[gh02t]

Yeah, all of that is part of the long tail. Fortran isn't going away, but with younger people who grew up without Fortran getting into leadership positions momentum is in the favor of moving HPC and sometimes more mundane computational code to C++. It's not just that developers are harder to find, it's that C++ is also offering advantages with better tooling, better libraries and community support, etc. Leveraging (and contributing to) open source is also important for DoE, which is tough in Fortran.

Of course you could make the case for even more modern languages like Rust etc as well, but the national labs are still on the conservative side when making decisions for their big projects. C++ does hit a nice sweet spot in terms of performance, features, and longevity despite the warts.