GoaLitiuM/FlaxEngine
1
0
Fork 0
Code Issues Pull Requests Actions 7 Packages Projects Releases Wiki Activity

Refactor HashSet and Dictionary collections capacity to handle rehashing when too many elements were deleted

Browse Source
This commit is contained in:
Wojtek Figat
2023-11-02 19:59:01 +01:00
parent c0a8d29453
commit 087cfd7a8c
3 changed files with 246 additions and 90 deletions
Download Patch File Download Diff File Expand all files Collapse all files

171
Source/Engine/Core/Collections/HashSet.h
View File

@@ -37,26 +37,33 @@ public:
private:
State _state;
void Free()
FORCE_INLINE void Free()
{
if (_state == Occupied)
Memory::DestructItem(&Item);
_state = Empty;
}
void Delete()
FORCE_INLINE void Delete()
{
_state = Deleted;
Memory::DestructItem(&Item);
}
template<typename ItemType>
void Occupy(const ItemType& item)
FORCE_INLINE void Occupy(const ItemType& item)
{
Memory::ConstructItems(&Item, &item, 1);
_state = Occupied;
}
template<typename ItemType>
FORCE_INLINE void Occupy(ItemType& item)
{
Memory::MoveItems(&Item, &item, 1);
_state = Occupied;
}
FORCE_INLINE bool IsEmpty() const
{
return _state == Empty;
@@ -82,6 +89,7 @@ public:
private:
int32 _elementsCount = 0;
int32 _deletedCount = 0;
int32 _size = 0;
AllocationData _allocation;
@@ -107,12 +115,12 @@ public:
/// </summary>
/// <param name="other">The other collection to move.</param>
HashSet(HashSet&& other) noexcept
: _elementsCount(other._elementsCount)
, _size(other._size)
{
_elementsCount = other._elementsCount;
_deletedCount = other._deletedCount;
_size = other._size;
other._elementsCount = 0;
other._deletedCount = 0;
other._size = 0;
_allocation.Swap(other._allocation);
}
@@ -150,8 +158,10 @@ public:
Clear();
_allocation.Free();
_elementsCount = other._elementsCount;
_deletedCount = other._deletedCount;
_size = other._size;
other._elementsCount = 0;
other._deletedCount = 0;
other._size = 0;
_allocation.Swap(other._allocation);
}
@@ -163,7 +173,7 @@ public:
/// </summary>
~HashSet()
{
SetCapacity(0, false);
Clear();
}
public:
@@ -210,6 +220,7 @@ public:
HashSet* _collection;
int32 _index;
public:
Iterator(HashSet* collection, const int32 index)
: _collection(collection)
, _index(index)
@@ -222,7 +233,12 @@ public:
{
}
public:
Iterator()
: _collection(nullptr)
, _index(-1)
{
}
Iterator(const Iterator& i)
: _collection(i._collection)
, _index(i._index)
@@ -236,6 +252,11 @@ public:
}
public:
FORCE_INLINE int32 Index() const
{
return _index;
}
FORCE_INLINE bool IsEnd() const
{
return _index == _collection->_size;
@@ -331,12 +352,12 @@ public:
/// </summary>
void Clear()
{
if (_elementsCount != 0)
if (_elementsCount + _deletedCount != 0)
{
Bucket* data = _allocation.Get();
for (int32 i = 0; i < _size; i++)
data[i].Free();
_elementsCount = 0;
_elementsCount = _deletedCount = 0;
}
}
@@ -371,7 +392,7 @@ public:
oldAllocation.Swap(_allocation);
const int32 oldSize = _size;
const int32 oldElementsCount = _elementsCount;
_elementsCount = 0;
_deletedCount = _elementsCount = 0;
if (capacity != 0 && (capacity & (capacity - 1)) != 0)
{
// Align capacity value to the next power of two (http://graphics.stanford.edu/~seander/bithacks.html#RoundUpPowerOf2)
@@ -394,11 +415,18 @@ public:
Bucket* oldData = oldAllocation.Get();
if (oldElementsCount != 0 && preserveContents)
{
// TODO; move keys and values on realloc
FindPositionResult pos;
for (int32 i = 0; i < oldSize; i++)
{
if (oldData[i].IsOccupied())
Add(oldData[i].Item);
Bucket& oldBucket = oldData[i];
if (oldBucket.IsOccupied())
{
FindPosition(oldBucket.Item, pos);
Bucket* bucket = &_allocation.Get()[pos.FreeSlotIndex];
Memory::MoveItems(&bucket->Item, &oldBucket.Item, 1);
bucket->_state = Bucket::Occupied;
_elementsCount++;
}
}
}
if (oldElementsCount != 0)
@@ -415,14 +443,26 @@ public:
/// <param name="preserveContents">True if preserve collection data when changing its size, otherwise collection after resize will be empty.</param>
void EnsureCapacity(int32 minCapacity, bool preserveContents = true)
{
if (Capacity() >= minCapacity)
