Tanh.cpp

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/*
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#include <cmath>
 
#include "Utilities/GSLCompat.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;
    }
}  // namespace endfieldmodel