fftw_loop.cpp

Output

Armadillo FFT Time = 46.8176
FFTW Loop[1]. Time = 0.052592
FFTW Loop[2]. Time = 0.003976
FFTW Loop[3]. Time = 0.003865
FFTW Loop[4]. Time = 0.003716

Source

#include "sigpack.h"
using namespace arma;
using namespace sp;

int main()
{
  int N = 45191; // Large prime number
  FFTW ss(N, FFTW_ESTIMATE);
  vec x(N);
  cx_vec Sxx(N);

  vec P(N);
  clock_t tic;
  x.randn();
  tic = clock();
  Sxx = fft(x);
  cout << " Armadillo FFT Time = " << (clock() - tic) / double(CLOCKS_PER_SEC)
       << endl;

  for (int n = 1; n < 5; n++)
  {
    x.randn();
    tic = clock();
    Sxx = ss.fft(x);
    cout << "FFTW Loop[" << n
         << "]. Time = " << (clock() - tic) / double(CLOCKS_PER_SEC) << endl;
  }
  return 0;
}