[petsc-dev] Ghost update in VecAssembly?

[Matthew Knepley]

On Tue, Mar 1, 2016 at 8:23 AM, Jed Brown <jed at jedbrown.org> wrote:

> Matthew Knepley <knepley at gmail.com> writes:
> >> ghost values.  Also, who uses VecGhost _and_ VecAssembly for the same
> >> Vec?  That's quite wasteful; if you have local indexing, why not just
> >> use VecGhostUpdate(...,SCATTER_REVERSE)?
> >>
> >
> > I do not understand this argument. If you form the local part of each
> vector
> > using VecGetArray(), then you must call both VecAssembly()
>
> No.  You only need to call VecAssembly if you use VecSetValues.  But if
>

I thought we had state increase on getarray() as well, but its just locking.


> you have a ghosted vector, you would normally use VecGetArray and never
> bother with VecSetValues.


Why would we assume people make the ghost values as well? However, if this
is the only case, I don't think putting it in is a great idea.

  Matt


> > and VecGhostUpdate(), which I think is the complaint.
>
>


-- 
What most experimenters take for granted before they begin their
experiments is infinitely more interesting than any results to which their
experiments lead.
-- Norbert Wiener
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