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, const 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))))
424 // Only the two bishops ?
425 if ( pos.non_pawn_material(WHITE) == BishopValueMidgame
426 && pos.non_pawn_material(BLACK) == BishopValueMidgame)
428 // Check for KBP vs KB with only a single pawn that is almost
429 // certainly a draw or at least two pawns.
430 bool one_pawn = (pos.pawn_count(WHITE) + pos.pawn_count(BLACK) == 1);
431 sf = one_pawn ? ScaleFactor(8) : ScaleFactor(32);
434 // Endgame with opposite-colored bishops, but also other pieces. Still
435 // a bit drawish, but not as drawish as with only the two bishops.
436 sf = ScaleFactor(50);
438 if (factor[WHITE] == SCALE_FACTOR_NORMAL)
440 if (factor[BLACK] == SCALE_FACTOR_NORMAL)
444 // Interpolate between the middle game and the endgame score, and
446 Color stm = pos.side_to_move();
448 Value v = Sign[stm] * scale_by_game_phase(ei.mgValue, ei.egValue, phase, factor);
450 return (ei.mateThreat[stm] == MOVE_NONE ? v : 8 * QueenValueMidgame - v);
454 /// quick_evaluate() does a very approximate evaluation of the current position.
455 /// It currently considers only material and piece square table scores. Perhaps
456 /// we should add scores from the pawn and material hash tables?
458 Value quick_evaluate(const Position &pos) {
463 ScaleFactor sf[2] = {SCALE_FACTOR_NORMAL, SCALE_FACTOR_NORMAL};
465 Value mgv = pos.mg_value();
466 Value egv = pos.eg_value();
467 Phase ph = pos.game_phase();
468 Color stm = pos.side_to_move();
470 return Sign[stm] * scale_by_game_phase(mgv, egv, ph, sf);
474 /// init_eval() initializes various tables used by the evaluation function.
476 void init_eval(int threads) {
478 assert(threads <= THREAD_MAX);
480 for (int i = 0; i < THREAD_MAX; i++)
485 delete MaterialTable[i];
487 MaterialTable[i] = NULL;
491 PawnTable[i] = new PawnInfoTable(PawnTableSize);
492 if (!MaterialTable[i])
493 MaterialTable[i] = new MaterialInfoTable(MaterialTableSize);
496 for (Bitboard b = 0ULL; b < 256ULL; b++)
497 BitCount8Bit[b] = count_1s(b);
501 /// quit_eval() releases heap-allocated memory at program termination.
505 for (int i = 0; i < THREAD_MAX; i++)
508 delete MaterialTable[i];
513 /// read_weights() reads evaluation weights from the corresponding UCI
516 void read_weights(Color us) {
518 WeightMobilityMidgame = weight_option("Mobility (Middle Game)", WeightMobilityMidgameInternal);
519 WeightMobilityEndgame = weight_option("Mobility (Endgame)", WeightMobilityEndgameInternal);
520 WeightPawnStructureMidgame = weight_option("Pawn Structure (Middle Game)", WeightPawnStructureMidgameInternal);
521 WeightPawnStructureEndgame = weight_option("Pawn Structure (Endgame)", WeightPawnStructureEndgameInternal);
522 WeightPassedPawnsMidgame = weight_option("Passed Pawns (Middle Game)", WeightPassedPawnsMidgameInternal);
523 WeightPassedPawnsEndgame = weight_option("Passed Pawns (Endgame)", WeightPassedPawnsEndgameInternal);
525 Color them = opposite_color(us);
527 WeightKingSafety[us] = weight_option("Cowardice", WeightKingSafetyInternal);
528 WeightKingSafety[them] = weight_option("Aggressiveness", WeightKingOppSafetyInternal);
536 // evaluate_common() computes terms common to all pieces attack
538 int evaluate_common(const Position&p, const Bitboard& b, Color us, EvalInfo& ei,
539 int AttackWeight, const Value* mgBonus, const Value* egBonus,
540 Square s = SQ_NONE, const Value* OutpostBonus = NULL) {
542 Color them = opposite_color(us);
545 if (b & ei.kingZone[us])
547 ei.kingAttackersCount[us]++;
548 ei.kingAttackersWeight[us] += AttackWeight;
549 Bitboard bb = (b & ei.attackedBy[them][KING]);
551 ei.kingAdjacentZoneAttacksCount[us] += count_1s_max_15(bb);
555 int mob = count_1s_max_15(b & ~p.pieces_of_color(us));
556 ei.mgMobility += Sign[us] * mgBonus[mob];
557 ei.egMobility += Sign[us] * egBonus[mob];
559 // Bishop and Knight outposts
560 if (!OutpostBonus || !p.square_is_weak(s, them))
563 // Initial bonus based on square
565 v = bonus = OutpostBonus[relative_square(us, s)];
567 // Increase bonus if supported by pawn, especially if the opponent has
568 // no minor piece which can exchange the outpost piece
569 if (v && (p.pawn_attacks(them, s) & p.pawns(us)))
572 if ( p.knight_count(them) == 0
573 && (SquaresByColorBB[square_color(s)] & p.bishops(them)) == EmptyBoardBB)
576 ei.mgValue += Sign[us] * bonus;
577 ei.egValue += Sign[us] * bonus;
582 // evaluate_knight() assigns bonuses and penalties to a knight of a given
583 // color on a given square.
