// evaluate_king() assigns bonuses and penalties to a king of a given color
public static Score evaluate_king(Position pos, EvalInfo ei, Color Us, bool Trace)
{
Color Them = (Us == ColorS.WHITE ? ColorS.BLACK : ColorS.WHITE);
Bitboard undefended, b, b1, b2, safe;
int attackUnits;
Square ksq = pos.king_square(Us);
// King shelter and enemy pawns storm
Score score = ei.pi.king_safety(pos, ksq, Us);
// Main king safety evaluation
if (ei.kingAttackersCount[Them] != 0)
{
// Find the attacked squares around the king which have no defenders
// apart from the king itself
undefended = ei.attackedBy[Them][PieceTypeS.ALL_PIECES]
& ei.attackedBy[Us][PieceTypeS.KING]
& ~(ei.attackedBy[Us][PieceTypeS.PAWN] | ei.attackedBy[Us][PieceTypeS.KNIGHT]
| ei.attackedBy[Us][PieceTypeS.BISHOP] | ei.attackedBy[Us][PieceTypeS.ROOK]
| ei.attackedBy[Us][PieceTypeS.QUEEN]);
// Initialize the 'attackUnits' variable, which is used later on as an
// index to the KingDanger[] array. The initial value is based on the
// number and types of the enemy's attacking pieces, the number of
// attacked and undefended squares around our king and the quality of
// the pawn shelter (current 'score' value).
attackUnits = Math.Min(20, (ei.kingAttackersCount[Them] * ei.kingAttackersWeight[Them]) / 2)
+ 3 * (ei.kingAdjacentZoneAttacksCount[Them] + Bitcount.popcount_Max15(undefended))
+ 2 * (ei.pinnedPieces[Us] != 0 ? 1 : 0)
- Types.mg_value(score) / 32;
// 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][PieceTypeS.QUEEN] & ~pos.pieces_color(Them);
if (b != 0)
{
// ...and then remove squares not supported by another enemy piece
b &= (ei.attackedBy[Them][PieceTypeS.PAWN] | ei.attackedBy[Them][PieceTypeS.KNIGHT]
| ei.attackedBy[Them][PieceTypeS.BISHOP] | ei.attackedBy[Them][PieceTypeS.ROOK]);
if (b != 0)
{
attackUnits += QueenContactCheck
* Bitcount.popcount_Max15(b)
* (Them == pos.side_to_move() ? 2 : 1);
}
}
// 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][PieceTypeS.ROOK] & ~pos.pieces_color(Them);
// Consider only squares where the enemy rook gives check
b &= BitBoard.PseudoAttacks[PieceTypeS.ROOK][ksq];
if (b != 0)
{
// ...and then remove squares not supported by another enemy piece
b &= (ei.attackedBy[Them][PieceTypeS.PAWN] | ei.attackedBy[Them][PieceTypeS.KNIGHT]
| ei.attackedBy[Them][PieceTypeS.BISHOP] | ei.attackedBy[Them][PieceTypeS.QUEEN]);
if (b != 0)
{
attackUnits += RookContactCheck
* Bitcount.popcount_Max15(b)
* (Them == pos.side_to_move() ? 2 : 1);
}
}
// Analyse enemy's safe distance checks for sliders and knights
safe = ~(pos.pieces_color(Them) | ei.attackedBy[Us][PieceTypeS.ALL_PIECES]);
b1 = pos.attacks_from_square_piecetype(ksq, PieceTypeS.ROOK) & safe;
b2 = pos.attacks_from_square_piecetype(ksq, PieceTypeS.BISHOP) & safe;
// Enemy queen safe checks
b = (b1 | b2) & ei.attackedBy[Them][PieceTypeS.QUEEN];
if (b != 0)
{
attackUnits += QueenCheck * Bitcount.popcount_Max15(b);
}
// Enemy rooks safe checks
b = b1 & ei.attackedBy[Them][PieceTypeS.ROOK];
if (b != 0)
{
attackUnits += RookCheck * Bitcount.popcount_Max15(b);
}
// Enemy bishops safe checks
b = b2 & ei.attackedBy[Them][PieceTypeS.BISHOP];
if (b != 0)
{
attackUnits += BishopCheck * Bitcount.popcount_Max15(b);
}
// Enemy knights safe checks
b = pos.attacks_from_square_piecetype(ksq, PieceTypeS.KNIGHT) & ei.attackedBy[Them][PieceTypeS.KNIGHT] & safe;
if (b != 0)
{
attackUnits += KnightCheck * Bitcount.popcount_Max15(b);
}
// To index KingDanger[] attackUnits must be in [0, 99] range
attackUnits = Math.Min(99, Math.Max(0, attackUnits));
// Finally, extract the king danger score from the KingDanger[]
// array and subtract the score from evaluation.
