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/* fft/hc_init.c
*
* Copyright (C) 1996, 1997, 1998, 1999, 2000 Brian Gough
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or (at
* your option) any later version.
*
* This program 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 General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*/
TYPE(gsl_fft_halfcomplex_wavetable) *
FUNCTION(gsl_fft_halfcomplex_wavetable,alloc) (size_t n)
{
int status;
size_t i;
size_t n_factors;
size_t t, product, product_1, q;
double d_theta;
TYPE(gsl_fft_halfcomplex_wavetable) * wavetable ;
if (n == 0)
{
GSL_ERROR_VAL ("length n must be positive integer", GSL_EDOM, 0);
}
wavetable = (TYPE(gsl_fft_halfcomplex_wavetable) *)
malloc(sizeof(TYPE(gsl_fft_halfcomplex_wavetable)));
if (wavetable == NULL)
{
GSL_ERROR_VAL ("failed to allocate struct", GSL_ENOMEM, 0);
}
wavetable->trig = (TYPE(gsl_complex) *) malloc (n * sizeof (TYPE(gsl_complex)));
if (wavetable->trig == NULL)
{
/* error in constructor, prevent memory leak */
free(wavetable) ;
GSL_ERROR_VAL ("failed to allocate trigonometric lookup table",
GSL_ENOMEM, 0);
}
wavetable->n = n ;
status = fft_halfcomplex_factorize (n, &n_factors, wavetable->factor);
if (status)
{
/* error in constructor, prevent memory leak */
free(wavetable->trig) ;
free(wavetable) ;
GSL_ERROR_VAL ("factorization failed", GSL_EFACTOR, 0);
}
wavetable->nf = n_factors;
d_theta = 2.0 * M_PI / ((double) n);
t = 0;
product = 1;
for (i = 0; i < n_factors; i++)
{
size_t j;
const size_t factor = wavetable->factor[i];
wavetable->twiddle[i] = wavetable->trig + t;
product_1 = product; /* product_1 = p_(i-1) */
product *= factor;
q = n / product;
for (j = 1; j < factor; j++)
{
size_t k;
size_t m = 0;
for (k = 1; k < (q + 1) / 2; k++)
{
double theta;
m = m + j * product_1;
m = m % n;
theta = d_theta * m; /* d_theta*j*k*product_1 */
GSL_REAL(wavetable->trig[t]) = cos (theta);
GSL_IMAG(wavetable->trig[t]) = sin (theta);
t++;
}
}
}
if (t > (n / 2))
{
/* error in constructor, prevent memory leak */
free(wavetable->trig) ;
free(wavetable) ;
GSL_ERROR_VAL ("overflowed trigonometric lookup table", GSL_ESANITY, 0);
}
return wavetable;
}
void
FUNCTION(gsl_fft_halfcomplex_wavetable,free) (TYPE(gsl_fft_halfcomplex_wavetable) * wavetable)
{
/* release trigonometric lookup tables */
free (wavetable->trig);
wavetable->trig = NULL;
free (wavetable);
}
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