585 void evaluate_knight(const Position &p, Square s, Color us, EvalInfo &ei) {
587 Bitboard b = p.knight_attacks(s);
588 ei.attackedBy[us][KNIGHT] |= b;
590 // King attack, mobility and outposts
591 evaluate_common(p, b, us, ei, KnightAttackWeight, MidgameKnightMobilityBonus,
592 EndgameKnightMobilityBonus, s, KnightOutpostBonus);
596 // evaluate_bishop() assigns bonuses and penalties to a bishop of a given
597 // color on a given square.
599 void evaluate_bishop(const Position &p, Square s, Color us, EvalInfo &ei) {
601 Bitboard b = bishop_attacks_bb(s, p.occupied_squares() & ~p.queens(us));
602 ei.attackedBy[us][BISHOP] |= b;
604 // King attack, mobility and outposts
605 evaluate_common(p, b, us, ei, BishopAttackWeight, MidgameBishopMobilityBonus,
606 EndgameBishopMobilityBonus, s, BishopOutpostBonus);
610 // evaluate_rook() assigns bonuses and penalties to a rook of a given
611 // color on a given square.
613 void evaluate_rook(const Position &p, Square s, Color us, EvalInfo &ei) {
615 //Bitboard b = p.rook_attacks(s);
616 Bitboard b = rook_attacks_bb(s, p.occupied_squares() & ~p.rooks_and_queens(us));
617 ei.attackedBy[us][ROOK] |= b;
619 // King attack and mobility
620 int mob = evaluate_common(p, b, us, ei, RookAttackWeight, MidgameRookMobilityBonus,
621 EndgameRookMobilityBonus);
624 Color them = opposite_color(us);
626 if ( relative_rank(us, s) == RANK_7
627 && relative_rank(us, p.king_square(them)) == RANK_8)
629 ei.mgValue += Sign[us] * MidgameRookOn7thBonus;
630 ei.egValue += Sign[us] * EndgameRookOn7thBonus;
633 // Open and half-open files
634 File f = square_file(s);
635 if (ei.pi->file_is_half_open(us, f))
637 if (ei.pi->file_is_half_open(them, f))
639 ei.mgValue += Sign[us] * RookOpenFileBonus;
640 ei.egValue += Sign[us] * RookOpenFileBonus;
644 ei.mgValue += Sign[us] * RookHalfOpenFileBonus;
645 ei.egValue += Sign[us] * RookHalfOpenFileBonus;
649 // Penalize rooks which are trapped inside a king. Penalize more if
650 // king has lost right to castle
651 if (mob > 6 || ei.pi->file_is_half_open(us, f))
654 Square ksq = p.king_square(us);
656 if ( square_file(ksq) >= FILE_E
657 && square_file(s) > square_file(ksq)
658 && (relative_rank(us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
660 // Is there a half-open file between the king and the edge of the board?
