[GitHub] [incubator-mxnet] YutingZhang opened a new issue #14396: mx.nd.Custom not working in subprocess

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

YutingZhang opened a new issue #14396: mx.nd.Custom not working in subprocess
URL: https://github.com/apache/incubator-mxnet/issues/14396
 
 
   mx.nd.Custom gets stuck at subprocess. 
   
   The following code to replicate the error is from https://github.com/wkcn/MobulaOP/issues/40#issuecomment-471803878
   
   ```python
   from concurrent import futures
   
   import mxnet as mx
   import sys
   from mobula.testing import assert_almost_equal
   sys.path.append('../../')  # Add MobulaOP Path
   
   class AdditionOP(mx.operator.CustomOp):
       def __init__(self):
           super(AdditionOP, self).__init__()
       def forward(self, is_train, req, in_data, out_data, aux):
           out_data[0][:] = in_data[0] + in_data[1]
       def backward(self, req, out_grad, in_data, out_data, in_grad, aux):
           in_grad[0][:] = out_grad[0]
           in_grad[1][:] = out_grad[0]
   
   @mx.operator.register("AdditionOP")
   class AdditionOPProp(mx.operator.CustomOpProp):
       def __init__(self):
           super(AdditionOPProp, self).__init__()
       def list_arguments(self):
           return ['a', 'b']
       def list_outputs(self):
           return ['output']
       def infer_shape(self, in_shape):
           return in_shape, [in_shape[0]]
       def create_operator(self, ctx, shapes, dtypes):
           return AdditionOP()
   
   def foo():
       a = mx.nd.array([1, 2, 3])
       b = mx.nd.array([4, 5, 6])
   
       a.attach_grad()
       b.attach_grad()
   
       print("REC")
       with mx.autograd.record():
           c = mx.nd.Custom(a, b, op_type='AdditionOP')
   
       dc = mx.nd.array([7, 8, 9])
       c.backward(dc)
   
       assert_almost_equal(a + b, c)
       assert_almost_equal(a.grad, dc)
       assert_almost_equal(b.grad, dc)
   
       print('Okay :-)')
       print('a + b = c \n {} + {} = {}'.format(a.asnumpy(), b.asnumpy(), c.asnumpy()))
   
   def main():
       ex = futures.ProcessPoolExecutor(1)
       r = ex.submit(foo)
       r.result()
   
   if __name__ == '__main__':
       main()
   ```

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