[Numpy-discussion] numpy and roundoff(?)

Christopher Barker Chris.Barker@noaa....
Mon Mar 3 11:52:42 CST 2008

Damian Eads wrote:
> At work we noticed a significant difference in results occurring in two 
> versions of our code, an earlier version written in C++, and a later 
> version written in Python/numpy. The algorithms were structured about 
> the same. My colleague found the cause of the discrepancy; it turned out 
> to be a difference in the way numpy and the C++ program were compiled. 
> One used -mfpmath=sse, and the other, -mfpmath=387. Keeping them both 
> the same cleared the discrepancy.

Was it really a "significant" difference, or just noticeable? I hope 
not, that would be pretty scary!


Christopher Barker, Ph.D.

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