[GitHub] altosaar commented on issue #8130: autograd.backward() segfaults: how to get gradients with respect to a subset of variables in mxnet?

[gi...@git.apache.org]

altosaar commented on issue #8130: autograd.backward() segfaults: how to get gradients with respect to a subset of variables in mxnet? 
URL: https://github.com/apache/incubator-mxnet/issues/8130#issuecomment-333903906
 
 
   Thanks @piiswrong !
   
   I installed the newest mxnet (`pip install --pre mxnet`).
   
   Here is a reproducible example based on what you suggested:
   
   ```
   In [49]: from mxnet import nd, autograd
   
   In [50]: x = nd.array([1.])
   
   In [51]: z = nd.array([1.])
   
   In [52]: x.attach_grad()
   
   In [53]: z.attach_grad()
   
   In [54]: with autograd.record():
       ...:     first = nd.square(x)
       ...:     second = nd.square(z)
       ...:     y = first + second
       ...:     autograd.grad(y, [x], retain_graph=True)
       ...:     autograd.grad(y, [z])
       ...:
   
   In [56]: x.grad
   Out[56]:
   
   [ 0.]
   <NDArray 1 @cpu(0)>
   
   In [57]: z.grad
   Out[57]:
   
   [ 0.]
   <NDArray 1 @cpu(0)>
   ```
   
 
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