mosesdecoder/moses/SyntacticLanguageModel.h

//

#ifndef moses_SyntacticLanguageModel_h
#define moses_SyntacticLanguageModel_h

#include "FeatureFunction.h"
#include <stdexcept>

class YModel; // hidden model
class XModel; // observed model

namespace Moses
{

  template <class MH, class MO> class SyntacticLanguageModelFiles;
  
  class SyntacticLanguageModel : public StatefulFeatureFunction {

  public:

    SyntacticLanguageModel(const std::vector<std::string>& filePaths,
			   const std::vector<float>& weights,
			   const FactorType factorType,
			   const size_t beamWidth);

    ~SyntacticLanguageModel();

    size_t GetNumScoreComponents() const;

    const FFState* EmptyHypothesisState(const InputType &input) const;

    FFState* Evaluate(const Hypothesis& cur_hypo,
		      const FFState* prev_state,
		      ScoreComponentCollection* accumulator) const;

    FFState* EvaluateChart(const ChartHypothesis& cur_hypo,
                           int featureID,
                           ScoreComponentCollection* accumulator) const {
      throw std::runtime_error("Syntactic LM can only be used with phrase-based decoder.");
    }


    //    double perplexity();

  private:

    const size_t m_NumScoreComponents;
    SyntacticLanguageModelFiles<YModel,XModel>* m_files;
    const FactorType m_factorType;
    const size_t m_beamWidth;

  };


}

#endif