[petsc-dev] VecNestSetSubVec for VecNest.

[Vijay S. Mahadevan]

Jed, I understood now what you meant but I think we might have diverged a
little. I was asking about using the VecConvert interface for converting a
Nest vector to an MPI/SEQ vector. I have the code for this but like I
mentioned, I need more tests. Let me know if you want to check out my
implementation of MergeVecSubVecs since I'm trying to integrate the
essential components on there.

Vijay
On Oct 18, 2011 12:09 AM, "Jed Brown" <jedbrown at mcs.anl.gov> wrote:

> 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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