/// 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);
}
/// Entry::do_king_safety() calculates a bonus for king safety. It is called only
/// when king square changes, which is about 20% of total king_safety() calls.
public Score do_king_safety(Position pos, Square ksq, Color Us)
{
kingSquares[Us] = ksq;
castlingRights[Us] = pos.can_castle_color(Us);
minKPdistance[Us] = 0;
Bitboard pawns = pos.pieces_color_piecetype(Us, PieceTypeS.PAWN);
if (pawns != 0)
{
while (0 == (BitBoard.DistanceRingsBB[ksq][minKPdistance[Us]++] & pawns))
{
}
}
if (Types.relative_rank_square(Us, ksq) > RankS.RANK_4)
{
return(Types.make_score(0, -16 * minKPdistance[Us]));
}
Value bonus = shelter_storm(pos, ksq, Us);
// If we can castle use the bonus after the castle if is bigger
if (pos.can_castle_castleright((new MakeCastlingS(Us, CastlingSideS.KING_SIDE)).right) != 0)
{
bonus = Math.Max(bonus, shelter_storm(pos, Types.relative_square(Us, SquareS.SQ_G1), Us));
}
if (pos.can_castle_castleright((new MakeCastlingS(Us, CastlingSideS.QUEEN_SIDE)).right) != 0)
{
bonus = Math.Max(bonus, shelter_storm(pos, Types.relative_square(Us, SquareS.SQ_C1), Us));
}
return(Types.make_score(bonus, -16 * minKPdistance[Us]));
}
/// 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);
}
// evaluate_unstoppable_pawns() scores the most advanced among the passed and
// candidate pawns. In case opponent has no pieces but pawns, this is somewhat
// related to the possibility that pawns are unstoppable.
public static Score evaluate_unstoppable_pawns(Position pos, Color us, EvalInfo ei)
{
Bitboard b = ei.pi.passed_pawns(us) | ei.pi.candidate_pawns(us);
if (0 == b || pos.non_pawn_material(Types.notColor(us)) != 0)
{
return(ScoreS.SCORE_ZERO);
}
return(Unstoppable * (Types.relative_rank_square(us, BitBoard.frontmost_sq(us, b))));
}
public ScaleFactor KRPKB(Position pos)
{
Debug.Assert(verify_material(pos, strongSide, ValueS.RookValueMg, 1));
Debug.Assert(verify_material(pos, weakSide, ValueS.BishopValueMg, 0));
// Test for a rook pawn
if ((pos.pieces_piecetype(PieceTypeS.PAWN) & (BitBoard.FileABB | BitBoard.FileHBB)) != 0)
{
Square ksq = pos.king_square(weakSide);
Square bsq = pos.list(weakSide, PieceTypeS.BISHOP)[0];
Square psq = pos.list(strongSide, PieceTypeS.PAWN)[0];
Rank rk = Types.relative_rank_square(strongSide, psq);
Square push = Types.pawn_push(strongSide);
// If the pawn is on the 5th rank and the pawn (currently) is on
// the same color square as the bishop then there is a chance of
// a fortress. Depending on the king position give a moderate
// reduction or a stronger one if the defending king is near the
// corner but not trapped there.
if (rk == RankS.RANK_5 && !Types.opposite_colors(bsq, psq))
{
int d = BitBoard.square_distance(psq + 3 * push, ksq);
if (d <= 2 && !(d == 0 && ksq == pos.king_square(strongSide) + 2 * push))
{
return(24);
}
else
{
return(48);
}
}
// When the pawn has moved to the 6th rank we can be fairly sure
// it's drawn if the bishop attacks the square in front of the
// pawn from a reasonable distance and the defending king is near
// the corner
if (rk == RankS.RANK_6 &&
BitBoard.square_distance(psq + 2 * push, ksq) <= 1 &&
(BitBoard.PseudoAttacks[PieceTypeS.BISHOP][bsq] & BitBoard.SquareBB[(psq + push)]) != 0 &&
BitBoard.file_distance(bsq, psq) >= 2)
{
return(8);
}
}
return(ScaleFactorS.SCALE_FACTOR_NONE);
}
/// 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);
}
/// KQ vs KP. In general, this is a win for the stronger side, but there are a
/// few important exceptions. A pawn on 7th rank and on the A,C,F or H files
/// with a king positioned next to it can be a draw, so in that case, we only
/// use the distance between the kings.
