(j3.2006) [ukfortran] (SC22WG5.5059) WG5 vote on draft TS on further coarray features

[Van Snyder]

On Mon, 2013-08-05 at 16:20 -0500, Bill Long wrote:
> 
> On 8/5/13 3:46 PM, Van Snyder wrote:
> > On Mon, 2013-08-05 at 11:06 -0500, Bill Long wrote:
> >> ... Indeed, assigning an
> >> image to each SMP node, and using OpenMP within the node is quite
> >> common.


> > ... we need an additional intrinsic to inquire which images share a
> > node.
> 
> This would be most useful for forming a TEAM composed of the images on 
> the node.   In fact, Cray provides an extension  this_node() intrinsic 
> that returns your node number. The value could be used as a team ID for 
> forming such teams.
> 
> >
> > Otherwise, the software isn't portable.
> >
> 
> You would (should) write the code to be independent of the number of 
> images or their placement.   If you don't, that is not the fault of the 
> design.

It seems that if an image on an SMP node has several cores, between
which work is shared using OpenMP, one needs an intrinsic, perhaps
having nothing to do with coarrays, that shows how many cores are
available for that image.  Is this already part of OpenMP?

Are coarrays really intended to be a replacement for both OpenMP and
MPI, as originally sold at Tokyo (and earlier), or just for MPI?  It was
my understanding that the distinction between communication using an
interconnect between nodes (whether or not using a global address
space), and using shared memory on a single node, would be handled
"under the covers" by a competent coarray implementation.  Is that no
longer the expectation?