[GitHub] [incubator-mxnet] apeforest edited a comment on issue #14991: Second order gradient wrt inputs, expected behaviour.

[GitBox <gi...@apache.org>]

apeforest edited a comment on issue #14991: Second order gradient wrt inputs, expected behaviour.
URL: https://github.com/apache/incubator-mxnet/issues/14991#issuecomment-494119975
 
 
   Calling autograd.grad on a first order ndarray seems not working this way. The API design could have been better documented.
   The following block works.
   ```
   def test_ag_grad():
       x = mx.nd.array([1, 2, 3])
       y = mx.nd.array([2, 3, 4])
       x.attach_grad()
       y.attach_grad()
       with mx.autograd.record():
           z = nd.elemwise_add(x, y)
           x_grad = mx.autograd.grad(z, x, create_graph=True, retain_graph=True)[0]
           print(x_grad)
           #first_grad = nd.concat(*[x.reshape(-1) for x in x_grad_y_grad], dim=0)
           #fg_f = 2 * first_grad
           #second_grad = mx.autograd.grad(fg_f, [x,y], retain_graph=True)
           fg_f = 2 * x_grad
       fg_f.backward()
       print(x.grad)
   ```
   

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