Balancing Tree to Prevent Skewness #1025
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To prevent the tree from becoming skewed, I balanced it by splaying the first node of the sequence every 500 linear insert operations. The value 500 was determined experimentally.
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## main #1025 +/- ##
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- Coverage 48.76% 48.75% -0.01%
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Files 79 79
Lines 11343 11355 +12
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Actionable comments posted: 1
🧹 Outside diff range and nitpick comments (3)
pkg/splay/splay.go (3)
96-97: Add documentation for new fields inTreestructTo improve code readability and maintainability, please add comments explaining the purpose of the new fields
linearCountandfirstNodein theTreestruct. This will help other developers understand how these fields are used to prevent skewness in the splay tree.
126-126: ResetfirstNodeafter splayingAfter splaying
firstNodeand resettinglinearCount, it's advisable to also resetfirstNodetonil. This prevents holding a reference to a node that may have been altered or deleted later, which can help avoid potential memory leaks or unintended behavior.Apply this diff:
t.Splay(t.firstNode) t.linearCount = 0 + t.firstNode = nil
124-126: Define splay threshold as a named constantUsing the magic number
500as the splay threshold can reduce code clarity. Consider defining it as a named constant or making it configurable. This enhances readability and makes future adjustments easier.Apply this diff:
+const splayThreshold = 500 ... } else if t.linearCount > splayThreshold { t.Splay(t.firstNode) t.linearCount = 0 }
| if t.linearCount == 1 { | ||
| t.firstNode = node | ||
| } else if t.linearCount > 500 { | ||
| t.Splay(t.firstNode) | ||
| t.linearCount = 0 | ||
| } |
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Ensure firstNode is valid before splaying
There's a potential risk that firstNode might have been modified or removed from the tree before the splay operation when linearCount exceeds the threshold. This could lead to unexpected behavior or runtime errors. Consider adding a check to ensure that firstNode is still a valid node in the tree before performing the splay operation.
Apply this diff to include a validity check:
} else if t.linearCount > 500 {
+ if t.isValidNode(t.firstNode) {
t.Splay(t.firstNode)
+ }
t.linearCount = 0
}And implement the isValidNode method:
func (t *Tree[V]) isValidNode(node *Node[V]) bool {
return node != nil && node.hasLinks()
}
m4ushold
changed the title
To prevent the tree from becoming skewed, I balanced it by splaying the first node of the sequence every 500 linear insert operations. The value 500 was determined experimentally.
What this PR does / why we need it:
Description:
This pull request (PR) introduces an enhanced method for balancing a tree during insert operations to prevent skewness. The goal is to optimize performance by replacing the inefficient height-based splay operations with a more effective approach.
Changes Made:
Linear Operation Detection and Balancing:
Optimization of Splay Trigger Frequency:
Code Modifications:
linearCountandfirstNodefields to theTreestructure to track consecutive insert operations.InsertAftermethod to conditionally perform a splay operation and resetlinearCount.Performance Improvements:
For more details, you can check this
Which issue(s) this PR fixes:
Fixes #941
Special notes for your reviewer:
Does this PR introduce a user-facing change?:
Additional documentation:
Checklist:
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