def test_external_hessian_SimpleModel2(self):
        model = SimpleModel2()
        m = model.make_model()
        x_init_list = [
                [-5.0], [-4.0], [-3.0], [-1.5], [0.5], [1.0], [2.0], [3.5]
                ]
        external_model = ExternalPyomoModel(
                [m.x], [m.y], [m.residual_eqn], [m.external_eqn],
                )

        for x in x_init_list:
            external_model.set_input_values(x)
            hess = external_model.evaluate_hessian_external_variables()
            expected_hess = model.evaluate_external_hessian(x[0])
            self.assertAlmostEqual(
                    hess[0][0,0],
                    expected_hess,
                    delta=1e-7,
                    )
    def test_external_hessian_SimpleModel2x2_1(self):
        model = SimpleModel2by2_1()
        m = model.make_model()
        m.x[0].set_value(1.0)
        m.x[1].set_value(2.0)
        m.y[0].set_value(3.0)
        m.y[1].set_value(4.0)
        x0_init_list = [-5.0, -3.0, 0.5, 1.0, 2.5]
        x1_init_list = [-4.5, -2.3, 0.0, 1.0, 4.1]
        x_init_list = list(itertools.product(x0_init_list, x1_init_list))
        external_model = ExternalPyomoModel(
            list(m.x.values()),
            list(m.y.values()),
            list(m.residual_eqn.values()),
            list(m.external_eqn.values()),
        )

        for x in x_init_list:
            external_model.set_input_values(x)
            hess = external_model.evaluate_hessian_external_variables()
            expected_hess = model.evaluate_external_hessian(x)
            for matrix1, matrix2 in zip(hess, expected_hess):
                np.testing.assert_allclose(matrix1, matrix2, rtol=1e-8)