Stockfish, a UCI chess playing engine derived from Glaurung 2.1
Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad
- Copyright (C) 2015-2017 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
+ Copyright (C) 2015-2018 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
Stockfish is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
#define V Value
#define S(mg, eg) make_score(mg, eg)
- // Isolated pawn penalty by opposed flag
- const Score Isolated[] = { S(45, 40), S(30, 27) };
-
- // Backward pawn penalty by opposed flag
- const Score Backward[] = { S(56, 33), S(41, 19) };
-
- // Unsupported pawn penalty for pawns which are neither isolated or backward
- const Score Unsupported = S(17, 8);
-
- // Connected pawn bonus by opposed, phalanx, twice supported and rank
- Score Connected[2][2][2][RANK_NB];
-
- // Doubled pawn penalty
- const Score Doubled = S(18, 38);
-
- // Lever bonus by rank
- const Score Lever[RANK_NB] = {
- S( 0, 0), S( 0, 0), S(0, 0), S(0, 0),
- S(17, 16), S(33, 32), S(0, 0), S(0, 0)
- };
-
- // Weakness of our pawn shelter in front of the king by [distance from edge][rank].
- // RANK_1 = 0 is used for files where we have no pawns or our pawn is behind our king.
- const Value ShelterWeakness[][RANK_NB] = {
- { V(100), V(20), V(10), V(46), V(82), V( 86), V( 98) },
- { V(116), V( 4), V(28), V(87), V(94), V(108), V(104) },
- { V(109), V( 1), V(59), V(87), V(62), V( 91), V(116) },
- { V( 75), V(12), V(43), V(59), V(90), V( 84), V(112) }
+ // Pawn penalties
+ constexpr Score Isolated = S(13, 16);
+ constexpr Score Backward = S(17, 11);
+ constexpr Score Doubled = S(13, 40);
+
+ // Connected pawn bonus by opposed, phalanx, #support and rank
+ Score Connected[2][2][3][RANK_NB];
+
+ // Strength of pawn shelter for our king by [distance from edge][rank].
+ // RANK_1 = 0 is used for files where we have no pawn, or pawn is behind our king.
+ constexpr Value ShelterStrength[int(FILE_NB) / 2][RANK_NB] = {
+ { V( 7), V(76), V( 84), V( 38), V( 7), V( 30), V(-19) },
+ { V(-13), V(83), V( 42), V(-27), V( 2), V(-32), V(-45) },
+ { V(-26), V(63), V( 5), V(-44), V( -5), V( 2), V(-59) },
+ { V(-19), V(53), V(-11), V(-22), V(-12), V(-51), V(-60) }
};
- // Danger of enemy pawns moving toward our king by [type][distance from edge][rank].
- // For the unopposed and unblocked cases, RANK_1 = 0 is used when opponent has no pawn
- // on the given file, or their pawn is behind our king.
- const Value StormDanger[][4][RANK_NB] = {
- { { V( 0), V(-290), V(-274), V(57), V(41) }, //BlockedByKing
- { V( 0), V( 60), V( 144), V(39), V(13) },
- { V( 0), V( 65), V( 141), V(41), V(34) },
- { V( 0), V( 53), V( 127), V(56), V(14) } },
- { { V( 4), V( 73), V( 132), V(46), V(31) }, //Unopposed
- { V( 1), V( 64), V( 143), V(26), V(13) },
- { V( 1), V( 47), V( 110), V(44), V(24) },
- { V( 0), V( 72), V( 127), V(50), V(31) } },
- { { V( 0), V( 0), V( 79), V(23), V( 1) }, //BlockedByPawn
- { V( 0), V( 0), V( 148), V(27), V( 2) },
- { V( 0), V( 0), V( 161), V(16), V( 1) },
- { V( 0), V( 0), V( 171), V(22), V(15) } },
- { { V(22), V( 45), V( 104), V(62), V( 6) }, //Unblocked
- { V(31), V( 30), V( 99), V(39), V(19) },
- { V(23), V( 29), V( 96), V(41), V(15) },
- { V(21), V( 23), V( 116), V(41), V(15) } }
+ // Danger of enemy pawns moving toward our king by [distance from edge][rank].
+ // RANK_1 = 0 is used for files where the enemy has no pawn, or their pawn
+ // is behind our king.
+ constexpr Value UnblockedStorm[int(FILE_NB) / 2][RANK_NB] = {
+ { V( 25), V( 79), V(107), V( 51), V( 27), V( 0), V( 0) },
+ { V( 5), V( 35), V(121), V( -2), V( 15), V(-10), V(-10) },
+ { V(-20), V( 22), V( 98), V( 36), V( 7), V(-20), V(-20) },
+ { V(-27), V( 24), V( 80), V( 25), V( -4), V(-30), V(-30) }
};
- // Max bonus for king safety. Corresponds to start position with all the pawns
- // in front of the king and no enemy pawn on the horizon.
