def test_clear_grad(self):
x = Variable(np.array(2.0))
y = 2 * x
y.backward()
x.clear_grad()
y = 3 * x
y.backward()
self.assertEqual(x.grad.data, np.array(3.0))
def test_two_order_diff(self):
x = Variable(np.array(2.0))
y = x**4 - 2*x**2
y.backward(create_graph=True)
gx = x.grad
x.clear_grad()
self.assertEqual(gx.data, np.array(24.0))
gx.backward()
self.assertEqual(x.grad.data, np.array(44.0))
def test_higher_derivative(self):
x = Variable(np.array(2.0))
y = x**4 - 2 * x**2
y.backward()
self.assertEqual(x.grad.data, 24.0)
gx = x.grad
x.clear_grad()
gx.backward()
print(gx)
self.assertEqual(x.grad.data, 44.0)