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/* fft/c_radix2.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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int
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FUNCTION(gsl_fft_complex,radix2_forward) (TYPE(gsl_complex_packed_array) data,
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const size_t stride, const size_t n)
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{
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gsl_fft_direction sign = gsl_fft_forward;
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int status = FUNCTION(gsl_fft_complex,radix2_transform) (data, stride, n, sign);
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return status;
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}
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int
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FUNCTION(gsl_fft_complex,radix2_backward) (TYPE(gsl_complex_packed_array) data,
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const size_t stride, const size_t n)
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{
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gsl_fft_direction sign = gsl_fft_backward;
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int status = FUNCTION(gsl_fft_complex,radix2_transform) (data, stride, n, sign);
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return status;
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}
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int
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FUNCTION(gsl_fft_complex,radix2_inverse) (TYPE(gsl_complex_packed_array) data,
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const size_t stride, const size_t n)
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{
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gsl_fft_direction sign = gsl_fft_backward;
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int status = FUNCTION(gsl_fft_complex,radix2_transform) (data, stride, n, sign);
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if (status)
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{
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return status;
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}
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/* normalize inverse fft with 1/n */
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{
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const ATOMIC norm = 1.0 / n;
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size_t i;
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for (i = 0; i < n; i++)
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{
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REAL(data,stride,i) *= norm;
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IMAG(data,stride,i) *= norm;
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}
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}
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return status;
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}
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int
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FUNCTION(gsl_fft_complex,radix2_transform) (TYPE(gsl_complex_packed_array) data,
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const size_t stride,
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const size_t n,
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const gsl_fft_direction sign)
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{
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int result ;
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size_t dual;
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size_t bit;
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size_t logn = 0;
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int status;
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if (n == 1) /* identity operation */
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{
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return 0 ;
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}
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/* make sure that n is a power of 2 */
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result = fft_binary_logn(n) ;
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if (result == -1)
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{
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GSL_ERROR ("n is not a power of 2", GSL_EINVAL);
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}
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else
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{
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logn = result ;
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}
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/* bit reverse the ordering of input data for decimation in time algorithm */
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status = FUNCTION(fft_complex,bitreverse_order) (data, stride, n, logn) ;
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/* apply fft recursion */
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dual = 1;
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for (bit = 0; bit < logn; bit++)
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{
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ATOMIC w_real = 1.0;
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ATOMIC w_imag = 0.0;
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const double theta = 2.0 * ((int) sign) * M_PI / (2.0 * (double) dual);
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const ATOMIC s = sin (theta);
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const ATOMIC t = sin (theta / 2.0);
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const ATOMIC s2 = 2.0 * t * t;
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size_t a, b;
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/* a = 0 */
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for (b = 0; b < n; b += 2 * dual)
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{
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const size_t i = b ;
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const size_t j = b + dual;
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const ATOMIC z1_real = REAL(data,stride,j) ;
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const ATOMIC z1_imag = IMAG(data,stride,j) ;
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const ATOMIC wd_real = z1_real ;
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const ATOMIC wd_imag = z1_imag ;
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REAL(data,stride,j) = REAL(data,stride,i) - wd_real;
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IMAG(data,stride,j) = IMAG(data,stride,i) - wd_imag;
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REAL(data,stride,i) += wd_real;
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IMAG(data,stride,i) += wd_imag;
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}
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/* a = 1 .. (dual-1) */
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for (a = 1; a < dual; a++)
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{
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/* trignometric recurrence for w-> exp(i theta) w */
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{
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const ATOMIC tmp_real = w_real - s * w_imag - s2 * w_real;
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const ATOMIC tmp_imag = w_imag + s * w_real - s2 * w_imag;
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w_real = tmp_real;
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w_imag = tmp_imag;
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}
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for (b = 0; b < n; b += 2 * dual)
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{
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const size_t i = b + a;
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const size_t j = b + a + dual;
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const ATOMIC z1_real = REAL(data,stride,j) ;
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const ATOMIC z1_imag = IMAG(data,stride,j) ;
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const ATOMIC wd_real = w_real * z1_real - w_imag * z1_imag;
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const ATOMIC wd_imag = w_real * z1_imag + w_imag * z1_real;
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REAL(data,stride,j) = REAL(data,stride,i) - wd_real;
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IMAG(data,stride,j) = IMAG(data,stride,i) - wd_imag;
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REAL(data,stride,i) += wd_real;
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IMAG(data,stride,i) += wd_imag;
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}
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}
