[MPI3 Fortran] Agenda for MPI3 Fortran Working group next week

N.M. Maclaren nmm1 at cam.ac.uk
Thu Jun 4 11:07:03 CDT 2009

On Jun 4 2009, Jeff Squyres wrote:
>Forgive me, but bringing ABI into this discussion is misleading at  
>best.  :-)
>There is no ABI between fortran implementations without specific  
>intent from the implementor.  For example, Open MPI and MPICH2 do not  
>have any Fortran ABI compatibility.  One simple/obvious reason for  
>this is that the integer constant values are different between the  
>two.  ...
>In short: All MPI's use the same INTEGER handle type today because  
>they have to, but that does *not* make them ABI compatible.


I have used a good half-dozen MPIs, and none were ABI compatible.  Some
of them even had multiple ABI's, corresponding to major differences in
options (e.g. 64- versus 32-bit, but quite a lot more on some systems,
such as AIX).  And that applied as much to C as to Fortran.

Once one starts making radical changes, like replacing integer handles by
opaque types, trying to maintain ABI compatibility is a lost cause.  It
could be done transparently, but only in programs that always use USE MPI.

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

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