1 files changed, 162 insertions, 0 deletions
diff --git a/sccomp/source/solver/DifferentialEvolution.hxx b/sccomp/source/solver/DifferentialEvolution.hxx
new file mode 100644
index 000000000..97453437c
--- /dev/null
+++ b/sccomp/source/solver/DifferentialEvolution.hxx
@@ -0,0 +1,162 @@
+/* -*- 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/.
+ *
+ */
+
+#pragma once
+
+#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;
+    }
+};
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */