Set is_tensor_product_flag in Quadrature::initialize(..)

[simonsticko]

If you first create a quadrature which is a tensor product and then call initialize with points and weights which does not correspond to a tensor product, you can make is_tensor_product_flag have wrong value. Set the flag in intialize(..) to avoid this.

#include <deal.II/base/quadrature_lib.h>

using namespace dealii;

int
main()
{
  const int dim = 2;

  QGauss<dim> quadrature(2);

  std::vector<Point<dim>> arbirary_points(3);
  std::vector<double>     arbirary_weights(3);

  // Puts the tensor product flag in the wrong state.
  quadrature.initialize(arbirary_points, arbirary_weights);
  
  std::cout << quadrature.is_tensor_product() << std::endl;
}

Or would it be better to require that the quadrature is empty when initialize is called?

[peterrum]

/rebuild

[peterrum]

Looks good to me! I would have thought that Quadrature checks the points and sets the flag accordingly, but obviously this is not the case in the general case but just in the 1D setting.

[kronbichler]

I agree with the present code.