Coarray article for the upcoming GCC Summit.

[Tobias Burnus]

Bill Long wrote:
> 8) In section 7 on implementation,  I would probably lean towards the 
> general implementation in terms of GASNet rather than MPI.   GASNet is 
> generally a shorter path to the hardware, and hence more efficient.  
> Perhaps more important, the GNU version of UPC is done with GASNet (at 
> least that's my impression), and reusing work already done within the 
> GNU umbrella seems like a good idea.  In fact, pointing out that much 
> of the work done for UPC can be reused for Fortran is probably a good 
> selling point.

I was also wondering the other day whether UPC could help (see GCC's 
bugzilla PR18918). However, I have the impression that since 2006 
nothing has happend and UPC is not part of the GCC itself. I actually do 
not know  whether they have signed a copyright assignment with the FSF. 
If not, we cannot take anything from UPC.

At least the GCC UPC I found was based on GCC 4.0.x which is already 
slightly outdated:
http://www.intrepid.com/upc.html

Regarding GASNet (http://gasnet.cs.berkeley.edu/), this would be indeed 
an alternative (as I wrote in PR18918). The advantage of MPI is that is 
ubiquitous. However, GASNet seems to be faster and seems to support also 
MPI as network backend (as TCP/IP, infiniband, myrinet, ....). [By the 
way, GASNet is under a BSD-like licence.]


Has anyone experience with GCC UPC or knows their licence status 
(agreement with FSF yes/no) or whether they indent to get it merged with 
standard GCC?


> I think that having coarrays available in gfortran would be a 
> tremendous plus for the Fortran user community.
So do I, although I would expect that it takes quite a while until 
coarrays are wider used. (At least the Fortran programmers I know strive 
for large compiler compatibility (Fortran 95 without allocatable TR, 
maybe even without some new F95 features). Though with conditional 
compiling some Fortran 2003 features are creeping in.)


Tobias