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Validate minimum samples for slope calculation #53

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arjunshajitech merged 1 commit into from
Aug 24, 2026
+4 −0
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Validate minimum samples for slope calculation #53

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4 changes: 4 additions & 0 deletions gcc/trendline_estimator.go
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Original file line number Diff line number Diff line change
Expand Up @@ -79,6 +79,10 @@ func (e *trendlineEstimator) update(arrivalTime time.Time, interGroupDelay time.
}

func fitSlope(packets []packetDelay) (float64, bool) {
if len(packets) < 2 {
return 0, false
}

@JoTurk JoTurk Aug 24, 2026

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Does this actually do anything?

denominator should be 0 for len < 2 because (x - avgX) is 0 for len 1, and for len zero we don't run the calculation loop at all

https://github.com/arjunshajitech/bwe/blob/be8c36cb457cac63e8dd0aedd90b2b499110a734/gcc/trendline_estimator.go#L106-L108

I'm all for adding an early return to make the code explicit but does it actually fix anything?

@arjunshajitech arjunshajitech Aug 24, 2026

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The early return doesn't fix a functional issue, but it makes the minimum input requirement explicit and avoids unnecessary calculations.

@JoTurk JoTurk Aug 24, 2026

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Can we amend the commit message then? :)

@arjunshajitech arjunshajitech Aug 24, 2026

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I was reading the implementation and, while comparing it with the WebRTC implementation (https://webrtc.googlesource.com/src/+/refs/heads/main/modules/congestion_controller/goog_cc/trendline_estimator.cc#58), I added the check mainly for simplicity and clarity.

If this doesn't make sense, feel free to close the PR.

@arjunshajitech arjunshajitech Aug 24, 2026

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Can we amend the commit message then? :)

sure

@JoTurk JoTurk Aug 24, 2026

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it's fine to add an early return, i think it will make the code easier to follow, it's just that we use commit messages in releases and "Fix prevent invalid slope calculation" would be misleading for people who read releases :)

@arjunshajitech arjunshajitech Aug 24, 2026

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Updated.

sumX := 0.0
sumY := 0.0

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