vtkMaskPoints.cxx

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

  Program:   Visualization Toolkit
  Module:    vtkMaskPoints.cxx

  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.

=========================================================================*/
#include "vtkMaskPoints.h"

#include "vtkCellArray.h"
#include "vtkDataSet.h"
#include "vtkInformation.h"
#include "vtkInformationVector.h"
#include "vtkMath.h"
#include "vtkObjectFactory.h"
#include "vtkPointData.h"
#include "vtkPoints.h"
#include "vtkPolyData.h"
#include <stdlib.h>

vtkStandardNewMacro(vtkMaskPoints);

//----------------------------------------------------------------------------
vtkMaskPoints::vtkMaskPoints()
{
  this->OnRatio = 2;
  this->Offset = 0;
  this->RandomMode = 0;
  this->MaximumNumberOfPoints = VTK_ID_MAX;
  this->GenerateVertices = 0;
  this->SingleVertexPerCell = 0;
  this->RandomModeType = 0;
  this->ProportionalMaximumNumberOfPoints = 0;
  this->OutputPointsPrecision = DEFAULT_PRECISION;
}

inline double d_rand()
{
  return rand() / (double)((unsigned long)RAND_MAX + 1);
}

inline void SwapPoint(vtkPoints* points,
                      vtkPointData* data,
                      vtkPointData* temp,
                      vtkIdType a, vtkIdType b)
{
  double ta[3];

  // a -> temp
  points->GetPoint(a, ta);
  temp->CopyData(data, a, 0);

  // b -> a
  points->SetPoint(a, points->GetPoint(b));
  data->CopyData(data, b, a);

  // temp -> b
  points->SetPoint(b, ta);
  data->CopyData(temp, 0, b);
}

// AKA select, quickselect, nth_element:
// this is average case linear, worse case quadratic implementation
// (i.e., just like quicksort) -- there is the median of 5 or
// median of medians algorithm, but I'm too lazy to implement it
static void QuickSelect(vtkPoints* points,
                        vtkPointData* data,
                        vtkPointData* temp,
                        vtkIdType start,
                        vtkIdType end,
                        vtkIdType nth,
                        int axis)
{
  // base case
  if(end - start < 2)
    {
    return;
    }

  // pick a pivot
  vtkIdType pivot = (vtkIdType)(rand() % (end - start)) + start;
  double value = points->GetPoint(pivot)[axis];

  // swap the pivot to end
  end = end - 1;
  SwapPoint(points, data, temp, pivot, end);

  // partition by pivot
  vtkIdType left = start;
  int allequal = 1;
  for(vtkIdType i = start; i < end; i = i + 1)
    {
    allequal = allequal && (points->GetPoint(i)[axis] == value);

    if(points->GetPoint(i)[axis] < value)
      {
      SwapPoint(points, data, temp, i, left);
      left = left + 1;
      }
    }

  // swap pivot to correct position
  SwapPoint(points, data, temp, left, end);
  end = end + 1;

  // recurse if we didn't find it
  if((left != nth) && !allequal)
    {
    if(left < nth) // it's in the right half
      {
      QuickSelect(points, data, temp, left, end, nth, axis);
      }
    else // it's in the left half
      {
      QuickSelect(points, data, temp, start, left, nth, axis);
      }
    }
}

// divide the data into sampling strata and randomly sample it
// (one sample per stratum)
static void SortAndSample(vtkPoints* points, vtkPointData* data,
                          vtkPointData* temp,
                          vtkIdType start, vtkIdType end,
                          vtkIdType size, int depth)
{
  // if size >= end - start return them all
  if(size >= (end - start))
    {
    return;
    }

  // if size == 1 return it (get one sample from a stratum)
  if(size < 2)
    {
    vtkIdType pick = (vtkIdType)(rand() % (end - start)) + start;
    SwapPoint(points, data, temp, start, pick);
    return;
    }

  // do median split of left and right (AKA select, quickselect, nth_element)
  vtkIdType half = start + (end - start) / 2;
  int bigger = 0;
  // randomly make one side bigger if it doesn't split evenly
  if((end - start) % 2)
    {
      if(rand() % 2)
        {
          bigger = 1;
          half = half + 1;
        }
      else
        {
          bigger = 2;
        }
    }

  QuickSelect(points, data, temp, start, end, half, depth % 3);

