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) 2015-2019 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
+ Copyright (C) 2015-2020 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
constexpr Score WeakLever = S( 0, 56);
constexpr Score WeakUnopposed = S(13, 27);
+ constexpr Score BlockedStorm[RANK_NB] = {S( 0, 0), S( 0, 0), S( 76, 78), S(-10, 15), S(-7, 10), S(-4, 6), S(-1, 2)};
+
// Connected pawn bonus
constexpr int Connected[RANK_NB] = { 0, 7, 8, 12, 29, 48, 86 };
// 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.
- // [0][1-2] accommodate opponent pawn on edge (likely blocked by 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(-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) }
+ { V( 85), V(-289), V(-166), V(97), V(50), V( 45), V( 50) },
+ { V( 46), V( -25), V( 122), V(45), V(37), V(-10), V( 20) },
+ { V( -6), V( 51), V( 168), V(34), V(-2), V(-22), V(-14) },
+ { V(-15), V( -11), V( 101), V( 4), V(11), V(-15), V(-29) }
};
#undef S
template<Color Us>
Score evaluate(const Position& pos, Pawns::Entry* e) {
- constexpr Color Them = (Us == WHITE ? BLACK : WHITE);
- constexpr Direction Up = (Us == WHITE ? NORTH : SOUTH);
+ constexpr Color Them = ~Us;
+ constexpr Direction Up = pawn_push(Us);
- Bitboard b, neighbours, stoppers, doubled, support, phalanx;
- Bitboard lever, leverPush;
+ Bitboard neighbours, stoppers, support, phalanx, opposed;
+ Bitboard lever, leverPush, blocked;
Square s;
- bool opposed, backward, passed;
+ bool backward, passed, doubled;
Score score = SCORE_ZERO;
const Square* pl = pos.squares<PAWN>(Us);
Bitboard doubleAttackThem = pawn_double_attacks_bb<Them>(theirPawns);
- e->passedPawns[Us] = e->pawnAttacksSpan[Us] = 0;
+ e->passedPawns[Us] = 0;
e->kingSquares[Us] = SQ_NONE;
- e->pawnAttacks[Us] = pawn_attacks_bb<Us>(ourPawns);
+ e->pawnAttacks[Us] = e->pawnAttacksSpan[Us] = pawn_attacks_bb<Us>(ourPawns);
+ e->blockedCount += popcount(shift<Up>(ourPawns) & (theirPawns | doubleAttackThem));
// Loop through all pawns of the current color and score each pawn
while ((s = *pl++) != SQ_NONE)
Rank r = relative_rank(Us, s);
- e->pawnAttacksSpan[Us] |= pawn_attack_span(Us, s);
-
// Flag the pawn
opposed = theirPawns & forward_file_bb(Us, s);
+ blocked = theirPawns & (s + Up);
stoppers = theirPawns & passed_pawn_span(Us, s);
lever = theirPawns & PawnAttacks[Us][s];
leverPush = theirPawns & PawnAttacks[Us][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 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)));
+ // the adjacent files and cannot safely advance.
+ backward = !(neighbours & forward_ranks_bb(Them, s + Up))
+ && (leverPush | blocked);
+
+ // Compute additional span if pawn is not backward nor blocked
+ if (!backward && !blocked)
+ e->pawnAttacksSpan[Us] |= pawn_attack_span(Us, s);
// 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.
+ // (Refined in Evaluation::passed)
passed = !(stoppers ^ lever)
|| ( !(stoppers ^ leverPush)
&& popcount(phalanx) >= popcount(leverPush))
- || ( stoppers == square_bb(s + Up) && r >= RANK_5
+ || ( stoppers == blocked && r >= RANK_5
&& (shift<Up>(support) & ~(theirPawns | doubleAttackThem)));
+ passed &= !(forward_file_bb(Us, s) & ourPawns);
+
// Passed pawns will be properly scored later in evaluation when we have
// full attack info.
