DOC: Mention and try to explain pairwise summation in sum #13737
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Note that this behavour is of course inherited into `np.add.reduce` and many other reductions such as `mean` or users of this reduction, such as `cov`. This is ignored here. Closes numpygh-11331, numpygh-9393, numpygh-13734
eric-wieser
reviewed
Jun 8, 2019
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Thanks! There's a good chance I wouldn't have opened #13734 if I had found this explanation on the page for the |
mhvk
reviewed
Jun 8, 2019
| is only used when the summation is along the fast axis in memory. | ||
| Note that the exact precision may vary depending on other parameters. | ||
| In contrast to NumPy, Python's ``math.fsum`` function uses a slower but | ||
| 8000 more precise approach to summation. |
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Is it worth adding that for lower-precision floats such as f4, one can pass in dtype='f8' to increase precision?
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I guess so, although it is growing so long... Maybe the real solution would be to have a longer paragraph about floating point rounding in the user guide and link that...
This was referenced Jun 11, 2019
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Note that this behavour is of course inherited into
np.add.reduceandmany other reductions such as
meanor users of this reduction, suchas
cov. This is ignored here.Closes gh-11331, gh-9393, gh-13734
To be honest, not sure I am too happy with it, but it is one of those things that comes up every couple of months.