internal override ScaleFactor GetScaleFactor(Position pos)
{
Debug.Assert(verify_material(pos, strongSide, Value.RookValueMg, 1));
Debug.Assert(verify_material(pos, weakSide, Value.BishopValueMg, 0));
// Test for a rook pawn
if ((pos.pieces_Pt(PieceType.PAWN) & (Bitboard.FileABB | Bitboard.FileHBB))!=0)
{
var ksq = pos.square(PieceType.KING, weakSide);
var bsq = pos.square(PieceType.BISHOP, weakSide);
var psq = pos.square(PieceType.PAWN, strongSide);
var rk = Rank.relative_rank_CtSt(strongSide, psq);
var push = Square.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 == Rank.RANK_5 && !Square.opposite_colors(bsq, psq))
{
var d = Utils.distance_Square(psq + 3*push, ksq);
if (d <= 2 && !(d == 0 && ksq == pos.square(PieceType.KING, strongSide) + 2*push))
{
return (ScaleFactor) (24);
}
return (ScaleFactor) (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 == Rank.RANK_6 && Utils.distance_Square(psq + 2*push, ksq) <= 1
&& Bitboard.AndWithSquare(Utils.PseudoAttacks[PieceType.BISHOP, bsq], (psq + push))!=0 && Utils.distance_File(bsq, psq) >= 2)
{
return (ScaleFactor) (8);
}
}
return ScaleFactor.SCALE_FACTOR_NONE;
}
internal override ScaleFactor GetScaleFactor(Position pos)
{
Debug.Assert(pos.non_pawn_material(strongSide) == Value.BishopValueMg);
Debug.Assert(pos.count(PieceType.PAWN, strongSide) >= 1);
// No assertions about the material of weakSide, because we want draws to
// be detected even when the weaker side has some pawns.
var pawns = pos.pieces_CtPt(strongSide, PieceType.PAWN);
var pawnsFile = Square.file_of(Utils.lsb(pawns));
// All pawns are on a single rook file?
if ((pawnsFile == File.FILE_A || pawnsFile == File.FILE_H) && (pawns & ~Utils.file_bb_Ft(pawnsFile))==0)
{
var bishopSq = pos.square(PieceType.BISHOP, strongSide);
var queeningSq = Square.relative_square(strongSide, Square.make_square(pawnsFile, Rank.RANK_8));
var kingSq = pos.square(PieceType.KING, weakSide);
if (Square.opposite_colors(queeningSq, bishopSq) && Utils.distance_Square(queeningSq, kingSq) <= 1)
{
return ScaleFactor.SCALE_FACTOR_DRAW;
}
}
// If all the pawns are on the same B or G file, then it's potentially a draw
if ((pawnsFile == File.FILE_B || pawnsFile == File.FILE_G)
&& (pos.pieces_Pt(PieceType.PAWN) & ~Utils.file_bb_Ft(pawnsFile))==0 && pos.non_pawn_material(weakSide) == 0
&& pos.count(PieceType.PAWN, weakSide) >= 1)
{
// Get weakSide pawn that is closest to the home rank
var weakPawnSq = Utils.backmost_sq(weakSide, pos.pieces_CtPt(weakSide, PieceType.PAWN));
var strongKingSq = pos.square(PieceType.KING, strongSide);
var weakKingSq = pos.square(PieceType.KING, weakSide);
var bishopSq = pos.square(PieceType.BISHOP, strongSide);
// 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 (Rank.relative_rank_CtSt(strongSide, weakPawnSq) == Rank.RANK_7
&& Bitboard.AndWithSquare(pos.pieces_CtPt(strongSide, PieceType.PAWN), (weakPawnSq + Square.pawn_push(weakSide)))!=0
&& (Square.opposite_colors(bishopSq, weakPawnSq) || pos.count(PieceType.PAWN, strongSide) == 1))
{
var strongKingDist = Utils.distance_Square(weakPawnSq, strongKingSq);
var weakKingDist = Utils.distance_Square(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 (Rank.relative_rank_CtSt(strongSide, weakKingSq) >= Rank.RANK_7 && weakKingDist <= 2
&& weakKingDist <= strongKingDist)
{
return ScaleFactor.SCALE_FACTOR_DRAW;
}
}
}
return ScaleFactor.SCALE_FACTOR_NONE;
}
/// Entry::shelter_storm() calculates shelter and storm penalties for the file
/// the king is on, as well as the two adjacent files.
