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) 2015-2018 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
+ Copyright (C) 2015-2019 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 S(mg, eg) make_score(mg, eg)
// Pawn penalties
- constexpr Score Backward = S( 9, 24);
- constexpr Score Doubled = S(11, 56);
- constexpr Score Isolated = S( 5, 15);
+ constexpr Score Backward = S( 9, 24);
+ constexpr Score BlockedStorm = S(82, 82);
+ constexpr Score Doubled = S(11, 56);
+ constexpr Score Isolated = S( 5, 15);
+ constexpr Score WeakLever = S( 0, 56);
+ constexpr Score WeakUnopposed = S(13, 27);
- // Connected pawn bonus by opposed, phalanx, #support and rank
- Score Connected[2][2][3][RANK_NB];
+ // Connected pawn bonus
+ constexpr int Connected[RANK_NB] = { 0, 7, 8, 12, 29, 48, 86 };
// 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.
// 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.
+ // is behind our king. Note that UnblockedStorm[0][1-2] accommodate opponent pawn
+ // on edge, likely blocked by our king.
constexpr Value UnblockedStorm[int(FILE_NB) / 2][RANK_NB] = {
- { V( 89), V(107), V(123), V(93), V(57), V( 45), V( 51) },
- { V( 44), V(-18), V(123), V(46), V(39), V( -7), V( 23) },
- { V( 4), V( 52), V(162), V(37), V( 7), V(-14), V( -2) },
- { V(-10), V(-14), V( 90), V(15), V( 2), V( -7), V(-16) }
+ { V( 89), V(-285), V(-185), V(93), V(57), V( 45), V( 51) },
+ { V( 44), V( -18), V( 123), V(46), V(39), V( -7), V( 23) },
+ { V( 4), V( 52), V( 162), V(37), V( 7), V(-14), V( -2) },
+ { V(-10), V( -14), V( 90), V(15), V( 2), V( -7), V(-16) }
};
- // Danger of blocked enemy pawns storming our king, by rank
- constexpr Value BlockedStorm[RANK_NB] =
- { V(0), V(0), V(66), V(6), V(5), V(1), V(15) };
-
#undef S
#undef V
constexpr Color Them = (Us == WHITE ? BLACK : WHITE);
constexpr Direction Up = (Us == WHITE ? NORTH : SOUTH);
- Bitboard b, neighbours, stoppers, doubled, supported, phalanx;
+ Bitboard neighbours, stoppers, support, phalanx;
Bitboard lever, leverPush;
Square s;
- bool opposed, backward;
+ bool opposed, backward, passed, doubled;
Score score = SCORE_ZERO;
const Square* pl = pos.squares<PAWN>(Us);
Bitboard ourPawns = pos.pieces( Us, PAWN);
Bitboard theirPawns = pos.pieces(Them, PAWN);
- e->passedPawns[Us] = e->pawnAttacksSpan[Us] = e->weakUnopposed[Us] = 0;
- e->semiopenFiles[Us] = 0xFF;
- e->kingSquares[Us] = SQ_NONE;
- 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];
+ Bitboard doubleAttackThem = pawn_double_attacks_bb<Them>(theirPawns);
+
+ e->passedPawns[Us] = e->pawnAttacksSpan[Us] = 0;
+ e->kingSquares[Us] = SQ_NONE;
+ e->pawnAttacks[Us] = pawn_attacks_bb<Us>(ourPawns);
// Loop through all pawns of the current color and score each pawn
while ((s = *pl++) != SQ_NONE)
{
assert(pos.piece_on(s) == make_piece(Us, PAWN));
- File f = file_of(s);
+ Rank r = relative_rank(Us, s);
- e->semiopenFiles[Us] &= ~(1 << f);
e->pawnAttacksSpan[Us] |= pawn_attack_span(Us, s);
// Flag the pawn
opposed = theirPawns & forward_file_bb(Us, s);
- stoppers = theirPawns & passed_pawn_mask(Us, s);
+ stoppers = theirPawns & passed_pawn_span(Us, s);
lever = theirPawns & PawnAttacks[Us][s];
leverPush = theirPawns & PawnAttacks[Us][s + Up];
doubled = ourPawns & (s - Up);
- neighbours = ourPawns & adjacent_files_bb(f);
+ neighbours = ourPawns & adjacent_files_bb(s);
phalanx = neighbours & rank_bb(s);
- supported = neighbours & rank_bb(s - Up);
+ support = neighbours & rank_bb(s - Up);
- // 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))
+ // A pawn is backward when it is behind all pawns of the same color on
+ // the adjacent files and cannot safely advance. Phalanx and isolated
+ // pawns will be excluded when the pawn is scored.
