winnow.h

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#ifndef META_WINNOW_H_
#define META_WINNOW_H_

#include <vector>
#include <unordered_map>
#include "index/forward_index.h"
#include "classify/classifier/classifier.h"
#include "classify/classifier_factory.h"
#include "meta.h"

namespace meta
{
namespace classify
{

class winnow : public classifier
{
  public:
    const static constexpr double default_m = 1.5;
    const static constexpr double default_gamma = 0.05;
    const static constexpr size_t default_max_iter = 100;

    winnow(std::shared_ptr<index::forward_index> idx, double m = default_m,
           double gamma = default_gamma, size_t max_iter = default_max_iter);

    void train(const std::vector<doc_id>& docs) override;

    class_label classify(doc_id d_id) override;

    void reset() override;

    const static std::string id;

  private:
    double get_weight(const class_label& label, const term_id& term) const;

    void zero_weights(const std::vector<doc_id>& docs);

    std::unordered_map<class_label, std::unordered_map<term_id, double>>
        weights_;

    const double m_;

    const double gamma_;

    const size_t max_iter_;
};

template <>
std::unique_ptr<classifier>
    make_classifier<winnow>(const cpptoml::table& config,
                            std::shared_ptr<index::forward_index> idx);
}
}
#endif