[MPI3 Fortran] MPI function symbol naming convention for tools

[Bill Long]

On 6/22/11 11:48 AM, Jeff Squyres wrote:
> Martin --
>
> It is important to realize the difference between the different Fortran bindings.
>
> The "old" form (via include 'mpif.h') will still be available, and (likely) use whatever mechanism an implementation used for it before (e.g., have an underlying symbol for MPI_RECV as mpi_recv, MPI_RECV, mpi_recv_, and/or mpi_recv__).  These will likely also be the same underlying symbols for the "use mpi" interface.
>
> However, the "use mpi_f08" interface uses different parameter types than mpi.h/use mpi.  So it has a different back-end function for MPI_RECV than the other two.  Modern fortran also allows us to specify what the back-end symbol name will be; hence, Craig is proposing a specific set of back-end symbol names for the "use mpi_f08" functions like MPI_RECV that will be different than those used for mpif.h and "use mpi".  This will actually allow tool authors to know for sure what the symbol names will be.
>

A bit more detail here:  If you specify BIND(C, name="Jeff") in Fortran 
the external symbol is the same as the external symbol for a C object 
named Jeff in C source code.  If the C compiler does some sort of name 
mangling for external symbols, then the Fortran compiler is required to 
do the SAME mangling on its name.  That way you can look at the Fortran 
and C statements and see the same names and know they correspond.   If, 
as is common, the C name is the same as the back-end symbol, they the 
the name= specifier does end up specifying the back-end symbol as well. 
   But the rule is in terms of the C name.

Cheers,
Bill


> So in one sense, we're not breaking tools because the use mpi_f08 interface is new.
>
> In another sense, if we mandate specific symbols for mpif.h/use mpi, we might break some tools, but put ourselves in a better place for the future.  Since a tool already has to sense which back-end symbol to use mpif.h/use mpi (lower case, caps, 1 underscore, 2 underscores -- none of which are mandated by the Fortran spec, by the way; it's just common convention), is it really a hardship to add another symbol name to check during the tools configuration/building mechanism?
>
>
>
>
> On Jun 22, 2011, at 12:12 PM, Rasmussen, Craig E wrote:
>
>>
>> On Jun 20, 2011, at 9:45 PM, Martin Schulz wrote:
>>
>>> Hi Craig, all,
>>>
>>> (I cc-ed the tools group on this as well - this is regarding the
>>> issue how the profiling interface will work with the proposed
>>> new Fortran bindings):
>>>
>>>
>>> On Jun 20, 2011, at 10:15 AM, Rasmussen, Craig E wrote:
>>>
>>>> I've talked with Jeff Squyres and we come up with naming convention that we'd like to propose for tools to have access to Fortran.
>>>>
>>>> I believe we need four different symbol naming conventions.  Consider MPI_Recv(), the four functions are
>>>>
>>>> 1. mpi_recv_f
>>>>       - This function implements (in C or Fortran) MPI_Recv with integer handles and the choice buffer passed by address.
>>>
>>> Does this mean the existing mpi_recv binding will go away?
>>> This would break any existing tool. Can we keep the old naming
>>> scheme for the old interface? Or is this intended as an additional
>>> symbol?
>>
>> Hum and YUK.  There really isn't an mpi_recv symbol as the Fortran compilers mangle the name.  We could keep the old mixed up name mangling scheme (and hopefully deprecate it) for the mpif.h usage.  This proposal give the C tools writer a common symbol name hook rather than compiler dependent mangling.
>>
>>>
>>>>
>>>> 2. mpi_recv_f_nostatus
>>>>       - This function implements (in C or Fortran) MPI_Recv with integer handles without a status variable and the choice buffer passed by address.
>>>
>>> Is this just for the new bindings?
>>
>> New bindings only but could be made available to "use mpi" users.
>>
>>>
>>>>
>>>> 3. mpi_recv_f08
>>>>       - This function implements (in C or Fortran) MPI_Recv with integer handles and the choice buffer passed via an array descriptor.
>>>>
>>>> 4. mpi_recv_f_nostatus
>>>>       - This function implements (in C or Fortran) MPI_Recv with integer handles without a status variable and the choice buffer passed via an array descriptor.
>>>
>>> I assume you mean mpi_recv_f08_nostatus?
>>
>> Yes.  But Steve requested a name change to mpi_recv_desc and mpi_recv_desc_nostatus.
>>
>>>
>>>>
>>>> Note that these functions only need to support integer handles because of the way we (thanks to Rolf) have chosen to define the handle types in the mpi_f08 module.
>>
>> I should say support integer handles in C.  If implemented in Fortran the interface would be with typed Fortran handles for mpi_recv_desc and mpi_recv_desc_nostatus.
>>
>> -craig
>> _______________________________________________
>> mpi3-fortran mailing list
>> mpi3-fortran at lists.mpi-forum.org
>> http://lists.mpi-forum.org/mailman/listinfo.cgi/mpi3-fortran
>
>

-- 
Bill Long                                           longb at cray.com
Fortran Technical Support    &                 voice: 651-605-9024
Bioinformatics Software Development            fax:   651-605-9142
Cray Inc./Cray Plaza, Suite 210/380 Jackson St./St. Paul, MN 55101