/* fft/real_init.c

 * 

 * Copyright (C) 1996, 1997, 1998, 1999, 2000, 2007, 2009 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.

 */

TYPE(gsl_fft_real_wavetable) *

FUNCTION(gsl_fft_real_wavetable,alloc) (size_t n)

{

  int status;

  size_t i;

  size_t n_factors;

  size_t t, product, product_1, q;

  double d_theta;

  TYPE(gsl_fft_real_wavetable) * wavetable;

  if (n == 0)

    {

      GSL_ERROR_VAL ("length n must be positive integer", GSL_EDOM, 0);

    }

  wavetable = (TYPE(gsl_fft_real_wavetable) *) 

    malloc(sizeof(TYPE(gsl_fft_real_wavetable)));

  if (wavetable == NULL)

    {

      GSL_ERROR_VAL ("failed to allocate struct", GSL_ENOMEM, 0);

    }

  if (n == 1) 

    {

      wavetable->trig = 0;

    }

  else

    {

      wavetable->trig = (TYPE(gsl_complex) *) 

        malloc ((n / 2) * sizeof (TYPE(gsl_complex)));

      if (wavetable->trig == NULL)

        {

          /* error in constructor, prevent memory leak */

          free(wavetable) ; 

          GSL_ERROR_VAL ("failed to allocate trigonometric lookup table", 

                            GSL_ENOMEM, 0);

        }

    }

  wavetable->n = n;

  status = fft_real_factorize (n, &n_factors, wavetable->factor);

  if (status)

    {

      /* error in constructor, prevent memory leak */

      free(wavetable->trig);

      free(wavetable) ; 

      GSL_ERROR_VAL ("factorization failed", GSL_EFACTOR, 0);

    }

  wavetable->nf = n_factors;

  d_theta = 2.0 * M_PI / ((double) n);

  t = 0;

  product = 1;

  for (i = 0; i < wavetable->nf; i++)

    {

      size_t j;

      const size_t factor = wavetable->factor[i];

      wavetable->twiddle[i] = wavetable->trig + t;

      product_1 = product;      /* product_1 = p_(i-1) */

      product *= factor;

      q = n / product;

      for (j = 1; j < factor; j++)

        {

          size_t k;

          size_t m = 0;

          for (k = 1; k < (product_1 + 1) / 2; k++)

            {

              double theta;

              m = m + j * q;

              m = m % n;

              theta = d_theta * m;      /*  d_theta*j*k*q */

              GSL_REAL(wavetable->trig[t]) = cos (theta);

              GSL_IMAG(wavetable->trig[t]) = sin (theta);

              t++;

            }

        }

    }

  if (t > (n / 2))

    {

      /* error in constructor, prevent memory leak */

      free(wavetable->trig);

      free(wavetable) ; 

      GSL_ERROR_VAL ("overflowed trigonometric lookup table", 

                        GSL_ESANITY, 0);

    }

  return wavetable;

}

TYPE(gsl_fft_real_workspace) *

FUNCTION(gsl_fft_real_workspace,alloc) (size_t n)

{

  TYPE(gsl_fft_real_workspace) * workspace;

  if (n == 0)

    {

      GSL_ERROR_VAL ("length n must be positive integer", GSL_EDOM, 0);

    }

  workspace = (TYPE(gsl_fft_real_workspace) *) 

    malloc(sizeof(TYPE(gsl_fft_real_workspace)));

  if (workspace == NULL)

    {

      GSL_ERROR_VAL ("failed to allocate struct", GSL_ENOMEM, 0);

    }

  workspace->n = n;

  workspace->scratch = (BASE *) malloc (n * sizeof (BASE));

  if (workspace->scratch == NULL)

    {

      /* error in constructor, prevent memory leak */

      free(workspace) ; 

      GSL_ERROR_VAL ("failed to allocate scratch space", GSL_ENOMEM, 0);

    }

  return workspace;

}

void

FUNCTION(gsl_fft_real_wavetable,free) (TYPE(gsl_fft_real_wavetable) * wavetable)

{

  RETURN_IF_NULL (wavetable);

  /* release trigonometric lookup tables */

  free (wavetable->trig);

  wavetable->trig = NULL;

  free (wavetable) ;

}

void

FUNCTION(gsl_fft_real_workspace,free) (TYPE(gsl_fft_real_workspace) * workspace)

{

  RETURN_IF_NULL (workspace);

  /* release scratch space */

  free (workspace->scratch);

  workspace->scratch = NULL;

  free (workspace) ;

}