text: /*=========================================================================
   *
   *  Copyright Insight Software Consortium
   *
   *  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
   *
   *         http://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 itkConjugateGradientLineSearchOptimizerv4_h
  #define itkConjugateGradientLineSearchOptimizerv4_h
  
  #include "itkGradientDescentLineSearchOptimizerv4.h"
  #include "itkOptimizerParameterScalesEstimator.h"
  #include "itkWindowConvergenceMonitoringFunction.h"
  
  namespace itk
  {
    /** \class ConjugateGradientLineSearchOptimizerv4Template
     *  \brief Conjugate gradient descent optimizer with a golden section line search for nonlinear optimization.
     *
     * ConjugateGradientLineSearchOptimizer implements a conjugate gradient descent optimizer
     * that is followed by a line search to find the best value for the learning rate.
     * At each iteration the current position is updated according to
     *
     * \f[
     *        p_{n+1} = p_n
     *                + \mbox{learningRateByGoldenSectionLineSearch}
     *                 \, d
     * \f]
     *
     * where d is defined as the Polak-Ribiere conjugate gradient.
     *
     * Options are identical to the superclass's.
     *
     * \ingroup ITKOptimizersv4
     */
  template<typename TInternalComputationValueType>
  class ITK_TEMPLATE_EXPORT ConjugateGradientLineSearchOptimizerv4Template
  : public GradientDescentLineSearchOptimizerv4Template<TInternalComputationValueType>
  {
  public:
    ITK_DISALLOW_COPY_AND_ASSIGN(ConjugateGradientLineSearchOptimizerv4Template);
  
    /** Standard class type aliases. */
    using Self = ConjugateGradientLineSearchOptimizerv4Template;
    using Superclass = GradientDescentLineSearchOptimizerv4Template<TInternalComputationValueType>;
    using Pointer = SmartPointer< Self >;
    using ConstPointer = SmartPointer< const Self >;
  
    /** Run-time type information (and related methods). */
    itkTypeMacro(ConjugateGradientLineSearchOptimizerv4Template, Superclass);
  
    /** New macro for creation of through a Smart Pointer */
    itkNewMacro(Self);
  
    /** It should be possible to derive the internal computation type from the class object. */
    using InternalComputationValueType = TInternalComputationValueType;
  
    /** Derivative type */
    using DerivativeType = typename Superclass::DerivativeType;
  
    /** Metric type over which this class is templated */
    using MeasureType = typename Superclass::MeasureType;
  
    /** Type for the convergence checker */
    using ConvergenceMonitoringType = itk::Function::WindowConvergenceMonitoringFunction<TInternalComputationValueType>;
  
    void StartOptimization( bool doOnlyInitialization = false ) override;
  
  protected:
  
    /** Advance one Step following the gradient direction.
     * Includes transform update. */
    void AdvanceOneStep() override;
  
    /** Default constructor */
    ConjugateGradientLineSearchOptimizerv4Template() = default;
  
    /** Destructor */
    ~ConjugateGradientLineSearchOptimizerv4Template() override = default;
  
    void PrintSelf( std::ostream & os, Indent indent ) const override;
  
  private:
  
    DerivativeType               m_LastGradient;
    DerivativeType               m_ConjugateGradient;
  
  };
  
  /** This helps to meet backward compatibility */
  using ConjugateGradientLineSearchOptimizerv4 = ConjugateGradientLineSearchOptimizerv4Template<double>;
  
  } // end namespace itk
  
  #ifndef ITK_MANUAL_INSTANTIATION
  #include "itkConjugateGradientLineSearchOptimizerv4.hxx"
  #endif
  
  #endif
  