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));
332 ei.attackedBy[BLACK][KING] | (ei.attackedBy[BLACK][KING] >> 8);
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.kingAttackersCount[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.kingAttackersCount[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.kingZone[us])
585 ei.kingAttackersCount[us]++;
586 ei.kingAttackersWeight[us] += AttackWeight;
587 Bitboard bb = (b & ei.attackedBy[them][KING]);
589 ei.kingZoneAttacksCount[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 //Bitboard b = p.rook_attacks(s);
654 Bitboard b = rook_attacks_bb(s, p.occupied_squares() & ~p.rooks_and_queens(us));
655 ei.attackedBy[us][ROOK] |= b;
657 // King attack and mobility
658 int mob = evaluate_common(p, b, us, ei, RookAttackWeight, MidgameRookMobilityBonus,
659 EndgameRookMobilityBonus);
662 Color them = opposite_color(us);
664 if ( relative_rank(us, s) == RANK_7
665 && relative_rank(us, p.king_square(them)) == RANK_8)
667 ei.mgValue += Sign[us] * MidgameRookOn7thBonus;
668 ei.egValue += Sign[us] * EndgameRookOn7thBonus;
671 // Open and half-open files
672 File f = square_file(s);
673 if (ei.pi->file_is_half_open(us, f))
675 if (ei.pi->file_is_half_open(them, f))
677 ei.mgValue += Sign[us] * RookOpenFileBonus;
678 ei.egValue += Sign[us] * RookOpenFileBonus;
682 ei.mgValue += Sign[us] * RookHalfOpenFileBonus;
683 ei.egValue += Sign[us] * RookHalfOpenFileBonus;
687 // Penalize rooks which are trapped inside a king. Penalize more if
688 // king has lost right to castle
689 if (mob > 6 || ei.pi->file_is_half_open(us, f))
692 Square ksq = p.king_square(us);
694 if ( square_file(ksq) >= FILE_E
695 && square_file(s) > square_file(ksq)
696 && (relative_rank(us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
698 // Is there a half-open file between the king and the edge of the board?
699 if (!ei.pi->has_open_file_to_right(us, square_file(ksq)))
700 ei.mgValue -= p.can_castle(us)? Sign[us] * ((TrappedRookPenalty - mob * 16) / 2)
701 : Sign[us] * (TrappedRookPenalty - mob * 16);
703 else if ( square_file(ksq) <= FILE_D
704 && square_file(s) < square_file(ksq)
705 && (relative_rank(us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
707 // Is there a half-open file between the king and the edge of the board?
708 if (!ei.pi->has_open_file_to_left(us, square_file(ksq)))
709 ei.mgValue -= p.can_castle(us)? Sign[us] * ((TrappedRookPenalty - mob * 16) / 2)
710 : Sign[us] * (TrappedRookPenalty - mob * 16);
715 // evaluate_queen() assigns bonuses and penalties to a queen of a given
716 // color on a given square.
718 void evaluate_queen(const Position &p, Square s, Color us, EvalInfo &ei) {
720 Bitboard b = p.queen_attacks(s);
721 ei.attackedBy[us][QUEEN] |= b;
723 // King attack and mobility
724 evaluate_common(p, b, us, ei, QueenAttackWeight, MidgameQueenMobilityBonus,
725 EndgameQueenMobilityBonus);
728 Color them = opposite_color(us);
730 if ( relative_rank(us, s) == RANK_7
731 && relative_rank(us, p.king_square(them)) == RANK_8)
733 ei.mgValue += Sign[us] * MidgameQueenOn7thBonus;
734 ei.egValue += Sign[us] * EndgameQueenOn7thBonus;
739 // evaluate_king() assigns bonuses and penalties to a king of a given
740 // color on a given square.
