/* roots/convergence.c

 * 

 * Copyright (C) 1996, 1997, 1998, 1999, 2000, 2007 Reid Priedhorsky, 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 <gsl/gsl_math.h>

#include <gsl/gsl_errno.h>

#include <gsl/gsl_roots.h>

int

gsl_root_test_interval (double x_lower, double x_upper, double epsabs, double epsrel)

{

  const double abs_lower = fabs(x_lower) ;

  const double abs_upper = fabs(x_upper) ;

  double min_abs, tolerance;

  if (epsrel < 0.0)

    GSL_ERROR ("relative tolerance is negative", GSL_EBADTOL);

  if (epsabs < 0.0)

    GSL_ERROR ("absolute tolerance is negative", GSL_EBADTOL);

  if (x_lower > x_upper)

    GSL_ERROR ("lower bound larger than upper bound", GSL_EINVAL);

  if ((x_lower > 0.0 && x_upper > 0.0) || (x_lower < 0.0 && x_upper < 0.0)) 

    {

      min_abs = GSL_MIN_DBL(abs_lower, abs_upper) ;

    }

  else

    {

      min_abs = 0;

    }

  tolerance = epsabs + epsrel * min_abs  ;

  if (fabs(x_upper - x_lower) < tolerance)

    return GSL_SUCCESS;

  return GSL_CONTINUE ;

}

int

gsl_root_test_delta (double x1, double x0, double epsabs, double epsrel)

{

  const double tolerance = epsabs + epsrel * fabs(x1)  ;

  if (epsrel < 0.0)

    GSL_ERROR ("relative tolerance is negative", GSL_EBADTOL);

  if (epsabs < 0.0)

    GSL_ERROR ("absolute tolerance is negative", GSL_EBADTOL);

  if (fabs(x1 - x0) < tolerance || x1 == x0)

    return GSL_SUCCESS;

  return GSL_CONTINUE ;

}

int

gsl_root_test_residual (double f, double epsabs)

{

  if (epsabs < 0.0)

    GSL_ERROR ("absolute tolerance is negative", GSL_EBADTOL);

  if (fabs(f) < epsabs)

    return GSL_SUCCESS;

  return GSL_CONTINUE ;

}