| /* |
| * libjingle |
| * Copyright 2011, Google Inc. |
| * |
| * Redistribution and use in source and binary forms, with or without |
| * modification, are permitted provided that the following conditions are met: |
| * |
| * 1. Redistributions of source code must retain the above copyright notice, |
| * this list of conditions and the following disclaimer. |
| * 2. Redistributions in binary form must reproduce the above copyright notice, |
| * this list of conditions and the following disclaimer in the documentation |
| * and/or other materials provided with the distribution. |
| * 3. The name of the author may not be used to endorse or promote products |
| * derived from this software without specific prior written permission. |
| * |
| * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED |
| * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF |
| * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO |
| * EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, |
| * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, |
| * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; |
| * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, |
| * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR |
| * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF |
| * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| */ |
| |
| #ifndef TALK_BASE_ROLLINGACCUMULATOR_H_ |
| #define TALK_BASE_ROLLINGACCUMULATOR_H_ |
| |
| #include <vector> |
| |
| #include "talk/base/common.h" |
| |
| namespace talk_base { |
| |
| // 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) |
| : count_(0), |
| next_index_(0), |
| sum_(0.0), |
| sum_2_(0.0), |
| samples_(max_count) { |
| } |
| ~RollingAccumulator() { |
| } |
| |
| int max_count() const { |
| return samples_.size(); |
| } |
| |
| int count() const { |
| return count_; |
| } |
| |
| void AddSample(T sample) { |
| if (count_ == max_count()) { |
| // Remove oldest sample. |
| T sample_to_remove = samples_[next_index_]; |
| sum_ -= sample_to_remove; |
| sum_2_ -= sample_to_remove * sample_to_remove; |
| } else { |
| // Increase count of samples. |
| ++count_; |
| } |
| // Add new sample. |
| samples_[next_index_] = sample; |
| sum_ += sample; |
| sum_2_ += sample * sample; |
| // Update next_index_. |
| next_index_ = (next_index_ + 1) % max_count(); |
| } |
| |
| T ComputeSum() const { |
| return static_cast<T>(sum_); |
| } |
| |
| T ComputeMean() const { |
| if (count_ == 0) { |
| return static_cast<T>(0); |
| } |
| return static_cast<T>(sum_ / count_); |
| } |
| |
| // Compute estimated variance. Estimation is more accurate |
| // as the number of samples grows. |
| T ComputeVariance() const { |
| if (count_ == 0) { |
| return static_cast<T>(0); |
| } |
| // Var = E[x^2] - (E[x])^2 |
| double count_inv = 1.0 / count_; |
| double mean_2 = sum_2_ * count_inv; |
| double mean = sum_ * count_inv; |
| return static_cast<T>(mean_2 - (mean * mean)); |
| } |
| |
| private: |
| int count_; |
| int next_index_; |
| double sum_; // Sum(x) |
| double sum_2_; // Sum(x*x) |
| std::vector<T> samples_; |
| |
| DISALLOW_COPY_AND_ASSIGN(RollingAccumulator); |
| }; |
| |
| } // namespace talk_base |
| |
| #endif // TALK_BASE_ROLLINGACCUMULATOR_H_ |