use core::borrow::Borrow; use core::iter::*; use core::mem; use core::num::Wrapping; use test::{black_box, Bencher}; #[bench] fn bench_rposition(b: &mut Bencher) { let it: Vec = (0..300).collect(); b.iter(|| { it.iter().rposition(|&x| x <= 150); }); } #[bench] fn bench_skip_while(b: &mut Bencher) { b.iter(|| { let it = 0..100; let mut sum = 0; it.skip_while(|&x| { sum += x; sum < 4000 }) .all(|_| true); }); } #[bench] fn bench_multiple_take(b: &mut Bencher) { let mut it = (0..42).cycle(); b.iter(|| { let n = it.next().unwrap(); for _ in 0..n { it.clone().take(it.next().unwrap()).all(|_| true); } }); } fn scatter(x: i32) -> i32 { (x * 31) % 127 } #[bench] fn bench_max_by_key(b: &mut Bencher) { b.iter(|| { let it = 0..100; it.map(black_box).max_by_key(|&x| scatter(x)) }) } // https://www.reddit.com/r/rust/comments/31syce/using_iterators_to_find_the_index_of_the_min_or/ #[bench] fn bench_max_by_key2(b: &mut Bencher) { fn max_index_iter(array: &[i32]) -> usize { array.iter().enumerate().max_by_key(|&(_, item)| item).unwrap().0 } let mut data = vec![0; 1638]; data[514] = 9999; b.iter(|| max_index_iter(&data)); } #[bench] fn bench_max(b: &mut Bencher) { b.iter(|| { let it = 0..100; it.map(black_box).map(scatter).max() }) } pub fn copy_zip(xs: &[u8], ys: &mut [u8]) { for (a, b) in ys.iter_mut().zip(xs) { *a = *b; } } pub fn add_zip(xs: &[f32], ys: &mut [f32]) { for (a, b) in ys.iter_mut().zip(xs) { *a += *b; } } #[bench] fn bench_zip_copy(b: &mut Bencher) { let source = vec![0u8; 16 * 1024]; let mut dst = black_box(vec![0u8; 16 * 1024]); b.iter(|| copy_zip(&source, &mut dst)) } #[bench] fn bench_zip_add(b: &mut Bencher) { let source = vec![1.; 16 * 1024]; let mut dst = vec![0.; 16 * 1024]; b.iter(|| add_zip(&source, &mut dst)); } /// `Iterator::for_each` implemented as a plain loop. fn for_each_loop(iter: I, mut f: F) where I: Iterator, F: FnMut(I::Item), { for item in iter { f(item); } } /// `Iterator::for_each` implemented with `fold` for internal iteration. /// (except when `by_ref()` effectively disables that optimization.) fn for_each_fold(iter: I, mut f: F) where I: Iterator, F: FnMut(I::Item), { iter.fold((), move |(), item| f(item)); } #[bench] fn bench_for_each_chain_loop(b: &mut Bencher) { b.iter(|| { let mut acc = 0; let iter = (0i64..1000000).chain(0..1000000).map(black_box); for_each_loop(iter, |x| acc += x); acc }); } #[bench] fn bench_for_each_chain_fold(b: &mut Bencher) { b.iter(|| { let mut acc = 0; let iter = (0i64..1000000).chain(0..1000000).map(black_box); for_each_fold(iter, |x| acc += x); acc }); } #[bench] fn bench_for_each_chain_ref_fold(b: &mut Bencher) { b.iter(|| { let mut acc = 0; let mut iter = (0i64..1000000).chain(0..1000000).map(black_box); for_each_fold(iter.by_ref(), |x| acc += x); acc }); } /// Helper to benchmark `sum` for iterators taken by value which /// can optimize `fold`, and by reference which cannot. macro_rules! bench_sums { ($bench_sum:ident, $bench_ref_sum:ident, $iter:expr) => { #[bench] fn $bench_sum(b: &mut