[petsc-users] Use parallel PETSc linear solver in a sequential program

[Qin Lu]

Hello,

I have successfully installed a sequential PETSc's linear solver in a sequential program. The matrix has been created in CSR format and it was passed to  MatCreateSeqAIJWithArrays (instead of using MatSetValues). 

Now I want to use a parallel PETSc solver in the same sequential program, and use the same CRS matrix mentioned above. I intend to use MatCreateMPIAIJWithArrays, since I hope to pass the array direct to PETSc, instead of using MatSetValues. There a few questions:
 
1. Is there a sample code for using MatCreateMPIAIJWithArrays?
2. There seems to be a subroutine MatDistribute_MPIAIJ, but it is not in the PETSc manual. Where can I get the instruction how to use it? It would be nice if there is a sample code available.
3. Manual says the matrix will be copied by MatCreateMPIAIJWithArrays into internal format (while it is not when using MatCreateSeqAIJWithArrays), does this mean I have to call MatMPIAIJSetPreallocation first?
4. In sample code ex2.c in the manual, both MatMPIAIJSetPreallocation and MatSeqAIJSetPreallocation are called to preallocate the matrix A. Is not the first subroutine sufficient?  
 
Many thanks for your help.
 
Regards,
Qin
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