internal static ExtMoveArrayWrapper generate_castling(
CastlingRight Cr,
bool Checks,
bool Chess960,
Position pos,
ExtMoveArrayWrapper moveList,
ColorT us,
CheckInfo ci)
{
var KingSide = (Cr == CastlingRight.WHITE_OO || Cr == CastlingRight.BLACK_OO);
if (pos.castling_impeded(Cr) || !pos.can_castle(Cr))
{
return moveList;
}
// After castling, the rook and king final positions are the same in Chess960
// as they would be in standard chess.
var kfrom = pos.square(PieceType.KING, us);
var rfrom = pos.castling_rook_square(Cr);
var kto = Square.relative_square(us, KingSide ? Square.SQ_G1 : Square.SQ_C1);
var enemies = pos.pieces_Ct(Color.opposite(us));
Debug.Assert(pos.checkers() == 0);
var K = Chess960 ? kto > kfrom ? Square.DELTA_W : Square.DELTA_E : KingSide ? Square.DELTA_W : Square.DELTA_E;
for (var s = kto; s != kfrom; s += K)
{
if ((pos.attackers_to(s) & enemies) != 0)
{
return moveList;
}
}
// Because we generate only legal castling moves we need to verify that
// when moving the castling rook we do not discover some hidden checker.
// For instance an enemy queen in SQ_A1 when castling rook is in SQ_B1.
if (Chess960
&& ((Utils.attacks_bb_PtSBb(PieceType.ROOK, kto, Bitboard.XorWithSquare(pos.pieces(), rfrom))
& pos.pieces_CtPtPt(Color.opposite(us), PieceType.ROOK, PieceType.QUEEN)))!= 0)
{
return moveList;
}
var m = Move.make(MoveType.CASTLING, kfrom, rfrom);
if (Checks && !pos.gives_check(m, ci))
{
return moveList;
}
moveList.Add(m);
return moveList;
}
/// Entry::shelter_storm() calculates shelter and storm penalties for the file
/// the king is on, as well as the two adjacent files.
private ValueT shelter_storm(ColorT Us, Position pos, SquareT ksq)
{
const int NoFriendlyPawn = 0;
const int Unblocked = 1;
const int BlockedByPawn = 2;
const int BlockedByKing = 3;
var Them = (Us == Color.WHITE ? Color.BLACK : Color.WHITE);
var b = pos.pieces_Pt(PieceType.PAWN) & (Utils.in_front_bb(Us, Square.rank_of(ksq)) | Utils.rank_bb_St(ksq));
var ourPawns = b & pos.pieces_Ct(Us);
var theirPawns = b & pos.pieces_Ct(Them);
var safety = MaxSafetyBonus;
var center = File.Create(Math.Max(File.FILE_B, Math.Min(File.FILE_G, Square.file_of(ksq))));
for (var f = center - 1; f <= (int)center + 1; ++f)
{
b = ourPawns & Utils.file_bb_Ft(File.Create(f));
var rkUs = b != 0 ? Rank.relative_rank_CtSt(Us, Utils.backmost_sq(Us, b)) : Rank.RANK_1;
b = theirPawns & Utils.file_bb_Ft(File.Create(f));
var rkThem = b != 0 ? Rank.relative_rank_CtSt(Us, Utils.frontmost_sq(Them, b)) : Rank.RANK_1;
safety -= ShelterWeakness[Math.Min(f, File.FILE_H - f)][rkUs]
+ StormDanger[
f == (int)Square.file_of(ksq) && rkThem == Rank.relative_rank_CtSt(Us, ksq) + 1
? BlockedByKing
: (int)rkUs == Rank.RANK_1
? NoFriendlyPawn
: rkThem == rkUs + 1 ? BlockedByPawn : Unblocked][Math.Min(f, File.FILE_H - f)][rkThem];
}
return safety;
}
// Helper used to detect a given material distribution
private static bool is_KXK(Position pos, ColorT us)
{
return !Bitboard.more_than_one(pos.pieces_Ct(Color.opposite(us))) && pos.non_pawn_material(us) >= Value.RookValueMg;
}
internal static ExtMoveArrayWrapper generate_pawn_moves(
ColorT Us,
GenType Type,
Position pos,
ExtMoveArrayWrapper moveList,
BitboardT target,
CheckInfo ci)
{
// Compute our parametrized parameters at compile time, named according to
// the point of view of white side.
