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Try to make Vec benchmarks only run code they are benchmarking
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Many of the Vec benchmarks assert what values should be produced by the
benchmarked code. In some cases, these asserts dominate the runtime of
the benchmarks they are in, causing the benchmarks to understate the
impact of an optimization or regression.
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@saethlin
saethlin committed Mar 25, 2021
1 parent 07e0e2e commit 8c88418
Showing 1 changed file with 25 additions and 68 deletions.
93 changes: 25 additions & 68 deletions library/alloc/benches/vec.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -4,23 +4,13 @@ use test::{black_box, Bencher};

#[bench]
fn bench_new(b: &mut Bencher) {
b.iter(|| {
let v: Vec<u32> = Vec::new();
assert_eq!(v.len(), 0);
assert_eq!(v.capacity(), 0);
v
})
b.iter(|| Vec::<u32>::new())
}

fn do_bench_with_capacity(b: &mut Bencher, src_len: usize) {
b.bytes = src_len as u64;

b.iter(|| {
let v: Vec<u32> = Vec::with_capacity(src_len);
assert_eq!(v.len(), 0);
assert_eq!(v.capacity(), src_len);
v
})
b.iter(|| Vec::<u32>::with_capacity(src_len))
}

#[bench]
Expand All @@ -46,12 +36,7 @@ fn bench_with_capacity_1000(b: &mut Bencher) {
fn do_bench_from_fn(b: &mut Bencher, src_len: usize) {
b.bytes = src_len as u64;

b.iter(|| {
let dst = (0..src_len).collect::<Vec<_>>();
assert_eq!(dst.len(), src_len);
assert!(dst.iter().enumerate().all(|(i, x)| i == *x));
dst
})
b.iter(|| (0..src_len).collect::<Vec<_>>())
}

#[bench]
Expand All @@ -77,12 +62,7 @@ fn bench_from_fn_1000(b: &mut Bencher) {
fn do_bench_from_elem(b: &mut Bencher, src_len: usize) {
b.bytes = src_len as u64;

b.iter(|| {
let dst: Vec<usize> = repeat(5).take(src_len).collect();
assert_eq!(dst.len(), src_len);
assert!(dst.iter().all(|x| *x == 5));
dst
})
b.iter(|| repeat(5).take(src_len).collect::<Vec<usize>>())
}

#[bench]
Expand Down Expand Up @@ -110,12 +90,7 @@ fn do_bench_from_slice(b: &mut Bencher, src_len: usize) {

b.bytes = src_len as u64;

b.iter(|| {
let dst = src.clone()[..].to_vec();
assert_eq!(dst.len(), src_len);
assert!(dst.iter().enumerate().all(|(i, x)| i == *x));
dst
});
b.iter(|| src.as_slice().to_vec());
}

#[bench]
Expand Down Expand Up @@ -144,9 +119,7 @@ fn do_bench_from_iter(b: &mut Bencher, src_len: usize) {
b.bytes = src_len as u64;

b.iter(|| {
let dst: Vec<_> = FromIterator::from_iter(src.clone());
assert_eq!(dst.len(), src_len);
assert!(dst.iter().enumerate().all(|(i, x)| i == *x));
let dst: Vec<_> = FromIterator::from_iter(src.iter().cloned());
dst
});
}
Expand Down Expand Up @@ -180,8 +153,6 @@ fn do_bench_extend(b: &mut Bencher, dst_len: usize, src_len: usize) {
b.iter(|| {
let mut dst = dst.clone();
dst.extend(src.clone());
assert_eq!(dst.len(), dst_len + src_len);
assert!(dst.iter().enumerate().all(|(i, x)| i == *x));
dst
});
}
Expand Down Expand Up @@ -230,8 +201,6 @@ fn do_bench_extend_from_slice(b: &mut Bencher, dst_len: usize, src_len: usize) {
b.iter(|| {
let mut dst = dst.clone();
dst.extend_from_slice(&src);
assert_eq!(dst.len(), dst_len + src_len);
assert!(dst.iter().enumerate().all(|(i, x)| i == *x));
dst
});
}
Expand Down Expand Up @@ -290,12 +259,7 @@ fn do_bench_clone(b: &mut Bencher, src_len: usize) {

b.bytes = src_len as u64;

b.iter(|| {
let dst = src.clone();
assert_eq!(dst.len(), src_len);
assert!(dst.iter().enumerate().all(|(i, x)| i == *x));
dst
});
b.iter(|| src.clone());
}

#[bench]
Expand Down Expand Up @@ -329,8 +293,7 @@ fn do_bench_clone_from(b: &mut Bencher, times: usize, dst_len: usize, src_len: u

for _ in 0..times {
dst.clone_from(&src);
assert_eq!(dst.len(), src_len);
assert!(dst.iter().enumerate().all(|(i, x)| dst_len + i == *x));
dst = black_box(dst);
}
dst
});
Expand Down Expand Up @@ -463,11 +426,10 @@ macro_rules! bench_in_place {
fn $fname(b: &mut Bencher) {
b.iter(|| {
let src: Vec<$type> = black_box(vec![$init; $count]);
let mut sink = src.into_iter()
src.into_iter()
.enumerate()
.map(|(idx, e)| idx as $type ^ e)
.collect::<Vec<$type>>();
black_box(sink.as_mut_ptr())
.collect::<Vec<$type>>()
});
}
)+
Expand Down Expand Up @@ -527,7 +489,6 @@ fn bench_in_place_zip_recycle(b: &mut Bencher) {
.enumerate()
.map(|(i, (d, s))| d.wrapping_add(i as u8) ^ s)
.collect::<Vec<_>>();
assert_eq!(mangled.len(), 1000);
data = black_box(mangled);
});
}
Expand Down Expand Up @@ -614,23 +575,6 @@ fn bench_nest_chain_chain_collect(b: &mut Bencher) {
});
}

pub fn example_plain_slow(l: &[u32]) -> Vec<u32> {
let mut result = Vec::with_capacity(l.len());
result.extend(l.iter().rev());
result
}

pub fn map_fast(l: &[(u32, u32)]) -> Vec<u32> {
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
}

#[bench]
fn bench_range_map_collect(b: &mut Bencher) {
b.iter(|| (0..LEN).map(|_| u32::default()).collect::<Vec<_>>());
Expand Down Expand Up @@ -669,7 +613,11 @@ fn bench_rev_1(b: &mut Bencher) {
#[bench]
fn bench_rev_2(b: &mut Bencher) {
let data = black_box([0; LEN]);
b.iter(|| example_plain_slow(&data));
b.iter(|| {
let mut v = Vec::<u32>::with_capacity(data.len());
v.extend(data.iter().rev());
v
});
}

#[bench]
Expand All @@ -685,7 +633,16 @@ fn bench_map_regular(b: &mut Bencher) {
#[bench]
fn bench_map_fast(b: &mut Bencher) {
let data = black_box([(0, 0); LEN]);
b.iter(|| map_fast(&data));
b.iter(|| {
let mut result = Vec::with_capacity(data.len());
for i in 0..data.len() {
unsafe {
*result.get_unchecked_mut(i) = data[i].0;
result.set_len(i);
}
}
result
});
}

fn random_sorted_fill(mut seed: u32, buf: &mut [u32]) {
Expand Down

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