void evaluate_king(const Position& pos, EvalInfo& ei) {
const Color Them = (Us == WHITE ? BLACK : WHITE);
+
+ Bitboard undefended, attackedByOthers, escapeSquares, occ, b, b2, safe;
+ Square from, to;
+ bool sente;
+ int attackUnits, count, shelter = 0;
const Square s = pos.king_square(Us);
- int shelter = 0;
// King shelter
if (relative_rank(Us, s) <= RANK_4)
&& ei.kingAdjacentZoneAttacksCount[Them])
{
// Is it the attackers turn to move?
- bool sente = (Them == pos.side_to_move());
+ sente = (Them == pos.side_to_move());
// Find the attacked squares around the king which has no defenders
// apart from the king itself
- Bitboard undefended =
- ei.attacked_by(Them) & ~ei.attacked_by(Us, PAWN)
- & ~ei.attacked_by(Us, KNIGHT) & ~ei.attacked_by(Us, BISHOP)
- & ~ei.attacked_by(Us, ROOK) & ~ei.attacked_by(Us, QUEEN)
- & ei.attacked_by(Us, KING);
-
- Bitboard occ = pos.occupied_squares(), b, b2;
+ undefended = ei.attacked_by(Them) & ei.attacked_by(Us, KING);
+ undefended &= ~( ei.attacked_by(Us, PAWN) | ei.attacked_by(Us, KNIGHT)
+ | ei.attacked_by(Us, BISHOP) | ei.attacked_by(Us, ROOK)
+ | ei.attacked_by(Us, QUEEN));
// Initialize the 'attackUnits' variable, which is used later on as an
- // index to the SafetyTable[] array. The initial value is based on the
+ // index to the SafetyTable[] array. The initial value is based on the
// number and types of the attacking pieces, the number of attacked and
// undefended squares around the king, the square of the king, and the
// quality of the pawn shelter.
- int attackUnits =
- Min((ei.kingAttackersCount[Them] * ei.kingAttackersWeight[Them]) / 2, 25)
- + (ei.kingAdjacentZoneAttacksCount[Them] + count_1s_max_15<HasPopCnt>(undefended)) * 3
- + InitKingDanger[relative_square(Us, s)] - (shelter >> 5);
+ attackUnits = Min(25, (ei.kingAttackersCount[Them] * ei.kingAttackersWeight[Them]) / 2)
+ + 3 * (ei.kingAdjacentZoneAttacksCount[Them] + count_1s_max_15<HasPopCnt>(undefended))
+ + InitKingDanger[relative_square(Us, s)]
+ - (shelter >> 5);
// Analyse safe queen contact checks
b = undefended & ei.attacked_by(Them, QUEEN) & ~pos.pieces_of_color(Them);
if (b)
{
- Bitboard attackedByOthers =
- ei.attacked_by(Them, PAWN) | ei.attacked_by(Them, KNIGHT)
- | ei.attacked_by(Them, BISHOP) | ei.attacked_by(Them, ROOK);
+ attackedByOthers = ei.attacked_by(Them, PAWN) | ei.attacked_by(Them, KNIGHT)
+ | ei.attacked_by(Them, BISHOP) | ei.attacked_by(Them, ROOK);
b &= attackedByOthers;
+
+ // Squares attacked by the queen and supported by another enemy piece and
+ // not defended by other pieces but our king.
if (b)
{
- // The bitboard b now contains the squares available for safe queen
- // contact checks.
- int count = count_1s_max_15<HasPopCnt>(b);
- attackUnits += QueenContactCheckBonus * count * (sente ? 2 : 1);
-
- // Is there a mate threat?
- if (QueenContactMates && !pos.is_check())
- {
- Bitboard escapeSquares =
- pos.attacks_from<KING>(s) & ~pos.pieces_of_color(Us) & ~attackedByOthers;
-
- while (b)
+ // The bitboard b now contains the squares available for safe queen
+ // contact checks.
+ count = count_1s_max_15<HasPopCnt>(b);
+ attackUnits += QueenContactCheckBonus * count * (sente ? 2 : 1);
+
+ // Is there a mate threat?
+ if (QueenContactMates && !pos.is_check())
{
- Square from, to = pop_1st_bit(&b);
- if (!(escapeSquares & ~queen_attacks_bb(to, occ & ClearMaskBB[s])))
+ escapeSquares = pos.attacks_from<KING>(s) & ~pos.pieces_of_color(Us) & ~attackedByOthers;
+ occ = pos.occupied_squares();
+ while (b)
{
- // We have a mate, unless the queen is pinned or there
- // is an X-ray attack through the queen.
