xidulu commented on issue #17529: np.random.gamma(1,0) and np.random.gamma(0,0) 
hang
URL: 
https://github.com/apache/incubator-mxnet/issues/17529#issuecomment-582907092
 
 
   Hi @D-Roberts, I am the author of `np.random.gamma`. It seems that the 
rejection sampling got trapped in an infinity loop because of the invalid 
parameter (scale = 0), as no samples could be accepted according to the 
standard formula. 
   
   I will create a fix soon.
   
   However,  
https://docs.scipy.org/doc/numpy-1.15.0/reference/generated/numpy.random.gamma.html
 the doc for official NumPy says "The scale of the gamma distribution. Should 
be greater than zero.", 
   So IMO, returning zero is kind of like undefined behavior.
   Do you have any practical examples that involves setting scale to be zero? 
If not, I would consider raising an ValueError exception rather than returning 
zero.

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