if (passed)
// Score this pawn
if (support | phalanx)
{
- int v = Connected[r] * (phalanx ? 3 : 2) / (opposed ? 2 : 1)
- + 17 * popcount(support);
+ int v = Connected[r] * (4 + 2 * bool(phalanx) - 2 * bool(opposed) - bool(blocked)) / 2
+ + 21 * popcount(support);
score += make_score(v, v * (r - 2) / 4);
}
else if (!neighbours)
- score -= Isolated + WeakUnopposed * int(!opposed);
+ {
+ score -= Isolated
+ + WeakUnopposed * !opposed;
+
+ if ( (ourPawns & forward_file_bb(Them, s))
+ && popcount(opposed) == 1
+ && !(theirPawns & adjacent_files_bb(s)))
+ score -= Doubled;
+ }
else if (backward)
- score -= Backward + WeakUnopposed * int(!opposed);
+ score -= Backward
+ + WeakUnopposed * !opposed;
- if (doubled && !support)
- score -= Doubled;
+ if (!support)
+ score -= Doubled * doubled
+ + WeakLever * more_than_one(lever);
}
- // Penalize the unsupported and non passed pawns attacked twice by the enemy
- b = ourPawns
- & doubleAttackThem
- & ~(e->pawnAttacks[Us] | e->passedPawns[Us]);
- score -= WeakLever * popcount(b);
-
return score;
}
return e;
e->key = key;
+ e->blockedCount = 0;
e->scores[WHITE] = evaluate<WHITE>(pos, e);
e->scores[BLACK] = evaluate<BLACK>(pos, e);
/// penalty for a king, looking at the king file and the two closest files.
template<Color Us>
-void Entry::evaluate_shelter(const Position& pos, Square ksq, Score& shelter) {
+Score Entry::evaluate_shelter(const Position& pos, Square ksq) {
- constexpr Color Them = (Us == WHITE ? BLACK : WHITE);
+ constexpr Color Them = ~Us;
Bitboard b = pos.pieces(PAWN) & ~forward_ranks_bb(Them, ksq);
- Bitboard ourPawns = b & pos.pieces(Us);
+ Bitboard ourPawns = b & pos.pieces(Us) & ~pawnAttacks[Them];
Bitboard theirPawns = b & pos.pieces(Them);
Score bonus = make_score(5, 5);
- File center = clamp(file_of(ksq), FILE_B, FILE_G);
+ File center = Utility::clamp(file_of(ksq), FILE_B, FILE_G);
for (File f = File(center - 1); f <= File(center + 1); ++f)
{
b = ourPawns & file_bb(f);
- Rank ourRank = b ? relative_rank(Us, frontmost_sq(Them, b)) : RANK_1;
+ int ourRank = b ? relative_rank(Us, frontmost_sq(Them, b)) : 0;
b = theirPawns & file_bb(f);
- Rank theirRank = b ? relative_rank(Us, frontmost_sq(Them, b)) : RANK_1;
+ int theirRank = b ? relative_rank(Us, frontmost_sq(Them, b)) : 0;
- int d = std::min(f, ~f);
+ int d = edge_distance(f);
bonus += make_score(ShelterStrength[d][ourRank], 0);
if (ourRank && (ourRank == theirRank - 1))
- bonus -= make_score(82 * (theirRank == RANK_3), 82 * (theirRank == RANK_3));
+ bonus -= BlockedStorm[theirRank];
else
bonus -= make_score(UnblockedStorm[d][theirRank], 0);
}
- if (mg_value(bonus) > mg_value(shelter))
- shelter = bonus;
+ return bonus;
}
Square ksq = pos.square<KING>(Us);
kingSquares[Us] = ksq;
castlingRights[Us] = pos.castling_rights(Us);
+ auto compare = [](Score a, Score b) { return mg_value(a) < mg_value(b); };
+ Score shelter = evaluate_shelter<Us>(pos, ksq);
+
+ // If we can castle use the bonus after castling if it is bigger
+
+ if (pos.can_castle(Us & KING_SIDE))
+ shelter = std::max(shelter, evaluate_shelter<Us>(pos, relative_square(Us, SQ_G1)), compare);
+
+ if (pos.can_castle(Us & QUEEN_SIDE))
+ shelter = std::max(shelter, evaluate_shelter<Us>(pos, relative_square(Us, SQ_C1)), compare);
+
+ // In endgame we like to bring our king near our closest pawn
Bitboard pawns = pos.pieces(Us, PAWN);
- int minPawnDist = pawns ? 8 : 0;
+ int minPawnDist = 6;
if (pawns & PseudoAttacks[KING][ksq])
minPawnDist = 1;
-
else while (pawns)
minPawnDist = std::min(minPawnDist, distance(ksq, pop_lsb(&pawns)));
- Score shelter = make_score(-VALUE_INFINITE, VALUE_ZERO);
- evaluate_shelter<Us>(pos, ksq, shelter);
-
- // If we can castle use the bonus after the castling if it is bigger
- if (pos.can_castle(Us | KING_SIDE))
- evaluate_shelter<Us>(pos, relative_square(Us, SQ_G1), shelter);
-
- if (pos.can_castle(Us | QUEEN_SIDE))
- evaluate_shelter<Us>(pos, relative_square(Us, SQ_C1), shelter);
-
- return shelter - make_score(VALUE_ZERO, 16 * minPawnDist);
+ return shelter - make_score(0, 16 * minPawnDist);
}
// Explicit template instantiation
projects / stockfish / blobdiff