[GitHub] [arrow] pitrou commented on pull request #8879: ARROW-10797: [C++] Vendor and use PCG random generator library

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

pitrou commented on pull request #8879:
URL: https://github.com/apache/arrow/pull/8879#issuecomment-824048390


   This exposes a small precision issue in the variance kernel tests in MinGW32 on 32-bit floats (because of rounding issues perhaps?):
   https://github.com/pitrou/arrow/runs/2400347814?check_suite_focus=true#step:10:831
   
   According to Numpy, the two float64 values differ by 5 ULPs:
   ```python
   >>> a
   1011966660.249961
   >>> b
   1011966660.2499604
   >>> np.testing.assert_array_max_ulp(a, b)
   Traceback (most recent call last):
     File "<ipython-input-15-48fada135e2b>", line 1, in <module>
       np.testing.assert_array_max_ulp(a, b)
     File "/home/antoine/miniconda3/envs/pyarrow/lib/python3.7/site-packages/numpy/testing/_private/utils.py", line 1643, in assert_array_max_ulp
       (maxulp, np.max(ret)))
   AssertionError: Arrays are not almost equal up to 1 ULP (max difference is 5 ULP)
   ```
   


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