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

[Mark Adams]

>
>
>
> 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/>
>
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