ScaleFactor ScalingFunction<KPsK>::apply(const Position& pos) const {
assert(pos.non_pawn_material(strongerSide) == VALUE_ZERO);
assert(pos.piece_count(strongerSide, PAWN) >= 2);
assert(pos.non_pawn_material(weakerSide) == VALUE_ZERO);
assert(pos.piece_count(weakerSide, PAWN) == 0);
Square ksq = pos.king_square(weakerSide);
Bitboard pawns = pos.pieces(PAWN, strongerSide);
// Are all pawns on the 'a' file?
if ((pawns & ~FileABB) == EmptyBoardBB)
{
// Does the defending king block the pawns?
if ( square_distance(ksq, relative_square(strongerSide, SQ_A8)) <= 1
|| ( square_file(ksq) == FILE_A
&& (in_front_bb(strongerSide, ksq) & pawns) == EmptyBoardBB))
return SCALE_FACTOR_ZERO;
}
// Are all pawns on the 'h' file?
else if ((pawns & ~FileHBB) == EmptyBoardBB)
{
// Does the defending king block the pawns?
if ( square_distance(ksq, relative_square(strongerSide, SQ_H8)) <= 1
|| ( square_file(ksq) == FILE_H
&& (in_front_bb(strongerSide, ksq) & pawns) == EmptyBoardBB))
return SCALE_FACTOR_ZERO;
}
return SCALE_FACTOR_NONE;
}
Score Entry::do_king_safety(const Position& pos, Square ksq) {
kingSquares[Us] = ksq;
castlingRights[Us] = pos.can_castle(Us);
int minKingPawnDistance = 0;
#ifdef THREECHECK
CheckCount checks = pos.is_three_check() ? pos.checks_given(~Us) : CHECKS_0;
#endif
Bitboard pawns = pos.pieces(Us, PAWN);
if (pawns)
while (!(DistanceRingBB[ksq][minKingPawnDistance++] & pawns)) {}
Value bonus = shelter_storm<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)));
if (pos.can_castle(MakeCastling<Us, QUEEN_SIDE>::right))
bonus = std::max(bonus, shelter_storm<Us>(pos, relative_square(Us, SQ_C1)));
#ifdef THREECHECK
// Decrease score when checks have been taken
return make_score(bonus, (-16 * minKingPawnDistance) + (-2 * checks));
#else
return make_score(bonus, -16 * minKingPawnDistance);
#endif
}
Score Entry::do_king_safety(const Position& pos, Square ksq) {
kingSquares[Us] = ksq;
castlingRights[Us] = pos.can_castle(Us);
int minKingPawnDistance = 0;
Bitboard pawns = pos.pieces(Us, PAWN);
if (pawns)
while (!(DistanceRingBB[ksq][minKingPawnDistance++] & pawns)) {}
Value bonus = shelter_storm<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)));
if (pos.can_castle(MakeCastling<Us, QUEEN_SIDE>::right))
bonus = std::max(bonus, shelter_storm<Us>(pos, relative_square(Us, SQ_C1)));
return make_score(bonus, -16 * minKingPawnDistance);
}
ScaleFactor ScalingFunction<KNPK>::apply(const Position& pos) const {
assert(pos.non_pawn_material(strongerSide) == KnightValueMidgame);
assert(pos.piece_count(strongerSide, KNIGHT) == 1);
assert(pos.piece_count(strongerSide, PAWN) == 1);
assert(pos.non_pawn_material(weakerSide) == VALUE_ZERO);
assert(pos.piece_count(weakerSide, PAWN) == 0);
Square pawnSq = pos.piece_list(strongerSide, PAWN, 0);
Square weakerKingSq = pos.king_square(weakerSide);
if ( pawnSq == relative_square(strongerSide, SQ_A7)
&& square_distance(weakerKingSq, relative_square(strongerSide, SQ_A8)) <= 1)
return SCALE_FACTOR_ZERO;
if ( pawnSq == relative_square(strongerSide, SQ_H7)
&& square_distance(weakerKingSq, relative_square(strongerSide, SQ_H8)) <= 1)
