RANK_7 &&
751 pawn_rank(us, p.king_square(them)) == RANK_8) {
752 ei.mgValue += Sign[us] * MidgameQueenOn7thBonus;
753 ei.egValue += Sign[us] * EndgameQueenOn7thBonus;
756 Bitboard b = p.queen_attacks(s);
757 ei.attackedBy[us][QUEEN] |= b;
760 if(b & ei.attackZone[us]) {
761 ei.attackCount[us]++;
762 ei.attackWeight[us] += QueenAttackWeight;
763 Bitboard bb = (b & ei.attackedBy[them][KING]);
764 if(bb) ei.attacked[us] += count_1s_max_15(bb);
768 int mob = count_1s(b & ~p.pieces_of_color(us));
769 ei.mgMobility += Sign[us] * MidgameQueenMobilityBonus[mob];
770 ei.egMobility += Sign[us] * EndgameQueenMobilityBonus[mob];
774 // evaluate_king() assigns bonuses and penalties to a king of a given
775 // color on a given square.
777 void evaluate_king(const Position &p, Square s, Color us, EvalInfo &ei) {
779 int shelter = 0, sign = Sign[us];
782 if(pawn_rank(us, s) <= RANK_4) {
783 Bitboard pawns = p.pawns(us) & this_and_neighboring_files_bb(s);
784 Rank r = square_rank(s);
785 for(int i = 0; i < 3; i++)
786 shelter += count_1s_8bit(pawns >> ((r+(i+1)*sign) * 8)) * (64>>i);
787 ei.mgValue += sign * Value(shelter);
790 // King safety. This is quite complicated, and is almost certainly far
791 // from optimally tuned.
792 Color them = opposite_color(us);
793 if(p.queen_count(them) >= 1 && ei.attackCount[them] >= 2
794 && p.non_pawn_material(them) >= QueenValueMidgame + RookValueMidgame
795 && ei.attacked[them]) {
797 // Is it the attackers turn to move?
798 bool sente = (them == p.side_to_move());
800 // Find the attacked squares around the king which has no defenders
801 // apart from the king itself:
802 Bitboard undefended =
803 ei.attacked_by(them) & ~ei.attacked_by(us, PAWN)
804 & ~ei.attacked_by(us, KNIGHT) & ~ei.attacked_by(us, BISHOP)
805 & ~ei.attacked_by(us, ROOK) & ~ei.attacked_by(us, QUEEN)
806 & ei.attacked_by(us, KING);
807 Bitboard occ = p.occupied_squares(), b, b2;
809 // Initialize the 'attackUnits' variable, which is used later on as an
810 // index to the SafetyTable[] array. The initial is based on the number
811 // and types of the attacking pieces, the number of attacked and
812 // undefended squares around the king, the square of the king, and the
813 // quality of the pawn shelter.
815 Min((ei.attackCount[them] * ei.attackWeight[them]) / 2, 25)
816 + (ei.attacked[them] + count_1s_max_15(undefended)) * 3
817 + InitKingDanger[relative_square(us, s)] - shelter / 32;
819 // Analyse safe queen contact checks:
820 b = undefended & ei.attacked_by(them, QUEEN) & ~p.pieces_of_color(them);
822 Bitboard attackedByOthers =
823 ei.attacked_by(them, PAWN) | ei.attacked_by(them, KNIGHT)
824 | ei.attacked_by(them, BISHOP) | ei.attacked_by(them, ROOK);
825 b &= attackedByOthers;
827 // The bitboard b now contains the squares available for safe queen
829 int count = count_1s_max_15(b);
830 attackUnits += QueenContactCheckBonus * count * (sente? 2 : 1);
832 // Is there a mate threat?
833 if(QueenContactMates && !p.is_check()) {
834 Bitboard escapeSquares =
835 p.king_attacks(s) & ~p.pieces_of_color(us) & ~attackedByOthers;
837 Square from, to = pop_1st_bit(&b);
839 & ~queen_attacks_bb(to, occ & clear_mask_bb(s)))) {
840 // We have a mate, unless the queen is pinned or there
841 // is an X-ray attack through the queen.
