(j3.2006) (SC22WG5.5141) [ukfortran] image selectors

[N.M. Maclaren]

On Dec 10 2013, Tom Clune wrote:
>On Dec 9, 2013, at 6:52 PM, Van Snyder <Van.Snyder at jpl.nasa.gov> wrote:
>
>> Better yet would be to specify the mapping from parent team to subteam.
>> If NEW_INDEX is not specified, is there really a difficulty with
>> specifying, for example, that the image indices for the subteam are in
>> the same order as the image indices in the parent team, so that image
>> index 1 for the subteam applies to the image with the smallest image
>> index in the parent team that becomes part of the subteam, etc.?
>
> I'll second that. ince many applications will be ported from MPI, the 
> principle of "least surprise" should be invoked here. Unless there is a 
> reason to the contrary, the MPI convention for subcommunicator ranks 
> should apply to subteam image indices. MPI allows redefining ranks as 
> well, but I've only used that once (maybe) in 20+ years of coding in MPI.

Yes, but I do NOT agree with that specification!  It should simply be
explicitly stated to be unspecified, thus permitting an implementation
to optimise.  Few will, but so what?


Regards,
Nick Maclaren.