661 if (!ei.pi->has_open_file_to_right(us, square_file(ksq)))
662 ei.mgValue -= p.can_castle(us)? Sign[us] * ((TrappedRookPenalty - mob * 16) / 2)
663 : Sign[us] * (TrappedRookPenalty - mob * 16);
665 else if ( square_file(ksq) <= FILE_D
666 && square_file(s) < square_file(ksq)
667 && (relative_rank(us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
669 // Is there a half-open file between the king and the edge of the board?
670 if (!ei.pi->has_open_file_to_left(us, square_file(ksq)))
671 ei.mgValue -= p.can_castle(us)? Sign[us] * ((TrappedRookPenalty - mob * 16) / 2)
672 : Sign[us] * (TrappedRookPenalty - mob * 16);
677 // evaluate_queen() assigns bonuses and penalties to a queen of a given
678 // color on a given square.
680 void evaluate_queen(const Position &p, Square s, Color us, EvalInfo &ei) {
682 Bitboard b = p.queen_attacks(s);
683 ei.attackedBy[us][QUEEN] |= b;
685 // King attack and mobility
686 evaluate_common(p, b, us, ei, QueenAttackWeight, MidgameQueenMobilityBonus,
687 EndgameQueenMobilityBonus);
690 Color them = opposite_color(us);
692 if ( relative_rank(us, s) == RANK_7
693 && relative_rank(us, p.king_square(them)) == RANK_8)
695 ei.mgValue += Sign[us] * MidgameQueenOn7thBonus;
696 ei.egValue += Sign[us] * EndgameQueenOn7thBonus;
701 // evaluate_king() assigns bonuses and penalties to a king of a given
702 // color on a given square.
704 void evaluate_king(const Position &p, Square s, Color us, EvalInfo &ei) {
706 int shelter = 0, sign = Sign[us];
709 if(relative_rank(us, s) <= RANK_4) {
710 Bitboard pawns = p.pawns(us) & this_and_neighboring_files_bb(s);
711 Rank r = square_rank(s);
712 for(int i = 0; i < 3; i++)
713 shelter += count_1s_8bit(pawns >> ((r+(i+1)*sign) * 8)) * (64>>i);
714 ei.mgValue += sign * Value(shelter);
717 // King safety. This is quite complicated, and is almost certainly far
718 // from optimally tuned.
719 Color them = opposite_color(us);
720 if(p.queen_count(them) >= 1 && ei.kingAttackersCount[them] >= 2
721 && p.non_pawn_material(them) >= QueenValueMidgame + RookValueMidgame
722 && ei.kingAdjacentZoneAttacksCount[them]) {
724 // Is it the attackers turn to move?
725 bool sente = (them == p.side_to_move());
727 // Find the attacked squares around the king which has no defenders
728 // apart from the king itself:
729 Bitboard undefended =
730 ei.attacked_by(them) & ~ei.attacked_by(us, PAWN)
731 & ~ei.attacked_by(us, KNIGHT) & ~ei.attacked_by(us, BISHOP)
732 & ~ei.attacked_by(us, ROOK) & ~ei.attacked_by(us, QUEEN)
733 & ei.attacked_by(us, KING);
734 Bitboard occ = p.occupied_squares(), b, b2;
736 // Initialize the 'attackUnits' variable, which is used later on as an
737 // index to the SafetyTable[] array. The initial is based on the number
738 // and types of the attacking pieces, the number of attacked and
739 // undefended squares around the king, the square of the king, and the
740 // quality of the pawn shelter.
742 Min((ei.kingAttackersCount[them] * ei.kingAttackersWeight[them]) / 2, 25)
743 + (ei.kingAdjacentZoneAttacksCount[them] + count_1s_max_15(undefended)) * 3
744 + InitKingDanger[relative_square(us, s)] - shelter / 32;
746 // Analyse safe queen contact checks:
747 b = undefended & ei.attacked_by(them, QUEEN) & ~p.pieces_of_color(them);
749 Bitboard attackedByOthers =
750 ei.attacked_by(them, PAWN) | ei.attacked_by(them, KNIGHT)
751 | ei.attacked_by(them, BISHOP) | ei.attacked_by(them, ROOK);
752 b &= attackedByOthers;
754 // The bitboard b now contains the squares available for safe queen
756 int count = count_1s_max_15(b);
757 attackUnits += QueenContactCheckBonus * count * (sente? 2 : 1);
759 // Is there a mate threat?
