Compiler Explorer

Source code

#![feature(test)]
//#![feature(bench_black_box)]

fn selection_sort(original_vec: &mut Vec<i32>) -> Vec<i32> {
    for i in 0..original_vec.len()-1 {
        let mut smallest: usize = i;
        for j in i+1..original_vec.len() {
            if original_vec[j] < original_vec[smallest] {
                smallest = j;
            }
        }
        if smallest != i {
            original_vec.swap(i, smallest);
        }
    };
    original_vec.to_vec()
}

// helper function for testing (uses builtin sort function)
fn rust_sort<A, T>(mut array: A) -> A
where
    A: AsMut<[T]>,
    T: Ord,
{
    let slice = array.as_mut();
    slice.sort_unstable();

array
}

const TEST_VECS: [[i32; 10]; 6] = [
    [1, 3, 2, 9, 6, 7, 4, 10, 8, 5],
    [1, 2, 7, 2, 9, 9, 7, 10, 2, 1],
    [0, 4, 1, 3, 9, 12, 3, 0, 13, 8],
    [1, 2, 3, 4, 5, 6, 7, 8, 9, 10],
    [-1, -5, -10, 1, 10, 2, -123, -34, 0, -32],
    [i32::MAX, -32984, i32::MIN, 31648, 5349857, -30954, -2343285, 0, 1, i32::MIN],
];

#[bench]
pub
fn bench_rust_sort(b: &mut Bencher) {
    b.iter(|| {
        for i in TEST_VECS {
            (&mut i.to_vec()).sort()
        }
    })
}

#[bench]
pub
fn bench_selection_sort(b: &mut Bencher) {
    b.iter(|| {
        for i in TEST_VECS {
            selection_sort(&mut i.to_vec());
        }
    })
}

// I don't know how to get it to show asm for the #[bench] version
pub
fn xbench_selection_sort(a: i32) {
    let mut b = a;
    while b!=0 {  // just a counted repeat loop
    // looks like selection_sort did *not* optimze away,
    // and there's just some movups copying of 40 bytes before each sort.  No alloc / dealloc
        for i in TEST_VECS {
            rust_sort(&mut i.to_vec());
        }
        b -= 1;
    }
}