test_autograd.py 文件源码

def test_multi_backward(self):
        x = Variable(torch.randn(5, 5), requires_grad=True)
        y = Variable(torch.randn(5, 5), requires_grad=True)

        q = Variable(torch.randn(5, 5), requires_grad=True)

        a = Variable(torch.randn(5, 5), requires_grad=True)
        b = Variable(torch.randn(5, 5), requires_grad=True)

        q2 = q * 2
        z = x + y + q2
        c = a * b + q2
        grad_z = torch.randn(5, 5)
        grad_c = torch.randn(5, 5)
        torch.autograd.backward([z, c], [grad_z, grad_c])

        self.assertEqual(x.grad.data, grad_z)
        self.assertEqual(y.grad.data, grad_z)
        self.assertEqual(a.grad.data, grad_c * b.data)
        self.assertEqual(b.grad.data, grad_c * a.data)
        self.assertEqual(q.grad.data, (grad_c + grad_z) * 2)