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94 lines
2.3 KiB
C++
94 lines
2.3 KiB
C++
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* vim: set ts=8 sts=2 et sw=2 tw=80: */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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/* Calculate the rolling mean of a series of values. */
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#ifndef mozilla_RollingMean_h_
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#define mozilla_RollingMean_h_
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#include "mozilla/Assertions.h"
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#include "mozilla/Vector.h"
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#include <stddef.h>
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#include <type_traits>
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namespace mozilla {
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/**
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* RollingMean<T> calculates a rolling mean of the values it is given. It
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* accumulates the total as values are added and removed. The second type
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* argument S specifies the type of the total. This may need to be a bigger
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* type in order to maintain that the sum of all values in the average doesn't
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* exceed the maximum input value.
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*
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* WARNING: Float types are not supported due to rounding errors.
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*/
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template <typename T, typename S>
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class RollingMean {
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private:
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size_t mInsertIndex;
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size_t mMaxValues;
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Vector<T> mValues;
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S mTotal;
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public:
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static_assert(!std::is_floating_point_v<T>,
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"floating-point types are unsupported due to rounding "
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"errors");
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explicit RollingMean(size_t aMaxValues)
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: mInsertIndex(0), mMaxValues(aMaxValues), mTotal(0) {
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MOZ_ASSERT(aMaxValues > 0);
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}
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RollingMean& operator=(RollingMean&& aOther) = default;
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/**
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* Insert a value into the rolling mean.
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*/
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bool insert(T aValue) {
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MOZ_ASSERT(mValues.length() <= mMaxValues);
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if (mValues.length() == mMaxValues) {
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mTotal = mTotal - mValues[mInsertIndex] + aValue;
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mValues[mInsertIndex] = aValue;
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} else {
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if (!mValues.append(aValue)) {
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return false;
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}
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mTotal = mTotal + aValue;
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}
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mInsertIndex = (mInsertIndex + 1) % mMaxValues;
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return true;
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}
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/**
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* Calculate the rolling mean.
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*/
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T mean() const {
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MOZ_ASSERT(!empty());
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return T(mTotal / int64_t(mValues.length()));
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}
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bool empty() const { return mValues.empty(); }
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/**
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* Remove all values from the rolling mean.
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*/
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void clear() {
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mValues.clear();
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mInsertIndex = 0;
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mTotal = T(0);
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}
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size_t maxValues() const { return mMaxValues; }
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};
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} // namespace mozilla
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#endif // mozilla_RollingMean_h_
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