[MPI3 Fortran] MPI buffer arguments - void and call-by-reference

[N.M. Maclaren]

>The only one of those that ABSOLUTELY blocks copy-in/copy-out and the
>more-or-less equivalent optimisations is VOLATILE.  ASYNCHRONOUS does
>the least blocking, and is therefore the most efficient.

Ugh.  I have thought of a case where even VOLATILE doesn't block
copy-in/copy-out, but it's irrelevant to this debate.

I am also pretty sure that I can construct an example where TARGET
isn't enough to make MPI non-blocking transfers safe, but would need
to check that with the standard very carefully.


Regards,
Nick Maclaren,
University of Cambridge Computing Service,
New Museums Site, Pembroke Street, Cambridge CB2 3QH, England.
Email:  nmm1 at cam.ac.uk
Tel.:  +44 1223 334761    Fax:  +44 1223 334679