/// KQ vs KR. This is almost identical to KX vs K: We give the attacking
/// king a bonus for having the kings close together, and for forcing the
/// defending king towards the edge. If we also take care to avoid null move
/// for the defending side in the search, this is usually sufficient to be
/// able to win KQ vs KR.
internal static Value Endgame_KQKR(Color strongerSide, Position pos)
{
Color weakerSide = strongerSide ^ 1;
Debug.Assert(pos.non_pawn_material(strongerSide) == Constants.QueenValueMidgame);
Debug.Assert(pos.piece_count(strongerSide, PieceTypeC.PAWN) == 0);
Debug.Assert(pos.non_pawn_material(weakerSide) == Constants.RookValueMidgame);
Debug.Assert(pos.piece_count(weakerSide, PieceTypeC.PAWN) == 0);
Square winnerKSq = pos.king_square(strongerSide);
Square loserKSq = pos.king_square(weakerSide);
Value result = Constants.QueenValueEndgame
- Constants.RookValueEndgame
+ MateTable[loserKSq]
+ DistanceBonus[Utils.square_distance(winnerKSq, loserKSq)];
return strongerSide == pos.sideToMove ? result : -result;
}
/// K and queen vs K, rook and one or more pawns. It tests for fortress draws with
/// a rook on the third rank defended by a pawn.
internal static ScaleFactor Endgame_KQKRPs(Color strongerSide, Position pos)
{
Color weakerSide = strongerSide ^ 1;
Debug.Assert(pos.non_pawn_material(strongerSide) == Constants.QueenValueMidgame);
Debug.Assert(pos.piece_count(strongerSide, PieceTypeC.QUEEN) == 1);
Debug.Assert(pos.piece_count(strongerSide, PieceTypeC.PAWN) == 0);
Debug.Assert(pos.piece_count(weakerSide, PieceTypeC.ROOK) == 1);
Debug.Assert(pos.piece_count(weakerSide, PieceTypeC.PAWN) >= 1);
Square kingSq = pos.king_square(weakerSide);
if (Utils.relative_rank_CS(weakerSide, kingSq) <= RankC.RANK_2
&& Utils.relative_rank_CS(weakerSide, pos.king_square(strongerSide)) >= RankC.RANK_4
&& ((pos.pieces_PTC(PieceTypeC.ROOK, weakerSide) & Utils.rank_bb_R(Utils.relative_rank_CR(weakerSide, RankC.RANK_3))) != 0)
&& ((pos.pieces_PTC(PieceTypeC.PAWN, weakerSide) & Utils.rank_bb_R(Utils.relative_rank_CR(weakerSide, RankC.RANK_2))) != 0)
&& ((Position.attacks_from_KING(kingSq) & pos.pieces_PTC(PieceTypeC.PAWN, weakerSide)) != 0)
)
{
Square rsq = pos.pieceList[weakerSide][PieceTypeC.ROOK][0];
if ((Position.attacks_from_PAWN(rsq, strongerSide) & pos.pieces_PTC(PieceTypeC.PAWN, weakerSide)) != 0)
return ScaleFactorC.SCALE_FACTOR_DRAW;
}
return ScaleFactorC.SCALE_FACTOR_NONE;
}
internal static bool is_KQKRPs(int Us, Position pos)
{
var Them = (Us == ColorC.WHITE ? ColorC.BLACK : ColorC.WHITE);
return pos.piece_count(Us, PieceTypeC.PAWN) == 0 && pos.non_pawn_material(Us) == Constants.QueenValueMidgame
&& pos.piece_count(Us, PieceTypeC.QUEEN) == 1 && pos.piece_count(Them, PieceTypeC.ROOK) == 1
&& pos.piece_count(Them, PieceTypeC.PAWN) >= 1;
}
/// KQ vs KP. In general, a win for the stronger side, however, there are a few
/// important exceptions. Pawn on 7th rank, A,C,F or H file, with king next can
/// be a draw, so we scale down to distance between kings only.
internal static int Endgame_KQKP(int strongerSide, Position pos)
{
var weakerSide = strongerSide ^ 1;
Debug.Assert(pos.non_pawn_material(strongerSide) == Constants.QueenValueMidgame);
Debug.Assert(pos.piece_count(strongerSide, PieceTypeC.PAWN) == 0);
Debug.Assert(pos.non_pawn_material(weakerSide) == 0);
Debug.Assert(pos.piece_count(weakerSide, PieceTypeC.PAWN) == 1);
Square winnerKSq = pos.king_square(strongerSide);
Square loserKSq = pos.king_square(weakerSide);
Square pawnSq = pos.pieceList[weakerSide][PieceTypeC.PAWN][0];
var result = Constants.QueenValueEndgame - Constants.PawnValueEndgame + DistanceBonus[Utils.square_distance(winnerKSq, loserKSq)];
if ( Utils.square_distance(loserKSq, pawnSq) == 1
&& Utils.relative_rank_CS(weakerSide, pawnSq) == RankC.RANK_7)
{
File f = Utils.file_of(pawnSq);
if (f == FileC.FILE_A || f == FileC.FILE_C || f == FileC.FILE_F || f == FileC.FILE_H)
{
result = DistanceBonus[Utils.square_distance(winnerKSq, loserKSq)];
}
}
return strongerSide == pos.sideToMove ? result : -result;
}
/// K, rook and two pawns vs K, rook and one pawn. There is only a single
/// pattern: If the stronger side has no passed pawns and the defending king
/// is actively placed, the position is drawish.
internal static ScaleFactor Endgame_KRPPKRP(Color strongerSide, Position pos)
{
Color weakerSide = strongerSide ^ 1;
Debug.Assert(pos.non_pawn_material(strongerSide) == Constants.RookValueMidgame);
Debug.Assert(pos.piece_count(strongerSide, PieceTypeC.PAWN) == 2);
Debug.Assert(pos.non_pawn_material(weakerSide) == Constants.RookValueMidgame);
Debug.Assert(pos.piece_count(weakerSide, PieceTypeC.PAWN) == 1);
Square wpsq1 = pos.pieceList[strongerSide][PieceTypeC.PAWN][0];
Square wpsq2 = pos.pieceList[strongerSide][PieceTypeC.PAWN][1];
Square bksq = pos.king_square(weakerSide);
// Does the stronger side have a passed pawn?
