BTF 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.