Hello,

UmfPackLU factorization fails when the matrix is singular, which might not be a problem when all it is needed are the LU matrices.
If this factorization is not used for the solution of a system then everything is OK.

Perhaps one could have access to the last status code returned by umfpack_numeric to check if the status is:
UMFPACK_WARNING_singular_matrix: Numeric factorization was successful, but the matrix is singular. (from the manual)

Any chance of adding this to UmfPackLU?

Best regards,
João Leal

Why not. Feel free to propose a patch doing so.

I implemented the changes in order to have access to the return status of the factorization.
I've also added access to the control vector used by umfpack in case anyone would like to customize some options.

Here is the code:
http://pastebin.com/dFivurz1

Is this the appropriate place to propose a patch

It is better to put it on the bug tracker (eigen.tuxfamily.org/bz/): it will become more visible to other developers and there is no risk we forgot about it.