/* rng/default.c

 * 

 * Copyright (C) 1996, 1997, 1998, 1999, 2000, 2007 James Theiler, 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 <stdio.h>

#include <string.h>

#include <gsl/gsl_rng.h>

#include <gsl/gsl_errno.h>

/* The initial defaults are defined in the file mt.c, so we can get

   access to the static parts of the default generator. */

const gsl_rng_type *

gsl_rng_env_setup (void)

{

  unsigned long int seed = 0;

  const char *p = getenv ("GSL_RNG_TYPE");

  if (p)

    {

      const gsl_rng_type **t, **t0 = gsl_rng_types_setup ();

      gsl_rng_default = 0;

      /* check GSL_RNG_TYPE against the names of all the generators */

      for (t = t0; *t != 0; t++)

        {

          if (strcmp (p, (*t)->name) == 0)

            {

              gsl_rng_default = *t;

              break;

            }

        }

      if (gsl_rng_default == 0)

        {

          int i = 0;

          fprintf (stderr, "GSL_RNG_TYPE=%s not recognized\n", p);

          fprintf (stderr, "Valid generator types are:\n");

          for (t = t0; *t != 0; t++)

            {

              fprintf (stderr, " %18s", (*t)->name);

              if ((++i) % 4 == 0)

                {

                  fputc ('\n', stderr);

                }

            }

          fputc ('\n', stderr);

          GSL_ERROR_VAL ("unknown generator", GSL_EINVAL, 0);

        }

      fprintf (stderr, "GSL_RNG_TYPE=%s\n", gsl_rng_default->name);

    }

  else

    {

      gsl_rng_default = gsl_rng_mt19937;

    }

  p = getenv ("GSL_RNG_SEED");

  if (p)

    {

      seed = strtoul (p, 0, 0);

      fprintf (stderr, "GSL_RNG_SEED=%lu\n", seed);

    };

  gsl_rng_default_seed = seed;

  return gsl_rng_default;

}