private ValueT shelter_storm(ColorT Us, Position pos, SquareT ksq)
{
const int NoFriendlyPawn = 0;
const int Unblocked = 1;
const int BlockedByPawn = 2;
const int BlockedByKing = 3;
var Them = (Us == Color.WHITE ? Color.BLACK : Color.WHITE);
var b = pos.pieces_Pt(PieceType.PAWN) & (Utils.in_front_bb(Us, Square.rank_of(ksq)) | Utils.rank_bb_St(ksq));
var ourPawns = b & pos.pieces_Ct(Us);
var theirPawns = b & pos.pieces_Ct(Them);
var safety = MaxSafetyBonus;
var center = File.Create(Math.Max(File.FILE_B, Math.Min(File.FILE_G, Square.file_of(ksq))));
for (var f = center - 1; f <= (int)center + 1; ++f)
{
b = ourPawns & Utils.file_bb_Ft(File.Create(f));
var rkUs = b != 0 ? Rank.relative_rank_CtSt(Us, Utils.backmost_sq(Us, b)) : Rank.RANK_1;
b = theirPawns & Utils.file_bb_Ft(File.Create(f));
var rkThem = b != 0 ? Rank.relative_rank_CtSt(Us, Utils.frontmost_sq(Them, b)) : Rank.RANK_1;
safety -= ShelterWeakness[Math.Min(f, File.FILE_H - f)][rkUs]
+ StormDanger[
f == (int)Square.file_of(ksq) && rkThem == Rank.relative_rank_CtSt(Us, ksq) + 1
? BlockedByKing
: (int)rkUs == Rank.RANK_1
? NoFriendlyPawn
: rkThem == rkUs + 1 ? BlockedByPawn : Unblocked][Math.Min(f, File.FILE_H - f)][rkThem];
}
return safety;
}
/// Material::probe() looks up the current position's material configuration in
/// the material hash table. It returns a pointer to the Entry if the position
/// is found. Otherwise a new Entry is computed and stored there, so we don't
/// have to recompute all when the same material configuration occurs again.
internal static MaterialEntry probe(Position pos)
{
var key = pos.material_key();
MaterialEntry e;
if (!pos.this_thread().materialTable.TryGetValue(key, out e))
{
e = new MaterialEntry();
pos.this_thread().materialTable.Add(key, e);
}
else if (e.key == key)
{
return e;
}
e.reset();
e.key = key;
e.factor[Color.WHITE] = e.factor[Color.BLACK] = (ushort) ScaleFactor.SCALE_FACTOR_NORMAL;
e.gamePhase = pos.game_phase();
// Let's look if we have a specialized evaluation function for this particular
// material configuration. Firstly we look for a fixed configuration one, then
// for a generic one if the previous search failed.
if ((e.evaluationFunction = pos.this_thread().endgames.probeEndgameValue(key)) != null)
{
return e;
}
foreach (var c in Color.AllColors)
{
if (is_KXK(pos, c))
{
e.evaluationFunction = EvaluateKXK[c];
return e;
}
}
// OK, we didn't find any special evaluation function for the current material
// configuration. Is there a suitable specialized scaling function?
EndgameScaleFactor sf;
if ((sf = pos.this_thread().endgames.probeEndgameScaleFactor(key)) != null)
{
e.scalingFunction[sf.strong_side()] = sf; // Only strong color assigned
return e;
}
// We didn't find any specialized scaling function, so fall back on generic
// ones that refer to more than one material distribution. Note that in this
// case we don't return after setting the function.
foreach (var c in Color.AllColors)
{
if (is_KBPsKs(pos, c))
{
e.scalingFunction[c] = ScaleKBPsK[c];
}
else if (is_KQKRPs(pos, c))
{
e.scalingFunction[c] = ScaleKQKRPs[c];
}
}
var npm_w = pos.non_pawn_material(Color.WHITE);
var npm_b = pos.non_pawn_material(Color.BLACK);
if (npm_w + npm_b == Value.VALUE_ZERO && (pos.pieces_Pt(PieceType.PAWN) != 0)) // Only pawns on the board
{
if (pos.count(PieceType.PAWN, Color.BLACK) == 0)
{
Debug.Assert(pos.count(PieceType.PAWN, Color.WHITE) >= 2);
e.scalingFunction[Color.WHITE] = ScaleKPsK[Color.WHITE];
}
else if (pos.count(PieceType.PAWN, Color.WHITE) == 0)
{
Debug.Assert(pos.count(PieceType.PAWN, Color.BLACK) >= 2);
e.scalingFunction[Color.BLACK] = ScaleKPsK[Color.BLACK];
}
else if (pos.count(PieceType.PAWN, Color.WHITE) == 1 && pos.count(PieceType.PAWN, Color.BLACK) == 1)
{
// This is a special case because we set scaling functions
// for both colors instead of only one.
