itkNormalVariateGenerator.h

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/*=========================================================================
 *
 *  Copyright NumFOCUS
 *
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *         https://www.apache.org/licenses/LICENSE-2.0.txt
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 *
 *=========================================================================*/
#ifndef itkNormalVariateGenerator_h
#define itkNormalVariateGenerator_h
 
#include "itkObjectFactory.h"
#include "itkRandomVariateGeneratorBase.h"
#include "ITKStatisticsExport.h"
 
namespace itk::Statistics
{
class ITKStatistics_EXPORT NormalVariateGenerator : public RandomVariateGeneratorBase
{
public:
  using Self = NormalVariateGenerator;
  using Superclass = RandomVariateGeneratorBase;
  using Pointer = SmartPointer<Self>;
  using ConstPointer = SmartPointer<const Self>;

  itkOverrideGetNameOfClassMacro(NormalVariateGenerator);

  itkNewMacro(Self);

  void
  Initialize(int randomSeed);

  double
  GetVariate() override;
 
protected:
  NormalVariateGenerator();
  ~NormalVariateGenerator() override;
  void
  PrintSelf(std::ostream & os, Indent indent) const override;

  double
  FastNorm();
 
private:
  static inline int
  SignedShiftXOR(int irs)
  {
    // shifting of signed integer gives undefined results, explicitly
    // cast to unsigned to get expected ( if two complement
    // representation ) results.
    auto uirs = static_cast<unsigned int>(irs);
    return static_cast<int>((irs <= 0) ? ((uirs << 1) ^ 333556017) : (uirs << 1));
  }
 
  double m_Scale{};
  double m_Rscale{};
  double m_Rcons{};
 
  static constexpr int m_ELEN{ 7 };
  // LEN must be 2 ** ELEN
  static constexpr int m_LEN{ 128 };
  static constexpr int m_LMASK{ 4 * (m_LEN - 1) };
  static constexpr int m_TLEN{ 8 * m_LEN };
 
  int   m_Gaussfaze{};
  int * m_Gausssave{};
 
  double m_GScale{};
 
  int    m_Vec1[m_TLEN]{};
  int    m_Nslew{};
  int    m_Irs{};
  int    m_Lseed{};
  double m_Chic1{};
  double m_Chic2{};
  double m_ActualRSD{};
}; // end of class
} // namespace itk::Statistics
#endif