[GitHub] [incubator-mxnet] wkcn commented on issue #16053: Fixes #15543

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

wkcn commented on issue #16053: Fixes #15543
URL: https://github.com/apache/incubator-mxnet/pull/16053#issuecomment-527710882
 
 
   Hi @zhanghang1989 , is there any difference between `a -= b` and `a[:] -= b`?
   `a[:] -= b` may call extra function `__getitem__`.
   ```python
   import mxnet as mx
   import time
   
   T = 1000
   N = 1000
   
   
   while 1:
       ti = time.time()
       a = mx.nd.arange(N)
       for i in range(T):
           a += 1
       mx.nd.waitall()
       print('a += b: ', time.time() - ti)
   
       ti = time.time()
       a = mx.nd.arange(N)
       for i in range(T):
           a[:] += 1
       mx.nd.waitall()
       print('a[:] += b: ', time.time() - ti)
   ```
   
   Output:
   ```
   a += b:  0.06155872344970703
   a[:] += b:  0.3492248058319092
   a += b:  0.06215381622314453
   a[:] += b:  0.30852508544921875
   a += b:  0.07872796058654785
   a[:] += b:  0.31493425369262695
   a += b:  0.08103752136230469
   a[:] += b:  0.3226127624511719
   a += b:  0.05706977844238281
   a[:] += b:  0.29704785346984863
   
   ```

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