Method UpdateSearchMethod

Common/DataModel/vtkPiecewiseFunction.cxx:1037–1082

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//------------------------------------------------------------------------------
void vtkPiecewiseFunction::UpdateSearchMethod(double epsilon, double thresh)
{
  double averageDiff = 0;
  double stdDiff = 0;
  double currDiff = 0;
  const size_t nodeCount = this->Internal->Nodes.size();

  if (nodeCount < 3)
  {
    this->Internal->AutomaticSearchMethod = BINARY_SEARCH;
    return;
  }

  // compute the mean of the sampling rate
  averageDiff = (this->Internal->Nodes[nodeCount - 1]->X - this->Internal->Nodes[0]->X) /
    static_cast<double>(nodeCount);

  // It should not happens since the piecewise function
  // can't have multiple node at the same X
  if (std::abs(averageDiff) < epsilon)
  {
    this->Internal->AutomaticSearchMethod = BINARY_SEARCH;
    return;
  }

  // compute the standard deviation of the sampling rate
  for (size_t k = 0; k < this->Internal->Nodes.size() - 1; ++k)
  {
    currDiff = this->Internal->Nodes[k + 1]->X - this->Internal->Nodes[k]->X;
    stdDiff += std::pow(currDiff - averageDiff, 2);
  }

  stdDiff /= std::max(static_cast<double>(this->Internal->Nodes.size() - 1), 1.0);
  stdDiff = std::sqrt(stdDiff);

  double C = std::abs(stdDiff / averageDiff);

  if (C < thresh)
  {
    this->Internal->AutomaticSearchMethod = INTERPOLATION_SEARCH;
  }
  else
  {
    this->Internal->AutomaticSearchMethod = BINARY_SEARCH;
  }
}

//------------------------------------------------------------------------------
int vtkPiecewiseFunction::GetAutomaticSearchMethod()