bench-times

     Running target/release/scratch-75cde277a7678a8e

running 2 tests
test bench_vec_from_elem ... bench:      1218 ns/iter (+/- 19)
test bench_vec_iter      ... bench:      5439 ns/iter (+/- 13)

test result: ok. 0 passed; 0 failed; 0 ignored; 2 measured

scratch2.rs

#![feature(test)]

extern crate test;

use std::iter::repeat;

const SIZE: usize = 10_000;

#[bench]
fn bench_vec_iter(b: &mut test::Bencher) {
    b.iter(|| {
        repeat(0).take(SIZE).collect::<Vec<_>>();
    });
}

#[bench]
fn bench_vec_from_elem(b: &mut test::Bencher) {
    b.iter(|| {
        let mut xs = Vec::with_capacity(SIZE);
        unsafe { xs.set_len(SIZE); }
        for x in xs.iter_mut() { *x = 0; }
    });
}

#[cfg(not(test))]
fn main() {}