var Them = (Us == Color.WHITE ? Color.BLACK : Color.WHITE);
var TRank8BB = (Us == Color.WHITE ? Bitboard.Rank8BB : Bitboard.Rank1BB);
var TRank7BB = (Us == Color.WHITE ? Bitboard.Rank7BB : Bitboard.Rank2BB);
var TRank3BB = (Us == Color.WHITE ? Bitboard.Rank3BB : Bitboard.Rank6BB);
var Up = (Us == Color.WHITE ? Square.DELTA_N : Square.DELTA_S);
var Right = (Us == Color.WHITE ? Square.DELTA_NE : Square.DELTA_SW);
var Left = (Us == Color.WHITE ? Square.DELTA_NW : Square.DELTA_SE);
var emptySquares = Bitboard.Create(0);
var pawnsOn7 = pos.pieces_CtPt(Us, PieceType.PAWN) & TRank7BB;
var pawnsNotOn7 = pos.pieces_CtPt(Us, PieceType.PAWN) & ~TRank7BB;
var enemies = (Type == GenType.EVASIONS
? pos.pieces_Ct(Them) & target
: Type == GenType.CAPTURES ? target : pos.pieces_Ct(Them));
// Single and double pawn pushes, no promotions
if (Type != GenType.CAPTURES)
{
emptySquares = (Type == GenType.QUIETS || Type == GenType.QUIET_CHECKS ? target : ~pos.pieces());
var b1 = Bitboard.shift_bb(Up, pawnsNotOn7) & emptySquares;
var b2 = Bitboard.shift_bb(Up, b1 & TRank3BB) & emptySquares;
if (Type == GenType.EVASIONS) // Consider only blocking squares
{
b1 &= target;
b2 &= target;
}
if (Type == GenType.QUIET_CHECKS)
{
b1 &= pos.attacks_from_PS(PieceType.PAWN, ci.ksq, Them);
b2 &= pos.attacks_from_PS(PieceType.PAWN, ci.ksq, Them);
// Add pawn pushes which give discovered check. This is possible only
// if the pawn is not on the same file as the enemy king, because we
// don't generate captures. Note that a possible discovery check
// promotion has been already generated amongst the captures.
if ((pawnsNotOn7 & ci.dcCandidates) != 0)
{
var dc1 = Bitboard.shift_bb(Up, pawnsNotOn7 & ci.dcCandidates) & emptySquares
& ~Utils.file_bb_St(ci.ksq);
var dc2 = Bitboard.shift_bb(Up, dc1 & TRank3BB) & emptySquares;
b1 |= dc1;
b2 |= dc2;
}
}
while (b1 != 0)
{
var to = Utils.pop_lsb(ref b1);
(moveList).Add(Move.make_move(to - Up, to));
}
while (b2 != 0)
{
var to = Utils.pop_lsb(ref b2);
(moveList).Add(Move.make_move(to - Up - Up, to));
}
}
// Promotions and underpromotions
if (pawnsOn7 != 0 && (Type != GenType.EVASIONS || ((target & TRank8BB) != 0)))
{
if (Type == GenType.CAPTURES)
{
emptySquares = ~pos.pieces();
}
if (Type == GenType.EVASIONS)
{
emptySquares &= target;
}
var b1 = Bitboard.shift_bb(Right, pawnsOn7) & enemies;
var b2 = Bitboard.shift_bb(Left, pawnsOn7) & enemies;
var b3 = Bitboard.shift_bb(Up, pawnsOn7) & emptySquares;
while (b1 != 0)
{
moveList = make_promotions(Type, Right, moveList, Utils.pop_lsb(ref b1), ci);
}
while (b2 != 0)
{
moveList = make_promotions(Type, Left, moveList, Utils.pop_lsb(ref b2), ci);
}
while (b3 != 0)
{
moveList = make_promotions(Type, Up, moveList, Utils.pop_lsb(ref b3), ci);
}
}
// Standard and en-passant captures
if (Type == GenType.CAPTURES || Type == GenType.EVASIONS || Type == GenType.NON_EVASIONS)
{
var b1 = Bitboard.shift_bb(Right, pawnsNotOn7) & enemies;
var b2 = Bitboard.shift_bb(Left, pawnsNotOn7) & enemies;
while (b1 != 0)
{
var to = Utils.pop_lsb(ref b1);
(moveList).Add(Move.make_move(to - Right, to));
}
while (b2 != 0)
{
var to = Utils.pop_lsb(ref b2);
(moveList).Add(Move.make_move(to - Left, to));
}
if (pos.ep_square() != Square.SQ_NONE)
{
Debug.Assert(Square.rank_of(pos.ep_square()) == Rank.relative_rank_CtRt(Us, Rank.RANK_6));
// An en passant capture can be an evasion only if the checking piece
// is the double pushed pawn and so is in the target. Otherwise this
// is a discovery check and we are forced to do otherwise.
