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Have all methods of Filter and FilterMap use internal iteration #58730

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Merged
merged 4 commits into from
Mar 3, 2019
Merged

Have all methods of Filter and FilterMap use internal iteration #58730

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1fd2f16
Have all methods of Filter and FilterMap use internal iteration
timvermeulen Feb 25, 2019
8884771
Add relevant benchmarks
timvermeulen Feb 27, 2019
ec2e4ba
Improve existing benchmarks to prevent extreme optimizations
timvermeulen Feb 27, 2019
88bd624
Add trailing newline
timvermeulen Feb 27, 2019
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32 changes: 30 additions & 2 deletions src/libcore/benches/iter.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -185,13 +185,13 @@ bench_sums! {
bench_sums! {
bench_filter_sum,
bench_filter_ref_sum,
(0i64..1000000).filter(|x| x % 2 == 0)
(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 % 2 == 0)
(0i64..1000000).chain(0..1000000).filter(|x| x % 3 == 0)
}

bench_sums! {
Expand Down Expand Up @@ -306,3 +306,31 @@ fn bench_skip_then_zip(b: &mut Bencher) {
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()
})
}
37 changes: 7 additions & 30 deletions src/libcore/iter/adapters/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -681,12 +681,7 @@ impl<I: Iterator, P> Iterator for Filter<I, P> where P: FnMut(&I::Item) -> bool

#[inline]
fn next(&mut self) -> Option<I::Item> {
for x in &mut self.iter {
if (self.predicate)(&x) {
return Some(x);
}
}
None
self.try_for_each(Err).err()
}

#[inline]
Expand All @@ -707,12 +702,9 @@ impl<I: Iterator, P> Iterator for Filter<I, P> where P: FnMut(&I::Item) -> bool
// Using the branchless version will also simplify the LLVM byte code, thus
// leaving more budget for LLVM optimizations.
#[inline]
fn count(mut self) -> usize {
let mut count = 0;
for x in &mut self.iter {
count += (self.predicate)(&x) as usize;
}
count
fn count(self) -> usize {
let mut predicate = self.predicate;
self.iter.map(|x| predicate(&x) as usize).sum()

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}

#[inline]
Expand Down Expand Up @@ -746,12 +738,7 @@ impl<I: DoubleEndedIterator, P> DoubleEndedIterator for Filter<I, P>
{
#[inline]
fn next_back(&mut self) -> Option<I::Item> {
for x in self.iter.by_ref().rev() {
if (self.predicate)(&x) {
return Some(x);
}
}
None
self.try_rfold((), |_, x| Err(x)).err()
}

#[inline]
Expand Down Expand Up @@ -820,12 +807,7 @@ impl<B, I: Iterator, F> Iterator for FilterMap<I, F>

#[inline]
fn next(&mut self) -> Option<B> {
for x in self.iter.by_ref() {
if let Some(y) = (self.f)(x) {
return Some(y);
}
}
None
self.try_for_each(Err).err()
}

#[inline]
Expand Down Expand Up @@ -863,12 +845,7 @@ impl<B, I: DoubleEndedIterator, F> DoubleEndedIterator for FilterMap<I, F>
{
#[inline]
fn next_back(&mut self) -> Option<B> {
for x in self.iter.by_ref().rev() {
if let Some(y) = (self.f)(x) {
return Some(y);
}
}
None
self.try_rfold((), |_, x| Err(x)).err()
}

#[inline]
Expand Down