[petsc-users] MatCompositeMerge + MatCreateRedundantMatrix

[Matthew Knepley]

On Tue, Mar 19, 2019 at 9:07 PM Marius Buerkle <mbuerkle at web.de> wrote:

> If it is not too complicated it would be nice if MPICreateSubMatricesMPI
> would be avaible for other matrices than MPIAIJ.
>

Can you give us an idea why you would want such as thing? This usually
helps people work on things. A good place to
record such reasons is in an Issue:

  https://bitbucket.org/petsc/petsc/issues?status=new&status=open

  Thanks,

     Matt


>
>
> On Mon, Mar 18, 2019 at 10:30 PM Marius Buerkle <mbuerkle at web.de> wrote:
>
>> I have another question
>> regarding MatCreateRedundantMatrix and MPICreateSubMatricesMPI. The former
>> works for MPIAIJ and  MPIDENSE and the later only for MPIAIJ. Would it be
>> possible to use MatCreateRedundantMatrix with a factored matrix
>>
>
> We usually do not have direct access to the data for factored matrices
> since it lives in the factorization package.
>
>
>> and MPICreateSubMatricesMPI with dense and/or elemental matrices ?
>>
>
> This would not be hard, it would just take time. The dense case is easy. I
> think Elemental already has such an operation, but we would have to find it
> and call it.
>
>   Thanks,
>
>     Matt
>
>> Indeed, was very easy to add. Are you going to include the Fortran
>> interface for MPICreateSubMatricesMPI  in future releases of PETSC ?
>>
>> Regarding my initial problem, thanks a lot. It works very well with
>> MPICreateSubMatricesMPI  and the solution can be implemented in a few
>> lines.
>>
>> Thanks and Best,
>>
>> Marius
>>
>>
>> On Tue, Mar 12, 2019 at 4:50 AM Marius Buerkle <mbuerkle at web.de> wrote:
>>
>>> I tried to follow your suggestions but it seems there is
>>> no MPICreateSubMatricesMPI for Fortran. Is this correct?
>>>
>>
>> We just have to write the binding. Its almost identical to
>> MatCreateSubMatrices() in src/mat/interface/ftn-custom/zmatrixf.c
>>
>>    Matt
>>
>>>
>>> On Wed, Feb 20, 2019 at 6:57 PM Marius Buerkle <mbuerkle at web.de> wrote:
>>>
>>>> ok, I think I understand now. I will give it a try and if there is some
>>>> trouble comeback to you. thanks.
>>>>
>>>
>>> Cool.
>>>
>>>    Matt
>>>
>>>
>>>>
>>>> marius
>>>>
>>>> On Tue, Feb 19, 2019 at 8:42 PM Marius Buerkle <mbuerkle at web.de> wrote:
>>>>
>>>>> ok, so it seems there is no straight forward way to transfer data
>>>>> between PETSc matrices on different subcomms. Probably doing it by "hand"
>>>>> extracting the matricies on the subcomms create a MPI_INTERCOMM transfering
>>>>> the data to PETSC_COMM_WORLD and assembling them in a new PETSc matrix
>>>>> would be possible, right?
>>>>>
>>>>
>>>> That sounds too complicated. Why not just reverse
>>>> MPICreateSubMatricesMPI()? Meaning make it collective on the whole big
>>>> communicator, so that you can swap out all the subcommunicator for the
>>>> aggregation call, just like we do in that function.
>>>> Then its really just a matter of reversing the communication call.
>>>>
>>>>    Matt
>>>>
>>>>>
>>>>> On Tue, Feb 19, 2019 at 7:12 PM Marius Buerkle <mbuerkle at web.de>
>>>>> wrote:
>>>>>
>>>>>> I see. This would work if the matrices are on different
>>>>>> subcommumicators ? Is it possible to add this functionality ?
>>>>>>
>>>>>
>>>>> Hmm, no. That is specialized to serial matrices. You need the inverse
>>>>> of MatCreateSubMatricesMPI().
>>>>>
>>>>>   Thanks,
>>>>>
>>>>>      Matt
>>>>>
>>>>>
>>>>>> marius
>>>>>>
>>>>>>
>>>>>> You basically need the inverse of MatCreateSubmatrices(). I do not
>>>>>> think we have that right now, but it could probably be done without too
>>>>>> much trouble by looking at that code.
>>>>>>
>>>>>>   Thanks,
>>>>>>
>>>>>>      Matt
>>>>>>
>>>>>> On Tue, Feb 19, 2019 at 6:15 AM Marius Buerkle via petsc-users <
>>>>>> petsc-users at mcs.anl.gov> wrote:
>>>>>>
>>>>>>> Hi !
>>>>>>>
>>>>>>> Is there some way to combine MatCompositeMerge
>>>>>>> with MatCreateRedundantMatrix? I basically want to create copies of a
>>>>>>> matrix from PETSC_COMM_WORLD to subcommunicators, do some work on each
>>>>>>> subcommunicator and than gather the results back to PETSC_COMM_WORLD,
>>>>>>> namely  I want to sum the  the invidual matrices from the subcommunicatos
>>>>>>> component wise and get the resulting matrix on PETSC_COMM_WORLD. Is this
>>>>>>> somehow possible without going through all the hassle of using MPI
>>>>>>> directly?
>>>>>>>
>>>>>>> marius
>>>>>>>
>>>>>>
>>>>>>
>>>>>> --
>>>>>> 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/>
>>>
>>
>>
>> --
>> 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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