ordered_map.rs

use std::iter;
use std::collections::BTreeMap;
use bencher::{ benchmark_group, benchmark_main, Bencher };
use rand::prelude::*;
use rand_pcg::Pcg64;
use heapless::FnvIndexMap;

fn get_keys_values(n: usize) -> Vec<(&'static str, u8)> {
    let mut rng = Pcg64::seed_from_u64(2);
    let values = iter::from_fn(|| rng.gen::<u8>().into());
    let keys = [
            "ab", "ac", "ad", "ae", "af", "ag", "ah", "ai",
            "XB", "XC", "XD", "XE", "XF", "XG", "XH", "XI",
        ]
        .iter()
        .copied()
        .cycle();

    keys.zip(values).take(n).collect()
}

fn index_map(b: &mut Bencher) {
    let kvs = get_keys_values(5_000);
    let mut map = FnvIndexMap::<&str, u8, 32>::new();

    b.iter(move || {
        for &(key, value) in &kvs {
            map.insert(key, value).unwrap();
        }
    });
}

fn btree_map(b: &mut Bencher) {
    let kvs = get_keys_values(5_000);
    let mut map = BTreeMap::<&str, u8>::new();

    b.iter(move || {
        for &(key, value) in &kvs {
            map.insert(key, value);
        }
    });
}

benchmark_group!(benches, index_map, btree_map);
benchmark_main!(benches);