2 Glaurung, a UCI chess playing engine.
3 Copyright (C) 2004-2008 Tord Romstad
5 Glaurung is free software: you can redistribute it and/or modify
6 it under the terms of the GNU General Public License as published by
7 the Free Software Foundation, either version 3 of the License, or
8 (at your option) any later version.
10 Glaurung is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 GNU General Public License for more details.
15 You should have received a copy of the GNU General Public License
16 along with this program. If not, see <http://www.gnu.org/licenses/>.
32 #include "ucioption.h"
36 //// Local definitions
41 const int Sign[2] = {1, -1};
43 // Evaluation grain size, must be a power of 2.
44 const int GrainSize = 4;
47 int WeightMobilityMidgame = 0x100;
48 int WeightMobilityEndgame = 0x100;
49 int WeightPawnStructureMidgame = 0x100;
50 int WeightPawnStructureEndgame = 0x100;
51 int WeightPassedPawnsMidgame = 0x100;
52 int WeightPassedPawnsEndgame = 0x100;
53 int WeightKingSafety[2] = { 0x100, 0x100 };
55 // Internal evaluation weights. These are applied on top of the evaluation
56 // weights read from UCI parameters. The purpose is to be able to change
57 // the evaluation weights while keeping the default values of the UCI
58 // parameters at 100, which looks prettier.
59 const int WeightMobilityMidgameInternal = 0x100;
60 const int WeightMobilityEndgameInternal = 0x100;
61 const int WeightPawnStructureMidgameInternal = 0x100;
62 const int WeightPawnStructureEndgameInternal = 0x100;
63 const int WeightPassedPawnsMidgameInternal = 0x100;
64 const int WeightPassedPawnsEndgameInternal = 0x100;
65 const int WeightKingSafetyInternal = 0x100;
66 const int WeightKingOppSafetyInternal = 0x100;
68 // Visually better to define tables constants
71 // Knight mobility bonus in middle game and endgame, indexed by the number
72 // of attacked squares not occupied by friendly piecess.
73 const Value MidgameKnightMobilityBonus[] = {
75 V(-30), V(-20),V(-10), V(0), V(10), V(20), V(25), V(30), V(30)
78 const Value EndgameKnightMobilityBonus[] = {
80 V(-30), V(-20),V(-10), V(0), V(10), V(20), V(25), V(30), V(30)
83 // Bishop mobility bonus in middle game and endgame, indexed by the number
84 // of attacked squares not occupied by friendly pieces. X-ray attacks through
85 // queens are also included.
86 const Value MidgameBishopMobilityBonus[] = {
88 V(-30), V(-15), V(0), V(15), V(30), V(45), V(58), V(66),
89 // 8 9 10 11 12 13 14 15
90 V( 72), V( 76), V(78), V(80), V(81), V(82), V(83), V(83)
93 const Value EndgameBishopMobilityBonus[] = {
95 V(-30), V(-15), V(0), V(15), V(30), V(45), V(58), V(66),
96 // 8 9 10 11 12 13 14 15
97 V( 72), V( 76), V(78), V(80), V(81), V(82), V(83), V(83)
100 // Rook mobility bonus in middle game and endgame, indexed by the number
101 // of attacked squares not occupied by friendly pieces. X-ray attacks through
102 // queens and rooks are also included.
103 const Value MidgameRookMobilityBonus[] = {
105 V(-18), V(-12), V(-6), V(0), V(6), V(12), V(16), V(21),
106 // 8 9 10 11 12 13 14 15
107 V( 24), V( 27), V(28), V(29), V(30), V(31), V(32), V(33)
110 const Value EndgameRookMobilityBonus[] = {
112 V(-30), V(-18), V(-6), V(6), V(18), V(30), V(42), V(54),
113 // 8 9 10 11 12 13 14 15
114 V( 66), V( 74), V(78), V(80), V(81), V(82), V(83), V(83)
117 // Queen mobility bonus in middle game and endgame, indexed by the number
118 // of attacked squares not occupied by friendly pieces.
119 const Value MidgameQueenMobilityBonus[] = {
121 V(-10), V(-8), V(-6), V(-4), V(-2), V( 0), V( 2), V( 4),
122 // 8 9 10 11 12 13 14 15
123 V( 6), V( 8), V(10), V(12), V(13), V(14), V(15), V(16),
124 // 16 17 18 19 20 21 22 23
125 V( 16), V(16), V(16), V(16), V(16), V(16), V(16), V(16),
126 // 24 25 26 27 28 29 30 31
127 V( 16), V(16), V(16), V(16), V(16), V(16), V(16), V(16)
130 const Value EndgameQueenMobilityBonus[] = {
132 V(-20),V(-15),V(-10), V(-5), V( 0), V( 5), V(10), V(15),
133 // 8 9 10 11 12 13 14 15
134 V( 19), V(23), V(27), V(29), V(30), V(30), V(30), V(30),
135 // 16 17 18 19 20 21 22 23
136 V( 30), V(30), V(30), V(30), V(30), V(30), V(30), V(30),
137 // 24 25 26 27 28 29 30 31
138 V( 30), V(30), V(30), V(30), V(30), V(30), V(30), V(30)
141 // Outpost bonuses for knights and bishops, indexed by square (from white's
143 const Value KnightOutpostBonus[64] = {
145 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 1
146 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 2
147 V(0), V(0), V(5),V(10),V(10), V(5), V(0), V(0), // 3
148 V(0), V(5),V(20),V(30),V(30),V(20), V(5), V(0), // 4
149 V(0),V(10),V(30),V(40),V(40),V(30),V(10), V(0), // 5
150 V(0), V(5),V(20),V(20),V(20),V(20), V(5), V(0), // 6
151 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 7
152 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0) // 8
155 const Value BishopOutpostBonus[64] = {
157 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 1
158 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 2
159 V(0), V(0), V(5), V(5), V(5), V(5), V(0), V(0), // 3
160 V(0), V(5),V(10),V(10),V(10),V(10), V(5), V(0), // 4
161 V(0),V(10),V(20),V(20),V(20),V(20),V(10), V(0), // 5
162 V(0), V(5), V(8), V(8), V(8), V(8), V(5), V(0), // 6
163 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 7
164 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0) // 8
167 // Bonus for unstoppable passed pawns:
168 const Value UnstoppablePawnValue = Value(0x500);
170 // Rooks and queens on the 7th rank:
171 const Value MidgameRookOn7thBonus = Value(50);
172 const Value EndgameRookOn7thBonus = Value(100);
173 const Value MidgameQueenOn7thBonus = Value(25);
174 const Value EndgameQueenOn7thBonus = Value(50);
176 // Rooks on open files:
177 const Value RookOpenFileBonus = Value(40);
178 const Value RookHalfOpenFileBonus = Value(20);
180 // Penalty for rooks trapped inside a friendly king which has lost the
182 const Value TrappedRookPenalty = Value(180);
184 // Penalty for a bishop on a7/h7 (a2/h2 for black) which is trapped by
186 const Value TrappedBishopA7H7Penalty = Value(300);
188 // Bitboard masks for detecting trapped bishops on a7/h7 (a2/h2 for black):
189 const Bitboard MaskA7H7[2] = {
190 ((1ULL << SQ_A7) | (1ULL << SQ_H7)),
191 ((1ULL << SQ_A2) | (1ULL << SQ_H2))
194 // Penalty for a bishop on a1/h1 (a8/h8 for black) which is trapped by
195 // a friendly pawn on b2/g2 (b7/g7 for black). This can obviously only
196 // happen in Chess960 games.
