1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
|
/*
* Copyright 2011 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.
*/
#ifndef RTC_BASE_ROLLING_ACCUMULATOR_H_
#define RTC_BASE_ROLLING_ACCUMULATOR_H_
#include <stddef.h>
#include <algorithm>
#include <vector>
#include "rtc_base/checks.h"
#include "rtc_base/numerics/running_statistics.h"
namespace webrtc {
// RollingAccumulator stores and reports statistics
// over N most recent samples.
//
// T is assumed to be an int, long, double or float.
template <typename T>
class RollingAccumulator {
public:
explicit RollingAccumulator(size_t max_count) : samples_(max_count) {
RTC_DCHECK(max_count > 0);
Reset();
}
~RollingAccumulator() {}
RollingAccumulator(const RollingAccumulator&) = delete;
RollingAccumulator& operator=(const RollingAccumulator&) = delete;
size_t max_count() const { return samples_.size(); }
size_t count() const { return static_cast<size_t>(stats_.Size()); }
void Reset() {
stats_ = webrtc_impl::RunningStatistics<T>();
next_index_ = 0U;
max_ = T();
max_stale_ = false;
min_ = T();
min_stale_ = false;
}
void AddSample(T sample) {
if (count() == max_count()) {
// Remove oldest sample.
T sample_to_remove = samples_[next_index_];
stats_.RemoveSample(sample_to_remove);
if (sample_to_remove >= max_) {
max_stale_ = true;
}
if (sample_to_remove <= min_) {
min_stale_ = true;
}
}
// Add new sample.
samples_[next_index_] = sample;
if (count() == 0 || sample >= max_) {
max_ = sample;
max_stale_ = false;
}
if (count() == 0 || sample <= min_) {
min_ = sample;
min_stale_ = false;
}
stats_.AddSample(sample);
// Update next_index_.
next_index_ = (next_index_ + 1) % max_count();
}
double ComputeMean() const { return stats_.GetMean().value_or(0); }
T ComputeMax() const {
if (max_stale_) {
RTC_DCHECK(count() > 0)
<< "It shouldn't be possible for max_stale_ && count() == 0";
max_ = samples_[next_index_];
for (size_t i = 1u; i < count(); i++) {
max_ = std::max(max_, samples_[(next_index_ + i) % max_count()]);
}
max_stale_ = false;
}
return max_;
}
T ComputeMin() const {
if (min_stale_) {
RTC_DCHECK(count() > 0)
<< "It shouldn't be possible for min_stale_ && count() == 0";
min_ = samples_[next_index_];
for (size_t i = 1u; i < count(); i++) {
min_ = std::min(min_, samples_[(next_index_ + i) % max_count()]);
}
min_stale_ = false;
}
return min_;
}
// O(n) time complexity.
// Weights nth sample with weight (learning_rate)^n. Learning_rate should be
// between (0.0, 1.0], otherwise the non-weighted mean is returned.
double ComputeWeightedMean(double learning_rate) const {
if (count() < 1 || learning_rate <= 0.0 || learning_rate >= 1.0) {
return ComputeMean();
}
double weighted_mean = 0.0;
double current_weight = 1.0;
double weight_sum = 0.0;
const size_t max_size = max_count();
for (size_t i = 0; i < count(); ++i) {
current_weight *= learning_rate;
weight_sum += current_weight;
// Add max_size to prevent underflow.
size_t index = (next_index_ + max_size - i - 1) % max_size;
weighted_mean += current_weight * samples_[index];
}
return weighted_mean / weight_sum;
}
// Compute estimated variance. Estimation is more accurate
// as the number of samples grows.
double ComputeVariance() const { return stats_.GetVariance().value_or(0); }
private:
webrtc_impl::RunningStatistics<T> stats_;
size_t next_index_;
mutable T max_;
mutable bool max_stale_;
mutable T min_;
mutable bool min_stale_;
std::vector<T> samples_;
};
} // namespace webrtc
// Re-export symbols from the webrtc namespace for backwards compatibility.
// TODO(bugs.webrtc.org/4222596): Remove once all references are updated.
#ifdef WEBRTC_ALLOW_DEPRECATED_NAMESPACES
namespace rtc {
using ::webrtc::RollingAccumulator;
} // namespace rtc
#endif // WEBRTC_ALLOW_DEPRECATED_NAMESPACES
#endif // RTC_BASE_ROLLING_ACCUMULATOR_H_
|