if (pos.pawn_is_passed(strongerSide, wpsq1)
|| pos.pawn_is_passed(strongerSide, wpsq2))
return ScaleFactorC.SCALE_FACTOR_NONE;
Rank r = Math.Max(Utils.relative_rank_CS(strongerSide, wpsq1), Utils.relative_rank_CS(strongerSide, wpsq2));
if (Utils.file_distance(bksq, wpsq1) <= 1
&& Utils.file_distance(bksq, wpsq2) <= 1
&& Utils.relative_rank_CS(strongerSide, bksq) > r)
{
switch (r)
{
case RankC.RANK_2: return (10);
case RankC.RANK_3: return (10);
case RankC.RANK_4: return (15);
case RankC.RANK_5: return (20);
case RankC.RANK_6: return (40);
default: Debug.Assert(false); break;
}
}
return ScaleFactorC.SCALE_FACTOR_NONE;
}
internal static bool is_KXK(int Us, Position pos)
{
var Them = (Us == ColorC.WHITE ? ColorC.BLACK : ColorC.WHITE);
return pos.non_pawn_material(Them) == ValueC.VALUE_ZERO && pos.piece_count(Them, PieceTypeC.PAWN) == 0
&& pos.non_pawn_material(Us) >= Constants.RookValueMidgame;
}
/// K, bishop and two pawns vs K and bishop. It detects a few basic draws with
/// opposite-colored bishops.
internal static ScaleFactor Endgame_KBPPKB(Color strongerSide, Position pos)
{
Color weakerSide = strongerSide ^ 1;
Debug.Assert(pos.non_pawn_material(strongerSide) == Constants.BishopValueMidgame);
Debug.Assert(pos.piece_count(strongerSide, PieceTypeC.BISHOP) == 1);
Debug.Assert(pos.piece_count(strongerSide, PieceTypeC.PAWN) == 2);
Debug.Assert(pos.non_pawn_material(weakerSide) == Constants.BishopValueMidgame);
Debug.Assert(pos.piece_count(weakerSide, PieceTypeC.BISHOP) == 1);
Debug.Assert(pos.piece_count(weakerSide, PieceTypeC.PAWN) == 0);
Square wbsq = pos.pieceList[strongerSide][PieceTypeC.BISHOP][0];
Square bbsq = pos.pieceList[weakerSide][PieceTypeC.BISHOP][0];
if (!Utils.opposite_colors(wbsq, bbsq))
return ScaleFactorC.SCALE_FACTOR_NONE;
Square ksq = pos.king_square(weakerSide);
Square psq1 = pos.pieceList[strongerSide][PieceTypeC.PAWN][0];
Square psq2 = pos.pieceList[strongerSide][PieceTypeC.PAWN][1];
Rank r1 = Utils.rank_of(psq1);
Rank r2 = Utils.rank_of(psq2);
Square blockSq1, blockSq2;
if (Utils.relative_rank_CS(strongerSide, psq1) > Utils.relative_rank_CS(strongerSide, psq2))
{
blockSq1 = psq1 + Utils.pawn_push(strongerSide);
blockSq2 = Utils.make_square(Utils.file_of(psq2), Utils.rank_of(psq1));
}
else
{
blockSq1 = psq2 + Utils.pawn_push(strongerSide);
blockSq2 = Utils.make_square(Utils.file_of(psq1), Utils.rank_of(psq2));
}
switch (Utils.file_distance(psq1, psq2))
{
case 0:
// Both pawns are on the same file. Easy draw if defender firmly controls
// some square in the frontmost pawn's path.
if (Utils.file_of(ksq) == Utils.file_of(blockSq1)
&& Utils.relative_rank_CS(strongerSide, ksq) >= Utils.relative_rank_CS(strongerSide, blockSq1)
&& Utils.opposite_colors(ksq, wbsq))
return ScaleFactorC.SCALE_FACTOR_DRAW;
else
return ScaleFactorC.SCALE_FACTOR_NONE;
case 1:
// Pawns on adjacent files. Draw if 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
&& Utils.opposite_colors(ksq, wbsq)
&& (bbsq == blockSq2
|| (((pos.attacks_from_BISHOP(blockSq2) & pos.pieces_PTC(PieceTypeC.BISHOP, weakerSide))) != 0)
|| Math.Abs(r1 - r2) >= 2))
return ScaleFactorC.SCALE_FACTOR_DRAW;
else if (ksq == blockSq2
&& Utils.opposite_colors(ksq, wbsq)
&& (bbsq == blockSq1
|| (((pos.attacks_from_BISHOP(blockSq1) & pos.pieces_PTC(PieceTypeC.BISHOP, weakerSide)))) != 0))
return ScaleFactorC.SCALE_FACTOR_DRAW;
else
return ScaleFactorC.SCALE_FACTOR_NONE;
default:
// The pawns are not on the same file or adjacent files. No scaling.
return ScaleFactorC.SCALE_FACTOR_NONE;
}
}
/// 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.
internal static Value Endgame_KRKP(Color strongerSide, Position pos)
{
Color weakerSide = strongerSide ^ 1;
Debug.Assert(pos.non_pawn_material(strongerSide) == Constants.RookValueMidgame);
Debug.Assert(pos.piece_count(strongerSide, PieceTypeC.PAWN) == 0);
Debug.Assert(pos.non_pawn_material(weakerSide) == 0);
Debug.Assert(pos.piece_count(weakerSide, PieceTypeC.PAWN) == 1);
Square wksq, wrsq, bksq, bpsq;
int tempo = (pos.sideToMove == strongerSide ? 1 : 0);
wksq = pos.king_square(strongerSide);
wrsq = pos.pieceList[strongerSide][PieceTypeC.ROOK][0];
bksq = pos.king_square(weakerSide);
bpsq = pos.pieceList[weakerSide][PieceTypeC.PAWN][0];
if (strongerSide == ColorC.BLACK)
{
wksq = Utils.flip_S(wksq);
wrsq = Utils.flip_S(wrsq);
bksq = Utils.flip_S(bksq);
bpsq = Utils.flip_S(bpsq);
}
Square queeningSq = Utils.make_square(Utils.file_of(bpsq), RankC.RANK_1);
Value result;
// If the stronger side's king is in front of the pawn, it's a win
if (wksq < bpsq && Utils.file_of(wksq) == Utils.file_of(bpsq))
result = Constants.RookValueEndgame - (Utils.square_distance(wksq, bpsq));
// If the weaker side's king is too far from the pawn and the rook,
// it's a win
else if (Utils.square_distance(bksq, bpsq) - (tempo ^ 1) >= 3
&& Utils.square_distance(bksq, wrsq) >= 3)
result = Constants.RookValueEndgame - (Utils.square_distance(wksq, bpsq));
// If the pawn is far advanced and supported by the defending king,
// the position is drawish
else if (Utils.rank_of(bksq) <= RankC.RANK_3
&& Utils.square_distance(bksq, bpsq) == 1
&& Utils.rank_of(wksq) >= RankC.RANK_4
&& Utils.square_distance(wksq, bpsq) - tempo > 2)
result = (80 - Utils.square_distance(wksq, bpsq) * 8);
else
result = (200)
- (Utils.square_distance(wksq, bpsq + SquareC.DELTA_S) * 8)
+ (Utils.square_distance(bksq, bpsq + SquareC.DELTA_S) * 8)
+ (Utils.square_distance(bpsq, queeningSq) * 8);
return strongerSide == pos.sideToMove ? result : -result;
}
/// K, bishop and a pawn vs K and a bishop. 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.
