2 use test::{Bencher, black_box};
5 fn bench_rposition(b: &mut Bencher) {
6 let it: Vec<usize> = (0..300).collect();
8 it.iter().rposition(|&x| x <= 150);
13 fn bench_skip_while(b: &mut Bencher) {
17 it.skip_while(|&x| { sum += x; sum < 4000 }).all(|_| true);
22 fn bench_multiple_take(b: &mut Bencher) {
23 let mut it = (0..42).cycle();
25 let n = it.next().unwrap();
27 it.clone().take(it.next().unwrap()).all(|_| true);
32 fn scatter(x: i32) -> i32 { (x * 31) % 127 }
35 fn bench_max_by_key(b: &mut Bencher) {
38 it.max_by_key(|&x| scatter(x))
42 // http://www.reddit.com/r/rust/comments/31syce/using_iterators_to_find_the_index_of_the_min_or/
44 fn bench_max_by_key2(b: &mut Bencher) {
45 fn max_index_iter(array: &[i32]) -> usize {
46 array.iter().enumerate().max_by_key(|&(_, item)| item).unwrap().0
49 let mut data = vec![0; 1638];
52 b.iter(|| max_index_iter(&data));
56 fn bench_max(b: &mut Bencher) {
63 pub fn copy_zip(xs: &[u8], ys: &mut [u8]) {
64 for (a, b) in ys.iter_mut().zip(xs) {
69 pub fn add_zip(xs: &[f32], ys: &mut [f32]) {
70 for (a, b) in ys.iter_mut().zip(xs) {
76 fn bench_zip_copy(b: &mut Bencher) {
77 let source = vec![0u8; 16 * 1024];
78 let mut dst = black_box(vec![0u8; 16 * 1024]);
80 copy_zip(&source, &mut dst)
85 fn bench_zip_add(b: &mut Bencher) {
86 let source = vec![1.; 16 * 1024];
87 let mut dst = vec![0.; 16 * 1024];
89 add_zip(&source, &mut dst)
93 /// `Iterator::for_each` implemented as a plain loop.
94 fn for_each_loop<I, F>(iter: I, mut f: F) where
95 I: Iterator, F: FnMut(I::Item)
102 /// `Iterator::for_each` implemented with `fold` for internal iteration.
103 /// (except when `by_ref()` effectively disables that optimization.)
104 fn for_each_fold<I, F>(iter: I, mut f: F) where
105 I: Iterator, F: FnMut(I::Item)
107 iter.fold((), move |(), item| f(item));
111 fn bench_for_each_chain_loop(b: &mut Bencher) {
114 let iter = (0i64..1000000).chain(0..1000000).map(black_box);
115 for_each_loop(iter, |x| acc += x);
121 fn bench_for_each_chain_fold(b: &mut Bencher) {
124 let iter = (0i64..1000000).chain(0..1000000).map(black_box);
125 for_each_fold(iter, |x| acc += x);
131 fn bench_for_each_chain_ref_fold(b: &mut Bencher) {
134 let mut iter = (0i64..1000000).chain(0..1000000).map(black_box);
135 for_each_fold(iter.by_ref(), |x| acc += x);
141 /// Helper to benchmark `sum` for iterators taken by value which
142 /// can optimize `fold`, and by reference which cannot.
143 macro_rules! bench_sums {
144 ($bench_sum:ident, $bench_ref_sum:ident, $iter:expr) => {
146 fn $bench_sum(b: &mut Bencher) {
148 $iter.map(black_box).sum()
153 fn $bench_ref_sum(b: &mut Bencher) {
155 $iter.map(black_box).by_ref().sum()
163 bench_flat_map_ref_sum,
164 (0i64..1000).flat_map(|x| x..x+1000)
168 bench_flat_map_chain_sum,
169 bench_flat_map_chain_ref_sum,
170 (0i64..1000000).flat_map(|x| once(x).chain(once(x)))
175 bench_enumerate_ref_sum,
176 (0i64..1000000).enumerate().map(|(i, x)| x * i as i64)
180 bench_enumerate_chain_sum,
181 bench_enumerate_chain_ref_sum,
182 (0i64..1000000).chain(0..1000000).enumerate().map(|(i, x)| x * i as i64)
187 bench_filter_ref_sum,
188 (0i64..1000000).filter(|x| x % 2 == 0)
192 bench_filter_chain_sum,
193 bench_filter_chain_ref_sum,
194 (0i64..1000000).chain(0..1000000).filter(|x| x % 2 == 0)
198 bench_filter_map_sum,
199 bench_filter_map_ref_sum,
200 (0i64..1000000).filter_map(|x| x.checked_mul(x))
204 bench_filter_map_chain_sum,
205 bench_filter_map_chain_ref_sum,
206 (0i64..1000000).chain(0..1000000).filter_map(|x| x.checked_mul(x))
212 (0i64..1000000).fuse()
216 bench_fuse_chain_sum,
217 bench_fuse_chain_ref_sum,
218 (0i64..1000000).chain(0..1000000).fuse()
223 bench_inspect_ref_sum,
224 (0i64..1000000).inspect(|_| {})
228 bench_inspect_chain_sum,
229 bench_inspect_chain_ref_sum,
230 (0i64..1000000).chain(0..1000000).inspect(|_| {})
235 bench_peekable_ref_sum,
236 (0i64..1000000).peekable()
240 bench_peekable_chain_sum,
241 bench_peekable_chain_ref_sum,
242 (0i64..1000000).chain(0..1000000).peekable()
248 (0i64..1000000).skip(1000)
252 bench_skip_chain_sum,
253 bench_skip_chain_ref_sum,
254 (0i64..1000000).chain(0..1000000).skip(1000)
258 bench_skip_while_sum,
259 bench_skip_while_ref_sum,
260 (0i64..1000000).skip_while(|&x| x < 1000)
264 bench_skip_while_chain_sum,
265 bench_skip_while_chain_ref_sum,
266 (0i64..1000000).chain(0..1000000).skip_while(|&x| x < 1000)
270 bench_take_while_chain_sum,
271 bench_take_while_chain_ref_sum,
272 (0i64..1000000).chain(1000000..).take_while(|&x| x < 1111111)
276 bench_cycle_take_sum,
277 bench_cycle_take_ref_sum,
278 (0i64..10000).cycle().take(1000000)
281 // Checks whether Skip<Zip<A,B>> is as fast as Zip<Skip<A>, Skip<B>>, from
282 // https://users.rust-lang.org/t/performance-difference-between-iterator-zip-and-skip-order/15743
284 fn bench_zip_then_skip(b: &mut Bencher) {
285 let v: Vec<_> = (0..100_000).collect();
286 let t: Vec<_> = (0..100_000).collect();
289 let s = v.iter().zip(t.iter()).skip(10000)
290 .take_while(|t| *t.0 < 10100)
291 .map(|(a, b)| *a + *b)
293 assert_eq!(s, 2009900);
297 fn bench_skip_then_zip(b: &mut Bencher) {
298 let v: Vec<_> = (0..100_000).collect();
299 let t: Vec<_> = (0..100_000).collect();
302 let s = v.iter().skip(10000).zip(t.iter().skip(10000))
303 .take_while(|t| *t.0 < 10100)
304 .map(|(a, b)| *a + *b)
306 assert_eq!(s, 2009900);