[petsc-users] Converting a Parallel(MPI) Matrix to a Sequential Matrix

[Anthony Dowling]

Okay, thank you for your help, Matthew.

Thanks,
Anthony Dowling


On Mon, Sep 7, 2020 at 11:25 AM Matthew Knepley <knepley at gmail.com> wrote:

> On Mon, Sep 7, 2020 at 11:21 AM Anthony Dowling <dowlinah at clarkson.edu>
> wrote:
>
>> But in theory, should I be able to get the rows or values from the
>> sequential matrix and insert them into a parallel matrix manually? I think
>> that would do what I need.
>>
>
> Sure, that will always work. There just isn't a function that moves
> directly from a serial matrix to a parallel matrix. You could use
> MatCreateSubMatrix() if you first
> swapped the communicator with the parallel one, which is what we would
> have to write.
>
>   Thanks,
>
>      Matt
>
>
>> Thanks,
>> Anthony Dowling
>>
>>
>> On Mon, Sep 7, 2020 at 11:20 AM Matthew Knepley <knepley at gmail.com>
>> wrote:
>>
>>> On Mon, Sep 7, 2020 at 11:17 AM Anthony Dowling <dowlinah at clarkson.edu>
>>> wrote:
>>>
>>>> Thank you for your help, Matthew.
>>>>
>>>> With those methods, will I be able to copy the contents of the created
>>>> serial matrices back to a parallel matrix if needed? If so, what is a good
>>>> way to do that?
>>>>
>>>
>>> There is nothing that does that right now. We would have to write it.
>>>
>>>   Thanks,
>>>
>>>      Matt
>>>
>>>
>>>> Thanks,
>>>> Anthony Dowling
>>>>
>>>>
>>>> On Mon, Sep 7, 2020 at 11:12 AM Matthew Knepley <knepley at gmail.com>
>>>> wrote:
>>>>
>>>>> On Mon, Sep 7, 2020 at 11:00 AM Anthony Dowling <dowlinah at clarkson.edu>
>>>>> wrote:
>>>>>
>>>>>> Hello all,
>>>>>>
>>>>>> Is there a method to convert a parallel(MPI) dense matrix to a
>>>>>> sequential dense matrix? Also to do the same in reverse? The code I am
>>>>>> using needs to be able to convert a float** matrix to a Petsc matrix, and
>>>>>> then later convert that Petsc matrix between MPI dense and sequential
>>>>>> dense. How might this be achieved? The code seems to be converting float**
>>>>>> matrices to Petsc properly, but I am unable to find a method to convert
>>>>>> between MPI and sequential matrices.
>>>>>>
>>>>>
>>>>> If you want the serial matrix everywhere, this is easy:
>>>>> https://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Mat/MatCreateRedundantMatrix.html
>>>>> If you want it just on 1 process, you can use:
>>>>> https://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Mat/MatCreateSubMatrices.html
>>>>>
>>>>>   Thanks,
>>>>>
>>>>>     Matt
>>>>>
>>>>>
>>>>>> Thanks in advance,
>>>>>> Anthony Dowling
>>>>>>
>>>>>
>>>>>
>>>>> --
>>>>> 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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