vendor/criterion/benches/benchmarks/compare_functions.rs

use criterion::{criterion_group, BenchmarkId, Criterion};

fn fibonacci_slow(n: u64) -> u64 {
    match n {
        0 | 1 => 1,
        n => fibonacci_slow(n - 1) + fibonacci_slow(n - 2),
    }
}

fn fibonacci_fast(n: u64) -> u64 {
    let mut a = 0;
    let mut b = 1;

    match n {
        0 => b,
        _ => {
            for _ in 0..n {
                let c = a + b;
                a = b;
                b = c;
            }
            b
        }
    }
}

fn compare_fibonaccis(c: &mut Criterion) {
    let mut group = c.benchmark_group("Fibonacci");

    group.bench_with_input("Recursive", &20, |b, i| b.iter(|| fibonacci_slow(*i)));
    group.bench_with_input("Iterative", &20, |b, i| b.iter(|| fibonacci_fast(*i)));
}
fn compare_fibonaccis_group(c: &mut Criterion) {
    let mut group = c.benchmark_group("Fibonacci3");
    for i in 20..=21 {
        group.bench_with_input(BenchmarkId::new("Recursive", i), &i, |b, i| {
            b.iter(|| fibonacci_slow(*i))
        });
        group.bench_with_input(BenchmarkId::new("Iterative", i), &i, |b, i| {
            b.iter(|| fibonacci_fast(*i))
        });
    }
    group.finish()
}

criterion_group!(fibonaccis, compare_fibonaccis, compare_fibonaccis_group,);