/*=========================================================================

  Program:   Insight Segmentation & Registration Toolkit
  Module:    $RCSfile: itkFiniteDifferenceSparseImageFilter.h,v $
  Language:  C++
  Date:      $Date: 2008-01-07 13:33:59 $
  Version:   $Revision: 1.6 $

  Copyright (c) Insight Software Consortium. All rights reserved.
  See ITKCopyright.txt or http://www.itk.org/HTML/Copyright.htm for details.

     This software is distributed WITHOUT ANY WARRANTY; without even 
     the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR 
     PURPOSE.  See the above copyright notices for more information.

     =========================================================================*/
#ifndef __itkFiniteDifferenceSparseImageFilter_h_
#define __itkFiniteDifferenceSparseImageFilter_h_ 

#include "itkFiniteDifferenceSparseImageFunction.h"
#include "itkFiniteDifferenceImageFilter.h"
#include "itkMultiThreader.h"
#include "itkSparseImage.h"

namespace itk {

/**
 * \class FiniteDifferenceSparseImageFilter
 *
 * \brief This class implements a multi-threaded base class for Image to
 * SparseImage finite difference processes.
 *
 * \par
 * This class implements a multi-threading mechanism for implementing finite
 * difference PDE's on sparse image types. The sparse image is a image of
 * pointers to node variables at valid pixel locations and null pointers at
 * others. The node variable type must have the following members: m_Index,
 * m_Data and m_Update.
 *
 * \par
 * This class also adds precomputing support to the finite difference image
 * filter scheme. This support can be used by certain filters to speed up the
 * processing. The m_PrecomputeFlag should be set to true to use this and the
 * Function object must provide a PrecomputeSparseUpdate method.
 *
 * \par INPUTS
 * The input to this filter is either a regular or sparse image. Subclasses
 * should provide a way of copying this information to the output sparse image
 * or initializing the output image nodes from the input image. 
 *
 * \par OUTPUTS
 * The output is a sparse image. The output will be in the m_Data members of
 * the nodes of the sparse image. 
 *
 * \par IMPORTANT
 * The output sparse image type must be templated with a node type that at
 * least has the following member variables: m_Index, m_Data and m_Update. 
 */

template <class TInputImageType, class TSparseOutputImageType>
class FiniteDifferenceSparseImageFilter
  : public FiniteDifferenceImageFilter <TInputImageType,
                                        TSparseOutputImageType>
{
public:
  /** Standard class typedef */
  typedef FiniteDifferenceSparseImageFilter Self;
  typedef FiniteDifferenceImageFilter<TInputImageType,
                                      TSparseOutputImageType> Superclass;
  typedef SmartPointer<Self>  Pointer;
  typedef SmartPointer<const Self>  ConstPointer;

  /** Run-time type information (and related methods) */
  itkTypeMacro(FiniteDifferenceSparseImageFilter, FiniteDifferenceImageFilter);

  /**Typedefs from the superclass */
  typedef typename Superclass::InputImageType  InputImageType;
  typedef typename Superclass::OutputImageType SparseOutputImageType;
  typedef typename Superclass::PixelType       PixelType; 
  typedef typename Superclass::TimeStepType    TimeStepType;
  typedef typename Superclass::FiniteDifferenceFunctionType
  FiniteDifferenceFunctionType;
  // the PixelType is from output image; therefore, it is a pointer
  
  /** Dimensionality of input and output data is assumed to be the same.
   * It is inherited from the superclass. */
  itkStaticConstMacro(ImageDimension, unsigned int,Superclass::ImageDimension);

  /** Typedefs from the sparse output image type. */
  typedef typename SparseOutputImageType::IndexType    IndexType;
  typedef typename SparseOutputImageType::SizeType     SizeType;
  typedef typename SparseOutputImageType::NodeType     OutputNodeType;
  typedef typename SparseOutputImageType::NodeListType NodeListType;

  /** The type for the data variable of OutputNodeType. */
  typedef typename OutputNodeType::NodeDataType NodeDataType;

