Function mpi::ffi::PMPI_Iallreduce

pub unsafe extern fn PMPI_Iallreduce(sendbuf: *const c_void,
                                     recvbuf: *mut c_void,
                                     count: c_int,
                                     datatype: MPI_Datatype,
                                     op: MPI_Op,
                                     comm: MPI_Comm,
                                     request: *mut MPI_Request)
                                     -> c_int