123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146 |
- /* fft/real_main.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 <stdlib.h>
- #include <math.h>
- #include "gsl_errno.h"
- #include "gsl_complex.h"
- #include "gsl_fft_real.h"
- #include "gsl_fft__real_pass.h"
- int
- FUNCTION(gsl_fft_real,transform) (BASE data[], const size_t stride, const size_t n,
- const TYPE(gsl_fft_real_wavetable) * wavetable,
- TYPE(gsl_fft_real_workspace) * work)
- {
- const size_t nf = wavetable->nf;
- size_t i;
- size_t q, product = 1;
- size_t tskip;
- size_t product_1;
- BASE *const scratch = work->scratch;
- TYPE(gsl_complex) *twiddle1, *twiddle2, *twiddle3, *twiddle4;
- size_t state = 0;
- BASE *in = data;
- size_t istride = stride ;
- BASE *out = scratch;
- size_t ostride = 1 ;
-
- if (n == 0)
- {
- GSL_ERROR ("length n must be positive integer", GSL_EDOM);
- }
- if (n == 1)
- { /* FFT of one data point is the identity */
- return 0;
- }
- if (n != wavetable->n)
- {
- GSL_ERROR ("wavetable does not match length of data", GSL_EINVAL);
- }
- if (n != work->n)
- {
- GSL_ERROR ("workspace does not match length of data", GSL_EINVAL);
- }
- for (i = 0; i < nf; i++)
- {
- const size_t factor = wavetable->factor[i];
- product_1 = product;
- product *= factor;
- q = n / product;
- tskip = (product_1 + 1) / 2 - 1;
- if (state == 0)
- {
- in = data;
- istride = stride;
- out = scratch;
- ostride = 1;
- state = 1;
- }
- else
- {
- in = scratch;
- istride = 1;
- out = data;
- ostride = stride;
- state = 0;
- }
- if (factor == 2)
- {
- twiddle1 = wavetable->twiddle[i];
- FUNCTION(fft_real,pass_2) (in, istride, out, ostride, product, n, twiddle1);
- }
- else if (factor == 3)
- {
- twiddle1 = wavetable->twiddle[i];
- twiddle2 = twiddle1 + tskip;
- FUNCTION(fft_real,pass_3) (in, istride, out, ostride, product, n, twiddle1,
- twiddle2);
- }
- else if (factor == 4)
- {
- twiddle1 = wavetable->twiddle[i];
- twiddle2 = twiddle1 + tskip;
- twiddle3 = twiddle2 + tskip;
- FUNCTION(fft_real,pass_4) (in, istride, out, ostride, product, n, twiddle1,
- twiddle2, twiddle3);
- }
- else if (factor == 5)
- {
- twiddle1 = wavetable->twiddle[i];
- twiddle2 = twiddle1 + tskip;
- twiddle3 = twiddle2 + tskip;
- twiddle4 = twiddle3 + tskip;
- FUNCTION(fft_real,pass_5) (in, istride, out, ostride, product, n, twiddle1,
- twiddle2, twiddle3, twiddle4);
- }
- else
- {
- twiddle1 = wavetable->twiddle[i];
- FUNCTION(fft_real,pass_n) (in, istride, out, ostride, factor, product, n,
- twiddle1);
- }
- }
- if (state == 1) /* copy results back from scratch to data */
- {
- for (i = 0; i < n; i++)
- {
- data[stride*i] = scratch[i] ;
- }
- }
- return 0;
- }
|