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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 itkCorrelationImageToImageMetricv4GetValueAndDerivativeThreader_hxx
#define itkCorrelationImageToImageMetricv4GetValueAndDerivativeThreader_hxx

#include "itkMakeUniqueForOverwrite.h"


namespace itk
{

template <typename TDomainPartitioner, typename TImageToImageMetric, typename TCorrelationMetric>
CorrelationImageToImageMetricv4GetValueAndDerivativeThreader<
  TDomainPartitioner,
  TImageToImageMetric,
  TCorrelationMetric>::CorrelationImageToImageMetricv4GetValueAndDerivativeThreader()
  : m_CorrelationMetricValueDerivativePerThreadVariables(nullptr)
  , m_CorrelationAssociate(nullptr)
{}


template <typename TDomainPartitioner, typename TImageToImageMetric, typename TCorrelationMetric>
void
CorrelationImageToImageMetricv4GetValueAndDerivativeThreader<TDomainPartitioner,
                                                             TImageToImageMetric,
                                                             TCorrelationMetric>::BeforeThreadedExecution()
{
  Superclass::BeforeThreadedExecution();

  /* Store the casted pointer to avoid dynamic casting in tight loops. */
  this->m_CorrelationAssociate = dynamic_cast<TCorrelationMetric *>(this->m_Associate);
  if (this->m_CorrelationAssociate == nullptr)
  {
    itkExceptionMacro("Dynamic casting of associate pointer failed.");
  }

  /* This size always comes from the moving image */
  const NumberOfParametersType globalDerivativeSize = this->GetCachedNumberOfParameters();

  const ThreadIdType numWorkUnitsUsed = this->GetNumberOfWorkUnitsUsed();
  // set size
  m_CorrelationMetricValueDerivativePerThreadVariables =
    make_unique_for_overwrite<AlignedCorrelationMetricValueDerivativePerThreadStruct[]>(numWorkUnitsUsed);
  for (ThreadIdType i = 0; i < numWorkUnitsUsed; ++i)
  {
    this->m_CorrelationMetricValueDerivativePerThreadVariables[i].fdm.SetSize(globalDerivativeSize);
    this->m_CorrelationMetricValueDerivativePerThreadVariables[i].mdm.SetSize(globalDerivativeSize);
  }

  //---------------------------------------------------------------
  // Set initial values.
  for (ThreadIdType i = 0; i < numWorkUnitsUsed; ++i)
  {
    m_CorrelationMetricValueDerivativePerThreadVariables[i].fm = InternalComputationValueType{};
    m_CorrelationMetricValueDerivativePerThreadVariables[i].f2 = InternalComputationValueType{};
    m_CorrelationMetricValueDerivativePerThreadVariables[i].m2 = InternalComputationValueType{};
    m_CorrelationMetricValueDerivativePerThreadVariables[i].f = InternalComputationValueType{};
    m_CorrelationMetricValueDerivativePerThreadVariables[i].m = InternalComputationValueType{};

    this->m_CorrelationMetricValueDerivativePerThreadVariables[i].mdm.Fill(DerivativeValueType{});
    this->m_CorrelationMetricValueDerivativePerThreadVariables[i].fdm.Fill(DerivativeValueType{});
  }
}

template <typename TDomainPartitioner, typename TImageToImageMetric, typename TCorrelationMetric>
void
CorrelationImageToImageMetricv4GetValueAndDerivativeThreader<TDomainPartitioner,
                                                             TImageToImageMetric,
                                                             TCorrelationMetric>::AfterThreadedExecution()
{

  /* This size always comes from the moving image */
  const NumberOfParametersType globalDerivativeSize = this->GetCachedNumberOfParameters();
  const ThreadIdType           numWorkUnitsUsed = this->GetNumberOfWorkUnitsUsed();

  /* Store the number of valid points the enclosing class \c
   * m_NumberOfValidPoints by collecting the valid points per thread. */
  this->m_CorrelationAssociate->m_NumberOfValidPoints = SizeValueType{};
  for (ThreadIdType i = 0; i < numWorkUnitsUsed; ++i)
  {
    this->m_CorrelationAssociate->m_NumberOfValidPoints +=
      this->m_GetValueAndDerivativePerThreadVariables[i].NumberOfValidPoints;
  }

  /* Check the number of valid points meets the default minimum.
   * If not, parameters will hold default return values for this case */
  if (!this->m_CorrelationAssociate->VerifyNumberOfValidPoints(this->m_CorrelationAssociate->m_Value,
                                                               *(this->m_CorrelationAssociate->m_DerivativeResult)))
  {
    return;
  }

  itkDebugMacro(
    "CorrelationImageToImageMetricv4: NumberOfValidPoints: " << this->m_CorrelationAssociate->m_NumberOfValidPoints);

