[J3] [EXTERNAL] Re: C_PTR not allowed in SEQUENCE types?

[Bill Long]

> On Mar 12, 2021, at 1:35 PM, Clune, Thomas L. (GSFC-6101) via J3 <j3 at mailman.j3-fortran.org> wrote:
> 
> Agreed.  There are some multi-language scenarios where having the parallelism implemented via a library is a real advantage. 
>  
> Bill – does SHMEM then guarantee some connection between the C side and co-arrays?   Or do they just not see a need to support mixed-language parallelism?

There is a Fortran module with thin wrappers that call the C library.  I’m not sure if this is a Cray/HPE thing or something in an annex of the SHMEM spec.  The biggest SHMEM user is mainly a C shop. Os the argument that a separate Fortran interface was unnecessary carried a lot of weight. 

As is the case with MPI, you can mix the use of coarrays and SHMEM in a program as long as you follow some simple rules. 

Cheers,
Bill

>  
> 	• Tom
>  
> From: J3 <j3-bounces at mailman.j3-fortran.org> on behalf of j3 <j3 at mailman.j3-fortran.org>
> Reply-To: j3 <j3 at mailman.j3-fortran.org>
> Date: Friday, March 12, 2021 at 2:31 PM
> To: j3 <j3 at mailman.j3-fortran.org>
> Cc: Van Snyder <van.snyder at sbcglobal.net>
> Subject: [EXTERNAL] Re: [J3] C_PTR not allowed in SEQUENCE types?
> 
>  
> 
> On Fri, 2021-03-12 at 04:21 +0000, Bill Long via J3 wrote:
> 
>>> MPI has 3 Fortran interfaces. The ancient include file, mpif.h, and two modules, MPI and MPI_F08. The MPI module uses SEQUENCE while the MPI_F08 module uses BIND(C). I’ve argued in the past to get rid of both mpif.h and the MPI module, leaving only the MPI_F08 module. Those who develop Fortran tools for MPI were staunchly opposed. 
>>> 
>>>  
>>> 
>> The alternative would be to do what SHMEM did and deprecate the Fortran interface entirely, on the grounds that the capabilities provided by SHMEM are all included in Fortran already anyway, and also it makes life easier for those providing SHMEM packages. The same argument could be made for MPI. 
>> 
>>  
>> Cheers,
>> Bill
>  
> One of our codes uses PVM to talk to an IDL program to "snoop" while it's running, including graphics. I assume that could have been done with MPI also, but when we started, 25 years ago, IDL only supported PVM.
> 
>  
> 
> We defininitely cannot do that with coarrays.
> 
>  
> 

Bill Long                                                                       longb at hpe.com
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