197 const Value TrappedBishopA1H1Penalty = Value(100);
199 // Bitboard masks for detecting trapped bishops on a1/h1 (a8/h8 for black):
200 const Bitboard MaskA1H1[2] = {
201 ((1ULL << SQ_A1) | (1ULL << SQ_H1)),
202 ((1ULL << SQ_A8) | (1ULL << SQ_H8))
205 /// King safety constants and variables. The king safety scores are taken
206 /// from the array SafetyTable[]. Various little "meta-bonuses" measuring
207 /// the strength of the attack are added up into an integer, which is used
208 /// as an index to SafetyTable[].
210 // Attack weights for each piece type.
211 const int QueenAttackWeight = 5;
212 const int RookAttackWeight = 3;
213 const int BishopAttackWeight = 2;
214 const int KnightAttackWeight = 2;
216 // Bonuses for safe checks for each piece type.
217 int QueenContactCheckBonus = 4;
218 int RookContactCheckBonus = 2;
219 int QueenCheckBonus = 2;
220 int RookCheckBonus = 1;
221 int BishopCheckBonus = 1;
222 int KnightCheckBonus = 1;
223 int DiscoveredCheckBonus = 3;
225 // Scan for queen contact mates?
226 const bool QueenContactMates = true;
228 // Bonus for having a mate threat.
229 int MateThreatBonus = 3;
231 // InitKingDanger[] contains bonuses based on the position of the defending
233 const int InitKingDanger[64] = {
234 2, 0, 2, 5, 5, 2, 0, 2,
235 2, 2, 4, 8, 8, 4, 2, 2,
236 7, 10, 12, 12, 12, 12, 10, 7,
237 15, 15, 15, 15, 15, 15, 15, 15,
238 15, 15, 15, 15, 15, 15, 15, 15,
239 15, 15, 15, 15, 15, 15, 15, 15,
240 15, 15, 15, 15, 15, 15, 15, 15,
241 15, 15, 15, 15, 15, 15, 15, 15
244 // SafetyTable[] contains the actual king safety scores. It is initialized
246 Value SafetyTable[100];
248 // Pawn and material hash tables, indexed by the current thread id:
249 PawnInfoTable *PawnTable[8] = {0, 0, 0, 0, 0, 0, 0, 0};
250 MaterialInfoTable *MaterialTable[8] = {0, 0, 0, 0, 0, 0, 0, 0};
252 // Sizes of pawn and material hash tables:
253 const int PawnTableSize = 16384;
254 const int MaterialTableSize = 1024;
256 // Array which gives the number of nonzero bits in an 8-bit integer:
257 uint8_t BitCount8Bit[256];
259 // Function prototypes:
260 void evaluate_knight(const Position &p, Square s, Color us, EvalInfo &ei);
261 void evaluate_bishop(const Position &p, Square s, Color us, EvalInfo &ei);
262 void evaluate_rook(const Position &p, Square s, Color us, EvalInfo &ei);
263 void evaluate_queen(const Position &p, Square s, Color us, EvalInfo &ei);
264 void evaluate_king(const Position &p, Square s, Color us, EvalInfo &ei);
266 void evaluate_passed_pawns(const Position &pos, EvalInfo &ei);
267 void evaluate_trapped_bishop_a7h7(const Position &pos, Square s, Color us,
269 void evaluate_trapped_bishop_a1h1(const Position &pos, Square s, Color us,
272 inline Value apply_weight(Value v, int w);
273 Value scale_by_game_phase(Value mv, Value ev, Phase ph, ScaleFactor sf[]);
275 int count_1s_8bit(Bitboard b);
277 int compute_weight(int uciWeight, int internalWeight);
278 int weight_option(const std::string& opt, int weight);
288 /// evaluate() is the main evaluation function. It always computes two
289 /// values, an endgame score and a middle game score, and interpolates
290 /// between them based on the remaining material.