if (Type == GenType.EVASIONS && Bitboard.AndWithSquare(target, (pos.ep_square() - Up))==0)
{
return moveList;
}
b1 = pawnsNotOn7 & pos.attacks_from_PS(PieceType.PAWN, pos.ep_square(), Them);
Debug.Assert(b1 != 0);
while (b1 != 0)
{
(moveList).Add(Move.make(MoveType.ENPASSANT, Utils.pop_lsb(ref b1), pos.ep_square()));
}
}
}
return moveList;
}
/// generate
/// EVASIONS
/// generates all pseudo-legal check evasions when the side
/// to move is in check. Returns a pointer to the end of the move list.
private static ExtMoveArrayWrapper generate_EVASIONS(Position pos, ExtMoveArrayWrapper moveList)
{
Debug.Assert(pos.checkers() != 0);
var us = pos.side_to_move();
var ksq = pos.square(PieceType.KING, us);
var sliderAttacks = Bitboard.Create(0);
var sliders = pos.checkers() & ~pos.pieces_PtPt(PieceType.KNIGHT, PieceType.PAWN);
// Find all the squares attacked by slider checkers. We will remove them from
// the king evasions in order to skip known illegal moves, which avoids any
// useless legality checks later on.
while (sliders != 0)
{
var checksq1 = Utils.pop_lsb(ref sliders);
sliderAttacks |= Bitboard.XorWithSquare(Utils.LineBB[checksq1, ksq], checksq1);
}
// Generate evasions for king, capture and non capture moves
var b = pos.attacks_from_PtS(PieceType.KING, ksq) & ~pos.pieces_Ct(us) & ~sliderAttacks;
while (b != 0)
{
(moveList).Add(Move.make_move(ksq, Utils.pop_lsb(ref b)));
}
if (Bitboard.more_than_one(pos.checkers()))
{
return moveList; // Double check, only a king move can save the day
}
// Generate blocking evasions or captures of the checking piece
var checksq = Utils.lsb(pos.checkers());
var target = Bitboard.OrWithSquare(Utils.between_bb(checksq, ksq), checksq);
return us == Color.WHITE
? generate_all(Color.WHITE, GenType.EVASIONS, pos, moveList, target)
: generate_all(Color.BLACK, GenType.EVASIONS, pos, moveList, target);
}
internal static ExtMoveArrayWrapper generate(GenType Type, Position pos, ExtMoveArrayWrapper moveList)
{
switch (Type)
{
case GenType.EVASIONS:
return generate_EVASIONS(pos, moveList);
case GenType.LEGAL:
return generate_LEGAL(pos, moveList);
case GenType.QUIET_CHECKS:
return generate_QUIET_CHECKS(pos, moveList);
}
Debug.Assert(Type == GenType.CAPTURES || Type == GenType.QUIETS || Type == GenType.NON_EVASIONS);
Debug.Assert(pos.checkers() == 0);
var us = pos.side_to_move();
var target = Type == GenType.CAPTURES
? pos.pieces_Ct(Color.opposite(us))
: Type == GenType.QUIETS
? ~pos.pieces()
: Type == GenType.NON_EVASIONS ? ~pos.pieces_Ct(us) : Bitboard.Create(0);
return us == Color.WHITE
? generate_all(Color.WHITE, Type, pos, moveList, target)
: generate_all(Color.BLACK, Type, pos, moveList, target);
}
// evaluate_passed_pawns() evaluates the passed pawns of the given color
