/// Entry::shelter_storm() calculates shelter and storm penalties for the file
/// the king is on, as well as the two adjacent files.
public Value shelter_storm(Position pos, Square ksq, Color Us)
{
Color Them = (Us == ColorS.WHITE ? ColorS.BLACK : ColorS.WHITE);
Value safety = Pawns.MaxSafetyBonus;
Bitboard b = pos.pieces_piecetype(PieceTypeS.PAWN) & (BitBoard.in_front_bb(Us, Types.rank_of(ksq)) | BitBoard.rank_bb_square(ksq));
Bitboard ourPawns = b & pos.pieces_color(Us);
Bitboard theirPawns = b & pos.pieces_color(Them);
Rank rkUs, rkThem;
File kf = Math.Max(FileS.FILE_B, Math.Min(FileS.FILE_G, Types.file_of(ksq)));
for (File f = kf - 1; f <= kf + 1; ++f)
{
b = ourPawns & BitBoard.file_bb_file(f);
rkUs = b != 0 ? Types.relative_rank_square(Us, BitBoard.backmost_sq(Us, b)) : RankS.RANK_1;
b = theirPawns & BitBoard.file_bb_file(f);
rkThem = b != 0 ? Types.relative_rank_square(Us, BitBoard.frontmost_sq(Them, b)) : RankS.RANK_1;
if ((MiddleEdges & BitBoard.SquareBB[Types.make_square(f, rkThem)]) != 0 &&
Types.file_of(ksq) == f &&
Types.relative_rank_square(Us, ksq) == rkThem - 1)
{
safety += 200;
}
else
{
safety -= ShelterWeakness[rkUs]
+ StormDanger[rkUs == RankS.RANK_1 ? 0 : rkThem == rkUs + 1 ? 2 : 1][rkThem];
}
}
return(safety);
}
// polyglot_key() returns the PolyGlot hash key of the given position
public static Key polyglot_key(Position pos)
{
Key key = 0;
Bitboard b = pos.pieces();
while (b != 0)
{
Square s = BitBoard.pop_lsb(ref b);
Piece pc = pos.piece_on(s);
// PolyGlot pieces are: BP = 0, WP = 1, BN = 2, ... BK = 10, WK = 11
int pieceOfs = 2 * (Types.type_of_piece(pc) - 1) + ((Types.color_of(pc) == ColorS.WHITE) ? 1 : 0);
key ^= PG[psq + (64 * pieceOfs + s)];
}
b = (ulong)pos.can_castle_castleright(CastlingRightS.ANY_CASTLING);
while (b != 0)
{
key ^= PG[castle + BitBoard.pop_lsb(ref b)];
}
if (pos.ep_square() != SquareS.SQ_NONE)
{
key ^= PG[enpassant + Types.file_of(pos.ep_square())];
}
if (pos.side_to_move() == ColorS.WHITE)
{
key ^= PG[turn + 0];
}
return(key);
}
public static bool probe_kpk(Square wksq, Square wpsq, Square bksq, Color us)
{
Debug.Assert(Types.file_of(wpsq) <= FileS.FILE_D);
uint idx = index(us, bksq, wksq, wpsq);
return((KPKBitbase[idx / 32] & (1U << (int)(idx & 0x1F))) != 0);
}
/// KBP vs KB. There are two rules: if the defending king is somewhere along the
/// path of the pawn, and the square of the king is not of the same color as the
/// stronger side's bishop, it's a draw. If the two bishops have opposite color,
/// it's almost always a draw.
public ScaleFactor KBPKB(Position pos)
{
Debug.Assert(verify_material(pos, strongSide, ValueS.BishopValueMg, 1));
Debug.Assert(verify_material(pos, weakSide, ValueS.BishopValueMg, 0));
Square pawnSq = pos.list(strongSide, PieceTypeS.PAWN)[0];
Square strongerBishopSq = pos.list(strongSide, PieceTypeS.BISHOP)[0];
Square weakerBishopSq = pos.list(weakSide, PieceTypeS.BISHOP)[0];
Square weakerKingSq = pos.king_square(weakSide);
// Case 1: Defending king blocks the pawn, and cannot be driven away
if (Types.file_of(weakerKingSq) == Types.file_of(pawnSq) &&
Types.relative_rank_square(strongSide, pawnSq) < Types.relative_rank_square(strongSide, weakerKingSq) &&
(Types.opposite_colors(weakerKingSq, strongerBishopSq) ||
Types.relative_rank_square(strongSide, weakerKingSq) <= RankS.RANK_6))
{
return(ScaleFactorS.SCALE_FACTOR_DRAW);
}
// Case 2: Opposite colored bishops
if (Types.opposite_colors(strongerBishopSq, weakerBishopSq))
{
// We assume that the position is drawn in the following three situations:
//
// a. The pawn is on rank 5 or further back.
// b. The defending king is somewhere in the pawn's path.
// c. The defending bishop attacks some square along the pawn's path,
// and is at least three squares away from the pawn.