292 Value evaluate(const Position &pos, EvalInfo &ei, int threadID) {
295 assert(threadID >= 0 && threadID < THREAD_MAX);
297 memset(&ei, 0, sizeof(EvalInfo));
299 // Initialize by reading the incrementally updated scores included in the
300 // position object (material + piece square tables)
301 ei.mgValue = pos.mg_value();
302 ei.egValue = pos.eg_value();
304 // Probe the material hash table
305 ei.mi = MaterialTable[threadID]->get_material_info(pos);
306 ei.mgValue += ei.mi->mg_value();
307 ei.egValue += ei.mi->eg_value();
309 // If we have a specialized evaluation function for the current material
310 // configuration, call it and return
311 if (ei.mi->specialized_eval_exists())
312 return ei.mi->evaluate(pos);
314 // After get_material_info() call that modifies them
315 ScaleFactor factor[2];
316 factor[WHITE] = ei.mi->scale_factor(pos, WHITE);
317 factor[BLACK] = ei.mi->scale_factor(pos, BLACK);
319 // Probe the pawn hash table
320 ei.pi = PawnTable[threadID]->get_pawn_info(pos);
321 ei.mgValue += apply_weight(ei.pi->mg_value(), WeightPawnStructureMidgame);
322 ei.egValue += apply_weight(ei.pi->eg_value(), WeightPawnStructureEndgame);
324 // Initialize king attack bitboards and king attack zones for both sides
325 ei.attackedBy[WHITE][KING] = pos.king_attacks(pos.king_square(WHITE));
326 ei.attackedBy[BLACK][KING] = pos.king_attacks(pos.king_square(BLACK));
327 ei.kingZone[WHITE] = ei.attackedBy[BLACK][KING] | (ei.attackedBy[BLACK][KING] >> 8);
328 ei.kingZone[BLACK] = ei.attackedBy[WHITE][KING] | (ei.attackedBy[WHITE][KING] << 8);
330 // Initialize pawn attack bitboards for both sides
331 ei.attackedBy[WHITE][PAWN] = ((pos.pawns(WHITE) << 9) & ~FileABB) | ((pos.pawns(WHITE) << 7) & ~FileHBB);
332 ei.attackedBy[BLACK][PAWN] = ((pos.pawns(BLACK) >> 7) & ~FileABB) | ((pos.pawns(BLACK) >> 9) & ~FileHBB);
333 ei.kingAttackersCount[WHITE] = count_1s_max_15(ei.attackedBy[WHITE][PAWN] & ei.attackedBy[BLACK][KING])/2;
334 ei.kingAttackersCount[BLACK] = count_1s_max_15(ei.attackedBy[BLACK][PAWN] & ei.attackedBy[WHITE][KING])/2;
337 for (Color c = WHITE; c <= BLACK; c++)
340 for (int i = 0; i < pos.knight_count(c); i++)
341 evaluate_knight(pos, pos.knight_list(c, i), c, ei);
344 for (int i = 0; i < pos.bishop_count(c); i++)
345 evaluate_bishop(pos, pos.bishop_list(c, i), c, ei);
348 for (int i = 0; i < pos.rook_count(c); i++)
349 evaluate_rook(pos, pos.rook_list(c, i), c, ei);
352 for(int i = 0; i < pos.queen_count(c); i++)
353 evaluate_queen(pos, pos.queen_list(c, i), c, ei);
355 // Special pattern: trapped bishops on a7/h7/a2/h2
356 Bitboard b = pos.bishops(c) & MaskA7H7[c];
359 Square s = pop_1st_bit(&b);
360 evaluate_trapped_bishop_a7h7(pos, s, c, ei);
363 // Special pattern: trapped bishops on a1/h1/a8/h8 in Chess960:
366 b = pos.bishops(c) & MaskA1H1[c];
369 Square s = pop_1st_bit(&b);
370 evaluate_trapped_bishop_a1h1(pos, s, c, ei);
374 // Sum up all attacked squares
375 ei.attackedBy[c][0] = ei.attackedBy[c][PAWN] | ei.attackedBy[c][KNIGHT]
376 | ei.attackedBy[c][BISHOP] | ei.attackedBy[c][ROOK]
377 | ei.attackedBy[c][QUEEN] | ei.attackedBy[c][KING];
380 // Kings. Kings are evaluated after all other pieces for both sides,
381 // because we need complete attack information for all pieces when computing
382 // the king safety evaluation.
383 for (Color c = WHITE; c <= BLACK; c++)
384 evaluate_king(pos, pos.king_square(c), c, ei);
386 // Evaluate passed pawns. We evaluate passed pawns for both sides at once,
387 // because we need to know which side promotes first in positions where
388 // both sides have an unstoppable passed pawn.
389 if (ei.pi->passed_pawns())
390 evaluate_passed_pawns(pos, ei);
392 Phase phase = pos.game_phase();
394 // Middle-game specific evaluation terms
395 if (phase > PHASE_ENDGAME)
397 // Pawn storms in positions with opposite castling.
398 if ( square_file(pos.king_square(WHITE)) >= FILE_E
399 && square_file(pos.king_square(BLACK)) <= FILE_D)
401 ei.mgValue += ei.pi->queenside_storm_value(WHITE)
402 - ei.pi->kingside_storm_value(BLACK);
404 else if ( square_file(pos.king_square(WHITE)) <= FILE_D
405 && square_file(pos.king_square(BLACK)) >= FILE_E)
407 ei.mgValue += ei.pi->kingside_storm_value(WHITE)
408 - ei.pi->queenside_storm_value(BLACK);
412 ei.mgValue += apply_weight(ei.mgMobility, WeightMobilityMidgame);
413 ei.egValue += apply_weight(ei.egMobility, WeightMobilityEndgame);
415 // If we don't already have an unusual scale factor, check for opposite
416 // colored bishop endgames, and use a lower scale for those:
417 if ( phase < PHASE_MIDGAME
418 && pos.opposite_colored_bishops()
419 && ( (factor[WHITE] == SCALE_FACTOR_NORMAL && ei.egValue > Value(0))
420 || (factor[BLACK] == SCALE_FACTOR_NORMAL && ei.egValue < Value(0))))
422 if (pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK) == 2*BishopValueMidgame)
424 // Only the two bishops
425 if (pos.pawn_count(WHITE) + pos.pawn_count(BLACK) == 1)
427 // KBP vs KB with only a single pawn; almost certainly a draw.
