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/* fft/real_pass_n.c
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*
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* Copyright (C) 1996, 1997, 1998, 1999, 2000, 2007 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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static void
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FUNCTION(fft_real,pass_n) (const BASE in[],
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const size_t istride,
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BASE out[],
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const size_t ostride,
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const size_t factor,
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const size_t product,
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const size_t n,
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const TYPE(gsl_complex) twiddle[])
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{
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size_t k, k1;
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const size_t m = n / factor;
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const size_t q = n / product;
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const size_t product_1 = product / factor;
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size_t e1, e2;
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const double d_theta = 2.0 * M_PI / ((double) factor);
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const ATOMIC cos_d_theta = cos (d_theta);
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const ATOMIC sin_d_theta = sin (d_theta);
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for (k1 = 0; k1 < q; k1++)
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{
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/* compute x = W(factor) z, for z real */
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ATOMIC dw_real = 1.0, dw_imag = 0.0;
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for (e1 = 0; e1 <= factor - e1; e1++)
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{
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ATOMIC sum_real = 0.0;
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ATOMIC sum_imag = 0.0;
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ATOMIC w_real = 1.0, w_imag = 0.0;
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if (e1 > 0)
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{
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ATOMIC tmp_real = dw_real * cos_d_theta + dw_imag * sin_d_theta;
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ATOMIC tmp_imag = -dw_real * sin_d_theta + dw_imag * cos_d_theta;
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dw_real = tmp_real;
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dw_imag = tmp_imag;
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}
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for (e2 = 0; e2 < factor; e2++)
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{
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ATOMIC z_real = VECTOR(in,istride,k1 * product_1 + e2 * m);
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if (e2 > 0)
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{
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ATOMIC tmp_real = dw_real * w_real - dw_imag * w_imag;
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ATOMIC tmp_imag = dw_real * w_imag + dw_imag * w_real;
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w_real = tmp_real;
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w_imag = tmp_imag;
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}
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sum_real += w_real * z_real;
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sum_imag += w_imag * z_real;
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}
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if (e1 == 0)
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{
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const size_t to0 = product * k1;
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VECTOR(out,ostride,to0) = sum_real;
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}
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else if (e1 < factor - e1)
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{
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const size_t to0 = k1 * product + 2 * e1 * product_1 - 1;
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VECTOR(out,ostride,to0) = sum_real;
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VECTOR(out,ostride,to0 + 1) = sum_imag;
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}
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else if (e1 == factor - e1)
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{
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const size_t to0 = k1 * product + 2 * e1 * product_1 - 1;
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VECTOR(out,ostride,to0) = sum_real;
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}
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}
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}
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if (product_1 == 1)
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return;
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for (k = 1; k < (product_1 + 1) / 2; k++)
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{
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for (k1 = 0; k1 < q; k1++)
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{
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ATOMIC dw_real = 1.0, dw_imag = 0.0;
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for (e1 = 0; e1 < factor; e1++)
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{
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ATOMIC sum_real = 0.0, sum_imag = 0.0;
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ATOMIC w_real = 1.0, w_imag = 0.0;
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if (e1 > 0)
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{
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const ATOMIC tmp_real = dw_real * cos_d_theta + dw_imag * sin_d_theta;
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const ATOMIC tmp_imag = -dw_real * sin_d_theta + dw_imag * cos_d_theta;
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dw_real = tmp_real;
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dw_imag = tmp_imag;
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}
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for (e2 = 0; e2 < factor; e2++)
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{
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int tskip = (product_1 + 1) / 2 - 1;
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const size_t from0 = k1 * product_1 + 2 * k + e2 * m - 1;
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ATOMIC tw_real, tw_imag;
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ATOMIC z_real, z_imag;
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if (e2 == 0)
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{
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tw_real = 1.0;
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tw_imag = 0.0;
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}
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else
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{
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const size_t t_index = (k - 1) + (e2 - 1) * tskip;
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tw_real = GSL_REAL(twiddle[t_index]);
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tw_imag = -GSL_IMAG(twiddle[t_index]);