e.scalingFunction[Color.WHITE] = ScaleKPKP[Color.WHITE];
e.scalingFunction[Color.BLACK] = ScaleKPKP[Color.BLACK];
}
}
// Zero or just one pawn makes it difficult to win, even with a small material
// advantage. This catches some trivial draws like KK, KBK and KNK and gives a
// drawish scale factor for cases such as KRKBP and KmmKm (except for KBBKN).
if (pos.count(PieceType.PAWN, Color.WHITE) == 0 && npm_w - npm_b <= Value.BishopValueMg)
{
e.factor[Color.WHITE] =
(ushort)
(npm_w < Value.RookValueMg
? (ushort) ScaleFactor.SCALE_FACTOR_DRAW
: npm_b <= Value.BishopValueMg ? 4 : 14);
}
if (pos.count(PieceType.PAWN, Color.BLACK) == 0 && npm_b - npm_w <= Value.BishopValueMg)
{
e.factor[Color.BLACK] =
(ushort)
(npm_b < Value.RookValueMg
? (ushort) ScaleFactor.SCALE_FACTOR_DRAW
: npm_w <= Value.BishopValueMg ? 4 : 14);
}
if (pos.count(PieceType.PAWN, Color.WHITE) == 1 && npm_w - npm_b <= Value.BishopValueMg)
{
e.factor[Color.WHITE] = (ushort) ScaleFactor.SCALE_FACTOR_ONEPAWN;
}
if (pos.count(PieceType.PAWN, Color.BLACK) == 1 && npm_b - npm_w <= Value.BishopValueMg)
{
e.factor[Color.BLACK] = (ushort) ScaleFactor.SCALE_FACTOR_ONEPAWN;
}
// Evaluate the material imbalance. We use PIECE_TYPE_NONE as a place holder
// for the bishop pair "extended piece", which allows us to be more flexible
// in defining bishop pair bonuses.
int[][] PieceCount =
{
new[]
{
pos.count(PieceType.BISHOP, Color.WHITE) > 1 ? 1 : 0,
pos.count(PieceType.PAWN, Color.WHITE), pos.count(PieceType.KNIGHT, Color.WHITE),
pos.count(PieceType.BISHOP, Color.WHITE), pos.count(PieceType.ROOK, Color.WHITE),
pos.count(PieceType.QUEEN, Color.WHITE)
},
new[]
{
pos.count(PieceType.BISHOP, Color.BLACK) > 1 ? 1 : 0,
pos.count(PieceType.PAWN, Color.BLACK), pos.count(PieceType.KNIGHT, Color.BLACK),
pos.count(PieceType.BISHOP, Color.BLACK), pos.count(PieceType.ROOK, Color.BLACK),
pos.count(PieceType.QUEEN, Color.BLACK)
}
};
e.value = (short) ((imbalance(Color.WHITE, PieceCount) - imbalance(Color.BLACK, PieceCount))/16);
return e;
}
/// evaluate() is the main evaluation function. It returns a static evaluation
/// of the position always from the point of view of the side to move.
internal static ValueT evaluate(bool DoTrace, Position pos)
{
Debug.Assert(pos.checkers() == 0);
var ei = new EvalInfo();
ScoreT[] mobility = {Score.SCORE_ZERO, Score.SCORE_ZERO};
// Initialize score by reading the incrementally updated scores included
// in the position object (material + piece square tables).
