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_common() computes terms common to all pieces attack
576 int evaluate_common(const Position&p, const Bitboard& b, Color us, EvalInfo& ei,
577 int AttackWeight, const Value* mgBonus, const Value* egBonus,
578 Square s = SQ_NONE, const Value* OutpostBonus = NULL) {
580 Color them = opposite_color(us);
583 if (b & ei.attackZone[us])
585 ei.attackCount[us]++;
586 ei.attackWeight[us] += AttackWeight;
587 Bitboard bb = (b & ei.attackedBy[them][KING]);
589 ei.attacked[us] += count_1s_max_15(bb);
593 int mob = count_1s_max_15(b & ~p.pieces_of_color(us));
594 ei.mgMobility += Sign[us] * mgBonus[mob];
595 ei.egMobility += Sign[us] * egBonus[mob];
597 // Bishop and Knight outposts
598 if (!OutpostBonus || !p.square_is_weak(s, them))
601 // Initial bonus based on square
603 v = bonus = OutpostBonus[relative_square(us, s)];
605 // Increase bonus if supported by pawn, especially if the opponent has
606 // no minor piece which can exchange the outpost piece
607 if (v && (p.pawn_attacks(them, s) & p.pawns(us)))
610 if ( p.knight_count(them) == 0
611 && (SquaresByColorBB[square_color(s)] & p.bishops(them)) == EmptyBoardBB)
614 ei.mgValue += Sign[us] * bonus;
615 ei.egValue += Sign[us] * bonus;
620 // evaluate_knight() assigns bonuses and penalties to a knight of a given
621 // color on a given square.
623 void evaluate_knight(const Position &p, Square s, Color us, EvalInfo &ei) {
625 Bitboard b = p.knight_attacks(s);
626 ei.attackedBy[us][KNIGHT] |= b;
628 // King attack, mobility and outposts
629 evaluate_common(p, b, us, ei, KnightAttackWeight, MidgameKnightMobilityBonus,
630 EndgameKnightMobilityBonus, s, KnightOutpostBonus);
634 // evaluate_bishop() assigns bonuses and penalties to a bishop of a given
635 // color on a given square.
637 void evaluate_bishop(const Position &p, Square s, Color us, EvalInfo &ei) {
639 Bitboard b = bishop_attacks_bb(s, p.occupied_squares() & ~p.queens(us));
640 ei.attackedBy[us][BISHOP] |= b;
642 // King attack, mobility and outposts
643 evaluate_common(p, b, us, ei, BishopAttackWeight, MidgameBishopMobilityBonus,
644 EndgameBishopMobilityBonus, s, BishopOutpostBonus);
648 // evaluate_rook() assigns bonuses and penalties to a rook of a given
649 // color on a given square.
651 void evaluate_rook(const Position &p, Square s, Color us, EvalInfo &ei) {
653 Color them = opposite_color(us);
655 // Open and half-open files:
656 File f = square_file(s);
657 if(ei.pi->file_is_half_open(us, f)) {
658 if(ei.pi->file_is_half_open(them, f)) {
659 ei.mgValue += Sign[us] * RookOpenFileBonus;
660 ei.egValue += Sign[us] * RookOpenFileBonus;
663 ei.mgValue += Sign[us] * RookHalfOpenFileBonus;
664 ei.egValue += Sign[us] * RookHalfOpenFileBonus;
669 if(pawn_rank(us, s) == RANK_7 &&
670 pawn_rank(us, p.king_square(them)) == RANK_8) {
671 ei.mgValue += Sign[us] * MidgameRookOn7thBonus;
672 ei.egValue += Sign[us] * EndgameRookOn7thBonus;
675 //Bitboard b = p.rook_attacks(s);
676 Bitboard b = rook_attacks_bb(s, p.occupied_squares() & ~p.rooks_and_queens(us));
677 ei.attackedBy[us][ROOK] |= b;
679 // King attack and mobility
680 int mob = evaluate_common(p, b, us, ei, RookAttackWeight, MidgameRookMobilityBonus,
681 EndgameRookMobilityBonus);
683 // Penalize rooks which are trapped inside a king which has lost the
685 if(mob <= 6 && !ei.pi->file_is_half_open(us, f)) {
686 Square ksq = p.king_square(us);
687 if(square_file(ksq) >= FILE_E && square_file(s) > square_file(ksq) &&
688 (pawn_rank(us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s))) {
689 // Is there a half-open file between the king and the edge of the
691 if(!(ei.pi->has_open_file_to_right(us, square_file(ksq)))) {
692 ei.mgValue -= p.can_castle(us)?
