How to use criterion crate in Rust benchmarking

Add criterion as a dev-dependency with the cargo_bench_support feature, create a benchmark file in benches/ with harness = false, and run it with cargo bench.

# Cargo.toml
[dev-dependencies]
criterion = { version = "0.8.2", features = ["cargo_bench_support"] }

[[bench]]
name = "my_bench"
harness = false

// benches/my_bench.rs
use criterion::{criterion_group, criterion_main, Criterion};

fn my_function() {
    // Code to benchmark
}

fn bench_my_function(c: &mut Criterion) {
    c.bench_function("my_function", |b| b.iter(my_function));
}

criterion_group!(benches, bench_my_function);
criterion_main!(benches);

cargo bench

Criterion is a tool that measures how fast your Rust code runs by executing it many times and calculating the average speed. You use it to find slow parts of your program before you release it to users. Think of it like a stopwatch that runs your code thousands of times to give you a very accurate time.