How to benchmark a function from my crate

[lucidBrot]

I got the fibonacci example to work with the function within my_benchmark.rs. But I cannot figure out how I can benchmark a function that I defined in my own crate.

My folder structure is like this:

mycratename
| - benches
    | - my_benchmark.rs
| - src
    | - main.rs
| - target
| - Cargo.toml
| - Cargo.lock

How could I benchmark a function that is defined in main.rs?
Or is that already documented somewhere? In that case, I think a more obvious link is needed

[bheisler]

Hey, thanks for trying Criterion.rs!

Unfortunately, it's not currently possible to use Criterion.rs with binary crates, only with library crates (see this issue for more details). If you have a library crate, you can take a look at the Getting Started page of the user guide, which shows an example of benchmarking a function from the lib.rs file.

Edit: I almost forgot; this is documented in the Known Limitations section of the user guide.

Edit2: It's fairly common for binary crates in Rust to contain only a thin layer of glue code (parsing command-line arguments, etc.) around a library crate that implements the application logic. I don't actually remember just off-hand why that's done, but it does handily solve this problem.

[lucidBrot]

Thanks for that reply! I'll have to read up on the difference between creating a lib vs binary crate (I'm kinda new to rust), but it does sound like I should be able do do what your Edit2 suggests

[lucidBrot]

Okay. Turns out I would have needed to use a library instead of a binary crate anyways, because I want to use my crate in a different crate and it is not possible to use binary crates in other crates. So thank you for the suggestion!

I don't see the point of binary crates then... because libraries can have executables with cargo run --example.

For anybody else with the same problem though: All it takes is renaming main.rs to lib.rs