spline/spline.cpp at submodule · nd-nuclear-theory/spline · GitHub

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/*
  Abraham Flores
  Notre Dame Physics REU 2016
  6/9/2016
  Language C++


  SPLINE INTERPOLATION:
  *see header for details
  */
#include <cstdlib>
#include <cstdio>
#include <cmath>
#include <utility>
#include <gsl/gsl_errno.h>
#include <gsl/gsl_spline.h>
#include <gsl/gsl_sf_laguerre.h>
#include "spline.h"
/*
  Enter function required for evaluation here:
*/
namespace spline{
  double CubicIntegrate(const double x[], const double y[], int n){

    gsl_interp_accel *acc = gsl_interp_accel_alloc (); //Returns pointer to accelerator object, tracks state of lookups
    const gsl_interp_type *t = gsl_interp_cspline;//Cubic Spline with periodic boundary conditions, result: piecewise cubic on each interval
    gsl_spline *spline = gsl_spline_alloc (t,n);//Returns a pointer to a newly allocated interpolation object of type t for n size data-points

    gsl_spline_init(spline, x, y, n);

    double integral_value;
    integral_value = gsl_spline_eval_integ(spline,x[0],x[n-1],acc);//Evaluate Integral

    gsl_spline_free (spline);
    gsl_interp_accel_free (acc);

    return integral_value;
  }

#ifndef SPLINE_NO_FANCY_INTEGRATION
  double AkimaIntegrate(double *x,double *y, int n){

    gsl_interp_accel *acc = gsl_interp_accel_alloc (); //Returns pointer to accelerator object, tracks state of lookups
    const gsl_interp_type *t = gsl_interp_akima;//Cubic Spline with periodic boundary conditions, result: piecewise cubic on each interval
    gsl_spline *spline = gsl_spline_alloc (t,n);//Returns a pointer to a newly allocated interpolation object of type t for n size data-points

    gsl_spline_init(spline, x, y, n);

    double integral_value;
    integral_value = gsl_spline_eval_integ(spline,x[0],x[n-1],acc);//Evaluate Integral

    gsl_spline_free (spline);
    gsl_interp_accel_free (acc);

    return integral_value;
  }

  double SteffenIntegrate(double *x,double *y, int n){

    gsl_interp_accel *acc = gsl_interp_accel_alloc (); //Returns pointer to accelerator object, tracks state of lookups
    const gsl_interp_type *t = gsl_interp_steffen;//Cubic Spline with periodic boundary conditions, result: piecewise cubic on each interval
    gsl_spline *spline = gsl_spline_alloc (t,n);//Returns a pointer to a newly allocated interpolation object of type t for n size data-points

    gsl_spline_init(spline, x, y, n);

    double integral_value;
    integral_value = gsl_spline_eval_integ(spline,x[0],x[n-1],acc);//Evaluate Integral

    gsl_spline_free (spline);
    gsl_interp_accel_free (acc);

    return integral_value;
  }
#endif
}