Fix incorrenct indexing #391
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WalkthroughImplements defensive fixes and indexing corrections in Changes
Sequence Diagram(s)sequenceDiagram
autonumber
actor Caller
participant Pred as Predictive
Caller->>Pred: getOvershootAdjustMillis(params)
rect rgb(230,245,255)
note over Pred: compute local rate and guard early
Pred->>Pred: getRate(measurements, cutoff)
alt stop index underflow risk
note right of Pred: while (i > 0 && measurementTimes[i-1] > cutoff)
end
alt tiny variance (tdev2 < 1e-10)
Pred-->>Pred: return 0.0 (degenerate)
else alt non-positive slope
Pred-->>Pred: return 0.0 (non-positive volume)
end
end
alt rate < 1e-10
Pred-->>Caller: 0.0 (avoid division)
else
Pred-->>Caller: overshootMillis (uses cached rate)
end
Estimated code review effort🎯 3 (Moderate) | ⏱️ ~20 minutes Poem
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Actionable comments posted: 0
Caution
Some comments are outside the diff and can’t be posted inline due to platform limitations.
⚠️ Outside diff range comments (1)
src/display/core/predictive.h (1)
4-5: Include what you use.This header uses
std::vectorandstd::powbut doesn’t include their headers. Avoid relying on transitive includes.#include <Arduino.h> +#include <vector> +#include <cmath>
🧹 Nitpick comments (4)
src/display/core/predictive.h (4)
45-47: Indexing fix is correct; avoid pow in the hot loop.Use precomputed deltas and multiplication to reduce floating-point overhead on MCU targets.
- tdev_vdev += (measurementTimes[j] - t_mean) * (measurements[j] - v_mean); - tdev2 += pow(measurementTimes[j] - t_mean, 2.0); + const double dt = measurementTimes[j] - t_mean; + const double dv = measurements[j] - v_mean; + tdev_vdev += dt * dv; + tdev2 += dt * dt;
48-53: Near-zero denominator guard is good; name the threshold.Minor: give the magic number a name for readability and easier tuning.
- // Prevent division by zero - if (tdev2 < 1e-10) { + // Prevent division by near-zero denominator (units: ms^2) + constexpr double kTdev2Epsilon = 1e-10; + if (tdev2 < kTdev2Epsilon) { return 0.0; }
54-56: Comment mismatch on units.The code returns volume/ms; the comment suggests seconds. Align the comment to avoid confusion.
- double volumePerMilliSecond = tdev_vdev / tdev2; // the slope (volume per millisecond) of the linear best fit - return volumePerMilliSecond > 0 ? volumePerMilliSecond : 0.0; // return 0 if it is not positive, convert to seconds + double volumePerMilliSecond = tdev_vdev / tdev2; // slope (volume per millisecond) of the linear best fit + return volumePerMilliSecond > 0 ? volumePerMilliSecond : 0.0; // return 0 if it is not positive (units: volume/ms)
62-70: Division-by-zero guard is correct; clarify negative overshoot behavior.If actual < expected, result is negative ms. Is that intended? Consider clamping to 0 for “overshoot” semantics.
double rate = getRate(measurementTimes.back()); // Prevent division by zero if (rate < 1e-10) { return 0.0; } - - return overshoot / rate; + // If actual <= expected, there is no overshoot to adjust. + if (overshoot <= 0.0) { + return 0.0; + } + return overshoot / rate;
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src/display/core/predictive.h(3 hunks)
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🔇 Additional comments (1)
src/display/core/predictive.h (1)
25-27: Good underflow safeguard in cutoff scan.The added
i > 0guard prevents size_t wraparound and out-of-bounds access when the window excludes all points. LGTM.
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