Numeric:FFT inverse_real_fft doesn't trevni!

[Christian Tismer]

"Warren B. Focke" wrote:
> 
> Christian Tismer <tismer at appliedbiometrics.com>:
> 
> >mhuster at hotmail.com wrote:
> >>I thought that calling inverse_real_fft on the
> >> same array as real_fft produced would give back the original array,
> >> possibly scaled by N. Not so. I pasted in a sample of a session.
> 
> >No, that's a misconception.
> >The real fft is just a speedup for cases where your data
> >has only real coefficients. Providing an inverse function
> >would be useless, since after any modifications of your
> >complex result, you will usually not expect a real result.
> 
>         That may be the intention of the FFT module, but it is not the
> intention of the FFTPACK library on which it is based.  I have written
> working FORTRAN programs using FFTPACK, under the assumption that the
> rffti function behaves as Michael expected inverse_real_fft to.
>         I find that operation extremely useful for doing things like
> convolution, interpolation, or differentiation in the Fourier domain.

Hmm. So maybe there is a bug in the FFT module?
Since you have experience using FFTPACK, it might
be helpful if you had a look into FFT.py if this is
correct. 
I'd really be interested to see what's the inverse of what,
and couldn't figure it out yet.

ciao - chris

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