  /* Accumulate the metric value from threads and store */
  this->m_CorrelationAssociate->m_Value = InternalComputationValueType{};
  InternalComputationValueType fm{};
  InternalComputationValueType f2{};
  InternalComputationValueType m2{};
  for (ThreadIdType threadId = 0; threadId < numWorkUnitsUsed; ++threadId)
  {
    fm += this->m_CorrelationMetricValueDerivativePerThreadVariables[threadId].fm;
    m2 += this->m_CorrelationMetricValueDerivativePerThreadVariables[threadId].m2;
    f2 += this->m_CorrelationMetricValueDerivativePerThreadVariables[threadId].f2;
  }

  InternalComputationValueType m2f2 = m2 * f2;
  if (m2f2 <= NumericTraits<InternalComputationValueType>::epsilon())
  {
    itkDebugMacro("CorrelationImageToImageMetricv4: m2 * f2 <= epsilon");
    return;
  }

  this->m_CorrelationAssociate->m_Value = -1.0 * fm * fm / (m2f2);

  /* For global transforms, compute the derivatives by combining values from each region. */
  if (this->m_CorrelationAssociate->GetComputeDerivative())
  {
    DerivativeType fdm, mdm;
    fdm.SetSize(globalDerivativeSize);
    mdm.SetSize(globalDerivativeSize);

    fdm.Fill(DerivativeValueType{});
    mdm.Fill(DerivativeValueType{});

    const auto fc = static_cast<InternalComputationValueType>(2.0);

    for (ThreadIdType i = 0; i < numWorkUnitsUsed; ++i)
    {
      fdm += this->m_CorrelationMetricValueDerivativePerThreadVariables[i].fdm;
      mdm += this->m_CorrelationMetricValueDerivativePerThreadVariables[i].mdm;
    }

    /** There should be a minus sign of \frac{d}{dp} mathematically, which
     *  is not in the implementation to match the requirement of the metricv4
     *  optimization framework.
     *
     *  We use += instead of assignment here because for multi-variate vector,
     *  we will want to always add to the values in m_DerivativeResult so they
     *  can be efficiently accumulated between multiple metrics.
     */
    *(this->m_CorrelationAssociate->m_DerivativeResult) += fc * fm / (f2 * m2) * (fdm - fm / m2 * mdm);
  }
}

template <typename TDomainPartitioner, typename TImageToImageMetric, typename TCorrelationMetric>
bool
CorrelationImageToImageMetricv4GetValueAndDerivativeThreader<
  TDomainPartitioner,
  TImageToImageMetric,
  TCorrelationMetric>::ProcessVirtualPoint(const VirtualIndexType & virtualIndex,
                                           const VirtualPointType & virtualPoint,
                                           const ThreadIdType       threadId)
{
  FixedImagePointType     mappedFixedPoint;
  FixedImagePixelType     mappedFixedPixelValue;
  FixedImageGradientType  mappedFixedImageGradient;
  MovingImagePointType    mappedMovingPoint;
  MovingImagePixelType    mappedMovingPixelValue;
  MovingImageGradientType mappedMovingImageGradient;
  bool                    pointIsValid = false;
  MeasureType             metricValueResult;

  /* Transform the point into fixed and moving spaces, and evaluate.
   * Different behavior with pre-warping enabled is handled transparently.
   * Do this in a try block to catch exceptions and print more useful info
   * then we otherwise get when exceptions are caught in MultiThreaderBase. */
  try
  {
    pointIsValid = this->m_CorrelationAssociate->TransformAndEvaluateFixedPoint(
      virtualPoint, mappedFixedPoint, mappedFixedPixelValue);
    if (pointIsValid && this->m_CorrelationAssociate->GetComputeDerivative() &&
        this->m_CorrelationAssociate->GetGradientSourceIncludesFixed())
    {
      this->m_CorrelationAssociate->ComputeFixedImageGradientAtPoint(mappedFixedPoint, mappedFixedImageGradient);
    }
  }
  catch (const ExceptionObject & exc)
  {
    // NOTE: there must be a cleaner way to do this:
    std::string msg("Caught exception: \n");
    msg += exc.what();
    ExceptionObject err(__FILE__, __LINE__, msg);
    throw err;
  }
  if (!pointIsValid)
  {
    return pointIsValid;
  }

  try
  {
    pointIsValid = this->m_CorrelationAssociate->TransformAndEvaluateMovingPoint(
      virtualPoint, mappedMovingPoint, mappedMovingPixelValue);
    if (pointIsValid && this->m_CorrelationAssociate->GetComputeDerivative() &&
        this->m_CorrelationAssociate->GetGradientSourceIncludesMoving())
    {
      this->m_CorrelationAssociate->ComputeMovingImageGradientAtPoint(mappedMovingPoint, mappedMovingImageGradient);
    }
  }
  catch (const ExceptionObject & exc)
  {
    std::string msg("Caught exception: \n");
    msg += exc.what();
    ExceptionObject err(__FILE__, __LINE__, msg);
    throw err;
  }
  if (!pointIsValid)
  {
    return pointIsValid;
  }