693 Sign[us] * ((TrappedRookPenalty - mob * 16) / 2) :
694 Sign[us] * (TrappedRookPenalty - mob * 16);
697 else if(square_file(ksq) <= FILE_D && square_file(s) < square_file(ksq)
698 && (pawn_rank(us, ksq) == RANK_1 ||
699 square_rank(ksq) == square_rank(s))) {
700 // Is there a half-open file between the king and the edge of the
702 if(!(ei.pi->has_open_file_to_left(us, square_file(ksq)))) {
703 ei.mgValue -= p.can_castle(us)?
704 Sign[us] * ((TrappedRookPenalty - mob * 16) / 2) :
705 Sign[us] * (TrappedRookPenalty - mob * 16);
712 // evaluate_queen() assigns bonuses and penalties to a queen of a given
713 // color on a given square.
715 void evaluate_queen(const Position &p, Square s, Color us, EvalInfo &ei) {
717 Color them = opposite_color(us);
719 // Queen on 7th rank:
720 if(pawn_rank(us, s) == RANK_7 &&
721 pawn_rank(us, p.king_square(them)) == RANK_8) {
722 ei.mgValue += Sign[us] * MidgameQueenOn7thBonus;
723 ei.egValue += Sign[us] * EndgameQueenOn7thBonus;
726 Bitboard b = p.queen_attacks(s);
727 ei.attackedBy[us][QUEEN] |= b;
729 // King attack and mobility
730 evaluate_common(p, b, us, ei, QueenAttackWeight, MidgameQueenMobilityBonus,
731 EndgameQueenMobilityBonus);
735 // evaluate_king() assigns bonuses and penalties to a king of a given
736 // color on a given square.
738 void evaluate_king(const Position &p, Square s, Color us, EvalInfo &ei) {
740 int shelter = 0, sign = Sign[us];
743 if(pawn_rank(us, s) <= RANK_4) {
744 Bitboard pawns = p.pawns(us) & this_and_neighboring_files_bb(s);
745 Rank r = square_rank(s);
746 for(int i = 0; i < 3; i++)
747 shelter += count_1s_8bit(pawns >> ((r+(i+1)*sign) * 8)) * (64>>i);
748 ei.mgValue += sign * Value(shelter);
751 // King safety. This is quite complicated, and is almost certainly far
752 // from optimally tuned.
753 Color them = opposite_color(us);
754 if(p.queen_count(them) >= 1 && ei.attackCount[them] >= 2
755 && p.non_pawn_material(them) >= QueenValueMidgame + RookValueMidgame
756 && ei.attacked[them]) {
758 // Is it the attackers turn to move?
759 bool sente = (them == p.side_to_move());
761 // Find the attacked squares around the king which has no defenders
762 // apart from the king itself:
763 Bitboard undefended =
764 ei.attacked_by(them) & ~ei.attacked_by(us, PAWN)
765 & ~ei.attacked_by(us, KNIGHT) & ~ei.attacked_by(us, BISHOP)
766 & ~ei.attacked_by(us, ROOK) & ~ei.attacked_by(us, QUEEN)
767 & ei.attacked_by(us, KING);
768 Bitboard occ = p.occupied_squares(), b, b2;
770 // Initialize the 'attackUnits' variable, which is used later on as an
771 // index to the SafetyTable[] array. The initial is based on the number
772 // and types of the attacking pieces, the number of attacked and
773 // undefended squares around the king, the square of the king, and the
774 // quality of the pawn shelter.
776 Min((ei.attackCount[them] * ei.attackWeight[them]) / 2, 25)
777 + (ei.attacked[them] + count_1s_max_15(undefended)) * 3
778 + InitKingDanger[relative_square(us, s)] - shelter / 32;
780 // Analyse safe queen contact checks:
781 b = undefended & ei.attacked_by(them, QUEEN) & ~p.pieces_of_color(them);
783 Bitboard attackedByOthers =
784 ei.attacked_by(them, PAWN) | ei.attacked_by(them, KNIGHT)
785 | ei.attacked_by(them, BISHOP) | ei.attacked_by(them, ROOK);
786 b &= attackedByOthers;
788 // The bitboard b now contains the squares available for safe queen
790 int count = count_1s_max_15(b);
791 attackUnits += QueenContactCheckBonus * count * (sente? 2 : 1);
793 // Is there a mate threat?
