[petsc-dev] Need mechanism to set LocalToGlobal mapping in a DMShell

[Matthew Knepley]

On Thu, Feb 21, 2013 at 2:07 PM, Jed Brown <jedbrown at mcs.anl.gov> wrote:

>
> On Thu, Feb 21, 2013 at 1:05 PM, Peter Brune <prbrune at gmail.com> wrote:
>
>>
>> The Set is the issue at hand;
>>
>
> I think he needs scatters, not ISLocalToGlobalMappings, as mentioned in my
> other email.
>

Yes, he needs the local to global scatters. Rich, I think the easiest way
to do this now may be
to define your data layout as a PetscSection (these are all local) using
DMSetDefaultSection(),
and record who owns which point using a PetscSF with DMSetPointSF().

Using this information, the DM will automatically construct a scatter
between local and global,
and the CreateLocal/GlobalVector() functions will also work right. This is
what its is designed for.

Does this make sense?

   Matt


>
>
>> and it probably belongs in DMShell as a Set/SetCreate pair like
>> everything else in DMShell.
>>
>
> Yes
>



-- 
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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