Tanh.cpp

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#include <cmath>
 
#include "gsl/gsl_sf_gamma.h"
#include "gsl/gsl_sf_pow_int.h"
 
#include "AbsBeamline/EndFieldModel/Tanh.h"
 
namespace endfieldmodel {
 
std::vector< std::vector< std::vector<int> > > Tanh::_tdi;
 
Tanh::Tanh(double x0, double lambda, int max_index) : _x0(x0), _lambda(lambda) {
  setTanhDiffIndices(max_index);
}
 
Tanh::~Tanh() {}
 
Tanh* Tanh::clone() const {
    return new Tanh(*this);
}
 
 
double Tanh::getTanh(double x, int n) const {
  if (n == 0) return tanh((x+_x0)/_lambda);
  double t = 0;
  double lam_n = gsl_sf_pow_int(_lambda, n);
  double tanh_x = tanh((x+_x0)/_lambda);
  for (size_t i = 0; i < _tdi[n].size(); i++)
    t += 1./lam_n*static_cast<double>(_tdi[n][i][0])
            *gsl_sf_pow_int(tanh_x, _tdi[n][i][1]);
  return t;
}
 
double Tanh::getNegTanh(double x, int n) const {
  if (n == 0) return tanh((x-_x0)/_lambda);
  double t = 0;
  double lam_n = gsl_sf_pow_int(_lambda, n);
  double tanh_x = tanh((x-_x0)/_lambda);
  for (size_t i = 0; i < _tdi[n].size(); i++)
    t += 1./lam_n*static_cast<double>(_tdi[n][i][0])
            *gsl_sf_pow_int(tanh_x, _tdi[n][i][1]);
  return t;
}
 
double Tanh::function(double x, int n) const {
  return (getTanh(x, n)-getNegTanh(x, n))/2.;
}
 
void Tanh::setMaximumDerivative(size_t n) {
    setTanhDiffIndices(n);
}
 
 
void Tanh::setTanhDiffIndices(size_t n) {
  _tdi.reserve(n+1);
  if (_tdi.size() == 0) {
    _tdi.push_back(std::vector< std::vector<int> >(1, std::vector<int>(2)));
    _tdi[0][0][0] = 1;  // 1*tanh(x) - third index is redundant
    _tdi[0][0][1] = 1;
  }
  for (size_t i = _tdi.size(); i < n+1; ++i) {
    _tdi.push_back(std::vector< std::vector<int> >());
    for (size_t j = 0; j < _tdi[i-1].size(); ++j) {
      int value = _tdi[i-1][j][1];
      if (value != 0) {
        std::vector<int> new_vec(_tdi[i-1][j]);
        new_vec[0] *= value;
        new_vec[1] -= 1;
        _tdi[i].push_back(new_vec);
        std::vector<int> new_vec2(_tdi[i-1][j]);
        new_vec2[0] *= -value;
        new_vec2[1] += 1;
        _tdi[i].push_back(new_vec2);
      }
    }
    _tdi[i] = CompactVector(_tdi[i]);
  }
}
 
std::vector< std::vector<int> > Tanh::getTanhDiffIndices(size_t n) {
  setTanhDiffIndices(n);
  return _tdi[n];
}
 
void Tanh::rescale(double scaleFactor) {
  _x0 *= scaleFactor;
  _lambda *= scaleFactor;
}
 
 
 
std::ostream& Tanh::print(std::ostream& out) const {
    out << "Tanh model with centre length: " << _x0 
        << " end length: " << _lambda;
    return out;
}
}