842 for(int i = 0; i < p.queen_count(them); i++) {
843 from = p.queen_list(them, i);
844 if(bit_is_set(p.queen_attacks(from), to)
845 && !bit_is_set(p.pinned_pieces(them), from)
846 && !(rook_attacks_bb(to, occ & clear_mask_bb(from))
847 & p.rooks_and_queens(us))
848 && !(rook_attacks_bb(to, occ & clear_mask_bb(from))
849 & p.rooks_and_queens(us)))
850 ei.mateThreat[them] = make_move(from, to);
858 // Analyse safe rook contact checks:
859 if(RookContactCheckBonus) {
860 b = undefended & ei.attacked_by(them, ROOK) & ~p.pieces_of_color(them);
862 Bitboard attackedByOthers =
863 ei.attacked_by(them, PAWN) | ei.attacked_by(them, KNIGHT)
864 | ei.attacked_by(them, BISHOP) | ei.attacked_by(them, QUEEN);
865 b &= attackedByOthers;
867 int count = count_1s_max_15(b);
868 attackUnits += (RookContactCheckBonus * count * (sente? 2 : 1));
873 // Analyse safe distance checks:
874 if(QueenCheckBonus > 0 || RookCheckBonus > 0) {
875 b = p.rook_attacks(s) & ~p.pieces_of_color(them) & ~ei.attacked_by(us);
878 b2 = b & ei.attacked_by(them, QUEEN);
879 if(b2) attackUnits += QueenCheckBonus * count_1s_max_15(b2);
882 b2 = b & ei.attacked_by(them, ROOK);
883 if(b2) attackUnits += RookCheckBonus * count_1s_max_15(b2);
885 if(QueenCheckBonus > 0 || BishopCheckBonus > 0) {
886 b = p.bishop_attacks(s) & ~p.pieces_of_color(them) & ~ei.attacked_by(us);
888 b2 = b & ei.attacked_by(them, QUEEN);
889 if(b2) attackUnits += QueenCheckBonus * count_1s_max_15(b2);
892 b2 = b & ei.attacked_by(them, BISHOP);
893 if(b2) attackUnits += BishopCheckBonus * count_1s_max_15(b2);
895 if(KnightCheckBonus > 0) {
896 b = p.knight_attacks(s) & ~p.pieces_of_color(them) & ~ei.attacked_by(us);
898 b2 = b & ei.attacked_by(them, KNIGHT);
899 if(b2) attackUnits += KnightCheckBonus * count_1s_max_15(b2);
902 // Analyse discovered checks (only for non-pawns right now, consider
903 // adding pawns later).
904 if(DiscoveredCheckBonus) {
905 b = p.discovered_check_candidates(them) & ~p.pawns();
908 DiscoveredCheckBonus * count_1s_max_15(b) * (sente? 2 : 1);
911 // Has a mate threat been found? We don't do anything here if the
912 // side with the mating move is the side to move, because in that
913 // case the mating side will get a huge bonus at the end of the main
914 // evaluation function instead.
915 if(ei.mateThreat[them] != MOVE_NONE)
916 attackUnits += MateThreatBonus;
918 // Ensure that attackUnits is between 0 and 99, in order to avoid array
919 // out of bounds errors:
920 if(attackUnits < 0) attackUnits = 0;
921 if(attackUnits >= 100) attackUnits = 99;
923 // Finally, extract the king safety score from the SafetyTable[] array.
924 // Add the score to the evaluation, and also to ei.futilityMargin. The
925 // reason for adding the king safety score to the futility margin is
926 // that the king safety scores can sometimes be very big, and that
927 // capturing a single attacking piece can therefore result in a score
928 // change far bigger than the value of the captured piece.
929 Value v = apply_weight(SafetyTable[attackUnits], WeightKingSafety[us]);
930 ei.mgValue -= sign * v;
931 if(us == p.side_to_move())
932 ei.futilityMargin += v;
937 // evaluate_passed_pawns() evaluates the passed pawns for both sides.
