[MPI3 Fortran] [Mpi-comments] MPI 3.0:Fortran 2008 interface - issue with the LOGICAL kind

[Bill Long]

Hi Craig,

There were many follow-up messages in this thread....

On 3/15/13 12:16 PM, Craig Rasmussen wrote:
> On Mar 10, 2013, at 10:18 PM, Schulz, Martin wrote:
>
>> Hi all,
>>
>> I am trying to catch up with the various threads on this (sorry, last week was hectic and I didn't get to all emails). I have to admit that I am still confused why there is a problem, but we can clarify this during a phone call or during the march meeting. However, doesn't not doing BINDC create a problem, since I now have to again deal with the no/one/two underscore issue? This sounds like a bad interface design to me, especially when we starting mixing  things.
>
> Yes, I believe that removing BIND(C) entirely makes it virtually impossible for the tools community.  Not only is there the underscore issue but some implementors want to put the code in modules which makes name mangling MUCH worse.
>

I would prefer that the tools people ignore the Fortran wrappers 
completely and instead only target the underlying C functions in the MPI 
library.  If a library function is entirely replaced by a Fortran 
routine, then that routine requires a BIND(C) specifying the C name. 
Otherwise, BIND(C) would not be needed for the wrappers.   This scheme 
seems to circumvent all of the recent problems, and also make life much 
simpler for the tools people who only need to look at the C functions. 
  It also avoids the problem of aggressively optimizing compilers 
inlining and eliminating the wrappers (which would then be unavailable 
for the tools).  I would think that forcing users to throttle back 
compiler optimization just to get the tools to work would be 
counterproductive.

Cheers,
Bill


> I think the best solution is to add on to Rolf's proposal for problem A.  The addition is that there must also be a BIND(C) interface for the tools community that replaces default LOGICAL with INTEGER(C_INT).
>
> The overloaded version (INTEGER(C_INT)) will be called by implementor so that it can be intercepted by PMPI users.
>
> Martin, do you see a problem with this?  It adds an additional wrapper call, one that you don't see.  If you like we could have a phone conversation today between you and I.  Then perhaps a group conference call the week of March 25.
>
> -craig
>
>
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-- 
Bill Long                                           longb at cray.com
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