Function fft

contents/cooley_tukey/code/c/fft.c:9–23

#include <fftw3.h>

void fft(double complex *x, size_t n) {
    double complex y[n];
    memset(y, 0, sizeof(y));
    fftw_plan p;

    p = fftw_plan_dft_1d((int)n, (fftw_complex*)x, (fftw_complex*)y,
                         FFTW_FORWARD, FFTW_ESTIMATE);

    fftw_execute(p);
    fftw_destroy_plan(p);

    for (size_t i = 0; i < n; ++i) {
        x[i] = y[i] / sqrt((double)n);
    }
}

void dft(double complex *X, const size_t N) {
    double complex tmp[N];