428 if (factor[WHITE] == SCALE_FACTOR_NORMAL)
429 factor[WHITE] = ScaleFactor(8);
430 if (factor[BLACK] == SCALE_FACTOR_NORMAL)
431 factor[BLACK] = ScaleFactor(8);
435 // At least two pawns
436 if (factor[WHITE] == SCALE_FACTOR_NORMAL)
437 factor[WHITE] = ScaleFactor(32);
438 if (factor[BLACK] == SCALE_FACTOR_NORMAL)
439 factor[BLACK] = ScaleFactor(32);
444 // Endgame with opposite-colored bishops, but also other pieces.
445 // Still a bit drawish, but not as drawish as with only the two
447 if (factor[WHITE] == SCALE_FACTOR_NORMAL)
448 factor[WHITE] = ScaleFactor(50);
449 if (factor[BLACK] == SCALE_FACTOR_NORMAL)
450 factor[BLACK] = ScaleFactor(50);
454 // Interpolate between the middle game and the endgame score, and
456 Color stm = pos.side_to_move();
458 Value v = Sign[stm] * scale_by_game_phase(ei.mgValue, ei.egValue, phase, factor);
460 return (ei.mateThreat[stm] == MOVE_NONE ? v : 8 * QueenValueMidgame - v);
464 /// quick_evaluate() does a very approximate evaluation of the current position.
465 /// It currently considers only material and piece square table scores. Perhaps
466 /// we should add scores from the pawn and material hash tables?
468 Value quick_evaluate(const Position &pos) {
470 Value mgValue, egValue;
471 ScaleFactor factor[2] = {SCALE_FACTOR_NORMAL, SCALE_FACTOR_NORMAL};
476 stm = pos.side_to_move();
478 mgValue = pos.mg_value();
479 egValue = pos.eg_value();
480 phase = pos.game_phase();
482 Value value = scale_by_game_phase(mgValue, egValue, phase, factor);
484 return Sign[stm] * value;
488 /// init_eval() initializes various tables used by the evaluation function.
490 void init_eval(int threads) {
492 assert(threads <= THREAD_MAX);
494 for (int i = 0; i < THREAD_MAX; i++)
499 delete MaterialTable[i];
501 MaterialTable[i] = NULL;
505 PawnTable[i] = new PawnInfoTable(PawnTableSize);
506 if (!MaterialTable[i])
507 MaterialTable[i] = new MaterialInfoTable(MaterialTableSize);
510 for (Bitboard b = 0ULL; b < 256ULL; b++)
511 BitCount8Bit[b] = count_1s(b);
515 /// quit_eval() releases heap-allocated memory at program termination.
518 for(int i = 0; i < THREAD_MAX; i++) {
520 delete MaterialTable[i];
525 /// read_weights() reads evaluation weights from the corresponding UCI
528 void read_weights(Color us) {
530 WeightMobilityMidgame = weight_option("Mobility (Middle Game)", WeightMobilityMidgameInternal);
531 WeightMobilityEndgame = weight_option("Mobility (Endgame)", WeightMobilityEndgameInternal);
532 WeightPawnStructureMidgame = weight_option("Pawn Structure (Middle Game)", WeightPawnStructureMidgameInternal);
533 WeightPawnStructureEndgame = weight_option("Pawn Structure (Endgame)", WeightPawnStructureEndgameInternal);
534 WeightPassedPawnsMidgame = weight_option("Passed Pawns (Middle Game)", WeightPassedPawnsMidgameInternal);
535 WeightPassedPawnsEndgame = weight_option("Passed Pawns (Endgame)", WeightPassedPawnsEndgameInternal);
537 Color them = opposite_color(us);
539 WeightKingSafety[us] = weight_option("Cowardice", WeightKingSafetyInternal);
540 WeightKingSafety[them] = weight_option("Aggressiveness", WeightKingOppSafetyInternal);
548 // evaluate_common() computes terms common to all pieces attack
550 int evaluate_common(const Position&p, const Bitboard& b, Color us, EvalInfo& ei,
551 int AttackWeight, const Value* mgBonus, const Value* egBonus,
552 Square s = SQ_NONE, const Value* OutpostBonus = NULL) {
554 Color them = opposite_color(us);
557 if (b & ei.kingZone[us])
559 ei.kingAttackersCount[us]++;
560 ei.kingAttackersWeight[us] += AttackWeight;
561 Bitboard bb = (b & ei.attackedBy[them][KING]);
563 ei.kingZoneAttacksCount[us] += count_1s_max_15(bb);
567 int mob = count_1s_max_15(b & ~p.pieces_of_color(us));
568 ei.mgMobility += Sign[us] * mgBonus[mob];
569 ei.egMobility += Sign[us] * egBonus[mob];
571 // Bishop and Knight outposts
572 if (!OutpostBonus || !p.square_is_weak(s, them))
575 // Initial bonus based on square
577 v = bonus = OutpostBonus[relative_square(us, s)];
579 // Increase bonus if supported by pawn, especially if the opponent has
580 // no minor piece which can exchange the outpost piece
581 if (v && (p.pawn_attacks(them, s) & p.pawns(us)))
584 if ( p.knight_count(them) == 0
585 && (SquaresByColorBB[square_color(s)] & p.bishops(them)) == EmptyBoardBB)
588 ei.mgValue += Sign[us] * bonus;
589 ei.egValue += Sign[us] * bonus;
594 // evaluate_knight() assigns bonuses and penalties to a knight of a given
595 // color on a given square.
597 void evaluate_knight(const Position &p, Square s, Color us, EvalInfo &ei) {
599 Bitboard b = p.knight_attacks(s);
600 ei.attackedBy[us][KNIGHT] |= b;
602 // King attack, mobility and outposts
603 evaluate_common(p, b, us, ei, KnightAttackWeight, MidgameKnightMobilityBonus,
604 EndgameKnightMobilityBonus, s, KnightOutpostBonus);
608 // evaluate_bishop() assigns bonuses and penalties to a bishop of a given
609 // color on a given square.
