[SciPy-User] Single precision FFT insufficiently accurate.
Mon Jun 28 08:58:46 CDT 2010
Den 28.06.2010 14:37, skrev Ralf Gommers:
> Anne's argument sounded convincing, so I think the way it is now in
> the 0.8.x branch is fine. Probably good to add a warning in the
> docstrings like:
> .. note:: In scipy 0.8.0 `fft` in single precision is available,
> but *only*
> for input array sizes which can be factorized into
> (combinations of) 2,
> 3 and 5. For other sizes the computation will be done in double
This is actually quite diagnostic. 2, 3, and 5 are the only primes
FFTPACK support. Larger primes has an O(N**2) fallback.
The source of the (rounding?) error must therefore be in the O(N**2)
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