Suitesparse is a collection of libraries for computations involving sparse matrices.

the btf library is a software package for permuting a matrix into block upper triangular form. it includes a maximum transversal algorithm, which finds a permutation of a square or rectangular matrix so that it has a zero-free diagonal (if one exists); otherwise, it finds a maximal matching which maximizes the number of nonzeros on the diagonal. the package also includes a method for finding the strongly connected components of a graph. these two methods together give the permutation to block upper triangular form.