Thanks for the link, it was very informative.

I passed through the highly-irreproducible eras described in the section you link, and that you summarize in your last paragraph. There was so much different FP hardware, and so many different niche compilers, that my takeaway became “you can’t rely on reproducibility across any hardware/os version/compiler/library difference”.

There are still issues with libraries and compilers, summarized farther down (https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2025/p37...). And these can be observed in the wild when changing compilers on the same underlying hardware.

But your point is that irreproducibility at the level of interrupts or processor scheduling is not a thing on contemporary mainstream hardware. That’s important and I hadn’t realized that.