pub fn sphere_one_max(x: &[f64]) -> f64
SphereOneMax, f(x) = Σ xᵢ² + n_b − Σ x_k, the first sum over the first ⌊n/2⌋ variables (continuous) and the second over the n_b others (0 or 1).
f(x) = Σ xᵢ² + n_b − Σ x_k
⌊n/2⌋
n_b