611 void evaluate_bishop(const Position &p, Square s, Color us, EvalInfo &ei) {
613 Bitboard b = bishop_attacks_bb(s, p.occupied_squares() & ~p.queens(us));
614 ei.attackedBy[us][BISHOP] |= b;
616 // King attack, mobility and outposts
617 evaluate_common(p, b, us, ei, BishopAttackWeight, MidgameBishopMobilityBonus,
618 EndgameBishopMobilityBonus, s, BishopOutpostBonus);
622 // evaluate_rook() assigns bonuses and penalties to a rook of a given
623 // color on a given square.
625 void evaluate_rook(const Position &p, Square s, Color us, EvalInfo &ei) {
627 //Bitboard b = p.rook_attacks(s);
628 Bitboard b = rook_attacks_bb(s, p.occupied_squares() & ~p.rooks_and_queens(us));
629 ei.attackedBy[us][ROOK] |= b;
631 // King attack and mobility
632 int mob = evaluate_common(p, b, us, ei, RookAttackWeight, MidgameRookMobilityBonus,
633 EndgameRookMobilityBonus);
636 Color them = opposite_color(us);
638 if ( relative_rank(us, s) == RANK_7
639 && relative_rank(us, p.king_square(them)) == RANK_8)
641 ei.mgValue += Sign[us] * MidgameRookOn7thBonus;
642 ei.egValue += Sign[us] * EndgameRookOn7thBonus;
645 // Open and half-open files
646 File f = square_file(s);
647 if (ei.pi->file_is_half_open(us, f))
649 if (ei.pi->file_is_half_open(them, f))
651 ei.mgValue += Sign[us] * RookOpenFileBonus;
652 ei.egValue += Sign[us] * RookOpenFileBonus;
656 ei.mgValue += Sign[us] * RookHalfOpenFileBonus;
657 ei.egValue += Sign[us] * RookHalfOpenFileBonus;
661 // Penalize rooks which are trapped inside a king. Penalize more if
662 // king has lost right to castle
663 if (mob > 6 || ei.pi->file_is_half_open(us, f))
666 Square ksq = p.king_square(us);
668 if ( square_file(ksq) >= FILE_E
669 && square_file(s) > square_file(ksq)
670 && (relative_rank(us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
672 // Is there a half-open file between the king and the edge of the board?
673 if (!ei.pi->has_open_file_to_right(us, square_file(ksq)))
674 ei.mgValue -= p.can_castle(us)? Sign[us] * ((TrappedRookPenalty - mob * 16) / 2)
675 : Sign[us] * (TrappedRookPenalty - mob * 16);
677 else if ( square_file(ksq) <= FILE_D
678 && square_file(s) < square_file(ksq)
679 && (relative_rank(us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
681 // Is there a half-open file between the king and the edge of the board?
682 if (!ei.pi->has_open_file_to_left(us, square_file(ksq)))
683 ei.mgValue -= p.can_castle(us)? Sign[us] * ((TrappedRookPenalty - mob * 16) / 2)
684 : Sign[us] * (TrappedRookPenalty - mob * 16);
689 // evaluate_queen() assigns bonuses and penalties to a queen of a given
690 // color on a given square.
692 void evaluate_queen(const Position &p, Square s, Color us, EvalInfo &ei) {
694 Bitboard b = p.queen_attacks(s);
695 ei.attackedBy[us][QUEEN] |= b;
697 // King attack and mobility
698 evaluate_common(p, b, us, ei, QueenAttackWeight, MidgameQueenMobilityBonus,
699 EndgameQueenMobilityBonus);
702 Color them = opposite_color(us);
704 if ( relative_rank(us, s) == RANK_7
705 && relative_rank(us, p.king_square(them)) == RANK_8)
707 ei.mgValue += Sign[us] * MidgameQueenOn7thBonus;
708 ei.egValue += Sign[us] * EndgameQueenOn7thBonus;
713 // evaluate_king() assigns bonuses and penalties to a king of a given
714 // color on a given square.
716 void evaluate_king(const Position &p, Square s, Color us, EvalInfo &ei) {
718 int shelter = 0, sign = Sign[us];
721 if(relative_rank(us, s) <= RANK_4) {
722 Bitboard pawns = p.pawns(us) & this_and_neighboring_files_bb(s);
723 Rank r = square_rank(s);
724 for(int i = 0; i < 3; i++)
725 shelter += count_1s_8bit(pawns >> ((r+(i+1)*sign) * 8)) * (64>>i);
726 ei.mgValue += sign * Value(shelter);
729 // King safety. This is quite complicated, and is almost certainly far
730 // from optimally tuned.
731 Color them = opposite_color(us);
732 if(p.queen_count(them) >= 1 && ei.kingAttackersCount[them] >= 2
733 && p.non_pawn_material(them) >= QueenValueMidgame + RookValueMidgame
734 && ei.kingZoneAttacksCount[them]) {
736 // Is it the attackers turn to move?
737 bool sente = (them == p.side_to_move());
739 // Find the attacked squares around the king which has no defenders
740 // apart from the king itself:
741 Bitboard undefended =
742 ei.attacked_by(them) & ~ei.attacked_by(us, PAWN)
743 & ~ei.attacked_by(us, KNIGHT) & ~ei.attacked_by(us, BISHOP)
744 & ~ei.attacked_by(us, ROOK) & ~ei.attacked_by(us, QUEEN)
745 & ei.attacked_by(us, KING);
746 Bitboard occ = p.occupied_squares(), b, b2;
748 // Initialize the 'attackUnits' variable, which is used later on as an
749 // index to the SafetyTable[] array. The initial is based on the number
750 // and types of the attacking pieces, the number of attacked and
751 // undefended squares around the king, the square of the king, and the
752 // quality of the pawn shelter.
