wkcn commented on issue #11913: Unexpectedly poor copy() performance
URL: 
https://github.com/apache/incubator-mxnet/issues/11913#issuecomment-409904550
 
 
   @safrooze 
   I modified the code then test it.
   Here is the code I modified.
   
   ```
   a = nd.empty((1, 512, 120*120))
   nd.waitall()
   
   start = time()
   for _ in range(2000):
       b = a.copy()
       nd.waitall()
   print('\tcopy: elapsed: {:.2f}'.format(time() - start))
   
   start = time()
   for _ in range(2000):
       b = a + 0.0
       nd.waitall()
   print('\tcopy via add: elapsed: {:.2f}'.format(time() - start))
   ```
   
   And I test the code you provided,
   the elapsed time of copy is almost invariable.
   But the elapsed copy via add is around 4.
   
   The reason that I changed the code is that the computation of NDArray is 
lazy.
   The script `b = a + 0.0` only records this operation but there is no actual 
computation until `nd.waitall` is called.

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