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
// 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
Score evaluate(const Position& pos, Pawns::Entry* e) {
constexpr Color Them = (Us == WHITE ? BLACK : WHITE);
- constexpr Direction Up = (Us == WHITE ? NORTH : SOUTH);
+ constexpr Direction Up = pawn_push(Us);
Bitboard neighbours, stoppers, support, phalanx, opposed;
- Bitboard lever, leverPush;
+ Bitboard lever, leverPush, blocked;
Square s;
bool backward, passed, doubled;
Score score = SCORE_ZERO;
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);
// Loop through all pawns of the current color and score each pawn
while ((s = *pl++) != SQ_NONE)
// 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)));
-
- // Span of backward pawns and span behind opposing pawns are not included
- // in the pawnAttacksSpan bitboard.
- if (!backward || phalanx)
- {
- if (opposed)
- e->pawnAttacksSpan[Us] |= pawn_attack_span(Us, s) &
- ~pawn_attack_span(Us, frontmost_sq(Them, opposed));
- else
- e->pawnAttacksSpan[Us] |= pawn_attack_span(Us, s);
- }
+ // 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
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 pawns will be properly scored later in evaluation when we have
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 shelters[3] = { evaluate_shelter<Us>(pos, ksq),
- make_score(-VALUE_INFINITE, 0),
- make_score(-VALUE_INFINITE, 0) };
+ 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))
- shelters[1] = evaluate_shelter<Us>(pos, relative_square(Us, SQ_G1));
+ shelter = std::max(shelter, evaluate_shelter<Us>(pos, relative_square(Us, SQ_G1)), compare);
if (pos.can_castle(Us & QUEEN_SIDE))
- shelters[2] = evaluate_shelter<Us>(pos, relative_square(Us, SQ_C1));
-
- for (int i : {1, 2})
- if (mg_value(shelters[i]) > mg_value(shelters[0]))
- shelters[0] = shelters[i];
+ 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);
else while (pawns)
minPawnDist = std::min(minPawnDist, distance(ksq, pop_lsb(&pawns)));
- return shelters[0] - make_score(0, 16 * minPawnDist);
+ return shelter - make_score(0, 16 * minPawnDist);
}
// Explicit template instantiation