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Implement MergeBy::fold #920

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merged 4 commits into from Apr 24, 2024
+81 −73
Merged

Implement MergeBy::fold #920

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e8b0daa
Implement `MergeBy::fold`
kinto-b Apr 18, 2024
1955923
Make merge specialization benchmark more realistic
kinto-b Apr 23, 2024
752f021
Remove `MergeBy::last` and `MergeBy::count`
kinto-b Apr 24, 2024
ca57605
Simplify `OrderingOrBool::merge`
kinto-b Apr 24, 2024
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16 changes: 8 additions & 8 deletions benches/specializations.rs
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Expand Up @@ -582,29 +582,29 @@ bench_specializations! {
}
merge {
{
let v1 = black_box(vec![0; 1024]);
let v2 = black_box(vec![0; 768]);
let v1 = black_box((0..1024).collect_vec());
let v2 = black_box((0..768).collect_vec());
}
v1.iter().merge(&v2)
}
merge_by {
{
let v1 = black_box(vec![0; 1024]);
let v2 = black_box(vec![0; 768]);
let v1 = black_box((0..1024).collect_vec());
let v2 = black_box((0..768).collect_vec());
}
v1.iter().merge_by(&v2, PartialOrd::ge)
}
merge_join_by_ordering {
{
let v1 = black_box(vec![0; 1024]);
let v2 = black_box(vec![0; 768]);
let v1 = black_box((0..1024).collect_vec());
let v2 = black_box((0..768).collect_vec());
}
v1.iter().merge_join_by(&v2, Ord::cmp)
}
merge_join_by_bool {
{
let v1 = black_box(vec![0; 1024]);
let v2 = black_box(vec![0; 768]);
let v1 = black_box((0..1024).collect_vec());
let v2 = black_box((0..768).collect_vec());
}
v1.iter().merge_join_by(&v2, PartialOrd::ge)
}
Expand Down
138 changes: 73 additions & 65 deletions src/merge_join.rs
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Expand Up @@ -115,7 +115,7 @@ pub trait OrderingOrBool<L, R> {
// "merge" never returns (Some(...), Some(...), ...) so Option<Either<I::Item, J::Item>>
// is appealing but it is always followed by two put_backs, so we think the compiler is
// smart enough to optimize it. Or we could move put_backs into "merge".
fn merge(&mut self, left: L, right: R) -> (Option<L>, Option<R>, Self::MergeResult);
fn merge(&mut self, left: L, right: R) -> (Option<Either<L, R>>, Self::MergeResult);
fn size_hint(left: SizeHint, right: SizeHint) -> SizeHint;
}

Expand All @@ -127,11 +127,11 @@ impl<L, R, F: FnMut(&L, &R) -> Ordering> OrderingOrBool<L, R> for MergeFuncLR<F,
fn right(right: R) -> Self::MergeResult {
EitherOrBoth::Right(right)
}
fn merge(&mut self, left: L, right: R) -> (Option<L>, Option<R>, Self::MergeResult) {
fn merge(&mut self, left: L, right: R) -> (Option<Either<L, R>>, Self::MergeResult) {
match self.0(&left, &right) {
Ordering::Equal => (None, None, EitherOrBoth::Both(left, right)),
Ordering::Less => (None, Some(right), EitherOrBoth::Left(left)),
Ordering::Greater => (Some(left), None, EitherOrBoth::Right(right)),
Ordering::Equal => (None, EitherOrBoth::Both(left, right)),
Ordering::Less => (Some(Either::Right(right)), EitherOrBoth::Left(left)),
Ordering::Greater => (Some(Either::Left(left)), EitherOrBoth::Right(right)),
}
}
fn size_hint(left: SizeHint, right: SizeHint) -> SizeHint {
Expand All @@ -154,11 +154,11 @@ impl<L, R, F: FnMut(&L, &R) -> bool> OrderingOrBool<L, R> for MergeFuncLR<F, boo
fn right(right: R) -> Self::MergeResult {
Either::Right(right)
}
fn merge(&mut self, left: L, right: R) -> (Option<L>, Option<R>, Self::MergeResult) {
fn merge(&mut self, left: L, right: R) -> (Option<Either<L, R>>, Self::MergeResult) {
if self.0(&left, &right) {
(None, Some(right), Either::Left(left))
(Some(Either::Right(right)), Either::Left(left))
} else {
(Some(left), None, Either::Right(right))
(Some(Either::Left(left)), Either::Right(right))
}
}
fn size_hint(left: SizeHint, right: SizeHint) -> SizeHint {
Expand All @@ -175,11 +175,11 @@ impl<T, F: FnMut(&T, &T) -> bool> OrderingOrBool<T, T> for F {
fn right(right: T) -> Self::MergeResult {
right
}
fn merge(&mut self, left: T, right: T) -> (Option<T>, Option<T>, Self::MergeResult) {
fn merge(&mut self, left: T, right: T) -> (Option<Either<T, T>>, Self::MergeResult) {
if self(&left, &right) {
(None, Some(right), left)
(Some(Either::Right(right)), left)
} else {
(Some(left), None, right)
(Some(Either::Left(left)), right)
}
}
fn size_hint(left: SizeHint, right: SizeHint) -> SizeHint {
Expand All @@ -196,11 +196,11 @@ impl<T: PartialOrd> OrderingOrBool<T, T> for MergeLte {
fn right(right: T) -> Self::MergeResult {
right
}
fn merge(&mut self, left: T, right: T) -> (Option<T>, Option<T>, Self::MergeResult) {
fn merge(&mut self, left: T, right: T) -> (Option<Either<T, T>>, Self::MergeResult) {
if left <= right {
(None, Some(right), left)
(Some(Either::Right(right)), left)
} else {
(Some(left), None, right)
(Some(Either::Left(left)), right)
}
}
fn size_hint(left: SizeHint, right: SizeHint) -> SizeHint {
Expand Down Expand Up @@ -244,66 +244,71 @@ where
(Some(left), None) => Some(F::left(left)),
(None, Some(right)) => Some(F::right(right)),
(Some(left), Some(right)) => {
let (left, right, next) = self.cmp_fn.merge(left, right);
if let Some(left) = left {
self.left.put_back(left);
}
if let Some(right) = right {
self.right.put_back(right);
let (not_next, next) = self.cmp_fn.merge(left, right);
match not_next {
Some(Either::Left(l)) => {
self.left.put_back(l);
}
Some(Either::Right(r)) => {
self.right.put_back(r);
}
None => (),
}

