Benchmarking programs in Rust

How is it possible to benchmark programs in Rust? For example, how would I get execution time of program in seconds?

Solution 1:

It might be worth noting two years later (to help any future Rust programmers who stumble on this page) that there are now tools to benchmark Rust code as a part of one's test suite.

(From the guide link below) Using the #[bench] attribute, one can use the standard Rust tooling to benchmark methods in their code.

extern crate test;
use test::Bencher;

#[bench]
fn bench_xor_1000_ints(b: &mut Bencher) {
    b.iter(|| {
        // Use `test::black_box` to prevent compiler optimizations from disregarding
        // Unused values
        test::black_box(range(0u, 1000).fold(0, |old, new| old ^ new));
    });
}

For the command cargo bench this outputs something like:

running 1 test
test bench_xor_1000_ints ... bench:       375 ns/iter (+/- 148)

test result: ok. 0 passed; 0 failed; 0 ignored; 1 measured

Links:

• The Rust Book (section on benchmark tests)
• "The Nightly Book" (section on the test crate)
• test::Bencher docs

Solution 2:

For measuring time without adding third-party dependencies, you can use std::time::Instant:

fn main() {
    use std::time::Instant;
    let now = Instant::now();

    // Code block to measure.
    {
        my_function_to_measure();
    }

    let elapsed = now.elapsed();
    println!("Elapsed: {:.2?}", elapsed);
}