[eigen] [Sparse][LU] scale factors |

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Hi,

`I'm using SuperLU and UmfPack backends for Sparse matrix LU
``decompositions.
``Those backends expose the P and Q permutations, but not the scaling
``factors
``(I believe that SuperLU backend gets them but does not give access[0],
``while UmfPack backend does not read the
``scaling factors [1], for UmfPack, one would also need acces to the
``do_recip flag).
`
Are there some strong reasons not to provide those access ?
Best regards,
Bernard

`PS: Is there a "nice" way to convert the permutations vectors to sparse
``matrices such that P* and *Q do the permutation ?
``I'm well aware that this would not be the proper way to perform those
``permutations, but I need thoses sparse matrices anyway
``, and my current code reading the values in the vectors and setting the
``1. by hand in the sparse matrix feels ugly.
`

`PS2: I saw that Scipy patched SuperLU [2], and while I'm against
``embedding libraries, those patches seem serious ☹
`

`[0]
``https://bitbucket.org/eigen/eigen/src/tip/unsupported/Eigen/src/SparseExtra/SuperLUSupport.h#cl-370
``[1]
``https://bitbucket.org/eigen/eigen/src/10990f843213/unsupported/Eigen/src/SparseExtra/UmfPackSupport.h#cl-306
``[2]
``http://projects.scipy.org/scipy/log/trunk/scipy/sparse/linalg/dsolve/SuperLU/SRC?rev=6355
`