[issue2819] Full precision summation

[Mark Dickinson]

Mark Dickinson <dickinsm at gmail.com> added the comment:

> Question: I see "math module patch committed, r63542" in May 22.  But in
> 3.0b2, there is no math.fsum and math.sum seems to be a wrapper for
> builtin sum.  Has this not been forward ported (merged) yet?

I'm pretty sure it *was* merged:  math.sum should be the full-precision 
summation in both recent betas (2.6b2 and 3.0b2).  Try comparing
sum([1e100, 1, -1e100, -1]) and math.sum([1e100, 1, -1e100, -1])---they 
should produce -1.0 and 0.0 respectively.

The name change to fsum only happened in the last few days.

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<http://bugs.python.org/issue2819>
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