libcolamd2 1:4.5.5-1 (armhf binary) in ubuntu bionic

 Suitesparse is a collection of libraries for computations involving
 sparse matrices.
 .
 The COLAMD library implements the "COLumn Approximate Minimum Degree ordering"
 algorithm. It computes a permutation vector P such that the LU factorization
 of A (:,P) tends to be sparser than that of A. The Cholesky factorization of
 (A (:,P))'*(A (:,P)) will also tend to be sparser than that of A'*A.