dolfin team mailing list archive

[Anders Logg <logg@xxxxxxxxx>]

On Fri, May 22, 2009 at 08:10:11AM +0100, Garth N. Wells wrote:
> 
> 
> Anders Logg wrote:
> > I'm looking at how to extend GenericSparsityPattern for parallel
> > assembly.
> > 
> > Currently, the interface allows the number of nonzeros per row to be
> > retrieved when initializing a matrix (through the common interface).
> > 
> > For PETSc, the interface needs to be extended to include both the
> > number of nonzeros in the diagonal block and offdiagonal blocks for
> > each row. This is already in the subclass SparsityPattern and a cast
> > is used in PETScMatrix to convert the GenericSparsityPattern to a
> > SparsityPattern so the offdiagonal nonzeros may be retrieved.
> > 
> > For Epetra, we have a subclass EpetraSparsityPattern and also a cast
> > in EpetraMatrix.
> > 
> > So, what would be a sensible way to design/implement the different
> > sparsity patterns? One option could be to extend
> > GenericSparsityPattern with the stuff needed for PETSc, and just have
> > those functions return an error for Epetra. There would then be a
> > single cast (in EpetraMatrix) and all backends except Epetra would use
> > the SparsityPattern implementation. If so, I can go ahead and make the
> > required changes so it works with PETSc. Epetra should work as is I
> > guess, assuming Epetra_FECrsGraph& does the right thing.
> > 
> > On a side note, we build much more information in SparsityPattern than
> > we actually need for PETSc. We know all the nonzero columns but just
> > count the total number and throw away the more fine-grained
> > information. Is there a way to pass this on to PETSc and have PETSc
> > use it?
> >
> 
> This might be what you want.
> 
> http://www.mcs.anl.gov/petsc/petsc-as/snapshots/petsc-current/docs/manualpages/Mat/MatSeqAIJSetColumnIndices.html#MatSeqAIJSetColumnIndices
> 
> Garth

Looks like these might be more interesting (can't find SetColumnIndices
for MPI matrix):

http://www.mcs.anl.gov/petsc/petsc-as/snapshots/petsc-current/docs/manualpages/Mat/MatSeqAIJSetPreallocationCSR.html
http://www.mcs.anl.gov/petsc/petsc-as/snapshots/petsc-current/docs/manualpages/Mat/MatMPIAIJSetPreallocationCSR.html

-- 
Anders

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