- const Value MaxSafetyBonus = V(258);
+ // Danger of blocked enemy pawns storming our king, by rank
+ constexpr Value BlockedStorm[RANK_NB] =
+ { V( 0), V( 0), V( 75), V(-10), V(-20), V(-20), V(-20) };
#undef S
#undef V
template<Color Us>
Score evaluate(const Position& pos, Pawns::Entry* e) {
- const Color Them = (Us == WHITE ? BLACK : WHITE);
- const Square Up = (Us == WHITE ? NORTH : SOUTH);
- const Square Right = (Us == WHITE ? NORTH_EAST : SOUTH_WEST);
- const Square Left = (Us == WHITE ? NORTH_WEST : SOUTH_EAST);
+ constexpr Color Them = (Us == WHITE ? BLACK : WHITE);
+ constexpr Direction Up = (Us == WHITE ? NORTH : SOUTH);
Bitboard b, neighbours, stoppers, doubled, supported, phalanx;
- Bitboard lever, leverPush, connected;
+ Bitboard lever, leverPush;
Square s;
bool opposed, backward;
Score score = SCORE_ZERO;
Bitboard ourPawns = pos.pieces( Us, PAWN);
Bitboard theirPawns = pos.pieces(Them, PAWN);
- e->passedPawns[Us] = e->pawnAttacksSpan[Us] = 0;
+ e->passedPawns[Us] = e->pawnAttacksSpan[Us] = e->weakUnopposed[Us] = 0;
e->semiopenFiles[Us] = 0xFF;
e->kingSquares[Us] = SQ_NONE;
- e->pawnAttacks[Us] = shift<Right>(ourPawns) | shift<Left>(ourPawns);
+ e->pawnAttacks[Us] = pawn_attacks_bb<Us>(ourPawns);
e->pawnsOnSquares[Us][BLACK] = popcount(ourPawns & DarkSquares);
e->pawnsOnSquares[Us][WHITE] = pos.count<PAWN>(Us) - e->pawnsOnSquares[Us][BLACK];
neighbours = ourPawns & adjacent_files_bb(f);
phalanx = neighbours & rank_bb(s);
supported = neighbours & rank_bb(s - Up);
- connected = supported | phalanx;
-
- // A pawn is backward when it is behind all pawns of the same color on the
- // adjacent files and cannot be safely advanced.
- if (!neighbours || lever || relative_rank(Us, s) >= RANK_5)
- backward = false;
- else
- {
- // Find the backmost rank with neighbours or stoppers
- b = rank_bb(backmost_sq(Us, neighbours | stoppers));
- // The pawn is backward when it cannot safely progress to that rank:
- // either there is a stopper in the way on this rank, or there is a
- // stopper on adjacent file which controls the way to that rank.
- backward = (b | shift<Up>(b & adjacent_files_bb(f))) & stoppers;
-
- assert(!backward || !(pawn_attack_span(Them, s + Up) & neighbours));
- }
+ // A pawn is backward when it is behind all pawns of the same color
+ // on the adjacent files and cannot be safely advanced.
+ backward = !(ourPawns & pawn_attack_span(Them, s + Up))
+ && (stoppers & (leverPush | (s + Up)));
// Passed pawns will be properly scored in evaluation because we need
// full attack info to evaluate them. Include also not passed pawns
// not attacked more times than defended.
if ( !(stoppers ^ lever ^ leverPush)
&& !(ourPawns & forward_file_bb(Us, s))
- && popcount(supported) >= popcount(lever)
+ && popcount(supported) >= popcount(lever) - 1
&& popcount(phalanx) >= popcount(leverPush))
e->passedPawns[Us] |= s;
}
// Score this pawn
- if (!neighbours)
- score -= Isolated[opposed];
+ if (supported | phalanx)
+ score += Connected[opposed][bool(phalanx)][popcount(supported)][relative_rank(Us, s)];
- else if (backward)
- score -= Backward[opposed];
+ else if (!neighbours)
+ score -= Isolated, e->weakUnopposed[Us] += !opposed;
- else if (!supported)
- score -= Unsupported;
-
- if (connected)
- score += Connected[opposed][!!phalanx][more_than_one(supported)][relative_rank(Us, s)];
+ else if (backward)
+ score -= Backward, e->weakUnopposed[Us] += !opposed;
if (doubled && !supported)
score -= Doubled;
-
- if (lever)
- score += Lever[relative_rank(Us, s)];
}
return score;
void init() {
- static const int Seed[RANK_NB] = { 0, 8, 19, 13, 71, 94, 169, 324 };
+ static constexpr int Seed[RANK_NB] = { 0, 13, 24, 18, 65, 100, 175, 330 };
for (int opposed = 0; opposed <= 1; ++opposed)
for (int phalanx = 0; phalanx <= 1; ++phalanx)
- for (int apex = 0; apex <= 1; ++apex)
+ for (int support = 0; support <= 2; ++support)
for (Rank r = RANK_2; r < RANK_8; ++r)
{
- int v = (Seed[r] + (phalanx ? (Seed[r + 1] - Seed[r]) / 2 : 0)) >> opposed;
- v += (apex ? v / 2 : 0);
- Connected[opposed][phalanx][apex][r] = make_score(v, v * (r-2) / 4);
+ int v = 17 * support;
+ v += (Seed[r] + (phalanx ? (Seed[r + 1] - Seed[r]) / 2 : 0)) >> opposed;
+
+ Connected[opposed][phalanx][support][r] = make_score(v, v * (r - 2) / 4);
}
}
return e;
e->key = key;
- e->score = evaluate<WHITE>(pos, e) - evaluate<BLACK>(pos, e);
- e->asymmetry = popcount(e->semiopenFiles[WHITE] ^ e->semiopenFiles[BLACK]);
+ e->scores[WHITE] = evaluate<WHITE>(pos, e);
+ e->scores[BLACK] = evaluate<BLACK>(pos, e);
e->openFiles = popcount(e->semiopenFiles[WHITE] & e->semiopenFiles[BLACK]);
+ e->asymmetry = popcount( (e->passedPawns[WHITE] | e->passedPawns[BLACK])
+ | (e->semiopenFiles[WHITE] ^ e->semiopenFiles[BLACK]));
+
return e;
}
-/// Entry::shelter_storm() calculates shelter and storm penalties for the file
-/// the king is on, as well as the two closest files.
