include/apfel/integrator2d.h

0001 //
0002 // APFEL++ 2017
0003 //
0004 // Author: Valerio Bertone: valerio.bertone@cern.ch
0005 //
0006
0007 #pragma once
0008
0009 #include "apfel/integrator.h"
0010
0011 namespace apfel
0012 {
0013   /**
0014    * @brief The Integrator2D class performs two-dimensional numerical
0015    * integrations using the Guassian quadrature.
0016    */
0017   class Integrator2D
0018   {
0019   public:
0020     /**
0021      * @name Constructors
0022      * List of constructors.
0023      */
0024     ///@{
0025     /**
0026      * @brief The Integrator constructor.
0027      * @param func: The function of two variables to be integrated
0028      * @param method: The integration method to be used (default: GAUSS_KRONROD)
0029      */
0030     Integrator2D(std::function<double(double const&, double const&)> const& func, Integrator::IntegrationMethod const& method = Integrator::GAUSS_KRONROD);
0031
0032     /**
0033      * @brief Function that integrates the integrand with a given
0034      * relative accuracy using the method defined in the constructor.
0035      * @param xmin: the lower bound integration bound for the first variable
0036      * @param xmax: the upper bound integration bound for the first variable
0037      * @param ymin: the lower bound integration bound for the second variable
0038      * @param ymax: the upper bound integration bound for the second variable
0039      * @param eps: the required relative accuracy
0040      * @return the value of the integral
0041      */
0042     double integrate(double const& xmin, double const& xmax, double const& ymin, double const& ymax, double const& eps) const;
0043
0044     /**
0045      * @brief Function that integrates the integrand with a using the
0046      * 8x8 and 16x16 Gauss-Legendre method.
0047      * @param xmin: the lower bound integration bound for the first variable
0048      * @param xmax: the upper bound integration bound for the first variable
0049      * @param ymin: the lower bound integration bound for the second variable
0050      * @param ymax: the upper bound integration bound for the second variable
0051      * @return a pair containing the value of the integral computed
0052      * with the 16x16 method and the relative difference w.r.t. the
0053      * 8x8 one.
0054      */
0055     std::pair<double, double> integrateGL(double const& xmin, double const& xmax, double const& ymin, double const& ymax) const;
0056
0057     /**
0058      * @brief Function that integrates the integrand with a using the
0059      * 7x7 and 15x15 Gauss-Kronrod method.
0060      * @param xmin: the lower bound integration bound for the first variable
0061      * @param xmax: the upper bound integration bound for the first variable
0062      * @param ymin: the lower bound integration bound for the second variable
0063      * @param ymax: the upper bound integration bound for the second variable
0064      * @return a pair containing the value of the integral computed
0065      * with the 15x15 method and the relative difference w.r.t. the
0066      * 7x7 one.
0067      */
0068     std::pair<double, double> integrateGK(double const& xmin, double const& xmax, double const& ymin, double const& ymax) const;
0069
0070     /**
0071      * @brief Function for the integrand.
0072      * @param x: the first variable
0073      * @param y: the second variable
0074      * @return the integrand evaluated at x and y
0075      */
0076     double integrand(double const& x, double const& y) const { return _func(x, y); };
0077
0078   private:
0079     std::function<double(double const&, double const&)> const _func;   //!< The integrand function
0080     Integrator::IntegrationMethod                       const _method; //!< The integration method
0081   };
0082 }