[MPIWG Fortran] [Mpi-comments] MPI_Comm_spawn_multiple: parameter description and Fortran bindings

[Bill Long]

> On Feb 8, 2018, at 3:44 PM, Jeff Squyres (jsquyres) <jsquyres at cisco.com> wrote:
> 
>> 
>> And the Fortran binding is
>> 
>> MPI_COMM_SPAWN_MULTIPLE(COUNT, ARRAY_OF_COMMANDS, ...)
>> INTEGER  COUNT
>> CHARACTER*(*) ARRAY_OF_COMMANDS(*)
>> 

Note that the character*(*) syntax is archaic (as of 25+ years ago).  The normal way of writing this is character(*). 

>> 
>> Intuitively, it seems obvious that 'array_of_commands' is an array of 'count' commands.

That is what I would assume.  The user would be responsible for declaring the array elements large enough to hold the longest command.  (All the elements of the array have the same length). 

>> 
>> That being said, the standard does not state that, and it is unclear whether 'array_of_commands' should be
>> 
>> NULL-terminated (so to speak) or not.
>> 

Fortran characters are NOT null terminated. 

>> 
>> Back to the Fortran binding, the following prototype, which is somehow consistent with 'array_of_argv',
>> 
>> could (help to) clear the confusion. The same comments also apply to the Fortran 2008 binding.
>> 
>> 
>> CHARACTER*(*) ARRAY_OF_COMMANDS(COUNT)

This is also fine, and clearer in terms of the expected minimum size of ARRAY_OF_COMMANDS.

Cheers,
Bill


>> 
>> 

Bill Long                                                                       longb at cray.com
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