+ backward = !(neighbours & forward_ranks_bb(Them, s))
&& (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
- // which could become passed after one or two pawn pushes when are
- // not attacked more times than defended.
- if ( !(stoppers ^ lever ^ leverPush)
- && popcount(supported) >= popcount(lever) - 1
- && popcount(phalanx) >= popcount(leverPush))
+ // A pawn is passed if one of the three following conditions is true:
+ // (a) there is no stoppers except some levers
+ // (b) the only stoppers are the leverPush, but we outnumber them
+ // (c) there is only one front stopper which can be levered.
+ passed = !(stoppers ^ lever)
+ || ( !(stoppers ^ leverPush)
+ && popcount(phalanx) >= popcount(leverPush))
+ || ( stoppers == square_bb(s + Up) && r >= RANK_5
+ && (shift<Up>(support) & ~(theirPawns | doubleAttackThem)));
+
+ // Passed pawns will be properly scored later in evaluation when we have
+ // full attack info.
+ if (passed)
e->passedPawns[Us] |= s;
- else if ( stoppers == SquareBB[s + Up]
- && relative_rank(Us, s) >= RANK_5)
+ // Score this pawn
+ if (support | phalanx)
{
- b = shift<Up>(supported) & ~theirPawns;
- while (b)
- if (!more_than_one(theirPawns & PawnAttacks[Us][pop_lsb(&b)]))
- e->passedPawns[Us] |= s;
- }
+ int v = Connected[r] * (2 + bool(phalanx) - opposed)
+ + 17 * popcount(support);
- // Score this pawn
- if (supported | phalanx)
- score += Connected[opposed][bool(phalanx)][popcount(supported)][relative_rank(Us, s)];
+ score += make_score(v, v * (r - 2) / 4);
+ }
else if (!neighbours)
- score -= Isolated, e->weakUnopposed[Us] += !opposed;
+ score -= Isolated + WeakUnopposed * !opposed;
else if (backward)
- score -= Backward, e->weakUnopposed[Us] += !opposed;
+ score -= Backward + WeakUnopposed * !opposed;
- if (doubled && !supported)
- score -= Doubled;
+ if (!support)
+ score -= Doubled * doubled
+ + WeakLever * more_than_one(lever);
}
return score;
namespace Pawns {
-/// Pawns::init() initializes some tables needed by evaluation. Instead of using
-/// hard-coded tables, when makes sense, we prefer to calculate them with a formula
-/// to reduce independent parameters and to allow easier tuning and better insight.
-
-void init() {
-
- 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 support = 0; support <= 2; ++support)
- for (Rank r = RANK_2; r < RANK_8; ++r)
- {
- 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);
- }
-}
-
-
/// Pawns::probe() looks up the current position's pawns configuration in
/// the pawns hash table. It returns a pointer to the Entry if the position
/// is found. Otherwise a new Entry is computed and stored there, so we don't
e->key = key;
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;
}
/// penalty for a king, looking at the king file and the two closest files.
template<Color Us>
-Value Entry::evaluate_shelter(const Position& pos, Square ksq) {
+Score Entry::evaluate_shelter(const Position& pos, Square ksq) {
- constexpr Color Them = (Us == WHITE ? BLACK : WHITE);
- constexpr Direction Down = (Us == WHITE ? SOUTH : NORTH);
- constexpr Bitboard BlockRanks = (Us == WHITE ? Rank1BB | Rank2BB : Rank8BB | Rank7BB);
+ constexpr Color Them = (Us == WHITE ? BLACK : WHITE);
Bitboard b = pos.pieces(PAWN) & ~forward_ranks_bb(Them, ksq);
Bitboard ourPawns = b & pos.pieces(Us);
Bitboard theirPawns = b & pos.pieces(Them);
- Value safety = (shift<Down>(theirPawns) & (FileABB | FileHBB) & BlockRanks & ksq) ?
