File: exponential_moving_average.cc

package info (click to toggle)
chromium 138.0.7204.183-1~deb12u1
  • links: PTS, VCS
  • area: main
  • in suites: bookworm-proposed-updates
  • size: 6,080,960 kB
  • sloc: cpp: 34,937,079; ansic: 7,176,967; javascript: 4,110,704; python: 1,419,954; asm: 946,768; xml: 739,971; pascal: 187,324; sh: 89,623; perl: 88,663; objc: 79,944; sql: 50,304; cs: 41,786; fortran: 24,137; makefile: 21,811; php: 13,980; tcl: 13,166; yacc: 8,925; ruby: 7,485; awk: 3,720; lisp: 3,096; lex: 1,327; ada: 727; jsp: 228; sed: 36
file content (53 lines) | stat: -rw-r--r-- 1,358 bytes parent folder | download | duplicates (8) 
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
 
// Copyright 2018 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "components/performance_manager/persistence/site_data/exponential_moving_average.h"

#include <cmath>

#include "base/check.h"

namespace performance_manager {

ExponentialMovingAverage::ExponentialMovingAverage(float alpha)
    : alpha_(alpha) {
  DCHECK(alpha_ > 0.0 && alpha_ < 1.0);
}

void ExponentialMovingAverage::AppendDatum(float datum) {
  if (num_datums_ == 0) {
    first_datum_ = datum;
    value_ = datum;
  } else {
    value_ = value_ * (1.0 - alpha_) + datum * alpha_;
  }

  ++num_datums_;
}

void ExponentialMovingAverage::PrependDatum(float datum) {
  if (num_datums_ == 0) {
    first_datum_ = datum;
    value_ = datum;
  } else {
    // Back the previous first datum out of the value.
    float beta = 1.0 - alpha_;
    float betan = std::pow(1.0 - alpha_, num_datums_ - 1);
    float first_datum_contrib = first_datum_ * betan;
    float other_datums_contrib = value_ - first_datum_contrib;
    first_datum_ = datum;
    value_ = datum * betan * beta + first_datum_contrib * alpha_ +
             other_datums_contrib;
  }

  ++num_datums_;
}

void ExponentialMovingAverage::Clear() {
  first_datum_ = 0.0;
  value_ = 0.0;
  num_datums_ = 0;
}

}  // namespace performance_manager