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))))
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) {
460 Value mgValue, egValue;
461 ScaleFactor factor[2] = {SCALE_FACTOR_NORMAL, SCALE_FACTOR_NORMAL};
466 stm = pos.side_to_move();
468 mgValue = pos.mg_value();
469 egValue = pos.eg_value();
470 phase = pos.game_phase();
472 Value value = scale_by_game_phase(mgValue, egValue, phase, factor);
474 return Sign[stm] * value;
478 /// init_eval() initializes various tables used by the evaluation function.
480 void init_eval(int threads) {
482 assert(threads <= THREAD_MAX);
484 for (int i = 0; i < THREAD_MAX; i++)
489 delete MaterialTable[i];
491 MaterialTable[i] = NULL;
495 PawnTable[i] = new PawnInfoTable(PawnTableSize);
496 if (!MaterialTable[i])
497 MaterialTable[i] = new MaterialInfoTable(MaterialTableSize);
500 for (Bitboard b = 0ULL; b < 256ULL; b++)
501 BitCount8Bit[b] = count_1s(b);
505 /// quit_eval() releases heap-allocated memory at program termination.
508 for(int i = 0; i < THREAD_MAX; i++) {
510 delete MaterialTable[i];
515 /// read_weights() reads evaluation weights from the corresponding UCI
518 void read_weights(Color us) {
520 WeightMobilityMidgame = weight_option("Mobility (Middle Game)", WeightMobilityMidgameInternal);
521 WeightMobilityEndgame = weight_option("Mobility (Endgame)", WeightMobilityEndgameInternal);
522 WeightPawnStructureMidgame = weight_option("Pawn Structure (Middle Game)", WeightPawnStructureMidgameInternal);
523 WeightPawnStructureEndgame = weight_option("Pawn Structure (Endgame)", WeightPawnStructureEndgameInternal);
524 WeightPassedPawnsMidgame = weight_option("Passed Pawns (Middle Game)", WeightPassedPawnsMidgameInternal);
525 WeightPassedPawnsEndgame = weight_option("Passed Pawns (Endgame)", WeightPassedPawnsEndgameInternal);
527 Color them = opposite_color(us);
529 WeightKingSafety[us] = weight_option("Cowardice", WeightKingSafetyInternal);
530 WeightKingSafety[them] = weight_option("Aggressiveness", WeightKingOppSafetyInternal);
538 // evaluate_common() computes terms common to all pieces attack
540 int evaluate_common(const Position&p, const Bitboard& b, Color us, EvalInfo& ei,
541 int AttackWeight, const Value* mgBonus, const Value* egBonus,
542 Square s = SQ_NONE, const Value* OutpostBonus = NULL) {
544 Color them = opposite_color(us);
547 if (b & ei.kingZone[us])
549 ei.kingAttackersCount[us]++;
550 ei.kingAttackersWeight[us] += AttackWeight;
551 Bitboard bb = (b & ei.attackedBy[them][KING]);
553 ei.kingZoneAttacksCount[us] += count_1s_max_15(bb);
557 int mob = count_1s_max_15(b & ~p.pieces_of_color(us));
558 ei.mgMobility += Sign[us] * mgBonus[mob];
559 ei.egMobility += Sign[us] * egBonus[mob];
561 // Bishop and Knight outposts
562 if (!OutpostBonus || !p.square_is_weak(s, them))
565 // Initial bonus based on square
567 v = bonus = OutpostBonus[relative_square(us, s)];
569 // Increase bonus if supported by pawn, especially if the opponent has
570 // no minor piece which can exchange the outpost piece
571 if (v && (p.pawn_attacks(them, s) & p.pawns(us)))
574 if ( p.knight_count(them) == 0
575 && (SquaresByColorBB[square_color(s)] & p.bishops(them)) == EmptyBoardBB)
578 ei.mgValue += Sign[us] * bonus;
579 ei.egValue += Sign[us] * bonus;
584 // evaluate_knight() assigns bonuses and penalties to a knight of a given
585 // color on a given square.
