constrained column approximate library for sparse matrices

 Suitesparse is a collection of libraries for computations involving
 sparse matrices.
 .
 The CCOLAMD library implements the "Constrained 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.