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}
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{
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const ATOMIC f0_real = VECTOR(in,istride,from0);
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const ATOMIC f0_imag = VECTOR(in,istride,from0 + 1);
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z_real = tw_real * f0_real - tw_imag * f0_imag;
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z_imag = tw_real * f0_imag + tw_imag * f0_real;
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}
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if (e2 > 0)
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{
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const ATOMIC tmp_real = dw_real * w_real - dw_imag * w_imag;
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const ATOMIC tmp_imag = dw_real * w_imag + dw_imag * w_real;
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w_real = tmp_real;
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w_imag = tmp_imag;
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}
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sum_real += w_real * z_real - w_imag * z_imag;
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sum_imag += w_real * z_imag + w_imag * z_real;
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}
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if (e1 < factor - e1)
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{
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const size_t to0 = k1 * product - 1 + 2 * e1 * product_1 + 2 * k;
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VECTOR(out,ostride,to0) = sum_real;
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VECTOR(out,ostride,to0 + 1) = sum_imag;
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}
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else
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{
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const size_t to0 = k1 * product - 1 + 2 * (factor - e1) * product_1 - 2 * k;
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VECTOR(out,ostride,to0) = sum_real;
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VECTOR(out,ostride,to0 + 1) = -sum_imag;
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}
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}
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}
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}
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if (product_1 % 2 == 1)
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return;
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{
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double tw_arg = M_PI / ((double) factor);
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ATOMIC cos_tw_arg = cos (tw_arg);
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ATOMIC sin_tw_arg = -sin (tw_arg);
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for (k1 = 0; k1 < q; k1++)
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{
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ATOMIC dw_real = 1.0, dw_imag = 0.0;
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for (e1 = 0; e1 < factor; e1++)
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{
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ATOMIC z_real, z_imag;
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ATOMIC sum_real = 0.0;
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ATOMIC sum_imag = 0.0;
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ATOMIC w_real = 1.0, w_imag = 0.0;
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ATOMIC tw_real = 1.0, tw_imag = 0.0;
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if (e1 > 0)
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{
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ATOMIC t_real = dw_real * cos_d_theta + dw_imag * sin_d_theta;
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ATOMIC t_imag = -dw_real * sin_d_theta + dw_imag * cos_d_theta;
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dw_real = t_real;
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dw_imag = t_imag;
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}
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for (e2 = 0; e2 < factor; e2++)
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{
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if (e2 > 0)
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{
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ATOMIC tmp_real = tw_real * cos_tw_arg - tw_imag * sin_tw_arg;
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ATOMIC tmp_imag = tw_real * sin_tw_arg + tw_imag * cos_tw_arg;
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tw_real = tmp_real;
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tw_imag = tmp_imag;
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}
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if (e2 > 0)
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{
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ATOMIC tmp_real = dw_real * w_real - dw_imag * w_imag;
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ATOMIC tmp_imag = dw_real * w_imag + dw_imag * w_real;
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w_real = tmp_real;
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w_imag = tmp_imag;
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}
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{
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const size_t from0 = k1 * product_1 + 2 * k + e2 * m - 1;
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const ATOMIC f0_real = VECTOR(in,istride,from0);
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z_real = tw_real * f0_real;
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z_imag = tw_imag * f0_real;
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}
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sum_real += w_real * z_real - w_imag * z_imag;
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sum_imag += w_real * z_imag + w_imag * z_real;
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}
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if (e1 + 1 < factor - e1)
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{
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const size_t to0 = k1 * product - 1 + 2 * e1 * product_1 + 2 * k;
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VECTOR(out,ostride,to0) = sum_real;
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VECTOR(out,ostride,to0 + 1) = sum_imag;
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}
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else if (e1 + 1 == factor - e1)
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{
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const size_t to0 = k1 * product - 1 + 2 * e1 * product_1 + 2 * k;
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VECTOR(out,ostride,to0) = sum_real;
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}
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else
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{
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const size_t to0 = k1 * product - 1 + 2 * (factor - e1) * product_1 - 2 * k;
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VECTOR(out,ostride,to0) = sum_real;
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VECTOR(out,ostride,to0 + 1) = -sum_imag;
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}
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}
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}
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}
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return;
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}
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