[petsc-users] Convert mat SEQAIJ to MPIAIJ

[Matthew Knepley]

On Tue, Sep 4, 2012 at 9:52 AM, Thomas Witkowski <
thomas.witkowski at tu-dresden.de> wrote:

>
>
> http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Mat/MATNEST.html
>
>   As I wrote in my initial question, each rank contains one and only one
> seqaij matrix, which all should be joined to one global matrix such that
> each local matrix is the corresponding diagonal block of the mpiaij matrix.
> I think, this does not work with nested matrices?
>

Why does this not work? I really think you are making this harder than it
has to be.

   Matt


> Thomas
>
>
>
>>
>>  Hong
>>
>>>
>>> Thomas :
>>>
>>>> In my FETI-DP code, each rank creates a SEQAIJ matrix that represents
>>>> the discretization of the interior domain. Just for debugging, I would like
>>>> to join these sequential matrices to one global MPIAIJ matrix. This matrix
>>>> has no off diagonal nnzs and should be stored corresponding to the ranks
>>>> unknowns, thus, first all rows of the first rank and so on. What's the most
>>>> efficient way to do this? Is it possible to create this parallel matrix
>>>> just as a view of the sequential ones, so without copying the data? Thanks
>>>> for any advise.
>>>
>>>
>>>
>>> http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Mat/MatCreateMPIAIJConcatenateSeqAIJ.html
>>>
>>>  Note: entries in seqaij matrices are copied into a mpiaij matrix
>>> without
>>> inter-processor communication. Use petsc-3.3 for this function.
>>>
>>>
>>>  The function does not do what I expect. For example, if we have two
>>> mpi task and each contains one local square matrix with n rows, I want to
>>> create a global square matrix with 2n rows. This function create a
>>> non-square matrix of size 2n x n.
>>>
>>> Thomas
>>>
>>
>>


-- 
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
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