[ITK Community] [Insight-users] Problem with ROI filter in a multithread filter

[Andrea Valsecchi]

I'm writing a multiple thread version of a custom filter. It uses a ROI
filter to extract a 3x3x3 region of the input image. The center of this ROI
is moved through the input image in a loop. If I run the code with a single
thread, it works correctly. If I use more threads I get segmentation fault
after the first iteration, i.e. when I reuse the ROI filter.

I've tried using a different instance of the ROI filter at each iteration,
saving the output of the filter to an image and calling DisconnectPipeline,
calling Modified(), Update(), UpdateLargestPossibleRegion(), replacing the
ROI filter with an Extract Image filter, but none of this worked. What am I
doing wrong? I'm using ITK 4.2


template<class TImage>
void myFilter<TImage>
::ThreadedGenerateData(const typename Superclass::OutputImageRegionType&
outputRegionForThread, ThreadIdType threadId)
{
  typename TImage::ConstPointer input = this->GetInput();
  typename TImage::Pointer output = this->GetOutput();
  typedef typename itk::RegionOfInterestFilter<TImage, TImage> roiType;

  typename roiType::Pointer roi = roiType::New();
  roi->SetInput(input);

  typename TImage::RegionType window;
  typename TImage::RegionType::SizeType size;
  size.Fill(3); //window size=3x3x3
  window.SetSize(size);
  typename TImage::IndexType pi; //pixel index

  itk::ImageRegionIteratorWithIndex<TImage> out(output,
outputRegionForThread);

  // typename TImage::Pointer buffer;

  for(; !out.IsAtEnd(); ++out)
  {
    pi = out.GetIndex();

    window.SetIndex(0, pi[0]-1);
    window.SetIndex(1, pi[1]-1);
    window.SetIndex(2, pi[2]-1);

    if ( outputRegionForThread.IsInside( window ) )
    {
      try
      {
        // typename roiType::Pointer roi = roiType::New();
        roi->SetInput(input);
        roi->SetExtractionRegion(window);
        // roi->SetNumberOfThreads(1);
        // roi->Modified();
        roi->Update();
        // roi->UpdateLargestPossibleRegion();
        // roi->Update();
        // buffer = roi->GetOutput();
        // buffer->Update();
        // buffer->DisconnectPipeline();
      }
      catch( itk::ExceptionObject & err )
      {
        std::cerr << "ExceptionObject caught !" << std::endl;
        std::cerr << err << std::endl;
        return;
      }
    }
  }
}


-- 
Andrea

-- 
Andrea Valsecchi

Postdoctoral Researcher
European Centre for Soft Computing

Edificio de Investigación
Calle Gonzalo Gutiérrez Quirós s/n
33600 Mieres, Asturias, Spain

Telephone: +34 985456545
Fax: +34 985456699
Email: andrea.valsecchi at softcomputing.es
Web: http://www.softcomputing.es
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