internal static ScaleFactor Endgame_KBPKB(Color strongerSide, Position pos)
{
Color weakerSide = strongerSide ^ 1;
Debug.Assert(pos.non_pawn_material(strongerSide) == Constants.BishopValueMidgame);
Debug.Assert(pos.piece_count(strongerSide, PieceTypeC.BISHOP) == 1);
Debug.Assert(pos.piece_count(strongerSide, PieceTypeC.PAWN) == 1);
Debug.Assert(pos.non_pawn_material(weakerSide) == Constants.BishopValueMidgame);
Debug.Assert(pos.piece_count(weakerSide, PieceTypeC.BISHOP) == 1);
Debug.Assert(pos.piece_count(weakerSide, PieceTypeC.PAWN) == 0);
Square pawnSq = pos.pieceList[strongerSide][PieceTypeC.PAWN][0];
Square strongerBishopSq = pos.pieceList[strongerSide][PieceTypeC.BISHOP][0];
Square weakerBishopSq = pos.pieceList[weakerSide][PieceTypeC.BISHOP][0];
Square weakerKingSq = pos.king_square(weakerSide);
// Case 1: Defending king blocks the pawn, and cannot be driven away
if (Utils.file_of(weakerKingSq) == Utils.file_of(pawnSq)
&& Utils.relative_rank_CS(strongerSide, pawnSq) < Utils.relative_rank_CS(strongerSide, weakerKingSq)
&& (Utils.opposite_colors(weakerKingSq, strongerBishopSq)
|| Utils.relative_rank_CS(strongerSide, weakerKingSq) <= RankC.RANK_6))
return ScaleFactorC.SCALE_FACTOR_DRAW;
// Case 2: Opposite colored bishops
if (Utils.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 (Utils.relative_rank_CS(strongerSide, pawnSq) <= RankC.RANK_5)
return ScaleFactorC.SCALE_FACTOR_DRAW;
else
{
Bitboard path = Utils.forward_bb(strongerSide, pawnSq);
if ((path & pos.pieces_PTC(PieceTypeC.KING, weakerSide)) != 0)
return ScaleFactorC.SCALE_FACTOR_DRAW;
if (((pos.attacks_from_BISHOP(weakerBishopSq) & path) != 0)
&& Utils.square_distance(weakerBishopSq, pawnSq) >= 3)
return ScaleFactorC.SCALE_FACTOR_DRAW;
}
}
return ScaleFactorC.SCALE_FACTOR_NONE;
}
/// K, bishop and a pawn vs K and knight. 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.
internal static ScaleFactor Endgame_KBPKN(Color strongerSide, Position pos)
{
Color weakerSide = strongerSide ^ 1;
Debug.Assert(pos.non_pawn_material(strongerSide) == Constants.BishopValueMidgame);
Debug.Assert(pos.piece_count(strongerSide, PieceTypeC.BISHOP) == 1);
Debug.Assert(pos.piece_count(strongerSide, PieceTypeC.PAWN) == 1);
Debug.Assert(pos.non_pawn_material(weakerSide) == Constants.KnightValueMidgame);
Debug.Assert(pos.piece_count(weakerSide, PieceTypeC.KNIGHT) == 1);
Debug.Assert(pos.piece_count(weakerSide, PieceTypeC.PAWN) == 0);
Square pawnSq = pos.pieceList[strongerSide][PieceTypeC.PAWN][0];
Square strongerBishopSq = pos.pieceList[strongerSide][PieceTypeC.BISHOP][0];
Square weakerKingSq = pos.king_square(weakerSide);
if (Utils.file_of(weakerKingSq) == Utils.file_of(pawnSq)
&& Utils.relative_rank_CS(strongerSide, pawnSq) < Utils.relative_rank_CS(strongerSide, weakerKingSq)
&& (Utils.opposite_colors(weakerKingSq, strongerBishopSq)
|| Utils.relative_rank_CS(strongerSide, weakerKingSq) <= RankC.RANK_6))
return ScaleFactorC.SCALE_FACTOR_DRAW;
return ScaleFactorC.SCALE_FACTOR_NONE;
}
/// Mate with KBN vs K. This is similar to KX vs K, but we have to drive the
/// defending king towards a corner square of the right color.
internal static Value Endgame_KBNK(Color strongerSide, Position pos)
{
Color weakerSide = strongerSide ^ 1;
Debug.Assert(pos.non_pawn_material(weakerSide) == ValueC.VALUE_ZERO);
Debug.Assert(pos.piece_count(weakerSide, PieceTypeC.PAWN) == ValueC.VALUE_ZERO);
Debug.Assert(pos.non_pawn_material(strongerSide) == Constants.KnightValueMidgame + Constants.BishopValueMidgame);
Debug.Assert(pos.piece_count(strongerSide, PieceTypeC.BISHOP) == 1);
Debug.Assert(pos.piece_count(strongerSide, PieceTypeC.KNIGHT) == 1);
Debug.Assert(pos.piece_count(strongerSide, PieceTypeC.PAWN) == 0);
Square winnerKSq = pos.king_square(strongerSide);
Square loserKSq = pos.king_square(weakerSide);
Square bishopSquare = pos.pieceList[strongerSide][PieceTypeC.BISHOP][0];
// kbnk_mate_table() tries to drive toward corners A1 or H8,
// if we have a bishop that cannot reach the above squares we
// mirror the kings so to drive enemy toward corners A8 or H1.