939 void evaluate_passed_pawns(const Position &pos, EvalInfo &ei) {
940 bool hasUnstoppable[2] = {false, false};
941 int movesToGo[2] = {100, 100};
943 for(Color us = WHITE; us <= BLACK; us++) {
944 Color them = opposite_color(us);
945 Square ourKingSq = pos.king_square(us);
946 Square theirKingSq = pos.king_square(them);
947 Bitboard b = ei.pi->passed_pawns() & pos.pawns(us), b2, b3, b4;
950 Square s = pop_1st_bit(&b);
951 assert(pos.piece_on(s) == pawn_of_color(us));
952 assert(pos.pawn_is_passed(us, s));
954 int r = int(pawn_rank(us, s) - RANK_2);
955 int tr = Max(0, r * (r-1));
956 Square blockSq = s + pawn_push(us);
958 // Base bonus based on rank:
959 Value mbonus = Value(20 * tr);
960 Value ebonus = Value(10 + r * r * 10);
962 // Adjust bonus based on king proximity:
963 ebonus -= Value(square_distance(ourKingSq, blockSq) * 3 * tr);
965 Value(square_distance(ourKingSq, blockSq + pawn_push(us)) * 1 * tr);
966 ebonus += Value(square_distance(theirKingSq, blockSq) * 6 * tr);
968 // If the pawn is free to advance, increase bonus:
969 if(pos.square_is_empty(blockSq)) {
971 b2 = squares_in_front_of(us, s);
972 b3 = b2 & ei.attacked_by(them);
973 b4 = b2 & ei.attacked_by(us);
974 if((b2 & pos.pieces_of_color(them)) == EmptyBoardBB) {
975 // There are no enemy pieces in the pawn's path! Are any of the
976 // squares in the pawn's path attacked by the enemy?
977 if(b3 == EmptyBoardBB)
978 // No enemy attacks, huge bonus!
979 ebonus += Value(tr * ((b2 == b4)? 17 : 15));
981 // OK, there are enemy attacks. Are those squares which are
982 // attacked by the enemy also attacked by us? If yes, big bonus
983 // (but smaller than when there are no enemy attacks), if no,
984 // somewhat smaller bonus.
985 ebonus += Value(tr * (((b3 & b4) == b3)? 13 : 8));
988 // There are some enemy pieces in the pawn's path. While this is
989 // sad, we still assign a moderate bonus if all squares in the path
990 // which are either occupied by or attacked by enemy pieces are
991 // also attacked by us.
992 if(((b3 | (b2 & pos.pieces_of_color(them))) & ~b4) == EmptyBoardBB)
993 ebonus += Value(tr * 6);
995 // At last, add a small bonus when there are no *friendly* pieces
996 // in the pawn's path:
997 if((b2 & pos.pieces_of_color(us)) == EmptyBoardBB)
1001 // If the pawn is supported by a friendly pawn, increase bonus.
1002 b2 = pos.pawns(us) & neighboring_files_bb(s);
1004 ebonus += Value(r * 20);
1005 else if(pos.pawn_attacks(them, s) & b2)
1006 ebonus += Value(r * 12);
1008 // If the other side has only a king, check whether the pawn is
1010 if(pos.non_pawn_material(them) == Value(0)) {
1014 qsq = relative_square(us, make_square(square_file(s), RANK_8));
1015 d = square_distance(s, qsq) - square_distance(theirKingSq, qsq)
1016 + ((us == pos.side_to_move())? 0 : 1);
1019 int mtg = RANK_8 - pawn_rank(us, s);
1021 count_1s_max_15(squares_in_front_of(us,s)&pos.occupied_squares());
1022 mtg += blockerCount;
1025 hasUnstoppable[us] = true;
1026 movesToGo[us] = Min(movesToGo[us], mtg);
1030 // Rook pawns are a special case: They are sometimes worse, and
1031 // sometimes better than other passed pawns. It is difficult to find
1032 // good rules for determining whether they are good or bad. For now,
1033 // we try the following: Increase the value for rook pawns if the
1034 // other side has no pieces apart from a knight, and decrease the
1035 // value if the other side has a rook or queen.
1036 if(square_file(s) == FILE_A || square_file(s) == FILE_H) {
1037 if(pos.non_pawn_material(them) == KnightValueMidgame
1038 && pos.knight_count(them) == 1)
1039 ebonus += ebonus / 4;
1040 else if(pos.rooks_and_queens(them))
1041 ebonus -= ebonus / 4;
1044 // Add the scores for this pawn to the middle game and endgame eval.