public Value KQKP(Position pos)
{
Debug.Assert(verify_material(pos, strongSide, ValueS.QueenValueMg, 0));
Debug.Assert(verify_material(pos, weakSide, ValueS.VALUE_ZERO, 1));
Square winnerKSq = pos.king_square(strongSide);
Square loserKSq = pos.king_square(weakSide);
Square pawnSq = pos.list(weakSide, PieceTypeS.PAWN)[0];
Value result = (PushClose[BitBoard.square_distance(winnerKSq, loserKSq)]);
if (Types.relative_rank_square(weakSide, pawnSq) != RankS.RANK_7 ||
BitBoard.square_distance(loserKSq, pawnSq) != 1 ||
0 == ((BitBoard.FileABB | BitBoard.FileCBB | BitBoard.FileFBB | BitBoard.FileHBB) & BitBoard.SquareBB[pawnSq]))
{
result += ValueS.QueenValueEg - ValueS.PawnValueEg;
}
return(strongSide == pos.side_to_move() ? result : -result);
}
/// KQ vs KR and one or more pawns. It tests for fortress draws with a rook on
/// the third rank defended by a pawn.
public ScaleFactor KQKRPs(Position pos)
{
Debug.Assert(verify_material(pos, strongSide, ValueS.QueenValueMg, 0));
Debug.Assert(pos.count(weakSide, PieceTypeS.ROOK) == 1);
Debug.Assert(pos.count(weakSide, PieceTypeS.PAWN) >= 1);
Square kingSq = pos.king_square(weakSide);
Square rsq = pos.list(weakSide, PieceTypeS.ROOK)[0];
if (Types.relative_rank_square(weakSide, kingSq) <= RankS.RANK_2 &&
Types.relative_rank_square(weakSide, pos.king_square(strongSide)) >= RankS.RANK_4 &&
Types.relative_rank_square(weakSide, rsq) == RankS.RANK_3 &&
(pos.pieces_color_piecetype(weakSide, PieceTypeS.PAWN)
& pos.attacks_from_square_piecetype(kingSq, PieceTypeS.KING)
& pos.attacks_from_pawn(rsq, strongSide)) != 0)
{
return(ScaleFactorS.SCALE_FACTOR_DRAW);
}
return(ScaleFactorS.SCALE_FACTOR_NONE);
}
/// KRPP vs KRP. There is just a single rule: if the stronger side has no passed
/// pawns and the defending king is actively placed, the position is drawish.
public ScaleFactor KRPPKRP(Position pos)
{
Debug.Assert(verify_material(pos, strongSide, ValueS.RookValueMg, 2));
Debug.Assert(verify_material(pos, weakSide, ValueS.RookValueMg, 1));
Square wpsq1 = pos.list(strongSide, PieceTypeS.PAWN)[0];
Square wpsq2 = pos.list(strongSide, PieceTypeS.PAWN)[1];
Square bksq = pos.king_square(weakSide);
// Does the stronger side have a passed pawn?
