coderabbitai[bot]
commented
1 month ago Walkthrough
The changes optimize the Splay tree implementation by incorporating enhancements to prevent skewness, thereby improving performance in the crdt.Text structure. Key updates include the addition of a height field to nodes and optimized splay operations that adapt based on the number of operations performed, ensuring a balanced tree structure. Benchmark tests and assertions are also updated for accuracy, reflecting the new output representations for the Document structure.
Changes
| Files | Change Summary |
|---|---|
| pkg/document/document_test.go, test/bench/document_bench_test.go | Updated assertions for ToTestString() method outputs in both tests to reflect new array formats. |
| pkg/splay/splay.go, pkg/splay/splay_test.go | Enhanced Node and Tree structures with height management, optimized splay operations, and updated test assertions to match new output formats. |
Sequence Diagram(s)
sequenceDiagram
participant User
participant SplayTree
participant Node
User->>SplayTree: Insert Node
SplayTree->>Node: Create NewNode
Node->>Node: Initialize Height
SplayTree->>SplayTree: Update Height
SplayTree->>User: Return Tree StructureAssessment against linked issues
| Objective | Addressed | Explanation |
|---|---|---|
| Improve performance of Splay Tree to prevent skewness (##941) | ✅ |
Poem
In the forest where trees sway,
A splay tree danced today.
With heights anew and branches wide,
It skips the skew and takes in stride.
A hop, a leap, in code we trust,
Performance shines, it's a must! 🐇✨
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m4ushold
What this PR does / why we need it:
Why this is needed: Currently, the crdt.Text data structure uses a Splay tree. While Splay trees are efficient for performing operations in a continuous range, they have a downside where consecutively inserted elements may become linearly arranged in the tree, leading to a skew tree. When performing M operations on a tree with N nodes, the performance is generally guaranteed to be O((N+M) log N). However, if the tree becomes skewed, each operation might initially take O(N) time, though it could eventually improve. This skewness can degrade the performance of the crdt.Text data structure, making it crucial to explore ways to prevent this skewness and maintain the tree's performance and efficiency. This PR aims to address the performance and efficiency degradation in the crdt.Text data structure caused by skewness in the Splay tree.
What this PR does: In this Pull Request, we introduce a method called max_height_splay to reduce the skewness. This method involves finding the deepest leaf node and performing a splay operation on it every √n operations, where n is the number of splay operations performed. The time complexity of max_height_splay is also amortized O(log n), similar to other operations. A POC for this approach was implemented in C++, and the code can be found here.
Which issue(s) this PR fixes:
Fixes #941
Special notes for your reviewer: If operations are primarily occurring at the end of the document, performance degradation might still occur. Although this may require further research, it seems worthwhile to implement as it can provide good performance in most cases. I have added test code but did not include benchmark code. If you think it's needed, please mention me! And while adding the test code, I needed to check the height of the Splay tree nodes, which led to some modifications in other test code as well.
Does this PR introduce a user-facing change?:
Additional documentation:
Checklist:
Summary by CodeRabbit
New Features
Bug Fixes
Tests