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dual *= 2;
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}
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return 0;
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}
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int
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FUNCTION(gsl_fft_complex,radix2_dif_forward) (TYPE(gsl_complex_packed_array) data,
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const size_t stride,
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const size_t n)
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{
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gsl_fft_direction sign = gsl_fft_forward;
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int status = FUNCTION(gsl_fft_complex,radix2_dif_transform) (data, stride, n, sign);
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return status;
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}
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int
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FUNCTION(gsl_fft_complex,radix2_dif_backward) (TYPE(gsl_complex_packed_array) data,
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const size_t stride,
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const size_t n)
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{
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gsl_fft_direction sign = gsl_fft_backward;
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int status = FUNCTION(gsl_fft_complex,radix2_dif_transform) (data, stride, n, sign);
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return status;
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}
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int
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FUNCTION(gsl_fft_complex,radix2_dif_inverse) (TYPE(gsl_complex_packed_array) data,
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const size_t stride,
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const size_t n)
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{
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gsl_fft_direction sign = gsl_fft_backward;
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int status = FUNCTION(gsl_fft_complex,radix2_dif_transform) (data, stride, n, sign);
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if (status)
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{
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return status;
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}
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/* normalize inverse fft with 1/n */
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{
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const ATOMIC norm = 1.0 / n;
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size_t i;
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for (i = 0; i < n; i++)
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{
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REAL(data,stride,i) *= norm;
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IMAG(data,stride,i) *= norm;
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}
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}
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return status;
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}
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int
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FUNCTION(gsl_fft_complex,radix2_dif_transform) (TYPE(gsl_complex_packed_array) data,
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const size_t stride,
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const size_t n,
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const gsl_fft_direction sign)
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{
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int result ;
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size_t dual;
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size_t bit;
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size_t logn = 0;
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int status;
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if (n == 1) /* identity operation */
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{
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return 0 ;
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}
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/* make sure that n is a power of 2 */
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result = fft_binary_logn(n) ;
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if (result == -1)
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{
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GSL_ERROR ("n is not a power of 2", GSL_EINVAL);
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}
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else
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{
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logn = result ;
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}
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/* apply fft recursion */
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dual = n / 2;
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for (bit = 0; bit < logn; bit++)
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{
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ATOMIC w_real = 1.0;
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ATOMIC w_imag = 0.0;
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const double theta = 2.0 * ((int) sign) * M_PI / ((double) (2 * dual));
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const ATOMIC s = sin (theta);
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const ATOMIC t = sin (theta / 2.0);
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const ATOMIC s2 = 2.0 * t * t;
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size_t a, b;
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for (b = 0; b < dual; b++)
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{
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for (a = 0; a < n; a+= 2 * dual)
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{
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const size_t i = b + a;
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const size_t j = b + a + dual;
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const ATOMIC t1_real = REAL(data,stride,i) + REAL(data,stride,j);
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const ATOMIC t1_imag = IMAG(data,stride,i) + IMAG(data,stride,j);
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const ATOMIC t2_real = REAL(data,stride,i) - REAL(data,stride,j);
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const ATOMIC t2_imag = IMAG(data,stride,i) - IMAG(data,stride,j);
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REAL(data,stride,i) = t1_real;
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IMAG(data,stride,i) = t1_imag;
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REAL(data,stride,j) = w_real*t2_real - w_imag * t2_imag;
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67cb25 |
IMAG(data,stride,j) = w_real*t2_imag + w_imag * t2_real;
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67cb25 |
}
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|
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/* trignometric recurrence for w-> exp(i theta) w */
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{
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const ATOMIC tmp_real = w_real - s * w_imag - s2 * w_real;
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const ATOMIC tmp_imag = w_imag + s * w_real - s2 * w_imag;
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67cb25 |
w_real = tmp_real;
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w_imag = tmp_imag;
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67cb25 |
}
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}
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dual /= 2;
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67cb25 |
}
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|
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67cb25 |
/* bit reverse the ordering of output data for decimation in
|
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Packit |
67cb25 |
frequency algorithm */
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67cb25 |
|
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67cb25 |
status = FUNCTION(fft_complex,bitreverse_order)(data, stride, n, logn) ;
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|
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Packit |
67cb25 |
return 0;
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67cb25 |
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67cb25 |
}
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|
Packit |
67cb25 |
|
|
Packit |
67cb25 |
|
|
Packit |
67cb25 |
|
|
Packit |
67cb25 |
|
|
Packit |
67cb25 |
|