//
// These rules are probably not perfect, but in practice they work
// reasonably well.
if (Types.relative_rank_square(strongSide, pawnSq) <= RankS.RANK_5)
{
return(ScaleFactorS.SCALE_FACTOR_DRAW);
}
else
{
Bitboard path = BitBoard.forward_bb(strongSide, pawnSq);
if ((path & pos.pieces_color_piecetype(weakSide, PieceTypeS.KING)) != 0)
{
return(ScaleFactorS.SCALE_FACTOR_DRAW);
}
if (((pos.attacks_from_square_piecetype(weakerBishopSq, PieceTypeS.BISHOP) & path) != 0) &&
BitBoard.square_distance(weakerBishopSq, pawnSq) >= 3)
{
return(ScaleFactorS.SCALE_FACTOR_DRAW);
}
}
}
return(ScaleFactorS.SCALE_FACTOR_NONE);
}
// Map the square as if strongSide is white and strongSide's only pawn
// is on the left half of the board.
public Square normalize(Position pos, Color strongSide, Square sq)
{
Debug.Assert(pos.count(strongSide, PieceTypeS.PAWN) == 1);
if (Types.file_of(pos.list(strongSide, PieceTypeS.PAWN)[0]) >= FileS.FILE_E)
{
sq = (Square)(sq ^ 7); // Mirror SQ_H1 -> SQ_A1
}
if (strongSide == ColorS.BLACK)
{
sq = Types.notSquare(sq);
}
return(sq);
}
/// KR vs KP. This is a somewhat tricky endgame to evaluate precisely without
/// a bitbase. The function below returns drawish scores when the pawn is
/// far advanced with support of the king, while the attacking king is far
/// away.
public Value KRKP(Position pos)
{
Debug.Assert(verify_material(pos, strongSide, ValueS.RookValueMg, 0));
Debug.Assert(verify_material(pos, weakSide, ValueS.VALUE_ZERO, 1));
Square wksq = Types.relative_square(strongSide, pos.king_square(strongSide));
Square bksq = Types.relative_square(strongSide, pos.king_square(weakSide));
Square rsq = Types.relative_square(strongSide, pos.list(strongSide, PieceTypeS.ROOK)[0]);
Square psq = Types.relative_square(strongSide, pos.list(weakSide, PieceTypeS.PAWN)[0]);
Square queeningSq = Types.make_square(Types.file_of(psq), RankS.RANK_1);
Value result;
// If the stronger side's king is in front of the pawn, it's a win
if (wksq < psq && Types.file_of(wksq) == Types.file_of(psq))
{
result = ValueS.RookValueEg - (BitBoard.square_distance(wksq, psq));
}
// If the weaker side's king is too far from the pawn and the rook,
// it's a win
else if (BitBoard.square_distance(bksq, psq) >= 3 + ((pos.side_to_move() == weakSide)?1:0) &&
BitBoard.square_distance(bksq, rsq) >= 3)
{
result = ValueS.RookValueEg - (BitBoard.square_distance(wksq, psq));
}
// If the pawn is far advanced and supported by the defending king,
// the position is drawish
else if (Types.rank_of(bksq) <= RankS.RANK_3 &&
BitBoard.square_distance(bksq, psq) == 1 &&
Types.rank_of(wksq) >= RankS.RANK_4 &&
BitBoard.square_distance(wksq, psq) > 2 + ((pos.side_to_move() == strongSide)?1:0))
{
result = 80 - 8 * BitBoard.square_distance(wksq, psq);
}
else
{
result = (Value)(200) - 8 * (BitBoard.square_distance(wksq, psq + SquareS.DELTA_S)
- BitBoard.square_distance(bksq, psq + SquareS.DELTA_S)
- BitBoard.square_distance(psq, queeningSq));
}
return(strongSide == pos.side_to_move() ? result : -result);
}
/// KBP vs KN. There is a single rule: If the defending king is somewhere along
/// the path of the pawn, and the square of the king is not of the same color as
/// the stronger side's bishop, it's a draw.
public ScaleFactor KBPKN(Position pos)
{
Debug.Assert(verify_material(pos, strongSide, ValueS.BishopValueMg, 1));
Debug.Assert(verify_material(pos, weakSide, ValueS.KnightValueMg, 0));
Square pawnSq = pos.list(strongSide, PieceTypeS.PAWN)[0];
Square strongerBishopSq = pos.list(strongSide, PieceTypeS.BISHOP)[0];
Square weakerKingSq = pos.king_square(weakSide);
if (Types.file_of(weakerKingSq) == Types.file_of(pawnSq) &&
Types.relative_rank_square(strongSide, pawnSq) < Types.relative_rank_square(strongSide, weakerKingSq) &&
(Types.opposite_colors(weakerKingSq, strongerBishopSq) ||
Types.relative_rank_square(strongSide, weakerKingSq) <= RankS.RANK_6))
{
return(ScaleFactorS.SCALE_FACTOR_DRAW);
}
return(ScaleFactorS.SCALE_FACTOR_NONE);
}
/// KP vs KP. This is done by removing the weakest side's pawn and probing the
/// KP vs K bitbase: If the weakest side has a draw without the pawn, it probably
/// has at least a draw with the pawn as well. The exception is when the stronger
/// side's pawn is far advanced and not on a rook file; in this case it is often
/// possible to win (e.g. 8/4k3/3p4/3P4/6K1/8/8/8 w - - 0 1).