587 void evaluate_knight(const Position &p, Square s, Color us, EvalInfo &ei) {
589 Bitboard b = p.knight_attacks(s);
590 ei.attackedBy[us][KNIGHT] |= b;
592 // King attack, mobility and outposts
593 evaluate_common(p, b, us, ei, KnightAttackWeight, MidgameKnightMobilityBonus,
594 EndgameKnightMobilityBonus, s, KnightOutpostBonus);
598 // evaluate_bishop() assigns bonuses and penalties to a bishop of a given
599 // color on a given square.
601 void evaluate_bishop(const Position &p, Square s, Color us, EvalInfo &ei) {
603 Bitboard b = bishop_attacks_bb(s, p.occupied_squares() & ~p.queens(us));
604 ei.attackedBy[us][BISHOP] |= b;
606 // King attack, mobility and outposts
607 evaluate_common(p, b, us, ei, BishopAttackWeight, MidgameBishopMobilityBonus,
608 EndgameBishopMobilityBonus, s, BishopOutpostBonus);
612 // evaluate_rook() assigns bonuses and penalties to a rook of a given
613 // color on a given square.
615 void evaluate_rook(const Position &p, Square s, Color us, EvalInfo &ei) {
617 //Bitboard b = p.rook_attacks(s);
618 Bitboard b = rook_attacks_bb(s, p.occupied_squares() & ~p.rooks_and_queens(us));
619 ei.attackedBy[us][ROOK] |= b;
621 // King attack and mobility
622 int mob = evaluate_common(p, b, us, ei, RookAttackWeight, MidgameRookMobilityBonus,
623 EndgameRookMobilityBonus);
626 Color them = opposite_color(us);
628 if ( relative_rank(us, s) == RANK_7
629 && relative_rank(us, p.king_square(them)) == RANK_8)
631 ei.mgValue += Sign[us] * MidgameRookOn7thBonus;
632 ei.egValue += Sign[us] * EndgameRookOn7thBonus;
635 // Open and half-open files
636 File f = square_file(s);
637 if (ei.pi->file_is_half_open(us, f))
639 if (ei.pi->file_is_half_open(them, f))
641 ei.mgValue += Sign[us] * RookOpenFileBonus;
642 ei.egValue += Sign[us] * RookOpenFileBonus;
646 ei.mgValue += Sign[us] * RookHalfOpenFileBonus;
647 ei.egValue += Sign[us] * RookHalfOpenFileBonus;
651 // Penalize rooks which are trapped inside a king. Penalize more if
652 // king has lost right to castle
653 if (mob > 6 || ei.pi->file_is_half_open(us, f))
656 Square ksq = p.king_square(us);
658 if ( square_file(ksq) >= FILE_E
659 && square_file(s) > square_file(ksq)
660 && (relative_rank(us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
662 // Is there a half-open file between the king and the edge of the board?
663 if (!ei.pi->has_open_file_to_right(us, square_file(ksq)))
664 ei.mgValue -= p.can_castle(us)? Sign[us] * ((TrappedRookPenalty - mob * 16) / 2)
665 : Sign[us] * (TrappedRookPenalty - mob * 16);
667 else if ( square_file(ksq) <= FILE_D
668 && square_file(s) < square_file(ksq)
669 && (relative_rank(us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
671 // Is there a half-open file between the king and the edge of the board?
672 if (!ei.pi->has_open_file_to_left(us, square_file(ksq)))
673 ei.mgValue -= p.can_castle(us)? Sign[us] * ((TrappedRookPenalty - mob * 16) / 2)
674 : Sign[us] * (TrappedRookPenalty - mob * 16);
679 // evaluate_queen() assigns bonuses and penalties to a queen of a given
680 // color on a given square.
