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;
}
/// 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;
}
