[Numpy-discussion] strange runtimes of numpy fft

[Robert Kern]

On Thu, Nov 14, 2013 at 5:30 PM, Max Linke <max_linke at gmx.de> wrote:
>
> You can check everything in the notebook, it will generate all the data.
> I checked the runtime for sizes in logspace(2, 7, 25). I know that the
> fft will work faster for array sizes that are a power of 2 but
> differences on 3 orders of magnitude is huge.

Primes are especially bad. 215443, for example, is prime. Going from
O(N*logN) to O(N**2) where N=215443 accounts for 3 orders of magnitude, at
least.

--
Robert Kern
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