754 Min((ei.kingAttackersCount[them] * ei.kingAttackersWeight[them]) / 2, 25)
755 + (ei.kingZoneAttacksCount[them] + count_1s_max_15(undefended)) * 3
756 + InitKingDanger[relative_square(us, s)] - shelter / 32;
758 // Analyse safe queen contact checks:
759 b = undefended & ei.attacked_by(them, QUEEN) & ~p.pieces_of_color(them);
761 Bitboard attackedByOthers =
762 ei.attacked_by(them, PAWN) | ei.attacked_by(them, KNIGHT)
763 | ei.attacked_by(them, BISHOP) | ei.attacked_by(them, ROOK);
764 b &= attackedByOthers;
766 // The bitboard b now contains the squares available for safe queen
768 int count = count_1s_max_15(b);
769 attackUnits += QueenContactCheckBonus * count * (sente? 2 : 1);
771 // Is there a mate threat?
772 if(QueenContactMates && !p.is_check()) {
773 Bitboard escapeSquares =
774 p.king_attacks(s) & ~p.pieces_of_color(us) & ~attackedByOthers;
776 Square from, to = pop_1st_bit(&b);
778 & ~queen_attacks_bb(to, occ & clear_mask_bb(s)))) {
779 // We have a mate, unless the queen is pinned or there
780 // is an X-ray attack through the queen.
781 for(int i = 0; i < p.queen_count(them); i++) {
782 from = p.queen_list(them, i);
783 if(bit_is_set(p.queen_attacks(from), to)
784 && !bit_is_set(p.pinned_pieces(them), from)
785 && !(rook_attacks_bb(to, occ & clear_mask_bb(from))
786 & p.rooks_and_queens(us))
787 && !(rook_attacks_bb(to, occ & clear_mask_bb(from))
788 & p.rooks_and_queens(us)))
789 ei.mateThreat[them] = make_move(from, to);
797 // Analyse safe rook contact checks:
798 if(RookContactCheckBonus) {
799 b = undefended & ei.attacked_by(them, ROOK) & ~p.pieces_of_color(them);
801 Bitboard attackedByOthers =
802 ei.attacked_by(them, PAWN) | ei.attacked_by(them, KNIGHT)
803 | ei.attacked_by(them, BISHOP) | ei.attacked_by(them, QUEEN);
804 b &= attackedByOthers;
806 int count = count_1s_max_15(b);
807 attackUnits += (RookContactCheckBonus * count * (sente? 2 : 1));
812 // Analyse safe distance checks:
813 if(QueenCheckBonus > 0 || RookCheckBonus > 0) {
814 b = p.rook_attacks(s) & ~p.pieces_of_color(them) & ~ei.attacked_by(us);
817 b2 = b & ei.attacked_by(them, QUEEN);
818 if(b2) attackUnits += QueenCheckBonus * count_1s_max_15(b2);
821 b2 = b & ei.attacked_by(them, ROOK);
822 if(b2) attackUnits += RookCheckBonus * count_1s_max_15(b2);
824 if(QueenCheckBonus > 0 || BishopCheckBonus > 0) {
825 b = p.bishop_attacks(s) & ~p.pieces_of_color(them) & ~ei.attacked_by(us);
827 b2 = b & ei.attacked_by(them, QUEEN);
828 if(b2) attackUnits += QueenCheckBonus * count_1s_max_15(b2);
831 b2 = b & ei.attacked_by(them, BISHOP);
832 if(b2) attackUnits += BishopCheckBonus * count_1s_max_15(b2);
834 if(KnightCheckBonus > 0) {
835 b = p.knight_attacks(s) & ~p.pieces_of_color(them) & ~ei.attacked_by(us);
837 b2 = b & ei.attacked_by(them, KNIGHT);
838 if(b2) attackUnits += KnightCheckBonus * count_1s_max_15(b2);
841 // Analyse discovered checks (only for non-pawns right now, consider
842 // adding pawns later).
843 if(DiscoveredCheckBonus) {
844 b = p.discovered_check_candidates(them) & ~p.pawns();
847 DiscoveredCheckBonus * count_1s_max_15(b) * (sente? 2 : 1);
850 // Has a mate threat been found? We don't do anything here if the
851 // side with the mating move is the side to move, because in that
852 // case the mating side will get a huge bonus at the end of the main
853 // evaluation function instead.
854 if(ei.mateThreat[them] != MOVE_NONE)
855 attackUnits += MateThreatBonus;
857 // Ensure that attackUnits is between 0 and 99, in order to avoid array
858 // out of bounds errors:
859 if(attackUnits < 0) attackUnits = 0;
860 if(attackUnits >= 100) attackUnits = 99;
862 // Finally, extract the king safety score from the SafetyTable[] array.
863 // Add the score to the evaluation, and also to ei.futilityMargin. The
864 // reason for adding the king safety score to the futility margin is
865 // that the king safety scores can sometimes be very big, and that
866 // capturing a single attacking piece can therefore result in a score
867 // change far bigger than the value of the captured piece.
868 Value v = apply_weight(SafetyTable[attackUnits], WeightKingSafety[us]);
869 ei.mgValue -= sign * v;
870 if(us == p.side_to_move())
871 ei.futilityMargin += v;
876 // evaluate_passed_pawns() evaluates the passed pawns for both sides.