794 if(QueenContactMates && !p.is_check()) {
795 Bitboard escapeSquares =
796 p.king_attacks(s) & ~p.pieces_of_color(us) & ~attackedByOthers;
798 Square from, to = pop_1st_bit(&b);
800 & ~queen_attacks_bb(to, occ & clear_mask_bb(s)))) {
801 // We have a mate, unless the queen is pinned or there
802 // is an X-ray attack through the queen.
803 for(int i = 0; i < p.queen_count(them); i++) {
804 from = p.queen_list(them, i);
805 if(bit_is_set(p.queen_attacks(from), to)
806 && !bit_is_set(p.pinned_pieces(them), from)
807 && !(rook_attacks_bb(to, occ & clear_mask_bb(from))
808 & p.rooks_and_queens(us))
809 && !(rook_attacks_bb(to, occ & clear_mask_bb(from))
810 & p.rooks_and_queens(us)))
811 ei.mateThreat[them] = make_move(from, to);
819 // Analyse safe rook contact checks:
820 if(RookContactCheckBonus) {
821 b = undefended & ei.attacked_by(them, ROOK) & ~p.pieces_of_color(them);
823 Bitboard attackedByOthers =
824 ei.attacked_by(them, PAWN) | ei.attacked_by(them, KNIGHT)
825 | ei.attacked_by(them, BISHOP) | ei.attacked_by(them, QUEEN);
826 b &= attackedByOthers;
828 int count = count_1s_max_15(b);
829 attackUnits += (RookContactCheckBonus * count * (sente? 2 : 1));
834 // Analyse safe distance checks:
835 if(QueenCheckBonus > 0 || RookCheckBonus > 0) {
836 b = p.rook_attacks(s) & ~p.pieces_of_color(them) & ~ei.attacked_by(us);
839 b2 = b & ei.attacked_by(them, QUEEN);
840 if(b2) attackUnits += QueenCheckBonus * count_1s_max_15(b2);
843 b2 = b & ei.attacked_by(them, ROOK);
844 if(b2) attackUnits += RookCheckBonus * count_1s_max_15(b2);
846 if(QueenCheckBonus > 0 || BishopCheckBonus > 0) {
847 b = p.bishop_attacks(s) & ~p.pieces_of_color(them) & ~ei.attacked_by(us);
849 b2 = b & ei.attacked_by(them, QUEEN);
850 if(b2) attackUnits += QueenCheckBonus * count_1s_max_15(b2);
853 b2 = b & ei.attacked_by(them, BISHOP);
854 if(b2) attackUnits += BishopCheckBonus * count_1s_max_15(b2);
856 if(KnightCheckBonus > 0) {
857 b = p.knight_attacks(s) & ~p.pieces_of_color(them) & ~ei.attacked_by(us);
859 b2 = b & ei.attacked_by(them, KNIGHT);
860 if(b2) attackUnits += KnightCheckBonus * count_1s_max_15(b2);
863 // Analyse discovered checks (only for non-pawns right now, consider
864 // adding pawns later).
865 if(DiscoveredCheckBonus) {
866 b = p.discovered_check_candidates(them) & ~p.pawns();
869 DiscoveredCheckBonus * count_1s_max_15(b) * (sente? 2 : 1);
872 // Has a mate threat been found? We don't do anything here if the
873 // side with the mating move is the side to move, because in that
874 // case the mating side will get a huge bonus at the end of the main
875 // evaluation function instead.
876 if(ei.mateThreat[them] != MOVE_NONE)
877 attackUnits += MateThreatBonus;
879 // Ensure that attackUnits is between 0 and 99, in order to avoid array
880 // out of bounds errors:
881 if(attackUnits < 0) attackUnits = 0;
882 if(attackUnits >= 100) attackUnits = 99;
884 // Finally, extract the king safety score from the SafetyTable[] array.
885 // Add the score to the evaluation, and also to ei.futilityMargin. The
886 // reason for adding the king safety score to the futility margin is
887 // that the king safety scores can sometimes be very big, and that
888 // capturing a single attacking piece can therefore result in a score
889 // change far bigger than the value of the captured piece.
