Optionでくるむと重くなる？？ #rustlang

test_option_btreeset.rs

use std::collections::BTreeSet;

fn func1(s: Option<BTreeSet<usize>>) -> BTreeSet<usize> {
    let mut s = s.unwrap_or((0..100).collect());

    s.pop_first();

    s
}

fn func2(mut s: BTreeSet<usize>) -> BTreeSet<usize> {
    s.pop_first();

    s
}

fn main() {
    let mut args = std::env::args();
    args.next();
    let f: usize = args.next().unwrap().parse().unwrap();
    let n: usize = args.next().unwrap().parse().unwrap();

    let mut s: BTreeSet<usize> = (0..n).collect();
    
    while !s.is_empty() {
        match f {
            1 => {
                s = func1(Some(s));
            },
            2 => {
                s = func2(s);
            },
            _ => {
                panic!();
            },
        }
    }
}

$ time cargo run -r 1 10000000
    Finished release [optimized] target(s) in 0.01s
     Running `target\release\test_btreeset.exe 1 10000000`

real    0m17.238s
user    0m0.000s
sys     0m0.000s

$ time cargo run -r 2 10000000
    Finished release [optimized] target(s) in 0.01s
     Running `target\release\test_btreeset.exe 2 10000000`

real    0m1.556s
user    0m0.000s
sys     0m0.000s