[petsc-dev] DMGetMatrix --> DMGetMatrices?

[Matthew Knepley]

On Fri, Feb 10, 2012 at 12:05 AM, Dmitry Karpeev <karpeev at mcs.anl.gov>wrote:

>
>
> On Fri, Feb 10, 2012 at 12:01 AM, Jed Brown <jedbrown at mcs.anl.gov> wrote:
>
>> On Thu, Feb 9, 2012 at 23:55, Dmitry Karpeev <karpeev at mcs.anl.gov> wrote:
>>
>>> In a somewhat related matter, it appears that I cannot duplicate a
>>> preallocated MATXXXAIJ until it has been assembled:
>>> if my DM implementation keeps a preallocated MATSEQAIJ, which it wants
>>> to duplicate on every call to DMGetMatrix,
>>> it would have to put in fake entries before any duplication is possible.
>>>
>>
>> Doesn't it already do this (inserting 0)?
>>
> I don't think so.  Preallocating doesn't set any values and seems to leave
> the matrix marked !assembled.
> MatDuplicate for such a matrix will fail.  Assemblying it before setting
> values (just to force an assembled flag)
> will squeeze out the extra values, won't it?  I think it would just be
> reasonable to allow to duplicate unassembled
> matrices, or, better yet, have a matrix be "assembled" by default until
> MatSetValues has been called.
> But I'm not sure whether either solution will break something else.
>

Actually, preallocating does do this now. I have to change the unstructured
code to do it.

   Matt


> Dmitry.
>
>


-- 
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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