// king is on g8 and there's a white knight on g5, this knight adds
// 2 to kingAdjacentZoneAttacksCount[BLACK].
int kingAdjacentZoneAttacksCount[COLOR_NB];
+
+ Bitboard pinnedPieces[COLOR_NB];
};
// Evaluation grain size, must be a power of 2
}
- /// trace() is like evaluate() but instead of a value returns a string suitable
- /// to be print on stdout with the detailed descriptions and values of each
- /// evaluation term. Used mainly for debugging.
+ /// trace() is like evaluate(), but instead of returning a value, it returns
+ /// a string (suitable for outputting to stdout) that contains the detailed
+ /// descriptions and values of each evaluation term. It's mainly used for
+ /// debugging.
std::string trace(const Position& pos) {
return Tracing::do_trace(pos);
}
Thread* th = pos.this_thread();
// Initialize score by reading the incrementally updated scores included
- // in the position object (material + piece square tables) and adding
+ // in the position object (material + piece square tables) and adding a
// Tempo bonus. Score is computed from the point of view of white.
score = pos.psq_score() + (pos.side_to_move() == WHITE ? Tempo : -Tempo);
&& pos.opposite_bishops()
&& sf == SCALE_FACTOR_NORMAL)
{
- // Only the two bishops ?
+ // Ignoring any pawns, do both sides only have a single bishop and no
+ // other pieces ?
if ( pos.non_pawn_material(WHITE) == BishopValueMg
&& pos.non_pawn_material(BLACK) == BishopValueMg)
{
const Color Them = (Us == WHITE ? BLACK : WHITE);
const Square Down = (Us == WHITE ? DELTA_S : DELTA_N);
+ ei.pinnedPieces[Us] = pos.pinned_pieces(Us);
+
Bitboard b = ei.attackedBy[Them][KING] = pos.attacks_from<KING>(pos.king_square(Them));
ei.attackedBy[Us][PAWN] = ei.pi->pawn_attacks(Us);
: Piece == ROOK ? attacks_bb< ROOK>(s, pos.pieces() ^ pos.pieces(Us, ROOK, QUEEN))
: pos.attacks_from<Piece>(s);
+ if (ei.pinnedPieces[Us] & s)
+ b &= LineBB[pos.king_square(Us)][s];
+
ei.attackedBy[Us][Piece] |= b;
if (b & ei.kingRing[Them])
mobility[Us] += MobilityBonus[Piece][mob];
- // Decrease score if we are attacked by an enemy pawn. Remaining part
+ // Decrease score if we are attacked by an enemy pawn. The remaining part
// of threat evaluation must be done later when we have full attack info.
if (ei.attackedBy[Them][PAWN] & s)
score -= ThreatenedByPawn[Piece];
Square ksq = pos.king_square(Us);
- // Penalize rooks which are trapped inside a king. Penalize more if
- // king has lost right to castle.
+ // Penalize rooks which are trapped by a king. Penalize more if the
+ // king has lost its castling capability.
if ( ((file_of(ksq) < FILE_E) == (file_of(s) < file_of(ksq)))
&& (rank_of(ksq) == rank_of(s) || relative_rank(Us, ksq) == RANK_1)
&& !ei.pi->semiopen_on_side(Us, file_of(ksq), file_of(ksq) < FILE_E))
if ( ei.kingAttackersCount[Them] >= 2
&& ei.kingAdjacentZoneAttacksCount[Them])
{
- // Find the attacked squares around the king which has no defenders
+ // Find the attacked squares around the king which have no defenders
// apart from the king itself
undefended = ei.attackedBy[Them][ALL_PIECES]
& ei.attackedBy[Us][KING]
+ KingExposed[relative_square(Us, ksq)]
- mg_value(score) / 32;
- // Analyse enemy's safe queen contact checks. First find undefended
- // squares around the king attacked by enemy queen...
+ // Analyse the enemy's safe queen contact checks. Firstly, find the
+ // undefended squares around the king that are attacked by the enemy's
+ // queen...
b = undefended & ei.attackedBy[Them][QUEEN] & ~pos.pieces(Them);
if (b)
{
- // ...then remove squares not supported by another enemy piece
+ // ...and then remove squares not supported by another enemy piece
b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
| ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][ROOK]);
if (b)
* (Them == pos.side_to_move() ? 2 : 1);
}
- // Analyse enemy's safe rook contact checks. First find undefended
- // squares around the king attacked by enemy rooks...
+ // Analyse the enemy's safe rook contact checks. Firstly, find the
+ // undefended squares around the king that are attacked by the enemy's
+ // rooks...
b = undefended & ei.attackedBy[Them][ROOK] & ~pos.pieces(Them);
- // Consider only squares where the enemy rook gives check
+ // Consider only squares where the enemy's rook gives check
b &= PseudoAttacks[ROOK][ksq];
if (b)
{
- // ...then remove squares not supported by another enemy piece
+ // ...and then remove squares not supported by another enemy piece
b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
| ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][QUEEN]);
if (b)
* (Them == pos.side_to_move() ? 2 : 1);
}
- // Analyse enemy's safe distance checks for sliders and knights
+ // Analyse the enemy's safe distance checks for sliders and knights
safe = ~(pos.pieces(Them) | ei.attackedBy[Us][ALL_PIECES]);
b1 = pos.attacks_from<ROOK>(ksq) & safe;
Bitboard b, undefendedMinors, weakEnemies;
Score score = SCORE_ZERO;
- // Undefended minors get penalized even if not under attack
+ // Undefended minors get penalized even if they are not under attack
undefendedMinors = pos.pieces(Them, BISHOP, KNIGHT)
& ~ei.attackedBy[Them][ALL_PIECES];
{
Square blockSq = s + pawn_push(Us);
- // Adjust bonus based on kings proximity
+ // Adjust bonus based on the king's proximity
ebonus += Value(square_distance(pos.king_square(Them), blockSq) * 5 * rr)
- Value(square_distance(pos.king_square(Us ), blockSq) * 2 * rr);
if (relative_rank(Us, blockSq) != RANK_8)
ebonus -= Value(square_distance(pos.king_square(Us), blockSq + pawn_push(Us)) * rr);
- // If the pawn is free to advance, increase bonus
+ // If the pawn is free to advance, then increase the bonus
if (pos.empty(blockSq))
{
squaresToQueen = forward_bb(Us, s);
else
defendedSquares = squaresToQueen & ei.attackedBy[Us][ALL_PIECES];
- // If there aren't enemy attacks huge bonus, a bit smaller if at
- // least block square is not attacked, otherwise smallest bonus.
+ // If there aren't any enemy attacks, then assign a huge bonus.
+ // The bonus will be a bit smaller if at least the block square
+ // isn't attacked, otherwise assign the smallest possible bonus.
int k = !unsafeSquares ? 15 : !(unsafeSquares & blockSq) ? 9 : 3;
- // Big bonus if the path to queen is fully defended, a bit less
- // if at least block square is defended.
+ // Assign a big bonus if the path to the queen is fully defended,
+ // otherwise assign a bit less of a bonus if at least the block
+ // square is defended.
if (defendedSquares == squaresToQueen)
k += 6;
// evaluate_unstoppable_pawns() scores the most advanced among the passed and
// candidate pawns. In case opponent has no pieces but pawns, this is somewhat
- // related to the possibility pawns are unstoppable.
+ // related to the possibility that pawns are unstoppable.
Score evaluate_unstoppable_pawns(const Position& pos, Color us, const EvalInfo& ei) {
projects / stockfish / blobdiff