public ScaleFactor KPKP(Position pos)
{
Debug.Assert(verify_material(pos, strongSide, ValueS.VALUE_ZERO, 1));
Debug.Assert(verify_material(pos, weakSide, ValueS.VALUE_ZERO, 1));
// Assume strongSide is white and the pawn is on files A-D
Square wksq = normalize(pos, strongSide, pos.king_square(strongSide));
Square bksq = normalize(pos, strongSide, pos.king_square(weakSide));
Square psq = normalize(pos, strongSide, pos.list(strongSide, PieceTypeS.PAWN)[0]);
Color us = strongSide == pos.side_to_move() ? ColorS.WHITE : ColorS.BLACK;
// If the pawn has advanced to the fifth rank or further, and is not a
// rook pawn, it's too dangerous to assume that it's at least a draw.
if (Types.rank_of(psq) >= RankS.RANK_5 && Types.file_of(psq) != FileS.FILE_A)
{
return(ScaleFactorS.SCALE_FACTOR_NONE);
}
// Probe the KPK bitbase with the weakest side's pawn removed. If it's a draw,
// it's probably at least a draw even with the pawn.
return(Bitbases.probe_kpk(wksq, psq, bksq, us) ? ScaleFactorS.SCALE_FACTOR_NONE : ScaleFactorS.SCALE_FACTOR_DRAW);
}
/// Bitboards::init() initializes various bitboard tables. It is called at
/// startup and relies on global objects to be already zero-initialized.
public static void init()
{
for (Square s = SquareS.SQ_A1; s <= SquareS.SQ_H8; ++s)
{
BSFTable[bsf_index(SquareBB[s] = 1UL << s)] = s;
}
for (Bitboard b = 1; b < 256; ++b)
{
MS1BTable[b] = more_than_one(b) ? MS1BTable[b - 1] : lsb(b);
}
for (File f = FileS.FILE_A; f <= FileS.FILE_H; ++f)
{
FileBB[f] = f > FileS.FILE_A ? FileBB[f - 1] << 1 : FileABB;
}
for (Rank r = RankS.RANK_1; r <= RankS.RANK_8; ++r)
{
RankBB[r] = r > RankS.RANK_1 ? RankBB[r - 1] << 8 : Rank1BB;
}
for (File f = FileS.FILE_A; f <= FileS.FILE_H; ++f)
{
AdjacentFilesBB[f] = (f > FileS.FILE_A ? FileBB[f - 1] : 0) | (f < FileS.FILE_H ? FileBB[f + 1] : 0);
}
for (int c = ColorS.WHITE; c <= ColorS.BLACK; c++)
{
InFrontBB[c] = new Bitboard[RankS.RANK_NB];
}
for (Rank r = RankS.RANK_1; r < RankS.RANK_8; ++r)
{
InFrontBB[ColorS.WHITE][r] = ~(InFrontBB[ColorS.BLACK][r + 1] = InFrontBB[ColorS.BLACK][r] | RankBB[r]);
}
for (int c = ColorS.WHITE; c <= ColorS.BLACK; c++)
{
ForwardBB[c] = new Bitboard[SquareS.SQUARE_NB];
PawnAttackSpan[c] = new Bitboard[SquareS.SQUARE_NB];
PassedPawnMask[c] = new Bitboard[SquareS.SQUARE_NB];
}
for (Color c = ColorS.WHITE; c <= ColorS.BLACK; ++c)
{
for (Square s = SquareS.SQ_A1; s <= SquareS.SQ_H8; ++s)
{
ForwardBB[c][s] = InFrontBB[c][Types.rank_of(s)] & FileBB[Types.file_of(s)];
PawnAttackSpan[c][s] = InFrontBB[c][Types.rank_of(s)] & AdjacentFilesBB[Types.file_of(s)];
PassedPawnMask[c][s] = ForwardBB[c][s] | PawnAttackSpan[c][s];
}
}
for (Square c = 0; c < SquareS.SQUARE_NB; c++)
{
SquareDistance[c] = new int[SquareS.SQUARE_NB];
DistanceRingsBB[c] = new Bitboard[8];
}
for (Square s1 = SquareS.SQ_A1; s1 <= SquareS.SQ_H8; ++s1)
{
for (Square s2 = SquareS.SQ_A1; s2 <= SquareS.SQ_H8; ++s2)
{
if (s1 != s2)
{
SquareDistance[s1][s2] = Math.Max(file_distance(s1, s2), rank_distance(s1, s2));
DistanceRingsBB[s1][SquareDistance[s1][s2] - 1] |= SquareBB[s2];
}
}
}
int[][] steps = new int[7][];
steps[0] = new int[] { 0, 0, 0, 0, 0, 0, 0, 0, 0 };
steps[1] = new int[] { 7, 9, 0, 0, 0, 0, 0, 0, 0 };
steps[2] = new int[] { 17, 15, 10, 6, -6, -10, -15, -17, 0 };