if (Utils.opposite_colors(bishopSquare, SquareC.SQ_A1))
{
winnerKSq = Utils.mirror(winnerKSq);
loserKSq = Utils.mirror(loserKSq);
}
Value result = ValueC.VALUE_KNOWN_WIN
+ DistanceBonus[Utils.square_distance(winnerKSq, loserKSq)]
+ KBNKMateTable[loserKSq];
return strongerSide == pos.sideToMove ? result : -result;
}
internal static Value Endgame_KBBKN(Color strongerSide, Position pos)
{
Color weakerSide = strongerSide ^ 1;
Debug.Assert(pos.piece_count(strongerSide, PieceTypeC.BISHOP) == 2);
Debug.Assert(pos.non_pawn_material(strongerSide) == 2 * Constants.BishopValueMidgame);
Debug.Assert(pos.piece_count(weakerSide, PieceTypeC.KNIGHT) == 1);
Debug.Assert(pos.non_pawn_material(weakerSide) == Constants.KnightValueMidgame);
Debug.Assert(pos.pieces_PT(PieceTypeC.PAWN) == 0);
Value result = Constants.BishopValueEndgame;
Square wksq = pos.king_square(strongerSide);
Square bksq = pos.king_square(weakerSide);
Square nsq = pos.pieceList[weakerSide][PieceTypeC.KNIGHT][0];
// Bonus for attacking king close to defending king
result += (DistanceBonus[Utils.square_distance(wksq, bksq)]);
// Bonus for driving the defending king and knight apart
result += (Utils.square_distance(bksq, nsq) * 32);
// Bonus for restricting the knight's mobility
result += ((8 - Bitcount.popcount_1s_Max15(Position.attacks_from_KNIGHT(nsq))) * 8);
return strongerSide == pos.sideToMove ? result : -result;
}
internal int update_safety_BLACK(Position pos, int ksq)
{
this.kingSquaresBLACK = ksq;
this.castleRightsBLACK = pos.st.castleRights & CastleRightC.BLACK_ANY;
ulong pawns = (ulong)pos.piece_count(ColorC.BLACK, PieceTypeC.PAWN);
if (pawns > 0)
{
var minDist = this.minKPdistanceBLACK;
while ((Utils.DistanceRingsBB[ksq][minDist++] & pawns) != pawns)
{
}
}
if (((ksq >> 3) ^ (ColorC.BLACK * 7)) > RankC.RANK_4)
{
return this.kingSafetyBLACK = Utils.make_score(0, -16 * this.minKPdistanceBLACK);
}
var bonus = shelter_storm(ColorC.BLACK, pos, ksq);
// If we can castle use the bonus after the castle if is bigger
if ((pos.st.castleRights & CastleRightC.BLACK_OO) != 0)
{
bonus = Math.Max(bonus, shelter_storm(ColorC.BLACK, pos, (SquareC.SQ_G1 ^ (ColorC.BLACK * 56))));
}
if ((pos.st.castleRights & CastleRightC.BLACK_OOO) != 0)
{
bonus = Math.Max(bonus, shelter_storm(ColorC.BLACK, pos, (SquareC.SQ_C1 ^ (ColorC.BLACK * 56))));
}
return this.kingSafetyBLACK = Utils.make_score(bonus, -16 * this.minKPdistanceBLACK);
}
/// KR vs KB. This is very simple, and always returns drawish scores. The
/// score is slightly bigger when the defending king is close to the edge.
internal static Value Endgame_KRKB(Color strongerSide, Position pos)
{
Color weakerSide = strongerSide ^ 1;
Debug.Assert(pos.non_pawn_material(strongerSide) == Constants.RookValueMidgame);
Debug.Assert(pos.piece_count(strongerSide, PieceTypeC.PAWN) == 0);
Debug.Assert(pos.non_pawn_material(weakerSide) == Constants.BishopValueMidgame);
Debug.Assert(pos.piece_count(weakerSide, PieceTypeC.PAWN) == 0);
Debug.Assert(pos.piece_count(weakerSide, PieceTypeC.BISHOP) == 1);
Value result = (MateTable[pos.king_square(weakerSide)]);
return strongerSide == pos.sideToMove ? result : -result;
}
/// K, bishop 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.
internal static ScaleFactor Endgame_KBPsK(Color strongerSide, Position pos)
{
Color weakerSide = strongerSide ^ 1;
Debug.Assert(pos.non_pawn_material(strongerSide) == Constants.BishopValueMidgame);
Debug.Assert(pos.piece_count(strongerSide, PieceTypeC.BISHOP) == 1);
Debug.Assert(pos.piece_count(strongerSide, PieceTypeC.PAWN) >= 1);
// No Debug.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_PTC(PieceTypeC.PAWN, strongerSide);
File pawnFile = Utils.file_of(pos.pieceList[strongerSide][PieceTypeC.PAWN][0]);
// All pawns are on a single rook file ?
if ((pawnFile == FileC.FILE_A || pawnFile == FileC.FILE_H)
&& (((pawns & ~Utils.file_bb_F(pawnFile))) == 0))
{
Square bishopSq = pos.pieceList[strongerSide][PieceTypeC.BISHOP][0];
Square queeningSq = Utils.relative_square(strongerSide, Utils.make_square(pawnFile, RankC.RANK_8));
Square kingSq = pos.king_square(weakerSide);
if (Utils.opposite_colors(queeningSq, bishopSq)
&& Math.Abs(Utils.file_of(kingSq) - pawnFile) <= 1)
{
// The bishop has the wrong color, and the defending king is on the
// file of the pawn(s) or the adjacent file. Find the rank of the
// frontmost pawn.
Rank rank;
if (strongerSide == ColorC.WHITE)
{
for (rank = RankC.RANK_7; (((Utils.rank_bb_R(rank) & pawns)) == 0); rank--) { }
Debug.Assert(rank >= RankC.RANK_2 && rank <= RankC.RANK_7);
}
else
{
for (rank = RankC.RANK_2; (((Utils.rank_bb_R(rank) & pawns)) == 0); rank++) { }
rank = (rank ^ 7); // HACK to get the relative rank
Debug.Assert(rank >= RankC.RANK_2 && rank <= RankC.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 (Utils.square_distance(kingSq, queeningSq) <= 1
|| Utils.relative_rank_CS(strongerSide, kingSq) >= rank)
return ScaleFactorC.SCALE_FACTOR_DRAW;
}
}
return ScaleFactorC.SCALE_FACTOR_NONE;
}
/// KR vs KN. The attacking side has slightly better winning chances than
/// in KR vs KB, particularly if the king and the knight are far apart.
internal static Value Endgame_KRKN(Color strongerSide, Position pos)
{
Color weakerSide = strongerSide ^ 1;
Debug.Assert(pos.non_pawn_material(strongerSide) == Constants.RookValueMidgame);
Debug.Assert(pos.piece_count(strongerSide, PieceTypeC.PAWN) == 0);
Debug.Assert(pos.non_pawn_material(weakerSide) == Constants.KnightValueMidgame);
Debug.Assert(pos.piece_count(weakerSide, PieceTypeC.PAWN) == 0);
Debug.Assert(pos.piece_count(weakerSide, PieceTypeC.KNIGHT) == 1);
Square bksq = pos.king_square(weakerSide);
Square bnsq = pos.pieceList[weakerSide][PieceTypeC.KNIGHT][0];
Value result = (MateTable[bksq] + penalty[Utils.square_distance(bksq, bnsq)]);
return strongerSide == pos.sideToMove ? result : -result;
}
/// K, knight and a pawn vs K. There is a single rule: If the pawn is a rook pawn
/// on the 7th rank and the defending king prevents the pawn from advancing, the
/// position is drawn.
