It is great that Fil-C exists. This is the sort of technique that is very effective for real programs, but that developers are convinced does not work. Existence proofs cut through long circular arguments.
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Some programs have a ~4x slowdown. That's also not super common, but it happens.
Most programs are somewhere in the middle.
> for the use-cases where C/C++ are still popular
This is a myth. 99% of the C/C++ code you are using right now is not perf sensitive. It's written in C or C++ because:
- That's what it was originally written in and nobody bothered to write a better version in any other language.
- The code depends on a C/C++ library and there doesn't exist a high quality binding for that library in any other language, which forces the dev to write code in C/C++.
- C/C++ provides the best level of abstraction (memory and syscalls) for the use case.
Great examples are things like shells and text editors, where the syscalls you want to use are exposed at the highest level of fidelity in libc and if you wrote your code in any other language you'd be constrained by that language's library's limited (and perpetually outdated) view of those syscalls.
Also, literally every language claims "only a x2 slowdown compared to C".
We still end up coding in C++, because see the first point.
> All code is perf-sensitive.
That can’t possibly be true. Meta runs on PHP/Hack, which are ridiculously slow. Code running in your browser is JS, which is like 40x slower than Yolo-C++ and yet it’s fine. So many other examples of folks running code that is just hella slow, way slower than “4x slower than C”
I'm doing some for loops in bash right now that could use 1000x more CPU cycles without me noticing.
Many programs use negligible cycles over their entire runtime. And even for programs that spend a lot of CPU and need tons of optimizations in certain spots, most of their code barely ever runs.
> Also, literally every language claims "only a x2 slowdown compared to C".
I've never seen anyone claim that a language like python (using the normal implementation) is generally within the same speed band as C.
The benchmark game is an extremely rough measure but you can pretty much split languages into two groups: 1x-5x slowdown versus C, and 50x-200x slowdown versus C. Plenty of popular languages are in each group.
Live long enough and you will. People claimed it about PyPy back in the day when it was still hype.