682 void evaluate_queen(const Position &p, Square s, Color us, EvalInfo &ei) {
684 Bitboard b = p.queen_attacks(s);
685 ei.attackedBy[us][QUEEN] |= b;
687 // King attack and mobility
688 evaluate_common(p, b, us, ei, QueenAttackWeight, MidgameQueenMobilityBonus,
689 EndgameQueenMobilityBonus);
692 Color them = opposite_color(us);
694 if ( relative_rank(us, s) == RANK_7
695 && relative_rank(us, p.king_square(them)) == RANK_8)
697 ei.mgValue += Sign[us] * MidgameQueenOn7thBonus;
698 ei.egValue += Sign[us] * EndgameQueenOn7thBonus;
703 // evaluate_king() assigns bonuses and penalties to a king of a given
704 // color on a given square.
706 void evaluate_king(const Position &p, Square s, Color us, EvalInfo &ei) {
708 int shelter = 0, sign = Sign[us];
711 if(relative_rank(us, s) <= RANK_4) {
712 Bitboard pawns = p.pawns(us) & this_and_neighboring_files_bb(s);
713 Rank r = square_rank(s);
714 for(int i = 0; i < 3; i++)
715 shelter += count_1s_8bit(pawns >> ((r+(i+1)*sign) * 8)) * (64>>i);
716 ei.mgValue += sign * Value(shelter);
719 // King safety. This is quite complicated, and is almost certainly far
720 // from optimally tuned.
721 Color them = opposite_color(us);
722 if(p.queen_count(them) >= 1 && ei.kingAttackersCount[them] >= 2
723 && p.non_pawn_material(them) >= QueenValueMidgame + RookValueMidgame
724 && ei.kingZoneAttacksCount[them]) {
726 // Is it the attackers turn to move?
727 bool sente = (them == p.side_to_move());
729 // Find the attacked squares around the king which has no defenders
730 // apart from the king itself:
731 Bitboard undefended =
732 ei.attacked_by(them) & ~ei.attacked_by(us, PAWN)
733 & ~ei.attacked_by(us, KNIGHT) & ~ei.attacked_by(us, BISHOP)
734 & ~ei.attacked_by(us, ROOK) & ~ei.attacked_by(us, QUEEN)
735 & ei.attacked_by(us, KING);
736 Bitboard occ = p.occupied_squares(), b, b2;
738 // Initialize the 'attackUnits' variable, which is used later on as an
739 // index to the SafetyTable[] array. The initial is based on the number
740 // and types of the attacking pieces, the number of attacked and
741 // undefended squares around the king, the square of the king, and the
742 // quality of the pawn shelter.
744 Min((ei.kingAttackersCount[them] * ei.kingAttackersWeight[them]) / 2, 25)
745 + (ei.kingZoneAttacksCount[them] + count_1s_max_15(undefended)) * 3
746 + InitKingDanger[relative_square(us, s)] - shelter / 32;
748 // Analyse safe queen contact checks:
749 b = undefended & ei.attacked_by(them, QUEEN) & ~p.pieces_of_color(them);
751 Bitboard attackedByOthers =
752 ei.attacked_by(them, PAWN) | ei.attacked_by(them, KNIGHT)
753 | ei.attacked_by(them, BISHOP) | ei.attacked_by(them, ROOK);
754 b &= attackedByOthers;
756 // The bitboard b now contains the squares available for safe queen
758 int count = count_1s_max_15(b);
759 attackUnits += QueenContactCheckBonus * count * (sente? 2 : 1);
761 // Is there a mate threat?
762 if(QueenContactMates && !p.is_check()) {
763 Bitboard escapeSquares =
764 p.king_attacks(s) & ~p.pieces_of_color(us) & ~attackedByOthers;
766 Square from, to = pop_1st_bit(&b);
768 & ~queen_attacks_bb(to, occ & clear_mask_bb(s)))) {
769 // We have a mate, unless the queen is pinned or there
770 // is an X-ray attack through the queen.
