Function compute_complete_regular_tree 

pub fn compute_complete_regular_tree<T: RealType>(
    particles: ArrayView2<'_, T>,
    max_level: usize,
    origin: &[f64; 3],
    diameter: &[f64; 3],
) -> HashSet<usize>

Create a regular octree from an array of particles.

Returns the set of all non-empty keys associated with a regular octree created from an array of particles.

Arguments

• particles - A (3, N) array of particles
• max_level - The deepest level of the tree.
• origin - The origin of the bounding box.
• diameter - The diameter of the bounding box in each dimension.