text: /*=========================================================================
   *
   *  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 itkCorrelationImageToImageMetricv4HelperThreader_h
  #define itkCorrelationImageToImageMetricv4HelperThreader_h
  
  #include "itkImageToImageMetricv4GetValueAndDerivativeThreader.h"
  
  namespace itk
  {
  
  /** \class CorrelationImageToImageMetricv4GetValueAndDerivativeThreader
   * \brief Helper class for CorrelationImageToImageMetricv4 \c
   * To compute the average pixel intensities of the fixed image and the moving image
   * on the sampled points or inside the virtual image region:
   * \f$ \bar f (CorrelationImageToImageMetricv4::m_AverageFix ) \f$
   * \f$ \bar m (CorrelationImageToImageMetricv4::m_AverageMov ) \f$
   *
   * \ingroup ITKMetricsv4
   */
  template <typename TDomainPartitioner, typename TImageToImageMetric, typename TCorrelationMetric>
  class ITK_TEMPLATE_EXPORT CorrelationImageToImageMetricv4HelperThreader
    : public ImageToImageMetricv4GetValueAndDerivativeThreader<TDomainPartitioner, TImageToImageMetric>
  {
  public:
    ITK_DISALLOW_COPY_AND_MOVE(CorrelationImageToImageMetricv4HelperThreader);
  
    /** Standard class type aliases. */
    using Self = CorrelationImageToImageMetricv4HelperThreader;
    using Superclass = ImageToImageMetricv4GetValueAndDerivativeThreader<TDomainPartitioner, TImageToImageMetric>;
    using Pointer = SmartPointer<Self>;
    using ConstPointer = SmartPointer<const Self>;
  
    itkTypeMacro(CorrelationImageToImageMetricv4HelperThreader, ImageToImageMetricv4GetValueAndDerivativeThreader);
  
    itkNewMacro(Self);
  
    using typename Superclass::DomainType;
    using typename Superclass::AssociateType;
  
    using ImageToImageMetricv4Type = typename Superclass::ImageToImageMetricv4Type;
    using typename Superclass::VirtualIndexType;
    using typename Superclass::VirtualPointType;
    using typename Superclass::FixedImagePointType;
    using typename Superclass::FixedImagePixelType;
    using typename Superclass::FixedImageGradientType;
    using typename Superclass::MovingImagePointType;
    using typename Superclass::MovingImagePixelType;
    using typename Superclass::MovingImageGradientType;
    using typename Superclass::MeasureType;
    using typename Superclass::DerivativeType;
    using typename Superclass::DerivativeValueType;
  
    using typename Superclass::InternalComputationValueType;
    using typename Superclass::NumberOfParametersType;
  
    using typename Superclass::FixedOutputPointType;
    using typename Superclass::MovingOutputPointType;
  
  protected:
    CorrelationImageToImageMetricv4HelperThreader();
    ~CorrelationImageToImageMetricv4HelperThreader() override;
  
    /** Overload: Resize and initialize per thread objects. */
    void
    BeforeThreadedExecution() override;
  
    /** Overload:
     * Collects the results from each thread and sums them.  Results are stored
     * in the enclosing class \c m_Value and \c m_DerivativeResult.  Behavior
     * depends on m_AverageValueAndDerivativeByNumberOfValuePoints,
     * m_NumberOfValidPoints, to average the value sum, and to average
     * derivative sums for global transforms only (i.e. transforms without local
     * support).  */
    void
    AfterThreadedExecution() override;
  
  
    /* Overload: don't need to compute the image gradients and store derivatives
     *
     * Method called by the threaders to process the given virtual point.  This
     * in turn calls \c TransformAndEvaluateFixedPoint, \c
     * TransformAndEvaluateMovingPoint, and \c ProcessPoint.
     */
    bool
    ProcessVirtualPoint(const VirtualIndexType & virtualIndex,
                        const VirtualPointType & virtualPoint,
                        const ThreadIdType       threadId) override;
  
  
    /**
     * Not using. All processing is done in ProcessVirtualPoint.
     */
    bool
    ProcessPoint(const VirtualIndexType &,
                 const VirtualPointType &,
                 const FixedImagePointType &,
                 const FixedImagePixelType &,
                 const FixedImageGradientType &,
                 const MovingImagePointType &,
                 const MovingImagePixelType &,
                 const MovingImageGradientType &,
                 MeasureType &,
                 DerivativeType &,
                 const ThreadIdType) const override
    {
      return false;
    }
  
  private:
    struct CorrelationMetricPerThreadStruct
    {
      InternalComputationValueType FixSum;
      InternalComputationValueType MovSum;
    };
    itkPadStruct(ITK_CACHE_LINE_ALIGNMENT, CorrelationMetricPerThreadStruct, PaddedCorrelationMetricPerThreadStruct);
    itkAlignedTypedef(ITK_CACHE_LINE_ALIGNMENT,
                      PaddedCorrelationMetricPerThreadStruct,
                      AlignedCorrelationMetricPerThreadStruct);
    /* per thread variables for correlation and its derivatives */
    mutable AlignedCorrelationMetricPerThreadStruct * m_CorrelationMetricPerThreadVariables;
  
    /** Internal pointer to the metric object in use by this threader.
     *  This will avoid costly dynamic casting in tight loops. */
    TCorrelationMetric * m_CorrelationAssociate;
  };
  
  } // end namespace itk
  
  #ifndef ITK_MANUAL_INSTANTIATION
  #  include "itkCorrelationImageToImageMetricv4HelperThreader.hxx"
  #endif
  
  #endif
  