771 for(int i = 0; i < p.queen_count(them); i++) {
772 from = p.queen_list(them, i);
773 if(bit_is_set(p.queen_attacks(from), to)
774 && !bit_is_set(p.pinned_pieces(them), from)
775 && !(rook_attacks_bb(to, occ & clear_mask_bb(from))
776 & p.rooks_and_queens(us))
777 && !(rook_attacks_bb(to, occ & clear_mask_bb(from))
778 & p.rooks_and_queens(us)))
779 ei.mateThreat[them] = make_move(from, to);
787 // Analyse safe rook contact checks:
788 if(RookContactCheckBonus) {
789 b = undefended & ei.attacked_by(them, ROOK) & ~p.pieces_of_color(them);
791 Bitboard attackedByOthers =
792 ei.attacked_by(them, PAWN) | ei.attacked_by(them, KNIGHT)
793 | ei.attacked_by(them, BISHOP) | ei.attacked_by(them, QUEEN);
794 b &= attackedByOthers;
796 int count = count_1s_max_15(b);
797 attackUnits += (RookContactCheckBonus * count * (sente? 2 : 1));
802 // Analyse safe distance checks:
803 if(QueenCheckBonus > 0 || RookCheckBonus > 0) {
804 b = p.rook_attacks(s) & ~p.pieces_of_color(them) & ~ei.attacked_by(us);
807 b2 = b & ei.attacked_by(them, QUEEN);
808 if(b2) attackUnits += QueenCheckBonus * count_1s_max_15(b2);
811 b2 = b & ei.attacked_by(them, ROOK);
812 if(b2) attackUnits += RookCheckBonus * count_1s_max_15(b2);
814 if(QueenCheckBonus > 0 || BishopCheckBonus > 0) {
815 b = p.bishop_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, BISHOP);
822 if(b2) attackUnits += BishopCheckBonus * count_1s_max_15(b2);
824 if(KnightCheckBonus > 0) {
825 b = p.knight_attacks(s) & ~p.pieces_of_color(them) & ~ei.attacked_by(us);
827 b2 = b & ei.attacked_by(them, KNIGHT);
828 if(b2) attackUnits += KnightCheckBonus * count_1s_max_15(b2);
831 // Analyse discovered checks (only for non-pawns right now, consider
832 // adding pawns later).
833 if(DiscoveredCheckBonus) {
834 b = p.discovered_check_candidates(them) & ~p.pawns();
837 DiscoveredCheckBonus * count_1s_max_15(b) * (sente? 2 : 1);
840 // Has a mate threat been found? We don't do anything here if the
841 // side with the mating move is the side to move, because in that
842 // case the mating side will get a huge bonus at the end of the main
843 // evaluation function instead.
844 if(ei.mateThreat[them] != MOVE_NONE)
845 attackUnits += MateThreatBonus;
847 // Ensure that attackUnits is between 0 and 99, in order to avoid array
848 // out of bounds errors:
849 if(attackUnits < 0) attackUnits = 0;
850 if(attackUnits >= 100) attackUnits = 99;
852 // Finally, extract the king safety score from the SafetyTable[] array.
853 // Add the score to the evaluation, and also to ei.futilityMargin. The
854 // reason for adding the king safety score to the futility margin is
855 // that the king safety scores can sometimes be very big, and that
856 // capturing a single attacking piece can therefore result in a score
857 // change far bigger than the value of the captured piece.
858 Value v = apply_weight(SafetyTable[attackUnits], WeightKingSafety[us]);
859 ei.mgValue -= sign * v;
860 if(us == p.side_to_move())
861 ei.futilityMargin += v;
866 // evaluate_passed_pawns() evaluates the passed pawns for both sides.
