[petsc-dev] DMDA_*PERIODIC and DMDA_XYZGHOSTED

[Barry Smith]

On Dec 7, 2010, at 1:50 PM, Jed Brown wrote:

> On Tue, Dec 7, 2010 at 20:45, Barry Smith <bsmith at mcs.anl.gov> wrote:
> Why can you not use VecAXPY() on the local Vecs?
> 
> You're absolutely right.  I must have been thinking of error control when I decided this was a problem.  You need some sort of norms and don't want to double-count the ghost entries.

   Yes, norms are an issue in the case of DMDA. When using ghosted local vectors norms are fine.

   BTW: I consider the DMDA Vec just a very special case that gets way to much attention and can sometimes distort the overall design of PETSc in issues that are not important in that non-special case.

   Barry


> 
> Jed