760 if(QueenContactMates && !p.is_check()) {
761 Bitboard escapeSquares =
762 p.king_attacks(s) & ~p.pieces_of_color(us) & ~attackedByOthers;
764 Square from, to = pop_1st_bit(&b);
766 & ~queen_attacks_bb(to, occ & clear_mask_bb(s)))) {
767 // We have a mate, unless the queen is pinned or there
768 // is an X-ray attack through the queen.
769 for(int i = 0; i < p.queen_count(them); i++) {
770 from = p.queen_list(them, i);
771 if(bit_is_set(p.queen_attacks(from), to)
772 && !bit_is_set(p.pinned_pieces(them), from)
773 && !(rook_attacks_bb(to, occ & clear_mask_bb(from))
774 & p.rooks_and_queens(us))
775 && !(rook_attacks_bb(to, occ & clear_mask_bb(from))
776 & p.rooks_and_queens(us)))
777 ei.mateThreat[them] = make_move(from, to);
785 // Analyse safe rook contact checks:
786 if(RookContactCheckBonus) {
787 b = undefended & ei.attacked_by(them, ROOK) & ~p.pieces_of_color(them);
789 Bitboard attackedByOthers =
790 ei.attacked_by(them, PAWN) | ei.attacked_by(them, KNIGHT)
791 | ei.attacked_by(them, BISHOP) | ei.attacked_by(them, QUEEN);
792 b &= attackedByOthers;
794 int count = count_1s_max_15(b);
795 attackUnits += (RookContactCheckBonus * count * (sente? 2 : 1));
800 // Analyse safe distance checks:
801 if(QueenCheckBonus > 0 || RookCheckBonus > 0) {
802 b = p.rook_attacks(s) & ~p.pieces_of_color(them) & ~ei.attacked_by(us);
805 b2 = b & ei.attacked_by(them, QUEEN);
806 if(b2) attackUnits += QueenCheckBonus * count_1s_max_15(b2);
809 b2 = b & ei.attacked_by(them, ROOK);
810 if(b2) attackUnits += RookCheckBonus * count_1s_max_15(b2);
812 if(QueenCheckBonus > 0 || BishopCheckBonus > 0) {
813 b = p.bishop_attacks(s) & ~p.pieces_of_color(them) & ~ei.attacked_by(us);
815 b2 = b & ei.attacked_by(them, QUEEN);
816 if(b2) attackUnits += QueenCheckBonus * count_1s_max_15(b2);
819 b2 = b & ei.attacked_by(them, BISHOP);
820 if(b2) attackUnits += BishopCheckBonus * count_1s_max_15(b2);
822 if(KnightCheckBonus > 0) {
823 b = p.knight_attacks(s) & ~p.pieces_of_color(them) & ~ei.attacked_by(us);
825 b2 = b & ei.attacked_by(them, KNIGHT);
826 if(b2) attackUnits += KnightCheckBonus * count_1s_max_15(b2);
829 // Analyse discovered checks (only for non-pawns right now, consider
830 // adding pawns later).
831 if(DiscoveredCheckBonus) {
832 b = p.discovered_check_candidates(them) & ~p.pawns();
835 DiscoveredCheckBonus * count_1s_max_15(b) * (sente? 2 : 1);
838 // Has a mate threat been found? We don't do anything here if the
839 // side with the mating move is the side to move, because in that
840 // case the mating side will get a huge bonus at the end of the main
841 // evaluation function instead.
842 if(ei.mateThreat[them] != MOVE_NONE)
843 attackUnits += MateThreatBonus;
845 // Ensure that attackUnits is between 0 and 99, in order to avoid array
846 // out of bounds errors:
847 if(attackUnits < 0) attackUnits = 0;
848 if(attackUnits >= 100) attackUnits = 99;
850 // Finally, extract the king safety score from the SafetyTable[] array.
851 // Add the score to the evaluation, and also to ei.futilityMargin. The
852 // reason for adding the king safety score to the futility margin is
853 // that the king safety scores can sometimes be very big, and that
854 // capturing a single attacking piece can therefore result in a score
855 // change far bigger than the value of the captured piece.