890 Value v = apply_weight(SafetyTable[attackUnits], WeightKingSafety[us]);
891 ei.mgValue -= sign * v;
892 if(us == p.side_to_move())
893 ei.futilityMargin += v;
898 // evaluate_passed_pawns() evaluates the passed pawns for both sides.
900 void evaluate_passed_pawns(const Position &pos, EvalInfo &ei) {
901 bool hasUnstoppable[2] = {false, false};
902 int movesToGo[2] = {100, 100};
904 for(Color us = WHITE; us <= BLACK; us++) {
905 Color them = opposite_color(us);
906 Square ourKingSq = pos.king_square(us);
907 Square theirKingSq = pos.king_square(them);
908 Bitboard b = ei.pi->passed_pawns() & pos.pawns(us), b2, b3, b4;
911 Square s = pop_1st_bit(&b);
912 assert(pos.piece_on(s) == pawn_of_color(us));
913 assert(pos.pawn_is_passed(us, s));
915 int r = int(pawn_rank(us, s) - RANK_2);
916 int tr = Max(0, r * (r-1));
917 Square blockSq = s + pawn_push(us);
919 // Base bonus based on rank:
920 Value mbonus = Value(20 * tr);
921 Value ebonus = Value(10 + r * r * 10);
923 // Adjust bonus based on king proximity:
924 ebonus -= Value(square_distance(ourKingSq, blockSq) * 3 * tr);
926 Value(square_distance(ourKingSq, blockSq + pawn_push(us)) * 1 * tr);
927 ebonus += Value(square_distance(theirKingSq, blockSq) * 6 * tr);
929 // If the pawn is free to advance, increase bonus:
930 if(pos.square_is_empty(blockSq)) {
932 b2 = squares_in_front_of(us, s);
933 b3 = b2 & ei.attacked_by(them);
934 b4 = b2 & ei.attacked_by(us);
935 if((b2 & pos.pieces_of_color(them)) == EmptyBoardBB) {
936 // There are no enemy pieces in the pawn's path! Are any of the
937 // squares in the pawn's path attacked by the enemy?
938 if(b3 == EmptyBoardBB)
939 // No enemy attacks, huge bonus!
940 ebonus += Value(tr * ((b2 == b4)? 17 : 15));
942 // OK, there are enemy attacks. Are those squares which are
943 // attacked by the enemy also attacked by us? If yes, big bonus
944 // (but smaller than when there are no enemy attacks), if no,
945 // somewhat smaller bonus.
946 ebonus += Value(tr * (((b3 & b4) == b3)? 13 : 8));
949 // There are some enemy pieces in the pawn's path. While this is
950 // sad, we still assign a moderate bonus if all squares in the path
951 // which are either occupied by or attacked by enemy pieces are
952 // also attacked by us.
953 if(((b3 | (b2 & pos.pieces_of_color(them))) & ~b4) == EmptyBoardBB)
954 ebonus += Value(tr * 6);
956 // At last, add a small bonus when there are no *friendly* pieces
957 // in the pawn's path:
958 if((b2 & pos.pieces_of_color(us)) == EmptyBoardBB)
962 // If the pawn is supported by a friendly pawn, increase bonus.
963 b2 = pos.pawns(us) & neighboring_files_bb(s);
965 ebonus += Value(r * 20);
966 else if(pos.pawn_attacks(them, s) & b2)
967 ebonus += Value(r * 12);
969 // If the other side has only a king, check whether the pawn is
971 if(pos.non_pawn_material(them) == Value(0)) {
975 qsq = relative_square(us, make_square(square_file(s), RANK_8));
976 d = square_distance(s, qsq) - square_distance(theirKingSq, qsq)
977 + ((us == pos.side_to_move())? 0 : 1);
980 int mtg = RANK_8 - pawn_rank(us, s);
982 count_1s_max_15(squares_in_front_of(us,s)&pos.occupied_squares());
986 hasUnstoppable[us] = true;
987 movesToGo[us] = Min(movesToGo[us], mtg);
991 // Rook pawns are a special case: They are sometimes worse, and
992 // sometimes better than other passed pawns. It is difficult to find
993 // good rules for determining whether they are good or bad. For now,
994 // we try the following: Increase the value for rook pawns if the
995 // other side has no pieces apart from a knight, and decrease the
996 // value if the other side has a rook or queen.