if (pos.pawn_passed(strongSide, wpsq1) || pos.pawn_passed(strongSide, wpsq2))
{
return(ScaleFactorS.SCALE_FACTOR_NONE);
}
Rank r = Math.Max(Types.relative_rank_square(strongSide, wpsq1), Types.relative_rank_square(strongSide, wpsq2));
if (BitBoard.file_distance(bksq, wpsq1) <= 1 &&
BitBoard.file_distance(bksq, wpsq2) <= 1 &&
Types.relative_rank_square(strongSide, bksq) > r)
{
switch (r)
{
case RankS.RANK_2: return(10);
case RankS.RANK_3: return(10);
case RankS.RANK_4: return(15);
case RankS.RANK_5: return(20);
case RankS.RANK_6: return(40);
default: Debug.Assert(false); break;
}
}
return(ScaleFactorS.SCALE_FACTOR_NONE);
}
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);
}
/// 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);
}
}
/// 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_passed_pawns() evaluates the passed pawns of the given color
public static Score evaluate_passed_pawns(Position pos, EvalInfo ei, Color Us, bool Trace)
{
Color Them = (Us == ColorS.WHITE ? ColorS.BLACK : ColorS.WHITE);
Bitboard b, squaresToQueen, defendedSquares, unsafeSquares;
Score score = ScoreS.SCORE_ZERO;
b = ei.pi.passed_pawns(Us);
while (b != 0)
{
Square s = BitBoard.pop_lsb(ref b);
Debug.Assert(pos.pawn_passed(Us, s));
int r = (int)(Types.relative_rank_square(Us, s) - RankS.RANK_2);
int rr = r * (r - 1);
// Base bonus based on rank
Value mbonus = (17 * rr), ebonus = (7 * (rr + r + 1));
if (rr != 0)
{
Square blockSq = s + Types.pawn_push(Us);
// Adjust bonus based on kings proximity
ebonus += (BitBoard.square_distance(pos.king_square(Them), blockSq) * 5 * rr)
- (BitBoard.square_distance(pos.king_square(Us), blockSq) * 2 * rr);
// If blockSq is not the queening square then consider also a second push
if (Types.relative_rank_square(Us, blockSq) != RankS.RANK_8)
{
ebonus -= (BitBoard.square_distance(pos.king_square(Us), blockSq + Types.pawn_push(Us)) * rr);
}
// If the pawn is free to advance, increase bonus
if (pos.empty(blockSq))
{
squaresToQueen = BitBoard.forward_bb(Us, s);
// If there is an enemy rook or queen attacking the pawn from behind,
// add all X-ray attacks by the rook or queen. Otherwise consider only
// the squares in the pawn's path attacked or occupied by the enemy.
if ((BitBoard.forward_bb(Them, s) & pos.pieces_color_piecetype(Them, PieceTypeS.ROOK, PieceTypeS.QUEEN)) != 0 &&
(BitBoard.forward_bb(Them, s) & pos.pieces_color_piecetype(Them, PieceTypeS.ROOK, PieceTypeS.QUEEN) & pos.attacks_from_square_piecetype(s, PieceTypeS.ROOK)) != 0)
{
unsafeSquares = squaresToQueen;
}
else
{
unsafeSquares = squaresToQueen & (ei.attackedBy[Them][PieceTypeS.ALL_PIECES] | pos.pieces_color(Them));
}
if ((BitBoard.forward_bb(Them, s) & pos.pieces_color_piecetype(Us, PieceTypeS.ROOK, PieceTypeS.QUEEN)) != 0 &&
(BitBoard.forward_bb(Them, s) & pos.pieces_color_piecetype(Us, PieceTypeS.ROOK, PieceTypeS.QUEEN) & pos.attacks_from_square_piecetype(s, PieceTypeS.ROOK)) != 0)
{
defendedSquares = squaresToQueen;
}
else
{
defendedSquares = squaresToQueen & ei.attackedBy[Us][PieceTypeS.ALL_PIECES];
}
// If there aren't any enemy attacks, assign a big bonus. Otherwise
// assign a smaller bonus if the block square isn't attacked.
int k = 0 == unsafeSquares? 15 : 0 == (unsafeSquares & BitBoard.SquareBB[blockSq]) ? 9 : 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 ((defendedSquares & BitBoard.SquareBB[blockSq]) != 0)
{
k += 4;
}
mbonus += (k * rr); ebonus += (k * rr);
}
} // rr != 0
if (pos.count(Us, PieceTypeS.PAWN) < pos.count(Them, PieceTypeS.PAWN))
{
ebonus += ebonus / 4;
}
score += Types.make_score(mbonus, ebonus);
}
if (Trace)
{
Tracing.terms[Us][TermsS.PASSED] = apply_weight(score, Weights[EvalWeightS.PassedPawns]);
}
// Add the scores to the middle game and endgame eval
return(Eval.apply_weight(score, Weights[EvalWeightS.PassedPawns]));
}
// 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));
}
