[a,irn,icn,ikeep,w,idisp,ifail] = f01brf(n,nz,a,irn,icn<,pivot,lblock,grow,... abort,ifail>)
Given a real sparse matrix A, this routine may be used to obtain
the LU factorization of a permutation of A,
PAQ=LU
where P and Q are permutation matrices, L is unit lower
triangular and U is upper triangular. The routine uses a sparse
variant of Gaussian elimination, and the pivotal strategy is
designed to compromise between maintaining sparsity and
controlling loss of accuracy through round-off.
Optionally the routine first permutes the matrix into block lower
triangular form and then only factorizes the diagonal blocks. For
some matrices this gives a considerable saving in storage and
execution time.
Extensive data checks are made; duplicated non-zeros can be
accumulated.
The factorization is intended to be used by F04AXF to solve
T
sparse systems of linear equations Ax=b or A x=b. If several
matrices of the same sparsity pattern are to be factorized,
F01BSF should be used for the second and subsequent matrices.
f01brf Required Input Arguments: n integer nz integer a (:) real irn (:) integer icn (:) integer Optional Input Arguments: <Default> pivot real 0.1 lblock logical 1 grow logical 1 abort (4) logical [1;1;0;1] ifail integer -1 Output Arguments: a (:) real irn (:) integer icn (:) integer ikeep (5*n) integer w (n) real idisp (10) integer ifail integer