  // sample the left and right halves
  vtkIdType leftsize, rightsize;
  if(size % 2)
    {
      if(bigger)
        {
          if(bigger == 1)
            {
              leftsize = size / 2 + 1;
              rightsize = size / 2;
            }
          else
            {
              leftsize = size / 2;
              rightsize = size / 2 + 1;
            }
        }
      // randomly make a sample size bigger if it doesn't split evenly
      else if(rand() % 2)
        {
          leftsize = size / 2 + 1;
          rightsize = size / 2;
        }
      else
        {
          leftsize = size / 2;
          rightsize = size / 2 + 1;
        }
    }
  else
    {
      leftsize = size / 2;
      rightsize = size / 2;
    }

  // get samples from children
  SortAndSample(points, data, temp, start, half, leftsize, depth + 1);
  SortAndSample(points, data, temp, half, end, rightsize, depth + 1);

  // combine the two halves
  for(vtkIdType i = 0; i < rightsize; i = i + 1)
    {
      SwapPoint(points, data, temp, start + leftsize + i, half + i);
    }
}


unsigned long vtkMaskPoints::GetLocalSampleSize(vtkIdType numPts, int np)
{
  if(np > 1)
    {
    // send number of points to process 0
    unsigned long send = (unsigned long)numPts;
    unsigned long* recv = new unsigned long[np];
    this->InternalGather(&send, recv, 1, 0);

    // process 0 figures it out
    unsigned long* dist = new unsigned long[np];
    if(this->InternalGetLocalProcessId() == 0)
      {
      // sum them
      unsigned long total = 0;
      for(int i = 0; i < np; i = i + 1)
        {
        total = total + recv[i];
        }

      // if it's greater than 0
      if(total > 0)
        {
        // each process gets a proportional fraction
        vtkIdType left = this->MaximumNumberOfPoints;
        double ratio = this->MaximumNumberOfPoints / (double)total;
        for(int i = 0; i < np; i = i + 1)
          {
          dist[i] = (unsigned long)(recv[i] * ratio);
          left = left - dist[i];
          }

        // if it didn't evenly divide, we need to assign the remaining
        // samples -- doing it completely randomly, though probably a better
        // way is to weight the randomness by the size of the remaining fraction
        if(left > 0)
          {
          unsigned long* rem = new unsigned long[np];

          for(int i = 0; i < np; i = i + 1)
            {
            rem[i] = i < left ? 1 : 0;
            }

          for(int i = 0; i < np; i = i + 1)
            {
            vtkIdType index = (vtkIdType)(rand() % np);
            unsigned long temp = rem[index];
            rem[index] = rem[i];
            rem[i] = temp;
            }

          for(int i = 0; i < np; i = i + 1)
            {
            dist[i] = dist[i] + rem[i];
            }

          delete [] rem;
          }
        }
      // no points
      else
        {
        for(int i = 0; i < np; i = i + 1)
          {
          dist[i] = 0;
          }
        }
      }

    // process 0 sends the fraction to each process
    this->InternalScatter(dist, recv, 1, 0);
    unsigned long retval = (vtkIdType)recv[0];

    delete [] dist;
    delete [] recv;

    return retval;
    }
  else
    {
    return this->MaximumNumberOfPoints;
    }
}

//----------------------------------------------------------------------------
int vtkMaskPoints::RequestData(
  vtkInformation *vtkNotUsed(request),
  vtkInformationVector **inputVector,
  vtkInformationVector *outputVector)
{
  // get the info objects
  vtkInformation *inInfo = inputVector[0]->GetInformationObject(0);
  vtkInformation *outInfo = outputVector->GetInformationObject(0);

  // get the input and output
  vtkDataSet *input = vtkDataSet::SafeDownCast(
    inInfo->Get(vtkDataObject::DATA_OBJECT()));
  vtkPolyData *output = vtkPolyData::SafeDownCast(
    outInfo->Get(vtkDataObject::DATA_OBJECT()));

  vtkPoints *newPts;
  vtkPointData *pd = input->GetPointData();
  vtkIdType numNewPts;
  double x[3];
  vtkIdType ptId, id = 0;
  vtkPointData *outputPD = output->GetPointData();
  vtkIdType numPts = input->GetNumberOfPoints();

  if(numPts < 1)
    {
    vtkErrorMacro(<<"No points to mask");
    return 1;
    }

  int abort = 0;

  // figure out how many sample points per process
  vtkIdType localMaxPts;
  // Make sure this does not exceed the number of points in the imput array
  localMaxPts = this->MaximumNumberOfPoints > numPts ? numPts : this->MaximumNumberOfPoints;
  if(this->ProportionalMaximumNumberOfPoints)
    {
    localMaxPts = this->GetLocalSampleSize(numPts,
                  this->InternalGetNumberOfProcesses());
    }

  vtkDebugMacro(<<"Masking points");

