.. _program_listing_file_src_pdfs_PDFSegmentNormal.hpp:

Program Listing for File PDFSegmentNormal.hpp
=============================================

|exhale_lsh| :ref:`Return to documentation for file <file_src_pdfs_PDFSegmentNormal.hpp>` (``src/pdfs/PDFSegmentNormal.hpp``)

.. |exhale_lsh| unicode:: U+021B0 .. UPWARDS ARROW WITH TIP LEFTWARDS

.. code-block:: cpp

   
   #ifndef PDFSEGMENTNORMAL_HPP
   #define PDFSEGMENTNORMAL_HPP
   
   #include "../utils/RandomDist.hpp"
   #include "../utils/RngThread.hpp"
   #include "PDFCommons.hpp"
   #include "PDFSegment.hpp"
   #include <algorithm>
   #include <cmath>
   #include <fstream>
   #include <numbers>
   #include <toml.hpp>
   
   namespace pdfs {
   
       class PDFSegmentNormal : public PDFSegment {
       public:
   
           // Constructor and destructor
           PDFSegmentNormal(double sMin, double sMax, double mean, double stddev) :
               PDFSegment(sMin, sMax), 
               mean_(mean), 
               stddev_(stddev),
               norm_(std::numbers::sqrt2 * std::numbers::inv_sqrtpi /
                       stddev_ /
                       (std::erf((sMax_ - mean_) / (stddev_ * std::numbers::sqrt2)) -
                        std::erf((sMin_ - mean_) / (stddev_ * std::numbers::sqrt2)))
                   )
               { }
           PDFSegmentNormal(std::ifstream& file,
               FileFormats fmt,
               double &sMin,
               double &sMax,
               double &wgt);
           PDFSegmentNormal(toml::node_view<const toml::node> node,
               FileFormats fmt,
               double &sMin,
               double &sMax,
               double &wgt);
           PDFSegmentNormal(const PDFSegmentNormal&) = default;
           auto operator=(const PDFSegmentNormal&) -> PDFSegmentNormal& = default;
           PDFSegmentNormal(PDFSegmentNormal&&) = default;
           auto operator=(PDFSegmentNormal&&) -> PDFSegmentNormal& = default;
           ~PDFSegmentNormal() override = default;
   
           // Evaluation functions
           [[nodiscard]] auto operator()(double x) const -> double override {
               if (x < sMin_ || x > sMax_) {
                   return 0.0; // PDF is zero outside the segment
               }
               return norm_ * std::exp(-0.5 * std::pow((x - mean_) / stddev_, 2)); // PDF value at x
           }
           [[nodiscard]] auto expectationValue(const double a, const double b) const -> double override {
               if (a >= b || a > sMax_ || b < sMin_) {
                   return 0.0; // Invalid range for expectation value calculation
               }
               if (a == sMax_) {
                   return sMax_; // Handle edge cases
               }
               if (b == sMin_) {
                   return sMin_; // Handle edge cases
               }
               const double aClamped = std::max(a, sMin_);
               const double bClamped = std::min(b, sMax_);
               const double dxLoNorm = (aClamped - mean_) / (std::numbers::sqrt2 * stddev_);
               const double dxHiNorm = (bClamped - mean_) / (std::numbers::sqrt2 * stddev_);
               const double denom = std::erf(dxHiNorm) - std::erf(dxLoNorm);
               if (denom == 0.0) {
                   return 0.0; // Avoid division by zero if the PDF is negligible in the range
               }
               const double numLo = std::exp(-std::pow(dxLoNorm, 2));
               const double numHi = std::exp(-std::pow(dxHiNorm, 2));
               return mean_ + 
                   (stddev_ * std::numbers::sqrt2 * std::numbers::inv_sqrtpi *
                       (numLo - numHi) / denom);
           }
           [[nodiscard]] auto expectationValue() const -> double override {
               return expectationValue(sMin_, sMax_); // Expectation value over the full range of the segment
           }
           [[nodiscard]] auto integral(const double a, const double b) const -> double override {
               if (a >= b || a >= sMax_ || b <= sMin_) {
                   return 0.0; // Invalid range for integral calculation
               }
               const double aClamped = std::max(a, sMin_);
               const double bClamped = std::min(b, sMax_);
               const double dxLoNorm = (aClamped - mean_) / (std::numbers::sqrt2 * stddev_);
               const double dxHiNorm = (bClamped - mean_) / (std::numbers::sqrt2 * stddev_);
               return norm_ /
                   (std::numbers::sqrt2 * std::numbers::inv_sqrtpi) *
                   stddev_ *
                   (std::erf(dxHiNorm) - std::erf(dxLoNorm));
           }
   
           // Drawing functions
           [[nodiscard]] auto draw(const double a, const double b) const -> double override {
               const double aClamped = std::max(a, sMin_);
               const double bClamped = std::min(b, sMax_);
               if (aClamped >= bClamped) {
                   return 0.0; // Invalid range for drawing
               }
               utils::NormalDist dist(mean_, stddev_);
               double sample = NAN;
               while (true) {
                   sample = dist(utils::rng()());
                   if (sample >= aClamped && sample <= bClamped) { break; } // Rejection sampling
               }
               return sample;
           }
           [[nodiscard]] auto draw() const -> double override {
               return draw(sMin_, sMax_);
           }
           // Serialization
           void toToml(toml::table& tbl) const override;
   
       private:
           double mean_;   
           double stddev_; 
           double norm_;   
       };
   
   } // namespace pdfs
   
   #endif // PDFSEGMENTNORMAL_HPP