Re: [eigen] Question on eigen/FFT

[Mark Borgerding <mark@xxxxxxxxxxxxxx>]

Hi.
I am the original author of the unsupported FFT module. Unfortunately, I 
don't have the time now to support it and no one else has stepped up and 
volunteered to take the reigns.

re alignment.
The Eigen allocation should be sufficient.  If you wish to use 
std::vector, then you'll probably want to specialize it with an 
aligned_allocator -- a quick google search should turn something up there.

The return-by-value proxy is an Eigen-ism that allows expressions to be 
composed and simplified before evaluation. The FFT module does not 
exploit this power well, if at all.

Hope this helps,
Mark Borgerding

On 03/08/2016 12:53 AM, Matthias Pospiech wrote:
> Hello,
> I looked at the unsupported FFT(W) implementation in eigen.
> I like the concept of the plan and execute approach implemented.
>
> However I have the impression that the code is not finished.
> Can someone comment on the state of the implementation?
>
> Also I wonder how to create the arrays for fftw. It requires aligned 
> arrays
> for fast computation. The eigen/fft code itsself does not use the 
> fftw_malloc functions.
>
> The example uses plain vector<complex<float> > which is possible but 
> might not allow
> fast computation.
>
> Eigen::FFT<float> fft;
>
> std::vector<float> timevec = MakeMyData();
> std::vector<std::complex<float> > freqvec;
>
> fft.fwd( freqvec,timevec);
> // manipulate freqvec
> fft.inv( timevec,freqvec);
>
> In FFT I was wondering the use of "fft_fwd_proxy"
> I see no example code nor do I understand its usage.
>
> I am interested in the code mainly because I have my own fftw-cpp class
> and I consider to reuse the fft-code from eigen and publish it 
> independed of eigen.
>
> Matthias