PETSc sparsity

[Toby D. Young]

>   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.


-- 

Toby D. Young ( Adiunkt )
Department of Computational Science
Institute of Fundamental Technical Research, Polish Academy of Sciences
Room 206, Swietokrzyska 21, 00-049 Warsaw, POLAND