Benchmarking your code

The Rust project has developed a testing crate for the compiler itself. Because it includes some quite useful features, most importantly a benchmarker, it is accessible on nightly builds as the built-in test crate. Because it gets shipped with every nightly build, you don't need to add it to your Cargo.toml to use it.

The test crate is marked unstable because of its tight coupling to the compiler.

How to do it...

1. Open the Cargo.toml file that has been generated earlier for you.

2. In the bin folder, create a file called benchmarking.rs.

3. Add the following code, and run it with cargo bench:

1   #![feature(test)]
2   // The test crate was primarily designed for
3   // the Rust compiler itself, so it has no stability guaranteed
4   extern crate test;
5   
6   pub fn slow_fibonacci_recursive(n: u32) -> u32 {
7     match n {
8       0 => 0,
9       1 => 1,
10      _ => slow_fibonacci_recursive(n - 1) +  
        slow_fibonacci_recursive(n - 2),
11    }
12  }
13  
14 ...