criterion 0.3.1

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

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 fib_slow = Fun::new("Recursive", |b, i| b.iter(|| fibonacci_slow(*i)));
    let fib_fast = Fun::new("Iterative", |b, i| b.iter(|| fibonacci_fast(*i)));

    let functions = vec![fib_slow, fib_fast];

    c.bench_functions("Fibonacci", functions, 20);
}
fn compare_fibonaccis_builder(c: &mut Criterion) {
    c.bench(
        "Fibonacci2",
        ParameterizedBenchmark::new(
            "Recursive",
            |b, i| b.iter(|| fibonacci_slow(*i)),
            vec![20u64, 21u64],
        )
        .with_function("Iterative", |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()
}

fn compare_looped(c: &mut Criterion) {
    use criterion::black_box;

    c.bench(
        "small",
        ParameterizedBenchmark::new("unlooped", |b, i| b.iter(|| i + 10), vec![10]).with_function(
            "looped",
            |b, i| {
                b.iter(|| {
                    for _ in 0..10_000 {
                        black_box(i + 10);
                    }
                })
            },
        ),
    );
}

criterion_group!(
    fibonaccis,
    compare_fibonaccis,
    compare_fibonaccis_builder,
    compare_fibonaccis_group,
    compare_looped
);