BUG: ZeroDivisionError when returning zero-length series/arrays #19

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1. asher-pembroke

   changed the title [-]ZeroDivisionError when returning zero-length series/arrays[/-] [+]BUG: ZeroDivisionError when returning zero-length series/arrays[/+] on Oct 31, 2019
2. jrbourbeau commented on Oct 31, 2019

   

   jrbourbeau

   on Oct 31, 2019

   Member

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   Thanks @asher-pembroke for the nice example! I'm able to reproduce the error. This originates from the cost function dividing by the number of bytes of an object:

   cachey/cachey/cache.py

   Lines 6 to 7 in 382e55e

   	def cost(nbytes, time):
   	return float(time) / nbytes / 1e9

   which is current 0 for things like empty NumPy arrays:

   In [1]: from cachey import nbytes
   
   In [2]: import numpy as np
   
   In [3]: nbytes(np.array([]))
   Out[3]: 0

   Do you have any thoughts on how this situation might be improved?
3. accurrently commented on Nov 1, 2019

   

   accurrently

   on Nov 1, 2019

   Contributor

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   cachey/cachey/cache.py

   Lines 6 to 7 in 382e55e

   	def cost(nbytes, time):
   	return float(time) / nbytes / 1e9

   This should be somewhat easy to fix. Consider that nbytes ought to be an int (because you can't have a fractional byte), but divide by some fractional float if nbytes is 0:

   def cost(nbytes, time):
       return float(time) / max(nbytes, .1) / 1e9

   ZeroDivisionError is avoided, but you still have something smaller than a byte. Depending on how scoring should be affected, this can be an arbitrary, such that max(nbytes, x) where 0 < x < 1.