856 Value v = apply_weight(SafetyTable[attackUnits], WeightKingSafety[us]);
857 ei.mgValue -= sign * v;
858 if(us == p.side_to_move())
859 ei.futilityMargin += v;
864 // evaluate_passed_pawns() evaluates the passed pawns for both sides.
866 void evaluate_passed_pawns(const Position &pos, EvalInfo &ei) {
867 bool hasUnstoppable[2] = {false, false};
868 int movesToGo[2] = {100, 100};
870 for(Color us = WHITE; us <= BLACK; us++) {
871 Color them = opposite_color(us);
872 Square ourKingSq = pos.king_square(us);
873 Square theirKingSq = pos.king_square(them);
874 Bitboard b = ei.pi->passed_pawns() & pos.pawns(us), b2, b3, b4;
877 Square s = pop_1st_bit(&b);
878 assert(pos.piece_on(s) == pawn_of_color(us));
879 assert(pos.pawn_is_passed(us, s));
881 int r = int(relative_rank(us, s) - RANK_2);
882 int tr = Max(0, r * (r-1));
883 Square blockSq = s + pawn_push(us);
885 // Base bonus based on rank:
886 Value mbonus = Value(20 * tr);
887 Value ebonus = Value(10 + r * r * 10);
889 // Adjust bonus based on king proximity:
890 ebonus -= Value(square_distance(ourKingSq, blockSq) * 3 * tr);
892 Value(square_distance(ourKingSq, blockSq + pawn_push(us)) * 1 * tr);
893 ebonus += Value(square_distance(theirKingSq, blockSq) * 6 * tr);
895 // If the pawn is free to advance, increase bonus:
896 if(pos.square_is_empty(blockSq)) {
898 b2 = squares_in_front_of(us, s);
899 b3 = b2 & ei.attacked_by(them);
900 b4 = b2 & ei.attacked_by(us);
901 if((b2 & pos.pieces_of_color(them)) == EmptyBoardBB) {
902 // There are no enemy pieces in the pawn's path! Are any of the
903 // squares in the pawn's path attacked by the enemy?
904 if(b3 == EmptyBoardBB)
905 // No enemy attacks, huge bonus!
906 ebonus += Value(tr * ((b2 == b4)? 17 : 15));
908 // OK, there are enemy attacks. Are those squares which are
909 // attacked by the enemy also attacked by us? If yes, big bonus
910 // (but smaller than when there are no enemy attacks), if no,
911 // somewhat smaller bonus.
912 ebonus += Value(tr * (((b3 & b4) == b3)? 13 : 8));
915 // There are some enemy pieces in the pawn's path. While this is
916 // sad, we still assign a moderate bonus if all squares in the path
917 // which are either occupied by or attacked by enemy pieces are
918 // also attacked by us.
919 if(((b3 | (b2 & pos.pieces_of_color(them))) & ~b4) == EmptyBoardBB)
920 ebonus += Value(tr * 6);
922 // At last, add a small bonus when there are no *friendly* pieces
923 // in the pawn's path:
924 if((b2 & pos.pieces_of_color(us)) == EmptyBoardBB)
928 // If the pawn is supported by a friendly pawn, increase bonus.
929 b2 = pos.pawns(us) & neighboring_files_bb(s);
931 ebonus += Value(r * 20);
932 else if(pos.pawn_attacks(them, s) & b2)
933 ebonus += Value(r * 12);
935 // If the other side has only a king, check whether the pawn is
937 if(pos.non_pawn_material(them) == Value(0)) {
941 qsq = relative_square(us, make_square(square_file(s), RANK_8));
942 d = square_distance(s, qsq) - square_distance(theirKingSq, qsq)
943 + ((us == pos.side_to_move())? 0 : 1);
946 int mtg = RANK_8 - relative_rank(us, s);
948 count_1s_max_15(squares_in_front_of(us,s)&pos.occupied_squares());
952 hasUnstoppable[us] = true;
953 movesToGo[us] = Min(movesToGo[us], mtg);
957 // Rook pawns are a special case: They are sometimes worse, and
958 // sometimes better than other passed pawns. It is difficult to find
959 // good rules for determining whether they are good or bad. For now,
960 // we try the following: Increase the value for rook pawns if the
961 // other side has no pieces apart from a knight, and decrease the
962 // value if the other side has a rook or queen.
