[petsc-users] beginner's, technical programming manual?

[Matthew Knepley]

On Wed, Sep 7, 2016 at 11:38 AM, Tonio Herrmann <tonioherrmann at gmail.com>
wrote:

> Thank you, Matt,
> the source codes of DMPlexComputeCellGeometryFVM and your other links seem
> to be very helpful. I think they answer most of my questions. I might come
> back with a few more detailed questions in 1-2 weeks if that is ok with you.
>

Yep, that is fine.

  Thanks,

     Matt


> Thanks
> Herrmann
>
>
> On Wed, Sep 7, 2016 at 4:39 PM, Matthew Knepley <knepley at gmail.com> wrote:
>
>> On Mon, Sep 5, 2016 at 12:52 PM, Tonio Herrmann <tonioherrmann at gmail.com>
>> wrote:
>>
>>> Hello,
>>> I am new to PETSc, and I am struggling to use it for some numerics
>>> problems. The mathematical capabilities are well explained in the manual,
>>> in several tutorials and examples.
>>>
>>> But I am stuck at every tiny step, because I cannot find the required
>>> functions for all the very basic technical details, like getting the vertex
>>> coordinates of a DMPlex, the face areas and cell volumes (if available
>>> through PETSc?). Merging two DMPlexes, that share a common boundary, into
>>> one. Extracting a boundary of one DMPlex as a new DMPlex. Etc.
>>>
>>
>> Hi Hermann,
>>
>> There is currently no introduction of the kind you want. Everything I
>> have written is geared towards solving PDEs because that
>> it what I do with most of my time, and it is what I get the most
>> questions about. However, there are some resources:
>>
>> a) Papers
>>
>>          http://arxiv.org/abs/0908.4427
>>          http://arxiv.org/abs/1506.07749
>>          http://arxiv.org/abs/1508.02470
>>          http://arxiv.org/abs/1506.06194
>>
>> b) Manpages
>>
>> For example, you can get the coordinates of a DM using
>>
>>   http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpage
>> s/DM/DMGetCoordinates.html
>>   http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpage
>> s/DM/DMGetCoordinatesLocal.html#DMGetCoordinatesLocal
>>
>> or compute things like volumes or face areas,
>>
>>   http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpage
>> s/DM/DMPlexComputeCellGeometryFVM.html
>>
>> or extracting the boundary
>>
>>   http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpage
>> s/DM/DMPlexCreateSubmesh.html
>>
>> c) Examples
>>
>> There are a lot of examples, like SNES ex12, ex62, ex77 where we use
>> these operations to solve PDEs.
>>
>> There is no operation for merging two Plex objects, but it would not be
>> hard to write, if you marked the common
>> boundary in both using a DMLabel. Plex is intended to be transparent
>> enough for users to write new operations
>> like these.
>>
>>   Thanks,
>>
>>       Matt
>>
>> Is there any technical introduction that shows how to deal with the data
>>> structures on a basic, geometrical and topological level without
>>> necessarily discussing the numerics of PDEs and equation systems?
>>>
>>> Thank you
>>> Hermann
>>>
>>
>>
>>
>> --
>> 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
>>
>
>


-- 
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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