[petsc-users] Convert mat SEQAIJ to MPIAIJ

[Thomas Witkowski]

>
> 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?

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
>>
>>
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