message: BUG: backward compatibility of CG was broken
diff: @@ -160,20 +160,25 @@ void ConjugateGradientImageFilter<OutputImageType>
  #if ITK_VERSION_MAJOR<5
  // Declare iterators that will be used throughout the calculations
  itk::ImageRegionConstIterator<OutputImageType> itB(this->GetB(), largest);
  - itk::ImageRegionIterator<OutputImageType> itA_out, itP, itR, itX;
  + itk::ImageRegionIterator<OutputImageType> itA_out, itP, itR, itIn, itX;
  // Initialize P0 and R0
  itP = itk::ImageRegionIterator<OutputImageType>(Pk, largest);
  itR = itk::ImageRegionIterator<OutputImageType>(Rk, largest);
  itA_out = itk::ImageRegionIterator<OutputImageType>(m_A->GetOutput(), largest);
  + itIn = itk::ImageRegionIterator<OutputImageType>(this->GetX(), largest);
  + itX = itk::ImageRegionIterator<OutputImageType>(this->GetOutput(), largest);
  while(!itP.IsAtEnd())
  {
  itR.Set(itB.Get() - itA_out.Get());
  itP.Set(itR.Get());
  + itX.Set(itIn.Get());
  ++itP;
  ++itR;
  ++itA_out;
  ++itB;
  + ++itIn;
  + ++itX;
  }
  #else
  // Instantiate the multithreader
  