The COLumn Approximate Minimum Degree ordering algorithm
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. SYMAMD is a symmetric minimum degree ordering method based on
COLAMD, available as a MATLAB-callable function. It constructs a
matrix M such that M\'*M has the same pattern as A, and then uses
COLAMD to compute a column ordering of M.