internal static ScaleFactor Endgame_KNPK(Color strongerSide, Position pos)
{
Color weakerSide = strongerSide ^ 1;
Debug.Assert(pos.non_pawn_material(strongerSide) == Constants.KnightValueMidgame);
Debug.Assert(pos.piece_count(strongerSide, PieceTypeC.KNIGHT) == 1);
Debug.Assert(pos.piece_count(strongerSide, PieceTypeC.PAWN) == 1);
Debug.Assert(pos.non_pawn_material(weakerSide) == ValueC.VALUE_ZERO);
Debug.Assert(pos.piece_count(weakerSide, PieceTypeC.PAWN) == 0);
Square pawnSq = pos.pieceList[strongerSide][PieceTypeC.PAWN][0];
Square weakerKingSq = pos.king_square(weakerSide);
if (pawnSq == Utils.relative_square(strongerSide, SquareC.SQ_A7)
&& Utils.square_distance(weakerKingSq, Utils.relative_square(strongerSide, SquareC.SQ_A8)) <= 1)
return ScaleFactorC.SCALE_FACTOR_DRAW;
if (pawnSq == Utils.relative_square(strongerSide, SquareC.SQ_H7)
&& Utils.square_distance(weakerKingSq, Utils.relative_square(strongerSide, SquareC.SQ_H8)) <= 1)
return ScaleFactorC.SCALE_FACTOR_DRAW;
return ScaleFactorC.SCALE_FACTOR_NONE;
}
/// K, rook and one pawn vs K and a rook. 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 not very pretty.
internal static ScaleFactor Endgame_KRPKR(Color strongerSide, Position pos)
{
Color weakerSide = strongerSide ^ 1;
Debug.Assert(pos.non_pawn_material(strongerSide) == Constants.RookValueMidgame);
Debug.Assert(pos.piece_count(strongerSide, PieceTypeC.PAWN) == 1);
Debug.Assert(pos.non_pawn_material(weakerSide) == Constants.RookValueMidgame);
Debug.Assert(pos.piece_count(weakerSide, PieceTypeC.PAWN) == 0);
Square wksq = pos.king_square(strongerSide);
Square wrsq = pos.pieceList[strongerSide][PieceTypeC.ROOK][0];
Square wpsq = pos.pieceList[strongerSide][PieceTypeC.PAWN][0];
Square bksq = pos.king_square(weakerSide);
Square brsq = pos.pieceList[weakerSide][PieceTypeC.ROOK][0];
// Orient the board in such a way that the stronger side is white, and the
// pawn is on the left half of the board.
if (strongerSide == ColorC.BLACK)
{
wksq = Utils.flip_S(wksq);
wrsq = Utils.flip_S(wrsq);
wpsq = Utils.flip_S(wpsq);
bksq = Utils.flip_S(bksq);
brsq = Utils.flip_S(brsq);
}
if (Utils.file_of(wpsq) > FileC.FILE_D)
{
wksq = Utils.mirror(wksq);
wrsq = Utils.mirror(wrsq);
wpsq = Utils.mirror(wpsq);
bksq = Utils.mirror(bksq);
brsq = Utils.mirror(brsq);
}
File f = Utils.file_of(wpsq);
Rank r = Utils.rank_of(wpsq);
Square queeningSq = Utils.make_square(f, RankC.RANK_8);
int tempo = (pos.sideToMove == strongerSide ? 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 <= RankC.RANK_5
&& Utils.square_distance(bksq, queeningSq) <= 1
&& wksq <= SquareC.SQ_H5
&& (Utils.rank_of(brsq) == RankC.RANK_6 || (r <= RankC.RANK_3 && Utils.rank_of(wrsq) != RankC.RANK_6)))
return ScaleFactorC.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 == RankC.RANK_6
&& Utils.square_distance(bksq, queeningSq) <= 1
&& Utils.rank_of(wksq) + tempo <= RankC.RANK_6
&& (Utils.rank_of(brsq) == RankC.RANK_1 || ((tempo == 0) && Math.Abs(Utils.file_of(brsq) - f) >= 3)))
return ScaleFactorC.SCALE_FACTOR_DRAW;
if (r >= RankC.RANK_6
&& bksq == queeningSq
&& Utils.rank_of(brsq) == RankC.RANK_1
&& ((tempo == 0) || Utils.square_distance(wksq, wpsq) >= 2))
return ScaleFactorC.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 == SquareC.SQ_A7
&& wrsq == SquareC.SQ_A8
&& (bksq == SquareC.SQ_H7 || bksq == SquareC.SQ_G7)
&& Utils.file_of(brsq) == FileC.FILE_A
&& (Utils.rank_of(brsq) <= RankC.RANK_3 || Utils.file_of(wksq) >= FileC.FILE_D || Utils.rank_of(wksq) <= RankC.RANK_5))
return ScaleFactorC.SCALE_FACTOR_DRAW;
// If the defending king blocks the pawn and the attacking king is too far
// away, it's a draw.
if (r <= RankC.RANK_5
&& bksq == wpsq + SquareC.DELTA_N
&& Utils.square_distance(wksq, wpsq) - tempo >= 2
&& Utils.square_distance(wksq, brsq) - tempo >= 2)
return ScaleFactorC.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 == RankC.RANK_7
&& f != FileC.FILE_A
&& Utils.file_of(wrsq) == f
&& wrsq != queeningSq
&& (Utils.square_distance(wksq, queeningSq) < Utils.square_distance(bksq, queeningSq) - 2 + tempo)
&& (Utils.square_distance(wksq, queeningSq) < Utils.square_distance(bksq, wrsq) + tempo))
return (ScaleFactorC.SCALE_FACTOR_MAX - 2 * Utils.square_distance(wksq, queeningSq));
// Similar to the above, but with the pawn further back
if (f != FileC.FILE_A
&& Utils.file_of(wrsq) == f
&& wrsq < wpsq
&& (Utils.square_distance(wksq, queeningSq) < Utils.square_distance(bksq, queeningSq) - 2 + tempo)
&& (Utils.square_distance(wksq, wpsq + SquareC.DELTA_N) < Utils.square_distance(bksq, wpsq + SquareC.DELTA_N) - 2 + tempo)
&& (Utils.square_distance(bksq, wrsq) + tempo >= 3
|| (Utils.square_distance(wksq, queeningSq) < Utils.square_distance(bksq, wrsq) + tempo
&& (Utils.square_distance(wksq, wpsq + SquareC.DELTA_N) < Utils.square_distance(bksq, wrsq) + tempo))))
return (ScaleFactorC.SCALE_FACTOR_MAX
- 8 * Utils.square_distance(wpsq, queeningSq)
- 2 * Utils.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 <= RankC.RANK_4 && bksq > wpsq)
{
if (Utils.file_of(bksq) == Utils.file_of(wpsq))
return (10);
if (Math.Abs(Utils.file_of(bksq) - Utils.file_of(wpsq)) == 1
&& Utils.square_distance(wksq, bksq) > 2)
return (24 - 2 * Utils.square_distance(wksq, bksq));
}
return ScaleFactorC.SCALE_FACTOR_NONE;
}
/// KP vs K. This endgame is evaluated with the help of a bitbase.
