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c_main.c

/* fft/c_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 "c_pass.h"

int
FUNCTION(gsl_fft_complex,forward) (TYPE(gsl_complex_packed_array) data, 
                                   const size_t stride, 
                                   const size_t n,
                                   const TYPE(gsl_fft_complex_wavetable) * wavetable,
                                   TYPE(gsl_fft_complex_workspace) * work)
{
  gsl_fft_direction sign = gsl_fft_forward;
  int status = FUNCTION(gsl_fft_complex,transform) (data, stride, n, 
                                                    wavetable, work, sign);
  return status;
}

int
FUNCTION(gsl_fft_complex,backward) (TYPE(gsl_complex_packed_array) data,
                                    const size_t stride, 
                                    const size_t n,
                                    const TYPE(gsl_fft_complex_wavetable) * wavetable,
                                    TYPE(gsl_fft_complex_workspace) * work)
{
  gsl_fft_direction sign = gsl_fft_backward;
  int status = FUNCTION(gsl_fft_complex,transform) (data, stride, n, 
                                                    wavetable, work, sign);
  return status;
}

int
FUNCTION(gsl_fft_complex,inverse) (TYPE(gsl_complex_packed_array) data, 
                                   const size_t stride, 
                                   const size_t n,
                                   const TYPE(gsl_fft_complex_wavetable) * wavetable,
                                   TYPE(gsl_fft_complex_workspace) * work)
{
  gsl_fft_direction sign = gsl_fft_backward;
  int status = FUNCTION(gsl_fft_complex,transform) (data, stride, n, 
                                                    wavetable, work, sign);

  if (status)
    {
      return status;
    }

  /* normalize inverse fft with 1/n */

  {
    const ATOMIC norm = ONE / (ATOMIC)n;
    size_t i;
    for (i = 0; i < n; i++)
      {
        REAL(data,stride,i) *= norm;
        IMAG(data,stride,i) *= norm;
      }
  }
  return status;
}

int
FUNCTION(gsl_fft_complex,transform) (TYPE(gsl_complex_packed_array) data, 
                                     const size_t stride, 
                                     const size_t n,
                                     const TYPE(gsl_fft_complex_wavetable) * wavetable,
                                     TYPE(gsl_fft_complex_workspace) * work,
                                     const gsl_fft_direction sign)
{
  const size_t nf = wavetable->nf;

  size_t i;

  size_t q, product = 1;

  TYPE(gsl_complex) *twiddle1, *twiddle2, *twiddle3, *twiddle4,
    *twiddle5, *twiddle6;

  size_t state = 0;

  BASE * const scratch = work->scratch;

  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 1 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 *= factor;
      q = n / product;

      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_complex,pass_2) (in, istride, out, ostride, sign, 
                                        product, n, twiddle1);
        }
      else if (factor == 3)
        {
          twiddle1 = wavetable->twiddle[i];
          twiddle2 = twiddle1 + q;
          FUNCTION(fft_complex,pass_3) (in, istride, out, ostride, sign, 
                                        product, n, twiddle1, twiddle2);
        }
      else if (factor == 4)
        {
          twiddle1 = wavetable->twiddle[i];
          twiddle2 = twiddle1 + q;
          twiddle3 = twiddle2 + q;
          FUNCTION(fft_complex,pass_4) (in, istride, out, ostride, sign, 
                                        product, n, twiddle1, twiddle2, 
                                        twiddle3);
        }
      else if (factor == 5)
        {
          twiddle1 = wavetable->twiddle[i];
          twiddle2 = twiddle1 + q;
          twiddle3 = twiddle2 + q;
          twiddle4 = twiddle3 + q;
          FUNCTION(fft_complex,pass_5) (in, istride, out, ostride, sign, 
                                        product, n, twiddle1, twiddle2, 
                                        twiddle3, twiddle4);
        }
      else if (factor == 6)
        {
          twiddle1 = wavetable->twiddle[i];
          twiddle2 = twiddle1 + q;
          twiddle3 = twiddle2 + q;
          twiddle4 = twiddle3 + q;
          twiddle5 = twiddle4 + q;
          FUNCTION(fft_complex,pass_6) (in, istride, out, ostride, sign, 
                                        product, n, twiddle1, twiddle2, 
                                        twiddle3, twiddle4, twiddle5);
        }
      else if (factor == 7)
        {
          twiddle1 = wavetable->twiddle[i];
          twiddle2 = twiddle1 + q;
          twiddle3 = twiddle2 + q;
          twiddle4 = twiddle3 + q;
          twiddle5 = twiddle4 + q;
          twiddle6 = twiddle5 + q;
          FUNCTION(fft_complex,pass_7) (in, istride, out, ostride, sign, 
                                        product, n, twiddle1, twiddle2, 
                                        twiddle3, twiddle4, twiddle5, 
                                        twiddle6);
        }
      else
        {
          twiddle1 = wavetable->twiddle[i];
          FUNCTION(fft_complex,pass_n) (in, istride, out, ostride, sign, 
                                        factor, product, n, twiddle1);
        }
    }

  if (state == 1)               /* copy results back from scratch to data */
    {
      for (i = 0; i < n; i++)
        {
          REAL(data,stride,i) = REAL(scratch,1,i) ;
          IMAG(data,stride,i) = IMAG(scratch,1,i) ;
        }
    }

  return 0;

}

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