Function controllability_matrix 

pub fn controllability_matrix(
    a: &[f64],
    b: &[f64],
    n: usize,
    m: usize,
) -> Vec<f64>

Compute the controllability matrix [B, AB, A^2B, …].

a is n-by-n, b is n-by-m (flat row-major). Returns n-by-(n*m).