On Mar 25, 2013, at 2:35 PM, Bill Long <[email protected]> wrote:

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I'm strongly in favor of option 3. It is the only option that allows the possibility of underscore name mangling disappearing in the future. I think most (if not all) MPI Fortran implementations will eventually evolve to thin wrappers calling the C API.

Remember that Open MPI can never do this approach since our C handles != Fortran handles, and Fortran wrappers will not be able to reach back into the back-end C MPI objects (at least, not without a truckload of extra interop code -- the Fortran bindings layer would have to gain an understanding of the back-end MPI C objects, and that seems like a terrible idea).

6. You can isolate the issues of Fortran types (compiled with -i8, meaning of LOGICAL, character arguments with len > 1) into the Fortran wrappers so that the C library writers do not have to know about these issues. Simplifies the maintenance and testing issues for the C library code.

There's a flaw in this logic. Yes, you divorce the *bindings* between C and Fortran, but the MPI library still has to know whether INTEGER is 4 or 8 bytes (for example) so that it can send/receive them properly. I.e., the MPI datatypes are intrinsically tied to the language's native types, and are orthogonal to how the bindings are implemented. -- Jeff Squyres [email protected] For corporate legal information go to: http://www.cisco.com/web/about/doing_business/legal/cri/