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/* fft/c_pass_n.c
*
* Copyright (C) 1996, 1997, 1998, 1999, 2000, 2007 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 3 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.
*/
static int
FUNCTION(fft_complex,pass_n) (BASE in[],
const size_t istride,
BASE out[],
const size_t ostride,
const gsl_fft_direction sign,
const size_t factor,
const size_t product,
const size_t n,
const TYPE(gsl_complex) twiddle[])
{
size_t i = 0, j = 0;
size_t k, k1;
const size_t m = n / factor;
const size_t q = n / product;
const size_t p_1 = product / factor;
const size_t jump = (factor - 1) * p_1;
size_t e, e1;
for (i = 0; i < m; i++)
{
REAL(out,ostride,i) = REAL(in,istride,i);
IMAG(out,ostride,i) = IMAG(in,istride,i);
}
for (e = 1; e < (factor - 1) / 2 + 1; e++)
{
for (i = 0; i < m; i++)
{
const size_t idx = i + e * m;
const size_t idxc = i + (factor - e) * m;
REAL(out,ostride,idx) = REAL(in,istride,idx) + REAL(in,istride,idxc);
IMAG(out,ostride,idx) = IMAG(in,istride,idx) + IMAG(in,istride,idxc);
REAL(out,ostride,idxc) = REAL(in,istride,idx) - REAL(in,istride,idxc);
IMAG(out,ostride,idxc) = IMAG(in,istride,idx) - IMAG(in,istride,idxc);
}
}
/* e = 0 */
for (i=0 ; i<m; i++)
{
REAL(in,istride,i) = REAL(out,ostride,i);
IMAG(in,istride,i) = IMAG(out,ostride,i);
}
for (e1 = 1; e1 < (factor - 1) / 2 + 1; e1++)
{
for (i = 0; i < m; i++)
{
REAL(in,istride,i) += REAL(out,ostride,i + e1*m) ;
IMAG(in,istride,i) += IMAG(out,ostride,i + e1*m) ;
}
}
for (e = 1; e < (factor-1)/2 + 1; e++)
{
size_t idx = e*q ;
const size_t idx_step = e * q ;
ATOMIC w_real, w_imag ;
const size_t em = e * m ;
const size_t ecm = (factor - e) * m ;
for (i = 0; i < m; i++)
{
REAL(in,istride,i+em) = REAL(out,ostride,i) ;
IMAG(in,istride,i+em) = IMAG(out,ostride,i) ;
REAL(in,istride,i+ecm) = REAL(out,ostride,i) ;
IMAG(in,istride,i+ecm) = IMAG(out,ostride,i) ;
}
for (e1 = 1; e1 < (factor - 1) / 2 + 1; e1++)
{
if (idx == 0) {
w_real = 1 ;
w_imag = 0 ;
} else {
if (sign == gsl_fft_forward) {
w_real = GSL_REAL(twiddle[idx - 1]) ;
w_imag = GSL_IMAG(twiddle[idx - 1]) ;
} else {
w_real = GSL_REAL(twiddle[idx - 1]) ;
w_imag = -GSL_IMAG(twiddle[idx - 1]) ;
}
}
for (i = 0; i < m; i++)
{
const ATOMIC xp_real = REAL(out,ostride,i + e1 * m);
const ATOMIC xp_imag = IMAG(out,ostride,i + e1 * m);
const ATOMIC xm_real = REAL(out,ostride,i + (factor - e1) *m);
const ATOMIC xm_imag = IMAG(out,ostride,i + (factor - e1) *m);
const ATOMIC ap = w_real * xp_real ;
const ATOMIC am = w_imag * xm_imag ;
ATOMIC sum_real = ap - am;
ATOMIC sumc_real = ap + am;
const ATOMIC bp = w_real * xp_imag ;
const ATOMIC bm = w_imag * xm_real ;
ATOMIC sum_imag = bp + bm;
ATOMIC sumc_imag = bp - bm;
REAL(in,istride,i + em) += sum_real;
IMAG(in,istride,i + em) += sum_imag;
REAL(in,istride,i + ecm) += sumc_real;
IMAG(in,istride,i + ecm) += sumc_imag;
}
idx += idx_step ;
idx %= factor * q ;
}
}
i = 0;
j = 0;
/* k = 0 */
for (k1 = 0; k1 < p_1; k1++)
{
REAL(out,ostride,k1) = REAL(in,istride,k1);
IMAG(out,ostride,k1) = IMAG(in,istride,k1);
}
for (e1 = 1; e1 < factor; e1++)
{
for (k1 = 0; k1 < p_1; k1++)
{
REAL(out,ostride,k1 + e1 * p_1) = REAL(in,istride,k1 + e1 * m) ;
IMAG(out,ostride,k1 + e1 * p_1) = IMAG(in,istride,k1 + e1 * m) ;
}
}
i = p_1 ;
j = product ;
for (k = 1; k < q; k++)
{
for (k1 = 0; k1 < p_1; k1++)
{
REAL(out,ostride,j) = REAL(in,istride,i);
IMAG(out,ostride,j) = IMAG(in,istride,i);
i++;
j++;
}
j += jump;
}
i = p_1 ;
j = product ;
for (k = 1; k < q; k++)
{
for (k1 = 0; k1 < p_1; k1++)
{
for (e1 = 1; e1 < factor; e1++)
{
ATOMIC x_real = REAL(in, istride,i + e1 * m);
ATOMIC x_imag = IMAG(in, istride,i + e1 * m);
ATOMIC w_real, w_imag ;
if (sign == gsl_fft_forward) {
w_real = GSL_REAL(twiddle[(e1-1)*q + k-1]) ;
w_imag = GSL_IMAG(twiddle[(e1-1)*q + k-1]) ;
} else {
w_real = GSL_REAL(twiddle[(e1-1)*q + k-1]) ;
w_imag = -GSL_IMAG(twiddle[(e1-1)*q + k-1]) ;
}
REAL(out,ostride,j + e1 * p_1) = w_real * x_real - w_imag * x_imag;
IMAG(out,ostride,j + e1 * p_1) = w_real * x_imag + w_imag * x_real;
}
i++;
j++;
}
j += jump;
}
return 0;
}
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