  // make sure new points aren't too big
  numNewPts = numPts / this->OnRatio;
  numNewPts = numNewPts > numPts ? numPts : numNewPts;
  if(numNewPts > localMaxPts || this->RandomMode)
    {
    numNewPts = localMaxPts;
    }

  // Allocate space
  newPts = vtkPoints::New();

  // Set the desired precision for the points in the output.
  if(this->OutputPointsPrecision == vtkAlgorithm::DEFAULT_PRECISION)
    {
    vtkPointSet *inputPointSet = vtkPointSet::SafeDownCast(input);
    if(inputPointSet)
      {
      newPts->SetDataType(inputPointSet->GetPoints()->GetDataType());
      }
    else
      {
      newPts->SetDataType(VTK_FLOAT);
      }
    }
  else if(this->OutputPointsPrecision == vtkAlgorithm::SINGLE_PRECISION)
    {
    newPts->SetDataType(VTK_FLOAT);
    }
  else if(this->OutputPointsPrecision == vtkAlgorithm::DOUBLE_PRECISION)
    {
    newPts->SetDataType(VTK_DOUBLE);
    }

  newPts->Allocate(numNewPts);
  outputPD->CopyAllocate(pd, numNewPts);

  // Traverse points and copy
  vtkIdType progressInterval=numPts/20 +1;
  if ( this->RandomMode ) // random modes
    {
    if(this->RandomModeType == 0)
      {
      // original random mode
      double cap;

      if ((static_cast<double>(numPts)/this->OnRatio) > localMaxPts)
        {
        cap = 2.0*numPts/localMaxPts - 1;
        }
      else
        {
        cap = 2.0*this->OnRatio - 1;
        }

      for (ptId = this->Offset;
      (ptId < numPts) && (id < localMaxPts) && !abort;
           ptId += (1 + static_cast<int>(static_cast<double>(vtkMath::Random())*cap)) )
        {
        input->GetPoint(ptId, x);
        id = newPts->InsertNextPoint(x);
        outputPD->CopyData(pd,ptId,id);
        if ( ! (id % progressInterval) ) //abort/progress
          {
          this->UpdateProgress (0.5*id/numPts);
          abort = this->GetAbortExecute();
          }
        }
      }
    else if(this->RandomModeType == 1)
      {
      // Vitter's algorithm D (without A)
      // for generating random samples incrementally: O(samplesize)
      ptId = -1;
      double vprime = log(d_rand());
      vtkIdType size = numPts;
      vtkIdType samplesize = localMaxPts;
      vtkIdType q1 = size - samplesize + 1;

      while(samplesize > 1)
        {
        double q2 = (q1 - 1.0) / (size - 1.0);
        double q3 = log(q2);
        vtkIdType s;

        while(1)
          {
          while(1)
            {
            s = (vtkIdType)(vprime / q3);
            if(s < q1)
              {
              break;
              }
            vprime = log(d_rand());
            }

          double lhs = log(d_rand());
          double rhs = s * (log((double)(q1 - s) / (size - s)) - q3);

          if(lhs <= rhs)
            {
            vprime = lhs - rhs;
            break;
            }

          double y = 1.0;
          vtkIdType bottom;
          vtkIdType limit;
          if(samplesize - 1 > s)
            {
            bottom = size - samplesize;
            limit = size - s;
            }
          else
            {
            bottom = size - s - 1;
            limit = q1;
            }

          for(vtkIdType top = size - 1; top >= limit; top = top - 1)
            {
            y = y * top / bottom;
            bottom = bottom - 1;
            }

          vprime = log(d_rand());
          if(q3 <= -(log(y) + lhs) / s)
            {
            break;
            }
          }

        // add a point
        ptId = ptId + s + 1;
        input->GetPoint(ptId, x);
        id = newPts->InsertNextPoint(x);
        outputPD->CopyData(pd, ptId, id);

        size = size - s - 1;
        samplesize = samplesize - 1;
        q1 = q1 - s;
        }

      // add last point
      ptId = ptId + (vtkIdType)(d_rand() * size) + 1;
      input->GetPoint(ptId, x);
      id = newPts->InsertNextPoint(x);
      outputPD->CopyData(pd, ptId, id);
      }
    else if(this->RandomModeType == 2)
      {
      // need to copy the entire data to sort it, to leave original in tact
      vtkPoints* pointCopy = vtkPoints::New();

