[J3] Performance Portability and Fortran: Making Fortran cool again

[Gary Klimowicz]

> On 1/17/19, 12:11 PM, "J3 on behalf of Ondřej Čertík via J3" <j3-bounces at mailman.j3-fortran.org on behalf of j3 at mailman.j3-fortran.org> wrote:

   >  
    
    > On Thu, Jan 17, 2019, at 9:21 AM, Tom Clune via J3 wrote:
    > > A colleague just shared a link that seems relevant to one of the 
    > > subthreads of this discussion:
    > > 
    > > https://www.nextplatform.com/2019/01/16/burying-the-openmp-versus-openacc-hatchet/
    > > 
    > > Note - I think the author has stated things exactly backwards in 
    > > several places, but I think the committee will generally like the 
    > > conclusion at the end.
    
    
    > This is a very good article, thanks for sharing it. I am wondering which things you think are stated backwards?
    
    > I discussed the "do concurrent" approach with several people at work and we arrived at the same conclusion as this article, that the compiler should simply offload "do concurrent" to a GPU and the GPU specific options that you currently specify in the OpenACC pragma, such as:
    
    > !$acc kernels loop gang(32), vector(16)
    
    > should become compiler options, that the user specifies when compiling for a given GPU. This is equivalent to how Kokkos works: you specify these options at configure time, they are not part of the source code.
    
    > This answers my question for an email above how it should be designed.
    
    > Ondrej
    
PGI had a demo at Supercomputing in November showing exactly that: undecorated DO CONCURRENT with GPU offload. It was just a demo, but it's clearly an important implementation direction.

And if I understand Ondrej's comment correctly, I agree that the optimization hints belong at configure time or runtime, and not be part of source code itself.

Gary


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