997 if(square_file(s) == FILE_A || square_file(s) == FILE_H) {
998 if(pos.non_pawn_material(them) == KnightValueMidgame
999 && pos.knight_count(them) == 1)
1000 ebonus += ebonus / 4;
1001 else if(pos.rooks_and_queens(them))
1002 ebonus -= ebonus / 4;
1005 // Add the scores for this pawn to the middle game and endgame eval.
1006 ei.mgValue += apply_weight(Sign[us] * mbonus, WeightPassedPawnsMidgame);
1007 ei.egValue += apply_weight(Sign[us] * ebonus, WeightPassedPawnsEndgame);
1011 // Does either side have an unstoppable passed pawn?
1012 if(hasUnstoppable[WHITE] && !hasUnstoppable[BLACK])
1013 ei.egValue += UnstoppablePawnValue - Value(0x40 * movesToGo[WHITE]);
1014 else if(hasUnstoppable[BLACK] && !hasUnstoppable[WHITE])
1015 ei.egValue -= UnstoppablePawnValue - Value(0x40 * movesToGo[BLACK]);
1016 else if(hasUnstoppable[BLACK] && hasUnstoppable[WHITE]) {
1017 // Both sides have unstoppable pawns! Try to find out who queens
1018 // first. We begin by transforming 'movesToGo' to the number of
1019 // plies until the pawn queens for both sides:
1020 movesToGo[WHITE] *= 2;
1021 movesToGo[BLACK] *= 2;
1022 movesToGo[pos.side_to_move()]--;
1024 // If one side queens at least three plies before the other, that
1026 if(movesToGo[WHITE] <= movesToGo[BLACK] - 3)
1027 ei.egValue += UnstoppablePawnValue - Value(0x40 * (movesToGo[WHITE]/2));
1028 else if(movesToGo[BLACK] <= movesToGo[WHITE] - 3)
1029 ei.egValue -= UnstoppablePawnValue - Value(0x40 * (movesToGo[BLACK]/2));
1031 // We could also add some rules about the situation when one side
1032 // queens exactly one ply before the other: Does the first queen
1033 // check the opponent's king, or attack the opponent's queening square?
1034 // This is slightly tricky to get right, because it is possible that
1035 // the opponent's king has moved somewhere before the first pawn queens.
1040 // evaluate_trapped_bishop_a7h7() determines whether a bishop on a7/h7
1041 // (a2/h2 for black) is trapped by enemy pawns, and assigns a penalty
1044 void evaluate_trapped_bishop_a7h7(const Position &pos, Square s, Color us,
1046 Piece pawn = pawn_of_color(opposite_color(us));
1049 assert(square_is_ok(s));
1050 assert(pos.piece_on(s) == bishop_of_color(us));
1052 if(square_file(s) == FILE_A) {
1053 b6 = relative_square(us, SQ_B6);
1054 b8 = relative_square(us, SQ_B8);
1057 b6 = relative_square(us, SQ_G6);
1058 b8 = relative_square(us, SQ_G8);
1061 if(pos.piece_on(b6) == pawn && pos.see(s, b6) < 0 && pos.see(s, b8) < 0) {
1062 ei.mgValue -= Sign[us] * TrappedBishopA7H7Penalty;
1063 ei.egValue -= Sign[us] * TrappedBishopA7H7Penalty;
1069 // evaluate_trapped_bishop_a1h1() determines whether a bishop on a1/h1
1070 // (a8/h8 for black) is trapped by a friendly pawn on b2/g2 (b7/g7 for
1071 // black), and assigns a penalty if it is. This pattern can obviously
1072 // only occur in Chess960 games.
1074 void evaluate_trapped_bishop_a1h1(const Position &pos, Square s, Color us,
1076 Piece pawn = pawn_of_color(us);
1080 assert(square_is_ok(s));
1081 assert(pos.piece_on(s) == bishop_of_color(us));
1083 if(square_file(s) == FILE_A) {
1084 b2 = relative_square(us, SQ_B2);
1085 b3 = relative_square(us, SQ_B3);
1086 c3 = relative_square(us, SQ_C3);
1089 b2 = relative_square(us, SQ_G2);
1090 b3 = relative_square(us, SQ_G3);
1091 c3 = relative_square(us, SQ_F3);
1094 if(pos.piece_on(b2) == pawn) {
1097 if(!pos.square_is_empty(b3))
1098 penalty = 2*TrappedBishopA1H1Penalty;
1099 else if(pos.piece_on(c3) == pawn)
1100 penalty = TrappedBishopA1H1Penalty;
1102 penalty = TrappedBishopA1H1Penalty / 2;
1104 ei.mgValue -= Sign[us] * penalty;
1105 ei.egValue -= Sign[us] * penalty;
1111 // apply_weight applies an evaluation weight to a value.