1045 ei.mgValue += apply_weight(Sign[us] * mbonus, WeightPassedPawnsMidgame);
1046 ei.egValue += apply_weight(Sign[us] * ebonus, WeightPassedPawnsEndgame);
1050 // Does either side have an unstoppable passed pawn?
1051 if(hasUnstoppable[WHITE] && !hasUnstoppable[BLACK])
1052 ei.egValue += UnstoppablePawnValue - Value(0x40 * movesToGo[WHITE]);
1053 else if(hasUnstoppable[BLACK] && !hasUnstoppable[WHITE])
1054 ei.egValue -= UnstoppablePawnValue - Value(0x40 * movesToGo[BLACK]);
1055 else if(hasUnstoppable[BLACK] && hasUnstoppable[WHITE]) {
1056 // Both sides have unstoppable pawns! Try to find out who queens
1057 // first. We begin by transforming 'movesToGo' to the number of
1058 // plies until the pawn queens for both sides:
1059 movesToGo[WHITE] *= 2;
1060 movesToGo[BLACK] *= 2;
1061 movesToGo[pos.side_to_move()]--;
1063 // If one side queens at least three plies before the other, that
1065 if(movesToGo[WHITE] <= movesToGo[BLACK] - 3)
1066 ei.egValue += UnstoppablePawnValue - Value(0x40 * (movesToGo[WHITE]/2));
1067 else if(movesToGo[BLACK] <= movesToGo[WHITE] - 3)
1068 ei.egValue -= UnstoppablePawnValue - Value(0x40 * (movesToGo[BLACK]/2));
1070 // We could also add some rules about the situation when one side
1071 // queens exactly one ply before the other: Does the first queen
1072 // check the opponent's king, or attack the opponent's queening square?
1073 // This is slightly tricky to get right, because it is possible that
1074 // the opponent's king has moved somewhere before the first pawn queens.
1079 // evaluate_trapped_bishop_a7h7() determines whether a bishop on a7/h7
1080 // (a2/h2 for black) is trapped by enemy pawns, and assigns a penalty
1083 void evaluate_trapped_bishop_a7h7(const Position &pos, Square s, Color us,
1085 Piece pawn = pawn_of_color(opposite_color(us));
1088 assert(square_is_ok(s));
1089 assert(pos.piece_on(s) == bishop_of_color(us));
1091 if(square_file(s) == FILE_A) {
1092 b6 = relative_square(us, SQ_B6);
1093 b8 = relative_square(us, SQ_B8);
1096 b6 = relative_square(us, SQ_G6);
1097 b8 = relative_square(us, SQ_G8);
1100 if(pos.piece_on(b6) == pawn && pos.see(s, b6) < 0 && pos.see(s, b8) < 0) {
1101 ei.mgValue -= Sign[us] * TrappedBishopA7H7Penalty;
1102 ei.egValue -= Sign[us] * TrappedBishopA7H7Penalty;
1108 // evaluate_trapped_bishop_a1h1() determines whether a bishop on a1/h1
1109 // (a8/h8 for black) is trapped by a friendly pawn on b2/g2 (b7/g7 for
1110 // black), and assigns a penalty if it is. This pattern can obviously
1111 // only occur in Chess960 games.
1113 void evaluate_trapped_bishop_a1h1(const Position &pos, Square s, Color us,
1115 Piece pawn = pawn_of_color(us);
1119 assert(square_is_ok(s));
1120 assert(pos.piece_on(s) == bishop_of_color(us));
1122 if(square_file(s) == FILE_A) {
1123 b2 = relative_square(us, SQ_B2);
1124 b3 = relative_square(us, SQ_B3);
1125 c3 = relative_square(us, SQ_C3);
1128 b2 = relative_square(us, SQ_G2);
1129 b3 = relative_square(us, SQ_G3);
1130 c3 = relative_square(us, SQ_F3);
1133 if(pos.piece_on(b2) == pawn) {
1136 if(!pos.square_is_empty(b3))
1137 penalty = 2*TrappedBishopA1H1Penalty;
1138 else if(pos.piece_on(c3) == pawn)
1139 penalty = TrappedBishopA1H1Penalty;
1141 penalty = TrappedBishopA1H1Penalty / 2;
1143 ei.mgValue -= Sign[us] * penalty;
1144 ei.egValue -= Sign[us] * penalty;
1150 // apply_weight applies an evaluation weight to a value.
