[petsc-users] Convert mat SEQAIJ to MPIAIJ

[Thomas Witkowski]

Am 03.09.2012 18:02, schrieb Hong Zhang:
>
>
> 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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