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

[Gary Klimowicz]

Hi, J3.

I need your help.

At the last minute (well, last week), I was asked to sit on a panel on performance portability at the Exascale Computing Project annual meeting. Thursday. Morning.

There will be panelists representing C++, OpenMP and OpenACC and frameworks like Kokkos and Raja.

I've been asked to have one slide and some words about Fortran 2018 and performance portability. The guidelines are along the following:


Usage

·         What ECP projects are using these technologies?  Why?  Why not?

·         What's the breadth of usage outside of a particular Lab?

·         What conditions are changing that might affect adoption?

Features

·         What key values get people to try them?

·         What could be done to make them more appealing?

·         What trends are needed/happening with these topics (e.g., graphs/tasks in Kokkos, parity on CPUs for OpenACC)

·         (To panelists) Has your offering been compared quantitatively to other alternatives?

Portability

·         What factors about this programming model most affect portability?

·         What are the portability opportunities and challenges of this programming model?

·         How effectively has portability been assessed for this programming model, relative to others?

Now, that's a lot to cover.

I'm thinking that there are a few important things Fortran has that the others don't:

  *   Decades of code bases that continue to work and whose performance improves as compiler and hardware technology improves
  *   A DSL (domain-specific language) for array operations
  *   Coarrays and teams
  *   DO CONCURRENT
  *   Strong rules about data aliasing (supporting optimizations like vectorization)

I'm sure I'm missing some obvious things.

If you had 10 minutes to explain to this group why Fortran is cool again for portable performance, what would you say?

Any help you can provide will be paid back at FIDS.

Gary


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