- for (int i = 0; i < pos.piece_count(Them, QUEEN); i++)
- {
- from = pos.piece_list(Them, QUEEN, i);
- if ( bit_is_set(pos.attacks_from<QUEEN>(from), to)
- && !bit_is_set(pos.pinned_pieces(Them), from)
- && !(rook_attacks_bb(to, occ & ClearMaskBB[from]) & pos.pieces(ROOK, QUEEN, Us))
- && !(bishop_attacks_bb(to, occ & ClearMaskBB[from]) & pos.pieces(BISHOP, QUEEN, Us)))
+ to = pop_1st_bit(&b);
- ei.mateThreat[Them] = make_move(from, to);
+ // Do we have escape squares from queen contact check attack ?
+ if (!(escapeSquares & ~queen_attacks_bb(to, occ & ClearMaskBB[s])))
+ {
+ // We have a mate, unless the queen is pinned or there
+ // is an X-ray attack through the queen.
+ for (int i = 0; i < pos.piece_count(Them, QUEEN); i++)
+ {
+ from = pos.piece_list(Them, QUEEN, i);
+ if ( bit_is_set(pos.attacks_from<QUEEN>(from), to)
+ && !bit_is_set(pos.pinned_pieces(Them), from)
+ && !(rook_attacks_bb(to, occ & ClearMaskBB[from]) & pos.pieces(ROOK, QUEEN, Us))
+ && !(bishop_attacks_bb(to, occ & ClearMaskBB[from]) & pos.pieces(BISHOP, QUEEN, Us)))
+
+ // Set the mate threat move
+ ei.mateThreat[Them] = make_move(from, to);
+ }
}
}
}
- }
}
}
// Analyse safe distance checks
+ safe = ~(pos.pieces_of_color(Them) | ei.attacked_by(Us));
+
if (QueenCheckBonus > 0 || RookCheckBonus > 0)
{
- b = pos.attacks_from<ROOK>(s) & ~pos.pieces_of_color(Them) & ~ei.attacked_by(Us);
+ b = pos.attacks_from<ROOK>(s) & safe;
// Queen checks
b2 = b & ei.attacked_by(Them, QUEEN);
}
if (QueenCheckBonus > 0 || BishopCheckBonus > 0)
{
- b = pos.attacks_from<BISHOP>(s) & ~pos.pieces_of_color(Them) & ~ei.attacked_by(Us);
+ b = pos.attacks_from<BISHOP>(s) & safe;
// Queen checks
b2 = b & ei.attacked_by(Them, QUEEN);
}
if (KnightCheckBonus > 0)
{
- b = pos.attacks_from<KNIGHT>(s) & ~pos.pieces_of_color(Them) & ~ei.attacked_by(Us);
+ b = pos.attacks_from<KNIGHT>(s) & safe;
// Knight checks
b2 = b & ei.attacked_by(Them, KNIGHT);
// adding pawns later).
if (DiscoveredCheckBonus)
{
- b = pos.discovered_check_candidates(Them) & ~pos.pieces(PAWN);
- if (b)
- attackUnits += DiscoveredCheckBonus * count_1s_max_15<HasPopCnt>(b) * (sente ? 2 : 1);
+ b = pos.discovered_check_candidates(Them) & ~pos.pieces(PAWN);
+ if (b)
+ attackUnits += DiscoveredCheckBonus * count_1s_max_15<HasPopCnt>(b) * (sente ? 2 : 1);
}
- // Has a mate threat been found? We don't do anything here if the
+ // Has a mate threat been found? We don't do anything here if the
// side with the mating move is the side to move, because in that
// case the mating side will get a huge bonus at the end of the main
// evaluation function instead.
attackUnits += MateThreatBonus;
// Ensure that attackUnits is between 0 and 99, in order to avoid array
- // out of bounds errors:
- if (attackUnits < 0)
- attackUnits = 0;
-
- if (attackUnits >= 100)
- attackUnits = 99;
+ // out of bounds errors.
+ attackUnits = Min(99, Max(0, attackUnits));
// Finally, extract the king safety score from the SafetyTable[] array.
- // Add the score to the evaluation, and also to ei.futilityMargin. The
+ // Add the score to the evaluation, and also to ei.futilityMargin. The
// reason for adding the king safety score to the futility margin is
// that the king safety scores can sometimes be very big, and that
// capturing a single attacking piece can therefore result in a score
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