[GitHub] lightingghost commented on issue #10220: Check failed: !ndinputs.back()->is_none()

[GitBox]

lightingghost commented on issue #10220: Check failed: 
!ndinputs.back()->is_none()
URL: 
https://github.com/apache/incubator-mxnet/issues/10220#issuecomment-375840105
 
 
   Here is a minimum sample to reproduce this error
   ```python
   
   import mxnet as nd
   from mxnet import nd, sym, autograd
   from mxnet import gluon as g
   
   inp = nd.ones((20, 10))
   class Test(g.nn.HybridBlock):
       def __init__(self):
           super(Test, self).__init__()
           self.fc1 = g.nn.Dense(100)
           self.fc2 = g.nn.Dense(20)
           
       def hybrid_forward(self, F, x):
           A = self.fc1(x)
           X = self.fc2(x)
           A = A.reshape((-1, 10, 10))
           X = X.reshape((-1, 10, 2))
           A = 0.5 <= A
           X = 0.5 <= X
           s = F.batch_dot(A, X)
           return s.sum()
       
   test = Test()
   #test.hybridize()
   test.initialize()
   with autograd.record():
       l = test(inp)
       
   l.backward()
   
   ```
   As stated earlier, calling `hybridize()` will make the error disappear.
   
   Besides, a slight change from `batch_dot` to `dot` will make the error 
disappear.
   

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