Fangbo Wang <[email protected]> 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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