[wrathofmonads]

The real barrier is the C++ ecosystem. It represents the cost of losing decades of optimized, highly integrated, high-performance libraries. C++ maps almost perfectly to the hardware with minimal overhead, and it remains at the forefront of the AI revolution. It is the true engine behind Python scientific libs and even Julia (ex. EnzymeAD). Rust does not offer advantages that would meaningfully improve how we approach HPC. Once you layer the necessary unsafe operations, C++ code in practice becomes mostly functional and immutable, and lifetimes matter less beyond a certain threshold when building complex HPC simulations. Or even outsourced to a scripting layer with Python.

[amluto]

> C++ maps almost perfectly to the hardware with minimal overhead

Barely.

The C++ aliasing rules map quite poorly into hardware. C++ barely helps at all with writing correct multithreaded code, and almost all non-tiny machines have multiple CPUs. C++ cannot cleanly express the kinds of floating point semantics that are associative, and SIMD optimization care about this. C++ exceptions have huge overhead when actually thrown.

[jawilson2]

> C++ exceptions have huge overhead when actually thrown

Which is why exceptions should never really be used for control flow. In our code, an exception basically means "the program is closing imminently, you should probably clean up and leave things in a sensible state if needed."

Agree with everything else mostly. C/C++ being a "thin layer on top of hardware" was sort of true 20? 30? years ago.

[wrathofmonads]

In simulations or in game dev, the practice is to use an SoA data layout to avoid aliasing entirely. Job systems or actors are used for handling multithreading. In machine learning, most parallelism is achieved through GPU offloading or CPU intrinsics. I agree in principle with everything you’re saying, but that doesn’t mean the ecosystem isn’t creative when it comes to working around these hiccups.

[jcalvinowens]

> The C++ aliasing rules map quite poorly into hardware.

But how much does aliasing matter on modern hardware? I know you're aware of Linus' position on this, I personally find it very compelling :)

As a silly little test a few months ago, I built whole Linux systems with -fno-strict-aliasing in CFLAGS, everything I've tried on it is within 1% of the original performance.

[pjmlp]

CUDA hardware is specially designed against C++ memory model.

It wasn't initially, and then NVIDIA went through a multi-year effort to redesign the hardware.

If you're curious, there are two CppCon talks on the matter.

[colonwqbang]

Your post could be (uncharitably) paraphrased as: "once you have written correct C++ code, the drawbacks of C++ are not relevant". That is true, and the same is true of C. But it's not really a counterargument to Rust. It doesn't much help those us who have to deliver that correct code in the first place.