test_autograd.py 文件源码

def test_hessian_vector(self):
        x = Variable(torch.randn(2, 2), requires_grad=True)
        y = Variable(torch.randn(2, 2), requires_grad=True)

        z = x ** 2 + y * x + y ** 2
        z.backward(Variable(torch.ones(2, 2), requires_grad=True), retain_variables=True)

        x_grad = 2 * x.data + y.data
        y_grad = x.data + 2 * y.data
        self.assertEqual(x.grad.data, x_grad)
        self.assertEqual(y.grad.data, y_grad)

        grad_sum = 2 * x.grad + y.grad
        grad_sum.backward(torch.ones(2, 2))
        x_hv = torch.ones(2, 2) * 5
        y_hv = torch.ones(2, 2) * 4
        self.assertEqual(x.grad.data, x_grad + x_hv)
        self.assertEqual(y.grad.data, y_grad + y_hv)