internal static Value Endgame_KPK(Color strongerSide, Position pos)
{
Color weakerSide = strongerSide ^ 1;
Debug.Assert(pos.non_pawn_material(strongerSide) == ValueC.VALUE_ZERO);
Debug.Assert(pos.non_pawn_material(weakerSide) == ValueC.VALUE_ZERO);
Debug.Assert(pos.piece_count(strongerSide, PieceTypeC.PAWN) == 1);
Debug.Assert(pos.piece_count(weakerSide, PieceTypeC.PAWN) == 0);
Square wksq, bksq, wpsq;
Color stm;
if (strongerSide == ColorC.WHITE)
{
wksq = pos.king_square(ColorC.WHITE);
bksq = pos.king_square(ColorC.BLACK);
wpsq = pos.pieceList[ColorC.WHITE][PieceTypeC.PAWN][0];
stm = pos.sideToMove;
}
else
{
wksq = Utils.flip_S(pos.king_square(ColorC.BLACK));
bksq = Utils.flip_S(pos.king_square(ColorC.WHITE));
wpsq = Utils.flip_S(pos.pieceList[ColorC.BLACK][PieceTypeC.PAWN][0]);
stm = Utils.flip_C(pos.sideToMove);
}
if (Utils.file_of(wpsq) >= FileC.FILE_E)
{
wksq = Utils.mirror(wksq);
bksq = Utils.mirror(bksq);
wpsq = Utils.mirror(wpsq);
}
if (KPKPosition.probe_kpk_bitbase(wksq, wpsq, bksq, stm) == 0)
return ValueC.VALUE_DRAW;
Value result = ValueC.VALUE_KNOWN_WIN
+ Constants.PawnValueEndgame
+ Utils.rank_of(wpsq);
return strongerSide == pos.sideToMove ? result : -result;
}
/// Mate with KX vs K. This function is used to evaluate positions with
/// King and plenty of material vs a lone king. It simply gives the
/// attacking side a bonus for driving the defending king towards the edge
/// of the board, and for keeping the distance between the two kings small.
/// KXK
internal static Value Endgame_KXK(Color strongerSide, Position pos)
{
Color weakerSide = strongerSide ^ 1;
Debug.Assert(pos.non_pawn_material(weakerSide) == ValueC.VALUE_ZERO);
Debug.Assert(pos.piece_count(weakerSide, PieceTypeC.PAWN) == ValueC.VALUE_ZERO);
// Stalemate detection with lone king
MList mlist = MListBroker.GetObject(); mlist.pos = 0;
Movegen.generate_legal(pos, mlist.moves, ref mlist.pos);
bool any = mlist.pos > 0;
MListBroker.Free();
if (pos.sideToMove == weakerSide
&& !pos.in_check()
&& !any)
{
return ValueC.VALUE_DRAW;
}
Square winnerKSq = pos.king_square(strongerSide);
Square loserKSq = pos.king_square(weakerSide);
Value result = pos.non_pawn_material(strongerSide)
+ pos.piece_count(strongerSide, PieceTypeC.PAWN) * Constants.PawnValueEndgame
+ MateTable[loserKSq]
+ DistanceBonus[Utils.square_distance(winnerKSq, loserKSq)];
if (pos.piece_count(strongerSide, PieceTypeC.QUEEN)!=0
|| pos.piece_count(strongerSide, PieceTypeC.ROOK)!=0
|| pos.bishop_pair(strongerSide))
{
result += ValueC.VALUE_KNOWN_WIN;
}
return strongerSide == pos.sideToMove ? result : -result;
}
/// K and a pawn vs K and a pawn. 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, she 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).
internal static ScaleFactor Endgame_KPKP(Color strongerSide, Position pos)
{
Color weakerSide = strongerSide ^ 1;
Debug.Assert(pos.non_pawn_material(strongerSide) == ValueC.VALUE_ZERO);
Debug.Assert(pos.non_pawn_material(weakerSide) == ValueC.VALUE_ZERO);
Debug.Assert(pos.piece_count(ColorC.WHITE, PieceTypeC.PAWN) == 1);
Debug.Assert(pos.piece_count(ColorC.BLACK, PieceTypeC.PAWN) == 1);
Square wksq = pos.king_square(strongerSide);
Square bksq = pos.king_square(weakerSide);
Square wpsq = pos.pieceList[strongerSide][PieceTypeC.PAWN][0];
Color stm = pos.sideToMove;
if (strongerSide == ColorC.BLACK)
{
wksq = Utils.flip_S(wksq);
bksq = Utils.flip_S(bksq);
wpsq = Utils.flip_S(wpsq);
stm = Utils.flip_C(stm);
}
if (Utils.file_of(wpsq) >= FileC.FILE_E)
{
wksq = Utils.mirror(wksq);
bksq = Utils.mirror(bksq);
wpsq = Utils.mirror(wpsq);
}
// 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 (Utils.rank_of(wpsq) >= RankC.RANK_5
&& Utils.file_of(wpsq) != FileC.FILE_A)
return ScaleFactorC.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 (KPKPosition.probe_kpk_bitbase(wksq, wpsq, bksq, stm) != 0) ? ScaleFactorC.SCALE_FACTOR_NONE : ScaleFactorC.SCALE_FACTOR_DRAW;
}
internal static bool is_KBPsKs(int Us, Position pos)
{
return pos.non_pawn_material(Us) == Constants.BishopValueMidgame
&& pos.piece_count(Us, PieceTypeC.BISHOP) == 1 && pos.piece_count(Us, PieceTypeC.PAWN) >= 1;
}
/// K and two or more pawns vs K. There is just a single rule here: If all pawns
/// are on the same rook file and are blocked by the defending king, it's a draw.
internal static ScaleFactor Endgame_KPsK(Color strongerSide, Position pos)
{
Color weakerSide = strongerSide ^ 1;
Debug.Assert(pos.non_pawn_material(strongerSide) == ValueC.VALUE_ZERO);
Debug.Assert(pos.piece_count(strongerSide, PieceTypeC.PAWN) >= 2);
Debug.Assert(pos.non_pawn_material(weakerSide) == ValueC.VALUE_ZERO);
Debug.Assert(pos.piece_count(weakerSide, PieceTypeC.PAWN) == 0);
Square ksq = pos.king_square(weakerSide);
Bitboard pawns = pos.pieces_PTC(PieceTypeC.PAWN, strongerSide);
// Are all pawns on the 'a' file?
if ((pawns & ~Constants.FileABB) == 0)
{
// Does the defending king block the pawns?
if (Utils.square_distance(ksq, Utils.relative_square(strongerSide, SquareC.SQ_A8)) <= 1
|| (Utils.file_of(ksq) == FileC.FILE_A
&& ((Utils.in_front_bb_CS(strongerSide, ksq)) & pawns) == 0))
return ScaleFactorC.SCALE_FACTOR_DRAW;
}
// Are all pawns on the 'h' file?
else if ((pawns & ~Constants.FileHBB) == 0)
{
// Does the defending king block the pawns?
if (Utils.square_distance(ksq, Utils.relative_square(strongerSide, SquareC.SQ_H8)) <= 1
|| (Utils.file_of(ksq) == FileC.FILE_H
&& ((Utils.in_front_bb_CS(strongerSide, ksq)) & pawns) == 0))
return ScaleFactorC.SCALE_FACTOR_DRAW;
}
return ScaleFactorC.SCALE_FACTOR_NONE;
}
/// MaterialTable::material_info() takes a position object as input,
/// computes or looks up a MaterialInfo object, and returns a pointer to it.
