Function inverted_generational_distance 

pub fn inverted_generational_distance(
    set: &[Vec<f64>],
    reference: &[Vec<f64>],
) -> f64

The inverted generational distance: the mean, over the points of reference, of the Euclidean distance to the nearest point of set, as pymoo’s IGD. Small only if set both lies near the reference and covers all of it.