private static ScoreT evaluate_passed_pawns(ColorT Us, bool DoTrace, Position pos, EvalInfo ei)
{
var Them = (Us == Color.WHITE ? Color.BLACK : Color.WHITE);
var score = Score.SCORE_ZERO;
var b = ei.pi.passed_pawns(Us);
while (b!=0)
{
var s = Utils.pop_lsb(ref b);
Debug.Assert(pos.pawn_passed(Us, s));
int r = Rank.relative_rank_CtSt(Us, s) - Rank.RANK_2;
var rr = r*(r - 1);
ValueT mbonus = Passed[(int) Phase.MG][r], ebonus = Passed[(int) Phase.EG][r];
if (rr != 0)
{
var blockSq = s + Square.pawn_push(Us);
// Adjust bonus based on the king's proximity
ebonus += Utils.distance_Square(pos.square(PieceType.KING, Them), blockSq)*5*rr
- Utils.distance_Square(pos.square(PieceType.KING, Us), blockSq)*2*rr;
// If blockSq is not the queening square then consider also a second push
if (Rank.relative_rank_CtSt(Us, blockSq) != Rank.RANK_8)
{
ebonus -= Utils.distance_Square(pos.square(PieceType.KING, Us), blockSq + Square.pawn_push(Us))*rr;
}
// If the pawn is free to advance, then increase the bonus
if (pos.empty(blockSq))
{
// If there is a rook or queen attacking/defending the pawn from behind,
// consider all the squaresToQueen. Otherwise consider only the squares
// in the pawn's path attacked or occupied by the enemy.
BitboardT squaresToQueen;
BitboardT unsafeSquares;
var defendedSquares = unsafeSquares = squaresToQueen = Utils.forward_bb(Us, s);
var bb = Utils.forward_bb(Them, s) & pos.pieces_PtPt(PieceType.ROOK, PieceType.QUEEN)
& pos.attacks_from_PtS(PieceType.ROOK, s);
if ((pos.pieces_Ct(Us) & bb)==0)
{
defendedSquares &= ei.attackedBy[Us, PieceType.ALL_PIECES];
}
if ((pos.pieces_Ct(Them) & bb) == 0)
{
unsafeSquares &= ei.attackedBy[Them, PieceType.ALL_PIECES] | pos.pieces_Ct(Them);
}
// If there aren't any enemy attacks, assign a big bonus. Otherwise
// assign a smaller bonus if the block square isn't attacked.
var k = unsafeSquares == 0 ? 18 : Bitboard.AndWithSquare(unsafeSquares, blockSq)==0 ? 8 : 0;
// If the path to queen is fully defended, assign a big bonus.
// Otherwise assign a smaller bonus if the block square is defended.
if (defendedSquares == squaresToQueen)
{
k += 6;
}
else if (Bitboard.AndWithSquare(defendedSquares, blockSq)!=0)
{
k += 4;
}
mbonus += k*rr;
ebonus += k*rr;
}
else if (Bitboard.AndWithSquare(pos.pieces_Ct(Us), blockSq)!=0)
{
mbonus += rr*3 + r*2 + 3;
ebonus += rr + r*2;
}
} // rr != 0
if (pos.count(PieceType.PAWN, Us) < pos.count(PieceType.PAWN, Them))
{
ebonus += ebonus/4;
}
score += Score.make_score(mbonus, ebonus) + PassedFile[Square.file_of(s)];
}
if (DoTrace)
{
add_IdxCtSt((int) Term.PASSED, Us, Score.Multiply(score, Weights[PassedPawns]));
}
// Add the scores to the middlegame and endgame eval
return Score.Multiply(score, Weights[PassedPawns]);
}
// evaluate_threats() assigns bonuses according to the type of attacking piece
// and the type of attacked one.
