InitializeRandom.hpp

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#ifndef KMEANS_INITIALIZE_RANDOM_HPP
#define KMEANS_INITIALIZE_RANDOM_HPP 
 
#include <algorithm>
#include <cstdint>
#include <random>
 
#include "Initialize.hpp"
#include "copy_into_array.hpp"
 
#include "aarand/aarand.hpp"
 
namespace kmeans {
 
struct InitializeRandomOptions {
    uint64_t seed = 6523u;
};
 
template<class Matrix_ = SimpleMatrix<double, int>, typename Cluster_ = int, typename Float_ = double>
class InitializeRandom : public Initialize<Matrix_, Cluster_, Float_> { 
private:
    InitializeRandomOptions my_options;
 
public:
    InitializeRandom(InitializeRandomOptions options) : my_options(std::move(options)) {}
 
    InitializeRandom() = default;
 
public:
    InitializeRandomOptions& get_options() {
        return my_options;
    }
 
public:
    Cluster_ run(const Matrix_& data, Cluster_ ncenters, Float_* centers) const {
        std::mt19937_64 eng(my_options.seed);
        auto nobs = data.num_observations();
        std::vector<typename Matrix_::index_type> chosen(std::min(nobs, static_cast<typename Matrix_::index_type>(ncenters)));
        aarand::sample(nobs, ncenters, chosen.begin(), eng);
        internal::copy_into_array(data, chosen, centers);
        return chosen.size();
    }
};
 
}
 
#endif