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Resize with a more conservative amount of space after deletions #86

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merged 1 commit into from Jun 6, 2019
Merged

Resize with a more conservative amount of space after deletions #86

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15 changes: 11 additions & 4 deletions src/raw/mod.rs
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Expand Up @@ -652,13 +652,20 @@ impl<T> RawTable<T> {
.checked_add(additional)
.ok_or_else(|| fallability.capacity_overflow())?;

// Rehash in-place without re-allocating if we have plenty of spare
// capacity that is locked up due to DELETED entries.
if new_items < bucket_mask_to_capacity(self.bucket_mask) / 2 {
let full_capacity = bucket_mask_to_capacity(self.bucket_mask);
if new_items <= full_capacity / 2 {
// Rehash in-place without re-allocating if we have plenty of spare
// capacity that is locked up due to DELETED entries.
self.rehash_in_place(hasher);
Ok(())
} else {
self.resize(new_items, hasher, fallability)
// Otherwise, conservatively resize to at least the next size up
// to avoid churning deletes into frequent rehashes.
self.resize(
usize::max(new_items, full_capacity + 1),
hasher,
fallability,
)
}
}

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