[petsc-users] alternative for MatCreateSeqAIJWithArrays

[Barry Smith]

   Is your code sequential (with possibly OpenMP) or MPI parallel? Do you plan to make your part of the code MPI parallel?

    If it is sequential or OpenMP parallel you might consider using the new feature https://petsc.org/release/manualpages/PC/PCMPI/#pcmpi Depending on your system it is an easy way to run linear solver in parallel while the code is sequential and can give some reasonable speedup.

> On Oct 26, 2023, at 8:58 AM, Qiyue Lu <qiyuelu1 at gmail.com> wrote:
> 
> Hello,
> I am trying to incorporate PETSc as a linear solver to compute Ax=b in my code. Currently, the sequential version works. 
> 1) I have the global matrix A in CSR format and they are stored in three 1-dimensional arrays: row_ptr[ ], col_idx[ ], values[ ], and I am using MatCreateSeqAIJWithArrays to get the PETSc format matrix. This works. 
> 2) I am trying to use multicores, and when I use "srun -n 6", I got the error Comm must be of size 1 from the MatCreateSeqAIJWithArrays. Saying I cannot use SEQ function in a parallel context. 
> 3) I don't think MatCreateMPIAIJWithArrays and MatMPIAIJSetPreallocationCSR are good options for me, since I already have the global matrix as a whole. 
> 
> I wonder, from the global CSR format data, how can I reach the PETSc format matrix for parallel KSP computation. Are the MatSetValue, MatSetValues what I need?
> 
> Thanks,
> Qiyue Lu

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20231026/53ace381/attachment.html>