963 if(square_file(s) == FILE_A || square_file(s) == FILE_H) {
964 if(pos.non_pawn_material(them) == KnightValueMidgame
965 && pos.knight_count(them) == 1)
966 ebonus += ebonus / 4;
967 else if(pos.rooks_and_queens(them))
968 ebonus -= ebonus / 4;
971 // Add the scores for this pawn to the middle game and endgame eval.
972 ei.mgValue += apply_weight(Sign[us] * mbonus, WeightPassedPawnsMidgame);
973 ei.egValue += apply_weight(Sign[us] * ebonus, WeightPassedPawnsEndgame);
977 // Does either side have an unstoppable passed pawn?
978 if(hasUnstoppable[WHITE] && !hasUnstoppable[BLACK])
979 ei.egValue += UnstoppablePawnValue - Value(0x40 * movesToGo[WHITE]);
980 else if(hasUnstoppable[BLACK] && !hasUnstoppable[WHITE])
981 ei.egValue -= UnstoppablePawnValue - Value(0x40 * movesToGo[BLACK]);
982 else if(hasUnstoppable[BLACK] && hasUnstoppable[WHITE]) {
983 // Both sides have unstoppable pawns! Try to find out who queens
984 // first. We begin by transforming 'movesToGo' to the number of
985 // plies until the pawn queens for both sides:
986 movesToGo[WHITE] *= 2;
987 movesToGo[BLACK] *= 2;
988 movesToGo[pos.side_to_move()]--;
990 // If one side queens at least three plies before the other, that
992 if(movesToGo[WHITE] <= movesToGo[BLACK] - 3)
993 ei.egValue += UnstoppablePawnValue - Value(0x40 * (movesToGo[WHITE]/2));
994 else if(movesToGo[BLACK] <= movesToGo[WHITE] - 3)
995 ei.egValue -= UnstoppablePawnValue - Value(0x40 * (movesToGo[BLACK]/2));
997 // We could also add some rules about the situation when one side
998 // queens exactly one ply before the other: Does the first queen
999 // check the opponent's king, or attack the opponent's queening square?
1000 // This is slightly tricky to get right, because it is possible that
1001 // the opponent's king has moved somewhere before the first pawn queens.
1006 // evaluate_trapped_bishop_a7h7() determines whether a bishop on a7/h7
1007 // (a2/h2 for black) is trapped by enemy pawns, and assigns a penalty
1010 void evaluate_trapped_bishop_a7h7(const Position &pos, Square s, Color us,
1013 assert(square_is_ok(s));
1014 assert(pos.piece_on(s) == bishop_of_color(us));
1016 Square b6 = relative_square(us, (square_file(s) == FILE_A) ? SQ_B6 : SQ_G6);
1017 Square b8 = relative_square(us, (square_file(s) == FILE_A) ? SQ_B8 : SQ_G8);
1019 if ( pos.piece_on(b6) == pawn_of_color(opposite_color(us))
1020 && pos.see(s, b6) < 0
1021 && pos.see(s, b8) < 0)
1023 ei.mgValue -= Sign[us] * TrappedBishopA7H7Penalty;
1024 ei.egValue -= Sign[us] * TrappedBishopA7H7Penalty;
1029 // evaluate_trapped_bishop_a1h1() determines whether a bishop on a1/h1
1030 // (a8/h8 for black) is trapped by a friendly pawn on b2/g2 (b7/g7 for
1031 // black), and assigns a penalty if it is. This pattern can obviously
1032 // only occur in Chess960 games.
1034 void evaluate_trapped_bishop_a1h1(const Position &pos, Square s, Color us,
1036 Piece pawn = pawn_of_color(us);
1040 assert(square_is_ok(s));
1041 assert(pos.piece_on(s) == bishop_of_color(us));
1043 if(square_file(s) == FILE_A) {
1044 b2 = relative_square(us, SQ_B2);
1045 b3 = relative_square(us, SQ_B3);
1046 c3 = relative_square(us, SQ_C3);
1049 b2 = relative_square(us, SQ_G2);
1050 b3 = relative_square(us, SQ_G3);
1051 c3 = relative_square(us, SQ_F3);
1054 if(pos.piece_on(b2) == pawn) {
1057 if(!pos.square_is_empty(b3))
1058 penalty = 2*TrappedBishopA1H1Penalty;
1059 else if(pos.piece_on(c3) == pawn)
1060 penalty = TrappedBishopA1H1Penalty;
1062 penalty = TrappedBishopA1H1Penalty / 2;
1064 ei.mgValue -= Sign[us] * penalty;
1065 ei.egValue -= Sign[us] * penalty;
1071 // apply_weight applies an evaluation weight to a value.