878 void evaluate_passed_pawns(const Position &pos, EvalInfo &ei) {
879 bool hasUnstoppable[2] = {false, false};
880 int movesToGo[2] = {100, 100};
882 for(Color us = WHITE; us <= BLACK; us++) {
883 Color them = opposite_color(us);
884 Square ourKingSq = pos.king_square(us);
885 Square theirKingSq = pos.king_square(them);
886 Bitboard b = ei.pi->passed_pawns() & pos.pawns(us), b2, b3, b4;
889 Square s = pop_1st_bit(&b);
890 assert(pos.piece_on(s) == pawn_of_color(us));
891 assert(pos.pawn_is_passed(us, s));
893 int r = int(relative_rank(us, s) - RANK_2);
894 int tr = Max(0, r * (r-1));
895 Square blockSq = s + pawn_push(us);
897 // Base bonus based on rank:
898 Value mbonus = Value(20 * tr);
899 Value ebonus = Value(10 + r * r * 10);
901 // Adjust bonus based on king proximity:
902 ebonus -= Value(square_distance(ourKingSq, blockSq) * 3 * tr);
904 Value(square_distance(ourKingSq, blockSq + pawn_push(us)) * 1 * tr);
905 ebonus += Value(square_distance(theirKingSq, blockSq) * 6 * tr);
907 // If the pawn is free to advance, increase bonus:
908 if(pos.square_is_empty(blockSq)) {
910 b2 = squares_in_front_of(us, s);
911 b3 = b2 & ei.attacked_by(them);
912 b4 = b2 & ei.attacked_by(us);
913 if((b2 & pos.pieces_of_color(them)) == EmptyBoardBB) {
914 // There are no enemy pieces in the pawn's path! Are any of the
915 // squares in the pawn's path attacked by the enemy?
916 if(b3 == EmptyBoardBB)
917 // No enemy attacks, huge bonus!
918 ebonus += Value(tr * ((b2 == b4)? 17 : 15));
920 // OK, there are enemy attacks. Are those squares which are
921 // attacked by the enemy also attacked by us? If yes, big bonus
922 // (but smaller than when there are no enemy attacks), if no,
923 // somewhat smaller bonus.
924 ebonus += Value(tr * (((b3 & b4) == b3)? 13 : 8));
927 // There are some enemy pieces in the pawn's path. While this is
928 // sad, we still assign a moderate bonus if all squares in the path
929 // which are either occupied by or attacked by enemy pieces are
930 // also attacked by us.
931 if(((b3 | (b2 & pos.pieces_of_color(them))) & ~b4) == EmptyBoardBB)
932 ebonus += Value(tr * 6);
934 // At last, add a small bonus when there are no *friendly* pieces
935 // in the pawn's path:
936 if((b2 & pos.pieces_of_color(us)) == EmptyBoardBB)
940 // If the pawn is supported by a friendly pawn, increase bonus.
941 b2 = pos.pawns(us) & neighboring_files_bb(s);
943 ebonus += Value(r * 20);
944 else if(pos.pawn_attacks(them, s) & b2)
945 ebonus += Value(r * 12);
947 // If the other side has only a king, check whether the pawn is
949 if(pos.non_pawn_material(them) == Value(0)) {
953 qsq = relative_square(us, make_square(square_file(s), RANK_8));
954 d = square_distance(s, qsq) - square_distance(theirKingSq, qsq)
955 + ((us == pos.side_to_move())? 0 : 1);
958 int mtg = RANK_8 - relative_rank(us, s);
960 count_1s_max_15(squares_in_front_of(us,s)&pos.occupied_squares());
964 hasUnstoppable[us] = true;
965 movesToGo[us] = Min(movesToGo[us], mtg);
969 // Rook pawns are a special case: They are sometimes worse, and
970 // sometimes better than other passed pawns. It is difficult to find
971 // good rules for determining whether they are good or bad. For now,
972 // we try the following: Increase the value for rook pawns if the
973 // other side has no pieces apart from a knight, and decrease the
974 // value if the other side has a rook or queen.
975 if(square_file(s) == FILE_A || square_file(s) == FILE_H) {
976 if(pos.non_pawn_material(them) == KnightValueMidgame
977 && pos.knight_count(them) == 1)
978 ebonus += ebonus / 4;
979 else if(pos.rooks_and_queens(them))
980 ebonus -= ebonus / 4;
983 // Add the scores for this pawn to the middle game and endgame eval.
984 ei.mgValue += apply_weight(Sign[us] * mbonus, WeightPassedPawnsMidgame);
985 ei.egValue += apply_weight(Sign[us] * ebonus, WeightPassedPawnsEndgame);
989 // Does either side have an unstoppable passed pawn?
990 if(hasUnstoppable[WHITE] && !hasUnstoppable[BLACK])
991 ei.egValue += UnstoppablePawnValue - Value(0x40 * movesToGo[WHITE]);
992 else if(hasUnstoppable[BLACK] && !hasUnstoppable[WHITE])
993 ei.egValue -= UnstoppablePawnValue - Value(0x40 * movesToGo[BLACK]);
994 else if(hasUnstoppable[BLACK] && hasUnstoppable[WHITE]) {
995 // Both sides have unstoppable pawns! Try to find out who queens
996 // first. We begin by transforming 'movesToGo' to the number of
997 // plies until the pawn queens for both sides:
998 movesToGo[WHITE] *= 2;
999 movesToGo[BLACK] *= 2;
1000 movesToGo[pos.side_to_move()]--;
1002 // If one side queens at least three plies before the other, that
1004 if(movesToGo[WHITE] <= movesToGo[BLACK] - 3)
1005 ei.egValue += UnstoppablePawnValue - Value(0x40 * (movesToGo[WHITE]/2));
1006 else if(movesToGo[BLACK] <= movesToGo[WHITE] - 3)
1007 ei.egValue -= UnstoppablePawnValue - Value(0x40 * (movesToGo[BLACK]/2));
1009 // We could also add some rules about the situation when one side
1010 // queens exactly one ply before the other: Does the first queen
1011 // check the opponent's king, or attack the opponent's queening square?
1012 // This is slightly tricky to get right, because it is possible that
1013 // the opponent's king has moved somewhere before the first pawn queens.
