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Comment by kibwen | Hacker News Reader

I'm curious if the results at the very end for the copy-pasted code benchmarks are a result of linking. They seem to have chosen to use mold for C++ and not for Rust after seeing that it gave little benefit for small projects, but I would expect that to change as the project scales.

In addition, I'd be interested in seeing how `cargo check` fares. In practice I do `cargo build` quite rarely, in favor of `cargo check` and `cargo test`.

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I think https://github.com/quick-lint/cpp-vs-rust/blob/f8d31341f5cac... indicates Rust is using Mold too. And I get the impression that the thing unit being benchmarked is a single crate—that is, one crate 8×, 16×, 24× the size (which puts the burden on the compiler, in areas that don’t parallelise well), rather than 8×, 16×, 24× as many crates (which puts the weight on the linker and on well-parallelised parts of the compiler).

On the hardware in question, which has loads of cores, I’m very confident that Rust would fare considerably better with 24 17.1k-line crates (410k lines, larger due to duplicating the entire thing rather than just the lexer) than with the one 104.4k-line crate apparently tested.

> I’m very confident that Rust would fare considerably better with 24 17.1k-line crates (410k lines, larger due to duplicating the entire thing rather than just the lexer) than with the one 104.4k-line crate apparently tested.

I didn't consider this in my scaling benchmark. You make a good point.

Yea, comparing C++ build times and Rust build times seems to ignore the practical workflow differences between writing the two.

Also, I think it's a little silly to say that Rust build times scale poorly (even if it isn't quite as good as C++). 100k LOC in, what, 6s at the end there is not so shabby if you're typically never building all of it.

> They seem to have chosen to use mold for C++ and not for Rust after seeing that it gave little benefit for small projects, but I would expect that to change as the project scales.

The benchmarks show Mold for both Rust and C++. This wasn't explicitly stated in the article; sorry. https://github.com/quick-lint/cpp-vs-rust/blob/f8d31341f5cac...

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