steps[3] = new int[] { 0, 0, 0, 0, 0, 0, 0, 0, 0 };
steps[4] = new int[] { 0, 0, 0, 0, 0, 0, 0, 0, 0 };
steps[5] = new int[] { 0, 0, 0, 0, 0, 0, 0, 0, 0 };
steps[6] = new int[] { 9, 7, -7, -9, 8, 1, -1, -8, 0 };
for (Piece p = PieceS.NO_PIECE; p < PieceS.PIECE_NB; p++)
{
StepAttacksBB[p] = new Bitboard[SquareS.SQUARE_NB];
}
for (Color c = ColorS.WHITE; c <= ColorS.BLACK; ++c)
{
for (PieceType pt = PieceTypeS.PAWN; pt <= PieceTypeS.KING; ++pt)
{
for (Square s = SquareS.SQ_A1; s <= SquareS.SQ_H8; ++s)
{
for (int i = 0; steps[pt][i] != 0; ++i)
{
Square to = s + (Square)(c == ColorS.WHITE ? steps[pt][i] : -steps[pt][i]);
if (Types.is_ok_square(to) && BitBoard.square_distance(s, to) < 3)
{
StepAttacksBB[Types.make_piece(c, pt)][s] |= SquareBB[to];
}
}
}
}
}
Square[] RDeltas = new Square[] { SquareS.DELTA_N, SquareS.DELTA_E, SquareS.DELTA_S, SquareS.DELTA_W };
Square[] BDeltas = new Square[] { SquareS.DELTA_NE, SquareS.DELTA_SE, SquareS.DELTA_SW, SquareS.DELTA_NW };
init_magics(PieceTypeS.ROOK, RAttacks, RMagics, RMasks, RShifts, RDeltas, magic_index);
init_magics(PieceTypeS.BISHOP, BAttacks, BMagics, BMasks, BShifts, BDeltas, magic_index);
for (PieceType pt = PieceTypeS.NO_PIECE_TYPE; pt < PieceTypeS.PIECE_TYPE_NB; pt++)
{
PseudoAttacks[pt] = new Bitboard[SquareS.SQUARE_NB];
}
for (Square s = SquareS.SQ_A1; s <= SquareS.SQ_H8; s++)
{
BetweenBB[s] = new Bitboard[SquareS.SQUARE_NB];
LineBB[s] = new Bitboard[SquareS.SQUARE_NB];
}
for (Square s1 = SquareS.SQ_A1; s1 <= SquareS.SQ_H8; ++s1)
{
PseudoAttacks[PieceTypeS.QUEEN][s1] = PseudoAttacks[PieceTypeS.BISHOP][s1] = attacks_bb_SBBPT(s1, 0, PieceTypeS.BISHOP);
PseudoAttacks[PieceTypeS.QUEEN][s1] |= PseudoAttacks[PieceTypeS.ROOK][s1] = attacks_bb_SBBPT(s1, 0, PieceTypeS.ROOK);
for (Square s2 = SquareS.SQ_A1; s2 <= SquareS.SQ_H8; ++s2)
{
Piece pc = (PseudoAttacks[PieceTypeS.BISHOP][s1] & SquareBB[s2]) != 0 ? PieceS.W_BISHOP :
(PseudoAttacks[PieceTypeS.ROOK][s1] & SquareBB[s2]) != 0 ? PieceS.W_ROOK : PieceS.NO_PIECE;
if (pc == PieceS.NO_PIECE)
{
continue;
}
LineBB[s1][s2] = (attacks_bb_PSBB(pc, s1, 0) & attacks_bb_PSBB(pc, s2, 0)) | SquareBB[s1] | SquareBB[s2];
BetweenBB[s1][s2] = attacks_bb_PSBB(pc, s1, SquareBB[s2]) & attacks_bb_PSBB(pc, s2, SquareBB[s1]);
}
}
}
public static Bitboard file_bb_square(Square s)
{
return(FileBB[Types.file_of(s)]);
}
public static int file_distance(Square s1, Square s2)
{
return(Math.Abs(Types.file_of(s1) - Types.file_of(s2)));
}
// A KPK bitbase index is an integer in [0, IndexMax] range
//
// Information is mapped in a way that minimizes the number of iterations:
//
// bit 0- 5: white king square (from SQ_A1 to SQ_H8)
// bit 6-11: black king square (from SQ_A1 to SQ_H8)
// bit 12: side to move (WHITE or BLACK)
// bit 13-14: white pawn file (from FILE_A to FILE_D)
// bit 15-17: white pawn RANK_7 - rank (from RANK_7 - RANK_7 to RANK_7 - RANK_2)
public static uint index(Color us, Square bksq, Square wksq, Square psq)
{
return((uint)(wksq + (bksq << 6) + (us << 12) + (Types.file_of(psq) << 13) + ((RankS.RANK_7 - Types.rank_of(psq)) << 15)));
}
/// KRP vs KR. This function knows a handful of the most important classes of
/// drawn positions, but is far from perfect. It would probably be a good idea
/// to add more knowledge in the future.
