Open
Conversation
Adds overflow protection to the Count-Min-Log sketch implementation. Previously, incrementing a register at its maximum value would wrap around to zero, leading to incorrect counts. Now, registers saturate at their maximum value and updates that would cause overflow are rejected. The changes: - Check for overflow before incrementing in Update - Add overflow protection to BulkUpdate - Handle overflow in value calculation - Add comprehensive tests for overflow behavior This is a critical fix for correctness when dealing with high-frequency items, particularly when using smaller register sizes like uint8.
Replace fixed-width encoding with variable-length integers for sketch
serialization. This change:
- Removes unsafe.Sizeof dependency
- Reduces serialized size for sparse sketches
- Adds bounds checking for register capacity
- Simplifies encoding/decoding logic
- Adds fuzzing for serialization correctness
The new format uses a fixed 16-byte header followed by varint-encoded
registers. Note: This is a breaking change to the binary format.
Added benchmarks show the impact on serialization performance and size.
```
goos: darwin
goarch: arm64
pkg: github.com/seiflotfy/count-min-log
cpu: Apple M3 Max
│ before │ after │
│ sec/op │ sec/op vs base │
Sketch/fn=MarshalBinary/eps=0.010/delta=0.010-16 1.631µ ± 2% 1.137µ ± 6% -30.27% (p=0.002 n=6)
Sketch/fn=UnmarshalBinary/eps=0.010/delta=0.010-16 925.8n ± 1% 2264.5n ± 1% +144.59% (p=0.002 n=6)
Sketch/fn=MarshalBinary/eps=0.050/delta=0.010-16 344.4n ± 7% 243.8n ± 4% -29.20% (p=0.002 n=6)
Sketch/fn=UnmarshalBinary/eps=0.050/delta=0.010-16 255.5n ± 4% 522.5n ± 7% +104.52% (p=0.002 n=6)
Sketch/fn=MarshalBinary/eps=0.100/delta=0.010-16 183.1n ± 2% 130.6n ± 1% -28.72% (p=0.002 n=6)
Sketch/fn=UnmarshalBinary/eps=0.100/delta=0.010-16 166.1n ± 1% 301.6n ± 2% +81.61% (p=0.002 n=6)
geomean 399.1n 484.4n +21.37%
│ before │ after │
│ bytes │ bytes vs base │
Sketch/fn=MarshalBinary/eps=0.010/delta=0.010-16 2.672Ki ± 0% 1.344Ki ± 0% -49.71% (p=0.002 n=6)
Sketch/fn=MarshalBinary/eps=0.050/delta=0.010-16 566.0 ± 0% 291.0 ± 0% -48.59% (p=0.002 n=6)
Sketch/fn=MarshalBinary/eps=0.100/delta=0.010-16 296.0 ± 0% 156.0 ± 0% -47.30% (p=0.002 n=6)
geomean 771.0 396.8 -48.54%
│ before │ after │
│ B/op │ B/op vs base │
Sketch/fn=MarshalBinary/eps=0.010/delta=0.010-16 3.000Ki ± 0% 1.375Ki ± 0% -54.17% (p=0.002 n=6)
Sketch/fn=UnmarshalBinary/eps=0.010/delta=0.010-16 3.172Ki ± 0% 3.172Ki ± 0% ~ (p=1.000 n=6) ¹
Sketch/fn=MarshalBinary/eps=0.050/delta=0.010-16 576.0 ± 0% 320.0 ± 0% -44.44% (p=0.002 n=6)
Sketch/fn=UnmarshalBinary/eps=0.050/delta=0.010-16 752.0 ± 0% 752.0 ± 0% ~ (p=1.000 n=6) ¹
Sketch/fn=MarshalBinary/eps=0.100/delta=0.010-16 320.0 ± 0% 160.0 ± 0% -50.00% (p=0.002 n=6)
Sketch/fn=UnmarshalBinary/eps=0.100/delta=0.010-16 464.0 ± 0% 464.0 ± 0% ~ (p=1.000 n=6) ¹
geomean 928.7 658.7 -29.07%
¹ all samples are equal
│ before │ after │
│ allocs/op │ allocs/op vs base │
Sketch/fn=MarshalBinary/eps=0.010/delta=0.010-16 1.000 ± 0% 1.000 ± 0% ~ (p=1.000 n=6) ¹
Sketch/fn=UnmarshalBinary/eps=0.010/delta=0.010-16 5.000 ± 0% 5.000 ± 0% ~ (p=1.000 n=6) ¹
Sketch/fn=MarshalBinary/eps=0.050/delta=0.010-16 1.000 ± 0% 1.000 ± 0% ~ (p=1.000 n=6) ¹
Sketch/fn=UnmarshalBinary/eps=0.050/delta=0.010-16 5.000 ± 0% 5.000 ± 0% ~ (p=1.000 n=6) ¹
Sketch/fn=MarshalBinary/eps=0.100/delta=0.010-16 1.000 ± 0% 1.000 ± 0% ~ (p=1.000 n=6) ¹
Sketch/fn=UnmarshalBinary/eps=0.100/delta=0.010-16 5.000 ± 0% 5.000 ± 0% ~ (p=1.000 n=6) ¹
geomean 2.236 2.236 +0.00%
¹ all samples are equal
```
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
1 participant
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
Adds overflow protection to the Count-Min-Log sketch implementation. Previously, incrementing a register at its maximum value would wrap around to zero, leading to incorrect counts. Now, registers saturate at their maximum value and updates that would cause overflow are rejected.
The changes:
This is a critical fix for correctness when dealing with high-frequency items, particularly when using smaller register sizes like uint8.
Also, replace fixed-width encoding with variable-length integers for sketch serialization.
The new format uses a fixed 16-byte header followed by varint-encoded registers. Note: This is a breaking change to the binary format.