[issue17958] int(math.log(2**i, 2))

[Mark Dickinson]

Mark Dickinson added the comment:

Sorry: this is not a bug, but a difficult-to-avoid consequence of floating-point imprecision: math.log(n, 2) is computed as log(n) / log(2), and each of the log computations and the division can introduce small errors.

For what it's worth, Python 3.3 has a `log2` function, which has accuracy that's a little bit better than math.log(n, 2), and gives the 'correct' answer exact powers of 2.

Closing as invalid.

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nosy: +mark.dickinson
resolution:  -> invalid
status: open -> closed

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<http://bugs.python.org/issue17958>
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