80 lines
2.2 KiB
C++
80 lines
2.2 KiB
C++
/*
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* Smoother.h
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*
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* This source file is part of the FoundationDB open source project
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*
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* Copyright 2013-2022 Apple Inc. and the FoundationDB project authors
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#pragma once
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#include "flow/flow.h"
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#include <cmath>
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template <class T>
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class SmootherImpl {
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// Times (t) are expected to be nondecreasing
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double eFoldingTime;
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double total;
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mutable double time, estimate;
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void update(double t) const {
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double elapsed = t - time;
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if (elapsed) {
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time = t;
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estimate += (total - estimate) * (1 - exp(-elapsed / eFoldingTime));
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}
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}
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protected:
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explicit SmootherImpl(double eFoldingTime) : eFoldingTime(eFoldingTime) { reset(0); }
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public:
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void reset(double value) {
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time = 0;
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total = value;
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estimate = value;
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}
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void setTotal(double total, double t = T::now()) { addDelta(total - this->total, t); }
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void addDelta(double delta, double t = T::now()) {
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update(t);
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total += delta;
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}
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// smoothTotal() is a continuous (under)estimate of the sum of all addDeltas()
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double smoothTotal(double t = T::now()) const {
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update(t);
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return estimate;
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}
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// smoothRate() is d/dt[smoothTotal], and is NOT continuous
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double smoothRate(double t = T::now()) const {
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update(t);
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return (total - estimate) / eFoldingTime;
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}
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double getTotal() const { return total; }
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};
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class Smoother : public SmootherImpl<Smoother> {
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public:
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static double now() { return ::now(); }
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explicit Smoother(double eFoldingTime) : SmootherImpl<Smoother>(eFoldingTime) {}
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};
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class TimerSmoother : public SmootherImpl<TimerSmoother> {
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public:
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static double now() { return timer(); }
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explicit TimerSmoother(double eFoldingTime) : SmootherImpl<TimerSmoother>(eFoldingTime) {}
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};
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