vtkSMPMergePoints.h

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

  Program:   Visualization Toolkit
  Module:    vtkSMPMergePoints.h

  Copyright (c) Ken Martin, Will Schroeder, Bill Lorensen
  All rights reserved.
  See Copyright.txt or http://www.kitware.com/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 notice for more information.

=========================================================================*/
/**
 * @class   vtkSMPMergePoints
 * @brief   Class designed to help with merging of points in parallel
 *
 * vtkSMPMergePoints is a subclass of vtkMergePoints designed to help
 * with merging of points generated by using multiple locators in parallel.
 * Its main functionality is provided by the Merge function. It also
 * has a few additional convenience functions.
 * Merge is thread safe as long as no two threads are merging the same
 * bin. The common way of using vtkSMPMergePoints is:
 *  - Initialize with outLocator->InitializeMerge()
 *  - Allocate points with outLocator->GetPoints()->Resize(numPts) (numPts should be >= total number
 * of points)
 *  - Do bunch of merging with outLocator->Merge(inLocator[i], ...) (this can be done in parallel as
 * long as no two bins are done at the same time)
 *  - Fix the size of points with outLocator->FixSizeOfPointArray()
 */

#ifndef vtkSMPMergePoints_h
#define vtkSMPMergePoints_h

#include "vtkFiltersSMPModule.h" // For export macro
#include "vtkIdList.h"           // For inline functions
#include "vtkMergePoints.h"
#include "vtkType.h" // For vtkIdType

#include <atomic> // for std::atomic

class vtkPointData;

class VTKFILTERSSMP_EXPORT vtkSMPMergePoints : public vtkMergePoints
{
public:
  vtkTypeMacro(vtkSMPMergePoints, vtkMergePoints);
  static vtkSMPMergePoints* New();
  void PrintSelf(ostream& os, vtkIndent indent) override;

  /**
   * This should be called from 1 thread before any call to Merge.
   */
  void InitializeMerge();

  /**
   * Merge the points of one of the bins from the given locator to
   * the same bin of the current locator. Note that this requires that
   * the two locators have identical binning structures. This also
   * merges point data given in the inPD argument to the outPd.
   * Furthermore, it generates a map of the old ids of the input locator
   * to the new ids. This is stored in the idList argument. The map
   * is idList[oldId] = newId.
   */
  void Merge(vtkSMPMergePoints* locator, vtkIdType idx, vtkPointData* outPd, vtkPointData* inPd,
    vtkIdList* idList);

  /**
   * At the of the merge, this can be called to set the MaxId of the
   * points array to the maximum id in the locator. The current design
   * usage is as follows:
   * - Allocate points with points->Resize(numPts). NumPts should be >= total number of points
   * - Do bunch of merging with outLocator->Merge(inLocator[i], ...)
   * - Fix the size of points with outLocator->FixSizeOfPointArray()
   */
  void FixSizeOfPointArray();

  /**
   * Returns the biggest id in the locator.
   */
  vtkIdType GetMaxId() { return this->AtomicInsertionId - 1; }

  ///@{
  /**
   * Returns the number of points in a bin.
   */
  vtkIdType GetNumberOfIdsInBucket(vtkIdType idx)
  {
    if (!this->HashTable)
    {
      return 0;
    }
    vtkIdList* bucket = this->HashTable[idx];
    return bucket ? bucket->GetNumberOfIds() : 0;
  }
  ///@}

  /**
   * Returns the number of bins.
   */
  vtkIdType GetNumberOfBuckets() override { return this->NumberOfBuckets; }

protected:
  vtkSMPMergePoints();
  ~vtkSMPMergePoints() override;

  std::atomic<vtkIdType> AtomicInsertionId;

private:
  vtkSMPMergePoints(const vtkSMPMergePoints&) = delete;
  void operator=(const vtkSMPMergePoints&) = delete;
};

#endif // vtkSMPMergePoints_h