return SCALE_FACTOR_ZERO;
return SCALE_FACTOR_NONE;
}
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;
Bitboard pawns = pos.pieces(Us, PAWN);
if (pawns)
while (!(DistanceRingBB[ksq][++minKingPawnDistance] & pawns)) {}
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(Us | KING_SIDE))
bonus = std::max(bonus, evaluate_shelter<Us>(pos, relative_square(Us, SQ_G1)));
if (pos.can_castle(Us | QUEEN_SIDE))
bonus = std::max(bonus, evaluate_shelter<Us>(pos, relative_square(Us, SQ_C1)));
return make_score(bonus, -16 * minKingPawnDistance);
}
Score Entry::update_safety(const Position& pos, Square ksq) {
kingSquares[Us] = ksq;
castleRights[Us] = pos.can_castle(Us);
minKPdistance[Us] = 0;
Bitboard pawns = pos.pieces(Us, PAWN);
if (pawns)
while (!(DistanceRingsBB[ksq][minKPdistance[Us]++] & pawns)) {}
if (relative_rank(Us, ksq) > RANK_4)
return kingSafety[Us] = make_score(0, -16 * minKPdistance[Us]);
Value bonus = shelter_storm<Us>(pos, ksq);
// If we can castle use the bonus after the castle if is bigger
if (pos.can_castle(make_castle_right(Us, KING_SIDE)))
bonus = std::max(bonus, shelter_storm<Us>(pos, relative_square(Us, SQ_G1)));
if (pos.can_castle(make_castle_right(Us, QUEEN_SIDE)))
bonus = std::max(bonus, shelter_storm<Us>(pos, relative_square(Us, SQ_C1)));
return kingSafety[Us] = make_score(bonus, -16 * minKPdistance[Us]);
}
ScaleFactor ScalingFunction<KBPsK>::apply(const Position& pos) const {
assert(pos.non_pawn_material(strongerSide) == BishopValueMidgame);
assert(pos.piece_count(strongerSide, BISHOP) == 1);
assert(pos.piece_count(strongerSide, PAWN) >= 1);
// No assertions about the material of weakerSide, because we want draws to
// be detected even when the weaker side has some pawns.
Bitboard pawns = pos.pieces(PAWN, strongerSide);
File pawnFile = square_file(pos.piece_list(strongerSide, PAWN, 0));
// All pawns are on a single rook file ?
if ( (pawnFile == FILE_A || pawnFile == FILE_H)
&& (pawns & ~file_bb(pawnFile)) == EmptyBoardBB)
{
Square bishopSq = pos.piece_list(strongerSide, BISHOP, 0);
Square queeningSq = relative_square(strongerSide, make_square(pawnFile, RANK_8));
Square kingSq = pos.king_square(weakerSide);
if ( !same_color_squares(queeningSq, bishopSq)
&& file_distance(square_file(kingSq), pawnFile) <= 1)
{
// The bishop has the wrong color, and the defending king is on the
// file of the pawn(s) or the neighboring file. Find the rank of the
// frontmost pawn.
Rank rank;
if (strongerSide == WHITE)
{
for (rank = RANK_7; (rank_bb(rank) & pawns) == EmptyBoardBB; rank--) {}
assert(rank >= RANK_2 && rank <= RANK_7);
}
else
{
for (rank = RANK_2; (rank_bb(rank) & pawns) == EmptyBoardBB; rank++) {}
rank = Rank(rank ^ 7); // HACK to get the relative rank
assert(rank >= RANK_2 && rank <= RANK_7);
}
// If the defending king has distance 1 to the promotion square or
// is placed somewhere in front of the pawn, it's a draw.
if ( square_distance(kingSq, queeningSq) <= 1
|| relative_rank(strongerSide, kingSq) >= rank)
return SCALE_FACTOR_ZERO;
}
}
return SCALE_FACTOR_NONE;
}
