MC25 — Permute a sparse matrix to block triangular form

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MC25 Permute a sparse matrix to block triangular form

Permutes a sparse real or complex matrix to a block lower triangular form, i.e. given a sparse matrix $A = {a_{i j}}_{n \times n}$ , it attempts to ﬁnd permutation matrices $P$ and $Q$ such that $Â = P A Q$ is block lower triangular and it returns $Â$ to the caller.