[GitHub] Neutron3529 opened a new issue #11504: Callback's bug with very fast speed.

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

Neutron3529 opened a new issue #11504: Callback's bug with very fast speed.
URL: https://github.com/apache/incubator-mxnet/issues/11504
 
 
   ```
   INFO:root:Epoch[0] Batch [1]    Speed: 323135.90 samples/sec    accuracy=0.102800
   INFO:root:Epoch[0] Batch [2]    Speed: 641232.84 samples/sec    accuracy=0.109800
   Traceback (most recent call last):
     File "<stdin>", line 7, in <module>
     File "d:\program files\python37\lib\site-packages\mxnet\module\base_module.py", line 533, in fit
       callback(batch_end_params)
     File "d:\program files\python37\lib\site-packages\mxnet\callback.py", line 159, in __call__
       speed = self.frequent * self.batch_size / (time.time() - self.tic)
   ```
   ZeroDivisionError: float division by zero
   it seems that time.time may not always return different result, which cause a division by zero exception.
   ```
   >>> [time.time() for i in range(100000)][0::99999]
   [1530318107.497374, 1530318107.497374]
   >>> [time.time() for i in range(100000)][0::99999]
   [1530318108.5909886, 1530318108.6061418]
   ```
   maybe use
   ```
   speed = self.frequent * self.batch_size / (time.time() - self.tic+1e-38)
   ```
   will be better, or mxnet should use a high performance timer rather than time.time
   for example, using `time.perf_counter_ns` may be better
   ```
   >>> [time.perf_counter_ns() for i in range(10)]
   [751763884032, 751763884495, 751763884959, 751763884959, 751763885423, 751763885887, 751763885887, 751763886351, 751763886351, 751763886814]
   ```
   

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