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Specialize "loops of next" #818

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merged 8 commits into from
Dec 14, 2023
Merged

Specialize "loops of next" #818

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4fc8734
`FilterOk::next`: use `find`
Philippe-Cholet Nov 20, 2023
0969d4c
`FilterMapOk::next`: use `find_map`
Philippe-Cholet Nov 20, 2023
7df930e
`UniqueBy::next`: use `find`
Philippe-Cholet Nov 20, 2023
64952fc
`UniqueBy::next_back`: use `rfind`
Philippe-Cholet Nov 20, 2023
a1ec8fb
`Unique::next`: use `find_map`
Philippe-Cholet Nov 20, 2023
2c5a8a8
`Unique::next_back`: use `rev().find_map`
Philippe-Cholet Nov 20, 2023
e286c1b
`partition`: use `rfind`
Philippe-Cholet Nov 20, 2023
b87cc6a
Bench `partition`
Philippe-Cholet Dec 13, 2023
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19 changes: 18 additions & 1 deletion benches/bench1.rs
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Original file line number Diff line number Diff line change
@@ -1,4 +1,4 @@
use criterion::{black_box, criterion_group, criterion_main, Criterion};
use criterion::{black_box, criterion_group, criterion_main, BatchSize, Criterion};
use itertools::free::cloned;
use itertools::iproduct;
use itertools::Itertools;
Expand Down Expand Up @@ -648,6 +648,22 @@ fn step_range_10(c: &mut Criterion) {
});
}

fn vec_iter_mut_partition(c: &mut Criterion) {
let data = std::iter::repeat(-1024i32..1024)
.take(256)
.flatten()
.collect_vec();
c.bench_function("vec iter mut partition", move |b| {
b.iter_batched(
|| data.clone(),
|mut data| {
black_box(itertools::partition(black_box(&mut data), |n| *n >= 0));
},
BatchSize::LargeInput,
)
});
}

fn cartesian_product_iterator(c: &mut Criterion) {
let xs = vec![0; 16];

Expand Down Expand Up @@ -803,6 +819,7 @@ criterion_group!(
step_vec_10,
step_range_2,
step_range_10,
vec_iter_mut_partition,
cartesian_product_iterator,
multi_cartesian_product_iterator,
cartesian_product_nested_for,
Expand Down
32 changes: 10 additions & 22 deletions src/adaptors/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -901,17 +901,11 @@ where
type Item = Result<T, E>;

fn next(&mut self) -> Option<Self::Item> {
loop {
match self.iter.next() {
Some(Ok(v)) => {
if (self.f)(&v) {
return Some(Ok(v));
}
}
Some(Err(e)) => return Some(Err(e)),
None => return None,
}
}
let f = &mut self.f;
self.iter.find(|res| match res {
Ok(t) => f(t),
_ => true,
})
}

fn size_hint(&self) -> (usize, Option<usize>) {
Expand Down Expand Up @@ -988,17 +982,11 @@ where
type Item = Result<U, E>;

fn next(&mut self) -> Option<Self::Item> {
loop {
match self.iter.next() {
Some(Ok(v)) => {
if let Some(v) = (self.f)(v) {
return Some(Ok(v));
}
}
Some(Err(e)) => return Some(Err(e)),
None => return None,
}
}
let f = &mut self.f;
self.iter.find_map(|res| match res {
Ok(t) => f(t).map(Ok),
Err(e) => Some(Err(e)),
})
}

fn size_hint(&self) -> (usize, Option<usize>) {
Expand Down
15 changes: 4 additions & 11 deletions src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -4054,18 +4054,11 @@ where
{
let mut split_index = 0;
let mut iter = iter.into_iter();
'main: while let Some(front) = iter.next() {
while let Some(front) = iter.next() {
if !pred(front) {
loop {
match iter.next_back() {
Some(back) => {
if pred(back) {
std::mem::swap(front, back);
break;
}
}
None => break 'main,
}
match iter.rfind(|back| pred(back)) {
Some(back) => std::mem::swap(front, back),
None => break,
}
}
split_index += 1;
Expand Down
36 changes: 14 additions & 22 deletions src/unique_impl.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -61,13 +61,8 @@ where
type Item = I::Item;

fn next(&mut self) -> Option<Self::Item> {
while let Some(v) = self.iter.next() {
let key = (self.f)(&v);
if self.used.insert(key, ()).is_none() {
return Some(v);
}
}
None
let Self { iter, used, f } = self;
iter.find(|v| used.insert(f(v), ()).is_none())
}

#[inline]
Expand All @@ -89,13 +84,8 @@ where
F: FnMut(&I::Item) -> V,
{
fn next_back(&mut self) -> Option<Self::Item> {
while let Some(v) = self.iter.next_back() {
let key = (self.f)(&v);
if self.used.insert(key, ()).is_none() {
return Some(v);
}
}
None
let Self { iter, used, f } = self;
iter.rfind(|v| used.insert(f(v), ()).is_none())
}
}

Expand All @@ -115,14 +105,15 @@ where
type Item = I::Item;

fn next(&mut self) -> Option<Self::Item> {
while let Some(v) = self.iter.iter.next() {
if let Entry::Vacant(entry) = self.iter.used.entry(v) {
let UniqueBy { iter, used, .. } = &mut self.iter;
iter.find_map(|v| {
if let Entry::Vacant(entry) = used.entry(v) {
let elt = entry.key().clone();
entry.insert(());
return Some(elt);
}
}
None
None
})
}

#[inline]
Expand All @@ -142,14 +133,15 @@ where
I::Item: Eq + Hash + Clone,
{
fn next_back(&mut self) -> Option<Self::Item> {
while let Some(v) = self.iter.iter.next_back() {
if let Entry::Vacant(entry) = self.iter.used.entry(v) {
let UniqueBy { iter, used, .. } = &mut self.iter;
iter.rev().find_map(|v| {
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Off-topic: Is it strange that there's rfind, but no rfind_map?

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It's not off-topic to me. I was wondering the same question while writing this.
Maybe there is no large performance gain to expect compare to .rev().method(). I searched a bit but did not find anything.
More generally, DoubleEndedIterator does not have a lot of methods.

if let Entry::Vacant(entry) = used.entry(v) {
let elt = entry.key().clone();
entry.insert(());
return Some(elt);
}
}
None
None
})
}
}

Expand Down