rust/library/alloc/benches/vec_deque.rs
surechen 40ae34194c remove redundant imports
detects redundant imports that can be eliminated.

for #117772 :

In order to facilitate review and modification, split the checking code and
removing redundant imports code into two PR.
2023-12-10 10:56:22 +08:00

269 lines
6.4 KiB
Rust

use std::{
collections::{vec_deque, VecDeque},
mem,
};
use test::{black_box, Bencher};
#[bench]
fn bench_new(b: &mut Bencher) {
b.iter(|| {
let ring: VecDeque<i32> = VecDeque::new();
black_box(ring);
})
}
#[bench]
fn bench_grow_1025(b: &mut Bencher) {
b.iter(|| {
let mut deq = VecDeque::new();
for i in 0..1025 {
deq.push_front(i);
}
black_box(deq);
})
}
#[bench]
fn bench_iter_1000(b: &mut Bencher) {
let ring: VecDeque<_> = (0..1000).collect();
b.iter(|| {
let mut sum = 0;
for &i in &ring {
sum += i;
}
black_box(sum);
})
}
#[bench]
fn bench_mut_iter_1000(b: &mut Bencher) {
let mut ring: VecDeque<_> = (0..1000).collect();
b.iter(|| {
let mut sum = 0;
for i in &mut ring {
sum += *i;
}
black_box(sum);
})
}
#[bench]
fn bench_try_fold(b: &mut Bencher) {
let ring: VecDeque<_> = (0..1000).collect();
b.iter(|| black_box(ring.iter().try_fold(0, |a, b| Some(a + b))))
}
/// does the memory bookkeeping to reuse the buffer of the Vec between iterations.
/// `setup` must not modify its argument's length or capacity. `g` must not move out of its argument.
fn into_iter_helper<
T: Copy,
F: FnOnce(&mut VecDeque<T>),
G: FnOnce(&mut vec_deque::IntoIter<T>),
>(
v: &mut Vec<T>,
setup: F,
g: G,
) {
let ptr = v.as_mut_ptr();
let len = v.len();
// ensure that the vec is full, to make sure that any wrapping from the deque doesn't
// access uninitialized memory.
assert_eq!(v.len(), v.capacity());
let mut deque = VecDeque::from(mem::take(v));
setup(&mut deque);
let mut it = deque.into_iter();
g(&mut it);
mem::forget(it);
// SAFETY: the provided functions are not allowed to modify the allocation, so the buffer is still alive.
// len and capacity are accurate due to the above assertion.
// All the elements in the buffer are still valid, because of `T: Copy` which implies `T: !Drop`.
mem::forget(mem::replace(v, unsafe { Vec::from_raw_parts(ptr, len, len) }));
}
#[bench]
fn bench_into_iter(b: &mut Bencher) {
let len = 1024;
// we reuse this allocation for every run
let mut vec: Vec<usize> = (0..len).collect();
vec.shrink_to_fit();
b.iter(|| {
let mut sum = 0;
into_iter_helper(
&mut vec,
|_| {},
|it| {
for i in it {
sum += i;
}
},
);
black_box(sum);
let mut sum = 0;
// rotating a full deque doesn't move any memory.
into_iter_helper(
&mut vec,
|d| d.rotate_left(len / 2),
|it| {
for i in it {
sum += i;
}
},
);
black_box(sum);
});
}
#[bench]
fn bench_into_iter_fold(b: &mut Bencher) {
let len = 1024;
// because `fold` takes ownership of the iterator,
// we can't prevent it from dropping the memory,
// so we have to bite the bullet and reallocate
// for every iteration.
b.iter(|| {
let deque: VecDeque<usize> = (0..len).collect();
assert_eq!(deque.len(), deque.capacity());
let sum = deque.into_iter().fold(0, |a, b| a + b);
black_box(sum);
// rotating a full deque doesn't move any memory.
let mut deque: VecDeque<usize> = (0..len).collect();
assert_eq!(deque.len(), deque.capacity());
deque.rotate_left(len / 2);
let sum = deque.into_iter().fold(0, |a, b| a + b);
black_box(sum);
});
}
#[bench]
fn bench_into_iter_try_fold(b: &mut Bencher) {
let len = 1024;
// we reuse this allocation for every run
let mut vec: Vec<usize> = (0..len).collect();
vec.shrink_to_fit();
// Iterator::any uses Iterator::try_fold under the hood
b.iter(|| {
let mut b = false;
into_iter_helper(&mut vec, |_| {}, |it| b = it.any(|i| i == len - 1));
black_box(b);
into_iter_helper(&mut vec, |d| d.rotate_left(len / 2), |it| b = it.any(|i| i == len - 1));
black_box(b);
});
}
#[bench]
fn bench_into_iter_next_chunk(b: &mut Bencher) {
let len = 1024;
// we reuse this allocation for every run
let mut vec: Vec<usize> = (0..len).collect();
vec.shrink_to_fit();
b.iter(|| {
let mut buf = [0; 64];
into_iter_helper(
&mut vec,
|_| {},
|it| {
while let Ok(a) = it.next_chunk() {
buf = a;
}
},
);
black_box(buf);
into_iter_helper(
&mut vec,
|d| d.rotate_left(len / 2),
|it| {
while let Ok(a) = it.next_chunk() {
buf = a;
}
},
);
black_box(buf);
});
}
#[bench]
fn bench_from_array_1000(b: &mut Bencher) {
const N: usize = 1000;
let mut array: [usize; N] = [0; N];
for i in 0..N {
array[i] = i;
}
b.iter(|| {
let deq: VecDeque<_> = array.into();
black_box(deq);
})
}
#[bench]
fn bench_extend_bytes(b: &mut Bencher) {
let mut ring: VecDeque<u8> = VecDeque::with_capacity(1000);
let input: &[u8] = &[128; 512];
b.iter(|| {
ring.clear();
ring.extend(black_box(input));
});
}
#[bench]
fn bench_extend_vec(b: &mut Bencher) {
let mut ring: VecDeque<u8> = VecDeque::with_capacity(1000);
let input = vec![128; 512];
b.iter(|| {
ring.clear();
let input = input.clone();
ring.extend(black_box(input));
});
}
#[bench]
fn bench_extend_trustedlen(b: &mut Bencher) {
let mut ring: VecDeque<u16> = VecDeque::with_capacity(1000);
b.iter(|| {
ring.clear();
ring.extend(black_box(0..512));
});
}
#[bench]
fn bench_extend_chained_trustedlen(b: &mut Bencher) {
let mut ring: VecDeque<u16> = VecDeque::with_capacity(1000);
b.iter(|| {
ring.clear();
ring.extend(black_box((0..256).chain(768..1024)));
});
}
#[bench]
fn bench_extend_chained_bytes(b: &mut Bencher) {
let mut ring: VecDeque<u16> = VecDeque::with_capacity(1000);
let input1: &[u16] = &[128; 256];
let input2: &[u16] = &[255; 256];
b.iter(|| {
ring.clear();
ring.extend(black_box(input1.iter().chain(input2.iter())));
});
}