[MPI3 Fortran] Deprecate mpif.h?

N.M. Maclaren nmm1 at cam.ac.uk
Mon Mar 8 10:52:16 CST 2010

On Mar 8 2010, Bill Long wrote:
>> This is in the context of MPI choice arguments, where the information is
>> provided by the MPI datatype argument.
>> However, in general (i.e. not just MPI), TYPE(*) isn't useful unless you
>> pass the type some other way - because, except in a few cases, C needs to
>> know the actual type X to make use of the argument.  And, if an interface
>> is used only for a single type, why use TYPE(*)?
>The classic example is a 'memory copy' routine where you care about the 
>starting addresses of the source and destination and the number of bytes 
>to move, but are not interested in the type of the data represented by 
>the bits in memory.  (MPI seems to have numerous variants on this idea.)

Actually, no, it doesn't.  The buffer in MPI_Attach_buffer is the only
one I can think of.  MPI choice arguments are typed by other means, and
necessarily so, because MPI supports heterogeneous clusters.

>>> 1) Call by value.   The actual value of the argument is passed - a 
>>> concept very much like the same in C, and designed for interoperability 
>>> with C.
>> Unlike in C, it's a true read-only value, and not the initial value of
>> an updatable variable.  C people need to note that.
>Huh?  In Fortran a VALUE dummy argument gets its initial value from the 
>corresponding actual argument.  Within the subprogram, its value can 
>change, but at the return to the caller any change in the value is not 
>propagated back to the actual argument.  ...

I stand corrected.  I didn't search far enough in the standard.  Thanks
for educating me!


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