Corbin,
I'm looking to LU factorize a ChunkSparseMatrix<double> instance (the same
type as is used in step-51). However, it seems that ChunkSparseMatrix does not
inherit from SparseMatrix, so I receive the predictable:
undefined reference to 'void
dealii::SparseDirectUMFPACK::factorize<dealii::ChunkSparseMatrix<double>
>(dealii::ChunkSparseMatrix<double> const&)'
Yes: This isn't implemented, because nobody so far saw a need to do so. The
ChunkSparseMatrix was intended to be used to make matrix-vector products
faster by using whole chunks that can be multiplied using BLAS operations.
Nobody thought of writing an interface to SparseDirectUMFPACK because if you
use the latter class, you are building a direct decomposition of the matrix
and the speed matrix-vector products are almost certainly no longer your
concern (because you're not using an iterative solver any more).
That doesn't mean that writing such an interface isn't useful: It's just that
nobody has seen a need for it in the past.
I have a few ideas around this, but I'm not sure which is simplest to do (or
whether I'm missing an easy templating/casting trick that would avoid the
problem):
1. Implement a way to copy the ChunkSparseMatrix to a SparseMatrix as an
intermediate before factorization
Yes, that would work.
2. Implement SparseDirectUMFPACK::factorize(const Matrix &matrix) directly
(this is perhaps tougher, since the function is templated by Matrix, and I
can't seem to find the explicit template instantiations in the source code)
If you look for it, there are functions that copy SparseMatrix and
BlockSparseMatrix objects to the necessary UMFPACK data structures. It
wouldn't be very difficult to add similar functions for ChunkSparseMatrix as
well, and we'd gladly take a patch of course!
3. Do away with use of ChunkSparseMatrix entirely, and simply assemble into a
SparseMatrix throughout (since I'm factorizing it anyway--perhaps this is
the truest to the intentions of the library)
That too would work. I think the question, if you intend to go with this
option, is why you chose ChunkSparseMatrix to begin with, and what effect it
would have to not use it any more.
Best
W.
--
------------------------------------------------------------------------
Wolfgang Bangerth email: [email protected]
www: http://www.math.colostate.edu/~bangerth/
--
The deal.II project is located at http://www.dealii.org/
For mailing list/forum options, see
https://groups.google.com/d/forum/dealii?hl=en
---
You received this message because you are subscribed to the Google Groups "deal.II User Group" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to [email protected].
To view this discussion on the web visit
https://groups.google.com/d/msgid/dealii/b80ac77c-d22f-0f04-3140-b9582d9e4837%40colostate.edu.
