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

[Matthew Knepley]

On Fri, Mar 22, 2019 at 1:41 PM Swarnava Ghosh <swarnava89 at gmail.com> wrote:

> Hi Mark and Matt,
>
> Thank you for your responses.
>  "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"
> Yes, that is correct. We would want a vertex partitioning.
>

Okay, I need to understand better what you want. A vertex partition of a
mesh does not make sense to me. What kind
of mesh do you have, and how do you plan to use the partitioned mesh?

  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/>
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