868 void evaluate_passed_pawns(const Position &pos, EvalInfo &ei) {
869 bool hasUnstoppable[2] = {false, false};
870 int movesToGo[2] = {100, 100};
872 for(Color us = WHITE; us <= BLACK; us++) {
873 Color them = opposite_color(us);
874 Square ourKingSq = pos.king_square(us);
875 Square theirKingSq = pos.king_square(them);
876 Bitboard b = ei.pi->passed_pawns() & pos.pawns(us), b2, b3, b4;
879 Square s = pop_1st_bit(&b);
880 assert(pos.piece_on(s) == pawn_of_color(us));
881 assert(pos.pawn_is_passed(us, s));
883 int r = int(relative_rank(us, s) - RANK_2);
884 int tr = Max(0, r * (r-1));
885 Square blockSq = s + pawn_push(us);
887 // Base bonus based on rank:
888 Value mbonus = Value(20 * tr);
889 Value ebonus = Value(10 + r * r * 10);
891 // Adjust bonus based on king proximity:
892 ebonus -= Value(square_distance(ourKingSq, blockSq) * 3 * tr);
894 Value(square_distance(ourKingSq, blockSq + pawn_push(us)) * 1 * tr);
895 ebonus += Value(square_distance(theirKingSq, blockSq) * 6 * tr);
897 // If the pawn is free to advance, increase bonus:
898 if(pos.square_is_empty(blockSq)) {
900 b2 = squares_in_front_of(us, s);
901 b3 = b2 & ei.attacked_by(them);
902 b4 = b2 & ei.attacked_by(us);
903 if((b2 & pos.pieces_of_color(them)) == EmptyBoardBB) {
904 // There are no enemy pieces in the pawn's path! Are any of the
905 // squares in the pawn's path attacked by the enemy?
906 if(b3 == EmptyBoardBB)
907 // No enemy attacks, huge bonus!
908 ebonus += Value(tr * ((b2 == b4)? 17 : 15));
910 // OK, there are enemy attacks. Are those squares which are
911 // attacked by the enemy also attacked by us? If yes, big bonus
912 // (but smaller than when there are no enemy attacks), if no,
913 // somewhat smaller bonus.
914 ebonus += Value(tr * (((b3 & b4) == b3)? 13 : 8));
917 // There are some enemy pieces in the pawn's path. While this is
918 // sad, we still assign a moderate bonus if all squares in the path
919 // which are either occupied by or attacked by enemy pieces are
920 // also attacked by us.
921 if(((b3 | (b2 & pos.pieces_of_color(them))) & ~b4) == EmptyBoardBB)
922 ebonus += Value(tr * 6);
924 // At last, add a small bonus when there are no *friendly* pieces
925 // in the pawn's path:
926 if((b2 & pos.pieces_of_color(us)) == EmptyBoardBB)
930 // If the pawn is supported by a friendly pawn, increase bonus.
931 b2 = pos.pawns(us) & neighboring_files_bb(s);
933 ebonus += Value(r * 20);
934 else if(pos.pawn_attacks(them, s) & b2)
935 ebonus += Value(r * 12);
937 // If the other side has only a king, check whether the pawn is
939 if(pos.non_pawn_material(them) == Value(0)) {
943 qsq = relative_square(us, make_square(square_file(s), RANK_8));
944 d = square_distance(s, qsq) - square_distance(theirKingSq, qsq)
945 + ((us == pos.side_to_move())? 0 : 1);
948 int mtg = RANK_8 - relative_rank(us, s);
950 count_1s_max_15(squares_in_front_of(us,s)&pos.occupied_squares());
954 hasUnstoppable[us] = true;
955 movesToGo[us] = Min(movesToGo[us], mtg);
959 // Rook pawns are a special case: They are sometimes worse, and
960 // sometimes better than other passed pawns. It is difficult to find
961 // good rules for determining whether they are good or bad. For now,
962 // we try the following: Increase the value for rook pawns if the
963 // other side has no pieces apart from a knight, and decrease the
964 // value if the other side has a rook or queen.
965 if(square_file(s) == FILE_A || square_file(s) == FILE_H) {
966 if(pos.non_pawn_material(them) == KnightValueMidgame
967 && pos.knight_count(them) == 1)
968 ebonus += ebonus / 4;
969 else if(pos.rooks_and_queens(them))
970 ebonus -= ebonus / 4;
973 // Add the scores for this pawn to the middle game and endgame eval.
