Is Rust faster than C?
steveklabnik.com
Is Rust faster than C?
1–10 of 402 posts
Re: Is Rust faster than C?
#2The article does not mention the possible additional optimisation opportunities that arise in Rust code due to stricter aliasing rules of references. But I don’t have an example in mind. Does anyone know of an example of it happening in real code?
Re: Is Rust faster than C?
#3Interesting post, but read it for the journey, not the destination[0].
[0] tldr: "I think that there are so many variables that it is difficult to draw generalized conclusions."
Re: Is Rust faster than C?
#4struct field alignment/padding isn't part of the C spec iirc (at least not in the way mentioned in the article), but it's almost always done that way, which is important for having a stable abi
also, if performance is critical to you, profile stuff and compare outputted assembly, more often than not you'll find that llvm just outputs the same thing in both cases
Re: Is Rust faster than C?
#5[flagged]
Re: Is Rust faster than C?
#6tl;dr: Rust officially allows you to write inline assembly so it's fast, but in C it's not officially specified as part of the language. Plus more points which do not actually indicate Rust is faster than C.
... well, that's what I get for reading an article with a silly title.
Re: Is Rust faster than C?
#7Depends what you're doing with it... You can make any language you want slower than another language by using it badly
Re: Is Rust faster than C?
#8The article does not mention the possible additional optimisation opportunities that arise in Rust code due to stricter aliasing rules of references. But I don’t have an example in mind. Does anyone know of an example of it happening in real code?
Many C programs are vailid C++ and are faster when compiled with a C++ compiler because of those stricter aliasing and type rules. Like you though I have no examples.
Re: Is Rust faster than C?
#9One example where Rust enables better and faster abstractions is traits. C you can do this with some ugly methods like macros and such but in Rust it’s not the implementers choice it’s the callers choice whether to use dynamic dispatch (function pointer table in C) or static dispatch (direct function calls!)
In c the caller isn’t choosing typically. The author of some library or api decides this for you.
This turns out to be fairly significant in something like an embedded context where function pointers kill icache and rob cycles jumping through hoops. Say you want to bit bang a bus protocol using GPIO, in C with function pointers this adds maybe non trivial overhead and your abstraction is no longer (never was) free. Traits let the caller decide to monomorphize that code and get effectively register reads and writes inlined while still having an abstract interface to GPIO. This is excellent!
Re: Is Rust faster than C?
#10One example where Rust enables better and faster abstractions is traits. C you can do this with some ugly methods like macros and such but in Rust it’s not the implementers choice it’s the callers choice whether to use dynamic dispatch (function pointer table in C) or static dispatch (direct function calls!) In c the caller isn’t choosing typically. The author of some library or api decides this for you. This turns o…
> In c the callers isn’t choosing typically. The author of some library or api decides this for you.
Tbf this applies to Rust too. If the author writes
fn foo(bar: Box)
Had they written
fn foo(bar: impl BarTrait)