PETSc sparsity

Barry Smith bsmith at
Wed Jul 11 22:25:30 CDT 2007

  Yes, this requires mucking with the internals of the data
structure.  Not terribly hard but requires some thought (especially
in parallel).


I wish I had time to do this, but we don't unless more PETSc developers

On Fri, 29 Jun 2007, Toby D. Young wrote:

> >   Ok, I understand. They want to zero out all the rows AND COLUMNS
> > that associated with the zero boundary conditioned points. Since
> > PETSc sparse matrices are stored by row it is difficult to zero
> > certain columns.
> Yes, we are trying to zero out rows & columns. I think I understand the
> source of the problem myself a lot better too now; thanks for that
> comment Barry.
> >   Perhaps we could augment the CSR storage format by having an
> > additional list of locations for each column? This could be generated
> > at MatAssembly time.
> This can not be implemented by a user can it, in fact this requires some
> modification of the internals of PETSc matrices, am I right?
> Sadly, I am only a beginner in the PETSc world and therefore not "PETSc
> competent" enough to try it. :-(
> Cheers, 
> 	Toby.

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