Re: [eigen] Eigen/FFT

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On Tue, Jun 23, 2009 at 1:59 PM, Benoit Jacob<jacob.benoit.1@xxxxxxxxx> wrote:
> 2009/6/23 Tim Hutt <tdhutt@xxxxxxxxx>:
>>>> I think the default behavior of Eigen/FFT should favor correctness and generality over speed.
>>>> 1) Scaling:
>>>> Other libraries (FFTW,IMKL,KISSFFT)  do not perform scaling, so there is a constant gain incurred after the forward&inverse transforms , so IFFT(FFT(x)) = Kx;  this is done to avoid a vector-by-value multiply..  The downside is that algorithms that worked correctly in Matlab/octave don't behave the same way once implemented in C++.
>> Simple solution, have FFT(x) and FFT_unscaled(x). That way people
>> won't be surprised by the results but they can still be optimised
> +1

if there is no true advantage in knowing that at compile time, I'd
prefer to see only one function:

FFT(..., int options = 0)

possible usages: FFT(x), FFT(x, Eigen::Unscaled), ...

I'm sure needs for other options will come.


> Benoit

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