Are your matrix entries stored in parallel or is your current code that 
generates the rows, columns, and values sequential.

   Does your matrix have a pointwise-block structure (like from having multiple 
degrees of freedom per grid point) or is it a scalar PDE? If scalar than you 
use AIJ matrices if point wise-block structure then use BAIJ. If symmetric than 
use SBAIJ.

   How are your matrix entries generated? Via the finite element method, finite 
differences, something else? Is there a mesh, how do you handle the mesh?

   Barry


> On Apr 12, 2018, at 1:54 PM, Klaus Burkart <k_burk...@yahoo.com> wrote:
> 
> I am confused with matrix object types and which one to use in my case:
> 
> 
> I want to solve a linear system using multiple processes. The steps I am 
> struggling with is the import of the global matrix and global rhs vector into 
> applicable PETSc objects.
> 
> The global matrix is currently stored in CSR format using 3 arrays. Array one 
> contains all the row indices, array two all the column indices, array three 
> all the values of the global matrix. In addition to that, there's a vector 
> object containing the rhs vector.
> 
> I think for the vector object I should use VectorCreateMPI with m set to 
> PETSC_DECIDE?
> 
> 
> What's the matrix object I should use in my case which also takes care of the 
> allocation local matrices to the processes at a later stage i.e. creates the 
> local matrices in line with the rhs vector?
> 
> Klaus

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