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

[Van Snyder]

On Mon, 2013-08-05 at 11:06 -0500, Bill Long wrote:
> Properly implemented coarrays should be very fast on the shared-memory
> configuration of most desktops and small servers. Certainly better
> than MPI which involves additional internal memory copies.  Assigning
> an image to each core is not a requirement.  Indeed, assigning an
> image to each SMP node, and using OpenMP within the node is quite
> common.

One of the selling points for coarrays at Tokyo, if not before, is that
the implementation would decide, under the covers, whether to use
something like MPI between nodes, or something like shmem between images
on a single node.

Are we now to tell users that was a mirage?

If so, we need an additional intrinsic to inquire which images share a
node.

Otherwise, the software isn't portable.

-- 
Van Snyder                    |  What fraction of Americans believe 
Van.Snyder at jpl.nasa.gov       |  Wrestling is real and NASA is fake?
Any alleged opinions are my own and have not been approved or
disapproved by JPL, CalTech, NASA, the President, or anybody else.