Series test_sum fails due to different NaN behavior

[drudd]

I have an installation of Pandas of 0.16.0 that fails TestSeries.test_sum when using Numpy 1.9.2 compiled against MKL 11.2. Here is a minimal test:

import numpy as np
import pandas as pd

s = np.nan*pd.util.testing.makeStringSeries()
print s.sum()

For Pandas 0.15.2, Numpy 1.9.1 compiled against MKL 10.3, this prints nan, but for Numpy 1.9.2 against 11.2 it prints 0.0.

I don't know whether to blame Pandas version, blas or Numpy version, and will run additional tests to distinguish which is at fault. I have stepped through execution for both cases and they are identical up to the call to at pandas/core/nanops.py:89

[jreback]

xref to #9422 and #8383

[jreback]

this is a dupe of #9422 actually

feel free to comment / propose fix etc there

thanks for the report