Timo,
Thank you so much for your response! Thanks to using
make_sparsity_pattern on the individual blocks as you suggest, I now
have it working just as I want (well, mod another bug whose origin is
eluding me at the moment). It's absolutely marvelous. Thank you!
Unfortunately, I can't remember the exact code that generated the error
with copy_from (I changed it so many times), but I think I was getting a
type error of some sort. I think it was looking for a
CompressedSparsityPattern--something other than a SparsityPattern (or
maybe that was when I used = ). If you'd like more information because
you want to investigate a possible issue within the library, I can try
to replicate the failed implementation that generated the error.
Best,
-J
On 05/09/2012 11:50 PM, Timo Heister wrote:
Hey Justin,
block_sparsity.block(0,0) is a SparsityPattern, so you can use
DoFTools::make_sparsity_pattern() on it.
What error are you getting if you call block_sparsity.block(0,0).copy_from() ?
On Thu, May 3, 2012 at 12:51 PM, Justin Droba<[email protected]> wrote:
Markus,
Thank you for your response.
What you say is precisely what I would like to do. I don't know how to copy
the sparsity patterns from sparsity_M et al. The copy_from method and =
operators both throw errors, so those aren't right. sparsity_M is of type
SparsityPattern. How do I assign that to block_sparsity.block(0,0)?
I cannot use the DoFTools::make_sparsity_pattern for the following reason:
in essence, I am doing an FE system without using FESystem. The components
of the system (real and imaginary parts) use the same FE space and satisfy
dual PDEs--so it's really a waste to use FESystem. It would duplicate a
whole lot of identical data and waste a lot of valuable memory. (And I'd
also prefer to avoid going through the code and modifying all the references
to FEValues to accommodate a system. :) ) By stacking up the stiffness
matrices in the right way, we can replicate the end result without needing
to generate and keep track of two sets of identical basis functions.
In other words, my dof_handler and FE objects don't know they are actually
part of a system.
I could go back and use FESystem and then make clever use of Block stuff to
avoid rewriting most of the existing code (which was just for a real
system), but I'd like to try this way first, if possible.
Thank you!
Best,
-J
On 05/03/2012 02:17 AM, Markus Bürg wrote:
Hello Justin,
did you try the following: Create a BlockSparsityPattern (2,2). Then copy
the sparsity patterns sparsity_M, sparsity_S, sparsity_T into the
corresponding blocks. Do the same with the BlockSparseMatrix.
Best Regards,
Markus
On 03.05.2012 03:42, Justin Droba wrote:
Hi,
I have three SparseMatrix objects already created, M, S, and T. I'd like to
combine them into one BlockSparseMatrix of the form A = [M, S; T, M]. All
of these matrices are the same size (square) and have the same sparsity
patterns. I've read through the documentation on BlockSparseMatrix and I
can't quite figure out how to do this. I'm sure I'm missing something
obvious (unless what I want to do is impossible!), but can someone point me
to the methods I need to use?
I'd like to do this so I can use SparseDirectUMFPACK to solve Ax = b with
the above A. The documentation says that SparseDirectUMFPACK should work
with BlockSparseMatrix objects too.
Thank you!
Best,
-J
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Justin Droba
Office: A111 Wells Hall
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Michigan State University
Department of Mathematics
East Lansing, MI 48824
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Michigan State University
Department of Mathematics
East Lansing, MI 48824
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