  /** The basic scalar variable type used in OutputNodeType. Expected to be
   * float or double. If NodeDataType is a scalar, then this is the same type as
   * that. */
  typedef typename OutputNodeType::NodeValueType NodeValueType;

  /** The sparse image finite difference function type used in this class. */
  typedef FiniteDifferenceSparseImageFunction <SparseOutputImageType>
  SparseFunctionType;

  /** Sets the function object that will be called for computing updates. */
  void SetSparseFunction( SparseFunctionType *sf );

  itkSetMacro(PrecomputeFlag, bool);
  itkGetMacro(PrecomputeFlag, bool);

protected:
  FiniteDifferenceSparseImageFilter();
  ~FiniteDifferenceSparseImageFilter() {}
  void PrintSelf(std::ostream& os, Indent indent) const;

  /** This method splits the active pixels of the sparse image into equal size
   *  lists for multi-threading. These lists remain constant throughout the
   *  operation of this filter.*/
  virtual void Initialize();
  
  /** This class does not use AllocateUpdateBuffer to allocate memory for its 
   *  narrow band. All memory is handled through the SparseImage class. */
  virtual void AllocateUpdateBuffer() {};

  /** This function can be used to implements constraints on the range of data
   * values. Default is no constraint. */
  virtual NodeDataType DataConstraint( const NodeDataType &data ) const 
  { return data; }
  
private:
  /** The type of region used in multithreading. */
  struct ThreadRegionType 
  {
    // this is the first element
    typename NodeListType::Iterator first;
    // this is one past the last element
    typename NodeListType::Iterator last;  
  };

protected:
  /** This function returns a single region for use in multi-threading. */
  int GetSplitRegion( int i, int num, ThreadRegionType &splitRegion );
  
  /** This function updates the m_Data variable in the output image nodes using
      the update values computed by CalculateChange. */
  virtual void ApplyUpdate( TimeStepType dt );
  
  /** Multi-threaded implementation of ApplyUpdate. */
  static ITK_THREAD_RETURN_TYPE ApplyUpdateThreaderCallback( void *arg );
  virtual void ThreadedApplyUpdate(TimeStepType dt,
                                   const ThreadRegionType &regionToProcess,
                                   int threadId);

  /** This method computes changes to the output image using the
      ComputeSparseUpdate method in the Sparse Function object. */
  virtual TimeStepType CalculateChange();

  /** Multuthreaded implementation of CalculateChange */
  static ITK_THREAD_RETURN_TYPE CalculateChangeThreaderCallback( void *arg );
  virtual TimeStepType ThreadedCalculateChange
  (const ThreadRegionType &regionToProcess, int threadId);

  /** This method provides a means of performing a first pass for computing the
   *  change and storing intermediate values that will then be used by
   *  CalculateChange. This can be used to speed up certain update rules. */
  virtual void PrecalculateChange();

  /** Multithreaded implementation of PrecalculateChange */
  static ITK_THREAD_RETURN_TYPE PrecalculateChangeThreaderCallback( void *arg );
  virtual void ThreadedPrecalculateChange
  (const ThreadRegionType &regionToProcess, int threadId);

  /** Structure for passing information into static callback methods.
   *  Used in  the subclasses' threading mechanisms. */
  struct FDThreadStruct
  {
    FiniteDifferenceSparseImageFilter *Filter;
    TimeStepType TimeStep;
    TimeStepType *TimeStepList;
    bool *ValidTimeStepList;
  };
  
private:
  /** Flag to let the class know whether or not to call PrecalculateChange. */
  bool m_PrecomputeFlag;

  /** The Sparse function type. */
  SparseFunctionType *m_SparseFunction;

  /** A list of subregions of the active set of pixels in the sparse image
      which are passed to each thread for parallel processing. */
  typename NodeListType::RegionListType m_RegionList;

  FiniteDifferenceSparseImageFilter(const Self&); //purposely not implemented
  void operator=(const Self&); //purposely not implemented
};

} // end namespace itk

#ifndef ITK_MANUAL_INSTANTIATION
#include "itkFiniteDifferenceSparseImageFilter.txx"
#endif

#endif