742 void evaluate_king(const Position &p, Square s, Color us, EvalInfo &ei) {
744 int shelter = 0, sign = Sign[us];
747 if(relative_rank(us, s) <= RANK_4) {
748 Bitboard pawns = p.pawns(us) & this_and_neighboring_files_bb(s);
749 Rank r = square_rank(s);
750 for(int i = 0; i < 3; i++)
751 shelter += count_1s_8bit(pawns >> ((r+(i+1)*sign) * 8)) * (64>>i);
752 ei.mgValue += sign * Value(shelter);
755 // King safety. This is quite complicated, and is almost certainly far
756 // from optimally tuned.
757 Color them = opposite_color(us);
758 if(p.queen_count(them) >= 1 && ei.kingAttackersCount[them] >= 2
759 && p.non_pawn_material(them) >= QueenValueMidgame + RookValueMidgame
760 && ei.kingZoneAttacksCount[them]) {
762 // Is it the attackers turn to move?
763 bool sente = (them == p.side_to_move());
765 // Find the attacked squares around the king which has no defenders
766 // apart from the king itself:
767 Bitboard undefended =
768 ei.attacked_by(them) & ~ei.attacked_by(us, PAWN)
769 & ~ei.attacked_by(us, KNIGHT) & ~ei.attacked_by(us, BISHOP)
770 & ~ei.attacked_by(us, ROOK) & ~ei.attacked_by(us, QUEEN)
771 & ei.attacked_by(us, KING);
772 Bitboard occ = p.occupied_squares(), b, b2;
774 // Initialize the 'attackUnits' variable, which is used later on as an
775 // index to the SafetyTable[] array. The initial is based on the number
776 // and types of the attacking pieces, the number of attacked and
777 // undefended squares around the king, the square of the king, and the
778 // quality of the pawn shelter.
780 Min((ei.kingAttackersCount[them] * ei.kingAttackersWeight[them]) / 2, 25)
781 + (ei.kingZoneAttacksCount[them] + count_1s_max_15(undefended)) * 3
782 + InitKingDanger[relative_square(us, s)] - shelter / 32;
784 // Analyse safe queen contact checks:
785 b = undefended & ei.attacked_by(them, QUEEN) & ~p.pieces_of_color(them);
787 Bitboard attackedByOthers =
788 ei.attacked_by(them, PAWN) | ei.attacked_by(them, KNIGHT)
789 | ei.attacked_by(them, BISHOP) | ei.attacked_by(them, ROOK);
790 b &= attackedByOthers;
792 // The bitboard b now contains the squares available for safe queen
794 int count = count_1s_max_15(b);
795 attackUnits += QueenContactCheckBonus * count * (sente? 2 : 1);
797 // Is there a mate threat?
798 if(QueenContactMates && !p.is_check()) {
799 Bitboard escapeSquares =
800 p.king_attacks(s) & ~p.pieces_of_color(us) & ~attackedByOthers;
802 Square from, to = pop_1st_bit(&b);
804 & ~queen_attacks_bb(to, occ & clear_mask_bb(s)))) {
805 // We have a mate, unless the queen is pinned or there
806 // is an X-ray attack through the queen.