///
/// It would also be nice to rewrite the actual code for this function,
/// which is mostly copied from Glaurung 1.x, and isn't very pretty.
public ScaleFactor KRPKR(Position pos)
{
Debug.Assert(verify_material(pos, strongSide, ValueS.RookValueMg, 1));
Debug.Assert(verify_material(pos, weakSide, ValueS.RookValueMg, 0));
// Assume strongSide is white and the pawn is on files A-D
Square wksq = normalize(pos, strongSide, pos.king_square(strongSide));
Square bksq = normalize(pos, strongSide, pos.king_square(weakSide));
Square wrsq = normalize(pos, strongSide, pos.list(strongSide, PieceTypeS.ROOK)[0]);
Square wpsq = normalize(pos, strongSide, pos.list(strongSide, PieceTypeS.PAWN)[0]);
Square brsq = normalize(pos, strongSide, pos.list(weakSide, PieceTypeS.ROOK)[0]);
File f = Types.file_of(wpsq);
Rank r = Types.rank_of(wpsq);
Square queeningSq = Types.make_square(f, RankS.RANK_8);
int tempo = (pos.side_to_move() == strongSide ? 1 : 0);
// If the pawn is not too far advanced and the defending king defends the
// queening square, use the third-rank defence.
if (r <= RankS.RANK_5 &&
BitBoard.square_distance(bksq, queeningSq) <= 1 &&
wksq <= SquareS.SQ_H5 &&
(Types.rank_of(brsq) == RankS.RANK_6 || (r <= RankS.RANK_3 && Types.rank_of(wrsq) != RankS.RANK_6)))
{
return(ScaleFactorS.SCALE_FACTOR_DRAW);
}
// The defending side saves a draw by checking from behind in case the pawn
// has advanced to the 6th rank with the king behind.
if (r == RankS.RANK_6 &&
BitBoard.square_distance(bksq, queeningSq) <= 1 &&
Types.rank_of(wksq) + tempo <= RankS.RANK_6 &&
(Types.rank_of(brsq) == RankS.RANK_1 || (0 == tempo && Math.Abs(Types.file_of(brsq) - f) >= 3)))
{
return(ScaleFactorS.SCALE_FACTOR_DRAW);
}
if (r >= RankS.RANK_6 &&
bksq == queeningSq &&
Types.rank_of(brsq) == RankS.RANK_1 &&
(0 == tempo || BitBoard.square_distance(wksq, wpsq) >= 2))
{
return(ScaleFactorS.SCALE_FACTOR_DRAW);
}
// White pawn on a7 and rook on a8 is a draw if black's king is on g7 or h7
// and the black rook is behind the pawn.
if (wpsq == SquareS.SQ_A7 &&
wrsq == SquareS.SQ_A8 &&
(bksq == SquareS.SQ_H7 || bksq == SquareS.SQ_G7) &&
Types.file_of(brsq) == FileS.FILE_A &&
(Types.rank_of(brsq) <= RankS.RANK_3 || Types.file_of(wksq) >= FileS.FILE_D || Types.rank_of(wksq) <= RankS.RANK_5))
{
return(ScaleFactorS.SCALE_FACTOR_DRAW);
}
// If the defending king blocks the pawn and the attacking king is too far
// away, it's a draw.
if (r <= RankS.RANK_5 &&
bksq == wpsq + SquareS.DELTA_N &&
BitBoard.square_distance(wksq, wpsq) - tempo >= 2 &&
BitBoard.square_distance(wksq, brsq) - tempo >= 2)
{
return(ScaleFactorS.SCALE_FACTOR_DRAW);
}
// Pawn on the 7th rank supported by the rook from behind usually wins if the
// attacking king is closer to the queening square than the defending king,
// and the defending king cannot gain tempi by threatening the attacking rook.
if (r == RankS.RANK_7 &&
f != FileS.FILE_A &&
Types.file_of(wrsq) == f &&
wrsq != queeningSq &&
(BitBoard.square_distance(wksq, queeningSq) < BitBoard.square_distance(bksq, queeningSq) - 2 + tempo) &&
(BitBoard.square_distance(wksq, queeningSq) < BitBoard.square_distance(bksq, wrsq) + tempo))
{
return((ScaleFactor)(ScaleFactorS.SCALE_FACTOR_MAX - 2 * BitBoard.square_distance(wksq, queeningSq)));
}
// Similar to the above, but with the pawn further back
if (f != FileS.FILE_A &&
Types.file_of(wrsq) == f &&
wrsq < wpsq &&
(BitBoard.square_distance(wksq, queeningSq) < BitBoard.square_distance(bksq, queeningSq) - 2 + tempo) &&
(BitBoard.square_distance(wksq, wpsq + SquareS.DELTA_N) < BitBoard.square_distance(bksq, wpsq + SquareS.DELTA_N) - 2 + tempo) &&
(BitBoard.square_distance(bksq, wrsq) + tempo >= 3 ||
(BitBoard.square_distance(wksq, queeningSq) < BitBoard.square_distance(bksq, wrsq) + tempo &&
(BitBoard.square_distance(wksq, wpsq + SquareS.DELTA_N) < BitBoard.square_distance(bksq, wrsq) + tempo))))
{
return((ScaleFactor)(ScaleFactorS.SCALE_FACTOR_MAX
- 8 * BitBoard.square_distance(wpsq, queeningSq)
- 2 * BitBoard.square_distance(wksq, queeningSq)));
}
// If the pawn is not far advanced, and the defending king is somewhere in
// the pawn's path, it's probably a draw.
if (r <= RankS.RANK_4 && bksq > wpsq)
{
if (Types.file_of(bksq) == Types.file_of(wpsq))
{
return(10);
}
if (Math.Abs(Types.file_of(bksq) - Types.file_of(wpsq)) == 1 &&
BitBoard.square_distance(wksq, bksq) > 2)
{
return(24 - 2 * BitBoard.square_distance(wksq, bksq));
}
}
return(ScaleFactorS.SCALE_FACTOR_NONE);
}
/// KB and one or more pawns vs K. It checks for draws with rook pawns and
/// a bishop of the wrong color. If such a draw is detected, SCALE_FACTOR_DRAW
/// is returned. If not, the return value is SCALE_FACTOR_NONE, i.e. no scaling
/// will be used.
public ScaleFactor KBPsK(Position pos)
{
Debug.Assert(pos.non_pawn_material(strongSide) == ValueS.BishopValueMg);
Debug.Assert(pos.count(strongSide, PieceTypeS.PAWN) >= 1);
// No assertions about the material of weakSide, because we want draws to
// be detected even when the weaker side has some pawns.
