actix-telepathy VS BOUT-dev

Well, one recent issue I came across recently is the lack of support for clusters. There are crates for parallelism on a local machine, but the crates wrapping MPI or coming up with a native solution are basically not maintained anymore. I've only found actix telepathy, which is not a complete solution tho, being an extension of Actix.

Rust is also another possibility: it's basically C++ but more modern with added features and safety. It can be tricky to write mathematical stuff in it, because you may not care too much about all the safety concerns Rust forces you to handle, but it can be useful to catch bugs ahead of times. Sadly, Rust seems to have no library for running programs on clusters of PCs, except maybe this one, which takes the Actor model implemented by Actix and runs it on a cluster. I don't know how tricky it is to use the Actor model for a scientific simulation, tho.

BOUT++: a framework for writing fluid and plasma simulations in curvilinear geometry

At least in my field (computational plasma physics), the majority of software is (in descending order) Fortran (e.g., SOLPS-ITER), Python (e.g., IPS; OMFIT; UEDGE), and C/C++ (e.g., BOUT++; Exascale Computing Project tools).

I don't want to paint too bleak a picture of my field - there are definitely big, well-supported projects that invest in code quality! For example, Bout++ is a fluid solver whose devs care a lot about best practices, and the folks at the Exascale Computing Project are doing great work with tools like Kokkos (GPU acceleration of HPCcodes), ADIOS (I/O for HPC), AMREX (meshes for HPC), etc.