807 for(int i = 0; i < p.queen_count(them); i++) {
808 from = p.queen_list(them, i);
809 if(bit_is_set(p.queen_attacks(from), to)
810 && !bit_is_set(p.pinned_pieces(them), from)
811 && !(rook_attacks_bb(to, occ & clear_mask_bb(from))
812 & p.rooks_and_queens(us))
813 && !(rook_attacks_bb(to, occ & clear_mask_bb(from))
814 & p.rooks_and_queens(us)))
815 ei.mateThreat[them] = make_move(from, to);
823 // Analyse safe rook contact checks:
824 if(RookContactCheckBonus) {
825 b = undefended & ei.attacked_by(them, ROOK) & ~p.pieces_of_color(them);
827 Bitboard attackedByOthers =
828 ei.attacked_by(them, PAWN) | ei.attacked_by(them, KNIGHT)
829 | ei.attacked_by(them, BISHOP) | ei.attacked_by(them, QUEEN);
830 b &= attackedByOthers;
832 int count = count_1s_max_15(b);
833 attackUnits += (RookContactCheckBonus * count * (sente? 2 : 1));
838 // Analyse safe distance checks:
839 if(QueenCheckBonus > 0 || RookCheckBonus > 0) {
840 b = p.rook_attacks(s) & ~p.pieces_of_color(them) & ~ei.attacked_by(us);
843 b2 = b & ei.attacked_by(them, QUEEN);
844 if(b2) attackUnits += QueenCheckBonus * count_1s_max_15(b2);
847 b2 = b & ei.attacked_by(them, ROOK);
848 if(b2) attackUnits += RookCheckBonus * count_1s_max_15(b2);
850 if(QueenCheckBonus > 0 || BishopCheckBonus > 0) {
851 b = p.bishop_attacks(s) & ~p.pieces_of_color(them) & ~ei.attacked_by(us);
853 b2 = b & ei.attacked_by(them, QUEEN);
854 if(b2) attackUnits += QueenCheckBonus * count_1s_max_15(b2);
857 b2 = b & ei.attacked_by(them, BISHOP);
858 if(b2) attackUnits += BishopCheckBonus * count_1s_max_15(b2);
860 if(KnightCheckBonus > 0) {
861 b = p.knight_attacks(s) & ~p.pieces_of_color(them) & ~ei.attacked_by(us);
863 b2 = b & ei.attacked_by(them, KNIGHT);
864 if(b2) attackUnits += KnightCheckBonus * count_1s_max_15(b2);
867 // Analyse discovered checks (only for non-pawns right now, consider
868 // adding pawns later).
869 if(DiscoveredCheckBonus) {
870 b = p.discovered_check_candidates(them) & ~p.pawns();
873 DiscoveredCheckBonus * count_1s_max_15(b) * (sente? 2 : 1);
876 // Has a mate threat been found? We don't do anything here if the
877 // side with the mating move is the side to move, because in that
878 // case the mating side will get a huge bonus at the end of the main
879 // evaluation function instead.
880 if(ei.mateThreat[them] != MOVE_NONE)
881 attackUnits += MateThreatBonus;
883 // Ensure that attackUnits is between 0 and 99, in order to avoid array
884 // out of bounds errors:
885 if(attackUnits < 0) attackUnits = 0;
886 if(attackUnits >= 100) attackUnits = 99;
888 // Finally, extract the king safety score from the SafetyTable[] array.
889 // Add the score to the evaluation, and also to ei.futilityMargin. The
890 // reason for adding the king safety score to the futility margin is
891 // that the king safety scores can sometimes be very big, and that
892 // capturing a single attacking piece can therefore result in a score
893 // change far bigger than the value of the captured piece.
894 Value v = apply_weight(SafetyTable[attackUnits], WeightKingSafety[us]);
895 ei.mgValue -= sign * v;
896 if(us == p.side_to_move())
897 ei.futilityMargin += v;
902 // evaluate_passed_pawns() evaluates the passed pawns for both sides.
