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