Hacker News

How close can pure functional programming get to C?

106 points by stmonty 6 hours ago | 10 comments

Much of the difference in optimizability is that C/C++ allows you to do fairly extreme copy elision. This is important because memory bandwidth tends to be a major performance bottleneck.

C/C++ code can trivially reach into some remote bit of state and mutate it directly. The compiler rarely objects, no matter how ugly the access method or pattern. It is up to the programmer to make sure the invariants hold and the compiler can’t always see through it. These elided copies add up, though it usually has a maintainability and safety cost.

It is related to why functional languages tend to be mediocre for supercomputing in practice despite having nice properties for massive parallelism in theory.

whilenot-dev 3 hours ago

That's a nice explanation, thanks.

Are there any common resources for this kind of access methods and patterns that specifically aim to bridge the soft-/hardware gap? The best one I can come up with is Performance Analysis and Tuning on Modern CPUs[0] by Denis Bakhvalov.

[0]: https://github.com/dendibakh/perf-book

pmkary 22 minutes ago

This is kind of hacker news post and comments I like; extreme languages on extreme performance with extreme features, not types being added to a language ten gizzilion times slower than a tortoise and the post making anti-type flat-earthers getting freaked out if they have to vaccinate next.

jeffbee 3 hours ago

This seems to raise the question: is libdeflate fast? My overall impression of libdeflate is that it produces a similar output size to zstd but takes 40 times longer to do it. I realize these are different algorithms of course, but they aren't that different, both being in the Huffman line of the LZ family. So why is libdeflate considered a performance benchmark?

antonvs 3 hours ago

It’s probably just because a zstd implementation in Lean would be more difficult. The whole project depends on being able to have a correctness proof for the implementation, and implementing that for the DEFLATE algorithm is simpler.

tkz1312 23 minutes ago

https://github.com/kim-em/lean-zstd

eigenblake 4 hours ago

I'm very simple. I see Richard Feldman post. I like it. I'll leave it to the experts as to whether this is a case of opportunistic mutation.

jdw64 3 hours ago

What are some well known programs made with Roc? And I'm curious about the difficulty level of its syntax

grayrest 5 minutes ago

There are no well known programs made with Roc. It's been usable for writing real software since July or so for those of us willing to deal with compiler crashes and regular syntax/feature changes. To my knowledge there are six people producing significant amounts of software in Roc. I'm using it for a speech recognition/transcription app and the desktop environment and apps on my eink tablet, both on my own UI framework.

prerok 2 hours ago

Well, it has not even reached 0.1.0, so the language is still in early development phase. But it has interesting properties, so I would recommend experimenting with it.