Martino FerrariandClaude Sonnet 4.6
41ab151a2f
Adds TimeBase.h/cpp with ClockOffset (latched wall-clock offset with one-sided recalibration on positive drift only, so early-arriving packets do not wobble the trace) and HrtRateFit (sliding-window OLS that recovers an unknown hrt tick rate from receive timestamps). Also adds TimeSignalScale() which maps UDPS type codes to seconds-per-count. 9 new tests, all 28 pass. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
73 lines
2.2 KiB
C++
73 lines
2.2 KiB
C++
#include "TimeBase.h"
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#include <cmath>
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namespace udpscope {
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/* UDPS_T_UINT64 == 6 in Common/UDP/UDPSProtocol.h. Spelled numerically so this
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* translation unit stays free of the C client header. */
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static constexpr uint8_t kTypeUint64 = 6u;
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double TimeSignalScale(uint8_t typeCode) {
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return (typeCode == kTypeUint64) ? 1.0e-9 : 1.0e-6;
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}
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double ClockOffset::map(double producerSec, double wallSec) {
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/* Recalibrate only when wall is significantly ahead of the prediction.
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* Early-arriving packets (wall < prediction) are normal network jitter and
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* must not reset the offset — doing so would wobble the trace. A large
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* positive error means the producer clock jumped back or restarted. */
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if (!valid_ || (wallSec - (offset_ + producerSec)) > kRecalibThresholdS) {
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offset_ = wallSec - producerSec;
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valid_ = true;
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}
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return offset_ + producerSec;
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}
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void HrtRateFit::reset() {
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samples_.clear();
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n_ = 0;
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rate_ = 0.0;
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}
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void HrtRateFit::add(uint64_t hrt, double wallSec) {
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samples_.push_back(Sample{static_cast<double>(hrt), wallSec});
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if (samples_.size() > kWindow) { samples_.pop_front(); }
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n_++;
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if (n_ >= kMinSamples) { refit(); }
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}
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void HrtRateFit::refit() {
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const size_t n = samples_.size();
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if (n < 2) { return; }
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/* Least squares slope of hrt against wall time. Both are subtracted from
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* their first value first: raw hrt counts and epoch seconds are large
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* enough that the naive sums lose precision. */
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const double h0 = samples_.front().hrt;
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const double w0 = samples_.front().wall;
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double sw = 0.0, sh = 0.0, sww = 0.0, swh = 0.0;
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for (const Sample& s : samples_) {
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const double w = s.wall - w0;
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const double h = s.hrt - h0;
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sw += w;
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sh += h;
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sww += w * w;
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swh += w * h;
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}
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const double dn = static_cast<double>(n);
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const double denom = dn * sww - sw * sw;
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if (std::fabs(denom) < 1e-12) { return; }
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const double slope = (dn * swh - sw * sh) / denom;
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if (slope > 0.0 && std::isfinite(slope)) { rate_ = slope; }
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}
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double HrtRateFit::toSeconds(uint64_t hrt) const {
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if (rate_ <= 0.0) { return 0.0; }
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return static_cast<double>(hrt) / rate_;
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}
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} /* namespace udpscope */
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