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Why Rust for Low-Level Linux Programming?

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Re: Why Rust for Low-Level Linux Programming?

#41

Post by enraged_camel »

Thaxll wrote: post #35
TheMagicHorsey wrote: post #11

Is there any reason why embedded software for autonomous vehicles is still being written in C/C++? This last week I was talking to a friend at a company that makes a small autonomous vehicle. During testing their prototype suddenly went off in a straight line. They had to pull a safety to halt the vehicle or it would have gone straight forever into the Pacific Ocean. Turns out there was an unsafe access to a variable…

Rust is not stable. The language is not battle tested like C/C++.

Can you give specific examples of this alleged lack of stability?

Re: Why Rust for Low-Level Linux Programming?

#42

Post by outworlder »

bjourne wrote: post #33

Performance. Rust is still twice as slow as C ( http://benchmarksgame.alioth.debian.org/u64q/performance.php... ) which is still a fair bit slower than if a skilled assembly programmer had taken on the task. Rust aficionados will say that their compiler is getting better, but so is C. clang has gotten faster than gcc on some benchmarks and on some others gcc has catched up and is now faster than clang again. But what…

There's a pretty big chasm between "only 2x as slow as C" and "not needing optimal performance". That's even assuming it is generally true and a constant 2x factor.

How many skilled assembly programmers you know that are able to write better code than the collective intelligence embedded in current compilers? Even if you have a few of them handy, then aren't their resources better spent in hand-optimizing the compiler output for critical sections only?

Re: Why Rust for Low-Level Linux Programming?

#43

Post by valarauca1 »

bjourne wrote: post #33

Performance. Rust is still twice as slow as C ( http://benchmarksgame.alioth.debian.org/u64q/performance.php... ) which is still a fair bit slower than if a skilled assembly programmer had taken on the task. Rust aficionados will say that their compiler is getting better, but so is C. clang has gotten faster than gcc on some benchmarks and on some others gcc has catched up and is now faster than clang again. But what…

This difference on this test is caused by Rust not having stabilized SIMD support. Also Rust support hand rolled assembly (on nightly) that C has.

On non-SIMD tasks Rust/C are neck and neck https://benchmarksgame.alioth.debian.org/u64q/rust.html

You're just cherry picking benchmarks. In the cases you care about raw number crunching power you'll likely be using a GPU not SIMD instructions as CPU's are roughly 3-4 orders of magnitude slower then GPU's at pure number crunching tasks.

Not that SIMD isn't important as it's instructions also cover things like AES, SHA1/2, Random numbers, Cache pre-loading/evacuation, memory fences, and fast loading paths. But so few programmers worry about these things you are really hitting a niche market.

Re: Why Rust for Low-Level Linux Programming?

#44

Post by Manishearth »

bjourne wrote: post #33

Performance. Rust is still twice as slow as C ( http://benchmarksgame.alioth.debian.org/u64q/performance.php... ) which is still a fair bit slower than if a skilled assembly programmer had taken on the task. Rust aficionados will say that their compiler is getting better, but so is C. clang has gotten faster than gcc on some benchmarks and on some others gcc has catched up and is now faster than clang again. But what…

Most of the slower benchmarks were fixed and just need to be merged iirc.

I don't have much faith in microbenchmarks. Usually all they measure is how much effort the author put into overoptimizing code.

Re: Why Rust for Low-Level Linux Programming?

#45

Post by jerf »

TheMagicHorsey wrote: post #11

Is there any reason why embedded software for autonomous vehicles is still being written in C/C++? This last week I was talking to a friend at a company that makes a small autonomous vehicle. During testing their prototype suddenly went off in a straight line. They had to pull a safety to halt the vehicle or it would have gone straight forever into the Pacific Ocean. Turns out there was an unsafe access to a variable…

A more productive line of questioning, rather than prodding them to convert their probably-quite-substantial codebase into a language that, with all due respect to the Rust team, is probably still a wee bit cutting edge to be putting in self-driving cars, is to ask them what static analysis tools they've been using and why their static-analysis tool missed this one.

If the answer is "no static analysis tool", there's your problem.

But as my first paragraph implied, they can't catch everything, so "we installed many layers of protection and it still got through even so" is definitely a possibility. Rust may have a different set of such issues but they will of course always exist.

Re: Why Rust for Low-Level Linux Programming?

#46

Post by outworlder »

Thaxll wrote: post #35
TheMagicHorsey wrote: post #11

Is there any reason why embedded software for autonomous vehicles is still being written in C/C++? This last week I was talking to a friend at a company that makes a small autonomous vehicle. During testing their prototype suddenly went off in a straight line. They had to pull a safety to halt the vehicle or it would have gone straight forever into the Pacific Ocean. Turns out there was an unsafe access to a variable…

Rust is not stable. The language is not battle tested like C/C++.

Yes, Rust is younger. There is less code out there running to root out undefined behavior.

Except Rust allows for less undefined behavior. I wouldn't be surprised if it improved at a faster rate then C. Or C++ ()

() Please don't say C/C++. They are different beasts.

Re: Why Rust for Low-Level Linux Programming?

#47

Post by bjourne »

frankmcsherry wrote: post #37
bjourne wrote: post #33

Performance. Rust is still twice as slow as C ( http://benchmarksgame.alioth.debian.org/u64q/performance.php... ) which is still a fair bit slower than if a skilled assembly programmer had taken on the task. Rust aficionados will say that their compiler is getting better, but so is C. clang has gotten faster than gcc on some benchmarks and on some others gcc has catched up and is now faster than clang again. But what…

Or it is faster than C ( http://benchmarksgame.alioth.debian.org/u64q/performance.php... ). Depends which link you click on.

From the looks of it, that Rust program spawns 20 threads and does the computations in parallel. The C program does it all in one thread and doesn't even utilize sse intrinsics. I know full well that The Computer Language Benchmarks Game isn't a perfect source for programming language speed arguments, but what you can you do.

Re: Why Rust for Low-Level Linux Programming?

#48

Post by AnimalMuppet »

scott_s wrote: post #6
Scarbutt wrote: post #2

Rust reduces the amount of state I need to keep track of in my brain. I doubt it, the mental overhead of doing "safe memory programming" in Rust is very high. Edit: all good replies, want to clarify and forgot to mention that I was comparing to languages with a GC, since I'm seeing Rust being used for lots of stuff, in a general purpose programming language sense (like creating web frameworks for example). Also, for…

The mental overhead of doing "safe memory programming" is high already . The difference between Rust and, say, C, is that Rust forces you to do "safe memory programming". C lets you get away with unsafe memory programming.

C lets you deliberately do unsafe memory programming, which is maybe OK if you actually know what you're doing. But C also lets you think that you're doing safe memory programming, when that is not the case.

Re: Why Rust for Low-Level Linux Programming?

#49

Post by fdr »

I'd like to be able to use something like rust, and maybe I will for smaller projects or for novelty sake, but I chafe over how slow compilation time is relative to C (not C++!) projects last I checked.

On the hardware of yesteryear, a parallel compile could build Postgres in about 45 seconds (750-1305KLOC, depending on measurement) , and user mode Linux (which doesn't compile so many drivers) in about a minute.

Re: Why Rust for Low-Level Linux Programming?

#50

Post by mkawia »

glibgil wrote: post #10
Bromskloss wrote: post #8

Earlier quoted context omitted.

> developer marketing person What is that? > They aren't going after C++ gurus or C magicians Don't they have anything to gain from using Rust?

Someone who markets to developers. The language and context should clear up the ambiguity that they don't mean they are merely a developer that works in marketing for something like, say selling potato chips

So like a lite developer advocate
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