score -= KingDanger[Us == Search.RootColor ? 1 : 0][attackUnits];
}
if (Trace)
{
Tracing.terms[Us][PieceTypeS.KING] = score;
}
return(score);
}
// evaluate_threats() assigns bonuses according to the type of attacking piece
// and the type of attacked one.
public static Score evaluate_threats(Position pos, EvalInfo ei, Color Us, bool Trace)
{
Color Them = (Us == ColorS.WHITE ? ColorS.BLACK : ColorS.WHITE);
Bitboard b, weakEnemies;
Score score = ScoreS.SCORE_ZERO;
// Enemies not defended by a pawn and under our attack
weakEnemies = pos.pieces_color(Them)
& ~ei.attackedBy[Them][PieceTypeS.PAWN]
& ei.attackedBy[Us][PieceTypeS.ALL_PIECES];
// Add a bonus according if the attacking pieces are minor or major
if (weakEnemies != 0)
{
b = weakEnemies & (ei.attackedBy[Us][PieceTypeS.PAWN] | ei.attackedBy[Us][PieceTypeS.KNIGHT] | ei.attackedBy[Us][PieceTypeS.BISHOP]);
if (b != 0)
{
score += Threat[0][Types.type_of_piece(pos.piece_on(BitBoard.lsb(b)))];
}
b = weakEnemies & (ei.attackedBy[Us][PieceTypeS.ROOK] | ei.attackedBy[Us][PieceTypeS.QUEEN]);
if (b != 0)
{
score += Threat[1][Types.type_of_piece(pos.piece_on(BitBoard.lsb(b)))];
}
b = weakEnemies & ~ei.attackedBy[Them][PieceTypeS.ALL_PIECES];
if (b != 0)
{
score += BitBoard.more_than_one(b) ? Hanging[Us != pos.side_to_move()?1:0] * Bitcount.popcount_Max15(b)
: Hanging[Us == pos.side_to_move()?1:0];
}
}
if (Trace)
{
Tracing.terms[Us][TermsS.THREAT] = score;
}
return(score);
}
// evaluate_pieces() assigns bonuses and penalties to the pieces of a given color
public static Score evaluate_pieces(Position pos, EvalInfo ei, Score[] mobility, Bitboard[] mobilityArea, PieceType Pt, Color Us, bool Trace)
{
if (Us == ColorS.WHITE && Pt == PieceTypeS.KING)
{
return(ScoreS.SCORE_ZERO);
}
Bitboard b;
Square s;
Score score = ScoreS.SCORE_ZERO;
PieceType NextPt = (Us == ColorS.WHITE ? Pt : (Pt + 1));
Color Them = (Us == ColorS.WHITE ? ColorS.BLACK : ColorS.WHITE);
Square[] pl = pos.list(Us, Pt);
int plPos = 0;
ei.attackedBy[Us][Pt] = 0;
while ((s = pl[plPos++]) != SquareS.SQ_NONE)
{
// Find attacked squares, including x-ray attacks for bishops and rooks
b = Pt == PieceTypeS.BISHOP ? BitBoard.attacks_bb_SBBPT(s, pos.pieces() ^ pos.pieces_color_piecetype(Us, PieceTypeS.QUEEN), PieceTypeS.BISHOP)
: Pt == PieceTypeS.ROOK ? BitBoard.attacks_bb_SBBPT(s, pos.pieces() ^ pos.pieces_color_piecetype(Us, PieceTypeS.ROOK, PieceTypeS.QUEEN), PieceTypeS.ROOK)
: pos.attacks_from_square_piecetype(s, Pt);
if ((ei.pinnedPieces[Us] & BitBoard.SquareBB[s]) != 0)
{
b &= BitBoard.LineBB[pos.king_square(Us)][s];
}
ei.attackedBy[Us][PieceTypeS.ALL_PIECES] |= ei.attackedBy[Us][Pt] |= b;
if ((b & ei.kingRing[Them]) != 0)
{
ei.kingAttackersCount[Us]++;
ei.kingAttackersWeight[Us] += KingAttackWeights[Pt];
Bitboard bb = (b & ei.attackedBy[Them][PieceTypeS.KING]);
if (bb != 0)
{
ei.kingAdjacentZoneAttacksCount[Us] += Bitcount.popcount_Max15(bb);
}
}
if (Pt == PieceTypeS.QUEEN)
{
b &= ~(ei.attackedBy[Them][PieceTypeS.KNIGHT]