/// If the material configuration is not already present in the table, it
/// is stored there, so we don't have to recompute everything when the
/// same material configuration occurs again.
internal void probe(Position pos, out MaterialEntry e)
{
var key = pos.material_key();
e = this.entries[((uint)key) & Constants.MaterialTableMask];
// If mi->key matches the position's material hash key, it means that we
// have analysed this material configuration before, and we can simply
// return the information we found the last time instead of recomputing it.
if (e.key == key)
{
return;
}
// Initialize MaterialInfo entry
var npm = pos.non_pawn_material(ColorC.WHITE) + pos.non_pawn_material(ColorC.BLACK);
e.value = 0;
e.scalingFunctionWHITE = null;
e.scalingFunctionBLACK = null;
e.spaceWeight = 0;
e.key = key;
e.factorWHITE = e.factorBLACK = ScaleFactorC.SCALE_FACTOR_NORMAL;
e.gamePhase = npm >= MidgameLimit
? PhaseC.PHASE_MIDGAME
: npm <= EndgameLimit
? PhaseC.PHASE_ENDGAME
: (((npm - EndgameLimit) * 128) / (MidgameLimit - EndgameLimit));
// Let's look if we have a specialized evaluation function for this
// particular material configuration. First we look for a fixed
// configuration one, then a generic one if previous search failed.
if ((e.evaluationFunction = Endgame.probeValue(key, out e.evaluationFunctionColor)) != null)
{
return;
}
if (is_KXK(ColorC.WHITE, pos))
{
e.evaluationFunction = Endgame.Endgame_KXK;
e.evaluationFunctionColor = ColorC.WHITE;
return;
}
if (is_KXK(ColorC.BLACK, pos))
{
e.evaluationFunction = Endgame.Endgame_KXK;
e.evaluationFunctionColor = ColorC.BLACK;
return;
}
if ((pos.pieces_PT(PieceTypeC.PAWN) == 0) && (pos.pieces_PT(PieceTypeC.ROOK) == 0)
&& (pos.pieces_PT(PieceTypeC.QUEEN) == 0))
{
// Minor piece endgame with at least one minor piece per side and
// no pawns. Note that the case KmmK is already handled by KXK.
Debug.Assert(
(pos.pieces_PTC(PieceTypeC.KNIGHT, ColorC.WHITE) | pos.pieces_PTC(PieceTypeC.BISHOP, ColorC.WHITE))
!= 0);
Debug.Assert(
(pos.pieces_PTC(PieceTypeC.KNIGHT, ColorC.BLACK) | pos.pieces_PTC(PieceTypeC.BISHOP, ColorC.BLACK))
!= 0);
if (pos.piece_count(ColorC.WHITE, PieceTypeC.BISHOP) + pos.piece_count(ColorC.WHITE, PieceTypeC.KNIGHT)
<= 2
&& pos.piece_count(ColorC.BLACK, PieceTypeC.BISHOP)
+ pos.piece_count(ColorC.BLACK, PieceTypeC.KNIGHT) <= 2)
{
e.evaluationFunction = Endgame.Endgame_KmmKm;
e.evaluationFunctionColor = pos.sideToMove;
return;
}
}
// OK, we didn't find any special evaluation function for the current
// material configuration. Is there a suitable scaling function?
//
// We face problems when there are several conflicting applicable
// scaling functions and we need to decide which one to use.
EndgameScaleFactor sf;
int c;
if ((sf = Endgame.probeScaleFactor(key, out c)) != null)
{
if (c == ColorC.WHITE)
{
e.scalingFunctionWHITE = sf;
}
else
{
e.scalingFunctionBLACK = sf;
}
return;
}
// Generic scaling functions that refer to more then one material
// distribution. Should be probed after the specialized ones.
// Note that these ones don't return after setting the function.
if (is_KBPsKs(ColorC.WHITE, pos))
{
e.scalingFunctionWHITE = Endgame.Endgame_KBPsK;
}
if (is_KBPsKs(ColorC.BLACK, pos))
{
e.scalingFunctionBLACK = Endgame.Endgame_KBPsK;
}
if (is_KQKRPs(ColorC.WHITE, pos))
{
e.scalingFunctionWHITE = Endgame.Endgame_KQKRPs;
}
else if (is_KQKRPs(ColorC.BLACK, pos))
{
e.scalingFunctionBLACK = Endgame.Endgame_KQKRPs;
}
var npm_w = pos.non_pawn_material(ColorC.WHITE);
var npm_b = pos.non_pawn_material(ColorC.BLACK);
if (npm_w + npm_b == ValueC.VALUE_ZERO)
{
if (pos.piece_count(ColorC.BLACK, PieceTypeC.PAWN) == 0)
{
Debug.Assert(pos.piece_count(ColorC.WHITE, PieceTypeC.PAWN) >= 2);
e.scalingFunctionWHITE = Endgame.Endgame_KPsK;
}
else if (pos.piece_count(ColorC.WHITE, PieceTypeC.PAWN) == 0)
{
Debug.Assert(pos.piece_count(ColorC.BLACK, PieceTypeC.PAWN) >= 2);
e.scalingFunctionBLACK = Endgame.Endgame_KPsK;
}
else if (pos.piece_count(ColorC.WHITE, PieceTypeC.PAWN) == 1
&& pos.piece_count(ColorC.BLACK, PieceTypeC.PAWN) == 1)
{
// This is a special case because we set scaling functions
// for both colors instead of only one.
