/*=========================================================================
 *
 *  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.
 *
 *=========================================================================*/

#include "itkRegularStepGradientDescentOptimizer.h"

namespace itk
{
/**
 * Advance one Step following the gradient direction
 * This method will be overridden in non-vector spaces
 */
void
RegularStepGradientDescentOptimizer::StepAlongGradient(double factor, const DerivativeType & transformedGradient)
{
  itkDebugMacro("factor = " << factor << "  transformedGradient= " << transformedGradient);

  const unsigned int spaceDimension = m_CostFunction->GetNumberOfParameters();

  ParametersType newPosition(spaceDimension);
  ParametersType currentPosition = this->GetCurrentPosition();

  for (unsigned int j = 0; j < spaceDimension; ++j)
  {
    newPosition[j] = currentPosition[j] + transformedGradient[j] * factor;
  }

  itkDebugMacro("new position = " << newPosition);

  this->SetCurrentPosition(newPosition);
}
} // end namespace itk