904 void evaluate_passed_pawns(const Position &pos, EvalInfo &ei) {
905 bool hasUnstoppable[2] = {false, false};
906 int movesToGo[2] = {100, 100};
908 for(Color us = WHITE; us <= BLACK; us++) {
909 Color them = opposite_color(us);
910 Square ourKingSq = pos.king_square(us);
911 Square theirKingSq = pos.king_square(them);
912 Bitboard b = ei.pi->passed_pawns() & pos.pawns(us), b2, b3, b4;
915 Square s = pop_1st_bit(&b);
916 assert(pos.piece_on(s) == pawn_of_color(us));
917 assert(pos.pawn_is_passed(us, s));
919 int r = int(relative_rank(us, s) - RANK_2);
920 int tr = Max(0, r * (r-1));
921 Square blockSq = s + pawn_push(us);
923 // Base bonus based on rank:
924 Value mbonus = Value(20 * tr);
925 Value ebonus = Value(10 + r * r * 10);
927 // Adjust bonus based on king proximity:
928 ebonus -= Value(square_distance(ourKingSq, blockSq) * 3 * tr);
930 Value(square_distance(ourKingSq, blockSq + pawn_push(us)) * 1 * tr);
931 ebonus += Value(square_distance(theirKingSq, blockSq) * 6 * tr);
933 // If the pawn is free to advance, increase bonus:
934 if(pos.square_is_empty(blockSq)) {
936 b2 = squares_in_front_of(us, s);
937 b3 = b2 & ei.attacked_by(them);
938 b4 = b2 & ei.attacked_by(us);
939 if((b2 & pos.pieces_of_color(them)) == EmptyBoardBB) {
940 // There are no enemy pieces in the pawn's path! Are any of the
941 // squares in the pawn's path attacked by the enemy?
942 if(b3 == EmptyBoardBB)
943 // No enemy attacks, huge bonus!
944 ebonus += Value(tr * ((b2 == b4)? 17 : 15));
946 // OK, there are enemy attacks. Are those squares which are
947 // attacked by the enemy also attacked by us? If yes, big bonus
948 // (but smaller than when there are no enemy attacks), if no,
949 // somewhat smaller bonus.
950 ebonus += Value(tr * (((b3 & b4) == b3)? 13 : 8));
953 // There are some enemy pieces in the pawn's path. While this is
954 // sad, we still assign a moderate bonus if all squares in the path
955 // which are either occupied by or attacked by enemy pieces are
956 // also attacked by us.
957 if(((b3 | (b2 & pos.pieces_of_color(them))) & ~b4) == EmptyBoardBB)
958 ebonus += Value(tr * 6);
960 // At last, add a small bonus when there are no *friendly* pieces
961 // in the pawn's path:
962 if((b2 & pos.pieces_of_color(us)) == EmptyBoardBB)
966 // If the pawn is supported by a friendly pawn, increase bonus.
967 b2 = pos.pawns(us) & neighboring_files_bb(s);
969 ebonus += Value(r * 20);
970 else if(pos.pawn_attacks(them, s) & b2)
971 ebonus += Value(r * 12);
973 // If the other side has only a king, check whether the pawn is
975 if(pos.non_pawn_material(them) == Value(0)) {
979 qsq = relative_square(us, make_square(square_file(s), RANK_8));
980 d = square_distance(s, qsq) - square_distance(theirKingSq, qsq)
981 + ((us == pos.side_to_move())? 0 : 1);
984 int mtg = RANK_8 - relative_rank(us, s);
986 count_1s_max_15(squares_in_front_of(us,s)&pos.occupied_squares());
990 hasUnstoppable[us] = true;
991 movesToGo[us] = Min(movesToGo[us], mtg);
995 // Rook pawns are a special case: They are sometimes worse, and
996 // sometimes better than other passed pawns. It is difficult to find
997 // good rules for determining whether they are good or bad. For now,
998 // we try the following: Increase the value for rook pawns if the
999 // other side has no pieces apart from a knight, and decrease the
1000 // value if the other side has a rook or queen.
1001 if(square_file(s) == FILE_A || square_file(s) == FILE_H) {
1002 if(pos.non_pawn_material(them) == KnightValueMidgame
1003 && pos.knight_count(them) == 1)
1004 ebonus += ebonus / 4;
1005 else if(pos.rooks_and_queens(them))
1006 ebonus -= ebonus / 4;
1009 // Add the scores for this pawn to the middle game and endgame eval.
1010 ei.mgValue += apply_weight(Sign[us] * mbonus, WeightPassedPawnsMidgame);
1011 ei.egValue += apply_weight(Sign[us] * ebonus, WeightPassedPawnsEndgame);
1015 // Does either side have an unstoppable passed pawn?
