Tpetra: Check whether sendbuf==recvbuf, and use MPI_IN_PLACE in that case
Created by: mhoemmen
@trilinos/tpetra This relates to #752 (closed). If sendbuf aliases recvbuf in Tpetra::Details::iallreduce, we need to use MPI_IN_PLACE to ensure correct behavior. This only works with intracommunicators, but it's worth doing nevertheless, since intercommunicators should be rare in Trilinos.