[Numpy-discussion] Numpy float precision vs Python list float issue

Matthieu Brucher matthieu.brucher@gmail....
Mon Apr 20 12:47:57 CDT 2009


> I understand the numerical mathematics behind this very well but my
> point is that his two algorithms appear to be identical (same
> operations, same order), he simply uses lists in one and arrays in the
> other. It's not like he used vectorization or other array-related
> operations - he uses for loops in both cases. Of course I agree that
> 1e-15 error should be acceptable, but that's not the point. I think
> there is legitimate curiosity in wondering why there is any difference
> between using the two data types in exactly the same algorithm.

Hi,
There are cases where the same algorithm implementation outputs
different results in optimized mode, depending on data alignment. As
David said, this is something that is known or at least better known.

Matthieu
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