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-rw-r--r-- | sccomp/source/solver/DifferentialEvolution.hxx | 165 |
1 files changed, 165 insertions, 0 deletions
diff --git a/sccomp/source/solver/DifferentialEvolution.hxx b/sccomp/source/solver/DifferentialEvolution.hxx new file mode 100644 index 000000000..7d1882135 --- /dev/null +++ b/sccomp/source/solver/DifferentialEvolution.hxx @@ -0,0 +1,165 @@ +/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */ +/* + * This file is part of the LibreOffice project. + * + * This Source Code Form is subject to the terms of the Mozilla Public + * License, v. 2.0. If a copy of the MPL was not distributed with this + * file, You can obtain one at http://mozilla.org/MPL/2.0/. + * + */ + +#ifndef INCLUDED_SCCOMP_SOURCE_DIFFERENTIALEVOLUTION_HXX +#define INCLUDED_SCCOMP_SOURCE_DIFFERENTIALEVOLUTION_HXX + +#include <vector> +#include <random> +#include <limits> + +struct Individual +{ + std::vector<double> mVariables; +}; + +template <typename DataProvider> class DifferentialEvolutionAlgorithm +{ + static constexpr double mnDifferentialWeight = 0.5; // [0, 2] + static constexpr double mnCrossoverProbability = 0.9; // [0, 1] + + static constexpr double constAcceptedPrecision = 0.000000001; + + DataProvider& mrDataProvider; + + size_t mnPopulationSize; + std::vector<Individual> maPopulation; + + std::random_device maRandomDevice; + std::mt19937 maGenerator; + size_t mnDimensionality; + + std::uniform_int_distribution<> maRandomPopulation; + std::uniform_int_distribution<> maRandomDimensionality; + std::uniform_real_distribution<> maRandom01; + + Individual maBestCandidate; + double mfBestFitness; + int mnGeneration; + int mnLastChange; + +public: + DifferentialEvolutionAlgorithm(DataProvider& rDataProvider, size_t nPopulationSize) + : mrDataProvider(rDataProvider) + , mnPopulationSize(nPopulationSize) + , maGenerator(maRandomDevice()) + , mnDimensionality(mrDataProvider.getDimensionality()) + , maRandomPopulation(0, mnPopulationSize - 1) + , maRandomDimensionality(0, mnDimensionality - 1) + , maRandom01(0.0, 1.0) + , mfBestFitness(std::numeric_limits<double>::lowest()) + , mnGeneration(0) + , mnLastChange(0) + { + } + + std::vector<double> const& getResult() { return maBestCandidate.mVariables; } + + int getGeneration() { return mnGeneration; } + + int getLastChange() { return mnLastChange; } + + void initialize() + { + mnGeneration = 0; + mnLastChange = 0; + maPopulation.clear(); + maBestCandidate.mVariables.clear(); + + // Initialize population with individuals that have been initialized with uniform random + // noise + // uniform noise means random value inside your search space + maPopulation.reserve(mnPopulationSize); + for (size_t i = 0; i < mnPopulationSize; ++i) + { + maPopulation.emplace_back(); + Individual& rIndividual = maPopulation.back(); + mrDataProvider.initializeVariables(rIndividual.mVariables, maGenerator); + } + } + + // Calculate one generation + bool next() + { + bool bBestChanged = false; + + for (size_t agentIndex = 0; agentIndex < mnPopulationSize; ++agentIndex) + { + // calculate new candidate solution + + // pick random point from population + size_t x = agentIndex; // randomPopulation(generator); + size_t a, b, c; + + // create a copy of chosen random agent in population + Individual& rOriginal = maPopulation[x]; + Individual aCandidate(rOriginal); + + // pick three different random points from population + do + { + a = maRandomPopulation(maGenerator); + } while (a == x); + + do + { + b = maRandomPopulation(maGenerator); + } while (b == x || b == a); + + do + { + c = maRandomPopulation(maGenerator); + + } while (c == x || c == a || c == b); + + size_t randomIndex = maRandomDimensionality(maGenerator); + + for (size_t index = 0; index < mnDimensionality; ++index) + { + double randomCrossoverProbability = maRandom01(maGenerator); + if (index == randomIndex || randomCrossoverProbability < mnCrossoverProbability) + { + double fVarA = maPopulation[a].mVariables[index]; + double fVarB = maPopulation[b].mVariables[index]; + double fVarC = maPopulation[c].mVariables[index]; + + double fNewValue = fVarA + mnDifferentialWeight * (fVarB - fVarC); + fNewValue = mrDataProvider.boundVariable(index, fNewValue); + aCandidate.mVariables[index] = fNewValue; + } + } + + double fCandidateFitness = mrDataProvider.calculateFitness(aCandidate.mVariables); + + // see if is better than original, if so replace + if (fCandidateFitness > mrDataProvider.calculateFitness(rOriginal.mVariables)) + { + maPopulation[x] = aCandidate; + + if (fCandidateFitness > mfBestFitness) + { + if (std::abs(fCandidateFitness - mfBestFitness) > constAcceptedPrecision) + { + bBestChanged = true; + mnLastChange = mnGeneration; + } + mfBestFitness = fCandidateFitness; + maBestCandidate = maPopulation[x]; + } + } + } + mnGeneration++; + return bBestChanged; + } +}; + +#endif + +/* vim:set shiftwidth=4 softtabstop=4 expandtab: */ |