[petsc-users] scattering strategies

Matthew Knepley knepley at gmail.com
Mon Oct 17 15:46:56 CDT 2011

On Mon, Oct 17, 2011 at 3:44 PM, Wienand Drenth <w.drenth at gmail.com> wrote:

> On Mon, Oct 17, 2011 at 10:22 PM, Jed Brown <jedbrown at mcs.anl.gov> wrote:
>> On Mon, Oct 17, 2011 at 15:17, Wienand Drenth <w.drenth at gmail.com> wrote:
>> Simple solution:
>> Make a DMDA to represent your multi-dimensional layout, put your array
>> values into the Vec you get from the DM, and call VecView(). It will do a
>> parallel write and your vector will end up in the natural ordering. You can
>> VecLoad() it later or read it with other software.
> Hello Jed,
> Thanks for the quick response. I haven't thought about this DMDA approach
> and it sounds really nice. With natural ordering, I assume you mean what I
> call Petsc ordering (in any case different from the ordering imposed by the
> user)?

A DMDA is a Cartesian grid.

Natural ordering: Ordering by dimension

Petsc Ordering: Ordering contiguously on each process, which is a contiguous
rectangular piece of the grid


> regards,
> Wienand
> --
> Wienand Drenth PhD
> Eindhoven, the Netherlands

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