Bitboard pawns = pos.pieces_color_piecetype(strongSide, PieceTypeS.PAWN);
File pawnFile = Types.file_of(pos.list(strongSide, PieceTypeS.PAWN)[0]);
// All pawns are on a single rook file ?
if ((pawnFile == FileS.FILE_A || pawnFile == FileS.FILE_H) &&
0 == (pawns & ~BitBoard.file_bb_file(pawnFile)))
{
Square bishopSq = pos.list(strongSide, PieceTypeS.BISHOP)[0];
Square queeningSq = Types.relative_square(strongSide, Types.make_square(pawnFile, RankS.RANK_8));
Square kingSq = pos.king_square(weakSide);
if (Types.opposite_colors(queeningSq, bishopSq) &&
BitBoard.square_distance(queeningSq, kingSq) <= 1)
{
return(ScaleFactorS.SCALE_FACTOR_DRAW);
}
}
// If all the pawns are on the same B or G file, then it's potentially a draw
if ((pawnFile == FileS.FILE_B || pawnFile == FileS.FILE_G) &&
0 == (pos.pieces_piecetype(PieceTypeS.PAWN) & ~BitBoard.file_bb_file(pawnFile)) &&
pos.non_pawn_material(weakSide) == 0 &&
pos.count(weakSide, PieceTypeS.PAWN) >= 1)
{
// Get weakSide pawn that is closest to the home rank
Square weakPawnSq = BitBoard.backmost_sq(weakSide, pos.pieces_color_piecetype(weakSide, PieceTypeS.PAWN));
Square strongKingSq = pos.king_square(strongSide);
Square weakKingSq = pos.king_square(weakSide);
Square bishopSq = pos.list(strongSide, PieceTypeS.BISHOP)[0];
// There's potential for a draw if our pawn is blocked on the 7th rank,
// the bishop cannot attack it or they only have one pawn left
if (Types.relative_rank_square(strongSide, weakPawnSq) == RankS.RANK_7 &&
(pos.pieces_color_piecetype(strongSide, PieceTypeS.PAWN) & BitBoard.SquareBB[(weakPawnSq + Types.pawn_push(weakSide))]) != 0 &&
(Types.opposite_colors(bishopSq, weakPawnSq) || pos.count(strongSide, PieceTypeS.PAWN) == 1))
{
int strongKingDist = BitBoard.square_distance(weakPawnSq, strongKingSq);
int weakKingDist = BitBoard.square_distance(weakPawnSq, weakKingSq);
// It's a draw if the weak king is on its back two ranks, within 2
// squares of the blocking pawn and the strong king is not
// closer. (I think this rule only fails in practically
// unreachable positions such as 5k1K/6p1/6P1/8/8/3B4/8/8 w
// and positions where qsearch will immediately correct the
// problem such as 8/4k1p1/6P1/1K6/3B4/8/8/8 w)
if (Types.relative_rank_square(strongSide, weakKingSq) >= RankS.RANK_7 &&
weakKingDist <= 2 &&
weakKingDist <= strongKingDist)
{
return(ScaleFactorS.SCALE_FACTOR_DRAW);
}
}
}
return(ScaleFactorS.SCALE_FACTOR_NONE);
}
// 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));
}
public static Score evaluate(Position pos, Pawns.Entry e, Color Us)
{
Color Them = (Us == ColorS.WHITE ? ColorS.BLACK : ColorS.WHITE);
Square Up = (Us == ColorS.WHITE ? SquareS.DELTA_N : SquareS.DELTA_S);
Square Right = (Us == ColorS.WHITE ? SquareS.DELTA_NE : SquareS.DELTA_SW);
Square Left = (Us == ColorS.WHITE ? SquareS.DELTA_NW : SquareS.DELTA_SE);
Bitboard b, p, doubled;
Square s;
File f;
Rank r;
bool passed, isolated, opposed, connected, backward, candidate, unsupported;
Score value = ScoreS.SCORE_ZERO;
Square[] pl = pos.list(Us, PieceTypeS.PAWN);
int plPos = 0;
Bitboard ourPawns = pos.pieces_color_piecetype(Us, PieceTypeS.PAWN);
Bitboard theirPawns = pos.pieces_color_piecetype(Them, PieceTypeS.PAWN);
e.passedPawns[Us] = e.candidatePawns[Us] = 0;
e.kingSquares[Us] = SquareS.SQ_NONE;
e.semiopenFiles[Us] = 0xFF;
e.pawnAttacks[Us] = BitBoard.shift_bb(ourPawns, Right) | BitBoard.shift_bb(ourPawns, Left);
e.pawnsOnSquares[Us][ColorS.BLACK] = Bitcount.popcount_Max15(ourPawns & BitBoard.DarkSquares);
e.pawnsOnSquares[Us][ColorS.WHITE] = pos.count(Us, PieceTypeS.PAWN) - e.pawnsOnSquares[Us][ColorS.BLACK];
// Loop through all pawns of the current color and score each pawn
while ((s = pl[plPos++]) != SquareS.SQ_NONE)
{
Debug.Assert(pos.piece_on(s) == Types.make_piece(Us, PieceTypeS.PAWN));
f = Types.file_of(s);
// This file cannot be semi-open
e.semiopenFiles[Us] &= ~(1 << f);
// Previous rank
p = BitBoard.rank_bb_square(s - Types.pawn_push(Us));
// Our rank plus previous one
b = BitBoard.rank_bb_square(s) | p;
// Flag the pawn as passed, isolated, doubled,
// unsupported or connected (but not the backward one).