1113 inline Value apply_weight(Value v, int w) {
1114 return (v*w) / 0x100;
1118 // scale_by_game_phase interpolates between a middle game and an endgame
1119 // score, based on game phase. It also scales the return value by a
1120 // ScaleFactor array.
1122 Value scale_by_game_phase(Value mv, Value ev, Phase ph, ScaleFactor sf[]) {
1123 assert(mv > -VALUE_INFINITE && mv < VALUE_INFINITE);
1124 assert(ev > -VALUE_INFINITE && ev < VALUE_INFINITE);
1125 assert(ph >= PHASE_ENDGAME && ph <= PHASE_MIDGAME);
1128 ev = apply_scale_factor(ev, sf[WHITE]);
1130 ev = apply_scale_factor(ev, sf[BLACK]);
1132 // Superlinear interpolator
1133 int sli_ph = int(ph);
1134 sli_ph -= (64 - sli_ph) / 4;
1135 sli_ph = Min(PHASE_MIDGAME, Max(PHASE_ENDGAME, sli_ph)); // ceiling
1137 Value result = Value(int((mv * sli_ph + ev * (128 - sli_ph)) / 128));
1138 return Value(int(result) & ~(GrainSize - 1));
1142 // count_1s_8bit() counts the number of nonzero bits in the 8 least
1143 // significant bits of a Bitboard. This function is used by the king
1144 // shield evaluation.
1146 int count_1s_8bit(Bitboard b) {
1147 return int(BitCount8Bit[b & 0xFF]);
1151 // compute_weight() computes the value of an evaluation weight, by combining
1152 // an UCI-configurable weight with an internal weight.
1154 int compute_weight(int uciWeight, int internalWeight) {
1155 uciWeight = (uciWeight * 0x100) / 100;
1156 return (uciWeight * internalWeight) / 0x100;
1160 // init_safety() initizes the king safety evaluation, based on UCI
1161 // parameters. It is called from read_weights().
1163 void init_safety() {
1165 int maxSlope, peak, i, j;
1167 QueenContactCheckBonus = get_option_value_int("Queen Contact Check Bonus");
1168 RookContactCheckBonus = get_option_value_int("Rook Contact Check Bonus");
1169 QueenCheckBonus = get_option_value_int("Queen Check Bonus");
1170 RookCheckBonus = get_option_value_int("Rook Check Bonus");
1171 BishopCheckBonus = get_option_value_int("Bishop Check Bonus");
1172 KnightCheckBonus = get_option_value_int("Knight Check Bonus");
1173 DiscoveredCheckBonus = get_option_value_int("Discovered Check Bonus");
1174 MateThreatBonus = get_option_value_int("Mate Threat Bonus");
1176 a = get_option_value_int("King Safety Coefficient") / 100.0;
1177 b = get_option_value_int("King Safety X Intercept") * 1.0;
1178 maxSlope = get_option_value_int("King Safety Max Slope");
1179 peak = (get_option_value_int("King Safety Max Value") * 256) / 100;
1181 for(i = 0; i < 100; i++) {
1182 if(i < b) SafetyTable[i] = Value(0);
1183 else if(get_option_value_string("King Safety Curve") == "Quadratic")
1184 SafetyTable[i] = Value((int)(a * (i - b) * (i - b)));
1185 else if(get_option_value_string("King Safety Curve") == "Linear")
1186 SafetyTable[i] = Value((int)(100 * a * (i - b)));
1189 for(i = 0; i < 100; i++)
1190 if(SafetyTable[i+1] - SafetyTable[i] > maxSlope) {
1191 for(j = i + 1; j < 100; j++)
1192 SafetyTable[j] = SafetyTable[j-1] + Value(maxSlope);
1194 for(i = 0; i < 100; i++)
1195 if(SafetyTable[i] > Value(peak))
1196 SafetyTable[i] = Value(peak);