Bencher) { b.iter(|| -> i64 { $iter.map(black_box).sum() }); } #[bench] fn $bench_ref_sum(b: &mut Bencher) { b.iter(|| -> i64 { $iter.map(black_box).by_ref().sum() }); } }; } bench_sums! { bench_flat_map_sum, bench_flat_map_ref_sum, (0i64..1000).flat_map(|x| x..x+1000) } bench_sums! { bench_flat_map_chain_sum, bench_flat_map_chain_ref_sum, (0i64..1000000).flat_map(|x| once(x).chain(once(x))) } bench_sums! { bench_enumerate_sum, bench_enumerate_ref_sum, (0i64..1000000).enumerate().map(|(i, x)| x * i as i64) } bench_sums! { bench_enumerate_chain_sum, bench_enumerate_chain_ref_sum, (0i64..1000000).chain(0..1000000).enumerate().map(|(i, x)| x * i as i64) } bench_sums! { bench_filter_sum, bench_filter_ref_sum, (0i64..1000000).filter(|x| x % 3 == 0) } bench_sums! { bench_filter_chain_sum, bench_filter_chain_ref_sum, (0i64..1000000).chain(0..1000000).filter(|x| x % 3 == 0) } bench_sums! { bench_filter_map_sum, bench_filter_map_ref_sum, (0i64..1000000).filter_map(|x| x.checked_mul(x)) } bench_sums! { bench_filter_map_chain_sum, bench_filter_map_chain_ref_sum, (0i64..1000000).chain(0..1000000).filter_map(|x| x.checked_mul(x)) } bench_sums! { bench_fuse_sum, bench_fuse_ref_sum, (0i64..1000000).fuse() } bench_sums! { bench_fuse_chain_sum, bench_fuse_chain_ref_sum, (0i64..1000000).chain(0..1000000).fuse() } bench_sums! { bench_inspect_sum, bench_inspect_ref_sum, (0i64..1000000).inspect(|_| {}) } bench_sums! { bench_inspect_chain_sum, bench_inspect_chain_ref_sum, (0i64..1000000).chain(0..1000000).inspect(|_| {}) } bench_sums! { bench_peekable_sum, bench_peekable_ref_sum, (0i64..1000000).peekable() } bench_sums! { bench_peekable_chain_sum, bench_peekable_chain_ref_sum, (0i64..1000000).chain(0..1000000).peekable() } bench_sums! { bench_skip_sum, bench_skip_ref_sum, (0i64..1000000).skip(1000) } bench_sums! { bench_skip_chain_sum, bench_skip_chain_ref_sum, (0i64..1000000).chain(0..1000000).skip(1000) } bench_sums! { bench_skip_while_sum, bench_skip_while_ref_sum, (0i64..1000000).skip_while(|&x| x < 1000) } bench_sums! { bench_skip_while_chain_sum, bench_skip_while_chain_ref_sum, (0i64..1000000).chain(0..1000000).skip_while(|&x| x < 1000) } bench_sums! { bench_take_while_chain_sum, bench_take_while_chain_ref_sum, (0i64..1000000).chain(1000000..).take_while(|&x| x < 1111111) } bench_sums! { bench_cycle_take_sum, bench_cycle_take_ref_sum, (0..10000).cycle().take(1000000) } bench_sums! { bench_cycle_skip_take_sum, bench_cycle_skip_take_ref_sum, (0..100000).cycle().skip(1000000).take(1000000) } bench_sums! { bench_cycle_take_skip_sum, bench_cycle_take_skip_ref_sum, (0..100000).cycle().take(1000000).skip(100000) } bench_sums! { bench_skip_cycle_skip_zip_add_sum, bench_skip_cycle_skip_zip_add_ref_sum, (0..100000).skip(100).cycle().skip(100) .zip((0..100000).cycle().skip(10)) .map(|(a,b)| a+b) .skip(100000) .take(1000000) } // Checks whether Skip> is as fast as Zip, Skip>, from // https://users.rust-lang.org/t/performance-difference-between-iterator-zip-and-skip-order/15743 #[bench] fn bench_zip_then_skip(b: &mut Bencher) { let v: Vec<_> = (0..100_000).collect(); let t: Vec<_> = (0..100_000).collect(); b.iter(|| { let s = v .iter() .zip(t.iter()) .skip(10000) .take_while(|t| *t.0 < 10100) .map(|(a, b)| *a + *b) .sum::(); assert_eq!