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muSpectre/src/libmufft/fft_utils.cc
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fft_utils.cc
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/**
* @file fft_utils.cc
*
* @author Till Junge <till.junge@altermail.ch>
*
* @date 11 Dec 2017
*
* @brief implementation of fft utilities
*
* Copyright © 2017 Till Junge
*
* µFFT is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public License as
* published by the Free Software Foundation, either version 3, or (at
* your option) any later version.
*
* µFFT is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with µFFT; see the file COPYING. If not, write to the
* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
* * Boston, MA 02111-1307, USA.
*
* Additional permission under GNU GPL version 3 section 7
*
* If you modify this Program, or any covered work, by linking or combining it
* with proprietary FFT implementations or numerical libraries, containing parts
* covered by the terms of those libraries' licenses, the licensors of this
* Program grant you additional permission to convey the resulting work.
*/
#include "fft_utils.hh"
namespace muFFT {
/* ---------------------------------------------------------------------- */
std::valarray<Real> fft_freqs(size_t nb_samples) {
std::valarray<Real> retval(nb_samples);
Int N = (nb_samples - 1) / 2 + 1; // needs to be signed int for neg freqs
for (Int i = 0; i < N; ++i) {
retval[i] = i;
}
for (Int i = N; i < Int(nb_samples); ++i) {
retval[i] = -Int(nb_samples) / 2 + i - N;
}
return retval;
}
/* ---------------------------------------------------------------------- */
std::valarray<Real> fft_freqs(size_t nb_samples, Real length) {
return fft_freqs(nb_samples) / length;
}
} // namespace muFFT
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