1018 // evaluate_trapped_bishop_a7h7() determines whether a bishop on a7/h7
1019 // (a2/h2 for black) is trapped by enemy pawns, and assigns a penalty
1022 void evaluate_trapped_bishop_a7h7(const Position &pos, Square s, Color us,
1025 assert(square_is_ok(s));
1026 assert(pos.piece_on(s) == bishop_of_color(us));
1028 Square b6 = relative_square(us, (square_file(s) == FILE_A) ? SQ_B6 : SQ_G6);
1029 Square b8 = relative_square(us, (square_file(s) == FILE_A) ? SQ_B8 : SQ_G8);
1031 if ( pos.piece_on(b6) == pawn_of_color(opposite_color(us))
1032 && pos.see(s, b6) < 0
1033 && pos.see(s, b8) < 0)
1035 ei.mgValue -= Sign[us] * TrappedBishopA7H7Penalty;
1036 ei.egValue -= Sign[us] * TrappedBishopA7H7Penalty;
1041 // evaluate_trapped_bishop_a1h1() determines whether a bishop on a1/h1
1042 // (a8/h8 for black) is trapped by a friendly pawn on b2/g2 (b7/g7 for
1043 // black), and assigns a penalty if it is. This pattern can obviously
1044 // only occur in Chess960 games.
1046 void evaluate_trapped_bishop_a1h1(const Position &pos, Square s, Color us,
1048 Piece pawn = pawn_of_color(us);
1052 assert(square_is_ok(s));
1053 assert(pos.piece_on(s) == bishop_of_color(us));
1055 if(square_file(s) == FILE_A) {
1056 b2 = relative_square(us, SQ_B2);
1057 b3 = relative_square(us, SQ_B3);
1058 c3 = relative_square(us, SQ_C3);
1061 b2 = relative_square(us, SQ_G2);
1062 b3 = relative_square(us, SQ_G3);
1063 c3 = relative_square(us, SQ_F3);
1066 if(pos.piece_on(b2) == pawn) {
1069 if(!pos.square_is_empty(b3))
1070 penalty = 2*TrappedBishopA1H1Penalty;
1071 else if(pos.piece_on(c3) == pawn)
1072 penalty = TrappedBishopA1H1Penalty;
1074 penalty = TrappedBishopA1H1Penalty / 2;
1076 ei.mgValue -= Sign[us] * penalty;
1077 ei.egValue -= Sign[us] * penalty;
1083 // apply_weight applies an evaluation weight to a value.
1085 inline Value apply_weight(Value v, int w) {
1086 return (v*w) / 0x100;
1090 // scale_by_game_phase interpolates between a middle game and an endgame
1091 // score, based on game phase. It also scales the return value by a
1092 // ScaleFactor array.
1094 Value scale_by_game_phase(Value mv, Value ev, Phase ph, ScaleFactor sf[]) {
1096 assert(mv > -VALUE_INFINITE && mv < VALUE_INFINITE);
1097 assert(ev > -VALUE_INFINITE && ev < VALUE_INFINITE);
1098 assert(ph >= PHASE_ENDGAME && ph <= PHASE_MIDGAME);
1100 ev = apply_scale_factor(ev, sf[(ev > Value(0) ? WHITE : BLACK)]);
1102 // Linearized sigmoid interpolator
1104 sph -= (64 - sph) / 4;
1105 sph = Min(PHASE_MIDGAME, Max(PHASE_ENDGAME, sph));
1107 Value result = Value(int((mv * sph + ev * (128 - sph)) / 128));
1109 return Value(int(result) & ~(GrainSize - 1));
1113 // count_1s_8bit() counts the number of nonzero bits in the 8 least
1114 // significant bits of a Bitboard. This function is used by the king
1115 // shield evaluation.
1117 int count_1s_8bit(Bitboard b) {
1118 return int(BitCount8Bit[b & 0xFF]);
1122 // compute_weight() computes the value of an evaluation weight, by combining
1123 // an UCI-configurable weight with an internal weight.
1125 int compute_weight(int uciWeight, int internalWeight) {
1126 uciWeight = (uciWeight * 0x100) / 100;
1127 return (uciWeight * internalWeight) / 0x100;
1131 // helper used in read_weights()
1132 int weight_option(const std::string& opt, int weight) {
1134 return compute_weight(get_option_value_int(opt), weight);
1138 // init_safety() initizes the king safety evaluation, based on UCI
1139 // parameters. It is called from read_weights().
1141 void init_safety() {
1143 QueenContactCheckBonus = get_option_value_int("Queen Contact Check Bonus");
1144 RookContactCheckBonus = get_option_value_int("Rook Contact Check Bonus");
1145 QueenCheckBonus = get_option_value_int("Queen Check Bonus");
1146 RookCheckBonus = get_option_value_int("Rook Check Bonus");
1147 BishopCheckBonus = get_option_value_int("Bishop Check Bonus");
1148 KnightCheckBonus = get_option_value_int("Knight Check Bonus");
1149 DiscoveredCheckBonus = get_option_value_int("Discovered Check Bonus");
1150 MateThreatBonus = get_option_value_int("Mate Threat Bonus");
1152 int maxSlope = get_option_value_int("King Safety Max Slope");
1153 int peak = get_option_value_int("King Safety Max Value") * 256 / 100;
1154 double a = get_option_value_int("King Safety Coefficient") / 100.0;
1155 double b = get_option_value_int("King Safety X Intercept");
1156 bool quad = (get_option_value_string("King Safety Curve") == "Quadratic");
1157 bool linear = (get_option_value_string("King Safety Curve") == "Linear");
1159 for (int i = 0; i < 100; i++)
1162 SafetyTable[i] = Value(0);
1164 SafetyTable[i] = Value((int)(a * (i - b) * (i - b)));
1166 SafetyTable[i] = Value((int)(100 * a * (i - b)));
1169 for (int i = 0; i < 100; i++)
1171 if (SafetyTable[i+1] - SafetyTable[i] > maxSlope)
1172 for (int j = i + 1; j < 100; j++)
1173 SafetyTable[j] = SafetyTable[j-1] + Value(maxSlope);
1175 if (SafetyTable[i] > Value(peak))
1176 SafetyTable[i] = Value(peak);