+/// Entry::evaluate_shelter() calculates the shelter bonus and the storm
+/// penalty for a king, looking at the king file and the two closest files.
template<Color Us>
-Value Entry::shelter_storm(const Position& pos, Square ksq) {
-
- const Color Them = (Us == WHITE ? BLACK : WHITE);
+Value Entry::evaluate_shelter(const Position& pos, Square ksq) {
- enum { BlockedByKing, Unopposed, BlockedByPawn, Unblocked };
+ constexpr Color Them = (Us == WHITE ? BLACK : WHITE);
+ constexpr Direction Down = (Us == WHITE ? SOUTH : NORTH);
+ constexpr Bitboard BlockRanks = (Us == WHITE ? Rank1BB | Rank2BB : Rank8BB | Rank7BB);
Bitboard b = pos.pieces(PAWN) & (forward_ranks_bb(Us, ksq) | rank_bb(ksq));
Bitboard ourPawns = b & pos.pieces(Us);
Bitboard theirPawns = b & pos.pieces(Them);
- Value safety = MaxSafetyBonus;
- File center = std::max(FILE_B, std::min(FILE_G, file_of(ksq)));
- for (File f = center - File(1); f <= center + File(1); ++f)
+ Value safety = (ourPawns & file_bb(ksq)) ? Value(5) : Value(-5);
+
+ if (shift<Down>(theirPawns) & (FileABB | FileHBB) & BlockRanks & ksq)
+ safety += Value(374);
+
+ File center = std::max(FILE_B, std::min(FILE_G, file_of(ksq)));
+ for (File f = File(center - 1); f <= File(center + 1); ++f)
{
b = ourPawns & file_bb(f);
- Rank rkUs = b ? relative_rank(Us, backmost_sq(Us, b)) : RANK_1;
+ int ourRank = b ? relative_rank(Us, backmost_sq(Us, b)) : 0;
b = theirPawns & file_bb(f);
- Rank rkThem = b ? relative_rank(Us, frontmost_sq(Them, b)) : RANK_1;
-
- int d = std::min(f, FILE_H - f);
- safety -= ShelterWeakness[d][rkUs]
- + StormDanger
- [f == file_of(ksq) && rkThem == relative_rank(Us, ksq) + 1 ? BlockedByKing :
- rkUs == RANK_1 ? Unopposed :
- rkThem == rkUs + 1 ? BlockedByPawn : Unblocked]
- [d][rkThem];
+ int theirRank = b ? relative_rank(Us, frontmost_sq(Them, b)) : 0;
+
+ int d = std::min(f, ~f);
+ safety += ShelterStrength[d][ourRank];
+ safety -= (ourRank && (ourRank == theirRank - 1)) ? BlockedStorm[theirRank]
+ : UnblockedStorm[d][theirRank];
}
return safety;
if (pawns)
while (!(DistanceRingBB[ksq][minKingPawnDistance++] & pawns)) {}
- Value bonus = shelter_storm<Us>(pos, ksq);
+ Value bonus = evaluate_shelter<Us>(pos, ksq);
// If we can castle use the bonus after the castling if it is bigger
if (pos.can_castle(MakeCastling<Us, KING_SIDE>::right))
- bonus = std::max(bonus, shelter_storm<Us>(pos, relative_square(Us, SQ_G1)));
+ bonus = std::max(bonus, evaluate_shelter<Us>(pos, relative_square(Us, SQ_G1)));
if (pos.can_castle(MakeCastling<Us, QUEEN_SIDE>::right))
- bonus = std::max(bonus, shelter_storm<Us>(pos, relative_square(Us, SQ_C1)));
+ bonus = std::max(bonus, evaluate_shelter<Us>(pos, relative_square(Us, SQ_C1)));
return make_score(bonus, -16 * minKingPawnDistance);
}