private static ScoreT evaluate_threats(ColorT Us, bool DoTrace, Position pos, EvalInfo ei)
{
var Them = (Us == Color.WHITE ? Color.BLACK : Color.WHITE);
var Up = (Us == Color.WHITE ? Square.DELTA_N : Square.DELTA_S);
var Left = (Us == Color.WHITE ? Square.DELTA_NW : Square.DELTA_SE);
var Right = (Us == Color.WHITE ? Square.DELTA_NE : Square.DELTA_SW);
var TRank2BB = (Us == Color.WHITE ? Bitboard.Rank2BB : Bitboard.Rank7BB);
var TRank7BB = (Us == Color.WHITE ? Bitboard.Rank7BB : Bitboard.Rank2BB);
const int Defended = 0;
const int Weak = 1;
const int Minor = 0;
const int Rook = 1;
BitboardT b;
var score = Score.SCORE_ZERO;
// Non-pawn enemies attacked by a pawn
var weak = (pos.pieces_Ct(Them) ^ pos.pieces_CtPt(Them, PieceType.PAWN)) & ei.attackedBy[Us, PieceType.PAWN];
if (weak!=0)
{
b = pos.pieces_CtPt(Us, PieceType.PAWN)
& (~ei.attackedBy[Them, PieceType.ALL_PIECES] | ei.attackedBy[Us, PieceType.ALL_PIECES]);
var safeThreats = (Bitboard.shift_bb(Right, b) | Bitboard.shift_bb(Left, b)) & weak;
if ((weak ^ safeThreats)!=0)
{
score += ThreatenedByHangingPawn;
}
while (safeThreats!=0)
{
score += ThreatenedByPawn[Piece.type_of(pos.piece_on(Utils.pop_lsb(ref safeThreats)))];
}
}
// Non-pawn enemies defended by a pawn
var defended = (pos.pieces_Ct(Them) ^ pos.pieces_CtPt(Them, PieceType.PAWN)) & ei.attackedBy[Them, PieceType.PAWN];
// Add a bonus according to the kind of attacking pieces
if (defended!=0)
{
b = defended & (ei.attackedBy[Us, PieceType.KNIGHT] | ei.attackedBy[Us, PieceType.BISHOP]);
while (b!=0)
{
score += Threat[Defended][Minor][Piece.type_of(pos.piece_on(Utils.pop_lsb(ref b)))];
}
b = defended & ei.attackedBy[Us, PieceType.ROOK];
while (b!=0)
{
score += Threat[Defended][Rook][Piece.type_of(pos.piece_on(Utils.pop_lsb(ref b)))];
}
}
// Enemies not defended by a pawn and under our attack
weak = pos.pieces_Ct(Them) & ~ei.attackedBy[Them, PieceType.PAWN] & ei.attackedBy[Us, PieceType.ALL_PIECES];
// Add a bonus according to the kind of attacking pieces
if (weak!=0)
{
b = weak & (ei.attackedBy[Us, PieceType.KNIGHT] | ei.attackedBy[Us, PieceType.BISHOP]);
while (b!=0)
{
score += Threat[Weak][Minor][Piece.type_of(pos.piece_on(Utils.pop_lsb(ref b)))];
}
b = weak & ei.attackedBy[Us, PieceType.ROOK];
while (b!=0)
{
score += Threat[Weak][Rook][Piece.type_of(pos.piece_on(Utils.pop_lsb(ref b)))];
}
b = weak & ~ei.attackedBy[Them, PieceType.ALL_PIECES];
if (b!=0)
{
score += Hanging*Bitcount.popcount_Max15(b);
}
b = weak & ei.attackedBy[Us, PieceType.KING];
if (b!=0)
{
score += Bitboard.more_than_one(b) ? KingOnMany : KingOnOne;
}
}
// Bonus if some pawns can safely push and attack an enemy piece
b = pos.pieces_CtPt(Us, PieceType.PAWN) & ~TRank7BB;
b = Bitboard.shift_bb(Up, b | (Bitboard.shift_bb(Up, b & TRank2BB) & ~pos.pieces()));
b &= ~pos.pieces() & ~ei.attackedBy[Them, PieceType.PAWN]
& (ei.attackedBy[Us, PieceType.ALL_PIECES] | ~ei.attackedBy[Them, PieceType.ALL_PIECES]);
b = (Bitboard.shift_bb(Left, b) | Bitboard.shift_bb(Right, b)) & pos.pieces_Ct(Them)
& ~ei.attackedBy[Us, PieceType.PAWN];