974 ei.mgValue += apply_weight(Sign[us] * mbonus, WeightPassedPawnsMidgame);
975 ei.egValue += apply_weight(Sign[us] * ebonus, WeightPassedPawnsEndgame);
979 // Does either side have an unstoppable passed pawn?
980 if(hasUnstoppable[WHITE] && !hasUnstoppable[BLACK])
981 ei.egValue += UnstoppablePawnValue - Value(0x40 * movesToGo[WHITE]);
982 else if(hasUnstoppable[BLACK] && !hasUnstoppable[WHITE])
983 ei.egValue -= UnstoppablePawnValue - Value(0x40 * movesToGo[BLACK]);
984 else if(hasUnstoppable[BLACK] && hasUnstoppable[WHITE]) {
985 // Both sides have unstoppable pawns! Try to find out who queens
986 // first. We begin by transforming 'movesToGo' to the number of
987 // plies until the pawn queens for both sides:
988 movesToGo[WHITE] *= 2;
989 movesToGo[BLACK] *= 2;
990 movesToGo[pos.side_to_move()]--;
992 // If one side queens at least three plies before the other, that
994 if(movesToGo[WHITE] <= movesToGo[BLACK] - 3)
995 ei.egValue += UnstoppablePawnValue - Value(0x40 * (movesToGo[WHITE]/2));
996 else if(movesToGo[BLACK] <= movesToGo[WHITE] - 3)
997 ei.egValue -= UnstoppablePawnValue - Value(0x40 * (movesToGo[BLACK]/2));
999 // We could also add some rules about the situation when one side
1000 // queens exactly one ply before the other: Does the first queen
1001 // check the opponent's king, or attack the opponent's queening square?
1002 // This is slightly tricky to get right, because it is possible that
1003 // the opponent's king has moved somewhere before the first pawn queens.
1008 // evaluate_trapped_bishop_a7h7() determines whether a bishop on a7/h7
1009 // (a2/h2 for black) is trapped by enemy pawns, and assigns a penalty
1012 void evaluate_trapped_bishop_a7h7(const Position &pos, Square s, Color us,
1015 assert(square_is_ok(s));
1016 assert(pos.piece_on(s) == bishop_of_color(us));
1018 Square b6 = relative_square(us, (square_file(s) == FILE_A) ? SQ_B6 : SQ_G6);
1019 Square b8 = relative_square(us, (square_file(s) == FILE_A) ? SQ_B8 : SQ_G8);
1021 if ( pos.piece_on(b6) == pawn_of_color(opposite_color(us))
1022 && pos.see(s, b6) < 0
1023 && pos.see(s, b8) < 0)
1025 ei.mgValue -= Sign[us] * TrappedBishopA7H7Penalty;
1026 ei.egValue -= Sign[us] * TrappedBishopA7H7Penalty;
1031 // evaluate_trapped_bishop_a1h1() determines whether a bishop on a1/h1
1032 // (a8/h8 for black) is trapped by a friendly pawn on b2/g2 (b7/g7 for
1033 // black), and assigns a penalty if it is. This pattern can obviously
1034 // only occur in Chess960 games.
1036 void evaluate_trapped_bishop_a1h1(const Position &pos, Square s, Color us,
1038 Piece pawn = pawn_of_color(us);
1042 assert(square_is_ok(s));
1043 assert(pos.piece_on(s) == bishop_of_color(us));
1045 if(square_file(s) == FILE_A) {
1046 b2 = relative_square(us, SQ_B2);
1047 b3 = relative_square(us, SQ_B3);
1048 c3 = relative_square(us, SQ_C3);
1051 b2 = relative_square(us, SQ_G2);
1052 b3 = relative_square(us, SQ_G3);
1053 c3 = relative_square(us, SQ_F3);
1056 if(pos.piece_on(b2) == pawn) {
1059 if(!pos.square_is_empty(b3))
1060 penalty = 2*TrappedBishopA1H1Penalty;
1061 else if(pos.piece_on(c3) == pawn)
1062 penalty = TrappedBishopA1H1Penalty;
1064 penalty = TrappedBishopA1H1Penalty / 2;
1066 ei.mgValue -= Sign[us] * penalty;
1067 ei.egValue -= Sign[us] * penalty;
1073 // apply_weight applies an evaluation weight to a value.
