On 8/14/12 8:30 AM, "Jeff Squyres" <jsquy...@cisco.com> wrote:
>On Aug 14, 2012, at 10:04 AM, Barrett, Brian W wrote: > >> That's incorrect. Fortran statuses should never be passed to C >> interfaces. If you look at testany_f.c, for example, a temporary status >> is created and then passed to the C binding > >I think the issue is that there is a mix of both styles. Look at >recv_f.c, for example -- in some cases, we pass the Fortran integer array >(if the sizes are equal), and in other cases, we use a temp C MPI_Status. Sounds like a Fortran problem to me ;). >> (although, in this case, it >> would probably be more efficient to pass it directly to >> ompi_request_testany(), but that's not important here). > >Probably so. No one has undertaken an effort to have the mpif.h >interfaces directly call the back-end OMPI functions (vs. the MPI >functions). It might be worthwhile if someone has an intern / student >and wants to come up to speed on OMPI internals -- e.g., they could at >least remove some of the calls to MPI functions from performance-critical >mpif.h functions (e.g., MPI_Send, MPI_Recv, ...etc.). > >> The part that is >> important is that outside of the Fortran interfaces themselves, requests >> are always C requests. > >George and Eugene came to similar conclusions on >https://svn.open-mpi.org/trac/ompi/ticket/3218. > >However, there is a downside (as Eugene pointed out): with the C >bindings, we usually (always?) end up copying the status once (from the >back-end request to the user-specified status). If we go the >use-a-C-MPI_Status route in for the mpif.h bindings, then we'll end up >copying the status twice (back-end request -> temp C MPI_Status -> >fortran INTEGER array). I agree, although I'd prefer that over a bunch of macros in the MCA code, particularly OB1. Brian -- Brian W. Barrett Dept. 1423: Scalable System Software Sandia National Laboratories
