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#ifndef SCIQLOP_FUZZINGUTILS_H
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#define SCIQLOP_FUZZINGUTILS_H
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#include <algorithm>
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#include <random>
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/**
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* Class that proposes random utility methods
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*/
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class RandomGenerator {
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public:
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/// @return the unique instance of the random generator
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static RandomGenerator &instance();
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/// Generates a random double between [min, max]
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double generateDouble(double min, double max);
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/// Generates a random int between [min, max]
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int generateInt(int min, int max);
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/**
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* Returns a random element among the elements of a container. An item may be more likely to be
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* selected if it has an associated weight greater than other items
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* @param container the container from which to retrieve an element
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* @param weights the weight associated to each element of the container. The vector must have
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* the same size of the container for the weights to be effective
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* @param nbDraws the number of random draws to perform
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* @return the random element retrieved, an element built by default if the container is empty
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*/
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template <typename T, typename ValueType = typename T::value_type>
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ValueType randomChoice(const T &container, const std::vector<double> &weights = {});
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private:
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std::mt19937 m_Mt;
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explicit RandomGenerator();
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};
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template <typename T, typename ValueType>
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ValueType RandomGenerator::randomChoice(const T &container, const std::vector<double> &weights)
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{
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if (container.empty()) {
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return ValueType{};
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}
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// Generates weights for each element: if the weights passed in parameter are malformed (the
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// number of weights defined is inconsistent with the number of elements in the container, or
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// all weights are zero), default weights are used
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auto nbIndexes = container.size();
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std::vector<double> indexWeights(nbIndexes);
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if (weights.size() != nbIndexes || std::all_of(weights.cbegin(), weights.cend(),
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[](const auto &val) { return val == 0.; })) {
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std::fill(indexWeights.begin(), indexWeights.end(), 1.);
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}
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else {
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std::copy(weights.begin(), weights.end(), indexWeights.begin());
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}
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// Performs a draw to determine the index to return
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std::discrete_distribution<> d{indexWeights.cbegin(), indexWeights.cend()};
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return container.at(d(m_Mt));
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}
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#endif // SCIQLOP_FUZZINGUTILS
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