// Score is computed from the point of view of white.
var score = pos.psq_score();
// Probe the material hash table
var me = Material.probe(pos);
score += me.imbalance();
// If we have a specialized evaluation function for the current material
// configuration, call it and return.
if (me.specialized_eval_exists())
{
return me.evaluate(pos);
}
// Probe the pawn hash table
ei.pi = Pawns.probe(pos);
score += Score.Multiply(ei.pi.pawns_score(), Weights[PawnStructure]);
// Initialize attack and king safety bitboards
ei.attackedBy[Color.WHITE, PieceType.ALL_PIECES] =
ei.attackedBy[Color.BLACK, PieceType.ALL_PIECES] = Bitboard.Create(0);
init_eval_info(Color.WHITE, pos, ei);
init_eval_info(Color.BLACK, pos, ei);
// Pawns blocked or on ranks 2 and 3. Will be excluded from the mobility area
BitboardT[] blockedPawns =
{
pos.pieces_CtPt(Color.WHITE, PieceType.PAWN)
& (Bitboard.shift_bb(Square.DELTA_S, pos.pieces()) | Bitboard.Rank2BB
| Bitboard.Rank3BB),
pos.pieces_CtPt(Color.BLACK, PieceType.PAWN)
& (Bitboard.shift_bb(Square.DELTA_N, pos.pieces()) | Bitboard.Rank7BB
| Bitboard.Rank6BB)
};
// Do not include in mobility squares protected by enemy pawns, or occupied
// by our blocked pawns or king.
BitboardT[] mobilityArea =
{
~(Bitboard.OrWithSquare(ei.attackedBy[Color.BLACK, PieceType.PAWN] | blockedPawns[Color.WHITE]
, pos.square(PieceType.KING, Color.WHITE))),
~(Bitboard.OrWithSquare(ei.attackedBy[Color.WHITE, PieceType.PAWN] | blockedPawns[Color.BLACK]
, pos.square(PieceType.KING, Color.BLACK)))
};
// Evaluate pieces and mobility
score += evaluate_pieces(PieceType.KNIGHT, Color.WHITE, DoTrace, pos, ei, mobility, mobilityArea);
score += Score.Multiply(mobility[Color.WHITE] - mobility[Color.BLACK], Weights[Mobility]);
// Evaluate kings after all other pieces because we need complete attack
// information when computing the king safety evaluation.
score += evaluate_king(Color.WHITE, DoTrace, pos, ei) - evaluate_king(Color.BLACK, DoTrace, pos, ei);
// Evaluate tactical threats, we need full attack information including king
score += evaluate_threats(Color.WHITE, DoTrace, pos, ei) - evaluate_threats(Color.BLACK, DoTrace, pos, ei);
// Evaluate passed pawns, we need full attack information including king
score += evaluate_passed_pawns(Color.WHITE, DoTrace, pos, ei)
- evaluate_passed_pawns(Color.BLACK, DoTrace, pos, ei);
// If both sides have only pawns, score for potential unstoppable pawns
if (pos.non_pawn_material(Color.WHITE) == 0 && pos.non_pawn_material(Color.BLACK) == 0)
{
BitboardT b;
if ((b = ei.pi.passed_pawns(Color.WHITE)) != 0)
{
score += Rank.relative_rank_CtSt(Color.WHITE, Utils.frontmost_sq(Color.WHITE, b)) * Unstoppable;
}
if ((b = ei.pi.passed_pawns(Color.BLACK)) != 0)
{
score -= Rank.relative_rank_CtSt(Color.BLACK, Utils.frontmost_sq(Color.BLACK, b)) * Unstoppable;
}
}
// Evaluate space for both sides, only during opening
if (pos.non_pawn_material(Color.WHITE) + pos.non_pawn_material(Color.BLACK) >= 12222)
{
score += Score.Multiply(evaluate_space(Color.WHITE, pos, ei) - evaluate_space(Color.BLACK, pos, ei), Weights[Space]);
}
// Scale winning side if position is more drawish than it appears
var strongSide = Score.eg_value(score) > Value.VALUE_DRAW ? Color.WHITE : Color.BLACK;
var sf = me.scale_factor(pos, strongSide);
// If we don't already have an unusual scale factor, check for certain
// types of endgames, and use a lower scale for those.
if (me.game_phase() < Phase.PHASE_MIDGAME
&& (sf == ScaleFactor.SCALE_FACTOR_NORMAL || sf == ScaleFactor.SCALE_FACTOR_ONEPAWN))
{
if (pos.opposite_bishops())
{
// Endgame with opposite-colored bishops and no other pieces (ignoring pawns)
// is almost a draw, in case of KBP vs KB is even more a draw.
if (pos.non_pawn_material(Color.WHITE) == Value.BishopValueMg
&& pos.non_pawn_material(Color.BLACK) == Value.BishopValueMg)
{
sf = Bitboard.more_than_one(pos.pieces_Pt(PieceType.PAWN)) ? (ScaleFactor) (31) : (ScaleFactor) (9);
}
// Endgame with opposite-colored bishops, but also other pieces. Still
// a bit drawish, but not as drawish as with only the two bishops.
else
{
sf = (ScaleFactor) (46*(int) sf/(int) ScaleFactor.SCALE_FACTOR_NORMAL);
}
}
// Endings where weaker side can place his king in front of the opponent's
// pawns are drawish.
else if (Math.Abs(Score.eg_value(score)) <= Value.BishopValueEg && ei.pi.pawn_span(strongSide) <= 1
&& !pos.pawn_passed(Color.opposite(strongSide), pos.square(PieceType.KING, Color.opposite(strongSide))))
{
sf = ei.pi.pawn_span(strongSide) != 0 ? (ScaleFactor) (51) : (ScaleFactor) (37);
}
}
// Scale endgame by number of pawns
var p = pos.count(PieceType.PAWN, Color.WHITE) + pos.count(PieceType.PAWN, Color.BLACK);
var vEg = 1 + Math.Abs(Score.eg_value(score));
sf = (ScaleFactor) (Math.Max((int) sf/2, (int) sf - 8*(int) ScaleFactor.SCALE_FACTOR_NORMAL*(12 - p)/vEg));
// Interpolate between a middlegame and a (scaled by 'sf') endgame score
var v = Score.mg_value(score)*(int) (me.game_phase())
+ Score.eg_value(score)*(Phase.PHASE_MIDGAME - me.game_phase())*(int) sf
/(int) ScaleFactor.SCALE_FACTOR_NORMAL;
v /= (int) (Phase.PHASE_MIDGAME);
// In case of tracing add all single evaluation terms
if (DoTrace)
{
add_IdxSt((int) Term.MATERIAL, pos.psq_score());
add_IdxSt((int) Term.IMBALANCE, me.imbalance());
add_IdxSt(PieceType.PAWN, ei.pi.pawns_score());
add_IdxStSt(
(int) Term.MOBILITY,
Score.Multiply(mobility[Color.WHITE], Weights[Mobility]),
Score.Multiply(mobility[Color.BLACK], Weights[Mobility]));
add_IdxStSt(
(int) Term.SPACE,
Score.Multiply(evaluate_space(Color.WHITE, pos, ei), Weights[Space]),
Score.Multiply(evaluate_space(Color.BLACK, pos, ei), Weights[Space]));
add_IdxSt((int) Term.TOTAL, score);
}
return (pos.side_to_move() == Color.WHITE ? v : -v) + Tempo; // Side to move point of view
}
// evaluate_pieces() assigns bonuses and penalties to the pieces of a given color
private static ScoreT evaluate_pieces(
PieceTypeT pieceType,
ColorT Us,
bool DoTrace,
Position pos,
EvalInfo ei,
ScoreT[] mobility,
BitboardT[] mobilityArea)
{
int Pt = pieceType;
if (Pt == PieceType.KING)
{
return Score.SCORE_ZERO;
}
var score = Score.SCORE_ZERO;
var NextPt = (Us == Color.WHITE ? pieceType : pieceType + 1);
var Them = (Us == Color.WHITE ? Color.BLACK : Color.WHITE);
ei.attackedBy[Us, Pt] = Bitboard.Create(0);
for(var idx=0; idx<16;idx++)
{
var s = pos.square(pieceType, Us, idx);
if (s == Square.SQ_NONE)
{
break;
}
// Find attacked squares, including x-ray attacks for bishops and rooks
var b = Pt == PieceType.BISHOP
? Utils.attacks_bb_PtSBb(PieceType.BISHOP, s, pos.pieces() ^ pos.pieces_CtPt(Us, PieceType.QUEEN))
: Pt == PieceType.ROOK
? Utils.attacks_bb_PtSBb(
PieceType.ROOK,
s,
pos.pieces() ^ pos.pieces_CtPtPt(Us, PieceType.ROOK, PieceType.QUEEN))
: pos.attacks_from_PtS(pieceType, s);
if (Bitboard.AndWithSquare(ei.pinnedPieces[Us], s)!=0)
{
b &= Utils.LineBB[pos.square(PieceType.KING, Us), s];
}
ei.attackedBy[Us, PieceType.ALL_PIECES] |= ei.attackedBy[Us, Pt] |= b;
if ((b & ei.kingRing[Them])!=0)
{
ei.kingAttackersCount[Us]++;
ei.kingAttackersWeight[Us] += KingAttackWeights[Pt];
var bb = b & ei.attackedBy[Them, PieceType.KING];
