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Improve SortedSet DeepCopy performance #56561

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merged 3 commits into from
Oct 12, 2021
Merged

Improve SortedSet DeepCopy performance #56561

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a4a240a
SortedSet recursive deep copy
johnthcall Sep 25, 2021
4c53f23
Make DeepCopy iterative
johnthcall Oct 6, 2021
294976f
Undo accidental delete
johnthcall Oct 6, 2021
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42 changes: 14 additions & 28 deletions src/libraries/System.Collections/src/System/Collections/Generic/SortedSet.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -1681,41 +1681,27 @@ public Node DeepClone(int count)
#if DEBUG
Debug.Assert(count == GetCount());
#endif

// Breadth-first traversal to recreate nodes, preorder traversal to replicate nodes.

var originalNodes = new Stack<Node>(2 * Log2(count) + 2);
var newNodes = new Stack<Node>(2 * Log2(count) + 2);
Node newRoot = ShallowClone();

Node? originalCurrent = this;
Node newCurrent = newRoot;
var pendingNodes = new Stack<(Node source, Node target)>(2 * Log2(count) + 2);
pendingNodes.Push((this, newRoot));

while (originalCurrent != null)
while (pendingNodes.TryPop(out var next))
{
originalNodes.Push(originalCurrent);
newNodes.Push(newCurrent);
newCurrent.Left = originalCurrent.Left?.ShallowClone();
originalCurrent = originalCurrent.Left;
newCurrent = newCurrent.Left!;
}
Node clonedNode;

while (originalNodes.Count != 0)
{
originalCurrent = originalNodes.Pop();
newCurrent = newNodes.Pop();

Node? originalRight = originalCurrent.Right;
Node? newRight = originalRight?.ShallowClone();
newCurrent.Right = newRight;
if (next.source.Left is Node left)
{
clonedNode = left.ShallowClone();
next.target.Left = clonedNode;
pendingNodes.Push((left, clonedNode));
}

while (originalRight != null)
if (next.source.Right is Node right)
{
originalNodes.Push(originalRight);
newNodes.Push(newRight!);
newRight!.Left = originalRight.Left?.ShallowClone();
originalRight = originalRight.Left;
newRight = newRight.Left;
clonedNode = right.ShallowClone();
next.target.Right = clonedNode;
pendingNodes.Push((right, clonedNode));
}
}

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