What is the Gauss Quadrature Formula you are using for triangle and tetrahedron?
I test on a regular operator with triangle mesh, and I change FEniCS quadrature order by setting parameters["form_compiler"]["quadrature_degree"].
I get the same matrix assembly results using the 1st order Gauss Quadrature, but I can't ge the same matrix assembly results using the 2st order Gauss Quadrature. The Gauss Quadrature Formula I have used is
1st order Gauss Quadrature:
$$ \int_{K}f(x) dx=f(a^{123})area(K)$$
2nd order Gauss Quadrature:
$$ \int_{K}f(x) dx=\sum_{j=1}^{n}f(b^{j})\frac{area(K)}{3}$$
$$a^{123}$$ is the center of each triangle. $$b^{j}$$ are the centers of three sides of each triangle.
