Re: [eigen] FFT for Eigen

[Thomas Capricelli <orzel@xxxxxxxxxxxxxxx>]

I agree that fftw is kind of a strandard, it handles every sizes (not only 
power of 2) and every  dimension (not only 1D or 2D FFT).
I use it on some projects and i'm very happy with it.

Though of course, the current situation if you want to use both eigen and fftw 
is to convert data back & forth between libraries. This is especially not 
great as complex numbers are involved.

I would enjoy a fft in eigen, and in an ideal world that would use fftw in the 
backend.

The way fftw works is the following : you create a "plan" (describing 
dimensions, sizes, type and so on), and you use the plan on data. The idea of 
course is that you create the plan once and use it several times. I am not 
sure if this is good or bad wrt to the use of fftw in eigen. Just wanted to 
mention it.

greatings;
Thomas


In data lunedì 18 maggio 2009 16:34:47, Benoit Jacob ha scritto:
> Many people who need a linear algebra library, also need a FFT
> library. In that case, if both libraries use the same data types
> (read: if they both talk in terms of Eigen:: objects like vectors)
> then it's extra convenient. They can also share infrastructure for
> handling various numeric types, for handling fixed-size/dynamic-size
> with a consistent API... Eigen has all that and so it makes sense to
> add a small FFT module that integrates well with that. Then, I think
> that Mark was very clear that FFTW is "much faster", and that's why I
> think we all agree that a must-have feature is that such optimized
> libraries may be used as optional backends. The idea is to enjoy their
> performance while using a uniform Eigen API. Also Mark notes that
> kissFFT provides more flexibility wrt custom datatypes (like
> fixed-point).
>
> Cheers,
> Benoit
>
> 2009/5/18 Robert Lupton the Good <rhl@xxxxxxxxxxxxxxxxxxx>:
> > I'm not quite sure why eigen needs an FFT library,
> > especially when there's a standard (C) library
> > that everyone uses, FFTW?
> >
> > Now, I can see the advantages of a pure-template
> > C++ library if it's competitive computationally,
> > so the question that I'd ask is, how do the
> > kissfft benchmarks look relative to FFTW?
> >
> >
> >                                R

-- 
Thomas Capricelli <orzel@xxxxxxxxxxxxxxx>
http://www.freehackers.org/thomas