[petsc-users] Consistent domain decomposition between DMDA and DMPLEX

[Swarnava Ghosh]

"Is this a finite element Poisson solve on your coarse unstructured mesh?"
> Yes, this is a finite element Poisson solve.

Sincerely,
Swarnava

On Thu, Mar 28, 2019 at 5:09 PM Matthew Knepley <knepley at gmail.com> wrote:

> On Thu, Mar 28, 2019 at 7:24 PM Swarnava Ghosh <swarnava89 at gmail.com>
> wrote:
>
>> Hi Mark and Matt,
>>
>> I calculate my unknown fields at the nodes of my coarse unstructured
>> mesh, and then project the solution at some of the fine structured mesh
>> nodes.
>> The only global matrix I form is on the unstructured coarse mesh to do a
>> Poisson solve.
>>
>
> Is this a finite element Poisson solve on your coarse unstructured mesh?
>
>   Thanks,
>
>     Matt
>
>
>> Sincerely,
>> Swarnava
>>
>> On Thu, Mar 28, 2019 at 5:56 AM Mark Adams <mfadams at lbl.gov> wrote:
>>
>>>
>>>>
>>>> That seems like a bad tradeoff. You avoid one communication during
>>>> injection for at least that much or more during
>>>> FE assembly on that cell partition?
>>>>
>>>>
>>> I am just guessing about the purpose as a way to describing what they
>>> are asking for.
>>>
>>>
>>>>   Matt
>>>>
>>>>
>>>>>
>>>>>>   Thanks,
>>>>>>
>>>>>>     Matt
>>>>>>
>>>>>>
>>>>>>> Sincerely,
>>>>>>> Swarnava
>>>>>>>
>>>>>>> On Fri, Mar 22, 2019 at 4:08 PM Mark Adams <mfadams at lbl.gov> wrote:
>>>>>>>
>>>>>>>> Matt,
>>>>>>>> I think they want a vertex partitioning. They may have elements on
>>>>>>>> the unstructured mesh that intersect with any number of processor domains
>>>>>>>> on the structured mesh. But the unstructured mesh vertices are in the
>>>>>>>> structured mesh set of vertices. They want the partition of the
>>>>>>>> unstructured mesh vertices (ie, matrices) to be slaved to the partitioning
>>>>>>>> of the structured mesh.
>>>>>>>> Do I have that right Swarnava?
>>>>>>>> Mark
>>>>>>>>
>>>>>>>> On Fri, Mar 22, 2019 at 6:56 PM Matthew Knepley via petsc-users <
>>>>>>>> petsc-users at mcs.anl.gov> wrote:
>>>>>>>>
>>>>>>>>> On Thu, Mar 21, 2019 at 8:20 PM Swarnava Ghosh via petsc-users <
>>>>>>>>> petsc-users at mcs.anl.gov> wrote:
>>>>>>>>>
>>>>>>>>>> Dear PETSc users and developers,
>>>>>>>>>>
>>>>>>>>>> I am new to DMPLEX and had a query regarding setting up a
>>>>>>>>>> consistent domain decomposition of two meshes in PETSc.
>>>>>>>>>> I have a structured finite difference grid, managed through DMDA.
>>>>>>>>>> I have another unstructured finite element mesh managed through DMPLEX. Now
>>>>>>>>>> all the nodes in the unstructured finite element mesh also belong to the
>>>>>>>>>> set of nodes in the structured finite difference mesh (but not necessarily
>>>>>>>>>> vice-versa), and the number of nodes in DMPLEX mesh is less than the number
>>>>>>>>>> of nodes in DMDA mesh. How can I guarantee a consistent domain
>>>>>>>>>> decomposition of the two meshes? By consistent, I mean that if a process
>>>>>>>>>> has a set of nodes P from DMDA, and the same process has the set of nodes Q
>>>>>>>>>> from DMPLEX, then Q is a subset of P.
>>>>>>>>>>
>>>>>>>>>
>>>>>>>>> Okay, this is not hard. DMPlexDistribute() basically distributes
>>>>>>>>> according to a cell partition. You can use PetscPartitionerShell() to stick
>>>>>>>>> in whatever cell partition you want. You can see me doing this here:
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> https://bitbucket.org/petsc/petsc/src/e2aefa968a094f48dc384fffc7d599a60aeeb591/src/dm/impls/plex/examples/tests/ex1.c#lines-261
>>>>>>>>>
>>>>>>>>> Will that work for you?
>>>>>>>>>
>>>>>>>>>   Thanks,
>>>>>>>>>
>>>>>>>>>     Matt
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>> I look forward to your response.
>>>>>>>>>>
>>>>>>>>>> Sincerely,
>>>>>>>>>> Swarnava
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>
>>>>>>>>> --
>>>>>>>>> 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
>>>>>>>>>
>>>>>>>>> https://www.cse.buffalo.edu/~knepley/
>>>>>>>>> <http://www.cse.buffalo.edu/~knepley/>
>>>>>>>>>
>>>>>>>>
>>>>>>
>>>>>> --
>>>>>> 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
>>>>>>
>>>>>> https://www.cse.buffalo.edu/~knepley/
>>>>>> <http://www.cse.buffalo.edu/~knepley/>
>>>>>>
>>>>>
>>>>
>>>> --
>>>> 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
>>>>
>>>> https://www.cse.buffalo.edu/~knepley/
>>>> <http://www.cse.buffalo.edu/~knepley/>
>>>>
>>>
>
> --
> 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
>
> https://www.cse.buffalo.edu/~knepley/
> <http://www.cse.buffalo.edu/~knepley/>
>
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