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Improve sift_down performance in BinaryHeap #81127

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Merged
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Mar 9, 2021
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Improve sift_down performance in BinaryHeap #81127

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4 changes: 2 additions & 2 deletions library/alloc/src/collections/binary_heap.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -565,7 +565,7 @@ impl<T: Ord> BinaryHeap<T> {
let mut child = 2 * hole.pos() + 1;

// Loop invariant: child == 2 * hole.pos() + 1.
while child < end - 1 {
while child <= end.saturating_sub(2) {
// compare with the greater of the two children
// SAFETY: child < end - 1 < self.len() and
// child + 1 < end <= self.len(), so they're valid indexes.
Expand Down Expand Up @@ -624,7 +624,7 @@ impl<T: Ord> BinaryHeap<T> {
let mut child = 2 * hole.pos() + 1;

// Loop invariant: child == 2 * hole.pos() + 1.
while child < end - 1 {
while child <= end.saturating_sub(2) {
// SAFETY: child < end - 1 < self.len() and
// child + 1 < end <= self.len(), so they're valid indexes.
// child == 2 * hole.pos() + 1 != hole.pos() and
Expand Down