if (b!=0)
{
score += Bitcount.popcount_Max15(b)*PawnAttackThreat;
}
if (DoTrace)
{
add_IdxCtSt((int) Term.THREAT, Us, score);
}
return score;
}
// evaluate_king() assigns bonuses and penalties to a king of a given color
private static ScoreT evaluate_king(ColorT Us, bool DoTrace, Position pos, EvalInfo ei)
{
var Them = (Us == Color.WHITE ? Color.BLACK : Color.WHITE);
var ksq = pos.square(PieceType.KING, Us);
// King shelter and enemy pawns storm
var score = ei.pi.king_safety(Us, pos, ksq);
// 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
var undefended = ei.attackedBy[Them, PieceType.ALL_PIECES] & ei.attackedBy[Us, PieceType.KING]
& ~(ei.attackedBy[Us, PieceType.PAWN] | ei.attackedBy[Us, PieceType.KNIGHT]
| ei.attackedBy[Us, PieceType.BISHOP] | ei.attackedBy[Us, PieceType.ROOK]
| ei.attackedBy[Us, PieceType.QUEEN]);
// Initialize the 'attackUnits' variable, which is used later on as an
// index into 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).
var attackUnits = Math.Min(72, ei.kingAttackersCount[Them] *ei.kingAttackersWeight[Them])
+ 9*ei.kingAdjacentZoneAttacksCount[Them] + 27*Bitcount.popcount_Max15(undefended)
+ 11*((ulong)ei.pinnedPieces[Us] != 0 ? 1 : 0)
- 64*(pos.count(PieceType.QUEEN, Them) == 0 ? 1 : 0) - Score.mg_value(score)/8;
// Analyse the enemy's safe queen contact checks. Firstly, find the
// undefended squares around the king reachable by the enemy queen...
var b = undefended & ei.attackedBy[Them, PieceType.QUEEN] & ~pos.pieces_Ct(Them);
if (b!=0)
{
// ...and then remove squares not supported by another enemy piece
b &= ei.attackedBy[Them, PieceType.PAWN] | ei.attackedBy[Them, PieceType.KNIGHT]
| ei.attackedBy[Them, PieceType.BISHOP] | ei.attackedBy[Them, PieceType.ROOK];
if (b!=0)
{
attackUnits += QueenContactCheck*Bitcount.popcount_Max15(b);
}
}
// Analyse the enemy's safe distance checks for sliders and knights
var safe = ~(ei.attackedBy[Us, PieceType.ALL_PIECES] | pos.pieces_Ct(Them));
var b1 = pos.attacks_from_PtS(PieceType.ROOK, ksq) & safe;
var b2 = pos.attacks_from_PtS(PieceType.BISHOP, ksq) & safe;
// Enemy queen safe checks
b = (b1 | b2) & ei.attackedBy[Them, PieceType.QUEEN];
if (b!=0)
{
attackUnits += QueenCheck*Bitcount.popcount_Max15(b);
score -= Checked;
}
// Enemy rooks safe checks
b = b1 & ei.attackedBy[Them, PieceType.ROOK];
if (b!=0)
{
attackUnits += RookCheck*Bitcount.popcount_Max15(b);
score -= Checked;
}
// Enemy bishops safe checks
b = b2 & ei.attackedBy[Them, PieceType.BISHOP];
if (b!=0)
{
attackUnits += BishopCheck*Bitcount.popcount_Max15(b);
score -= Checked;
}
// Enemy knights safe checks
b = pos.attacks_from_PtS(PieceType.KNIGHT, ksq) & ei.attackedBy[Them, PieceType.KNIGHT] & safe;
if (b!=0)
{
attackUnits += KnightCheck*Bitcount.popcount_Max15(b);
score -= Checked;
}
// Finally, extract the king danger score from the KingDanger[]
// array and subtract the score from evaluation.
score -= KingDanger[Math.Max(Math.Min(attackUnits, 399), 0)];
}
if (DoTrace)
{
add_IdxCtSt(PieceType.KING, Us, score);
}
return score;
}