BOUT-dev VS actix

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.

9. Actix

I think it's fairer to say the language got so much more powerful that there wasn't any point making actors a language feature when they can be built from existing orthogonal language features. You're probably looking for actix (not actix-web, just actix). There's also Lunatic built in Rust but supporting any actors compiled to WebAssembly.

Actix is an actor framework for developing concurrent applications built on top of the Tokio asynchronous runtime. It allows multiple actors to run on a single thread, but also allows actors to run on multiple threads via Arbiters. Actors can communicate with each other by sequentially exchanging typed messages.

I’ve seen frameworks for c++ (https://seastar.io/) and rust (https://github.com/actix/actix) which support what you’re describing out of the box.

The actix repository on github doesn't seem to be very active, and everyone seems to be focused on actix-web instead, is anyone out there using plain actix or any other actor-model implementation in Rust?

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.

I'd just use Actix for that. Make your state an actor and make it a StreamHandler for each of these sources, and that's it - now you just implement the business logic for handling each message in the StreamHandler::handle methods.

However, this isn't even 50% of what's out there: Need raw parallel power (and maybe don't need an async runtime)? Checkout Rayon. Need simple Actors for concurrent processing? Checkout Actix. Need a larger Actor system for fault tolerance/CQRS messaging? Checkout Riker. Damn, I sound like a youtube advert 🤦 - For real though, this is the tip of the concurrency iceberg. There is so much more - and it's growing.