1073 inline Value apply_weight(Value v, int w) {
1074 return (v*w) / 0x100;
1078 // scale_by_game_phase interpolates between a middle game and an endgame
1079 // score, based on game phase. It also scales the return value by a
1080 // ScaleFactor array.
1082 Value scale_by_game_phase(Value mv, Value ev, Phase ph, const ScaleFactor sf[]) {
1084 assert(mv > -VALUE_INFINITE && mv < VALUE_INFINITE);
1085 assert(ev > -VALUE_INFINITE && ev < VALUE_INFINITE);
1086 assert(ph >= PHASE_ENDGAME && ph <= PHASE_MIDGAME);
1088 ev = apply_scale_factor(ev, sf[(ev > Value(0) ? WHITE : BLACK)]);
1090 // Linearized sigmoid interpolator
1092 sph -= (64 - sph) / 4;
1093 sph = Min(PHASE_MIDGAME, Max(PHASE_ENDGAME, sph));
1095 Value result = Value(int((mv * sph + ev * (128 - sph)) / 128));
1097 return Value(int(result) & ~(GrainSize - 1));
1101 // count_1s_8bit() counts the number of nonzero bits in the 8 least
1102 // significant bits of a Bitboard. This function is used by the king
1103 // shield evaluation.
1105 int count_1s_8bit(Bitboard b) {
1106 return int(BitCount8Bit[b & 0xFF]);
1110 // compute_weight() computes the value of an evaluation weight, by combining
1111 // an UCI-configurable weight with an internal weight.
1113 int compute_weight(int uciWeight, int internalWeight) {
1114 uciWeight = (uciWeight * 0x100) / 100;
1115 return (uciWeight * internalWeight) / 0x100;
1119 // helper used in read_weights()
1120 int weight_option(const std::string& opt, int weight) {
1122 return compute_weight(get_option_value_int(opt), weight);
1126 // init_safety() initizes the king safety evaluation, based on UCI
1127 // parameters. It is called from read_weights().
1129 void init_safety() {
1131 QueenContactCheckBonus = get_option_value_int("Queen Contact Check Bonus");
1132 RookContactCheckBonus = get_option_value_int("Rook Contact Check Bonus");
1133 QueenCheckBonus = get_option_value_int("Queen Check Bonus");
1134 RookCheckBonus = get_option_value_int("Rook Check Bonus");
1135 BishopCheckBonus = get_option_value_int("Bishop Check Bonus");
1136 KnightCheckBonus = get_option_value_int("Knight Check Bonus");
1137 DiscoveredCheckBonus = get_option_value_int("Discovered Check Bonus");
1138 MateThreatBonus = get_option_value_int("Mate Threat Bonus");
1140 int maxSlope = get_option_value_int("King Safety Max Slope");
1141 int peak = get_option_value_int("King Safety Max Value") * 256 / 100;
1142 double a = get_option_value_int("King Safety Coefficient") / 100.0;
1143 double b = get_option_value_int("King Safety X Intercept");
1144 bool quad = (get_option_value_string("King Safety Curve") == "Quadratic");
1145 bool linear = (get_option_value_string("King Safety Curve") == "Linear");
1147 for (int i = 0; i < 100; i++)
1150 SafetyTable[i] = Value(0);
1152 SafetyTable[i] = Value((int)(a * (i - b) * (i - b)));
1154 SafetyTable[i] = Value((int)(100 * a * (i - b)));
1157 for (int i = 0; i < 100; i++)
1159 if (SafetyTable[i+1] - SafetyTable[i] > maxSlope)
1160 for (int j = i + 1; j < 100; j++)
1161 SafetyTable[j] = SafetyTable[j-1] + Value(maxSlope);
1163 if (SafetyTable[i] > Value(peak))
1164 SafetyTable[i] = Value(peak);