objective_function.h

#ifndef LIGHTGBM_OBJECTIVE_FUNCTION_H_
#define LIGHTGBM_OBJECTIVE_FUNCTION_H_
 
#include <LightGBM/meta.h>
#include <LightGBM/config.h>
#include <LightGBM/dataset.h>
#include <functional>
 
namespace LightGBM {
class ObjectiveFunction {
public:
  virtual ~ObjectiveFunction() {}
 
  virtual void Init(const Metadata& metadata, data_size_t num_data) = 0;
 
  virtual void GetGradients(const double* score,
    score_t* gradients, score_t* hessians) const = 0;
 
  virtual const char* GetName() const = 0;
 
  virtual bool IsConstantHessian() const { return false; }
 
  virtual bool IsRenewTreeOutput() const { return false; }
 
  virtual double RenewTreeOutput(double ori_output, const double*,
                                 const data_size_t*,
                                 const data_size_t*,
                                 data_size_t) const { return ori_output; }
 
  virtual double RenewTreeOutput(double ori_output, double,
                                  const data_size_t*,
                                  const data_size_t*,
                                  data_size_t) const {
                                  return ori_output;
  }
 
  virtual double BoostFromScore(int /*class_id*/) const { return 0.0; }
 
  virtual bool ClassNeedTrain(int /*class_id*/) const { return true; }
 
  virtual bool SkipEmptyClass() const { return false; }
 
  virtual int NumModelPerIteration() const { return 1; }
 
  virtual int NumPredictOneRow() const { return 1; }
 
  virtual bool NeedAccuratePrediction() const { return true; }
 
  virtual void ConvertOutput(const double* input, double* output) const {
    output[0] = input[0];
  }
 
  virtual std::string ToString() const = 0;
 
  ObjectiveFunction() = default;
  ObjectiveFunction& operator=(const ObjectiveFunction&) = delete;
  ObjectiveFunction(const ObjectiveFunction&) = delete;
 
  LIGHTGBM_EXPORT static ObjectiveFunction* CreateObjectiveFunction(const std::string& type,
    const Config& config);
 
  LIGHTGBM_EXPORT static ObjectiveFunction* CreateObjectiveFunction(const std::string& str);
};
 
}  // namespace LightGBM
 
#endif   // LightGBM_OBJECTIVE_FUNCTION_H_