<div dir="ltr">Dear PETSc dev team,<div>   If I want PETSc to use my own parallel partition(instead of PETSc "evenly" partition rows), I assume I can provide local rows/columns as follows. </div><div><pre style="color:rgb(0,0,0)"><a href="https://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Mat/MatCreateShell.html#MatCreateShell">MatCreateShell</a>(<a href="https://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Sys/MPI_Comm.html#MPI_Comm">MPI_Comm</a> comm,<a href="https://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Sys/PetscInt.html#PetscInt">PetscInt</a> m,<a href="https://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Sys/PetscInt.html#PetscInt">PetscInt</a> n,<a href="https://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Sys/PetscInt.html#PetscInt">PetscInt</a> M,<a href="https://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Sys/PetscInt.html#PetscInt">PetscInt</a> N,void *ctx,<a href="https://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Mat/Mat.html#Mat">Mat</a> *A)</pre></div><div>  If that's the case, what role does local columns play? Memory allocation? Should I use n (the global rows) or local rows or PETSC_DECIDE in this case?</div><div><br></div><div>Thanks,</div><div>Sam</div></div>