Some(next)
}
}
}

fn size_hint(&self) -> SizeHint {
F::size_hint(self.left.size_hint(), self.right.size_hint())
}
fn fold<B, G>(mut self, init: B, mut f: G) -> B
where
Self: Sized,
G: FnMut(B, Self::Item) -> B,
{
let mut acc = init;
let mut left = self.left.next();
let mut right = self.right.next();

fn count(mut self) -> usize {
let mut count = 0;
loop {
match (self.left.next(), self.right.next()) {
(None, None) => break count,
(Some(_left), None) => break count + 1 + self.left.into_parts().1.count(),
(None, Some(_right)) => break count + 1 + self.right.into_parts().1.count(),
(Some(left), Some(right)) => {
count += 1;
let (left, right, _) = self.cmp_fn.merge(left, right);
if let Some(left) = left {
self.left.put_back(left);
match (left, right) {
(Some(l), Some(r)) => match self.cmp_fn.merge(l, r) {
(Some(Either::Right(r)), x) => {
acc = f(acc, x);
left = self.left.next();
right = Some(r);
}
if let Some(right) = right {
self.right.put_back(right);
(Some(Either::Left(l)), x) => {
acc = f(acc, x);
left = Some(l);
right = self.right.next();
}
(None, x) => {
acc = f(acc, x);
left = self.left.next();
right = self.right.next();
}
},
(Some(l), None) => {
self.left.put_back(l);
acc = self.left.fold(acc, |acc, x| f(acc, F::left(x)));
break;
}
}
}
}

fn last(mut self) -> Option<Self::Item> {
let mut previous_element = None;
loop {
match (self.left.next(), self.right.next()) {
(None, None) => break previous_element,
(Some(left), None) => {
break Some(F::left(self.left.into_parts().1.last().unwrap_or(left)))
}
(None, Some(right)) => {
break Some(F::right(self.right.into_parts().1.last().unwrap_or(right)))
(None, Some(r)) => {
self.right.put_back(r);
acc = self.right.fold(acc, |acc, x| f(acc, F::right(x)));
break;
}
(Some(left), Some(right)) => {
let (left, right, elem) = self.cmp_fn.merge(left, right);
if let Some(left) = left {
self.left.put_back(left);
}
if let Some(right) = right {
self.right.put_back(right);
}
previous_element = Some(elem);
(None, None) => {
break;
}
}
}

acc
}

fn size_hint(&self) -> SizeHint {
F::size_hint(self.left.size_hint(), self.right.size_hint())
}

fn nth(&mut self, mut n: usize) -> Option<Self::Item> {
Expand All @@ -317,12 +322,15 @@ where
(Some(_left), None) => break self.left.nth(n).map(F::left),
(None, Some(_right)) => break self.right.nth(n).map(F::right),
(Some(left), Some(right)) => {
let (left, right, _) = self.cmp_fn.merge(left, right);
if let Some(left) = left {
self.left.put_back(left);
}
if let Some(right) = right {
self.right.put_back(right);
let (not_next, _) = self.cmp_fn.merge(left, right);
match not_next {
Some(Either::Left(l)) => {
self.left.put_back(l);
}
Some(Either::Right(r)) => {
self.right.put_back(r);
}
None => (),
}
}
}
Expand Down