dirichlet_prior.h

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#ifndef META_DIRICHLET_PRIOR_H_
#define META_DIRICHLET_PRIOR_H_

#include "index/ranker/lm_ranker.h"
#include "index/ranker/ranker_factory.h"

namespace meta
{
namespace index
{

class dirichlet_prior : public language_model_ranker
{
  public:
    const static std::string id;

    const static constexpr double default_mu = 2000;

    dirichlet_prior(double mu = default_mu);

    double smoothed_prob(const score_data& sd) const override;

    double doc_constant(const score_data& sd) const override;

  private:
    const double mu_;
};

template <>
std::unique_ptr<ranker> make_ranker<dirichlet_prior>(const cpptoml::table&);
}
}
#endif