KQKREvaluationFunction EvaluateKQKR = KQKREvaluationFunction(WHITE);
KQKREvaluationFunction EvaluateKRKQ = KQKREvaluationFunction(BLACK);
+// KBB vs KN:
+KBBKNEvaluationFunction EvaluateKBBKN = KBBKNEvaluationFunction(WHITE);
+KBBKNEvaluationFunction EvaluateKNKBB = KBBKNEvaluationFunction(BLACK);
+
+// K and two minors vs K and one or two minors:
+KmmKmEvaluationFunction EvaluateKmmKm = KmmKmEvaluationFunction(WHITE);
+
/// Scaling functions
KRKBEvaluationFunction::KRKBEvaluationFunction(Color c) : EndgameEvaluationFunction(c) { }
KRKNEvaluationFunction::KRKNEvaluationFunction(Color c) : EndgameEvaluationFunction(c) { }
KQKREvaluationFunction::KQKREvaluationFunction(Color c) : EndgameEvaluationFunction(c) { }
+KBBKNEvaluationFunction::KBBKNEvaluationFunction(Color c) : EndgameEvaluationFunction(c) { }
+KmmKmEvaluationFunction::KmmKmEvaluationFunction(Color c) : EndgameEvaluationFunction(c) { }
ScalingFunction::ScalingFunction(Color c) {
}
+Value KBBKNEvaluationFunction::apply(const Position &pos) {
+ assert(pos.piece_count(strongerSide, BISHOP) == 2);
+ assert(pos.non_pawn_material(strongerSide) == 2*BishopValueMidgame);
+ assert(pos.piece_count(weakerSide, KNIGHT) == 1);
+ assert(pos.non_pawn_material(weakerSide) == KnightValueMidgame);
+ assert(pos.pawns() == EmptyBoardBB);
+
+ Value result = BishopValueEndgame;
+ Square wksq = pos.king_square(strongerSide);
+ Square bksq = pos.king_square(weakerSide);
+ Square nsq = pos.piece_list(weakerSide, KNIGHT, 0);
+
+ // Bonus for attacking king close to defending king
+ result += distance_bonus(square_distance(wksq, bksq));
+
+ // Bonus for driving the defending king and knight apart
+ result += Value(square_distance(bksq, nsq) * 32);
+
+ // Bonus for restricting the knight's mobility
+ result += Value((8 - count_1s_max_15(pos.piece_attacks<KNIGHT>(nsq))) * 8);
+
+ return (strongerSide == pos.side_to_move())? result : -result;
+}
+
+
+Value KmmKmEvaluationFunction::apply(const Position &pos) {
+ return Value(0);
+}
+
+
/// KBPKScalingFunction scales endgames where the stronger side has king,
/// bishop and one or more pawns. It checks for draws with rook pawns and a
/// bishop of the wrong color. If such a draw is detected, ScaleFactor(0) is
- (8 * square_distance(wpsq, queeningSq) +
2 * 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 <= RANK_4 && bksq > wpsq) {
+ if(square_file(bksq) == square_file(wpsq))
+ return ScaleFactor(10);
+ if(abs(square_file(bksq) - square_file(wpsq)) == 1
+ && square_distance(wksq, bksq) > 2)
+ return ScaleFactor(24 - 2 * square_distance(wksq, bksq));
+ }
+
return SCALE_FACTOR_NONE;
}
Value apply(const Position &pos);
};
+// KBB vs KN:
+class KBBKNEvaluationFunction : public EndgameEvaluationFunction {
+public:
+ KBBKNEvaluationFunction(Color C);
+ Value apply(const Position &pos);
+};
+
+// K and two minors vs K and one or two minors:
+class KmmKmEvaluationFunction : public EndgameEvaluationFunction {
+public:
+ KmmKmEvaluationFunction(Color c);
+ Value apply(const Position &pos);
+};
+
/// Abstract base class for all evaluation scaling functions:
// KQ vs KR:
extern KQKREvaluationFunction EvaluateKQKR, EvaluateKRKQ;
+// KBB vs KN:
+extern KBBKNEvaluationFunction EvaluateKBBKN, EvaluateKNKBB;
+
+// K and two minors vs K and one or two minors:
+extern KmmKmEvaluationFunction EvaluateKmmKm;
+
// KBP vs K:
extern KBPKScalingFunction ScaleKBPK, ScaleKKBP;
mi->evaluationFunction = &EvaluateKKX;
return mi;
}
+ else if ( pos.pawns() == EmptyBoardBB
+ && pos.rooks() == EmptyBoardBB
+ && pos.queens() == EmptyBoardBB)
+ {
+ // Minor piece endgame with at least one minor piece per side,
+ // and no pawns.
+ assert(pos.knights(WHITE) | pos.bishops(WHITE));
+ assert(pos.knights(BLACK) | pos.bishops(BLACK));
+
+ if ( pos.piece_count(WHITE, BISHOP) + pos.piece_count(WHITE, KNIGHT) <= 2
+ && pos.piece_count(BLACK, BISHOP) + pos.piece_count(BLACK, KNIGHT) <= 2)
+ {
+ mi->evaluationFunction = &EvaluateKmmKm;
+ return mi;
+ }
+ }
// OK, we didn't find any special evaluation function for the current
// material configuration. Is there a suitable scaling function?
add(z[W][KNIGHT][1] ^ z[B][ROOK][1], &EvaluateKNKR);
add(z[W][QUEEN][1] ^ z[B][ROOK][1], &EvaluateKQKR);
add(z[W][ROOK][1] ^ z[B][QUEEN][1], &EvaluateKRKQ);
+ add(z[W][BISHOP][2] ^ z[B][KNIGHT][1], &EvaluateKBBKN);
+ add(z[W][KNIGHT][1] ^ z[B][BISHOP][2], &EvaluateKNKBB);
add(z[W][KNIGHT][1] ^ z[W][PAWN][1], W, &ScaleKNPK);
add(z[B][KNIGHT][1] ^ z[B][PAWN][1], B, &ScaleKKNP);