Fast Fourier Transform

The castor framework wraps the kissfft library in a standalone kissfft.hpp header file so it is not necessary to download it. Currently, only single precision arithmetic is supported. We describe below a basic example.

A minimum working file can be found below.

#include "castor/matrix.hpp"
#include "castor/kissfft.hpp"

int main()
{
    matrix<std::complex<float>> A = rand(3,4) + M_1I*rand(3,4);
    // your code here
    return 0;
}

In the code above, we created a random complex single precision matrix with twelve elements. Since only the one-dimensional fft is supported, the matrix A will be treated as a one-dimensional array where the first row comes first, etc. Now we declare a second matrix B where we store the result of the forward-backward discrete Fourier transform.

matrix<std::complex<float>> ifft(fft(A));

While A is a two-dimensional array, this is not the case for B. In order to access the one-dimensional data of A, we use a view on the 12 elements using ranged access (see view) and we compare it to B.

disp(norm(eval(A(range(0,12))) - B, "inf");

The output should be something more or less like

(9.31323e-08,0)

Please note that this code is part of the overview_kissfft.cpp file which can be found in the demo/demo_kissfft subfolder.