1075 inline Value apply_weight(Value v, int w) {
1076 return (v*w) / 0x100;
1080 // scale_by_game_phase interpolates between a middle game and an endgame
1081 // score, based on game phase. It also scales the return value by a
1082 // ScaleFactor array.
1084 Value scale_by_game_phase(Value mv, Value ev, Phase ph, ScaleFactor sf[]) {
1086 assert(mv > -VALUE_INFINITE && mv < VALUE_INFINITE);
1087 assert(ev > -VALUE_INFINITE && ev < VALUE_INFINITE);
1088 assert(ph >= PHASE_ENDGAME && ph <= PHASE_MIDGAME);
1090 ev = apply_scale_factor(ev, sf[(ev > Value(0) ? WHITE : BLACK)]);
1092 // Linearized sigmoid interpolator
1094 sph -= (64 - sph) / 4;
1095 sph = Min(PHASE_MIDGAME, Max(PHASE_ENDGAME, sph));
1097 Value result = Value(int((mv * sph + ev * (128 - sph)) / 128));
1099 return Value(int(result) & ~(GrainSize - 1));
1103 // count_1s_8bit() counts the number of nonzero bits in the 8 least
1104 // significant bits of a Bitboard. This function is used by the king
1105 // shield evaluation.
1107 int count_1s_8bit(Bitboard b) {
1108 return int(BitCount8Bit[b & 0xFF]);
1112 // compute_weight() computes the value of an evaluation weight, by combining
1113 // an UCI-configurable weight with an internal weight.
1115 int compute_weight(int uciWeight, int internalWeight) {
1116 uciWeight = (uciWeight * 0x100) / 100;
1117 return (uciWeight * internalWeight) / 0x100;
1121 // helper used in read_weights()
1122 int weight_option(const std::string& opt, int weight) {
1124 return compute_weight(get_option_value_int(opt), weight);
1128 // init_safety() initizes the king safety evaluation, based on UCI
1129 // parameters. It is called from read_weights().
1131 void init_safety() {
1133 QueenContactCheckBonus = get_option_value_int("Queen Contact Check Bonus");
1134 RookContactCheckBonus = get_option_value_int("Rook Contact Check Bonus");
1135 QueenCheckBonus = get_option_value_int("Queen Check Bonus");
1136 RookCheckBonus = get_option_value_int("Rook Check Bonus");
1137 BishopCheckBonus = get_option_value_int("Bishop Check Bonus");
1138 KnightCheckBonus = get_option_value_int("Knight Check Bonus");
1139 DiscoveredCheckBonus = get_option_value_int("Discovered Check Bonus");
1140 MateThreatBonus = get_option_value_int("Mate Threat Bonus");
1142 int maxSlope = get_option_value_int("King Safety Max Slope");
1143 int peak = get_option_value_int("King Safety Max Value") * 256 / 100;
1144 double a = get_option_value_int("King Safety Coefficient") / 100.0;
1145 double b = get_option_value_int("King Safety X Intercept");
1146 bool quad = (get_option_value_string("King Safety Curve") == "Quadratic");
1147 bool linear = (get_option_value_string("King Safety Curve") == "Linear");
1149 for (int i = 0; i < 100; i++)
1152 SafetyTable[i] = Value(0);
1154 SafetyTable[i] = Value((int)(a * (i - b) * (i - b)));
1156 SafetyTable[i] = Value((int)(100 * a * (i - b)));
1159 for (int i = 0; i < 100; i++)
1161 if (SafetyTable[i+1] - SafetyTable[i] > maxSlope)
1162 for (int j = i + 1; j < 100; j++)
1163 SafetyTable[j] = SafetyTable[j-1] + Value(maxSlope);
1165 if (SafetyTable[i] > Value(peak))
1166 SafetyTable[i] = Value(peak);