[chris_va]

(disclaimer: I work in a Climate&Energy R&D Lab)

I don't entirely agree with the overall assertion of this article. The author has some valid points, but I think it misses the forest for the trees.

TLDR: I think Fortran tooling and HPC clusters are a self-reinforcing local maximum. They are heavily optimized for each other, but at the cost of innovation and extensibility.

For example, we'll never get a fully differentiable climate model in Fortran. The tooling does not exist, and there are not enough Fortran developers to make a serious dent in the tooling progress made outside of the HPC world. The MPI stacks these codes rely on are not great for hardware outside of a supercomputer, and Fortran codes basically are built around full interconnect. I have many PFLOPs at my disposal that I cannot use because these codes are too brittle without being entirely rewritten.

At the end of the day, everything is a Turing machine, so you can technically do whatever you want in Fortran or any other language (or mix and match), but strategically staying in Fortran leaves a lot of resources on the table.

[cbkeller]

Well Fortran was, notably, one of the first languages to have proper source-to-source autodiff (TAPENADE) [1-3], so it’s probably not impossible, though my choice for a fully differentiable climate model would personally be Julia, like the CliMA folks at Caltech [4].

[1] https://doi.org/10.1145/2450153.2450158

[2] http://www-tapenade.inria.fr:8080/tapenade/index.jsp

[3] http://www-sop.inria.fr/ecuador/tapenade/distrib/README.html

[4] https://clima.caltech.edu/