xinterpolation.h

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#pragma once

#include "xerror.h"
#include "xvector.h"
#include <algorithm>
#include <gsl/gsl_errno.h>
#include <gsl/gsl_spline.h>

namespace nmx::gsl {

class Interpolation
{
private:
    gsl_spline *_workspace = nullptr; //gsl-interne Datenstruktur
    gsl_interp_accel *_accel = nullptr; //effiziente Suche im Datensatz

public:
    Interpolation() = delete;

    template<class X, class Y>
    inline Interpolation(const gsl_interp_type *type, const X &x, const Y &y) {
        size_t _dim = x.size();
        _workspace = gsl_spline_alloc(type, _dim);
        _accel = gsl_interp_accel_alloc();
        gsl_spline_init(_workspace, &x[0], &y[0], _dim);
    }

    inline Interpolation(const gsl_interp_type *type, const gsl::Vector &x, const gsl::Vector &y) {
        size_t _dim = x.size();
        _workspace = gsl_spline_alloc(type, _dim);
        _accel = gsl_interp_accel_alloc();
        gsl_spline_init(_workspace, x.begin(), y.begin(), _dim);
    }

    Interpolation(const Interpolation &obj) = delete;

    inline ~Interpolation() {
        if (_accel != nullptr) {
            gsl_interp_accel_free(_accel);
        }

        if (_workspace != nullptr) {
            gsl_spline_free(_workspace);
        }
    }

    Interpolation &operator=(const Interpolation &obj) = delete;

    inline double eval(double val) {
        double result; //y-Wert wird hier gespeichert
        //Rückgabewert enthält Fehlermeldung
        const int errorcode = gsl_spline_eval_e(_workspace,
                                                val, // x-Wert
                                                _accel,
                                                &result);
        //wenn der Wert val sich außerhalb der vorgegebenen Werte
        //befindet meldet die gsl einen Fehler
        Check::error_if(nmx_msg, errorcode == GSL_EDOM);
        return result;
    }

    inline double deriv(double val) {
        double result; //y-Wert
        const int errorcode = gsl_spline_eval_deriv_e(_workspace, //
                                                      val,
                                                      _accel,
                                                      &result);
        Check::error_if(nmx_msg, errorcode == GSL_EDOM);
        return result;
    }

    inline double deriv2(double val) {
        double result; //y-Wert
        const int errorcode = gsl_spline_eval_deriv2_e(_workspace, //
                                                       val,
                                                       _accel,
                                                       &result);
        Check::error_if(nmx_msg, errorcode == GSL_EDOM);
        return result;
    }

    inline double integral(double xmin, double xmax) {
        double result;
        const int errorcode = gsl_spline_eval_integ_e(_workspace, //
                                                      xmin,
                                                      xmax,
                                                      _accel,
                                                      &result);
        Check::error_if(nmx_msg, errorcode == GSL_EDOM);
        return result;
    }

    inline size_t size() const { return _workspace->size; }
};

} // namespace nmx::gsl