if (_size >= minCapacity)
return;
if (minCapacity < DICTIONARY_DEFAULT_CAPACITY)
minCapacity = DICTIONARY_DEFAULT_CAPACITY;
const int32 capacity = _allocation.CalculateCapacityGrow(_size, minCapacity);
int32 capacity = _allocation.CalculateCapacityGrow(_size, minCapacity);
if (capacity < DICTIONARY_DEFAULT_CAPACITY)
capacity = DICTIONARY_DEFAULT_CAPACITY;
SetCapacity(capacity, preserveContents);
}
/// <summary>
/// Swaps the contents of collection with the other object without copy operation. Performs fast internal data exchange.
/// </summary>
/// <param name="other">The other collection.</param>
void Swap(HashSet& other)
{
::Swap(_elementsCount, other._elementsCount);
::Swap(_deletedCount, other._deletedCount);
::Swap(_size, other._size);
_allocation.Swap(other._allocation);
}
public:
/// <summary>
/// Add element to the collection.
@@ -432,24 +472,23 @@ public:
template<typename ItemType>
bool Add(const ItemType& item)
{
// Ensure to have enough memory for the next item (in case of new element insertion)
EnsureCapacity(_elementsCount + 1);
Bucket* bucket = OnAdd(item);
if (bucket)
bucket->Occupy(item);
return bucket != nullptr;
}
// Find location of the item or place to insert it
FindPositionResult pos;
FindPosition(item, pos);
// Check if object has been already added
if (pos.ObjectIndex != -1)
return false;
// Insert
ASSERT(pos.FreeSlotIndex != -1);
Bucket* bucket = &_allocation.Get()[pos.FreeSlotIndex];
bucket->Occupy(item);
_elementsCount++;
return true;
/// <summary>
/// Add element to the collection.
/// </summary>
/// <param name="item">The element to add to the set.</param>
/// <returns>True if element has been added to the collection, otherwise false if the element is already present.</returns>
bool Add(T&& item)
{
Bucket* bucket = OnAdd(item);
if (bucket)
bucket->Occupy(MoveTemp(item));
return bucket != nullptr;
}
/// <summary>
@@ -479,6 +518,7 @@ public:
{
_allocation.Get()[pos.ObjectIndex].Delete();
_elementsCount--;
_deletedCount++;
return true;
}
return false;
@@ -497,6 +537,7 @@ public:
ASSERT(_allocation.Get()[i._index].IsOccupied());
_allocation.Get()[i._index].Delete();
_elementsCount--;
_deletedCount++;
return true;
}
return false;
@@ -585,7 +626,7 @@ public:
return Iterator(this, _size);
}
protected:
private:
/// <summary>
/// The result container of the set item lookup searching.
/// </summary>
@@ -646,4 +687,64 @@ protected:
result.ObjectIndex = -1;
result.FreeSlotIndex = insertPos;
}
template<typename ItemType>
Bucket* OnAdd(const ItemType& key)
{
// Check if need to rehash elements (prevent many deleted elements that use too much of capacity)
if (_deletedCount > _size / DICTIONARY_DEFAULT_SLACK_SCALE)
Compact();
// Ensure to have enough memory for the next item (in case of new element insertion)
EnsureCapacity((_elementsCount + 1) * DICTIONARY_DEFAULT_SLACK_SCALE + _deletedCount);
// Find location of the item or place to insert it
FindPositionResult pos;
FindPosition(key, pos);
// Ensure key is unknown
ASSERT(pos.ObjectIndex == -1 && "That key has been already added to the dictionary.");
// Insert
ASSERT(pos.FreeSlotIndex != -1);
_elementsCount++;
return &_allocation.Get()[pos.FreeSlotIndex];
}
void Compact()
{
if (_elementsCount == 0)
{
// Fast path if it's empty
Bucket* data = _allocation.Get();
for (int32 i = 0; i < _size; i++)
data[i]._state = Bucket::Empty;
}
else
{
// Rebuild entire table completely
AllocationData oldAllocation;
oldAllocation.Swap(_allocation);
_allocation.Allocate(_size);
Bucket* data = _allocation.Get();
for (int32 i = 0; i < _size; i++)
data[i]._state = Bucket::Empty;
Bucket* oldData = oldAllocation.Get();
FindPositionResult pos;
for (int32 i = 0; i < _size; i++)
{
Bucket& oldBucket = oldData[i];
if (oldBucket.IsOccupied())
{
FindPosition(oldBucket.Item, pos);
Bucket* bucket = &_allocation.Get()[pos.FreeSlotIndex];
Memory::MoveItems(&bucket->Item, &oldBucket.Item, 1);
bucket->_state = Bucket::Occupied;
}
}
for (int32 i = 0; i < _size; i++)
oldData[i].Free();
}
_deletedCount = 0;
}
};