      // Set the desired precision for the points.
      if(this->OutputPointsPrecision == vtkAlgorithm::DEFAULT_PRECISION)
        {
        vtkPointSet *inputPointSet = vtkPointSet::SafeDownCast(input);
        if(inputPointSet)
          {
          pointCopy->SetDataType(inputPointSet->GetPoints()->GetDataType());
          }
        else
          {
          pointCopy->SetDataType(VTK_FLOAT);
          }
        }
      else if(this->OutputPointsPrecision == vtkAlgorithm::SINGLE_PRECISION)
        {
        pointCopy->SetDataType(VTK_FLOAT);
        }
      else if(this->OutputPointsPrecision == vtkAlgorithm::DOUBLE_PRECISION)
        {
        pointCopy->SetDataType(VTK_DOUBLE);
        }

      vtkPointData* dataCopy = vtkPointData::New();
      vtkPointData* tempData = vtkPointData::New();

      pointCopy->Allocate(numPts);
      dataCopy->CopyAllocate(pd, numPts);
      for(vtkIdType i = 0; i < numPts; i = i + 1)
        {
        input->GetPoint(i, x);
        id = pointCopy->InsertNextPoint(x);
        dataCopy->CopyData(pd, i, id);
        }
      tempData->CopyAllocate(dataCopy, 1);

      // Woodring's spatially stratified random sampling: O(N log N)
      SortAndSample(pointCopy, dataCopy, tempData, 0, numPts,
                    numNewPts, 0);

      // copy the results back
      for(vtkIdType i = 0; i < numNewPts; i = i + 1)
        {
        pointCopy->GetPoint(i, x);
        id = newPts->InsertNextPoint(x);
        outputPD->CopyData(dataCopy, i, id);
        }

      tempData->Delete();
      dataCopy->Delete();
      pointCopy->Delete();

      // PARALLEL CODE
      // need this barrier or the communicator fails for some reason
      this->InternalBarrier();
      }
    }
  else // striding mode
    {
    for ( ptId = this->Offset;
    (ptId < numPts) && (id < localMaxPts) && !abort;
    ptId += this->OnRatio )
      {
      input->GetPoint(ptId, x);
      id = newPts->InsertNextPoint(x);
      outputPD->CopyData(pd,ptId,id);
      if ( ! (id % progressInterval) ) //abort/progress
        {
        this->UpdateProgress (0.5*id/numPts);
        abort = this->GetAbortExecute();
        }
      }
    }

  // Generate vertices if requested
  if ( this->GenerateVertices )
    {
    vtkCellArray *verts = vtkCellArray::New();
    if (this->SingleVertexPerCell)
      {
      verts->Allocate(id*2);
      }
    else
      {
      verts->Allocate(verts->EstimateSize(1,id+1));
      verts->InsertNextCell(id+1);
      }
    for ( ptId=0; ptId<(id+1) && !abort; ptId++)
      {
      if ( ! (ptId % progressInterval) ) //abort/progress
        {
        this->UpdateProgress (0.5+0.5*ptId/(id+1));
        abort = this->GetAbortExecute();
        }
      if (this->SingleVertexPerCell)
        {
          verts->InsertNextCell(1,&ptId);
        }
      else
        {
        verts->InsertCellPoint(ptId);
        }

      }
    output->SetVerts(verts);
    verts->Delete();
    }

  // Update ourselves
  output->SetPoints(newPts);
  newPts->Delete();

  output->Squeeze();

  vtkDebugMacro(<<"Masked " << numPts << " original points to "
                << id+1 << " points");

  return 1;
}

//----------------------------------------------------------------------------
int vtkMaskPoints::FillInputPortInformation(int, vtkInformation *info)
{
  info->Set(vtkAlgorithm::INPUT_REQUIRED_DATA_TYPE(), "vtkDataSet");
  return 1;
}

//----------------------------------------------------------------------------
void vtkMaskPoints::PrintSelf(ostream& os, vtkIndent indent)
{
  this->Superclass::PrintSelf(os,indent);

  os << indent << "Generate Vertices: "
     << (this->GenerateVertices ? "On\n" : "Off\n");
  os << indent << "SingleVertexPerCell: "
     << (this->SingleVertexPerCell ? "On\n" : "Off\n");
  os << indent << "MaximumNumberOfPoints: "
     << this->MaximumNumberOfPoints << "\n";
  os << indent << "On Ratio: " << this->OnRatio << "\n";
  os << indent << "Offset: " << this->Offset << "\n";
  os << indent << "Random Mode: " << (this->RandomMode ? "On\n" : "Off\n");
  os << indent << "Random Mode Type: " << this->RandomModeType << "\n";
  os << indent << "Proportional Maximum Number of Points: " <<
                  this->ProportionalMaximumNumberOfPoints << "\n";

  os << indent << "Output Points Precision: " << this->OutputPointsPrecision << "\n";
}