1016 if(hasUnstoppable[WHITE] && !hasUnstoppable[BLACK])
1017 ei.egValue += UnstoppablePawnValue - Value(0x40 * movesToGo[WHITE]);
1018 else if(hasUnstoppable[BLACK] && !hasUnstoppable[WHITE])
1019 ei.egValue -= UnstoppablePawnValue - Value(0x40 * movesToGo[BLACK]);
1020 else if(hasUnstoppable[BLACK] && hasUnstoppable[WHITE]) {
1021 // Both sides have unstoppable pawns! Try to find out who queens
1022 // first. We begin by transforming 'movesToGo' to the number of
1023 // plies until the pawn queens for both sides:
1024 movesToGo[WHITE] *= 2;
1025 movesToGo[BLACK] *= 2;
1026 movesToGo[pos.side_to_move()]--;
1028 // If one side queens at least three plies before the other, that
1030 if(movesToGo[WHITE] <= movesToGo[BLACK] - 3)
1031 ei.egValue += UnstoppablePawnValue - Value(0x40 * (movesToGo[WHITE]/2));
1032 else if(movesToGo[BLACK] <= movesToGo[WHITE] - 3)
1033 ei.egValue -= UnstoppablePawnValue - Value(0x40 * (movesToGo[BLACK]/2));
1035 // We could also add some rules about the situation when one side
1036 // queens exactly one ply before the other: Does the first queen
1037 // check the opponent's king, or attack the opponent's queening square?
1038 // This is slightly tricky to get right, because it is possible that
1039 // the opponent's king has moved somewhere before the first pawn queens.
1044 // evaluate_trapped_bishop_a7h7() determines whether a bishop on a7/h7
1045 // (a2/h2 for black) is trapped by enemy pawns, and assigns a penalty
1048 void evaluate_trapped_bishop_a7h7(const Position &pos, Square s, Color us,
1051 assert(square_is_ok(s));
1052 assert(pos.piece_on(s) == bishop_of_color(us));
1054 Square b6 = relative_square(us, (square_file(s) == FILE_A) ? SQ_B6 : SQ_G6);
1055 Square b8 = relative_square(us, (square_file(s) == FILE_A) ? SQ_B8 : SQ_G8);
1057 if ( pos.piece_on(b6) == pawn_of_color(opposite_color(us))
1058 && pos.see(s, b6) < 0
1059 && pos.see(s, b8) < 0)
1061 ei.mgValue -= Sign[us] * TrappedBishopA7H7Penalty;
1062 ei.egValue -= Sign[us] * TrappedBishopA7H7Penalty;
1067 // evaluate_trapped_bishop_a1h1() determines whether a bishop on a1/h1
1068 // (a8/h8 for black) is trapped by a friendly pawn on b2/g2 (b7/g7 for
1069 // black), and assigns a penalty if it is. This pattern can obviously
1070 // only occur in Chess960 games.
1072 void evaluate_trapped_bishop_a1h1(const Position &pos, Square s, Color us,
1074 Piece pawn = pawn_of_color(us);
1078 assert(square_is_ok(s));
1079 assert(pos.piece_on(s) == bishop_of_color(us));
1081 if(square_file(s) == FILE_A) {
1082 b2 = relative_square(us, SQ_B2);
1083 b3 = relative_square(us, SQ_B3);
1084 c3 = relative_square(us, SQ_C3);
1087 b2 = relative_square(us, SQ_G2);
1088 b3 = relative_square(us, SQ_G3);
1089 c3 = relative_square(us, SQ_F3);
1092 if(pos.piece_on(b2) == pawn) {
1095 if(!pos.square_is_empty(b3))
1096 penalty = 2*TrappedBishopA1H1Penalty;
1097 else if(pos.piece_on(c3) == pawn)
1098 penalty = TrappedBishopA1H1Penalty;
1100 penalty = TrappedBishopA1H1Penalty / 2;
1102 ei.mgValue -= Sign[us] * penalty;
1103 ei.egValue -= Sign[us] * penalty;
1109 // apply_weight applies an evaluation weight to a value.
