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- /* fft/bitreverse.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.
- */
- #include "gsl__config.h"
- #include "gsl_fft.h"
- #include "gsl_fft__complex_internal.h"
- #include "gsl_fft__bitreverse.h"
- static int
- FUNCTION(fft_complex,bitreverse_order) (BASE data[],
- const size_t stride,
- const size_t n,
- size_t logn)
- {
- /* This is the Goldrader bit-reversal algorithm */
- size_t i;
- size_t j = 0;
- logn = 0 ; /* not needed for this algorithm */
- for (i = 0; i < n - 1; i++)
- {
- size_t k = n / 2 ;
- if (i < j)
- {
- const BASE tmp_real = REAL(data,stride,i);
- const BASE tmp_imag = IMAG(data,stride,i);
- REAL(data,stride,i) = REAL(data,stride,j);
- IMAG(data,stride,i) = IMAG(data,stride,j);
- REAL(data,stride,j) = tmp_real;
- IMAG(data,stride,j) = tmp_imag;
- }
- while (k <= j)
- {
- j = j - k ;
- k = k / 2 ;
- }
- j += k ;
- }
- return 0;
- }
- static int
- FUNCTION(fft_real,bitreverse_order) (BASE data[],
- const size_t stride,
- const size_t n,
- size_t logn)
- {
- /* This is the Goldrader bit-reversal algorithm */
- size_t i;
- size_t j = 0;
- logn = 0 ; /* not needed for this algorithm */
- for (i = 0; i < n - 1; i++)
- {
- size_t k = n / 2 ;
- if (i < j)
- {
- const BASE tmp = VECTOR(data,stride,i);
- VECTOR(data,stride,i) = VECTOR(data,stride,j);
- VECTOR(data,stride,j) = tmp;
- }
- while (k <= j)
- {
- j = j - k ;
- k = k / 2 ;
- }
- j += k ;
- }
- return 0;
- }
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