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Date: 10 Dec 2013 09:23:02 +0000
From: "N.M. Maclaren" <nmm1@cam.ac.uk>
To: Tom Clune <Thomas.L.Clune@nasa.gov>
Cc: sc22wg5 <sc22wg5@open-std.org>
Subject: Re: [ukfortran] (SC22WG5.5139) (j3.2006)   image selectors
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On Dec 10 2013, Tom Clune wrote:
>On Dec 9, 2013, at 6:52 PM, Van Snyder <Van.Snyder@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.