connected = (ourPawns & BitBoard.adjacent_files_bb(f) & b) != 0;
unsupported = (0 == (ourPawns & BitBoard.adjacent_files_bb(f) & p));
isolated = (0 == (ourPawns & BitBoard.adjacent_files_bb(f)));
doubled = ourPawns & BitBoard.forward_bb(Us, s);
opposed = (theirPawns & BitBoard.forward_bb(Us, s)) != 0;
passed = (0 == (theirPawns & BitBoard.passed_pawn_mask(Us, s)));
// Test for backward pawn.
// If the pawn is passed, isolated, or connected it cannot be
// backward. If there are friendly pawns behind on adjacent files
// or if it can capture an enemy pawn it cannot be backward either.
if ((passed | isolated | connected) ||
(ourPawns & BitBoard.pawn_attack_span(Them, s)) != 0 ||
(pos.attacks_from_pawn(s, Us) & theirPawns) != 0)
{
backward = false;
}
else
{
// We now know that there are no friendly pawns beside or behind this
// pawn on adjacent files. We now check whether the pawn is
// backward by looking in the forward direction on the adjacent
// files, and picking the closest pawn there.
b = BitBoard.pawn_attack_span(Us, s) & (ourPawns | theirPawns);
b = BitBoard.pawn_attack_span(Us, s) & BitBoard.rank_bb_square(BitBoard.backmost_sq(Us, b));
// If we have an enemy pawn in the same or next rank, the pawn is
// backward because it cannot advance without being captured.
backward = ((b | BitBoard.shift_bb(b, Up)) & theirPawns) != 0;
}
Debug.Assert(opposed | passed | (BitBoard.pawn_attack_span(Us, s) & theirPawns) != 0);
// A not-passed pawn is a candidate to become passed, if it is free to
// advance and if the number of friendly pawns beside or behind this
// pawn on adjacent files is higher than or equal to the number of
// enemy pawns in the forward direction on the adjacent files.
candidate = !(opposed | passed | backward | isolated) &&
(b = BitBoard.pawn_attack_span(Them, s + Types.pawn_push(Us)) & ourPawns) != 0 &&
Bitcount.popcount_Max15(b) >= Bitcount.popcount_Max15(BitBoard.pawn_attack_span(Us, s) & theirPawns);
// Passed pawns will be properly scored in evaluation because we need
// full attack info to evaluate passed pawns. Only the frontmost passed
// pawn on each file is considered a true passed pawn.
if (passed && 0 == doubled)
{
e.passedPawns[Us] |= BitBoard.SquareBB[s];
}
// Score this pawn
if (isolated)
{
value -= Isolated[opposed ? 1 : 0][f];
}
if (unsupported && !isolated)
{
value -= UnsupportedPawnPenalty;
}
if (doubled != 0)
{
value -= Types.divScore(Doubled[f], BitBoard.rank_distance(s, BitBoard.lsb(doubled)));
}
if (backward)
{
value -= Backward[opposed ? 1 : 0][f];
}
if (connected)
{
value += Connected[f][Types.relative_rank_square(Us, s)];
}
if (candidate)
{
value += CandidatePassed[Types.relative_rank_square(Us, s)];
if (0 == doubled)
{
e.candidatePawns[Us] |= BitBoard.SquareBB[s];
}
}
}
// In endgame it's better to have pawns on both wings. So give a bonus according
// to file distance between left and right outermost pawns.
if (pos.count(Us, PieceTypeS.PAWN) > 1)
{
b = (Bitboard)(e.semiopenFiles[Us] ^ 0xFF);
value += PawnsFileSpan * (BitBoard.msb(b) - BitBoard.lsb(b));
}
return(value);
}
/// move_to_san() takes a position and a legal Move as input and returns its
/// short algebraic notation representation.
