All code is perf-sensitive.

Also, literally every language claims "only a x2 slowdown compared to C".

We still end up coding in C++, because see the first point.

pizlonator 5 days ago | parent | next [-]

I’m not claiming only 2x slowdown. It’s 4x for some of the programs I’ve measured. 4x > 2x. I’m not here to exaggerate the perf of Fil-C. I actually think that figuring out the true perf cost is super interesting!

> 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”

▲

Sesse__ 5 days ago | parent | next [-]

FWIW, I just tested it on a random program I wrote recently, and it went from 2.085 seconds with Clang+jemalloc to 18.465 seconds with Fil-C. (No errors were reported, thank goodness!) So that's a 9x new worst case for you :-) It's basically a STL performance torture test, though. TBH I'm impressed that Fil-C just worked on the first try for this.

	▲	Sesse__ 5 days ago \| parent [-]
		And on the next one, a SIMD-heavy searcher thingie (where it found a real bug, though thankfully “only” reading junk data that would be immediately discarded!), it went from 7.723 to 379.56 seconds, a whopping 49x slowdown.

▲

otabdeveloper4 5 days ago | parent | prev [-]

All code is perf-sensitive. Not all code is important enough to be written as we'd like it to be.

▲

zelphirkalt 5 days ago | parent | next [-]

We don't like all code to be written in some C or C++ dialect.

▲

gf000 5 days ago | parent | prev [-]

Then why use C? Take a look at actually perf-sensitive hot loops, and they are predominantly some inline assembly with a bunch of SIMD hacks, which can be 1000x times faster than C...

	▲	otabdeveloper4 4 days ago \| parent [-]
		Unfortunately inline assembly isn't portable even to different revisions of one CPU architecture, much less different ones.

▲

Dylan16807 5 days ago | parent | prev [-]

> All code is perf-sensitive.

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.

▲

otabdeveloper4 5 days ago | parent [-]

> I've never seen anyone claim that a language like python (using the normal implementation) is generally within the same speed band as C.

Live long enough and you will. People claimed it about PyPy back in the day when it was still hype.

	▲	Dylan16807 5 days ago \| parent [-]
		Pypy is not the normal implementation. I was specifically excluding special implementations that only do part of a language and do it much faster. Especially with something like pypy that has extremely good best case scenarios, people can get too excited.