- Value(374) : Value(5);
+ Score bonus = make_score(5, 5);
- File center = std::max(FILE_B, std::min(FILE_G, file_of(ksq)));
+ File center = clamp(file_of(ksq), FILE_B, FILE_G);
for (File f = File(center - 1); f <= File(center + 1); ++f)
{
b = ourPawns & file_bb(f);
- int ourRank = b ? relative_rank(Us, backmost_sq(Us, b)) : 0;
+ int ourRank = b ? relative_rank(Us, frontmost_sq(Them, b)) : 0;
b = theirPawns & file_bb(f);
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];
+ File d = map_to_queenside(f);
+ bonus += make_score(ShelterStrength[d][ourRank], 0);
+
+ if (ourRank && (ourRank == theirRank - 1))
+ bonus -= BlockedStorm * int(theirRank == RANK_3);
+ else
+ bonus -= make_score(UnblockedStorm[d][theirRank], 0);
}
- return safety;
+ return bonus;
}
/// when king square changes, which is about 20% of total king_safety() calls.
template<Color Us>
-Score Entry::do_king_safety(const Position& pos, Square ksq) {
+Score Entry::do_king_safety(const Position& pos) {
+ Square ksq = pos.square<KING>(Us);
kingSquares[Us] = ksq;
- castlingRights[Us] = pos.can_castle(Us);
- int minKingPawnDistance = 0;
+ castlingRights[Us] = pos.castling_rights(Us);
- Bitboard pawns = pos.pieces(Us, PAWN);
- if (pawns)
- while (!(DistanceRingBB[ksq][++minKingPawnDistance] & pawns)) {}
+ Score shelters[3] = { evaluate_shelter<Us>(pos, ksq),
+ make_score(-VALUE_INFINITE, 0),
+ make_score(-VALUE_INFINITE, 0) };
+
+ // If we can castle use the bonus after castling if it is bigger
+ if (pos.can_castle(Us & KING_SIDE))
+ shelters[1] = evaluate_shelter<Us>(pos, relative_square(Us, SQ_G1));
- Value bonus = evaluate_shelter<Us>(pos, ksq);
+ if (pos.can_castle(Us & QUEEN_SIDE))
+ shelters[2] = evaluate_shelter<Us>(pos, relative_square(Us, SQ_C1));
- // If we can castle use the bonus after the castling if it is bigger
- if (pos.can_castle(Us | KING_SIDE))
- bonus = std::max(bonus, evaluate_shelter<Us>(pos, relative_square(Us, SQ_G1)));
+ for (int i : {1, 2})
+ if (mg_value(shelters[i]) > mg_value(shelters[0]))
+ shelters[0] = shelters[i];
+
+ // In endgame we like to bring our king near our closest pawn
+ Bitboard pawns = pos.pieces(Us, PAWN);
+ int minPawnDist = pawns ? 8 : 0;
- if (pos.can_castle(Us | QUEEN_SIDE))
- bonus = std::max(bonus, evaluate_shelter<Us>(pos, relative_square(Us, SQ_C1)));
+ if (pawns & PseudoAttacks[KING][ksq])
+ minPawnDist = 1;
+ else while (pawns)
+ minPawnDist = std::min(minPawnDist, distance(ksq, pop_lsb(&pawns)));
- return make_score(bonus, -16 * minKingPawnDistance);
+ return shelters[0] - make_score(0, 16 * minPawnDist);
}
// Explicit template instantiation
-template Score Entry::do_king_safety<WHITE>(const Position& pos, Square ksq);
-template Score Entry::do_king_safety<BLACK>(const Position& pos, Square ksq);
+template Score Entry::do_king_safety<WHITE>(const Position& pos);
+template Score Entry::do_king_safety<BLACK>(const Position& pos);
} // namespace Pawns
projects / stockfish / blobdiff