e.scalingFunctionWHITE = Endgame.Endgame_KPKP;
e.scalingFunctionBLACK = Endgame.Endgame_KPKP;
}
}
// No pawns makes it difficult to win, even with a material advantage
if (pos.piece_count(ColorC.WHITE, PieceTypeC.PAWN) == 0 && npm_w - npm_b <= Constants.BishopValueMidgame)
{
e.factorWHITE =
(byte)
(npm_w == npm_b || npm_w < Constants.RookValueMidgame
? 0
: NoPawnsSF[Math.Min(pos.piece_count(ColorC.WHITE, PieceTypeC.BISHOP), 2)]);
}
if (pos.piece_count(ColorC.BLACK, PieceTypeC.PAWN) == 0 && npm_b - npm_w <= Constants.BishopValueMidgame)
{
e.factorBLACK =
(byte)
(npm_w == npm_b || npm_b < Constants.RookValueMidgame
? 0
: NoPawnsSF[Math.Min(pos.piece_count(ColorC.BLACK, PieceTypeC.BISHOP), 2)]);
}
// Compute the space weight
if (npm_w + npm_b
>= 2 * Constants.QueenValueMidgame + 4 * Constants.RookValueMidgame + 2 * Constants.KnightValueMidgame)
{
var minorPieceCount = pos.piece_count(ColorC.WHITE, PieceTypeC.KNIGHT)
+ pos.piece_count(ColorC.WHITE, PieceTypeC.BISHOP)
+ pos.piece_count(ColorC.BLACK, PieceTypeC.KNIGHT)
+ pos.piece_count(ColorC.BLACK, PieceTypeC.BISHOP);
e.spaceWeight = minorPieceCount * minorPieceCount;
}
// Evaluate the material imbalance. We use PIECE_TYPE_NONE as a place holder
// for the bishop pair "extended piece", this allow us to be more flexible
// in defining bishop pair bonuses.
this.pieceCount[0][0] = pos.piece_count(ColorC.WHITE, PieceTypeC.BISHOP) > 1 ? 1 : 0;
this.pieceCount[0][1] = pos.piece_count(ColorC.WHITE, PieceTypeC.PAWN);
this.pieceCount[0][2] = pos.piece_count(ColorC.WHITE, PieceTypeC.KNIGHT);
this.pieceCount[0][3] = pos.piece_count(ColorC.WHITE, PieceTypeC.BISHOP);
this.pieceCount[0][4] = pos.piece_count(ColorC.WHITE, PieceTypeC.ROOK);
this.pieceCount[0][5] = pos.piece_count(ColorC.WHITE, PieceTypeC.QUEEN);
this.pieceCount[1][0] = pos.piece_count(ColorC.BLACK, PieceTypeC.BISHOP) > 1 ? 1 : 0;
this.pieceCount[1][1] = pos.piece_count(ColorC.BLACK, PieceTypeC.PAWN);
this.pieceCount[1][2] = pos.piece_count(ColorC.BLACK, PieceTypeC.KNIGHT);
this.pieceCount[1][3] = pos.piece_count(ColorC.BLACK, PieceTypeC.BISHOP);
this.pieceCount[1][4] = pos.piece_count(ColorC.BLACK, PieceTypeC.ROOK);
this.pieceCount[1][5] = pos.piece_count(ColorC.BLACK, PieceTypeC.QUEEN);
e.value = (short)((this.imbalance(ColorC.WHITE) - this.imbalance(ColorC.BLACK)) / 16);
}
/// K, bishop 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.
internal static int Endgame_KBPsK(int strongerSide, Position pos)
{
var weakerSide = strongerSide ^ 1;
Debug.Assert(pos.non_pawn_material(strongerSide) == Constants.BishopValueMidgame);
Debug.Assert(pos.piece_count(strongerSide, PieceTypeC.BISHOP) == 1);
Debug.Assert(pos.piece_count(strongerSide, PieceTypeC.PAWN) >= 1);
// No Debug.Assertions about the material of weakerSide, because we want draws to
// be detected even when the weaker side has some pawns.
var pawns = pos.pieces_PTC(PieceTypeC.PAWN, strongerSide);
var pawnFile = Utils.file_of(pos.pieceList[strongerSide][PieceTypeC.PAWN][0]);
// All pawns are on a single rook file ?
if ((pawnFile == FileC.FILE_A || pawnFile == FileC.FILE_H) && (((pawns & ~Utils.file_bb_F(pawnFile))) == 0))
{
var bishopSq = pos.pieceList[strongerSide][PieceTypeC.BISHOP][0];
var queeningSq = Utils.relative_square(strongerSide, Utils.make_square(pawnFile, RankC.RANK_8));
var kingSq = pos.king_square(weakerSide);
if (Utils.opposite_colors(queeningSq, bishopSq) && Math.Abs(Utils.file_of(kingSq) - pawnFile) <= 1)
{
// The bishop has the wrong color, and the defending king is on the
// file of the pawn(s) or the adjacent file. Find the rank of the
// frontmost pawn.
int rank;
if (strongerSide == ColorC.WHITE)
{
for (rank = RankC.RANK_7; (((Utils.rank_bb_R(rank) & pawns)) == 0); rank--)
{
}
Debug.Assert(rank >= RankC.RANK_2 && rank <= RankC.RANK_7);
}
else
{
for (rank = RankC.RANK_2; (((Utils.rank_bb_R(rank) & pawns)) == 0); rank++)
{
}
rank = (rank ^ 7); // HACK to get the relative rank
Debug.Assert(rank >= RankC.RANK_2 && rank <= RankC.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 (Utils.square_distance(kingSq, queeningSq) <= 1
|| Utils.relative_rank_CS(strongerSide, kingSq) >= rank)
{
return ScaleFactorC.SCALE_FACTOR_DRAW;
}
}
}
// All pawns on same B or G file? Then potential draw
if ((pawnFile == FileC.FILE_B || pawnFile == FileC.FILE_G)
&& (pos.pieces_PT(PieceTypeC.PAWN) & ~Utils.file_bb_F(pawnFile)) == 0
&& pos.non_pawn_material(weakerSide) == 0
&& pos.piece_count(weakerSide, PieceTypeC.PAWN) >= 1)
{
// Get weaker pawn closest to opponent's queening square
Bitboard wkPawns = pos.pieces_PTC(PieceTypeC.PAWN, weakerSide);
Square weakerPawnSq = strongerSide == ColorC.WHITE ? Utils.msb(wkPawns) : Utils.lsb(wkPawns);
Square strongerKingSq = pos.king_square(strongerSide);
Square weakerKingSq = pos.king_square(weakerSide);
Square bishopSq = pos.pieceList[strongerSide][PieceTypeC.BISHOP][0];
// Draw if weaker pawn is on rank 7, bishop can't attack the pawn, and
// weaker king can stop opposing opponent's king from penetrating.
if (Utils.relative_rank_CS(strongerSide, weakerPawnSq) == RankC.RANK_7
&& Utils.opposite_colors(bishopSq, weakerPawnSq)
&& Utils.square_distance(weakerPawnSq, weakerKingSq) <= Utils.square_distance(weakerPawnSq, strongerKingSq))
return ScaleFactorC.SCALE_FACTOR_DRAW;
}
return ScaleFactorC.SCALE_FACTOR_NONE;
}
