diff --git a/library/alloc/benches/vec.rs b/library/alloc/benches/vec.rs index 6a3d7046126..df11aa9355f 100644 --- a/library/alloc/benches/vec.rs +++ b/library/alloc/benches/vec.rs @@ -471,3 +471,107 @@ bench_in_place![ bench_in_place_u128_i1_0100, u128, 100, 1; bench_in_place_u128_i1_1000, u128, 1000, 1 ]; + +#[bench] +fn bench_chain_collect(b: &mut test::Bencher) { + let data = black_box([0; LEN]); + b.iter(|| data.iter().cloned().chain([1].iter().cloned()).collect::>()); +} + +#[bench] +fn bench_chain_chain_collect(b: &mut test::Bencher) { + let data = black_box([0; LEN]); + b.iter(|| { + data.iter() + .cloned() + .chain([1].iter().cloned()) + .chain([2].iter().cloned()) + .collect::>() + }); +} + +#[bench] +fn bench_nest_chain_chain_collect(b: &mut test::Bencher) { + let data = black_box([0; LEN]); + b.iter(|| { + data.iter().cloned().chain([1].iter().chain([2].iter()).cloned()).collect::>() + }); +} + +pub fn example_plain_slow(l: &[u32]) -> Vec { + let mut result = Vec::with_capacity(l.len()); + result.extend(l.iter().rev()); + result +} + +pub fn map_fast(l: &[(u32, u32)]) -> Vec { + let mut result = Vec::with_capacity(l.len()); + for i in 0..l.len() { + unsafe { + *result.get_unchecked_mut(i) = l[i].0; + result.set_len(i); + } + } + result +} + +const LEN: usize = 16384; + +#[bench] +fn bench_range_map_collect(b: &mut test::Bencher) { + b.iter(|| (0..LEN).map(|_| u32::default()).collect::>()); +} + +#[bench] +fn bench_chain_extend_ref(b: &mut test::Bencher) { + let data = black_box([0; LEN]); + b.iter(|| { + let mut v = Vec::::with_capacity(data.len() + 1); + v.extend(data.iter().chain([1].iter())); + v + }); +} + +#[bench] +fn bench_chain_extend_value(b: &mut test::Bencher) { + let data = black_box([0; LEN]); + b.iter(|| { + let mut v = Vec::::with_capacity(data.len() + 1); + v.extend(data.iter().cloned().chain(Some(1))); + v + }); +} + +#[bench] +fn bench_rev_1(b: &mut test::Bencher) { + let data = black_box([0; LEN]); + b.iter(|| { + let mut v = Vec::::new(); + v.extend(data.iter().rev()); + v + }); +} + +#[bench] +fn bench_rev_2(b: &mut test::Bencher) { + let data = black_box([0; LEN]); + b.iter(|| { + example_plain_slow(&data); + }); +} + +#[bench] +fn bench_map_regular(b: &mut test::Bencher) { + let data = black_box([(0, 0); LEN]); + b.iter(|| { + let mut v = Vec::::new(); + v.extend(data.iter().map(|t| t.1)); + v + }); +} + +#[bench] +fn bench_map_fast(b: &mut test::Bencher) { + let data = black_box([(0, 0); LEN]); + b.iter(|| map_fast(&data)); +}