(j3.2006) Comments on some of the comments

Steidel, Jon L jon.l.steidel
Wed Aug 9 22:45:15 EDT 2017


Hi Malcolm,

These edits have gone back and forth between Bill and John Reid and myself.  I started all this by expressing my concern that there is no restriction on a CHANGE TEAM or FORM TEAM using a coindexed team-variable.  My concern is that a FORM TEAM could define a different images team variable, or you could do a change team to a team variable that describes a team which the executing image is not a member of.  Do you think these things should be allowed?  John and Bill did not think that was the intent.

-jon

From: j3-bounces at mailman.j3-fortran.org [mailto:j3-bounces at mailman.j3-fortran.org] On Behalf Of Malcolm Cohen
Sent: Wednesday, August 9, 2017 9:53 PM
To: 'fortran standards email list for J3' <j3 at mailman.j3-fortran.org>
Subject: (j3.2006) Comments on some of the comments

[139:29] The assertion that it is not stated that the team value in an image selector has to be defined is false, the standard already states "shall identify the current or an ancestor team".  The suggested fix for this non-problem has forgotten that one is allowed to use assignment of team variables (after all, that's what GET_TEAM is useful for!!!).  Nothing needs to be done here and this technical change would break the language, rendering GET_TEAM unusable for this context.  Do Not Do This.

[213:3] This is wrong and completely unworkable.  The claim that something "is required" and "has not been stated" is false on the face of it (it's an internal contradiction!).  The suggested change seems to be imagining that when SYNC TEAM happens, it is the same SYNC TEAM statement being executed on every participating image.  This imagination is false.  In fact the standard already states that the SYNC occurs between SYNC TEAM executions "specifying the same team", so there is no problem that needs to be solved here.  It also breaks assignment of team variables for subsequent use in SYNC TEAM, rendering GET_TEAM unusable for this context.  Do Not Do This.

[214:27] The team-variables in FORM TEAM would appear to be already required to be separate variables by the segment rules.  There would be nothing wrong in principle with
                FORM TEAM ( myteam(this_image())[1], ...)
which is allowed by the coarray TS.  This usage might be unusual, but it's not inconceivable or wrong.

This would not be a disaster (unlike the two preceding), but it would still be a gratuitous incompatibility with the coarray TS.  Please don't insert more gratuitous incompatibilities.

P.S. I am not planning to participate in the telecon seeing as how it's at 2am my time...

Cheers,
--
..............Malcolm Cohen, NAG Oxford/Tokyo.

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