include/G4HepEm/G4HepEmInitUtils.hh

0001
0002 #ifndef G4HepEmInitUtils_HH
0003 #define G4HepEmInitUtils_HH
0004
0005 //
0006 // Utility methods used during the initialisation.
0007 //
0008
0009 class G4HepEmInitUtils {
0010 public:
0011   G4HepEmInitUtils() = delete;
0012
0013   // Fills the input vector arguments with `npoints` GL integral abscissas and
0014   // weights values (on [0,1] by default)
0015   static void GLIntegral(int npoints, double* abscissas, double* weights, double min=0.0, double max=1.0);
0016
0017
0018
0019   // receives `npoint` x,y data arrays and fills the `secderiv` array with the
0020   // second derivatives that can be used for a spline interpolation
0021   static void   PrepareSpline(int npoint, double* xdata, double* ydata, double* secderiv);
0022
0023   // same as above, but both the ydata and second derivatives are stored in the
0024   // ydata array (compact [...,y_i, sd_i, y_{i+1}, sd_{i+1},...] with 2x`npoint`)
0025   static void   PrepareSpline(int npoint, double* xdata, double* ydata);
0026
0027
0028   // get spline interpolation over a log-spaced xgrid previously prepared by
0029   // PrepareSpline (separate storrage of ydata and second deriavtive)
0030   // use the improved, robust spline interpolation that I put in G4 10.6
0031   static double GetSplineLog(int ndata, double* xdata, double* ydata, double* secderiv, double x, double logx, double logxmin, double invLDBin);
0032
0033   // get spline interpolation over a log-spaced xgrid previously prepared by
0034   // PrepareSpline (compact storrage of ydata and second deriavtive in ydata)
0035   // use the improved, robust spline interpolation that I put in G4 10.6
0036   static double GetSplineLog(int ndata, double* xdata, double* ydata, double x, double logx, double logxmin, double invLDBin);
0037
0038   // get spline interpolation over a log-spaced xgrid previously prepared by
0039   // PrepareSpline (compact storrage of xdata, ydata and second deriavtive in data)
0040   // use the improved, robust spline interpolation that I put in G4 10.6
0041   static double GetSplineLog(int ndata, double* data, double x, double logx, double logxmin, double invLDBin);
0042
0043
0044   // get spline interpolation over any xgrid: idx = i such  xdata[i] <= x < xdata[i+1]
0045   // and x >= xdata[0] and x<xdata[ndata-1]
0046   // PrepareSpline (separate storrage of ydata and second deriavtive)
0047   // use the improved, robust spline interpolation that I put in G4 10.6
0048   static double GetSpline(double* xdata, double* ydata, double* secderiv, double x, int idx, int step=1);
0049
0050   // get spline interpolation if it was prepared with compact storrage of ydata
0051   // and second deriavtive in ydata
0052   // use the improved, robust spline interpolation that I put in G4 10.6
0053   static double GetSpline(double* xdata, double* ydata, double x, int idx);
0054
0055   // get spline interpolation if it was prepared with compact storrage of xdata,
0056   // ydata and second deriavtive in data
0057   static double GetSpline(double* data, double x, int idx);
0058
0059
0060   // finds the lower index of the x-bin in an ordered, increasing x-grid such
0061   // that x[i] <= x < x[i+1]
0062   static int    FindLowerBinIndex(double* xdata, int num, double x, int step=1);
0063
0064    /**
0065    * Fills a pre-existing array with doubles uniformly spaced in log(x)
0066    *
0067    * @param[in] emin Inclusive lower bound
0068    * @param[in] emax Inclusive upper bound
0069    * @param[in] npoints Number of points in array, including upper/lower bounds
0070    * @param[out] log_min_value Logarithm of @param emin
0071    * @param[out] inverse_log_delta Inverse of logarithmic spacing between points
0072    * @param[out] grid pointer to array
0073    *
0074    * @pre @param grid must not by `nullptr` and have capacity for at least @param npoints `double`s
0075    * @post The [0,npoints-1] elements of @param grid will contain the data
0076    */
0077   static void FillLogarithmicGrid(const double emin, const double emax, const int npoints,
0078                                   double& log_min_value, double& inverse_log_delta, double* grid);
0079 };
0080
0081 #endif //  G4HepEmInitUtils_HH