Dear Petsc-dev;
Sorry to bring this up again.
I am trying to fit Dirchlet boundary conditions on a matrix and retain
a symmetric matrix after this operation and have run into some difficulty.
Let me pose my question in another way: Is there a Gaussian elimination in
the form of an LU decomposit
>How are you applying boundary conditions? That requires the
> sparsity pattern?
I am trying to apply Dirchlet boundary conditions, ie. solution = 0 on
all boundaries. This, as I understand it, requires a Guass elimination
process to keep the final matrix symmetric. If it really is necessary
> I actually have a "bug" in Prometheus that makes me want the sparse
> structure of whole system,
It would be very useful to have sparsity information at hand.
There are many ways to solve a system. My preferred way is (1) assemble
system, (2) apply boundary conditions, and (3) solve. However
Barry,
Thank you for an interesting response.
> For algorithms that require dealing with the sparsity structure of
> the matrix we generally just include the appropriate private include file
> for the matrix format and access the data directly in the underlying format.
Can you please elabora
> If I understand you correctly, a trick we use for this is to use
> MatGetRow to get the sparcity pattern of each row (where you are
> applying BCs)
Neat trick. MatGetRow will give me the row of the matrix, so would then
need a little loop to examine the elements and proceed as you suggested;
a
Hello petsc-users and petsc-dev.
I am using PETSc to solve finite element problems. In particular I am
working with the dealii package which has C++ wrappers designed to
interface with PETSc. I am working on developing some of these wrappers.
The difficulty I face is that, after applying bounda