if (bb!=0)
{
ei.kingAdjacentZoneAttacksCount[Us] += Bitcount.popcount_Max15(bb);
}
}
if (Pt == PieceType.QUEEN)
{
b &=
~(ei.attackedBy[Them, PieceType.KNIGHT] | ei.attackedBy[Them, PieceType.BISHOP]
| ei.attackedBy[Them, PieceType.ROOK]);
}
var mob = Pt == PieceType.QUEEN
? Bitcount.popcount_Full(b & mobilityArea[Us])
: Bitcount.popcount_Max15(b & mobilityArea[Us]);
mobility[Us] += MobilityBonus[Pt][mob];
if (Pt == PieceType.BISHOP || Pt == PieceType.KNIGHT)
{
// Bonus for outpost square
if (Rank.relative_rank_CtSt(Us, s) >= Rank.RANK_4 && Rank.relative_rank_CtSt(Us, s) <= Rank.RANK_6
&& (pos.pieces_CtPt(Them, PieceType.PAWN) & Utils.pawn_attack_span(Us, s))==0)
{
score +=
Outpost[Pt == PieceType.BISHOP ? 1 : 0][Bitboard.AndWithSquare(ei.attackedBy[Us, PieceType.PAWN], s)!=0 ? 1 : 0];
}
// Bonus when behind a pawn
if (Rank.relative_rank_CtSt(Us, s) < Rank.RANK_5 && Bitboard.AndWithSquare(pos.pieces_Pt(PieceType.PAWN), (s + Square.pawn_push(Us)))!=0)
{
score += MinorBehindPawn;
}
// Penalty for pawns on same color square of bishop
if (Pt == PieceType.BISHOP)
{
score -= BishopPawns*ei.pi.pawns_on_same_color_squares(Us, s);
}
// 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 == PieceType.BISHOP && pos.is_chess960()
&& (s == Square.relative_square(Us, Square.SQ_A1) || s == Square.relative_square(Us, Square.SQ_H1)))
{
var d = Square.pawn_push(Us) + (Square.file_of(s) == File.FILE_A ? Square.DELTA_E : Square.DELTA_W);
if (pos.piece_on(s + d) == Piece.make_piece(Us, PieceType.PAWN))
{
score -= !pos.empty(s + d + Square.pawn_push(Us))
? TrappedBishopA1H1*4
: pos.piece_on(s + d + d) == Piece.make_piece(Us, PieceType.PAWN)
? TrappedBishopA1H1*2
: TrappedBishopA1H1;
}
}
}
if (Pt == PieceType.ROOK)
{
// Bonus for aligning with enemy pawns on the same rank/file
if (Rank.relative_rank_CtSt(Us, s) >= Rank.RANK_5)
{
var alignedPawns = pos.pieces_CtPt(Them, PieceType.PAWN) & Utils.PseudoAttacks[PieceType.ROOK, s];
if (alignedPawns!=0)
{
score += Bitcount.popcount_Max15(alignedPawns)*RookOnPawn;
}
}
// Bonus when on an open or semi-open file
if (ei.pi.semiopen_file(Us, Square.file_of(s)) != 0)
{
score += ei.pi.semiopen_file(Them, Square.file_of(s)) != 0 ? RookOnOpenFile : RookOnSemiOpenFile;
}
// Penalize when trapped by the king, even more if king cannot castle
if (mob <= 3 && 0 == ei.pi.semiopen_file(Us, Square.file_of(s)))
{
var ksq = pos.square(PieceType.KING, Us);
if (((Square.file_of(ksq) < File.FILE_E) == (Square.file_of(s) < Square.file_of(ksq)))
&& (Square.rank_of(ksq) == Square.rank_of(s) || Rank.relative_rank_CtSt(Us, ksq) == Rank.RANK_1)
&& 0 == ei.pi.semiopen_side(Us, Square.file_of(ksq), Square.file_of(s) < Square.file_of(ksq)))
{
score -= (TrappedRook - Score.make_score(mob*22, 0))*(1 + (pos.can_castle(Us) == 0 ? 1 : 0));
}
}
}
}
if (DoTrace)
{
add_IdxCtSt(Pt, Us, score);
}
// Recursively call evaluate_pieces() of next piece type until KING excluded
return score - evaluate_pieces(NextPt, Them, DoTrace, pos, ei, mobility, mobilityArea);
}
