GSL을 이용한 Wavelet transforms

Example:

#include <stdio.h>
#include <math.h>
#include <gsl/gsl_sort.h>
#include <gsl/gsl_wavelet.h>

#include <random>
#include <functional>

int main(int argc, char **argv)
{
    (void)(argc); /* avoid unused parameter warning */
    int i, n = 256, nc = 20;
    double *orig_data = (double*)malloc(n * sizeof(double));
    double *data = (double*)malloc(n * sizeof(double));
    double *abscoeff = (double*)malloc(n * sizeof(double));
    size_t *p = (size_t*)malloc(n * sizeof(size_t));

    gsl_wavelet *w;
    gsl_wavelet_workspace *work;

    std::mt19937 engine(100);		// Fixed seed
    std::uniform_real_distribution<> distribution;
    auto generator = bind(distribution, engine);

    w = gsl_wavelet_alloc(gsl_wavelet_daubechies, 4);
    work = gsl_wavelet_workspace_alloc(n);

    for (i = 0; i < n; i++)
    {
        orig_data[i] = generator();
        data[i] = orig_data[i];
    }

    gsl_wavelet_transform_forward(w, data, 1, n, work);

    for (i = 0; i < n; i++)
    {
        abscoeff[i] = fabs(data[i]);
    }

    gsl_sort_index(p, abscoeff, 1, n);

    for (i = 0; (i + nc) < n; i++)
        data[p[i]] = 0;

    gsl_wavelet_transform_inverse(w, data, 1, n, work);

    for (i = 0; i < n; i++)
    {
        printf("%g %g\n", orig_data[i], data[i]);
    }

    gsl_wavelet_free(w);
    gsl_wavelet_workspace_free(work);

    free(data);
    free(orig_data);
    free(abscoeff);
    free(p);

    return 0;
}