[issue27761] Private _nth_root function loses accuracy

[Mark Dickinson]

Mark Dickinson added the comment:

Steven: can you explain why you think your code *should* be giving exact results for exact powers? Do you have an error analysis that says that should be the case?

One issue here is that libm pow functions vary hugely in quality, so any algorithm that depends on ** or math.pow is going to be hard to prove anything about.

I think the tests should simply be weakened: it's unreasonable to expect perfect results in this case.

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nosy: +mark.dickinson

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue27761>
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