Co-arrays?

[Tobias Burnus]

John Chludzinski wrote:
> One more question on my inventory list:  When will gfortran support
> co-arrays?

I admit it is a bit boring, but is has a nearly complete support for 
coarrays using a single-image, i.e. all coarray programs (which are 
programmed such that num_images() == 1 works) should run.

For proper parallelization (num_images() > 1): I think most basic 
infrastructure is there, i.e. mainly the real communication is missing. 
Probably around one person month work is required to get it working. 
(Plus some more time to refine it.) I don't know whether and how much 
progress there will be during 4.9 development. I think there is some 
chance that progress is made, but I wouldn't hold my breath.

> My contractor asked for other avenues using Fortran to improve
> performance and, of course, this brought up co-arrays.

If you are on a single shared-memory node, you could consider OpenMP; 
that's one of the simpler approaches to retrofit parallelization to the 
code. If you are using a distributed-memory machine, using MPI (Message 
Passing Interface) could be currently the better approach - contrary to 
coarrays it is very widely available and well tested. There are also a 
few other possibilities Â…

Tobias