HomogeneousLeastSquares

#include <vtkMath.h>

namespace {
/* allocate memory for an nrow x ncol matrix */
template <class TReal> TReal** create_matrix(long nrow, long ncol)
{
  typedef TReal* TRealPointer;
  TReal** m = new TRealPointer[nrow];

  TReal* block = (TReal*)calloc(nrow * ncol, sizeof(TReal));
  m[0] = block;
  for (int row = 1; row < nrow; ++row)
  {
    m[row] = &block[row * ncol];
  }
  return m;
}

/* free a TReal matrix allocated with matrix() */
template <class TReal> void free_matrix(TReal** m)
{
  free(m[0]);
  delete[] m;
}

} // namespace

int main(int, char*[])
{

  // Solve XM = Y;

  int numberOfSamples = 3;
  int numberOfVariables = 2;
  double** x = create_matrix<double>(numberOfSamples, numberOfVariables);
  x[0][0] = 1;
  x[0][1] = 2;
  x[1][0] = 2;
  x[1][1] = 4;
  x[2][0] = 3;
  x[2][1] = 6;

  double** m = create_matrix<double>(numberOfVariables, 1);

  vtkMath::SolveHomogeneousLeastSquares(numberOfSamples, x, numberOfVariables,
                                        m);

  std::cout << "Solution is: " << m[0][0] << " " << m[1][0] << std::endl;

  free_matrix(x);
  free_matrix(m);

  return EXIT_SUCCESS;
}

cmake_minimum_required(VERSION 3.12 FATAL_ERROR)

project(HomogeneousLeastSquares)

find_package(VTK COMPONENTS 
)

if (NOT VTK_FOUND)
  message(FATAL_ERROR "HomogeneousLeastSquares: Unable to find the VTK build folder.")
endif()

# Prevent a "command line is too long" failure in Windows.
set(CMAKE_NINJA_FORCE_RESPONSE_FILE "ON" CACHE BOOL "Force Ninja to use response files.")
add_executable(HomogeneousLeastSquares MACOSX_BUNDLE HomogeneousLeastSquares.cxx )
  target_link_libraries(HomogeneousLeastSquares PRIVATE ${VTK_LIBRARIES}
)
# vtk_module_autoinit is needed
vtk_module_autoinit(
  TARGETS HomogeneousLeastSquares
  MODULES ${VTK_LIBRARIES}
)

cd HomogeneousLeastSquares/build

cmake ..

cmake -DVTK_DIR:PATH=/home/me/vtk_build ..

make

./HomogeneousLeastSquares