1111 inline Value apply_weight(Value v, int w) {
1112 return (v*w) / 0x100;
1116 // scale_by_game_phase interpolates between a middle game and an endgame
1117 // score, based on game phase. It also scales the return value by a
1118 // ScaleFactor array.
1120 Value scale_by_game_phase(Value mv, Value ev, Phase ph, ScaleFactor sf[]) {
1122 assert(mv > -VALUE_INFINITE && mv < VALUE_INFINITE);
1123 assert(ev > -VALUE_INFINITE && ev < VALUE_INFINITE);
1124 assert(ph >= PHASE_ENDGAME && ph <= PHASE_MIDGAME);
1126 ev = apply_scale_factor(ev, sf[(ev > Value(0) ? WHITE : BLACK)]);
1128 // Linearized sigmoid interpolator
1130 sph -= (64 - sph) / 4;
1131 sph = Min(PHASE_MIDGAME, Max(PHASE_ENDGAME, sph));
1133 Value result = Value(int((mv * sph + ev * (128 - sph)) / 128));
1135 return Value(int(result) & ~(GrainSize - 1));
1139 // count_1s_8bit() counts the number of nonzero bits in the 8 least
1140 // significant bits of a Bitboard. This function is used by the king
1141 // shield evaluation.
1143 int count_1s_8bit(Bitboard b) {
1144 return int(BitCount8Bit[b & 0xFF]);
1148 // compute_weight() computes the value of an evaluation weight, by combining
1149 // an UCI-configurable weight with an internal weight.
1151 int compute_weight(int uciWeight, int internalWeight) {
1152 uciWeight = (uciWeight * 0x100) / 100;
1153 return (uciWeight * internalWeight) / 0x100;
1157 // init_safety() initizes the king safety evaluation, based on UCI
1158 // parameters. It is called from read_weights().
1160 void init_safety() {
1162 QueenContactCheckBonus = get_option_value_int("Queen Contact Check Bonus");
1163 RookContactCheckBonus = get_option_value_int("Rook Contact Check Bonus");
1164 QueenCheckBonus = get_option_value_int("Queen Check Bonus");
1165 RookCheckBonus = get_option_value_int("Rook Check Bonus");
1166 BishopCheckBonus = get_option_value_int("Bishop Check Bonus");
1167 KnightCheckBonus = get_option_value_int("Knight Check Bonus");
1168 DiscoveredCheckBonus = get_option_value_int("Discovered Check Bonus");
1169 MateThreatBonus = get_option_value_int("Mate Threat Bonus");
1171 int maxSlope = get_option_value_int("King Safety Max Slope");
1172 int peak = get_option_value_int("King Safety Max Value") * 256 / 100;
1173 double a = get_option_value_int("King Safety Coefficient") / 100.0;
1174 double b = get_option_value_int("King Safety X Intercept");
1175 bool quad = (get_option_value_string("King Safety Curve") == "Quadratic");
1176 bool linear = (get_option_value_string("King Safety Curve") == "Linear");
1178 for (int i = 0; i < 100; i++)
1181 SafetyTable[i] = Value(0);
1183 SafetyTable[i] = Value((int)(a * (i - b) * (i - b)));
1185 SafetyTable[i] = Value((int)(100 * a * (i - b)));
1188 for (int i = 0; i < 100; i++)
1190 if (SafetyTable[i+1] - SafetyTable[i] > maxSlope)
1191 for (int j = i + 1; j < 100; j++)
1192 SafetyTable[j] = SafetyTable[j-1] + Value(maxSlope);
1194 if (SafetyTable[i] > Value(peak))
1195 SafetyTable[i] = Value(peak);