mirror of
https://github.com/mollyim/webrtc.git
synced 2025-05-15 14:50:39 +01:00
890f62b8fe
This CL implements Welford's algorithm for a numerically stable computation of the variance. This implementation is plugged in SamplesStatsCounter class (adapter pattern). A 'NumericalStability' unit test has been added, whose previous implementation of SamplesStatsCounter failed to pass. Follow-up CLs will factorize more occurences of duplicated and misbehaved computations. Bug: webrtc:10412 Change-Id: Id807c3d34e9c780fb1cbd769d30b655c575c88ac Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/131394 Commit-Queue: Yves Gerey <yvesg@google.com> Reviewed-by: Artem Titov <titovartem@webrtc.org> Reviewed-by: Karl Wiberg <kwiberg@webrtc.org> Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org> Cr-Commit-Position: refs/heads/master@{#27547}
69 lines
2.2 KiB
C++
69 lines
2.2 KiB
C++
/*
|
|
* Copyright (c) 2018 The WebRTC project authors. All Rights Reserved.
|
|
*
|
|
* Use of this source code is governed by a BSD-style license
|
|
* that can be found in the LICENSE file in the root of the source
|
|
* tree. An additional intellectual property rights grant can be found
|
|
* in the file PATENTS. All contributing project authors may
|
|
* be found in the AUTHORS file in the root of the source tree.
|
|
*/
|
|
|
|
#include "rtc_base/numerics/samples_stats_counter.h"
|
|
|
|
#include <cmath>
|
|
|
|
#include "absl/algorithm/container.h"
|
|
|
|
namespace webrtc {
|
|
|
|
SamplesStatsCounter::SamplesStatsCounter() = default;
|
|
SamplesStatsCounter::~SamplesStatsCounter() = default;
|
|
SamplesStatsCounter::SamplesStatsCounter(const SamplesStatsCounter&) = default;
|
|
SamplesStatsCounter& SamplesStatsCounter::operator=(
|
|
const SamplesStatsCounter&) = default;
|
|
SamplesStatsCounter::SamplesStatsCounter(SamplesStatsCounter&&) = default;
|
|
SamplesStatsCounter& SamplesStatsCounter::operator=(SamplesStatsCounter&&) =
|
|
default;
|
|
|
|
void SamplesStatsCounter::AddSample(double value) {
|
|
stats_.AddSample(value);
|
|
samples_.push_back(value);
|
|
sorted_ = false;
|
|
}
|
|
|
|
void SamplesStatsCounter::AddSamples(const SamplesStatsCounter& other) {
|
|
stats_.MergeStatistics(other.stats_);
|
|
samples_.insert(samples_.end(), other.samples_.begin(), other.samples_.end());
|
|
sorted_ = false;
|
|
}
|
|
|
|
double SamplesStatsCounter::GetPercentile(double percentile) {
|
|
RTC_DCHECK(!IsEmpty());
|
|
RTC_CHECK_GE(percentile, 0);
|
|
RTC_CHECK_LE(percentile, 1);
|
|
if (!sorted_) {
|
|
absl::c_sort(samples_);
|
|
sorted_ = true;
|
|
}
|
|
const double raw_rank = percentile * (samples_.size() - 1);
|
|
double int_part;
|
|
double fract_part = std::modf(raw_rank, &int_part);
|
|
size_t rank = static_cast<size_t>(int_part);
|
|
if (fract_part >= 1.0) {
|
|
// It can happen due to floating point calculation error.
|
|
rank++;
|
|
fract_part -= 1.0;
|
|
}
|
|
|
|
RTC_DCHECK_GE(rank, 0);
|
|
RTC_DCHECK_LT(rank, samples_.size());
|
|
RTC_DCHECK_GE(fract_part, 0);
|
|
RTC_DCHECK_LT(fract_part, 1);
|
|
RTC_DCHECK(rank + fract_part == raw_rank);
|
|
|
|
const double low = samples_[rank];
|
|
const double high = samples_[std::min(rank + 1, samples_.size() - 1)];
|
|
return low + fract_part * (high - low);
|
|
}
|
|
|
|
} // namespace webrtc
|