| ei.attackedBy[Them][PieceTypeS.BISHOP]
| ei.attackedBy[Them][PieceTypeS.ROOK]);
}
int mob = (Pt != PieceTypeS.QUEEN ? Bitcount.popcount_Max15(b & mobilityArea[Us])
: Bitcount.popcount(b & mobilityArea[Us]));
mobility[Us] += MobilityBonus[Pt][mob];
// 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][PieceTypeS.PAWN] & BitBoard.SquareBB[s]) != 0)
{
score -= ThreatenedByPawn[Pt];
}
if (Pt == PieceTypeS.BISHOP || Pt == PieceTypeS.KNIGHT)
{
// Penalty for bishop with same coloured pawns
if (Pt == PieceTypeS.BISHOP)
{
score -= BishopPawns * ei.pi.pawns_on_same_color_squares(Us, s);
}
// Bishop and knight outposts squares
if (0 == (pos.pieces_color_piecetype(Them, PieceTypeS.PAWN) & BitBoard.pawn_attack_span(Us, s)))
{
score += evaluate_outposts(pos, ei, s, Pt, Us);
}
// Bishop or knight behind a pawn
if (Types.relative_rank_square(Us, s) < RankS.RANK_5 &&
(pos.pieces_piecetype(PieceTypeS.PAWN) & BitBoard.SquareBB[(s + Types.pawn_push(Us))]) != 0)
{
score += MinorBehindPawn;
}
}
if (Pt == PieceTypeS.ROOK)
{
// Rook piece attacking enemy pawns on the same rank/file
if (Types.relative_rank_square(Us, s) >= RankS.RANK_5)
{
Bitboard pawns = pos.pieces_color_piecetype(Them, PieceTypeS.PAWN) & BitBoard.PseudoAttacks[PieceTypeS.ROOK][s];
if (pawns != 0)
{
score += Bitcount.popcount_Max15(pawns) * RookOnPawn;
}
}
// Give a bonus for a rook on a open or semi-open file
if (ei.pi.semiopen_file(Us, Types.file_of(s)) != 0)
{
score += ei.pi.semiopen_file(Them, Types.file_of(s)) != 0 ? RookOpenFile : RookSemiopenFile;
}
if (mob > 3 || ei.pi.semiopen_file(Us, Types.file_of(s)) != 0)
{
continue;
}
Square ksq = pos.king_square(Us);
// Penalize rooks which are trapped by a king. Penalize more if the
// king has lost its castling capability.
if (((Types.file_of(ksq) < FileS.FILE_E) == (Types.file_of(s) < Types.file_of(ksq))) &&
(Types.rank_of(ksq) == Types.rank_of(s) || Types.relative_rank_square(Us, ksq) == RankS.RANK_1) &&
0 == ei.pi.semiopen_side(Us, Types.file_of(ksq), Types.file_of(s) < Types.file_of(ksq)))
{
score -= (TrappedRook - Types.make_score(mob * 8, 0)) * (1 + (pos.can_castle_color(Us) == 0 ? 1 : 0));
}
}
// An important Chess960 pattern: A cornered bishop blocked by a friendly
// pawn diagonally in front of it is a very serious problem, especially
// when that pawn is also blocked.
if (Pt == PieceTypeS.BISHOP &&
pos.is_chess960() != 0 &&
(s == Types.relative_square(Us, SquareS.SQ_A1) || s == Types.relative_square(Us, SquareS.SQ_H1)))
{
Square d = Types.pawn_push(Us) + (Types.file_of(s) == FileS.FILE_A ? SquareS.DELTA_E : SquareS.DELTA_W);
if (pos.piece_on(s + d) == Types.make_piece(Us, PieceTypeS.PAWN))
{
score -= !pos.empty(s + d + Types.pawn_push(Us)) ? TrappedBishopA1H1 * 4
: pos.piece_on(s + d + d) == Types.make_piece(Us, PieceTypeS.PAWN) ? TrappedBishopA1H1 * 2
: TrappedBishopA1H1;
}
}
}
if (Trace)
{
Tracing.terms[Us][Pt] = score;
}
return(score - evaluate_pieces(pos, ei, mobility, mobilityArea, NextPt, Them, Trace));
}
