[Pysparse-users] Factors in Umfpack: contribution to PySparse

[Dominique O. <dom...@gm...>]

Hello,

I wrote an addition to the UMFPack module of PySparse that lets users
retrieve the details of the factorization. Here is an example:

 from pysparse import spmatrix, umfpack
 A = spmatrix.ll_mat_from_mtx('bcsstk11.mtx')
 LU = umfpack.factorize(A)
 (L, U, P, Q, R, do_recip) = LU.lu()

The help of lu() is as follows:

-------
lu(...)
    self.lu()
    Returns L and U factors, permutation and scaling information.

    Use: (L, U, P, Q, R, do_recip) = self.lu().
    The original matrix A is factorized into
         L U = P R A Q
    where L is unit lower triangular,
          U is upper triangular,
          P and Q are permutation matrices,
          R is a row-scaling diagonal matrix such that
           the i-th row of A has been divided    by R[i] if do_recip = True,
           the i-th row of A has been multiplied by R[i] if do_recip = False.

    L and U are returned as ll_mat sparse matrices.
    P, Q and R are returned as NumPy arrays.
-------

I would very much like to see this function included in PySparse. I
will e-mail the code directly to Daniel Wheeler.

Comments welcome.

Cheers,
Dominique