[petsc-users] How can I do reduction operation for Petsc vectors in splitted communicators?

[Jed Brown]

Fangbo Wang <fangbowa at buffalo.edu> writes:

> Hi,
>
> Assume I did MPI_Comm_split, the global communicator is splitted into
> several disjoint communicators.
>
> I created a parallel Petsc vector with same size in all the small
> communicators.
> How can I do a reduction operation for this Petsc vector among all the
> small communicators?

VecNorm (and related functions) on the Vecs created using a communicator
are done exclusively on that communicator.  Is that the question?  Of
course you can always use the original communicator (by creating objects
on it or by calling MPI_* functions directly).
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