[petsc-dev] VecNestSetSubVec for VecNest.

[Jed Brown]

Yes, see also

http://www.mail-archive.com/libmesh-devel@lists.sourceforge.net/msg02047.html

http://www.mail-archive.com/libmesh-devel@lists.sourceforge.net/msg01141.html

On Oct 17, 2011 9:29 PM, "Vijay S. Mahadevan" <vijay.m at gmail.com> wrote:

>
> http://www.mail-archive.com/libmesh-devel@lists.sourceforge.net/msg02100.html??
>
> On Mon, Oct 17, 2011 at 9:25 PM, Jed Brown <jedbrown at mcs.anl.gov> wrote:
> > We discussed Vec local/global semantics on the libmesh list a year ago or
> > more. I didn't think there was a failing in the current system, but
> libmesh
> > imposes some stricter consistency on local vectors, which sometimes
> causes
> > unnecessary communication. I don't recall all the details, but we can dig
> up
> > the thread.
> >
> > On Oct 17, 2011 9:17 PM, "Vijay S. Mahadevan" <vijay.m at gmail.com> wrote:
> >>
> >> > I would not try to simultaneously change the distribution of the Vec.
> >> > That's
> >> > what VecScatter is for. VecConvert() would keep the same distribution
> >> > and
> >> > give you back a semantically identical vector of a different type.
> >>
> >> Well, I implied changing the parallel layout because of the code I've
> >> seen in say libMesh and other packages using PETSc. Their idea of
> >> localize() is often to convert a MPI vector to a locally serial vector
> >> with/without ghost nodes. I see your point on using VecScatter and so
> >> VECSEQ can still be disallowed but some form of Ghosted parallel
> >> vector conversion would still be useful.
> >>
> >> On Mon, Oct 17, 2011 at 9:00 PM, Jed Brown <jedbrown at mcs.anl.gov>
> wrote:
> >> > On Mon, Oct 17, 2011 at 20:55, Vijay S. Mahadevan <vijay.m at gmail.com>
> >> > wrote:
> >> >>
> >> >> Actually, that is quite consistent in philosophy to the merge
> >> >> operation I'm trying to perform. SEQ->MPI might still be an invalid
> >> >> operation for Vec though. Perhaps with a PETSC_DECIDE for local, it
> >> >> still could be relevant ? You can definitely specialize this for
> >> >> MPI->SEQ and Nest Vectors with a new VecReuse enum with relevant
> >> >> names.
> >> >
> >> > I would not try to simultaneously change the distribution of the Vec.
> >> > That's
> >> > what VecScatter is for. VecConvert() would keep the same distribution
> >> > and
> >> > give you back a semantically identical vector of a different type.
> >
>
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