public static string move_to_san(Position pos, Move m)
{
if (m == MoveS.MOVE_NONE)
{
return("(none)");
}
if (m == MoveS.MOVE_NULL)
{
return("(null)");
}
Debug.Assert((new MoveList(pos, GenTypeS.LEGAL).contains(m)));
Bitboard others, b;
string san = "";
Color us = pos.side_to_move();
Square from = Types.from_sq(m);
Square to = Types.to_sq(m);
Piece pc = pos.piece_on(from);
PieceType pt = Types.type_of_piece(pc);
if (Types.type_of_move(m) == MoveTypeS.CASTLING)
{
san = to > from ? "O-O" : "O-O-O";
}
else
{
if (pt != PieceTypeS.PAWN)
{
san = "" + PieceToChar[ColorS.WHITE][pt]; // Upper case
// A disambiguation occurs if we have more then one piece of type 'pt'
// that can reach 'to' with a legal move.
others = b = (pos.attacks_from_piece_square(pc, to) & pos.pieces_color_piecetype(us, pt)) ^ BitBoard.SquareBB[from];
while (b != 0)
{
Square s = BitBoard.pop_lsb(ref b);
if (!pos.legal(Types.make_move(s, to), pos.pinned_pieces(us)))
{
others ^= BitBoard.SquareBB[s];
}
}
if (0 == others)
{ /* Disambiguation is not needed */
}
else if (0 == (others & BitBoard.file_bb_square(from)))
{
san += Types.file_to_char(Types.file_of(from));
}
else if (0 == (others & BitBoard.rank_bb_square(from)))
{
san += Types.rank_to_char(Types.rank_of(from));
}
else
{
san += Types.square_to_string(from);
}
}
else if (pos.capture(m))
{
san = "" + Types.file_to_char(Types.file_of(from));
}
if (pos.capture(m))
{
san += 'x';
}
san += Types.square_to_string(to);
if (Types.type_of_move(m) == MoveTypeS.PROMOTION)
{
san += "=" + PieceToChar[ColorS.WHITE][Types.promotion_type(m)];
}
}
if (pos.gives_check(m, new CheckInfo(pos)))
{
StateInfo st = new StateInfo();
pos.do_move(m, st);
san += (new MoveList(pos, GenTypeS.LEGAL)).size() > 0 ? "+" : "#";
pos.undo_move(m);
}
return(san);
}
/// KBPP vs KB. It detects a few basic draws with opposite-colored bishops
public ScaleFactor KBPPKB(Position pos)
{
Debug.Assert(verify_material(pos, strongSide, ValueS.BishopValueMg, 2));
Debug.Assert(verify_material(pos, weakSide, ValueS.BishopValueMg, 0));
Square wbsq = pos.list(strongSide, PieceTypeS.BISHOP)[0];
Square bbsq = pos.list(weakSide, PieceTypeS.BISHOP)[0];
if (!Types.opposite_colors(wbsq, bbsq))
{
return(ScaleFactorS.SCALE_FACTOR_NONE);
}
Square ksq = pos.king_square(weakSide);
Square psq1 = pos.list(strongSide, PieceTypeS.PAWN)[0];
Square psq2 = pos.list(strongSide, PieceTypeS.PAWN)[1];
Rank r1 = Types.rank_of(psq1);
Rank r2 = Types.rank_of(psq2);
Square blockSq1, blockSq2;
if (Types.relative_rank_square(strongSide, psq1) > Types.relative_rank_square(strongSide, psq2))
{
blockSq1 = psq1 + Types.pawn_push(strongSide);
blockSq2 = Types.make_square(Types.file_of(psq2), Types.rank_of(psq1));
}
else
{
blockSq1 = psq2 + Types.pawn_push(strongSide);
blockSq2 = Types.make_square(Types.file_of(psq1), Types.rank_of(psq2));
}
switch (BitBoard.file_distance(psq1, psq2))
{
case 0:
// Both pawns are on the same file. It's an easy draw if the defender firmly
// controls some square in the frontmost pawn's path.
if (Types.file_of(ksq) == Types.file_of(blockSq1) &&
Types.relative_rank_square(strongSide, ksq) >= Types.relative_rank_square(strongSide, blockSq1) &&
Types.opposite_colors(ksq, wbsq))
{
return(ScaleFactorS.SCALE_FACTOR_DRAW);
}
else
{
return(ScaleFactorS.SCALE_FACTOR_NONE);
}
case 1:
// Pawns on adjacent files. It's a draw if the defender firmly controls the
// square in front of the frontmost pawn's path, and the square diagonally
// behind this square on the file of the other pawn.
if (ksq == blockSq1 &&
Types.opposite_colors(ksq, wbsq) &&
(bbsq == blockSq2 ||
(pos.attacks_from_square_piecetype(blockSq2, PieceTypeS.BISHOP) & pos.pieces_color_piecetype(weakSide, PieceTypeS.BISHOP)) != 0 ||
Math.Abs(r1 - r2) >= 2))
{
return(ScaleFactorS.SCALE_FACTOR_DRAW);
}
else if (ksq == blockSq2 &&
Types.opposite_colors(ksq, wbsq) &&
(bbsq == blockSq1 ||
(pos.attacks_from_square_piecetype(blockSq1, PieceTypeS.BISHOP) & pos.pieces_color_piecetype(weakSide, PieceTypeS.BISHOP)) != 0))
{
return(ScaleFactorS.SCALE_FACTOR_DRAW);
}
else
{
return(ScaleFactorS.SCALE_FACTOR_NONE);
}
default:
// The pawns are not on the same file or adjacent files. No scaling.
return(ScaleFactorS.SCALE_FACTOR_NONE);
}
}