  /* Call the user method in derived classes to do the specific
   * calculations for value and derivative. */
  try
  {
    pointIsValid = this->ProcessPoint(virtualIndex,
                                      virtualPoint,
                                      mappedFixedPoint,
                                      mappedFixedPixelValue,
                                      mappedFixedImageGradient,
                                      mappedMovingPoint,
                                      mappedMovingPixelValue,
                                      mappedMovingImageGradient,
                                      metricValueResult,
                                      this->m_GetValueAndDerivativePerThreadVariables[threadId].LocalDerivatives,
                                      threadId);
  }
  catch (const ExceptionObject & exc)
  {
    // NOTE: there must be a cleaner way to do this:
    std::string msg("Exception in GetValueAndDerivativeProcessPoint:\n");
    msg += exc.what();
    ExceptionObject err(__FILE__, __LINE__, msg);
    throw err;
  }
  if (pointIsValid)
  {
    this->m_GetValueAndDerivativePerThreadVariables[threadId].NumberOfValidPoints++;
  }

  return pointIsValid;
}

template <typename TDomainPartitioner, typename TImageToImageMetric, typename TCorrelationMetric>
bool
CorrelationImageToImageMetricv4GetValueAndDerivativeThreader<
  TDomainPartitioner,
  TImageToImageMetric,
  TCorrelationMetric>::ProcessPoint(const VirtualIndexType &        itkNotUsed(virtualIndex),
                                    const VirtualPointType &        virtualPoint,
                                    const FixedImagePointType &     itkNotUsed(mappedFixedPoint),
                                    const FixedImagePixelType &     fixedImageValue,
                                    const FixedImageGradientType &  itkNotUsed(mappedFixedImageGradient),
                                    const MovingImagePointType &    itkNotUsed(mappedMovingPoint),
                                    const MovingImagePixelType &    movingImageValue,
                                    const MovingImageGradientType & movingImageGradient,
                                    MeasureType &                   itkNotUsed(metricValueReturn),
                                    DerivativeType &                itkNotUsed(localDerivativeReturn),
                                    const ThreadIdType              threadId) const
{

  /*
   * metricValueReturn and localDerivativeReturn will not be computed here.
   * Instead, m_CorrelationMetricValueDerivativePerThreadVariables will store temporary results for each thread
   * and finally compute metric and derivative in overloaded AfterThreadedExecution
   */

  /* subtract the average of pixels (computed during InitializeIteration) */
  const InternalComputationValueType & f1 = fixedImageValue - this->m_CorrelationAssociate->m_AverageFix;
  const InternalComputationValueType & m1 = movingImageValue - this->m_CorrelationAssociate->m_AverageMov;

  AlignedCorrelationMetricValueDerivativePerThreadStruct & cumsum =
    this->m_CorrelationMetricValueDerivativePerThreadVariables[threadId];
  cumsum.f += f1;
  cumsum.m += m1;
  cumsum.f2 += f1 * f1;
  cumsum.m2 += m1 * m1;
  cumsum.fm += f1 * m1;

  if (this->m_CorrelationAssociate->GetComputeDerivative())
  {
    /* Use a pre-allocated jacobian object for efficiency */
    using JacobianReferenceType = typename TImageToImageMetric::JacobianType &;
    JacobianReferenceType jacobian = this->m_GetValueAndDerivativePerThreadVariables[threadId].MovingTransformJacobian;
    JacobianReferenceType jacobianPositional =
      this->m_GetValueAndDerivativePerThreadVariables[threadId].MovingTransformJacobianPositional;

    /** For dense transforms, this returns identity */
    this->m_CorrelationAssociate->GetMovingTransform()->ComputeJacobianWithRespectToParametersCachedTemporaries(
      virtualPoint, jacobian, jacobianPositional);

    for (unsigned int par = 0; par < this->m_CorrelationAssociate->GetNumberOfLocalParameters(); ++par)
    {
      InternalComputationValueType sum{};
      for (SizeValueType dim = 0; dim < ImageToImageMetricv4Type::MovingImageDimension; ++dim)
      {
        sum += movingImageGradient[dim] * jacobian(dim, par);
      }

      cumsum.fdm[par] += f1 * sum;
      cumsum.mdm[par] += m1 * sum;
    }
  }

  return true;
}

} // end namespace itk

#endif