1152 inline Value apply_weight(Value v, int w) {
1153 return (v*w) / 0x100;
1157 // scale_by_game_phase interpolates between a middle game and an endgame
1158 // score, based on game phase. It also scales the return value by a
1159 // ScaleFactor array.
1161 Value scale_by_game_phase(Value mv, Value ev, Phase ph, ScaleFactor sf[]) {
1162 assert(mv > -VALUE_INFINITE && mv < VALUE_INFINITE);
1163 assert(ev > -VALUE_INFINITE && ev < VALUE_INFINITE);
1164 assert(ph >= PHASE_ENDGAME && ph <= PHASE_MIDGAME);
1167 ev = apply_scale_factor(ev, sf[WHITE]);
1169 ev = apply_scale_factor(ev, sf[BLACK]);
1171 // Superlinear interpolator
1172 int sli_ph = int(ph);
1173 sli_ph -= (64 - sli_ph) / 4;
1174 sli_ph = Min(PHASE_MIDGAME, Max(PHASE_ENDGAME, sli_ph)); // ceiling
1176 Value result = Value(int((mv * sli_ph + ev * (128 - sli_ph)) / 128));
1177 return Value(int(result) & ~(GrainSize - 1));
1181 // count_1s_8bit() counts the number of nonzero bits in the 8 least
1182 // significant bits of a Bitboard. This function is used by the king
1183 // shield evaluation.
1185 int count_1s_8bit(Bitboard b) {
1186 return int(BitCount8Bit[b & 0xFF]);
1190 // compute_weight() computes the value of an evaluation weight, by combining
1191 // an UCI-configurable weight with an internal weight.
1193 int compute_weight(int uciWeight, int internalWeight) {
1194 uciWeight = (uciWeight * 0x100) / 100;
1195 return (uciWeight * internalWeight) / 0x100;
1199 // init_safety() initizes the king safety evaluation, based on UCI
1200 // parameters. It is called from read_weights().
1202 void init_safety() {
1204 int maxSlope, peak, i, j;
1206 QueenContactCheckBonus = get_option_value_int("Queen Contact Check Bonus");
1207 RookContactCheckBonus = get_option_value_int("Rook Contact Check Bonus");
1208 QueenCheckBonus = get_option_value_int("Queen Check Bonus");
1209 RookCheckBonus = get_option_value_int("Rook Check Bonus");
1210 BishopCheckBonus = get_option_value_int("Bishop Check Bonus");
1211 KnightCheckBonus = get_option_value_int("Knight Check Bonus");
1212 DiscoveredCheckBonus = get_option_value_int("Discovered Check Bonus");
1213 MateThreatBonus = get_option_value_int("Mate Threat Bonus");
1215 a = get_option_value_int("King Safety Coefficient") / 100.0;
1216 b = get_option_value_int("King Safety X Intercept") * 1.0;
1217 maxSlope = get_option_value_int("King Safety Max Slope");
1218 peak = (get_option_value_int("King Safety Max Value") * 256) / 100;
1220 for(i = 0; i < 100; i++) {
1221 if(i < b) SafetyTable[i] = Value(0);
1222 else if(get_option_value_string("King Safety Curve") == "Quadratic")
1223 SafetyTable[i] = Value((int)(a * (i - b) * (i - b)));
1224 else if(get_option_value_string("King Safety Curve") == "Linear")
1225 SafetyTable[i] = Value((int)(100 * a * (i - b)));
1228 for(i = 0; i < 100; i++)
1229 if(SafetyTable[i+1] - SafetyTable[i] > maxSlope) {
1230 for(j = i + 1; j < 100; j++)
1231 SafetyTable[j] = SafetyTable[j-1] + Value(maxSlope);
1233 for(i = 0; i < 100; i++)
1234 if(SafetyTable[i] > Value(peak))
1235 SafetyTable[i] = Value(peak);