(s, 2009900); }); } #[bench] fn bench_skip_then_zip(b: &mut Bencher) { let v: Vec<_> = (0..100_000).collect(); let t: Vec<_> = (0..100_000).collect(); b.iter(|| { let s = v .iter() .skip(10000) .zip(t.iter().skip(10000)) .take_while(|t| *t.0 < 10100) .map(|(a, b)| *a + *b) .sum::(); assert_eq!(s, 2009900); }); } #[bench] fn bench_filter_count(b: &mut Bencher) { b.iter(|| (0i64..1000000).map(black_box).filter(|x| x % 3 == 0).count()) } #[bench] fn bench_filter_ref_count(b: &mut Bencher) { b.iter(|| (0i64..1000000).map(black_box).by_ref().filter(|x| x % 3 == 0).count()) } #[bench] fn bench_filter_chain_count(b: &mut Bencher) { b.iter(|| (0i64..1000000).chain(0..1000000).map(black_box).filter(|x| x % 3 == 0).count()) } #[bench] fn bench_filter_chain_ref_count(b: &mut Bencher) { b.iter(|| { (0i64..1000000).chain(0..1000000).map(black_box).by_ref().filter(|x| x % 3 == 0).count() }) } #[bench] fn bench_partial_cmp(b: &mut Bencher) { b.iter(|| (0..100000).map(black_box).partial_cmp((0..100000).map(black_box))) } #[bench] fn bench_chain_partial_cmp(b: &mut Bencher) { b.iter(|| { (0..50000).chain(50000..100000).map(black_box).partial_cmp((0..100000).map(black_box)) }) } #[bench] fn bench_lt(b: &mut Bencher) { b.iter(|| (0..100000).map(black_box).lt((0..100000).map(black_box))) } #[bench] fn bench_trusted_random_access_adapters(b: &mut Bencher) { let vec1: Vec<_> = (0usize..100000).collect(); let vec2 = black_box(vec1.clone()); b.iter(|| { let mut iter = vec1 .iter() .copied() .enumerate() .map(|(idx, e)| idx.wrapping_add(e)) .zip(vec2.iter().copied()) .map(|(a, b)| a.wrapping_add(b)) .fuse(); let mut acc: usize = 0; let size = iter.size(); for i in 0..size { // SAFETY: TRA requirements are satisfied by 0..size iteration and then dropping the // iterator. acc = acc.wrapping_add(unsafe { iter.__iterator_get_unchecked(i) }); } acc }) } /// Exercises the iter::Copied specialization for slice::Iter #[bench] fn bench_copied_chunks(b: &mut Bencher) { let v = vec![1u8; 1024]; b.iter(|| { let mut iter = black_box(&v).iter().copied(); let mut acc = Wrapping(0); // This uses a while-let loop to side-step the TRA specialization in ArrayChunks while let Ok(chunk) = iter.next_chunk::<{ mem::size_of::() }>() { let d = u64::from_ne_bytes(chunk); acc += Wrapping(d.rotate_left(7).wrapping_add(1)); } acc }) } /// Exercises the TrustedRandomAccess specialization in ArrayChunks #[bench] fn bench_trusted_random_access_chunks(b: &mut Bencher) { let v = vec![1u8; 1024]; b.iter(|| { black_box(&v) .iter() // this shows that we're not relying on the slice::Iter specialization in Copied .map(|b| *b.borrow()) .array_chunks::<{ mem::size_of::() }>() .map(|ary| { let d = u64::from_ne_bytes(ary); Wrapping(d.rotate_left(7).wrapping_add(1)) }) .sum::>() }) }