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/* fft/hc_init.c
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*
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* Copyright (C) 1996, 1997, 1998, 1999, 2000, 2007, 2009 Brian Gough
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 3 of the License, or (at
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* your option) any later version.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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*/
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TYPE(gsl_fft_halfcomplex_wavetable) *
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FUNCTION(gsl_fft_halfcomplex_wavetable,alloc) (size_t n)
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{
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int status;
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size_t i;
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size_t n_factors;
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size_t t, product, product_1, q;
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double d_theta;
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TYPE(gsl_fft_halfcomplex_wavetable) * wavetable ;
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if (n == 0)
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{
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GSL_ERROR_VAL ("length n must be positive integer", GSL_EDOM, 0);
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}
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wavetable = (TYPE(gsl_fft_halfcomplex_wavetable) *)
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malloc(sizeof(TYPE(gsl_fft_halfcomplex_wavetable)));
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if (wavetable == NULL)
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{
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GSL_ERROR_VAL ("failed to allocate struct", GSL_ENOMEM, 0);
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}
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wavetable->trig = (TYPE(gsl_complex) *) malloc (n * sizeof (TYPE(gsl_complex)));
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if (wavetable->trig == NULL)
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{
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/* error in constructor, prevent memory leak */
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free(wavetable) ;
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GSL_ERROR_VAL ("failed to allocate trigonometric lookup table",
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GSL_ENOMEM, 0);
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}
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wavetable->n = n ;
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status = fft_halfcomplex_factorize (n, &n_factors, wavetable->factor);
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if (status)
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{
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/* error in constructor, prevent memory leak */
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free(wavetable->trig) ;
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free(wavetable) ;
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GSL_ERROR_VAL ("factorization failed", GSL_EFACTOR, 0);
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}
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wavetable->nf = n_factors;
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d_theta = 2.0 * M_PI / ((double) n);
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t = 0;
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product = 1;
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for (i = 0; i < n_factors; i++)
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{
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size_t j;
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const size_t factor = wavetable->factor[i];
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wavetable->twiddle[i] = wavetable->trig + t;
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product_1 = product; /* product_1 = p_(i-1) */
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product *= factor;
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q = n / product;
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for (j = 1; j < factor; j++)
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{
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size_t k;
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size_t m = 0;
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for (k = 1; k < (q + 1) / 2; k++)
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{
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double theta;
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m = m + j * product_1;
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m = m % n;
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theta = d_theta * m; /* d_theta*j*k*product_1 */
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GSL_REAL(wavetable->trig[t]) = cos (theta);
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GSL_IMAG(wavetable->trig[t]) = sin (theta);
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t++;
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}
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}
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}
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if (t > (n / 2))
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{
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/* error in constructor, prevent memory leak */
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free(wavetable->trig) ;
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free(wavetable) ;
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GSL_ERROR_VAL ("overflowed trigonometric lookup table", GSL_ESANITY, 0);
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}
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return wavetable;
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}
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void
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FUNCTION(gsl_fft_halfcomplex_wavetable,free) (TYPE(gsl_fft_halfcomplex_wavetable) * wavetable)
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{
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RETURN_IF_NULL (wavetable);
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/* release trigonometric lookup tables */
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free (wavetable->trig);
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wavetable->trig = NULL;
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free (wavetable);
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}
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