FastErf.h

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/*
    Copyright (C) 2022, University College London
    This file is part of STIR.
    SPDX-License-Identifier: Apache-2.0
    See STIR/LICENSE.txt for details
*/
 
#include "stir/numerics/BSplines1DRegularGrid.h"
 
#ifndef __stir_numerics_FastErf__H__
#  define __stir_numerics_FastErf__H__
 
START_NAMESPACE_STIR

class FastErf
{
private:
  int _num_samples;

  double _sampling_period;
 
  //  //! Used to check if setup has been run before parameter changes
  //  bool _is_setup = false;

  BSpline::BSplines1DRegularGrid<double, double> _spline;

  double _maximum_sample_value;

  std::vector<double> erf_values_vec;
 
public:
  explicit FastErf(const int num_samples = 1000, const float maximum_sample_value = 5)
      : _num_samples(num_samples),
        _maximum_sample_value(maximum_sample_value)
  {}

  inline int get_num_samples() const;
  inline void set_num_samples(int num_samples);

  inline double get_maximum_sample_value() const;
  inline void set_maximum_sample_value(double maximum_sample_value);

  inline void set_up();

  inline double get_erf_BSplines_interpolation(double xp) const;

  inline double get_erf_linear_interpolation(double xp) const;

  inline double get_erf_nearest_neighbour_interpolation(double xp) const;

  inline const double operator()(const double xp) const;
};
 
END_NAMESPACE_STIR
 
#  include "stir/numerics/FastErf.inl"
 
#endif // __stir_numerics_FastErf__H__