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/* 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 <config.h>
#include <stdlib.h>
#include <math.h>
#include <gsl/gsl_errno.h>
#include <gsl/gsl_complex.h>
#include <gsl/gsl_fft_real.h>
#include "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;
}
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